Functional mechanisms of drought tolerance in subtropical maize (Zea mays L.) identified using genome-wide association mapping.

PubMed

Thirunavukkarasu, Nepolean; Hossain, Firoz; Arora, Kanika; Sharma, Rinku; Shiriga, Kaliyugam; Mittal, Swati; Mohan, Sweta; Namratha, Pottekatt Mohanlal; Dogga, Sreelatha; Rani, Tikka Shobha; Katragadda, Sumalini; Rathore, Abhishek; Shah, Trushar; Mohapatra, Trilochan; Gupta, Hari Shankar

2014-12-24

Earlier studies were focused on the genetics of temperate and tropical maize under drought. We identified genetic loci and their association with functional mechanisms in 240 accessions of subtropical maize using a high-density marker set under water stress. Out of 61 significant SNPs (11 were false-discovery-rate-corrected associations), identified across agronomic traits, models, and locations by subjecting the accessions to water stress at flowering stage, 48% were associated with drought-tolerant genes. Maize gene models revealed that SNPs mapped for agronomic traits were in fact associated with number of functional traits as follows: stomatal closure, 28; flowering, 15; root development, 5; detoxification, 4; and reduced water potential, 2. Interactions of these SNPS through the functional traits could lead to drought tolerance. The SNPs associated with ABA-dependent signalling pathways played a major role in the plant's response to stress by regulating a series of functions including flowering, root development, auxin metabolism, guard cell functions, and scavenging reactive oxygen species (ROS). ABA signalling genes regulate flowering through epigenetic changes in stress-responsive genes. ROS generated by ABA signalling are reduced by the interplay between ethylene, ABA, and detoxification signalling transductions. Integration of ABA-signalling genes with auxin-inducible genes regulates root development which in turn, maintains the water balance by regulating electrochemical gradient in plant. Several genes are directly or indirectly involved in the functioning of agronomic traits related to water stress. Genes involved in these crucial biological functions interacted significantly in order to maintain the primary as well as exclusive functions related to coping with water stress. SNPs associated with drought-tolerant genes involved in strategic biological functions will be useful to understand the mechanisms of drought tolerance in subtropical maize.

Ethylene Responses in Rice Roots and Coleoptiles Are Differentially Regulated by a Carotenoid Isomerase-Mediated Abscisic Acid Pathway[OPEN

PubMed Central

Yin, Cui-Cui; Ma, Biao; Collinge, Derek Phillip; Pogson, Barry James; He, Si-Jie; Xiong, Qing; Duan, Kai-Xuan; Chen, Hui; Yang, Chao; Lu, Xiang; Wang, Yi-Qin; Zhang, Wan-Ke; Chu, Cheng-Cai; Sun, Xiao-Hong; Fang, Shuang; Chu, Jin-Fang; Lu, Tie-Gang; Chen, Shou-Yi; Zhang, Jin-Song

2015-01-01

Ethylene and abscisic acid (ABA) act synergistically or antagonistically to regulate plant growth and development. ABA is derived from the carotenoid biosynthesis pathway. Here, we analyzed the interplay among ethylene, carotenoid biogenesis, and ABA in rice (Oryza sativa) using the rice ethylene response mutant mhz5, which displays a reduced ethylene response in roots but an enhanced ethylene response in coleoptiles. We found that MHZ5 encodes a carotenoid isomerase and that the mutation in mhz5 blocks carotenoid biosynthesis, reduces ABA accumulation, and promotes ethylene production in etiolated seedlings. ABA can largely rescue the ethylene response of the mhz5 mutant. Ethylene induces MHZ5 expression, the production of neoxanthin, an ABA biosynthesis precursor, and ABA accumulation in roots. MHZ5 overexpression results in enhanced ethylene sensitivity in roots and reduced ethylene sensitivity in coleoptiles. Mutation or overexpression of MHZ5 also alters the expression of ethylene-responsive genes. Genetic studies revealed that the MHZ5-mediated ABA pathway acts downstream of ethylene signaling to inhibit root growth. The MHZ5-mediated ABA pathway likely acts upstream but negatively regulates ethylene signaling to control coleoptile growth. Our study reveals novel interactions among ethylene, carotenogenesis, and ABA and provides insight into improvements in agronomic traits and adaptive growth through the manipulation of these pathways in rice. PMID:25841037

Release of GTP Exchange Factor Mediated Down-Regulation of Abscisic Acid Signal Transduction through ABA-Induced Rapid Degradation of RopGEFs

PubMed Central

Waadt, Rainer; Schroeder, Julian I.

2016-01-01

The phytohormone abscisic acid (ABA) is critical to plant development and stress responses. Abiotic stress triggers an ABA signal transduction cascade, which is comprised of the core components PYL/RCAR ABA receptors, PP2C-type protein phosphatases, and protein kinases. Small GTPases of the ROP/RAC family act as negative regulators of ABA signal transduction. However, the mechanisms by which ABA controls the behavior of ROP/RACs have remained unclear. Here, we show that an Arabidopsis guanine nucleotide exchange factor protein RopGEF1 is rapidly sequestered to intracellular particles in response to ABA. GFP-RopGEF1 is sequestered via the endosome-prevacuolar compartment pathway and is degraded. RopGEF1 directly interacts with several clade A PP2C protein phosphatases, including ABI1. Interestingly, RopGEF1 undergoes constitutive degradation in pp2c quadruple abi1/abi2/hab1/pp2ca mutant plants, revealing that active PP2C protein phosphatases protect and stabilize RopGEF1 from ABA-mediated degradation. Interestingly, ABA-mediated degradation of RopGEF1 also plays an important role in ABA-mediated inhibition of lateral root growth. The presented findings point to a PP2C-RopGEF-ROP/RAC control loop model that is proposed to aid in shutting off ABA signal transduction, to counteract leaky ABA signal transduction caused by “monomeric” PYL/RCAR ABA receptors in the absence of stress, and facilitate signaling in response to ABA. PMID:27192441

Expression of Stipa purpurea SpCIPK26 in Arabidopsis thaliana Enhances Salt and Drought Tolerance and Regulates Abscisic Acid Signaling

PubMed Central

Zhou, Yanli; Sun, Xudong; Yang, Yunqiang; Li, Xiong; Cheng, Ying; Yang, Yongping

2016-01-01

Stipa purpurea (S. purpurea) is the dominant plant species in the alpine steppe of the Qinghai-Tibet Plateau, China. It is highly resistant to cold and drought conditions. However, the underlying mechanisms regulating the stress tolerance are unknown. In this study, a CIPK gene from S. purpurea (SpCIPK26) was isolated. The SpCIPK26 coding region consisted of 1392 bp that encoded 464 amino acids. The protein has a highly conserved catalytic structure and regulatory domain. The expression of SpCIPK26 was induced by drought and salt stress. SpCIPK26 overexpression in Arabidopsis thaliana (A. thaliana) plants provided increased tolerance to drought and salt stress in an abscisic acid (ABA)-dependent manner. Compared with wild-type A. thaliana plants, SpCIPK26-overexpressing plants had higher survival rates, water potentials, and photosynthetic efficiency (Fv/Fm), as well as lower levels of reactive oxygen species (ROS) following exposure to drought and salt stress. Gene expression analyses indicated stress-inducible genes (RD29A, RD29B, and ABF2) and a ROS-scavenger gene (CAT1) were upregulated in SpCIPK26-overexpressing plants after stress treatments. All of these marker genes are associated with ABA-responsive cis-acting elements. Additionally, the similarities in the gene expression patterns following ABA, mannitol, and NaCl treatments suggest SpCIPK26 has an important role during plant responses to drought and salt stress and in regulating ABA signaling. PMID:27338368

A distal ABA responsive element in AtNCED3 promoter is required for positive feedback regulation of ABA biosynthesis in Arabidopsis.

PubMed

Yang, Yan-Zhuo; Tan, Bao-Cai

2014-01-01

The plant hormone abscisic acid (ABA) plays a crucial role in plant development and responses to abiotic stresses. Recent studies indicate that a positive feedback regulation by ABA exists in ABA biosynthesis in plants under dehydration stress. To understand the molecular basis of this regulation, we analyzed the cis-elements of the AtNCED3 promoter in Arabidopsis. AtNCED3 encodes the first committed and highly regulated dioxygenase in the ABA biosynthetic pathway. Through delineated and mutagenesis analyses in stable-transformed Arabidopsis, we revealed that a distal ABA responsive element (ABRE: GGCACGTG, -2372 to -2364 bp) is required for ABA-induced AtNCED3 expression. By analyzing the AtNCED3 expression in ABRE binding protein ABF3 over-expression transgenic plants and knock-out mutants, we provide evidence that the ABA feedback regulation of AtNCED3 expression is not mediated by ABF3.

Exogenous auxin represses soybean seed germination through decreasing the gibberellin/abscisic acid (GA/ABA) ratio.

PubMed

Shuai, Haiwei; Meng, Yongjie; Luo, Xiaofeng; Chen, Feng; Zhou, Wenguan; Dai, Yujia; Qi, Ying; Du, Junbo; Yang, Feng; Liu, Jiang; Yang, Wenyu; Shu, Kai

2017-10-03

Auxin is an important phytohormone which mediates diverse development processes in plants. Published research has demonstrated that auxin induces seed dormancy. However, the precise mechanisms underlying the effect of auxin on seed germination need further investigation, especially the relationship between auxins and both abscisic acid (ABA) and gibberellins (GAs), the latter two phytohormones being the key regulators of seed germination. Here we report that exogenous auxin treatment represses soybean seed germination by enhancing ABA biosynthesis, while impairing GA biogenesis, and finally decreasing GA 1 /ABA and GA 4 /ABA ratios. Microscope observation showed that auxin treatment delayed rupture of the soybean seed coat and radicle protrusion. qPCR assay revealed that transcription of the genes involved in ABA biosynthetic pathway was up-regulated by application of auxin, while expression of genes involved in GA biosynthetic pathway was down-regulated. Accordingly, further phytohormone quantification shows that auxin significantly increased ABA content, whereas the active GA 1 and GA 4 levels were decreased, resulting insignificant decreases in the ratiosGA 1 /ABA and GA 4 /ABA.Consistent with this, ABA biosynthesis inhibitor fluridone reversed the delayed-germination phenotype associated with auxin treatment, while paclobutrazol, a GA biosynthesis inhibitor, inhibited soybean seed germination. Altogether, exogenous auxin represses soybean seed germination by mediating ABA and GA biosynthesis.

Development of sensors for monitoring oxygen and free radicals in plant physiology

NASA Astrophysics Data System (ADS)

Chaturvedi, Prachee

Oxygen plays a critical role in the physiology of photosynthetic organisms, including bioenergetics, metabolism, development, and stress response. Oxygen levels affect photosynthesis, respiration, and alternative oxidase pathways. Likewise, the metabolic rate of spatially distinct plant cells (and therefore oxygen flux) is known to be affected by biotic stress (e.g., herbivory) and environmental stress (e.g., salt/nutrient stress). During aerobic metabolism, cells produce reactive oxygen species (ROS) as a by product. Plants also produce ROS during adaptation to stress (e.g., abscisic acid (ABA) mediated stress responses). If stress conditions are prolonged, ROS levels surpass the capacity of detoxifying mechanisms within the cell, resulting in oxidative damage. While stress response pathways such as ABA-mediated mechanisms have been well characterized (e.g., water stress, inhibited shoot growth, synthesis of storage proteins in seeds), the connection between ROS production, oxygen metabolism and stress response remains unknown. In part, this is because details of oxygen transport at the interface of cell(s) and the surrounding microenvironment remains nebulous. The overall goal of this research was to develop oxygen and Free radical sensors for studying stress signaling in plants. Recent developments in nanomaterials and data acquisition systems were integrated to develop real-time, non-invasive oxygen and Free radical sensors. The availability of these sensors for plant physiologists is an exciting opportunity to probe the functional realm of cells and tissues in ways that were not previously possible.

Disruption of Abscisic Acid Signaling Constitutively Activates Arabidopsis Resistance to the Necrotrophic Fungus Plectosphaerella cucumerina1[W

PubMed Central

Sánchez-Vallet, Andrea; López, Gemma; Ramos, Brisa; Delgado-Cerezo, Magdalena; Riviere, Marie-Pierre; Llorente, Francisco; Fernández, Paula Virginia; Miedes, Eva; Estevez, José Manuel; Grant, Murray; Molina, Antonio

2012-01-01

Plant resistance to necrotrophic fungi is regulated by a complex set of signaling pathways that includes those mediated by the hormones salicylic acid (SA), ethylene (ET), jasmonic acid (JA), and abscisic acid (ABA). The role of ABA in plant resistance remains controversial, as positive and negative regulatory functions have been described depending on the plant-pathogen interaction analyzed. Here, we show that ABA signaling negatively regulates Arabidopsis (Arabidopsis thaliana) resistance to the necrotrophic fungus Plectosphaerella cucumerina. Arabidopsis plants impaired in ABA biosynthesis, such as the aba1-6 mutant, or in ABA signaling, like the quadruple pyr/pyl mutant (pyr1pyl1pyl2pyl4), were more resistant to P. cucumerina than wild-type plants. In contrast, the hab1-1abi1-2abi2-2 mutant impaired in three phosphatases that negatively regulate ABA signaling displayed an enhanced susceptibility phenotype to this fungus. Comparative transcriptomic analyses of aba1-6 and wild-type plants revealed that the ABA pathway negatively regulates defense genes, many of which are controlled by the SA, JA, or ET pathway. In line with these data, we found that aba1-6 resistance to P. cucumerina was partially compromised when the SA, JA, or ET pathway was disrupted in this mutant. Additionally, in the aba1-6 plants, some genes encoding cell wall-related proteins were misregulated. Fourier transform infrared spectroscopy and biochemical analyses of cell walls from aba1-6 and wild-type plants revealed significant differences in their Fourier transform infrared spectratypes and uronic acid and cellulose contents. All these data suggest that ABA signaling has a complex function in Arabidopsis basal resistance, negatively regulating SA/JA/ET-mediated resistance to necrotrophic fungi. PMID:23037505

The antagonistic regulation of abscisic acid-inhibited root growth by brassinosteroids is partially mediated via direct suppression of ABSCISIC ACID INSENSITIVE 5 expression by BRASSINAZOLE RESISTANT 1.

PubMed

Yang, Xiaorui; Bai, Yang; Shang, Jianxiu; Xin, Ruijiao; Tang, Wenqiang

2016-09-01

Brassinosteroids (BRs) and abscisic acid (ABA) are plant hormones that antagonistically regulate many aspects of plant growth and development; however, the mechanisms that regulate the crosstalk of these two hormones are still not well understood. BRs regulate plant growth and development by activating BRASSINAZOLE RESISTANT 1 (BZR1) family transcription factors. Here we show that the crosstalk between BRs and ABA signalling is partially mediated by BZR1 regulated gene expression. bzr1-1D is a dominant mutant with enhanced BR signalling; our results showed that bzr1-1D mutant is less sensitive to ABA-inhibited primary root growth. By RNA sequencing, a subset of BZR1 regulated ABA-responsive root genes were identified. Of these genes, the expression of a major ABA signalling component ABA INSENSITIVE 5 (ABI5) was found to be suppressed by BR and by BZR1. Additional evidences showed that BZR1 could bind strongly with several G-box cis-elements in the promoter of ABI5, suppress the expression of ABI5 and make plants less sensitive to ABA. Our study demonstrated that ABI5 is a direct target gene of BZR1, and modulating the expression of ABI5 by BZR1 plays important roles in regulating the crosstalk between the BR and ABA signalling pathways. © 2016 John Wiley & Sons Ltd.

A Distal ABA Responsive Element in AtNCED3 Promoter Is Required for Positive Feedback Regulation of ABA Biosynthesis in Arabidopsis

PubMed Central

Yang, Yan-Zhuo; Tan, Bao-Cai

2014-01-01

The plant hormone abscisic acid (ABA) plays a crucial role in plant development and responses to abiotic stresses. Recent studies indicate that a positive feedback regulation by ABA exists in ABA biosynthesis in plants under dehydration stress. To understand the molecular basis of this regulation, we analyzed the cis-elements of the AtNCED3 promoter in Arabidopsis. AtNCED3 encodes the first committed and highly regulated dioxygenase in the ABA biosynthetic pathway. Through delineated and mutagenesis analyses in stable-transformed Arabidopsis, we revealed that a distal ABA responsive element (ABRE: GGCACGTG, -2372 to -2364 bp) is required for ABA-induced AtNCED3 expression. By analyzing the AtNCED3 expression in ABRE binding protein ABF3 over-expression transgenic plants and knock-out mutants, we provide evidence that the ABA feedback regulation of AtNCED3 expression is not mediated by ABF3. PMID:24475264

The regulatory network of ThbZIP1 in response to abscisic acid treatment

PubMed Central

Ji, Xiaoyu; Liu, Guifeng; Liu, Yujia; Nie, Xianguang; Zheng, Lei; Wang, Yucheng

2015-01-01

Previously, a bZIP transcription factor from Tamarix hispida, ThbZIP1, was characterized: plants overexpressing ThbZIP1 displayed improved salt stress tolerance but were sensitive to abscisic acid (ABA). In the current study, we further characterized the regulatory network of ThbZIP1 and the mechanism of ABA sensitivity mediated by ThbZIP1. An ABF transcription factor from T. hispida, ThABF1, directly regulates the expression of ThbZIP1. Microarray analysis identified 1662 and 1609 genes that were respectively significantly upregulated or downregulated by ThbZIP1 when exposed to ABA. Gene ontology (GO) analysis showed that the processes including “response to stimulus,” “catalytic activity,” “binding function,” and “metabolic process” were highly altered in ThbZIP1 expressing plants exposed to ABA. The gene expression in ThbZIP1 transformed plants were compared between exposed to ABA and salt on the genome scale. Genes differentially regulated by both salt and ABA treatment only accounted for 9.75% of total differentially regulated genes. GO analysis showed that structural molecule activity, organelle part, membrane-enclosed lumen, reproduction, and reproductive process are enhanced by ABA but inhibited by salt stress. Conversely, immune system and multi-organism process were improved by salt but inhibited by ABA. Transcription regulator activity, enzyme regulator activity, and developmental process were significantly altered by ABA but were not affected by salt stress. Our study provides insights into how ThbZIP1 mediates ABA and salt stress response at the molecular level. PMID:25713576

Salt Stress Represses Soybean Seed Germination by Negatively Regulating GA Biosynthesis While Positively Mediating ABA Biosynthesis

PubMed Central

Shu, Kai; Qi, Ying; Chen, Feng; Meng, Yongjie; Luo, Xiaofeng; Shuai, Haiwei; Zhou, Wenguan; Ding, Jun; Du, Junbo; Liu, Jiang; Yang, Feng; Wang, Qiang; Liu, Weiguo; Yong, Taiwen; Wang, Xiaochun; Feng, Yuqi; Yang, Wenyu

2017-01-01

Soybean is an important and staple oilseed crop worldwide. Salinity stress has adverse effects on soybean development periods, especially on seed germination and post-germinative growth. Improving seed germination and emergence will have positive effects under salt stress conditions on agricultural production. Here we report that NaCl delays soybean seed germination by negatively regulating gibberellin (GA) while positively mediating abscisic acid (ABA) biogenesis, which leads to a decrease in the GA/ABA ratio. This study suggests that fluridone (FLUN), an ABA biogenesis inhibitor, might be a potential plant growth regulator that can promote soybean seed germination under saline stress. Different soybean cultivars, which possessed distinct genetic backgrounds, showed a similar repressed phenotype during seed germination under exogenous NaCl application. Biochemical analysis revealed that NaCl treatment led to high MDA (malondialdehyde) level during germination and the post-germinative growth stages. Furthermore, catalase, superoxide dismutase, and peroxidase activities also changed after NaCl treatment. Subsequent quantitative Real-Time Polymerase Chain Reaction analysis showed that the transcription levels of ABA and GA biogenesis and signaling genes were altered after NaCl treatment. In line with this, phytohormone measurement also revealed that NaCl considerably down-regulated active GA1, GA3, and GA4 levels, whereas the ABA content was up-regulated; and therefore ratios, such as GA1/ABA, GA3/ABA, and GA4/ABA, are decreased. Consistent with the hormonal quantification, FLUN partially rescued the delayed-germination phenotype caused by NaCl-treatment. Altogether, these results demonstrate that NaCl stress inhibits soybean seed germination by decreasing the GA/ABA ratio, and that FLUN might be a potential plant growth regulator that could promote soybean seed germination under salinity stress. PMID:28848576

Salt Stress Represses Soybean Seed Germination by Negatively Regulating GA Biosynthesis While Positively Mediating ABA Biosynthesis.

PubMed

Shu, Kai; Qi, Ying; Chen, Feng; Meng, Yongjie; Luo, Xiaofeng; Shuai, Haiwei; Zhou, Wenguan; Ding, Jun; Du, Junbo; Liu, Jiang; Yang, Feng; Wang, Qiang; Liu, Weiguo; Yong, Taiwen; Wang, Xiaochun; Feng, Yuqi; Yang, Wenyu

2017-01-01

Soybean is an important and staple oilseed crop worldwide. Salinity stress has adverse effects on soybean development periods, especially on seed germination and post-germinative growth. Improving seed germination and emergence will have positive effects under salt stress conditions on agricultural production. Here we report that NaCl delays soybean seed germination by negatively regulating gibberellin (GA) while positively mediating abscisic acid (ABA) biogenesis, which leads to a decrease in the GA/ABA ratio. This study suggests that fluridone (FLUN), an ABA biogenesis inhibitor, might be a potential plant growth regulator that can promote soybean seed germination under saline stress. Different soybean cultivars, which possessed distinct genetic backgrounds, showed a similar repressed phenotype during seed germination under exogenous NaCl application. Biochemical analysis revealed that NaCl treatment led to high MDA (malondialdehyde) level during germination and the post-germinative growth stages. Furthermore, catalase, superoxide dismutase, and peroxidase activities also changed after NaCl treatment. Subsequent quantitative Real-Time Polymerase Chain Reaction analysis showed that the transcription levels of ABA and GA biogenesis and signaling genes were altered after NaCl treatment. In line with this, phytohormone measurement also revealed that NaCl considerably down-regulated active GA 1 , GA 3 , and GA 4 levels, whereas the ABA content was up-regulated; and therefore ratios, such as GA 1 /ABA, GA 3 /ABA, and GA 4 /ABA, are decreased. Consistent with the hormonal quantification, FLUN partially rescued the delayed-germination phenotype caused by NaCl-treatment. Altogether, these results demonstrate that NaCl stress inhibits soybean seed germination by decreasing the GA/ABA ratio, and that FLUN might be a potential plant growth regulator that could promote soybean seed germination under salinity stress.

Transcription factor HAT1 is a substrate of SnRK2.3 kinase and negatively regulates ABA synthesis and signaling in Arabidopsis responding to drought.

PubMed

Tan, Wenrong; Zhang, Dawei; Zhou, Huapeng; Zheng, Ting; Yin, Yanhai; Lin, Honghui

2018-04-01

Drought is a major threat to plant growth and crop productivity. The phytohormone abscisic acid (ABA) plays a critical role in plant response to drought stress. Although ABA signaling-mediated drought tolerance has been widely investigated in Arabidopsis thaliana, the feedback mechanism and components negatively regulating this pathway are less well understood. Here we identified a member of Arabidopsis HD-ZIP transcription factors HAT1 which can interacts with and be phosphorylated by SnRK2s. hat1hat3, loss-of-function mutant of HAT1 and its homolog HAT3, was hypersensitive to ABA in primary root inhibition, ABA-responsive genes expression, and displayed enhanced drought tolerance, whereas HAT1 overexpressing lines were hyposensitive to ABA and less tolerant to drought stress, suggesting that HAT1 functions as a negative regulator in ABA signaling-mediated drought response. Furthermore, expression levels of ABA biosynthesis genes ABA3 and NCED3 were repressed by HAT1 directly binding to their promoters, resulting in the ABA level was increased in hat1hat3 and reduced in HAT1OX lines. Further evidence showed that both protein stability and binding activity of HAT1 was repressed by SnRK2.3 phosphorylation. Overexpressing SnRK2.3 in HAT1OX transgenic plant made a reduced HAT1 protein level and suppressed the HAT1OX phenotypes in ABA and drought response. Our results thus establish a new negative regulation mechanism of HAT1 which helps plants fine-tune their drought responses.

Arabidopsis HOOKLESS1 Regulates Responses to Pathogens and Abscisic Acid through Interaction with MED18 and Acetylation of WRKY33 and ABI5 Chromatin

PubMed Central

Liao, Chao-Jan; Lee, Sanghun; Mengiste, Tesfaye

2016-01-01

Arabidopsis thaliana HOOKLESS1 (HLS1) encodes a putative histone acetyltransferase with known functions in seedling growth. Here, we show that HLS1 regulates plant responses to pathogens and abscisic acid (ABA) through histone acetylation at chromatin of target loci. The hls1 mutants show impaired responses to bacterial and fungal infection, accelerated senescence, and impaired responses to ABA. HLS1 modulates the expression of WRKY33 and ABA INSENSITIVE5 (ABI5), known regulators of pathogen and ABA responses, respectively, through direct association with these loci. Histone 3 acetylation (H3Ac), a positive mark of transcription, at WRKY33 and ABI5 requires HLS1 function. ABA treatment and pathogen infection enhance HLS1 recruitment and H3Ac at WRKY33. HLS1 associates with Mediator, a eukaryotic transcription coregulatory complex, through direct interaction with mediator subunit 18 (MED18), with which it shares multiple functions. HLS1 recruits MED18 to the WRKY33 promoter, boosting WKRY33 expression, suggesting the synergetic action of HLS1 and MED18. By contrast, MED18 recruitment to ABI5 and transcriptional activation are independent of HLS1. ABA-mediated priming of resistance to fungal infection was abrogated in hls1 and wrky33 mutants but correlated with ABA-induced HLS1 accumulation. In sum, HLS1 provides a regulatory node in pathogen and hormone response pathways through interaction with the Mediator complex and important transcription factors. PMID:27317674

The Arabidopsis tandem CCCH zinc finger proteins AtTZF4, 5 and 6 are involved in light-, abscisic acid- and gibberellic acid-mediated regulation of seed germination.

PubMed

Bogamuwa, Srimathi; Jang, Jyan-Chyun

2013-08-01

Tandem CCCH zinc finger proteins (TZFs) are post-transcriptional regulators of gene expression in animals and yeast. Genetic studies indicate that plant TZFs are involved in hormone-mediated developmental and environmental responses. We have demonstrated previously that Arabidopsis AtTZF1 can localize to processing bodies (PBs) and stress granules (SGs), and affects abscisic acid (ABA)- and gibberellic acid (GA)-mediated growth, stress and gene expression responses. Here we show that AtTZF4, 5 and 6 are specifically expressed in seeds. Consistent with the observation that their expression levels decline during seed imbibition, AtTZF4, 5 and 6 are up-regulated by ABA and down-regulated by GA. Mutant analyses indicate that AtTZF4, 5 and 6 act as positive regulators for ABA- and negative regulators for light- and GA-mediated seed germination responses. Results of gene expression analysis indicate that AtTZF4, 5 and 6 affect seed germination by controlling genes critical for ABA and GA response. Furthermore, AtTZF4, 5 and 6 can co-localize with both PB and SG markers in Arabidopsis cells. Specifically, AtTZF6 can be assembled into PBs and SGs in embryos with the induction of stress hormone methyl jasmonate under the control of native AtTZF6 promoter. © 2013 John Wiley & Sons Ltd.

ROS signaling and stomatal movement in plant responses to drought stress and pathogen attack.

PubMed

Qi, Junsheng; Song, Chun-Peng; Wang, Baoshan; Zhou, Jianmin; Kangasjärvi, Jaakko; Zhu, Jian-Kang; Gong, Zhizhong

2018-04-16

Stomata, the pores formed by a pair of guard cells, are the main gateways for water transpiration and photosynthetic CO 2 exchange, as well as pathogen invasion in land plants. Guard cell movement is regulated by a combination of environmental factors including water status, light, CO 2 levels and pathogen attack, as well as endogenous signals such as abscisic acid and apoplastic reactive oxygen species (ROS). Under abiotic and biotic stress conditions, extracellular ROS are mainly produced by plasma membrane-localized NADPH oxidases, whereas intracellular ROS are produced in multiple organelles. These ROS form a sophisticated cellular signaling network, with the accumulation of apoplastic ROS an early hallmark of stomatal movement. Here, we review recent progress in understanding the molecular mechanisms of the ROS signaling network, primarily during drought stress and pathogen attack. We summarize the roles of apoplastic ROS in regulating stomatal movement, ABA and CO 2 signaling, and immunity responses. Finally, we discuss ROS accumulation and communication between organelles and cells. This information provides a conceptual framework for understanding how ROS signaling is integrated with various signaling pathways during plant responses to abiotic and biotic stress stimuli. This article is protected by copyright. All rights reserved.

Transcription Profiles Reveal Sugar and Hormone Signaling Pathways Mediating Flower Induction in Apple (Malus domestica Borkh.).

PubMed

Xing, Li-Bo; Zhang, Dong; Li, You-Mei; Shen, Ya-Wen; Zhao, Cai-Ping; Ma, Juan-Juan; An, Na; Han, Ming-Yu

2015-10-01

Flower induction in apple (Malus domestica Borkh.) is regulated by complex gene networks that involve multiple signal pathways to ensure flower bud formation in the next year, but the molecular determinants of apple flower induction are still unknown. In this research, transcriptomic profiles from differentiating buds allowed us to identify genes potentially involved in signaling pathways that mediate the regulatory mechanisms of flower induction. A hypothetical model for this regulatory mechanism was obtained by analysis of the available transcriptomic data, suggesting that sugar-, hormone- and flowering-related genes, as well as those involved in cell-cycle induction, participated in the apple flower induction process. Sugar levels and metabolism-related gene expression profiles revealed that sucrose is the initiation signal in flower induction. Complex hormone regulatory networks involved in cytokinin (CK), abscisic acid (ABA) and gibberellic acid pathways also induce apple flower formation. CK plays a key role in the regulation of cell formation and differentiation, and in affecting flowering-related gene expression levels during these processes. Meanwhile, ABA levels and ABA-related gene expression levels gradually increased, as did those of sugar metabolism-related genes, in developing buds, indicating that ABA signals regulate apple flower induction by participating in the sugar-mediated flowering pathway. Furthermore, changes in sugar and starch deposition levels in buds can be affected by ABA content and the expression of the genes involved in the ABA signaling pathway. Thus, multiple pathways, which are mainly mediated by crosstalk between sugar and hormone signals, regulate the molecular network involved in bud growth and flower induction in apple trees. © The Author 2015. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists.

The glutamate carboxypeptidase AMP1 mediates abscisic acid and abiotic stress responses in Arabidopsis.

PubMed

Shi, Yiting; Wang, Zheng; Meng, Pei; Tian, Siqi; Zhang, Xiaoyan; Yang, Shuhua

2013-07-01

ALTERED MERISTEM PROGRAM1 (AMP1) encodes a glutamate carboxypeptidase that plays an important role in shoot apical meristem development and phytohormone homeostasis. We isolated a new mutant allele of AMP1, amp1-20, from a screen for abscisic acid (ABA) hypersensitive mutants and characterized the function of AMP1 in plant stress responses. amp1 mutants displayed ABA hypersensitivity, while overexpression of AMP1 caused ABA insensitivity. Moreover, endogenous ABA concentration was increased in amp1-20- and decreased in AMP1-overexpressing plants under stress conditions. Application of ABA reduced the AMP1 protein level in plants. Interestingly, amp1 mutants accumulated excess superoxide and displayed hypersensitivity to oxidative stress. The hypersensitivity of amp1 to ABA and oxidative stress was partially rescued by reactive oxygen species (ROS) scavenging agent. Furthermore, amp1 was tolerant to freezing and drought stress. The ABA hypersensitivity and freezing tolerance of amp1 was dependent on ABA signaling. Moreover, amp1 had elevated soluble sugar content and showed hypersensitivity to high concentrations of sugar. By contrast, the contents of amino acids were changed in amp1 mutant compared to the wild-type. This study suggests that AMP1 modulates ABA, oxidative and abotic stress responses, and is involved in carbon and amino acid metabolism in Arabidopsis. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Stomata Prioritize Their Responses to Multiple Biotic and Abiotic Signal Inputs

PubMed Central

Chen, Peilei; Qiu, Muqing; Jiang, Kun; Wang, Genxuan

2014-01-01

Stomata are microscopic pores in leaf epidermis that regulate gas exchange between plants and the environment. Being natural openings on the leaf surface, stomata also serve as ports for the invasion of foliar pathogenic bacteria. Each stomatal pore is enclosed by a pair of guard cells that are able to sense a wide spectrum of biotic and abiotic stresses and respond by precisely adjusting the pore width. However, it is not clear whether stomatal responses to simultaneously imposed biotic and abiotic signals are mutually dependent on each other. Here we show that a genetically engineered Escherichia coli strain DH5α could trigger stomatal closure in Vicia faba, an innate immune response that might depend on NADPH oxidase-mediated ROS burst. DH5α-induced stomatal closure could be abolished or disguised under certain environmental conditions like low [CO2], darkness, and drought, etc. Foliar spraying of high concentrations of ABA could reduce stomatal aperture in high humidity-treated faba bean plants. Consistently, the aggressive multiplication of DH5α bacteria in Vicia faba leaves under high humidity could be alleviated by exogenous application of ABA. Our data suggest that a successful colonization of bacteria on the leaf surface is correlated with stomatal aperture regulation by a specific set of environmental factors. PMID:25003527

Singlet oxygen triggers chloroplast rupture and cell death in the zeaxanthin epoxidase defective mutant aba1 of Arabidopsis thaliana under high light stress.

PubMed

Sánchez-Corrionero, Álvaro; Sánchez-Vicente, Inmaculada; González-Pérez, Sergio; Corrales, Ascensión; Krieger-Liszkay, Anja; Lorenzo, Óscar; Arellano, Juan B

2017-09-01

The two Arabidopsis thaliana mutants, aba1 and max4, were previously identified as sharing a number of co-regulated genes with both the flu mutant and Arabidopsis cell suspension cultures exposed to high light (HL). On this basis, we investigated whether aba1 and max4 were generating high amounts of singlet oxygen ( 1 O 2 ) and activating 1 O 2 -mediated cell death. Thylakoids of aba1 produced twice as much 1 O 2 as thylakoids of max4 and wild type (WT) plants when illuminated with strong red light. 1 O 2 was measured using the spin probe 2,2,6,6-tetramethyl-4-piperidone hydrochloride. 77-K chlorophyll fluorescence emission spectra of thylakoids revealed lower aggregation of the light harvesting complex II in aba1. This was rationalized as a loss of connectivity between photosystem II (PSII) units and as the main cause for the high yield of 1 O 2 generation in aba1. Up-regulation of the 1 O 2 responsive gene AAA-ATPase was only observed with statistical significant in aba1 under HL. Two early jasmonate (JA)-responsive genes, JAZ1 and JAZ5, encoding for two repressor proteins involved in the negative feedback regulation of JA signalling, were not up-regulated to the WT plant levels. Chloroplast aggregation followed by chloroplast rupture and eventual cell death was observed by confocal imaging of the fluorescence emission of leaf cells of transgenic aba1 plants expressing the chimeric fusion protein SSU-GFP. Cell death was not associated with direct 1 O 2 cytotoxicity in aba1, but rather with a delayed stress response. In contrast, max4 did not show evidence of 1 O 2 -mediated cell death. In conclusion, aba1 may serve as an alternative model to other 1 O 2 -overproducing mutants of Arabidopsis for investigating 1 O 2 -mediated cell death. Copyright © 2017 Elsevier GmbH. All rights reserved.

Identification and functional characterization of the pepper CaDRT1 gene involved in the ABA-mediated drought stress response.

PubMed

Baek, Woonhee; Lim, Sohee; Lee, Sung Chul

2016-05-01

Plants are constantly challenged by various environmental stresses, including high salinity and drought, and they have evolved defense mechanisms to counteract the deleterious effects of these stresses. The plant hormone abscisic acid (ABA) regulates plant growth and developmental processes and mediates abiotic stress responses. Here, we identified the Capsicum annuum DRought Tolerance 1 (CaDRT1) gene from pepper leaves treated with ABA. CaDRT1 was strongly expressed in pepper leaves in response to environmental stresses and after ABA treatment, suggesting that the CaDRT1 protein functions in the abiotic stress response. Knockdown expression of CaDRT1 via virus-induced gene silencing resulted in a high level of drought susceptibility, and this was characterized by increased transpirational water loss via decreased stomatal closure. CaDRT1-overexpressing (OX) Arabidopsis plants exhibited an ABA-hypersensitive phenotype during the germinative, seedling, and adult stages. Additionally, these CaDRT1-OX plants exhibited a drought-tolerant phenotype characterized by low levels of transpirational water loss, high leaf temperatures, increased stomatal closure, and enhanced expression levels of drought-responsive genes. Taken together, our results suggest that CaDRT1 is a positive regulator of the ABA-mediated drought stress response.

The homeodomain-leucine zipper (HD-Zip) class I transcription factors ATHB7 and ATHB12 modulate abscisic acid signalling by regulating protein phosphatase 2C and abscisic acid receptor gene activities.

PubMed

Valdés, Ana Elisa; Overnäs, Elin; Johansson, Henrik; Rada-Iglesias, Alvaro; Engström, Peter

2012-11-01

Plants perceiving drought activate multiple responses to improve survival, including large-scale alterations in gene expression. This article reports on the roles in the drought response of two Arabidopsis thaliana homeodomain-leucine zipper class I genes; ATHB7 and ATHB12, both strongly induced by water-deficit and abscisic acid (ABA). ABA-mediated transcriptional regulation of both genes is shown to depend on the activity of protein phosphatases type 2C (PP2C). ATHB7 and ATHB12 are, thus, targets of the ABA signalling mechanism defined by the PP2Cs and the PYR/PYL family of ABA receptors, with which the PP2C proteins interact. Our results from chromatin immunoprecipitation and gene expression analyses demonstrate that ATHB7 and ATHB12 act as positive transcriptional regulators of PP2C genes, and thereby as negative regulators of abscisic acid signalling. In support of this notion, our results also show that ATHB7 and ATHB12 act to repress the transcription of genes encoding the ABA receptors PYL5 and PYL8 in response to an ABA stimulus. In summary, we demonstrate that ATHB7 and ATHB12 have essential functions in the primary response to drought, as mediators of a negative feedback effect on ABA signalling in the plant response to water deficit.

The Arabidopsis Vacuolar Sorting Receptor1 Is Required for Osmotic Stress-Induced Abscisic Acid Biosynthesis1[OPEN

PubMed Central

Wang, Zhen-Yu; Gehring, Chris; Zhu, Jianhua; Li, Feng-Min; Zhu, Jian-Kang; Xiong, Liming

2015-01-01

Osmotic stress activates the biosynthesis of the phytohormone abscisic acid (ABA) through a pathway that is rate limited by the carotenoid cleavage enzyme 9-cis-epoxycarotenoid dioxygenase (NCED). To understand the signal transduction mechanism underlying the activation of ABA biosynthesis, we performed a forward genetic screen to isolate mutants defective in osmotic stress regulation of the NCED3 gene. Here, we identified the Arabidopsis (Arabidopsis thaliana) Vacuolar Sorting Receptor1 (VSR1) as a unique regulator of ABA biosynthesis. The vsr1 mutant not only shows increased sensitivity to osmotic stress, but also is defective in the feedback regulation of ABA biosynthesis by ABA. Further analysis revealed that vacuolar trafficking mediated by VSR1 is required for osmotic stress-responsive ABA biosynthesis and osmotic stress tolerance. Moreover, under osmotic stress conditions, the membrane potential, calcium flux, and vacuolar pH changes in the vsr1 mutant differ from those in the wild type. Given that manipulation of the intracellular pH is sufficient to modulate the expression of ABA biosynthesis genes, including NCED3, and ABA accumulation, we propose that intracellular pH changes caused by osmotic stress may play a signaling role in regulating ABA biosynthesis and that this regulation is dependent on functional VSR1. PMID:25416474

Cuticle Biosynthesis in Tomato Leaves Is Developmentally Regulated by Abscisic Acid1[OPEN

PubMed Central

2017-01-01

The expansion of aerial organs in plants is coupled with the synthesis and deposition of a hydrophobic cuticle, composed of cutin and waxes, which is critically important in limiting water loss. While the abiotic stress-related hormone abscisic acid (ABA) is known to up-regulate wax accumulation in response to drought, the hormonal regulation of cuticle biosynthesis during organ ontogeny is poorly understood. To address the hypothesis that ABA also mediates cuticle formation during organ development, we assessed the effect of ABA deficiency on cuticle formation in three ABA biosynthesis-impaired tomato mutants. The mutant leaf cuticles were thinner, had structural abnormalities, and had a substantial reduction in levels of cutin. ABA deficiency also consistently resulted in differences in the composition of leaf cutin and cuticular waxes. Exogenous application of ABA partially rescued these phenotypes, confirming that they were a consequence of reduced ABA levels. The ABA mutants also showed reduced expression of genes involved in cutin or wax formation. This difference was again countered by exogenous ABA, further indicating regulation of cuticle biosynthesis by ABA. The fruit cuticles were affected differently by the ABA-associated mutations, but in general were thicker. However, no structural abnormalities were observed, and the cutin and wax compositions were less affected than in leaf cuticles, suggesting that ABA action influences cuticle formation in an organ-dependent manner. These results suggest dual roles for ABA in regulating leaf cuticle formation: one that is fundamentally associated with leaf expansion, independent of abiotic stress, and another that is drought induced. PMID:28483881

Cuticle Biosynthesis in Tomato Leaves Is Developmentally Regulated by Abscisic Acid.

PubMed

Martin, Laetitia B B; Romero, Paco; Fich, Eric A; Domozych, David S; Rose, Jocelyn K C

2017-07-01

The expansion of aerial organs in plants is coupled with the synthesis and deposition of a hydrophobic cuticle, composed of cutin and waxes, which is critically important in limiting water loss. While the abiotic stress-related hormone abscisic acid (ABA) is known to up-regulate wax accumulation in response to drought, the hormonal regulation of cuticle biosynthesis during organ ontogeny is poorly understood. To address the hypothesis that ABA also mediates cuticle formation during organ development, we assessed the effect of ABA deficiency on cuticle formation in three ABA biosynthesis-impaired tomato mutants. The mutant leaf cuticles were thinner, had structural abnormalities, and had a substantial reduction in levels of cutin. ABA deficiency also consistently resulted in differences in the composition of leaf cutin and cuticular waxes. Exogenous application of ABA partially rescued these phenotypes, confirming that they were a consequence of reduced ABA levels. The ABA mutants also showed reduced expression of genes involved in cutin or wax formation. This difference was again countered by exogenous ABA, further indicating regulation of cuticle biosynthesis by ABA. The fruit cuticles were affected differently by the ABA-associated mutations, but in general were thicker. However, no structural abnormalities were observed, and the cutin and wax compositions were less affected than in leaf cuticles, suggesting that ABA action influences cuticle formation in an organ-dependent manner. These results suggest dual roles for ABA in regulating leaf cuticle formation: one that is fundamentally associated with leaf expansion, independent of abiotic stress, and another that is drought induced. © 2017 American Society of Plant Biologists. All Rights Reserved.

C2-domain abscisic acid-related proteins mediate the interaction of PYR/PYL/RCAR abscisic acid receptors with the plasma membrane and regulate abscisic acid sensitivity in Arabidopsis.

PubMed

Rodriguez, Lesia; Gonzalez-Guzman, Miguel; Diaz, Maira; Rodrigues, Americo; Izquierdo-Garcia, Ana C; Peirats-Llobet, Marta; Fernandez, Maria A; Antoni, Regina; Fernandez, Daniel; Marquez, Jose A; Mulet, Jose M; Albert, Armando; Rodriguez, Pedro L

2014-12-01

Membrane-delimited abscisic acid (ABA) signal transduction plays a critical role in early ABA signaling, but the molecular mechanisms linking core signaling components to the plasma membrane are unclear. We show that transient calcium-dependent interactions of PYR/PYL ABA receptors with membranes are mediated through a 10-member family of C2-domain ABA-related (CAR) proteins in Arabidopsis thaliana. Specifically, we found that PYL4 interacted in an ABA-independent manner with CAR1 in both the plasma membrane and nucleus of plant cells. CAR1 belongs to a plant-specific gene family encoding CAR1 to CAR10 proteins, and bimolecular fluorescence complementation and coimmunoprecipitation assays showed that PYL4-CAR1 as well as other PYR/PYL-CAR pairs interacted in plant cells. The crystal structure of CAR4 was solved, which revealed that, in addition to a classical calcium-dependent lipid binding C2 domain, a specific CAR signature is likely responsible for the interaction with PYR/PYL receptors and their recruitment to phospholipid vesicles. This interaction is relevant for PYR/PYL function and ABA signaling, since different car triple mutants affected in CAR1, CAR4, CAR5, and CAR9 genes showed reduced sensitivity to ABA in seedling establishment and root growth assays. In summary, we identified PYR/PYL-interacting partners that mediate a transient Ca(2+)-dependent interaction with phospholipid vesicles, which affects PYR/PYL subcellular localization and positively regulates ABA signaling. © 2014 American Society of Plant Biologists. All rights reserved.

C2-Domain Abscisic Acid-Related Proteins Mediate the Interaction of PYR/PYL/RCAR Abscisic Acid Receptors with the Plasma Membrane and Regulate Abscisic Acid Sensitivity in Arabidopsis[C][W

PubMed Central

Rodriguez, Lesia; Diaz, Maira; Rodrigues, Americo; Izquierdo-Garcia, Ana C.; Peirats-Llobet, Marta; Fernandez, Maria A.; Antoni, Regina; Fernandez, Daniel; Marquez, Jose A.; Mulet, Jose M.; Albert, Armando; Rodriguez, Pedro L.

2014-01-01

Membrane-delimited abscisic acid (ABA) signal transduction plays a critical role in early ABA signaling, but the molecular mechanisms linking core signaling components to the plasma membrane are unclear. We show that transient calcium-dependent interactions of PYR/PYL ABA receptors with membranes are mediated through a 10-member family of C2-domain ABA-related (CAR) proteins in Arabidopsis thaliana. Specifically, we found that PYL4 interacted in an ABA-independent manner with CAR1 in both the plasma membrane and nucleus of plant cells. CAR1 belongs to a plant-specific gene family encoding CAR1 to CAR10 proteins, and bimolecular fluorescence complementation and coimmunoprecipitation assays showed that PYL4-CAR1 as well as other PYR/PYL-CAR pairs interacted in plant cells. The crystal structure of CAR4 was solved, which revealed that, in addition to a classical calcium-dependent lipid binding C2 domain, a specific CAR signature is likely responsible for the interaction with PYR/PYL receptors and their recruitment to phospholipid vesicles. This interaction is relevant for PYR/PYL function and ABA signaling, since different car triple mutants affected in CAR1, CAR4, CAR5, and CAR9 genes showed reduced sensitivity to ABA in seedling establishment and root growth assays. In summary, we identified PYR/PYL-interacting partners that mediate a transient Ca2+-dependent interaction with phospholipid vesicles, which affects PYR/PYL subcellular localization and positively regulates ABA signaling. PMID:25465408

Bromodomain proteins GTE9 and GTE11 are essential for specific BT2-mediated sugar and ABA responses in Arabidopsis thaliana.

PubMed

Misra, Anjali; McKnight, Thomas D; Mandadi, Kranthi K

2018-03-01

Global Transcription Factor Group E proteins GTE9 and GTE11 interact with BT2 to mediate ABA and sugar responses in Arabidopsis thaliana. BT2 is a BTB-domain protein that regulates responses to various hormone, stress and metabolic conditions in Arabidopsis thaliana. Loss of BT2 results in plants that are hypersensitive to inhibition of germination by abscisic acid (ABA) and sugars. Conversely, overexpression of BT2 results in resistance to ABA and sugars. Here, we report the roles of BT2-interacting partners GTE9 and GTE11, bromodomain and extraterminal-domain proteins of Global Transcription Factor Group E, in BT2-mediated responses to sugars and hormones. Loss-of-function mutants, gte9-1 and gte11-1, mimicked the bt2-1-null mutant responses; germination of all three mutants was hypersensitive to inhibition by glucose and ABA. Loss of either GTE9 or GTE11 in a BT2 over-expressing line blocked resistance to sugars and ABA, indicating that both GTE9 and GTE11 were required for BT2 function. Co-immunoprecipitation of BT2 and GTE9 suggested that these proteins physically interact in vivo, and presumably function together to mediate responses to ABA and sugar signals.

Quantitative statistical analysis of cis-regulatory sequences in ABA/VP1- and CBF/DREB1-regulated genes of Arabidopsis.

PubMed

Suzuki, Masaharu; Ketterling, Matthew G; McCarty, Donald R

2005-09-01

We have developed a simple quantitative computational approach for objective analysis of cis-regulatory sequences in promoters of coregulated genes. The program, designated MotifFinder, identifies oligo sequences that are overrepresented in promoters of coregulated genes. We used this approach to analyze promoter sequences of Viviparous1 (VP1)/abscisic acid (ABA)-regulated genes and cold-regulated genes, respectively, of Arabidopsis (Arabidopsis thaliana). We detected significantly enriched sequences in up-regulated genes but not in down-regulated genes. This result suggests that gene activation but not repression is mediated by specific and common sequence elements in promoters. The enriched motifs include several known cis-regulatory sequences as well as previously unidentified motifs. With respect to known cis-elements, we dissected the flanking nucleotides of the core sequences of Sph element, ABA response elements (ABREs), and the C repeat/dehydration-responsive element. This analysis identified the motif variants that may correlate with qualitative and quantitative differences in gene expression. While both VP1 and cold responses are mediated in part by ABA signaling via ABREs, these responses correlate with unique ABRE variants distinguished by nucleotides flanking the ACGT core. ABRE and Sph motifs are tightly associated uniquely in the coregulated set of genes showing a strict dependence on VP1 and ABA signaling. Finally, analysis of distribution of the enriched sequences revealed a striking concentration of enriched motifs in a proximal 200-base region of VP1/ABA and cold-regulated promoters. Overall, each class of coregulated genes possesses a discrete set of the enriched motifs with unique distributions in their promoters that may account for the specificity of gene regulation.

Overexpression of the transcription factor NF-YC9 confers abscisic acid hypersensitivity in Arabidopsis.

PubMed

Bi, Chao; Ma, Yu; Wang, Xiao-Fang; Zhang, Da-Peng

2017-11-01

Nuclear factor Y (NF-Y) family proteins are involved in many developmental processes and responses to environmental cues in plants, but whether and how they regulate phytohormone abscisic acid (ABA) signaling need further studies. In the present study, we showed that over-expression of the NF-YC9 gene confers ABA hypersensitivity in both the early seedling growth and stomatal response, while down-regulation of NF-YC9 does not affect ABA response in these processes. We also showed that over-expression of the NF-YC9 gene confers salt and osmotic hypersensitivity in early seedling growth, which is likely to be directly associated with the ABA hypersensitivity. Further, we observed that NF-YC9 physically interacts with the ABA-responsive bZIP transcription factor ABA-INSENSITIVE5 (ABI5), and facilitates the function of ABI5 to bind and activate the promoter of a target gene EM6. Additionally, NF-YC9 up-regulates expression of the ABI5 gene in response to ABA. These findings show that NF-YC9 may be involved in ABA signaling as a positive regulator and likely functions redundantly together with other NF-YC members, and support the model that the NF-YC9 mediates ABA signaling via targeting to and aiding the ABA-responsive transcription factors such as ABI5.

Abscisic Acid Regulates Inflammation via Ligand-binding Domain-independent Activation of Peroxisome Proliferator-activated Receptor γ*

PubMed Central

Bassaganya-Riera, Josep; Guri, Amir J.; Lu, Pinyi; Climent, Montse; Carbo, Adria; Sobral, Bruno W.; Horne, William T.; Lewis, Stephanie N.; Bevan, David R.; Hontecillas, Raquel

2011-01-01

Abscisic acid (ABA) has shown efficacy in the treatment of diabetes and inflammation; however, its molecular targets and the mechanisms of action underlying its immunomodulatory effects remain unclear. This study investigates the role of peroxisome proliferator-activated receptor γ (PPAR γ) and lanthionine synthetase C-like 2 (LANCL2) as molecular targets for ABA. We demonstrate that ABA increases PPAR γ reporter activity in RAW 264.7 macrophages and increases ppar γ expression in vivo, although it does not bind to the ligand-binding domain of PPAR γ. LANCL2 knockdown studies provide evidence that ABA-mediated activation of macrophage PPAR γ is dependent on lancl2 expression. Consistent with the association of LANCL2 with G proteins, we provide evidence that ABA increases cAMP accumulation in immune cells. ABA suppresses LPS-induced prostaglandin E2 and MCP-1 production via a PPAR γ-dependent mechanism possibly involving activation of PPAR γ and suppression of NF-κB and nuclear factor of activated T cells. LPS challenge studies in PPAR γ-expressing and immune cell-specific PPAR γ null mice demonstrate that ABA down-regulates toll-like receptor 4 expression in macrophages and T cells in vivo through a PPAR γ-dependent mechanism. Global transcriptomic profiling and confirmatory quantitative RT-PCR suggest novel candidate targets and demonstrate that ABA treatment mitigates the effect of LPS on the expression of genes involved in inflammation, metabolism, and cell signaling, in part, through PPAR γ. In conclusion, ABA decreases LPS-mediated inflammation and regulates innate immune responses through a bifurcating pathway involving LANCL2 and an alternative, ligand-binding domain-independent mechanism of PPAR γ activation. PMID:21088297

Abscisic acid regulates inflammation via ligand-binding domain-independent activation of peroxisome proliferator-activated receptor gamma.

PubMed

Bassaganya-Riera, Josep; Guri, Amir J; Lu, Pinyi; Climent, Montse; Carbo, Adria; Sobral, Bruno W; Horne, William T; Lewis, Stephanie N; Bevan, David R; Hontecillas, Raquel

2011-01-28

Abscisic acid (ABA) has shown efficacy in the treatment of diabetes and inflammation; however, its molecular targets and the mechanisms of action underlying its immunomodulatory effects remain unclear. This study investigates the role of peroxisome proliferator-activated receptor γ (PPAR γ) and lanthionine synthetase C-like 2 (LANCL2) as molecular targets for ABA. We demonstrate that ABA increases PPAR γ reporter activity in RAW 264.7 macrophages and increases ppar γ expression in vivo, although it does not bind to the ligand-binding domain of PPAR γ. LANCL2 knockdown studies provide evidence that ABA-mediated activation of macrophage PPAR γ is dependent on lancl2 expression. Consistent with the association of LANCL2 with G proteins, we provide evidence that ABA increases cAMP accumulation in immune cells. ABA suppresses LPS-induced prostaglandin E(2) and MCP-1 production via a PPAR γ-dependent mechanism possibly involving activation of PPAR γ and suppression of NF-κB and nuclear factor of activated T cells. LPS challenge studies in PPAR γ-expressing and immune cell-specific PPAR γ null mice demonstrate that ABA down-regulates toll-like receptor 4 expression in macrophages and T cells in vivo through a PPAR γ-dependent mechanism. Global transcriptomic profiling and confirmatory quantitative RT-PCR suggest novel candidate targets and demonstrate that ABA treatment mitigates the effect of LPS on the expression of genes involved in inflammation, metabolism, and cell signaling, in part, through PPAR γ. In conclusion, ABA decreases LPS-mediated inflammation and regulates innate immune responses through a bifurcating pathway involving LANCL2 and an alternative, ligand-binding domain-independent mechanism of PPAR γ activation.

Abscisic acid induction of vacuolar H+-ATPase activity in mesembryanthemum crystallinum is developmentally regulated

PubMed

Barkla; Vera-Estrella; Maldonado-Gama; Pantoja

1999-07-01

Abscisic acid (ABA) has been implicated as a key component in water-deficit-induced responses, including those triggered by drought, NaCl, and low- temperature stress. In this study a role for ABA in mediating the NaCl-stress-induced increases in tonoplast H+-translocating ATPase (V-ATPase) and Na+/H+ antiport activity in Mesembryanthemum crystallinum, leading to vacuolar Na+ sequestration, were investigated. NaCl or ABA treatment of adult M. crystallinum plants induced V-ATPase H+ transport activity, and when applied in combination, an additive effect on V-ATPase stimulation was observed. In contrast, treatment of juvenile plants with ABA did not induce V-ATPase activity, whereas NaCl treatment resulted in a similar response to that observed in adult plants. Na+/H+ antiport activity was induced in both juvenile and adult plants by NaCl, but ABA had no effect at either developmental stage. Results indicate that ABA-induced changes in V-ATPase activity are dependent on the plant reaching its adult phase, whereas NaCl-induced increases in V-ATPase and Na+/H+ antiport activity are independent of plant age. This suggests that ABA-induced V-ATPase activity may be linked to the stress-induced, developmentally programmed switch from C3 metabolism to Crassulacean acid metabolism in adult plants, whereas, vacuolar Na+ sequestration, mediated by the V-ATPase and Na+/H+ antiport, is regulated through ABA-independent pathways.

Up-Regulation of HSFA2c and HSPs by ABA Contributing to Improved Heat Tolerance in Tall Fescue and Arabidopsis

PubMed Central

Wang, Xiuyun; Zhuang, Lili; Huang, Bingru

2017-01-01

Abscisic acid (ABA) is known to play roles in regulating plant tolerance to various abiotic stresses, but whether ABA’s effects on heat tolerance are associated with its regulation of heat stress transcription factors (HSFs) and heat shock proteins (HSPs) is not well documented. The objective of this study was to determine whether improved heat tolerance of tall fescue (Festuca arundinacea Schreb.) by ABA was through the regulation of HSFs and HSPs. ABA-responsive transcriptional factors, ABA-responsive element binding protein 3 (FaAREB3) and dehydration-responsive element binding protein 2A (FaDREB2A) of tall fescue, were able to bind to the cis-elements in the promoter of tall fescue heat stress transcription factor A2c (FaHSFA2c). Exogenous ABA (5 μM) application enhanced heat tolerance of tall fescue, as manifested by increased leaf photochemical efficiency and membrane stability under heat stress (37/32 °C, day/night). The expression levels of FaHSFA2c, several tall fescue HSPs (FaHSPs), and ABA-responsive transcriptional factors were up-regulated in plants treated with ABA. Deficiency of Arabidopsis heat stress transcription factor A2 (AtHSFA2) suppressed ABA-induction of AtHSPs expression and ABA-improved heat tolerance in Arabidopsis. These results suggested that HSFA2 plays an important role in ABA-mediated plant heat tolerance, and FaAREB3 and FaDREB2A may function as upstream trans-acting factors and regulate transcriptional activity of FaHSFA2c and the downstream FaHSPs, leading to improved heat tolerance. PMID:28914758

Negative feedback regulation of ABA biosynthesis in peanut (Arachis hypogaea): a transcription factor complex inhibits AhNCED1 expression during water stress

PubMed Central

Liu, Shuai; Li, Meijuan; Su, Liangchen; Ge, Kui; Li, Limei; Li, Xiaoyun; Liu, Xu; Li, Ling

2016-01-01

Abscisic acid (ABA), a key plant stress-signaling hormone, is produced in response to drought and counteracts the effects of this stress. The accumulation of ABA is controlled by the enzyme 9-cis-epoxycarotenoid dioxygenase (NCED). In Arabidopsis, NCED3 is regulated by a positive feedback mechanism by ABA. In this study in peanut (Arachis hypogaea), we demonstrate that ABA biosynthesis is also controlled by negative feedback regulation, mediated by the inhibitory effect on AhNCED1 transcription of a protein complex between transcription factors AhNAC2 and AhAREB1. AhNCED1 was significantly down-regulated after PEG treatment for 10 h, at which time ABA content reached a peak. A ChIP-qPCR assay confirmed AhAREB1 and AhNAC2 binding to the AhNCED1 promoter in response to ABA. Moreover, the interaction between AhAREB1 and AhNAC2, and a transient expression assay showed that the protein complex could negatively regulate the expression of AhNCED1. The results also demonstrated that AhAREB1 was the key factor in AhNCED1 feedback regulation, while AhNAC2 played a subsidiary role. ABA reduced the rate of AhAREB1 degradation and enhanced both the synthesis and degradation rate of the AhNAC2 protein. In summary, the AhAREB1/AhNAC2 protein complex functions as a negative feedback regulator of drought-induced ABA biosynthesis in peanut. PMID:27892506

Role of nitric oxide in regulating stomatal apertures

PubMed Central

Ribeiro, Dimas M; Bright, Jo; Confraria, Ana; Harrison, Judith; Barros, Raimundo S; Desikan, Radhika; Neill, Steven J; Hancock, John T

2009-01-01

During stomatal closure, nitric oxide (NO) operates as one of the key intermediates in the complex, abscisic acid (ABA)-mediated, guard cell signaling network that regulates this process. However, data concerning the role of NO in stomatal closure that occurs in turgid vs. dehydrated plants is limited. The data presented demonstrate that, while there is a requirement for NO during the ABA-induced stomatal closure of turgid leaves, such a requirement does not exist for ABA-enhanced stomatal closure observed to occur during conditions of rapid dehydration. The data also indicate that the ABA signaling pathway must be both functional and to some degree activated for guard cell NO signaling to occur. These observations are in line with the idea that the effects of NO in guard cells are mediated via a Ca2+-dependent rather than a Ca2+-independent ABA signaling pathway. It appears that there is a role for NO in the fine tuning of the stomatal apertures of turgid leaves that occurs in response to fluctuations in the prevailing environment. PMID:19816112

Cloning and function analysis of a drought-inducible gene associated with resistance to Curvularia leaf spot in maize.

PubMed

Zhu, Jiewei; Huang, Xiuli; Liu, Tong; Gao, Shigang; Chen, Jie

2012-08-01

ZmDIP was cloned and its function against Curvularia lunata was analyzed, according to a previous finding on a drought-inducible protein in resistant maize identified through MALDI-TOF-MS/MS. The ZmDIP expression varied in roots, leaf sheaths, and young, as well as old, leaves of different maize inbred lines. The ZmDIP transcript level changed in leaves over the course of time after inoculation with C. lunata. A prokaryotic expression analysis demonstrated that the gene can regulate the salt stress tolerance of Escherichia coli. The ZmDIP transient expression in the maize leaf showed that the gene was also linked to leaf resistance against the C. lunata infection. ZmDIP-mediated ROS and ABA signaling pathways were inferred to be closely associated with maize leaf resistance to the pathogen infection.

The Pepper WPP Domain Protein, CaWDP1, Acts as a Novel Negative Regulator of Drought Stress via ABA Signaling.

PubMed

Park, Chanmi; Lim, Chae Woo; Baek, Woonhee; Kim, Jung-Hyun; Lim, Sohee; Kim, Sang Hyon; Kim, Kyung-Nam; Lee, Sung Chul

2017-04-01

Plants are constantly challenged by various environmental stresses, including high salinity and drought, and they have evolved defense mechanisms to counteract the deleterious effects of these stresses. The plant hormone ABA regulates plant growth and developmental processes and mediates abiotic stress responses. Here, we report the identification and characterization of a novel CaWDP1 (Capsicum annuum) protein. The expression of CaWDP1 in pepper leaves was induced by ABA, drought and NaCl treatments, suggesting its role in the abiotic stress response. CaWDP1 proteins show conserved sequence homology with other known WDP1 proteins, and they are localized in the nucleus and cytoplasm. We generated CaWDP1-silenced peppers via virus-induced gene silencing (VIGS). We evaluated the responses of these CaWDP1-silenced pepper plants and CaWDP1-overexpressing (OX) transgenic Arabidopsis plants to ABA and drought. CaWDP1-silenced pepper plants displayed enhanced tolerance to drought stress, and this was characterized by low levels of leaf water loss in the drought-treated leaves. In contrast to CaWDP1-silenced plants, CaWDP1-OX plants exhibited an ABA-hyposensitive and drought-susceptible phenotype, which was accompanied by high levels of leaf water loss, low leaf temperatures, increased stomatal pore size and low expression levels of stress-responsive genes. Our results indicate that CaWDP1, a novel pepper negative regulator of ABA, regulates the ABA-mediated defense response to drought stress. © The Author 2017. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Role of protein farnesylation events in the ABA-mediated regulation of the Pinoresinol-Lariciresinol Reductase 1 (LuPLR1) gene expression and lignan biosynthesis in flax (Linum usitatissimum L.).

PubMed

Corbin, Cyrielle; Decourtil, Cédric; Marosevic, Djurdjica; Bailly, Marlène; Lopez, Tatiana; Renouard, Sullivan; Doussot, Joël; Dutilleul, Christelle; Auguin, Daniel; Giglioli-Guivarc'h, Nathalie; Lainé, Eric; Lamblin, Frédéric; Hano, Christophe

2013-11-01

A Linum usitatissimum LuERA1 gene encoding a putative ortholog of the ERA1 (Enhanced Response to ABA 1) gene of Arabidopsis thaliana (encoding the beta subunit of a farnesyltransferase) was analyzed in silico and for its expression in flax. The gene and the protein sequences are highly similar to other sequences already characterized in plants and all the features of a farnesyltransferase were detected. Molecular modeling of LuERA1 protein confirmed its farnesyltransferase nature. LuERA1 is expressed in the vegetative organs and also in the outer seedcoat of the flaxseed, where it could modulate the previously observed regulation operated by ABA on lignan synthesis. This effect could be mediated by the regulation of the transcription of a key gene for lignan synthesis in flax, the LuPLR1 gene, encoding a pinoresinol lariciresinol reductase. The positive effect of manumycin A, a specific inhibitor of farnesyltransferase, on lignan biosynthesis in flax cell suspension systems supports the hypothesis of the involvement of such an enzyme in the negative regulation of ABA action. In Arabidopsis, ERA1 is able to negatively regulate the ABA effects and the mutant era1 has an enhanced sensitivity to ABA. When expressed in an Arabidopsis cell suspension (heterologous system) LuERA1 is able to reverse the effect of the era1 mutation. RNAi experiments in flax targeting the farnesyltransferase β-subunit encoded by the LuERA1 gene led to an increase LuPLR1 expression level associated with an increased content of lignan in transgenic calli. Altogether these results strongly suggest a role of the product of this LuERA1 gene in the ABA-mediated upregulation of lignan biosynthesis in flax cells through the activation of LuPLR1 promoter. This ABA signaling pathway involving ERA1 probably acts through the ABRE box found in the promoter sequence of LuPLR1, a key gene for lignan synthesis in flax, as demonstrated by LuPLR1 gene promoter-reporter experiments in flax cells using wild type and mutated promoter sequences. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Arabidopsis plants deficient in plastidial glyceraldehyde-3-phosphate dehydrogenase show alterations in abscisic acid (ABA) signal transduction: interaction between ABA and primary metabolism

PubMed Central

Muñoz-Bertomeu, Jesús; Bermúdez, María Angeles; Segura, Juan; Ros, Roc

2011-01-01

Abscisic acid (ABA) controls plant development and regulates plant responses to environmental stresses. A role for ABA in sugar regulation of plant development has also been well documented although the molecular mechanisms connecting the hormone with sugar signal transduction pathways are not well understood. In this work it is shown that Arabidopsis thaliana mutants deficient in plastidial glycolytic glyceraldehyde-3-phosphate dehydrogenase (gapcp1gapcp2) are ABA insensitive in growth, stomatal closure, and germination assays. The ABA levels of gapcp1gapcp2 were normal, suggesting that the ABA signal transduction pathway is impaired in the mutants. ABA modified gapcp1gapcp2 gene expression, but the mutant response to the hormone differed from that observed in wild-type plants. The gene expression of the transcription factor ABI4, involved in both sugar and ABA signalling, was altered in gapcp1gapcp2, suggesting that their ABA insensitivity is mediated, at least partially, through this transcriptional regulator. Serine supplementation was able partly to restore the ABA sensitivity of gapcp1gapcp2, indicating that amino acid homeostasis and/or serine metabolism may also be important determinants in the connections of ABA with primary metabolism. Overall, these studies provide new insights into the links between plant primary metabolism and ABA signalling, and demonstrate the importance of plastidial glycolytic glyceraldehyde-3-phosphate dehydrogenase in these interactions. PMID:21068209

The NF-YC–RGL2 module integrates GA and ABA signalling to regulate seed germination in Arabidopsis

PubMed Central

Liu, Xu; Hu, Pengwei; Huang, Mingkun; Tang, Yang; Li, Yuge; Li, Ling; Hou, Xingliang

2016-01-01

The antagonistic crosstalk between gibberellic acid (GA) and abscisic acid (ABA) plays a pivotal role in the modulation of seed germination. However, the molecular mechanism of such phytohormone interaction remains largely elusive. Here we show that three Arabidopsis NUCLEAR FACTOR-Y C (NF-YC) homologues NF-YC3, NF-YC4 and NF-YC9 redundantly modulate GA- and ABA-mediated seed germination. These NF-YCs interact with the DELLA protein RGL2, a key repressor of GA signalling. The NF-YC–RGL2 module targets ABI5, a gene encoding a core component of ABA signalling, via specific CCAAT elements and collectively regulates a set of GA- and ABA-responsive genes, thus controlling germination. These results suggest that the NF-YC–RGL2–ABI5 module integrates GA and ABA signalling pathways during seed germination. PMID:27624486

Analysis of Cytokinin Mutants and Regulation of Cytokinin Metabolic Genes Reveals Important Regulatory Roles of Cytokinins in Drought, Salt and Abscisic Acid Responses, and Abscisic Acid Biosynthesis[C][W

PubMed Central

Nishiyama, Rie; Watanabe, Yasuko; Fujita, Yasunari; Le, Dung Tien; Kojima, Mikiko; Werner, Tomás; Vankova, Radomira; Yamaguchi-Shinozaki, Kazuko; Shinozaki, Kazuo; Kakimoto, Tatsuo; Sakakibara, Hitoshi; Schmülling, Thomas; Tran, Lam-Son Phan

2011-01-01

Cytokinins (CKs) regulate plant growth and development via a complex network of CK signaling. Here, we perform functional analyses with CK-deficient plants to provide direct evidence that CKs negatively regulate salt and drought stress signaling. All CK-deficient plants with reduced levels of various CKs exhibited a strong stress-tolerant phenotype that was associated with increased cell membrane integrity and abscisic acid (ABA) hypersensitivity rather than stomatal density and ABA-mediated stomatal closure. Expression of the Arabidopsis thaliana ISOPENTENYL-TRANSFERASE genes involved in the biosynthesis of bioactive CKs and the majority of the Arabidopsis CYTOKININ OXIDASES/DEHYDROGENASES genes was repressed by stress and ABA treatments, leading to a decrease in biologically active CK contents. These results demonstrate a novel mechanism for survival under abiotic stress conditions via the homeostatic regulation of steady state CK levels. Additionally, under normal conditions, although CK deficiency increased the sensitivity of plants to exogenous ABA, it caused a downregulation of key ABA biosynthetic genes, leading to a significant reduction in endogenous ABA levels in CK-deficient plants relative to the wild type. Taken together, this study provides direct evidence that mutual regulation mechanisms exist between the CK and ABA metabolism and signals underlying different processes regulating plant adaptation to stressors as well as plant growth and development. PMID:21719693

Auxin as a player in the biocontrol of Fusarium head blight disease of barley and its potential as a disease control agent.

PubMed

Petti, Carloalberto; Reiber, Kathrin; Ali, Shahin S; Berney, Margaret; Doohan, Fiona M

2012-11-22

Mechanisms involved in the biological control of plant diseases are varied and complex. Hormones, including the auxin indole acetic acid (IAA) and abscisic acid (ABA), are essential regulators of a multitude of biological functions, including plant responses to biotic and abiotic stressors. This study set out to determine what hormones might play a role in Pseudomonas fluorescens -mediated control of Fusarium head blight (FHB) disease of barley and to determine if biocontrol-associated hormones directly affect disease development. A previous study distinguished bacterium-responsive genes from bacterium-primed genes, distinguished by the fact that the latter are only up-regulated when both P. fluorescens and the pathogen Fusarium culmorum are present. In silico analysis of the promoter sequences available for a subset of the bacterium-primed genes identified several hormones, including IAA and ABA as potential regulators of transcription. Treatment with the bacterium or pathogen resulted in increased IAA and ABA levels in head tissue; both microbes had additive effects on the accumulation of IAA but not of ABA. The microbe-induced accumulation of ABA preceded that of IAA. Gene expression analysis showed that both hormones up-regulated the accumulation of bacterium-primed genes. But IAA, more than ABA up-regulated the transcription of the ABA biosynthesis gene NCED or the signalling gene Pi2, both of which were previously shown to be bacterium-responsive rather than primed. Application of IAA, but not of ABA reduced both disease severity and yield loss caused by F. culmorum, but neither hormone affect in vitro fungal growth. Both IAA and ABA are involved in the P. fluorescens-mediated control of FHB disease of barley. Gene expression studies also support the hypothesis that IAA plays a role in the primed response to F. culmorum. This hypothesis was validated by the fact that pre-application of IAA reduced both symptoms and yield loss asssociated with the disease. This is the first evidence that IAA plays a role in the control of FHB disease and in the bacterial priming of host defences.

Auxin as a player in the biocontrol of Fusarium head blight disease of barley and its potential as a disease control agent

PubMed Central

2012-01-01

Background Mechanisms involved in the biological control of plant diseases are varied and complex. Hormones, including the auxin indole acetic acid (IAA) and abscisic acid (ABA), are essential regulators of a multitude of biological functions, including plant responses to biotic and abiotic stressors. This study set out to determine what hormones might play a role in Pseudomonas fluorescens –mediated control of Fusarium head blight (FHB) disease of barley and to determine if biocontrol-associated hormones directly affect disease development. Results A previous study distinguished bacterium-responsive genes from bacterium-primed genes, distinguished by the fact that the latter are only up-regulated when both P. fluorescens and the pathogen Fusarium culmorum are present. In silico analysis of the promoter sequences available for a subset of the bacterium-primed genes identified several hormones, including IAA and ABA as potential regulators of transcription. Treatment with the bacterium or pathogen resulted in increased IAA and ABA levels in head tissue; both microbes had additive effects on the accumulation of IAA but not of ABA. The microbe-induced accumulation of ABA preceded that of IAA. Gene expression analysis showed that both hormones up-regulated the accumulation of bacterium-primed genes. But IAA, more than ABA up-regulated the transcription of the ABA biosynthesis gene NCED or the signalling gene Pi2, both of which were previously shown to be bacterium-responsive rather than primed. Application of IAA, but not of ABA reduced both disease severity and yield loss caused by F. culmorum, but neither hormone affect in vitro fungal growth. Conclusions Both IAA and ABA are involved in the P. fluorescens-mediated control of FHB disease of barley. Gene expression studies also support the hypothesis that IAA plays a role in the primed response to F. culmorum. This hypothesis was validated by the fact that pre-application of IAA reduced both symptoms and yield loss asssociated with the disease. This is the first evidence that IAA plays a role in the control of FHB disease and in the bacterial priming of host defences. PMID:23173736

Abscisic acid analogs as chemical probes for dissection of abscisic acid responses in Arabidopsis thaliana.

PubMed

Benson, Chantel L; Kepka, Michal; Wunschel, Christian; Rajagopalan, Nandhakishore; Nelson, Ken M; Christmann, Alexander; Abrams, Suzanne R; Grill, Erwin; Loewen, Michele C

2015-05-01

Abscisic acid (ABA) is a phytohormone known to mediate numerous plant developmental processes and responses to environmental stress. In Arabidopsis thaliana, ABA acts, through a genetically redundant family of ABA receptors entitled Regulatory Component of ABA Receptor (RCAR)/Pyrabactin Resistant 1 (PYR1)/Pyrabactin Resistant-Like (PYL) receptors comprised of thirteen homologues acting in concert with a seven-member set of phosphatases. The individual contributions of A. thaliana RCARs and their binding partners with respect to specific physiological functions are as yet poorly understood. Towards developing efficacious plant growth regulators selective for specific ABA functions and tools for elucidating ABA perception, a panel of ABA analogs altered specifically on positions around the ABA ring was assembled. These analogs have been used to probe thirteen RCARs and four type 2C protein phosphatases (PP2Cs) and were also screened against representative physiological assays in the model plant Arabidopsis. The 1'-O methyl ether of (S)-ABA was identified as selective in that, at physiologically relevant levels, it regulates stomatal aperture and improves drought tolerance, but does not inhibit germination or root growth. Analogs with the 7'- and 8'-methyl groups of the ABA ring replaced with bulkier groups generally retained the activity and stereoselectivity of (S)- and (R)-ABA, while alteration of the 9'-methyl group afforded an analog that substituted for ABA in inhibiting germination but neither root growth nor stomatal closure. Further in vitro testing indicated differences in binding of analogs to individual RCARs, as well as differences in the enzyme activity resulting from specific PP2Cs bound to RCAR-analog complexes. Ultimately, these findings highlight the potential of a broader chemical genetics approach for dissection of the complex network mediating ABA-perception, signaling and functionality within a given species and modifications in the future design of ABA agonists. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

Abscisic Acid Induction of Vacuolar H+-ATPase Activity in Mesembryanthemum crystallinum Is Developmentally Regulated1

PubMed Central

Barkla, Bronwyn J.; Vera-Estrella, Rosario; Maldonado-Gama, Minerva; Pantoja, Omar

1999-01-01

Abscisic acid (ABA) has been implicated as a key component in water-deficit-induced responses, including those triggered by drought, NaCl, and low- temperature stress. In this study a role for ABA in mediating the NaCl-stress-induced increases in tonoplast H+-translocating ATPase (V-ATPase) and Na+/H+ antiport activity in Mesembryanthemum crystallinum, leading to vacuolar Na+ sequestration, were investigated. NaCl or ABA treatment of adult M. crystallinum plants induced V-ATPase H+ transport activity, and when applied in combination, an additive effect on V-ATPase stimulation was observed. In contrast, treatment of juvenile plants with ABA did not induce V-ATPase activity, whereas NaCl treatment resulted in a similar response to that observed in adult plants. Na+/H+ antiport activity was induced in both juvenile and adult plants by NaCl, but ABA had no effect at either developmental stage. Results indicate that ABA-induced changes in V-ATPase activity are dependent on the plant reaching its adult phase, whereas NaCl-induced increases in V-ATPase and Na+/H+ antiport activity are independent of plant age. This suggests that ABA-induced V-ATPase activity may be linked to the stress-induced, developmentally programmed switch from C3 metabolism to Crassulacean acid metabolism in adult plants, whereas, vacuolar Na+ sequestration, mediated by the V-ATPase and Na+/H+ antiport, is regulated through ABA-independent pathways. PMID:10398716

Up-regulating the abscisic acid inactivation gene ZmABA8ox1b contributes to seed germination heterosis by promoting cell expansion.

PubMed

Li, Yangyang; Wang, Cheng; Liu, Xinye; Song, Jian; Li, Hongjian; Sui, Zhipeng; Zhang, Ming; Fang, Shuang; Chu, Jinfang; Xin, Mingming; Xie, Chaojie; Zhang, Yirong; Sun, Qixin; Ni, Zhongfu

2016-04-01

Heterosis has been widely used in agriculture, but the underlying molecular principles are still largely unknown. During seed germination, we observed that maize (Zea mays) hybrid B73/Mo17 was less sensitive than its parental inbred lines to exogenous abscisic acid (ABA), and endogenous ABA content in hybrid embryos decreased more rapidly than in the parental inbred lines. ZmABA8ox1b, an ABA inactivation gene, was consistently more highly up-regulated in hybrid B73/Mo17 than in its parental inbred lines at early stages of seed germination. Moreover, ectopic expression of ZmABA8ox1b obviously promoted seed germination in Arabidopsis Remarkably, microscopic observation revealed that cell expansion played a major role in the ABA-mediated maize seed germination heterosis, which could be attributed to the altered expression of cell wall-related genes. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

An ABRE promoter sequence is involved in osmotic stress-responsive expression of the DREB2A gene, which encodes a transcription factor regulating drought-inducible genes in Arabidopsis.

PubMed

Kim, June-Sik; Mizoi, Junya; Yoshida, Takuya; Fujita, Yasunari; Nakajima, Jun; Ohori, Teppei; Todaka, Daisuke; Nakashima, Kazuo; Hirayama, Takashi; Shinozaki, Kazuo; Yamaguchi-Shinozaki, Kazuko

2011-12-01

In plants, osmotic stress-responsive transcriptional regulation depends mainly on two major classes of cis-acting elements found in the promoter regions of stress-inducible genes: ABA-responsive elements (ABREs) and dehydration-responsive elements (DREs). ABRE has been shown to perceive ABA-mediated osmotic stress signals, whereas DRE is known to be involved in an ABA-independent pathway. Previously, we reported that the transcription factor DRE-BINDING PROTEIN 2A (DREB2A) regulates DRE-mediated transcription of target genes under osmotic stress conditions in Arabidopsis (Arabidopsis thaliana). However, the transcriptional regulation of DREB2A itself remains largely uncharacterized. To elucidate the transcriptional mechanism associated with the DREB2A gene under osmotic stress conditions, we generated a series of truncated and base-substituted variants of the DREB2A promoter and evaluated their transcriptional activities individually. We found that both ABRE and coupling element 3 (CE3)-like sequences located approximately -100 bp from the transcriptional initiation site are necessary for the dehydration-responsive expression of DREB2A. Coupling our transient expression analyses with yeast one-hybrid and chromatin immunoprecipitation (ChIP) assays indicated that the ABRE-BINDING PROTEIN 1 (AREB1), AREB2 and ABRE-BINDING FACTOR 3 (ABF3) bZIP transcription factors can bind to and activate the DREB2A promoter in an ABRE-dependent manner. Exogenous ABA application induced only a modest accumulation of the DREB2A transcript when compared with the osmotic stress treatment. However, the osmotic stress-induced DREB2A expression was found to be markedly impaired in several ABA-deficient and ABA-insensitive mutants. These results suggest that in addition to an ABA-independent pathway, the ABA-dependent pathway plays a positive role in the osmotic stress-responsive expression of DREB2A.

Abscisic Acid Regulates Early Seed Development in Arabidopsis by ABI5-Mediated Transcription of SHORT HYPOCOTYL UNDER BLUE1[C][W][OPEN

PubMed Central

Cheng, Zhi Juan; Zhao, Xiang Yu; Shao, Xing Xing; Wang, Fei; Zhou, Chao; Liu, Ying Gao; Zhang, Yan; Zhang, Xian Sheng

2014-01-01

Seed development includes an early stage of endosperm proliferation and a late stage of embryo growth at the expense of the endosperm in Arabidopsis thaliana. Abscisic acid (ABA) has known functions during late seed development, but its roles in early seed development remain elusive. In this study, we report that ABA-deficient mutants produced seeds with increased size, mass, and embryo cell number but delayed endosperm cellularization. ABSCISIC ACID DEFICIENT2 (ABA2) encodes a unique short-chain dehydrogenase/reductase that functions in ABA biosynthesis, and its expression pattern overlaps that of SHORT HYPOCOTYL UNDER BLUE1 (SHB1) during seed development. SHB1 RNA accumulation was significantly upregulated in the aba2-1 mutant and was downregulated by the application of exogenous ABA. Furthermore, RNA accumulation of the basic/region leucine zipper transcription factor ABSCISIC ACID-INSENSITIVE5 (ABI5), involved in ABA signaling, was decreased in aba2-1. Consistent with this, seed size was also increased in abi5. We further show that ABI5 directly binds to two discrete regions in the SHB1 promoter. Our results suggest that ABA negatively regulates SHB1 expression, at least in part, through the action of its downstream signaling component ABI5. Our findings provide insights into the molecular mechanisms by which ABA regulates early seed development. PMID:24619610

Isolation and functional characterization of CE1 binding proteins.

PubMed

Lee, Sun-ji; Park, Ji Hye; Lee, Mi Hun; Yu, Ji-hyun; Kim, Soo Young

2010-12-16

Abscisic acid (ABA) is a plant hormone that controls seed germination, protective responses to various abiotic stresses and seed maturation. The ABA-dependent processes entail changes in gene expression. Numerous genes are regulated by ABA, and promoter analyses of the genes revealed that cis-elements sharing the ACGTGGC consensus sequence are ubiquitous among ABA-regulated gene promoters. The importance of the core sequence, which is generally known as ABA response element (ABRE), has been demonstrated by various experiments, and its cognate transcription factors known as ABFs/AREBs have been identified. Although necessary, ABRE alone is not sufficient, and another cis-element known as "coupling element (CE)" is required for full range ABA-regulation of gene expression. Several CEs are known. However, despite their importance, the cognate transcription factors mediating ABA response via CEs have not been reported to date. Here, we report the isolation of transcription factors that bind one of the coupling elements, CE1. To isolate CE1 binding proteins, we carried out yeast one-hybrid screens. Reporter genes containing a trimer of the CE1 element were prepared and introduced into a yeast strain. The yeast was transformed with library DNA that represents RNA isolated from ABA-treated Arabidopsis seedlings. From the screen of 3.6 million yeast transformants, we isolated 78 positive clones. Analysis of the clones revealed that a group of AP2/ERF domain proteins binds the CE1 element. We investigated their expression patterns and analyzed their overexpression lines to investigate the in vivo functions of the CE element binding factors (CEBFs). Here, we show that one of the CEBFs, AtERF13, confers ABA hypersensitivity in Arabidopsis, whereas two other CEBFs enhance sugar sensitivity. Our results indicate that a group of AP2/ERF superfamily proteins interacts with CE1. Several CEBFs are known to mediate defense or abiotic stress response, but the physiological functions of other CEBFs remain to be determined. Our in vivo functional analysis of several CEBFs suggests that they are likely to be involved in ABA and/or sugar response. Together with previous results reported by others, our current data raise an interesting possibility that the coupling element CE1 may function not only as an ABRE but also as an element mediating biotic and abiotic stress responses.

Involvement of NADPH oxidase isoforms in the production of O2− manipulated by ABA in the senescing leaves of early-senescence-leaf (esl) mutant rice (Oryza sativa)

PubMed Central

Wang, Fubiao; Zhao, Qian; Liu, Jianchao; Cheng, Fangmin

2018-01-01

In this study, the differences in reactive oxygen species (ROS) generation and abscisic acid (ABA) accumulation in senescing leaves were investigated by early-senescence-leaf (esl) mutant and its wild type, to clarify the relationship among ABA levels, ROS generation, and NADPH oxidase (Nox) in senescing leaves of rice (Oryza sativa). The temporal expression levels of OsNox isoforms in senescing leaves and their expression patterns in response to ABA treatment were determined through quantitative real-time reverse transcription PCR (qRT-PCR). Results showed that the flag leaf of the esl mutant generated more O2- concentrations and accumulated higher ABA levels than the wild-type cultivar did in the grain-filling stage. Exogenous ABA treatment induced O2- generation; however, it was depressed by diphenyleneiodonium chloride (DPI) pretreatment in the detached leaf segments. This finding suggested the involvement of NADPH oxidase in ABA-induced O2- generation. The esl mutant exhibited significantly higher expression of OsNox2, OsNox5, OsNox6, and OsNox7 in the initial of grain-filling stage, followed by sharply decrease. The transcriptional levels of OsNox1, OsNox3, and OsFR07 in the flag leaf of the esl mutant were significantly lower than those in the wild-type cultivar. The expression levels of OsNox2, OsNox5, OsNox6, and OsNox7 were significantly enhanced by exogenous ABA treatments. The enhanced expression levels of OsNox2 and OsNox6 were dependent on the duration of ABA treatment. The inducible expression levels of OsNox5 and OsNox7 were dependent on ABA concentrations. By contrast, exogenous ABA treatment severely repressed the transcripts of OsNox1, OsNox3, and OsFR07 in the detached leaf segments. Therefore, OsNox2, OsNox5, OsNox6, and OsNox7 were probably involved in the ABA-induced O2- generation in the initial stage of leaf senescence. Subsequently, other oxidases activated in deteriorating cells were associated with ROS generation and accumulation in the senescing leaves of the esl mutant. Conversely, OsNox1, OsNox3, and OsFR07 were not associated with ABA-induced O2- generation during leaf senescence. PMID:29309410

Involvement of NADPH oxidase isoforms in the production of O2- manipulated by ABA in the senescing leaves of early-senescence-leaf (esl) mutant rice (Oryza sativa).

PubMed

Li, Zhaowei; Wang, Fubiao; Zhao, Qian; Liu, Jianchao; Cheng, Fangmin

2018-01-01

In this study, the differences in reactive oxygen species (ROS) generation and abscisic acid (ABA) accumulation in senescing leaves were investigated by early-senescence-leaf (esl) mutant and its wild type, to clarify the relationship among ABA levels, ROS generation, and NADPH oxidase (Nox) in senescing leaves of rice (Oryza sativa). The temporal expression levels of OsNox isoforms in senescing leaves and their expression patterns in response to ABA treatment were determined through quantitative real-time reverse transcription PCR (qRT-PCR). Results showed that the flag leaf of the esl mutant generated more O2- concentrations and accumulated higher ABA levels than the wild-type cultivar did in the grain-filling stage. Exogenous ABA treatment induced O2- generation; however, it was depressed by diphenyleneiodonium chloride (DPI) pretreatment in the detached leaf segments. This finding suggested the involvement of NADPH oxidase in ABA-induced O2- generation. The esl mutant exhibited significantly higher expression of OsNox2, OsNox5, OsNox6, and OsNox7 in the initial of grain-filling stage, followed by sharply decrease. The transcriptional levels of OsNox1, OsNox3, and OsFR07 in the flag leaf of the esl mutant were significantly lower than those in the wild-type cultivar. The expression levels of OsNox2, OsNox5, OsNox6, and OsNox7 were significantly enhanced by exogenous ABA treatments. The enhanced expression levels of OsNox2 and OsNox6 were dependent on the duration of ABA treatment. The inducible expression levels of OsNox5 and OsNox7 were dependent on ABA concentrations. By contrast, exogenous ABA treatment severely repressed the transcripts of OsNox1, OsNox3, and OsFR07 in the detached leaf segments. Therefore, OsNox2, OsNox5, OsNox6, and OsNox7 were probably involved in the ABA-induced O2- generation in the initial stage of leaf senescence. Subsequently, other oxidases activated in deteriorating cells were associated with ROS generation and accumulation in the senescing leaves of the esl mutant. Conversely, OsNox1, OsNox3, and OsFR07 were not associated with ABA-induced O2- generation during leaf senescence.

The SnRK2-APC/CTE regulatory module mediates the antagonistic action of gibberellic acid and abscisic acid pathways

PubMed Central

Lin, Qibing; Wu, Fuqing; Sheng, Peike; Zhang, Zhe; Zhang, Xin; Guo, Xiuping; Wang, Jiulin; Cheng, Zhijun; Wang, Jie; Wang, Haiyang; Wan, Jianmin

2015-01-01

Abscisic acid (ABA) and gibberellic acid (GA) antagonistically regulate many developmental processes and responses to biotic or abiotic stresses in higher plants. However, the molecular mechanism underlying this antagonism is still poorly understood. Here, we show that loss-of-function mutation in rice Tiller Enhancer (TE), an activator of the APC/CTE complex, causes hypersensitivity and hyposensitivity to ABA and GA, respectively. We find that TE physically interacts with ABA receptor OsPYL/RCARs and promotes their degradation by the proteasome. Genetic analysis also shows OsPYL/RCARs act downstream of TE in mediating ABA responses. Conversely, ABA inhibits APC/CTE activity by phosphorylating TE through activating the SNF1-related protein kinases (SnRK2s), which may interrupt the interaction between TE and OsPYL/RCARs and subsequently stabilize OsPYL/RCARs. In contrast, GA can reduce the level of SnRK2s and may promote APC/CTE-mediated degradation of OsPYL/RCARs. Thus, we propose that the SnRK2-APC/CTE regulatory module represents a regulatory hub underlying the antagonistic action of GA and ABA in plants. PMID:26272249

An Atypical Late Embryogenesis Abundant Protein OsLEA5 Plays a Positive Role in ABA-Induced Antioxidant Defense in Oryza sativa L.

PubMed

Huang, Liping; Zhang, MengYao; Jia, Jing; Zhao, Xixi; Huang, Xingxiu; Ji, E; Ni, Lan; Jiang, Mingyi

2018-05-01

OsLEA5 acts as a co-regulator of a transcriptional fact ZFP36 to enhance the expression and the activity of ascorbate peroxidase OsAPX1 to regulate seed germination in rice, but it it unknown whether OsLEA5 is also crucial in plant seedlings under stress conditions. To determine this, we generated OsLEA5 overexpression and knockdown rice plants. We found that overexpression of OsLEA5 in rice plants enhanced the tolerance to drought and salt stress; in contrast, an RNA interference (RNAi) mutant of OsLEA5 rice plants was more sensitive to drought and salinity. Further investigation found that various stimuli and ABA could induce OsLEA5 expression, and OsLEA5 acted downstream of ZFP36 to be involved in ABA-induced generation of hydrogen peroxide (H2O2), and the regulation of the expression and the activities of antioxidant defense enzymes in plants leaves, and OsLEA5 contributed to stabilize ZFP36. Additionally, OsLEA5 participates in the accumulation of ABA by up-regulating ABA biosynthesis genes and down-regulating ABA metabolism genes. Moreover, we found that two homologs of OsLEA5 (5C700, short for Os05g0526700; and 5C300, short for Os05g0584300) which were induced by ABA also interacted with ZFP36 separately; interestingly, the nuclear-located 5C700 could also act as a co-activator of ZFP36 to modulate OsAPX1, while 5C300 which was down-regulated by ABA induction acted as an ABA-induced inhibitor of ZFP36 to regulate OsAPX1. Hence, our conclusion is that OsLEA5 participates in the ABA-mediated antioxidant defense to function in drought and salt stress response in rice, and the 5C subgroup of LEAs contribute by acting as co-regulators of the transcription factor ZFP36.

Abscisic Acid Deficiency Antagonizes High-Temperature Inhibition of Disease Resistance through Enhancing Nuclear Accumulation of Resistance Proteins SNC1 and RPS4 in Arabidopsis[C][W

PubMed Central

Mang, Hyung-Gon; Qian, Weiqiang; Zhu, Ying; Qian, Jun; Kang, Hong-Gu; Klessig, Daniel F.; Hua, Jian

2012-01-01

Plant defense responses to pathogens are influenced by abiotic factors, including temperature. Elevated temperatures often inhibit the activities of disease resistance proteins and the defense responses they mediate. A mutant screen with an Arabidopsis thaliana temperature-sensitive autoimmune mutant bonzai1 revealed that the abscisic acid (ABA)–deficient mutant aba2 enhances resistance mediated by the resistance (R) gene SUPPRESSOR OF npr1-1 CONSTITUTIVE1 (SNC1) at high temperature. ABA deficiency promoted nuclear accumulation of SNC1, which was essential for it to function at low and high temperatures. Furthermore, the effect of ABA deficiency on SNC1 protein accumulation is independent of salicylic acid, whose effects are often antagonized by ABA. ABA deficiency also promotes the activity and nuclear localization of R protein RESISTANCE TO PSEUDOMONAS SYRINGAE4 at higher temperature, suggesting that the effect of ABA on R protein localization and nuclear activity is rather broad. By contrast, mutations that confer ABA insensitivity did not promote defense responses at high temperature, suggesting either tissue specificity of ABA signaling or a role of ABA in defense regulation independent of the core ABA signaling machinery. Taken together, this study reveals a new intersection between ABA and disease resistance through R protein localization and provides further evidence of antagonism between abiotic and biotic responses. PMID:22454454

WRKY transcription factors: key components in abscisic acid signalling.

PubMed

Rushton, Deena L; Tripathi, Prateek; Rabara, Roel C; Lin, Jun; Ringler, Patricia; Boken, Ashley K; Langum, Tanner J; Smidt, Lucas; Boomsma, Darius D; Emme, Nicholas J; Chen, Xianfeng; Finer, John J; Shen, Qingxi J; Rushton, Paul J

2012-01-01

WRKY transcription factors (TFs) are key regulators of many plant processes, including the responses to biotic and abiotic stresses, senescence, seed dormancy and seed germination. For over 15 years, limited evidence has been available suggesting that WRKY TFs may play roles in regulating plant responses to the phytohormone abscisic acid (ABA), notably some WRKY TFs are ABA-inducible repressors of seed germination. However, the roles of WRKY TFs in other aspects of ABA signalling, and the mechanisms involved, have remained unclear. Recent significant progress in ABA research has now placed specific WRKY TFs firmly in ABA-responsive signalling pathways, where they act at multiple levels. In Arabidopsis, WRKY TFs appear to act downstream of at least two ABA receptors: the cytoplasmic PYR/PYL/RCAR-protein phosphatase 2C-ABA complex and the chloroplast envelope-located ABAR-ABA complex. In vivo and in vitro promoter-binding studies show that the target genes for WRKY TFs that are involved in ABA signalling include well-known ABA-responsive genes such as ABF2, ABF4, ABI4, ABI5, MYB2, DREB1a, DREB2a and RAB18. Additional well-characterized stress-inducible genes such as RD29A and COR47 are also found in signalling pathways downstream of WRKY TFs. These new insights also reveal that some WRKY TFs are positive regulators of ABA-mediated stomatal closure and hence drought responses. Conversely, many WRKY TFs are negative regulators of seed germination, and controlling seed germination appears a common function of a subset of WRKY TFs in flowering plants. Taken together, these new data demonstrate that WRKY TFs are key nodes in ABA-responsive signalling networks. © 2011 The Authors. Plant Biotechnology Journal © 2011 Society for Experimental Biology, Association of Applied Biologists and Blackwell Publishing Ltd.

APETALA 2-domain-containing transcription factors: focusing on abscisic acid and gibberellins antagonism.

PubMed

Shu, Kai; Zhou, Wenguan; Yang, Wenyu

2018-02-01

The phytohormones abscisic acid (ABA) and gibberellin (GA) antagonistically mediate diverse plant developmental processes including seed dormancy and germination, root development, and flowering time control, and thus the optimal balance between ABA and GA is essential for plant growth and development. Although more than a half and one century have passed since the initial discoveries of ABA and GA, respectively, the precise mechanisms underlying ABA-GA antagonism still need further investigation. Emerging evidence indicates that two APETALA 2 (AP2)-domain-containing transcription factors (ATFs), ABI4 in Arabidopsis and OsAP2-39 in rice, play key roles in ABA and GA antagonism. These two transcription factors precisely regulate the transcription pattern of ABA and GA biosynthesis or inactivation genes, mediating ABA and GA levels. In this Viewpoint article, we try to shed light on the effects of ATFs on ABA-GA antagonism, and summarize the overlapping but distinct biological functions of these ATFs in the antagonism between ABA and GA. Finally, we strongly propose that further research is needed into the detailed roles of additional numerous ATFs in ABA and GA crosstalk, which will improve our understanding of the antagonism between these two phytohormones. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Arabidopsis YAK1 regulates abscisic acid response and drought resistance.

PubMed

Kim, Dongjin; Ntui, Valentine Otang; Xiong, Liming

2016-07-01

Abscisic acid (ABA) is an important phytohormone that controls several plant processes such as seed germination, seedling growth, and abiotic stress response. Here, we report that AtYak1 plays an important role in ABA signaling and postgermination growth in Arabidopsis. AtYak1 knockout mutant plants were hyposensitive to ABA inhibition of seed germination, cotyledon greening, seedling growth, and stomatal movement. atyak1-1 mutant plants display reduced drought stress resistance, as evidenced by water loss rate and survival rate. Molecular genetic analysis revealed that AtYak1 deficiency led to elevated expression of stomatal-related gene, MYB60, and down-regulation of several stress-responsive genes. Altogether, these results indicate that AtYak1 plays a role as a positive regulator in ABA-mediated drought response in Arabidopsis. © 2016 Federation of European Biochemical Societies.

LTP3 contributes to disease susceptibility in Arabidopsis by enhancing abscisic acid (ABA) biosynthesis.

PubMed

Gao, Shan; Guo, Wenya; Feng, Wen; Liu, Liang; Song, Xiaorui; Chen, Jian; Hou, Wei; Zhu, Hongxia; Tang, Saijun; Hu, Jian

2016-04-01

Several plant lipid transfer proteins (LTPs) act positively in plant disease resistance. Here, we show that LTP3 (At5g59320), a pathogen and abscisic acid (ABA)-induced gene, negatively regulates plant immunity in Arabidopsis. The overexpression of LTP3 (LTP3-OX) led to an enhanced susceptibility to virulent bacteria and compromised resistance to avirulent bacteria. On infection of LTP3-OX plants with Pseudomonas syringae pv. tomato, genes involved in ABA biosynthesis, NCED3 and AAO3, were highly induced, whereas salicylic acid (SA)-related genes, ICS1 and PR1, were down-regulated. Accordingly, in LTP3-OX plants, we observed increased ABA levels and decreased SA levels relative to the wild-type. We also showed that the LTP3 overexpression-mediated enhanced susceptibility was partially dependent on AAO3. Interestingly, loss of function of LTP3 (ltp3-1) did not affect ABA pathways, but resulted in PR1 gene induction and elevated SA levels, suggesting that LTP3 can negatively regulate SA in an ABA-independent manner. However, a double mutant consisting of ltp3-1 and silent LTP4 (ltp3/ltp4) showed reduced susceptibility to Pseudomonas and down-regulation of ABA biosynthesis genes, suggesting that LTP3 acts in a redundant manner with its closest homologue LTP4 by modulating the ABA pathway. Taken together, our data show that LTP3 is a novel negative regulator of plant immunity which acts through the manipulation of the ABA-SA balance. © 2015 BSPP and John Wiley & Sons Ltd.

Feedback regulation via AMPK and HIF-1 mediates ROS-dependent longevity in Caenorhabditis elegans

PubMed Central

Hwang, Ara B.; Ryu, Eun-A; Artan, Murat; Chang, Hsin-Wen; Kabir, Mohammad Humayun; Nam, Hyun-Jun; Lee, Dongyeop; Yang, Jae-Seong; Kim, Sanguk; Mair, William B.; Lee, Cheolju; Lee, Siu Sylvia; Lee, Seung-Jae

2014-01-01

Mild inhibition of mitochondrial respiration extends the lifespan of many species. In Caenorhabditis elegans, reactive oxygen species (ROS) promote longevity by activating hypoxia-inducible factor 1 (HIF-1) in response to reduced mitochondrial respiration. However, the physiological role and mechanism of ROS-induced longevity are poorly understood. Here, we show that a modest increase in ROS increases the immunity and lifespan of C. elegans through feedback regulation by HIF-1 and AMP-activated protein kinase (AMPK). We found that activation of AMPK as well as HIF-1 mediates the longevity response to ROS. We further showed that AMPK reduces internal levels of ROS, whereas HIF-1 amplifies the levels of internal ROS under conditions that increase ROS. Moreover, mitochondrial ROS increase resistance to various pathogenic bacteria, suggesting a possible association between immunity and long lifespan. Thus, AMPK and HIF-1 may control immunity and longevity tightly by acting as feedback regulators of ROS. PMID:25288734

Expression of the SIN3 homologue from banana, MaSIN3, suppresses ABA responses globally during plant growth in Arabidopsis.

PubMed

Luxmi, Raj; Garg, Rashmi; Srivastava, Sudhakar; Sane, Aniruddha P

2017-11-01

The SIN3 family of co-repressors is a family of highly conserved eukaryotic repressor proteins that regulates diverse functions in yeasts and animals but remains largely uncharacterized functionally even in plants like Arabidopsis. The sole SIN3 homologue in banana, MaSIN3, was identified as a 1408 amino acids, nuclear localized protein conserved to other SIN3s in the PAH, HID and HCR domains. Interestingly, MaSIN3 over-expression in Arabidopsis mimics a state of reduced ABA responses throughout plant development affecting growth processes such as germination, root growth, stomatal closure and water loss, flowering and senescence. The reduction in ABA responses is not due to reduced ABA levels but due to suppression of expression of several transcription factors mediating ABA responses. Transcript levels of negative regulators of germination (ABI3, ABI5, PIL5, RGL2 and RGL3) are reduced post-imbibition while those responsible for GA biosynthesis are up-regulated in transgenic MaSIN3 over-expressers. ABA-associated transcription factors are also down-regulated in response to ABA treatment. The HDAC inhibitors, SAHA and sodium butyrate, in combination with ABA differentially suppress germination in control and transgenic lines suggesting the recruitment by MaSIN3 of HDACs involved in suppression of ABA responses in different processes. The studies provide an insight into the ability of MaSIN3 to specifically affect a subset of developmental processes governed largely by ABA. Copyright © 2017 Elsevier B.V. All rights reserved.

Rice G-protein subunits qPE9-1 and RGB1 play distinct roles in abscisic acid responses and drought adaptation.

PubMed

Zhang, Dong-Ping; Zhou, Yong; Yin, Jian-Feng; Yan, Xue-Jiao; Lin, Sheng; Xu, Wei-Feng; Baluška, František; Wang, Yi-Ping; Xia, Yi-Ji; Liang, Guo-hua; Liang, Jian-Sheng

2015-10-01

Heterotrimeric GTP-binding protein (G-protein)-mediated abscisic acid (ABA) and drought-stress responses have been documented in numerous plant species. However, our understanding of the function of rice G-protein subunits in ABA signalling and drought tolerance is limited. In this study, the function of G-protein subunits in ABA response and drought resistance in rice plants was explored. It was found that the transcription level of qPE9-1 (rice Gγ subunit) gradually decreased with increasing ABA concentration and the lack of qPE9-1 showed an enhanced drought tolerance in rice plants. In contrast, mRNA levels of RGB1 (rice Gβ subunit) were significantly upregulated by ABA treatment and the lack of RGB1 led to reduced drought tolerance. Furthermore, the results suggested that qPE9-1 negatively regulates the ABA response by suppressing the expression of key transcription factors involved in ABA and stress responses, while RGB1 positively regulates ABA biosynthesis by upregulating NCED gene expression under both normal and drought stress conditions. Taken together, it is proposed that RGB1 is a positive regulator of the ABA response and drought adaption in rice plants, whereas qPE9-1 is modulated by RGB1 and functions as a negative regulator in the ABA-dependent drought-stress responses. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Ectopic expression of ABSCISIC ACID 2/GLUCOSE INSENSITIVE 1 in Arabidopsis promotes seed dormancy and stress tolerance.

PubMed

Lin, Pei-Chi; Hwang, San-Gwang; Endo, Akira; Okamoto, Masanori; Koshiba, Tomokazu; Cheng, Wan-Hsing

2007-02-01

Abscisic acid (ABA) is an important phytohormone that plays a critical role in seed development, dormancy, and stress tolerance. 9-cis-Epoxycarotenoid dioxygenase is the key enzyme controlling ABA biosynthesis and stress tolerance. In this study, we investigated the effect of ectopic expression of another ABA biosynthesis gene, ABA2 (or GLUCOSE INSENSITIVE 1 [GIN1]) encoding a short-chain dehydrogenase/reductase in Arabidopsis (Arabidopsis thaliana). We show that ABA2-overexpressing transgenic plants with elevated ABA levels exhibited seed germination delay and more tolerance to salinity than wild type when grown on agar plates and/or in soil. However, the germination delay was abolished in transgenic plants showing ABA levels over 2-fold higher than that of wild type grown on 250 mm NaCl. The data suggest that there are distinct mechanisms underlying ABA-mediated inhibition of seed germination under diverse stress. The ABA-deficient mutant aba2, with a shorter primary root, can be restored to normal root growth by exogenous application of ABA, whereas transgenic plants overexpressing ABA2 showed normal root growth. The data reflect that the basal levels of ABA are essential for maintaining normal primary root elongation. Furthermore, analysis of ABA2 promoter activity with ABA2::beta-glucuronidase transgenic plants revealed that the promoter activity was enhanced by multiple prolonged stresses, such as drought, salinity, cold, and flooding, but not by short-term stress treatments. Coincidently, prolonged drought stress treatment led to the up-regulation of ABA biosynthetic and sugar-related genes. Thus, the data support ABA2 as a late expression gene that might have a fine-tuning function in mediating ABA biosynthesis through primary metabolic changes in response to stress.

Over-expression of TaMYB33 encoding a novel wheat MYB transcription factor increases salt and drought tolerance in Arabidopsis.

PubMed

Qin, Yuxiang; Wang, Mengcheng; Tian, Yanchen; He, Wenxing; Han, Lu; Xia, Guangmin

2012-06-01

Salt and drought stresses often adversely affect plant growth and productivity, MYB transcription factors have been shown to participate in the response to these stresses. Here we identified a new R2R3-type MYB transcription factor gene TaMYB33 from wheat (Triticum aestivum). TaMYB33 was induced by NaCl, PEG and ABA treatments, and its promoter sequence contains putative ABRE, MYB and other abiotic stress related cis-elements. Ectopic over-expression of TaMYB33 in Arabidopsis thaliana remarkably enhanced its tolerance to drought and NaCl stresses, but not to LiCl and KCl treatments. The expressions of AtP5CS and AtZAT12 which mirror the activities of proline and ascorbate peroxidase synthesis respectively were induced in TaMYB33 over-expression lines, indicating TaMYB33 promotes the ability for osmotic pressure balance-reconstruction and reactive oxidative species (ROS) scavenging. The up-regulation of AtAAO3 along with down-regulation of AtABF3, AtABI1 in TaMYB33 over-expression lines indicated that ABA synthesis was elevated while its signaling was restricted. These results suggest that TaMYB33 enhances salt and drought tolerance partially through superior ability for osmotic balance reconstruction and ROS detoxification.

Antagonism between salicylic and abscisic acid reflects early host-pathogen conflict and moulds plant defence responses.

PubMed

de Torres Zabala, Marta; Bennett, Mark H; Truman, William H; Grant, Murray R

2009-08-01

The importance of phytohormone balance is increasingly recognized as central to the outcome of plant-pathogen interactions. Recently it has been demonstrated that abscisic acid signalling pathways are utilized by the bacterial phytopathogen Pseudomonas syringae to promote pathogenesis. In this study, we examined the dynamics, inter-relationship and impact of three key acidic phytohormones, salicylic acid, abscisic acid and jasmonic acid, and the bacterial virulence factor, coronatine, during progression of P. syringae infection of Arabidopsis thaliana. We show that levels of SA and ABA, but not JA, appear to play important early roles in determining the outcome of the infection process. SA is required in order to mount a full innate immune responses, while bacterial effectors act rapidly to activate ABA biosynthesis. ABA suppresses inducible innate immune responses by down-regulating SA biosynthesis and SA-mediated defences. Mutant analyses indicated that endogenous ABA levels represent an important reservoir that is necessary for effector suppression of plant-inducible innate defence responses and SA synthesis prior to subsequent pathogen-induced increases in ABA. Enhanced susceptibility due to loss of SA-mediated basal resistance is epistatically dominant over acquired resistance due to ABA deficiency, although ABA also contributes to symptom development. We conclude that pathogen-modulated ABA signalling rapidly antagonizes SA-mediated defences. We predict that hormonal perturbations, either induced or as a result of environmental stress, have a marked impact on pathological outcomes, and we provide a mechanistic basis for understanding priming events in plant defence.

Regulation of Wheat Seed Dormancy by After-Ripening Is Mediated by Specific Transcriptional Switches That Induce Changes in Seed Hormone Metabolism and Signaling

PubMed Central

Kanno, Yuri; Jordan, Mark C.; Kamiya, Yuji; Seo, Mitsunori; Ayele, Belay T.

2013-01-01

Treatments that promote dormancy release are often correlated with changes in seed hormone content and/or sensitivity. To understand the molecular mechanisms underlying the role of after-ripening (seed dry storage) in triggering hormone related changes and dormancy decay in wheat (Triticum aestivum), temporal expression patterns of genes related to abscisic acid (ABA), gibberellin (GA), jasmonate and indole acetic acid (IAA) metabolism and signaling, and levels of the respective hormones were examined in dormant and after-ripened seeds in both dry and imbibed states. After-ripening mediated developmental switch from dormancy to germination appears to be associated with declines in seed sensitivity to ABA and IAA, which are mediated by transcriptional repressions of PROTEIN PHOSPHATASE 2C, SNF1-RELATED PROTEIN KINASE2, ABA INSENSITIVE5 and LIPID PHOSPHATE PHOSPHTASE2, and AUXIN RESPONSE FACTOR and RELATED TO UBIQUITIN1 genes. Transcriptomic analysis of wheat seed responsiveness to ABA suggests that ABA inhibits the germination of wheat seeds partly by repressing the transcription of genes related to chromatin assembly and cell wall modification, and activating that of GA catabolic genes. After-ripening induced seed dormancy decay in wheat is also associated with the modulation of seed IAA and jasmonate contents. Transcriptional control of members of the ALLENE OXIDE SYNTHASE, 3-KETOACYL COENZYME A THIOLASE, LIPOXYGENASE and 12-OXOPHYTODIENOATE REDUCTASE gene families appears to regulate seed jasmonate levels. Changes in the expression of GA biosynthesis genes, GA 20-OXIDASE and GA 3-OXIDASE, in response to after-ripening implicate this hormone in enhancing dormancy release and germination. These findings have important implications in the dissection of molecular mechanisms underlying regulation of seed dormancy in cereals. PMID:23437172

Functional roles of the pepper RING finger protein gene, CaRING1, in abscisic acid signaling and dehydration tolerance.

PubMed

Lim, Chae Woo; Hwang, Byung Kook; Lee, Sung Chul

2015-09-01

Plants are constantly exposed to a variety of biotic and abiotic stresses, which include pathogens and conditions of high salinity, low temperature, and drought. Abscisic acid (ABA) is a major plant hormone involved in signal transduction pathways that mediate the defense response of plants to abiotic stress. Previously, we isolated Ring finger protein gene (CaRING1) from pepper (Capsicum annuum), which is associated with resistance to bacterial pathogens, accompanied by hypersensitive cell death. Here, we report a new function of the CaRING1 gene product in the ABA-mediated defense responses of plants to dehydration stress. The expression of the CaRING1 gene was induced in pepper leaves treated with ABA or exposed to dehydration or NaCl. Virus-induced gene silencing of CaRING1 in pepper plants exhibited low degree of ABA-induced stomatal closure and high levels of transpirational water loss in dehydrated leaves. These led to be more vulnerable to dehydration stress in CaRING1-silenced pepper than in the control pepper, accompanied by reduction of ABA-regulated gene expression and low accumulation of ABA and H2O2. In contrast, CaRING1-overexpressing transgenic plants showed enhanced sensitivity to ABA during the seedling growth and establishment. These plants were also more tolerant to dehydration stress than the wild-type plants because of high ABA accumulation, enhanced stomatal closure and increased expression of stress-responsive genes. Together, these results suggest that the CaRING1 acts as positive factor for dehydration tolerance in Arabidopsis by modulating ABA biosynthesis and ABA-mediated stomatal closing and gene expression.

Abscisic acid regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin.

PubMed

Rowe, James H; Topping, Jennifer F; Liu, Junli; Lindsey, Keith

2016-07-01

Understanding the mechanisms regulating root development under drought conditions is an important question for plant biology and world agriculture. We examine the effect of osmotic stress on abscisic acid (ABA), cytokinin and ethylene responses and how they mediate auxin transport, distribution and root growth through effects on PIN proteins. We integrate experimental data to construct hormonal crosstalk networks to formulate a systems view of root growth regulation by multiple hormones. Experimental analysis shows: that ABA-dependent and ABA-independent stress responses increase under osmotic stress, but cytokinin responses are only slightly reduced; inhibition of root growth under osmotic stress does not require ethylene signalling, but auxin can rescue root growth and meristem size; osmotic stress modulates auxin transporter levels and localization, reducing root auxin concentrations; PIN1 levels are reduced under stress in an ABA-dependent manner, overriding ethylene effects; and the interplay among ABA, ethylene, cytokinin and auxin is tissue-specific, as evidenced by differential responses of PIN1 and PIN2 to osmotic stress. Combining experimental analysis with network construction reveals that ABA regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Identification and characterization of cis-acting elements involved in the regulation of ABA- and/or GA-mediated LuPLR1 gene expression and lignan biosynthesis in flax (Linum usitatissimum L.) cell cultures.

PubMed

Corbin, Cyrielle; Renouard, Sullivan; Lopez, Tatiana; Lamblin, Frédéric; Lainé, Eric; Hano, Christophe

2013-03-15

Pinoresinol lariciresinol reductase 1, encoded by the LuPLR1 gene in flax (Linum usitatissimum L.), is responsible for the biosynthesis of (+)-secoisolariciresinol, a cancer chemopreventive phytoestrogenic lignan accumulated in high amount in the hull of flaxseed. Our recent studies have demonstrated a key role of abscisic acid (ABA) in the regulation of LuPLR1 gene expression and thus of the (+)-secoisolariciresinol synthesis during the flax seedcoat development. It is well accepted that gibberellins (GA) and ABA play antagonistic roles in the regulation of numerous developmental processes; therefore it is of interest to clarify their respective effects on lignan biosynthesis. Herein, using flax cell suspension cultures, we demonstrate that LuPLR1 gene expression and (+)-secoisolariciresinol synthesis are up-regulated by ABA and down-regulated by GA. The LuPLR1 gene promoter analysis and mutation experiments allow us to identify and characterize two important cis-acting sequences (ABRE and MYB2) required for these regulations. These results imply that a cross-talk between ABA and GA signaling orchestrated by transcription factors is involved in the regulation of lignan biosynthesis. This is particularly evidenced in the case of the ABRE cis-regulatory sequence of LuPLR1 gene promoter that appears to be a common target sequence of GA and ABA signals. Copyright © 2012 Elsevier GmbH. All rights reserved.

Reciprocal Regulation of Reactive Oxygen Species and Phospho-CREB Regulates Voltage Gated Calcium Channel Expression during Mycobacterium tuberculosis Infection

PubMed Central

Selvakumar, Arti; Antony, Cecil; Singhal, Jhalak; Tiwari, Brijendra K.; Singh, Yogendra; Natarajan, Krishnamurthy

2014-01-01

Our previous work has demonstrated the roles played by L-type Voltage Gated Calcium Channels (VGCC) in regulating Mycobacterium tuberculosis (M. tb) survival and pathogenesis. Here we decipher mechanisms and pathways engaged by the pathogen to regulate VGCC expression in macrophages. We show that M. tb and its antigen Rv3416 use phospho-CREB (pCREB), Reactive Oxygen Species (ROS), Protein Kinase C (PKC) and Mitogen Activated Protein Kinase (MAPK) to modulate VGCC expression in macrophages. siRNA mediated knockdown of MyD88, IRAK1, IRAK2 or TRAF6 significantly inhibited antigen mediated VGCC expression. Inhibiting Protein Kinase C (PKC) or MEK-ERK1/2 further increased VGCC expression. Interestingly, inhibiting intracellular calcium release upregulated antigen mediated VGCC expression, while inhibiting extracellular calcium influx had no significant effect. siRNA mediated knockdown of transcription factors c-Jun, SOX5 and CREB significantly inhibited Rv3416 mediated VGCC expression. A dynamic reciprocal cross-regulation between ROS and pCREB was observed that in turn governed VGCC expression with ROS playing a limiting role in the process. Further dissection of the mechanisms such as the interplay between ROS and pCREB would improve our understanding of the regulation of VGCC expression during M. tb infection. PMID:24797940

Abscisic Acid (ABA) Regulation of Arabidopsis SR Protein Gene Expression

PubMed Central

Cruz, Tiago M. D.; Carvalho, Raquel F.; Richardson, Dale N.; Duque, Paula

2014-01-01

Serine/arginine-rich (SR) proteins are major modulators of alternative splicing, a key generator of proteomic diversity and flexible means of regulating gene expression likely to be crucial in plant environmental responses. Indeed, mounting evidence implicates splicing factors in signal transduction of the abscisic acid (ABA) phytohormone, which plays pivotal roles in the response to various abiotic stresses. Using real-time RT-qPCR, we analyzed total steady-state transcript levels of the 18 SR and two SR-like genes from Arabidopsis thaliana in seedlings treated with ABA and in genetic backgrounds with altered expression of the ABA-biosynthesis ABA2 and the ABA-signaling ABI1 and ABI4 genes. We also searched for ABA-responsive cis elements in the upstream regions of the 20 genes. We found that members of the plant-specific SC35-Like (SCL) Arabidopsis SR protein subfamily are distinctively responsive to exogenous ABA, while the expression of seven SR and SR-related genes is affected by alterations in key components of the ABA pathway. Finally, despite pervasiveness of established ABA-responsive promoter elements in Arabidopsis SR and SR-like genes, their expression is likely governed by additional, yet unidentified cis-acting elements. Overall, this study pinpoints SR34, SR34b, SCL30a, SCL28, SCL33, RS40, SR45 and SR45a as promising candidates for involvement in ABA-mediated stress responses. PMID:25268622

An Apple Protein Kinase MdSnRK1.1 Interacts with MdCAIP1 to Regulate ABA Sensitivity.

PubMed

Liu, Xiao-Juan; Liu, Xin; An, Xiu-Hong; Han, Peng-Liang; You, Chun-Xiang; Hao, Yu-Jin

2017-10-01

ABA is a crucial phytohormone for development and stress responses in plants. Snf1-related protein kinase 1.1 (SnRK1.1) is involved in the ABA response. However, the molecular mechanism underlying the SnRK1.1 response to ABA is largely unknown. Here, it was found that overexpression of the apple MdSnRK1.1 gene enhanced ABA sensitivity in both transgenic apple calli and Arabidopsis seedlings. Subsequently, a yeast two-hybrid screen demonstrated that MdCAIP1 (C2-domain ABA Insensitive Protein1) interacted with MdSnRK1.1. Their interaction was further confirmed by pull-down and co-immunoprecipitation assays. Expression of the MdCAIP1 gene was positively induced by ABA. Its overexpression enhanced ABA sensitivity in transgenic apple calli. Furthermore, it was found that MdSnRK1.1 phosphorylated the MdCAIP1 protein in vivo and promoted its degradation in vitro and in vivo. As a result, MdSnRK1.1 inhibited MdCAIP1-mediated ABA sensitivity, and MdCAIP1 partially reduced MdSnRK1.1-mediated ABA sensitivity. Our findings indicate that MdSnRK1.1 plays an important role in the ABA response, partially by controlling the stability of the MdCAIP1 protein. © The Author 2017. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Inoculation with Bacillus subtilis and Azospirillum brasilense produces abscisic acid that reduces IRT1-mediated cadmium uptake of roots.

PubMed

Xu, Qianru; Pan, Wei; Zhang, Ranran; Lu, Qi; Xue, Wanlei; Wu, Cainan; Song, Bixiu; Du, Shaoting

2018-05-08

Cadmium (Cd) contamination of agricultural soils represents a serious risk to crop safety. A new strategy using abscisic acid (ABA)-generating bacteria, Bacillus subtilis or Azospirillum brasilense, was developed to reduce the Cd accumulation in plants grown in Cd-contaminated soil. Inoculation with either bacterium resulted in a pronounced increase in the ABA level in wild-type Arabidopsis Col-0 plants, accompanied by a decrease in Cd levels in plant tissues, which mitigated the Cd toxicity. As a consequence, the growth of plants exposed to Cd was improved. Nevertheless, B. subtilis and A. brasilense inoculation had little effect on Cd levels and toxicity in the ABA-insensitive mutant snrk 2.2/2.3, indicating that the action of ABA is required for these bacteria to reduce Cd accumulation in plants. Furthermore, inoculation with either B. subtilis or A. brasilense down-regulated the expression of IRT1 (IRON-REGULATED TRANSPORTER 1) in the roots of wild-type plants and had little effect on Cd levels in the IRT1-knockout mutants irt1-1 and irt1-2. In summary, we conclude that B. subtilis and A. brasilense can reduce Cd levels in plants via an IRT1-dependent ABA-mediated mechanism.

The critical role of catalase in prooxidant and antioxidant function of p53

PubMed Central

Kang, M Y; Kim, H-B; Piao, C; Lee, K H; Hyun, J W; Chang, I-Y; You, H J

2013-01-01

The tumor suppressor p53 is an important regulator of intracellular reactive oxygen species (ROS) levels, although downstream mediators of p53 remain to be elucidated. Here, we show that p53 and its downstream targets, p53-inducible ribonucleotide reductase (p53R2) and p53-inducible gene 3 (PIG3), physically and functionally interact with catalase for efficient regulation of intracellular ROS, depending on stress intensity. Under physiological conditions, the antioxidant functions of p53 are mediated by p53R2, which maintains increased catalase activity and thereby protects against endogenous ROS. After genotoxic stress, high levels of p53 and PIG3 cooperate to inhibit catalase activity, leading to a shift in the oxidant/antioxidant balance toward an oxidative status, which could augment apoptotic cell death. These results highlight the essential role of catalase in p53-mediated ROS regulation and suggest that the p53/p53R2–catalase and p53/PIG3–catalase pathways are critically involved in intracellular ROS regulation under physiological conditions and during the response to DNA damage, respectively. PMID:22918438

Calcium-calmodulin is required for abscisic acid-induced antioxidant defense and functions both upstream and downstream of H2O2 production in leaves of maize (Zea mays) plants.

PubMed

Hu, Xiuli; Jiang, Mingyi; Zhang, Jianhua; Zhang, Aying; Lin, Fan; Tan, Mingpu

2007-01-01

* Using pharmacological and biochemical approaches, the role of calmodulin (CaM) and the relationship between CaM and hydrogen peroxide (H(2)O(2)) in abscisic acid (ABA)-induced antioxidant defense in leaves of maize (Zea mays) plants were investigated. * Treatment with ABA or H(2)O(2) led to significant increases in the concentration of cytosolic Ca(2+) in the protoplasts of mesophyll cells and in the expression of the calmodulin 1 (CaM1) gene and the content of CaM in leaves of maize plants, and enhanced the expression of the antioxidant genes superoxide dismutase 4 (SOD4), cytosolic ascorbate peroxidase (cAPX), and glutathione reductase 1 (GR1) and the activities of the chloroplastic and cytosolic antioxidant enzymes. The up-regulation of the antioxidant enzymes was almost completely blocked by pretreatments with two CaM antagonists. * Pretreatments with CaM antagonists almost completely inhibited ABA-induced H(2)O(2) production throughout ABA treatment, but pretreatment with an inhibitor or scavenger of reactive oxygen species (ROS) did not affect the initial increase in the contents of CaM induced by ABA. * Our results suggest that Ca(2+)-CaM is involved in ABA-induced antioxidant defense, and that cross-talk between Ca(2+)-CaM and H(2)O(2) plays a pivotal role in ABA signaling.

Control of seed dormancy and germination by DOG1-AHG1 PP2C phosphatase complex via binding to heme.

PubMed

Nishimura, Noriyuki; Tsuchiya, Wataru; Moresco, James J; Hayashi, Yuki; Satoh, Kouji; Kaiwa, Nahomi; Irisa, Tomoko; Kinoshita, Toshinori; Schroeder, Julian I; Yates, John R; Hirayama, Takashi; Yamazaki, Toshimasa

2018-06-06

Abscisic acid (ABA) regulates abiotic stress and developmental responses including regulation of seed dormancy to prevent seeds from germinating under unfavorable environmental conditions. ABA HYPERSENSITIVE GERMINATION1 (AHG1) encoding a type 2C protein phosphatase (PP2C) is a central negative regulator of ABA response in germination; however, the molecular function and regulation of AHG1 remain elusive. Here we report that AHG1 interacts with DELAY OF GERMINATION1 (DOG1), which is a pivotal positive regulator in seed dormancy. DOG1 acts upstream of AHG1 and impairs the PP2C activity of AHG1 in vitro. Furthermore, DOG1 has the ability to bind heme. Binding of DOG1 to AHG1 and heme are independent processes, but both are essential for DOG1 function in vivo. Our study demonstrates that AHG1 and DOG1 constitute an important regulatory system for seed dormancy and germination by integrating multiple environmental signals, in parallel with the PYL/RCAR ABA receptor-mediated regulatory system.

PacCYP707A2 negatively regulates cherry fruit ripening while PacCYP707A1 mediates drought tolerance.

PubMed

Li, Qian; Chen, Pei; Dai, Shengjie; Sun, Yufei; Yuan, Bing; Kai, Wenbin; Pei, Yuelin; He, Suihuan; Liang, Bin; Zhang, Yushu; Leng, Ping

2015-07-01

Sweet cherry is a non-climacteric fruit and its ripening is regulated by abscisic acid (ABA) during fruit development. In this study, four cDNAs (PacCYP707A1-4) encoding 8'-hydroxylase, a key enzyme in the oxidative catabolism of ABA, were identified in sweet cherry fruits using tobacco rattle virus-induced gene silencing (VIGS) and particle bombardment approaches. Quantitative real-time PCR confirmed significant down-regulation of target gene transcripts in VIGS-treated cherry fruits. In PacCYP707A2-RNAi-treated fruits, ripening and fruit colouring were promoted relative to control fruits, and both ABA accumulation and PacNCED1 transcript levels were up-regulated by 140%. Silencing of PacCYP707A2 by VIGS significantly altered the transcripts of both ABA-responsive and ripening-related genes, including the ABA metabolism-associated genes NCED and CYP707A, the anthocyanin synthesis genes PacCHS, PacCHI, PacF3H, PacDFR, PacANS, and PacUFGT, the ethylene biosynthesis gene PacACO1, and the transcription factor PacMYBA. The promoter of PacMYBA responded more strongly to PacCYP707A2-RNAi-treated fruits than to PacCYP707A1-RNAi-treated fruits. By contrast, silencing of PacCYP707A1 stimulated a slight increase in fruit colouring and enhanced resistance to dehydration stress compared with control fruits. These results suggest that PacCYP707A2 is a key regulator of ABA catabolism that functions as a negative regulator of fruit ripening, while PacCYP707A1 regulates ABA content in response to dehydration during fruit development. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

PacCYP707A2 negatively regulates cherry fruit ripening while PacCYP707A1 mediates drought tolerance

PubMed Central

Li, Qian; Chen, Pei; Dai, Shengjie; Sun, Yufei; Yuan, Bing; Kai, Wenbin; Pei, Yuelin; He, Suihuan; Liang, Bin; Zhang, Yushu; Leng, Ping

2015-01-01

Sweet cherry is a non-climacteric fruit and its ripening is regulated by abscisic acid (ABA) during fruit development. In this study, four cDNAs (PacCYP707A1–4) encoding 8′-hydroxylase, a key enzyme in the oxidative catabolism of ABA, were identified in sweet cherry fruits using tobacco rattle virus-induced gene silencing (VIGS) and particle bombardment approaches. Quantitative real-time PCR confirmed significant down-regulation of target gene transcripts in VIGS-treated cherry fruits. In PacCYP707A2-RNAi-treated fruits, ripening and fruit colouring were promoted relative to control fruits, and both ABA accumulation and PacNCED1 transcript levels were up-regulated by 140%. Silencing of PacCYP707A2 by VIGS significantly altered the transcripts of both ABA-responsive and ripening-related genes, including the ABA metabolism-associated genes NCED and CYP707A, the anthocyanin synthesis genes PacCHS, PacCHI, PacF3H, PacDFR, PacANS, and PacUFGT, the ethylene biosynthesis gene PacACO1, and the transcription factor PacMYBA. The promoter of PacMYBA responded more strongly to PacCYP707A2-RNAi-treated fruits than to PacCYP707A1-RNAi-treated fruits. By contrast, silencing of PacCYP707A1 stimulated a slight increase in fruit colouring and enhanced resistance to dehydration stress compared with control fruits. These results suggest that PacCYP707A2 is a key regulator of ABA catabolism that functions as a negative regulator of fruit ripening, while PacCYP707A1 regulates ABA content in response to dehydration during fruit development. PMID:25956880

FRET-based reporters for the direct visualization of abscisic acid concentration changes and distribution in Arabidopsis

PubMed Central

Waadt, Rainer; Hitomi, Kenichi; Nishimura, Noriyuki; Hitomi, Chiharu; Adams, Stephen R; Getzoff, Elizabeth D; Schroeder, Julian I

2014-01-01

Abscisic acid (ABA) is a plant hormone that regulates plant growth and development and mediates abiotic stress responses. Direct cellular monitoring of dynamic ABA concentration changes in response to environmental cues is essential for understanding ABA action. We have developed ABAleons: ABA-specific optogenetic reporters that instantaneously convert the phytohormone-triggered interaction of ABA receptors with PP2C-type phosphatases to send a fluorescence resonance energy transfer (FRET) signal in response to ABA. We report the design, engineering and use of ABAleons with ABA affinities in the range of 100–600 nM to map ABA concentration changes in plant tissues with spatial and temporal resolution. High ABAleon expression can partially repress Arabidopsis ABA responses. ABAleons report ABA concentration differences in distinct cell types, ABA concentration increases in response to low humidity and NaCl in guard cells and to NaCl and osmotic stress in roots and ABA transport from the hypocotyl to the shoot and root. DOI: http://dx.doi.org/10.7554/eLife.01739.001 PMID:24737861

Abscisic acid activates a Ca2+-calmodulin-stimulated protein kinase involved in antioxidant defense in maize leaves.

PubMed

Xu, Shucheng

2010-09-01

The role of a calcium-dependent and calmodulin (CaM)-stimulated protein kinase in abscisic acid (ABA)-induced antioxidant defense was determined in leaves of maize (Zea mays). In-gel kinase assays showed that treatments with ABA or H(2)O(2) induced the activation of a 49-kDa protein kinase and a 52-kDa protein kinase significantly. Furthermore, we showed that the 52-kDa protein kinase has the characteristics of CaM-stimulating activity and is sensitive to calcium-CaM-dependent protein kinase II (CaMK II) inhibitor KN-93 or CaM antagonist W-7. Treatments with ABA or H(2)O(2) not only induced the activation of the 52-kDa protein kinase, but also enhanced the total activities of the antioxidant enzymes, including catalase, ascorbate peroxidase, glutathione reductase, and superoxide dismutase. Such enhancements were blocked by pretreatment with a CaMK inhibitor and a reactive oxygen species (ROS) inhibitor or scavenger. Pretreatment with the CaMK inhibitor also substantially arrested the ABA-induced H(2)O(2) production. Kinase activity enhancements induced by ABA were attenuated by pretreatment with an ROS inhibitor or scavenger. These results suggest that the 52-kDa CaMK is involved in ABA-induced antioxidant defense and that cross-talk between CaMK and H(2)O(2) plays a pivotal role in ABA signaling. We infer that CaMK acts both upstream and downstream of H(2)O(2), but mainly acts between ABA and H(2)O(2) in ABA-induced antioxidant-defensive signaling.

ABI4 Regulates Primary Seed Dormancy by Regulating the Biogenesis of Abscisic Acid and Gibberellins in Arabidopsis

PubMed Central

Shu, Kai; Zhang, Huawei; Wang, Shengfu; Chen, Mingluan; Wu, Yaorong; Tang, Sanyuan; Liu, Chunyan; Feng, Yuqi; Cao, Xiaofeng; Xie, Qi

2013-01-01

Seed dormancy is an important economic trait for agricultural production. Abscisic acid (ABA) and Gibberellins (GA) are the primary factors that regulate the transition from dormancy to germination, and they regulate this process antagonistically. The detailed regulatory mechanism involving crosstalk between ABA and GA, which underlies seed dormancy, requires further elucidation. Here, we report that ABI4 positively regulates primary seed dormancy, while negatively regulating cotyledon greening, by mediating the biogenesis of ABA and GA. Seeds of the Arabidopsis abi4 mutant that were subjected to short-term storage (one or two weeks) germinated significantly more quickly than Wild-Type (WT), and abi4 cotyledons greened markedly more quickly than WT, while the rates of germination and greening were comparable when the seeds were subjected to longer-term storage (six months). The ABA content of dry abi4 seeds was remarkably lower than that of WT, but the amounts were comparable after stratification. Consistently, the GA level of abi4 seeds was increased compared to WT. Further analysis showed that abi4 was resistant to treatment with paclobutrazol (PAC), a GA biosynthesis inhibitor, during germination, while OE-ABI4 was sensitive to PAC, and exogenous GA rescued the delayed germination phenotype of OE-ABI4. Analysis by qRT-PCR showed that the expression of genes involved in ABA and GA metabolism in dry and germinating seeds corresponded to hormonal measurements. Moreover, chromatin immunoprecipitation qPCR (ChIP-qPCR) and transient expression analysis showed that ABI4 repressed CYP707A1 and CYP707A2 expression by directly binding to those promoters, and the ABI4 binding elements are essential for this repression. Accordingly, further genetic analysis showed that abi4 recovered the delayed germination phenotype of cyp707a1 and cyp707a2 and further, rescued the non-germinating phenotype of ga1-t. Taken together, this study suggests that ABI4 is a key factor that regulates primary seed dormancy by mediating the balance between ABA and GA biogenesis. PMID:23818868

Ethylene-induced inhibition of root growth requires abscisic acid function in rice (Oryza sativa L.) seedlings.

PubMed

Ma, Biao; Yin, Cui-Cui; He, Si-Jie; Lu, Xiang; Zhang, Wan-Ke; Lu, Tie-Gang; Chen, Shou-Yi; Zhang, Jin-Song

2014-10-01

Ethylene and abscisic acid (ABA) have a complicated interplay in many developmental processes. Their interaction in rice is largely unclear. Here, we characterized a rice ethylene-response mutant mhz4, which exhibited reduced ethylene-response in roots but enhanced ethylene-response in coleoptiles of etiolated seedlings. MHZ4 was identified through map-based cloning and encoded a chloroplast-localized membrane protein homologous to Arabidopsis thaliana (Arabidopsis) ABA4, which is responsible for a branch of ABA biosynthesis. MHZ4 mutation reduced ABA level, but promoted ethylene production. Ethylene induced MHZ4 expression and promoted ABA accumulation in roots. MHZ4 overexpression resulted in enhanced and reduced ethylene response in roots and coleoptiles, respectively. In root, MHZ4-dependent ABA pathway acts at or downstream of ethylene receptors and positively regulates root ethylene response. This ethylene-ABA interaction mode is different from that reported in Arabidopsis, where ethylene-mediated root inhibition is independent of ABA function. In coleoptile, MHZ4-dependent ABA pathway acts at or upstream of OsEIN2 to negatively regulate coleoptile ethylene response, possibly by affecting OsEIN2 expression. At mature stage, mhz4 mutation affects branching and adventitious root formation on stem nodes of higher positions, as well as yield-related traits. Together, our findings reveal a novel mode of interplay between ethylene and ABA in control of rice growth and development.

Ethylene-Induced Inhibition of Root Growth Requires Abscisic Acid Function in Rice (Oryza sativa L.) Seedlings

PubMed Central

He, Si-Jie; Lu, Xiang; Zhang, Wan-Ke; Lu, Tie-Gang; Chen, Shou-Yi; Zhang, Jin-Song

2014-01-01

Ethylene and abscisic acid (ABA) have a complicated interplay in many developmental processes. Their interaction in rice is largely unclear. Here, we characterized a rice ethylene-response mutant mhz4, which exhibited reduced ethylene-response in roots but enhanced ethylene-response in coleoptiles of etiolated seedlings. MHZ4 was identified through map-based cloning and encoded a chloroplast-localized membrane protein homologous to Arabidopsis thaliana (Arabidopsis) ABA4, which is responsible for a branch of ABA biosynthesis. MHZ4 mutation reduced ABA level, but promoted ethylene production. Ethylene induced MHZ4 expression and promoted ABA accumulation in roots. MHZ4 overexpression resulted in enhanced and reduced ethylene response in roots and coleoptiles, respectively. In root, MHZ4-dependent ABA pathway acts at or downstream of ethylene receptors and positively regulates root ethylene response. This ethylene-ABA interaction mode is different from that reported in Arabidopsis, where ethylene-mediated root inhibition is independent of ABA function. In coleoptile, MHZ4-dependent ABA pathway acts at or upstream of OsEIN2 to negatively regulate coleoptile ethylene response, possibly by affecting OsEIN2 expression. At mature stage, mhz4 mutation affects branching and adventitious root formation on stem nodes of higher positions, as well as yield-related traits. Together, our findings reveal a novel mode of interplay between ethylene and ABA in control of rice growth and development. PMID:25330236

Modulation of organic acids and sugar content in tomato fruits by an abscisic acid-regulated transcription factor.

PubMed

Bastías, Adriana; López-Climent, María; Valcárcel, Mercedes; Rosello, Salvador; Gómez-Cadenas, Aurelio; Casaretto, José A

2011-03-01

Growing evidence suggests that the phytohormone abscisic acid (ABA) plays a role in fruit development. ABA signaling components of developmental programs and responses to stress conditions include the group of basic leucine zipper transcriptional activators known as ABA-response element binding factors (AREBs/ABFs). AREB transcription factors mediate ABA-regulated gene expression involved in desiccation tolerance and are expressed mainly in seeds and in vegetative tissues under stress; however, they are also expressed in some fruits such as tomato. In order to get an insight into the role of ABA signaling in fruit development, the expression of two AREB-like factors were investigated during different developmental stages. In addition, tomato transgenic lines that overexpress and downregulate one AREB-like transcription factor, SlAREB1, were used to determine its effect on the levels of some metabolites determining fruit quality. Higher levels of citric acid, malic acid, glutamic acid, glucose and fructose were observed in SlAREB1-overexpressing lines compared with those in antisense suppression lines in red mature fruit pericarp. The higher hexose concentration correlated with increased expression of genes encoding a vacuolar invertase (EC 3.2.1.26) and a sucrose synthase (EC 2.4.1.13). No significant changes were found in ethylene content which agrees with the normal ripening phenotype observed in transgenic fruits. These results suggest that an AREB-mediated ABA signal affects the metabolism of these compounds during the fruit developmental program. Copyright © Physiologia Plantarum 2010.

Abscisic Acid and Abiotic Stress Tolerance in Crop Plants

PubMed Central

Sah, Saroj K.; Reddy, Kambham R.; Li, Jiaxu

2016-01-01

Abiotic stress is a primary threat to fulfill the demand of agricultural production to feed the world in coming decades. Plants reduce growth and development process during stress conditions, which ultimately affect the yield. In stress conditions, plants develop various stress mechanism to face the magnitude of stress challenges, although that is not enough to protect them. Therefore, many strategies have been used to produce abiotic stress tolerance crop plants, among them, abscisic acid (ABA) phytohormone engineering could be one of the methods of choice. ABA is an isoprenoid phytohormone, which regulates various physiological processes ranging from stomatal opening to protein storage and provides adaptation to many stresses like drought, salt, and cold stresses. ABA is also called an important messenger that acts as the signaling mediator for regulating the adaptive response of plants to different environmental stress conditions. In this review, we will discuss the role of ABA in response to abiotic stress at the molecular level and ABA signaling. The review also deals with the effect of ABA in respect to gene expression. PMID:27200044

The Pepper RING-Type E3 Ligase CaAIRF1 Regulates ABA and Drought Signaling via CaADIP1 Protein Phosphatase Degradation.

PubMed

Lim, Chae Woo; Baek, Woonhee; Lee, Sung Chul

2017-04-01

Ubiquitin-mediated protein modification occurs at multiple steps of abscisic acid (ABA) signaling. Here, we sought proteins responsible for degradation of the pepper ( Capsicum annuum ) type 2C protein phosphatase CaADIP1 via the 26S proteasome system. We showed that the RING-type E3 ligase CaAIRF1 ( Capsicum annuum ADIP1 Interacting RING Finger Protein 1) interacts with and ubiquitinates CaADIP1. CaADIP1 degradation was slower in crude proteins from CaAIRF1 -silenced peppers than in those from control plants. CaAIRF1 -silenced pepper plants displayed reduced ABA sensitivity and decreased drought tolerance characterized by delayed stomatal closure and suppressed induction of ABA- and drought-responsive marker genes. In contrast, CaAIRF1 -overexpressing Arabidopsis ( Arabidopsis thaliana ) plants exhibited ABA-hypersensitive and drought-tolerant phenotypes. Moreover, in these plants, CaADIP1-induced ABA hyposensitivity was strongly suppressed by CaAIRF1 overexpression. Our findings highlight a potential new route for fine-tune regulation of ABA signaling in pepper via CaAIRF1 and CaADIP1. © 2017 American Society of Plant Biologists. All Rights Reserved.

Nitric Oxide Mediates the Hormonal Control of Crassulacean Acid Metabolism Expression in Young Pineapple Plants1[W][OA

PubMed Central

Freschi, Luciano; Rodrigues, Maria Aurineide; Domingues, Douglas Silva; Purgatto, Eduardo; Van Sluys, Marie-Anne; Magalhaes, Jose Ronaldo; Kaiser, Werner M.; Mercier, Helenice

2010-01-01

Genotypic, developmental, and environmental factors converge to determine the degree of Crassulacean acid metabolism (CAM) expression. To characterize the signaling events controlling CAM expression in young pineapple (Ananas comosus) plants, this photosynthetic pathway was modulated through manipulations in water availability. Rapid, intense, and completely reversible up-regulation in CAM expression was triggered by water deficit, as indicated by the rise in nocturnal malate accumulation and in the expression and activity of important CAM enzymes. During both up- and down-regulation of CAM, the degree of CAM expression was positively and negatively correlated with the endogenous levels of abscisic acid (ABA) and cytokinins, respectively. When exogenously applied, ABA stimulated and cytokinins repressed the expression of CAM. However, inhibition of water deficit-induced ABA accumulation did not block the up-regulation of CAM, suggesting that a parallel, non-ABA-dependent signaling route was also operating. Moreover, strong evidence revealed that nitric oxide (NO) may fulfill an important role during CAM signaling. Up-regulation of CAM was clearly observed in NO-treated plants, and a conspicuous temporal and spatial correlation was also evident between NO production and CAM expression. Removal of NO from the tissues either by adding NO scavenger or by inhibiting NO production significantly impaired ABA-induced up-regulation of CAM, indicating that NO likely acts as a key downstream component in the ABA-dependent signaling pathway. Finally, tungstate or glutamine inhibition of the NO-generating enzyme nitrate reductase completely blocked NO production during ABA-induced up-regulation of CAM, characterizing this enzyme as responsible for NO synthesis during CAM signaling in pineapple plants. PMID:20147491

Abscisic Acid Is a Major Regulator of Grape Berry Ripening Onset: New Insights into ABA Signaling Network

PubMed Central

Pilati, Stefania; Bagagli, Giorgia; Sonego, Paolo; Moretto, Marco; Brazzale, Daniele; Castorina, Giulia; Simoni, Laura; Tonelli, Chiara; Guella, Graziano; Engelen, Kristof; Galbiati, Massimo; Moser, Claudio

2017-01-01

Grapevine is a world-wide cultivated economically relevant crop. The process of berry ripening is non-climacteric and does not rely on the sole ethylene signal. Abscisic acid (ABA) is recognized as an important hormone of ripening inception and color development in ripening berries. In order to elucidate the effect of this signal at the molecular level, pre-véraison berries were treated ex vivo for 20 h with 0.2 mM ABA and berry skin transcriptional modulation was studied by RNA-seq after the treatment and 24 h later, in the absence of exogenous ABA. This study highlighted that a small amount of ABA triggered its own biosynthesis and had a transcriptome-wide effect (1893 modulated genes) characterized by the amplification of the transcriptional response over time. By comparing this dataset with the many studies on ripening collected within the grapevine transcriptomic compendium Vespucci, an extended overlap between ABA- and ripening modulated gene sets was observed (71% of the genes), underpinning the role of this hormone in the regulation of berry ripening. The signaling network of ABA, encompassing ABA metabolism, transport and signaling cascade, has been analyzed in detail and expanded based on knowledge from other species in order to provide an integrated molecular description of this pathway at berry ripening onset. Expression data analysis was combined with in silico promoter analysis to identify candidate target genes of ABA responsive element binding protein 2 (VvABF2), a key upstream transcription factor of the ABA signaling cascade which is up-regulated at véraison and also by ABA treatments. Two transcription factors, VvMYB143 and VvNAC17, and two genes involved in protein degradation, Armadillo-like and Xerico-like genes, were selected for in vivo validation by VvABF2-mediated promoter trans-activation in tobacco. VvNAC17 and Armadillo-like promoters were induced by ABA via VvABF2, while VvMYB143 responded to ABA in a VvABF2-independent manner. This knowledge of the ABA cascade in berry skin contributes not only to the understanding of berry ripening regulation but might be useful to other areas of viticultural interest, such as bud dormancy regulation and drought stress tolerance. PMID:28680438

Basic leucine zipper transcription factor SlbZIP1 mediates salt and drought stress tolerance in tomato.

PubMed

Zhu, Mingku; Meng, Xiaoqing; Cai, Jing; Li, Ge; Dong, Tingting; Li, Zongyun

2018-05-08

Basic region/leucine zipper (bZIP) transcription factors perform as crucial regulators in ABA-mediated stress response in plants. Nevertheless, the functions for most bZIP family members in tomato remain to be deciphered. Here we examined the functional characterization of SlbZIP1 under salt and drought stresses in tomato. Silencing of SlbZIP1 in tomato resulted in reduced expression of multiple ABA biosynthesis- and signal transduction-related genes in transgenic plants. In stress assays, SlbZIP1-RNAi transgenic plants exhibited reduced tolerance to salt and drought stresses compared with WT plants, as are evaluated by multiple physiological parameters associated with stress responses, such as decreased ABA, chlorophyll contents and CAT activity, and increased MDA content. In addition, RNA-seq analysis of transgenic plants revealed that the transcription levels of multiple genes encoding defense proteins related to responses to abiotic stress (e.g. endochitinase, peroxidases, and lipid transfer proteins) and biotic stress (e.g. pathogenesis-related proteins) were downregulated in SlbZIP1-RNAi plants, suggesting that SlbZIP1 plays a role in regulating the genes related to biotic and abiotic stress response. Collectively, the data suggest that SlbZIP1 exerts an essential role in salt and drought stress tolerance through modulating an ABA-mediated pathway, and SlbZIP1 may hold potential applications in the engineering of salt- and drought-tolerant tomato cultivars.

ABF2, an ABRE-binding bZIP factor, is an essential component of glucose signaling and its overexpression affects multiple stress tolerance.

PubMed

Kim, Sunmi; Kang, Jung-Youn; Cho, Dong-Im; Park, Ji Hye; Kim, Soo Young

2004-10-01

Phytohormone abscisic acid (ABA) regulates stress-responsive gene expression during vegetative growth, which is mediated largely by cis-elements sharing the ACGTGGC consensus. Although many transcription factors are known to bind the elements in vitro, only a few have been demonstrated to have in vivo functions and their specific roles in ABA/stress responses are mostly unknown. Here, we report that ABF2, an ABF subfamily member of bZIP proteins interacting with the ABA-responsive elements, is involved in ABA/stress responses. Its overexpression altered ABA sensitivity, dehydration tolerance, and the expression levels of ABA/stress-regulated genes. Furthermore, ABF2 overexpression promoted glucose-induced inhibition of seedling development, whereas its mutation impaired glucose response. The reduced sugar sensitivity was not observed with mutants of two other ABF family members, ABF3 and ABF4. Instead, these mutants displayed defects in ABA, salt, and dehydration responses, which were not observed with the abf2 mutant. Our data indicate distinct roles of ABF family members: whereas ABF3 and ABF4 play essential roles in ABA/stress responses, ABF2 is required for normal glucose response. We also show that ABF2 overexpression affects multiple stress tolerance.

Karrikins delay soybean seed germination by mediating abscisic acid and gibberellin biogenesis under shaded conditions

PubMed Central

Meng, Yongjie; Chen, Feng; Shuai, Haiwei; Luo, Xiaofeng; Ding, Jun; Tang, Shengwen; Xu, Shuanshuan; Liu, Jianwei; Liu, Weiguo; Du, Junbo; Liu, Jiang; Yang, Feng; Sun, Xin; Yong, Taiwen; Wang, Xiaochun; Feng, Yuqi; Shu, Kai; Yang, Wenyu

2016-01-01

Karrikins (KAR) are a class of signal compounds, discovered in wildfire smoke, which affect seed germination. Currently, numerous studies have focused on the model plant Arabidopsis in the KAR research field, rather than on crops. Thus the regulatory mechanisms underlying KAR regulation of crop seed germination are largely unknown. Here, we report that KAR delayed soybean seed germination through enhancing abscisic acid (ABA) biosynthesis, while impairing gibberellin (GA) biogenesis. Interestingly, KAR only retarded soybean seed germination under shaded conditions, rather than under dark and white light conditions, which differs from in Arabidopsis. Phytohormone quantification showed that KAR enhanced ABA biogenesis while impairing GA biosynthesis during the seed imbibition process, and subsequently, the ratio of active GA4 to ABA was significantly reduced. Further qRT-PCR analysis showed that the transcription pattern of genes involved in ABA and GA metabolic pathways are consistent with the hormonal measurements. Finally, fluridone, an ABA biogenesis inhibitor, remarkably rescued the delayed-germination phenotype of KAR-treatment; and paclobutrazol, a GA biosynthesis inhibitor, inhibited soybean seed germination. Taken together, these evidences suggest that KAR inhibit soybean seed germination by mediating the ratio between GA and ABA biogenesis. PMID:26902640

Karrikins delay soybean seed germination by mediating abscisic acid and gibberellin biogenesis under shaded conditions.

PubMed

Meng, Yongjie; Chen, Feng; Shuai, Haiwei; Luo, Xiaofeng; Ding, Jun; Tang, Shengwen; Xu, Shuanshuan; Liu, Jianwei; Liu, Weiguo; Du, Junbo; Liu, Jiang; Yang, Feng; Sun, Xin; Yong, Taiwen; Wang, Xiaochun; Feng, Yuqi; Shu, Kai; Yang, Wenyu

2016-02-23

Karrikins (KAR) are a class of signal compounds, discovered in wildfire smoke, which affect seed germination. Currently, numerous studies have focused on the model plant Arabidopsis in the KAR research field, rather than on crops. Thus the regulatory mechanisms underlying KAR regulation of crop seed germination are largely unknown. Here, we report that KAR delayed soybean seed germination through enhancing abscisic acid (ABA) biosynthesis, while impairing gibberellin (GA) biogenesis. Interestingly, KAR only retarded soybean seed germination under shaded conditions, rather than under dark and white light conditions, which differs from in Arabidopsis. Phytohormone quantification showed that KAR enhanced ABA biogenesis while impairing GA biosynthesis during the seed imbibition process, and subsequently, the ratio of active GA4 to ABA was significantly reduced. Further qRT-PCR analysis showed that the transcription pattern of genes involved in ABA and GA metabolic pathways are consistent with the hormonal measurements. Finally, fluridone, an ABA biogenesis inhibitor, remarkably rescued the delayed-germination phenotype of KAR-treatment; and paclobutrazol, a GA biosynthesis inhibitor, inhibited soybean seed germination. Taken together, these evidences suggest that KAR inhibit soybean seed germination by mediating the ratio between GA and ABA biogenesis.

Isolation and characterization of an osmotic stress and ABA induced histone deacetylase in Arachis hygogaea

PubMed Central

Su, Liang-Chen; Deng, Bin; Liu, Shuai; Li, Li-Mei; Hu, Bo; Zhong, Yu-Ting; Li, Ling

2015-01-01

Histone acetylation, which together with histone methylation regulates gene activity in response to stress, is an important epigenetic modification. There is an increasing research focus on histone acetylation in crops, but there is no information to date in peanut (Arachis hypogaea). We showed that osmotic stress and ABA affect the acetylation of histone H3 loci in peanut seedlings by immunoblotting experiments. Using RNA-seq data for peanut, we found a RPD3/HDA1-like superfamily histone deacetylase (HDAC), termed AhHDA1, whose gene is up-regulated by PEG-induced water limitation and ABA signaling. We isolated and characterized AhHDA1 from A. hypogaea, showing that AhHDA1 is very similar to an Arabidopsis HDAC (AtHDA6) and, in recombinant form, possesses HDAC activity. To understand whether and how osmotic stress and ABA mediate the peanut stress response by epigenetics, the expression of AhHDA1 and stress-responsive genes following treatment with PEG, ABA, and the specific HDAC inhibitor trichostatin A (TSA) were analyzed. AhHDA1 transcript levels were enhanced by all three treatments, as was expression of peanut transcription factor genes, indicating that AhHDA1 might be involved in the epigenetic regulation of stress resistance genes that comprise the responses to osmotic stress and ABA. PMID:26217363

The Arabidopsis transcription factor ABIG1 relays ABA signaled growth inhibition and drought induced senescence.

PubMed

Liu, Tie; Longhurst, Adam D; Talavera-Rauh, Franklin; Hokin, Samuel A; Barton, M Kathryn

2016-10-04

Drought inhibits plant growth and can also induce premature senescence. Here we identify a transcription factor, ABA INSENSITIVE GROWTH 1 (ABIG1) required for abscisic acid (ABA) mediated growth inhibition, but not for stomatal closure. ABIG1 mRNA levels are increased both in response to drought and in response to ABA treatment. When treated with ABA, abig1 mutants remain greener and produce more leaves than comparable wild-type plants. When challenged with drought, abig1 mutants have fewer yellow, senesced leaves than wild-type. Induction of ABIG1 transcription mimics ABA treatment and regulates a set of genes implicated in stress responses. We propose a model in which drought acts through ABA to increase ABIG1 transcription which in turn restricts new shoot growth and promotes leaf senescence. The results have implications for plant breeding: the existence of a mutant that is both ABA resistant and drought resistant points to new strategies for isolating drought resistant genetic varieties.

OsRACK1 Is Involved in Abscisic Acid- and H2O2-Mediated Signaling to Regulate Seed Germination in Rice (Oryza sativa, L.)

PubMed Central

Zhang, Dongping; Chen, Li; Li, Dahong; Lv, Bing; Chen, Yun; Chen, Jingui; XuejiaoYan; Liang, Jiansheng

2014-01-01

The receptor for activated C kinase 1 (RACK1) is one member of the most important WD repeat–containing family of proteins found in all eukaryotes and is involved in multiple signaling pathways. However, compared with the progress in the area of mammalian RACK1, our understanding of the functions and molecular mechanisms of RACK1 in the regulation of plant growth and development is still in its infancy. In the present study, we investigated the roles of rice RACK1A gene (OsRACK1A) in controlling seed germination and its molecular mechanisms by generating a series of transgenic rice lines, of which OsRACK1A was either over-expressed or under-expressed. Our results showed that OsRACK1A positively regulated seed germination and negatively regulated the responses of seed germination to both exogenous ABA and H2O2. Inhibition of ABA biosynthesis had no enhancing effect on germination, whereas inhibition of ABA catabolism significantly suppressed germination. ABA inhibition on seed germination was almost fully recovered by exogenous H2O2 treatment. Quantitative analyses showed that endogenous ABA levels were significantly higher and H2O2 levels significantly lower in OsRACK1A-down regulated transgenic lines as compared with those in wildtype or OsRACK1A-up regulated lines. Quantitative real-time PCR analyses showed that the transcript levels of OsRbohs and amylase genes, RAmy1A and RAmy3D, were significantly lower in OsRACK1A-down regulated transgenic lines. It is concluded that OsRACK1A positively regulates seed germination by controlling endogenous levels of ABA and H2O2 and their interaction. PMID:24865690

Directly transforming PCR-amplified DNA fragments into plant cells is a versatile system that facilitates the transient expression assay.

PubMed

Lu, Yuming; Chen, Xi; Wu, Yuxuan; Wang, Yanping; He, Yuqing; Wu, Yan

2013-01-01

A circular plasmid containing a gene coding sequence has been broadly used for studying gene regulation in cells. However, to accommodate a quick screen plasmid construction and preparation can be time consuming. Here we report a PCR amplified dsDNA fragments (PCR-fragments) based transient expression system (PCR-TES) for suiting in the study of gene regulation in plant cells. Instead of transforming plasmids into plant cells, transient expression of PCR-fragments can be applicable. The transformation efficiency and expression property of PCR-fragments are comparable to transformation using plasmids. We analyzed the transformation efficiency in PCR-TES at transcription and protein levels. Our results indicate that the PCR-TES is as versatile as the conventional transformation system using plasmid DNA. Through reconstituting PYR1-mediated ABA signaling pathway in Arabidopsis mesophyll protoplasts, we were not only validating the practicality of PCR-TES but also screening potential candidates of CDPK family members which might be involved in the ABA signaling. Moreover, we determined that phosphorylation of ABF2 by CPK4 could be mediated by ABA-induced PYR1 and ABI1, demonstrating a crucial role of CDPKs in the ABA signaling. In summary, PCR-TES can be applicable to facilitate analyzing gene regulation and for the screen of putative regulatory molecules at the high throughput level in plant cells.

Directly Transforming PCR-Amplified DNA Fragments into Plant Cells Is a Versatile System That Facilitates the Transient Expression Assay

PubMed Central

Lu, Yuming; Chen, Xi; Wu, Yuxuan; Wang, Yanping; He, Yuqing; Wu, Yan

2013-01-01

A circular plasmid containing a gene coding sequence has been broadly used for studying gene regulation in cells. However, to accommodate a quick screen plasmid construction and preparation can be time consuming. Here we report a PCR amplified dsDNA fragments (PCR-fragments) based transient expression system (PCR-TES) for suiting in the study of gene regulation in plant cells. Instead of transforming plasmids into plant cells, transient expression of PCR-fragments can be applicable. The transformation efficiency and expression property of PCR-fragments are comparable to transformation using plasmids. We analyzed the transformation efficiency in PCR-TES at transcription and protein levels. Our results indicate that the PCR-TES is as versatile as the conventional transformation system using plasmid DNA. Through reconstituting PYR1-mediated ABA signaling pathway in Arabidopsis mesophyll protoplasts, we were not only validating the practicality of PCR-TES but also screening potential candidates of CDPK family members which might be involved in the ABA signaling. Moreover, we determined that phosphorylation of ABF2 by CPK4 could be mediated by ABA-induced PYR1 and ABI1, demonstrating a crucial role of CDPKs in the ABA signaling. In summary, PCR-TES can be applicable to facilitate analyzing gene regulation and for the screen of putative regulatory molecules at the high throughput level in plant cells. PMID:23468926

Drought and exogenous abscisic acid alter hydrogen peroxide accumulation and differentially regulate the expression of two maize RD22-like genes.

PubMed

Phillips, Kyle; Ludidi, Ndiko

2017-08-18

Increased biosynthesis of abscisic acid (ABA) occurs in plants in response to water deficit, which is mediated by changes in the levels of reactive oxygen species such as H 2 O 2 . Water deficit and ABA induce expression of some RD22-like proteins. This study aimed to evaluate the effect of water deficit and exogenous ABA (50 µM ABA applied every 24 hours for a total of 72 hours) on H 2 O 2 content in Zea mays (maize) and to characterise genes encoding two putative maize RD22-like proteins (designated ZmRD22A and ZmRD22B). The expression profiles of the two putative maize RD22-like genes in response to water deficit and treatment with ABA were examined in leaves. In silico analyses showed that the maize RD22-like proteins share domain organisation with previously characterized RD22-like proteins. Both water deficit and exogenous ABA resulted in increased H 2 O 2 content in leaves but the increase was more pronounced in response to water deficit than to exogenous ABA. Lignin content was not affected by exogenous ABA, whereas it was decreased by water deficit. Expression of both RD22-like genes was up-regulated by drought but the ZmRD22A gene was not influenced by exogenous ABA, whereas ZmRD22B was highly responsive to exogenous ABA.

Regulation of epinasty induced by 2,4-dichlorophenoxyacetic acid in pea and Arabidopsis plants.

PubMed

Pazmiño, D M; Rodríguez-Serrano, M; Sanz, M; Romero-Puertas, M C; Sandalio, L M

2014-07-01

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) causes uncontrolled cell division and malformed growth in plants, giving rise to leaf epinasty and stem curvature. In this study, mechanisms involved in the regulation of leaf epinasty induced by 2,4-D were studied using different chemicals involved in reactive oxygen species (ROS) accumulation (diphenyleniodonium, butylated hydroxyanisole, EDTA, allopurinol), calcium channels (LaCl3), protein phosphorylation (cantharidin, wortmannin) and ethylene emission/perception (aminoethoxyvinyl glycine, AgNO3). The effect of these compounds on the epinasty induced by 2,4-D was analysed in shoots and leaf strips from pea plants. For further insight into the effect of 2,4-D, studies were also made in Arabidopsis mutants deficient in ROS production (rbohD, rbohF, xdh), ethylene (ein 3-1, ctr 1-1, etr 1-1), abscisic acid (aba 3.1), and jasmonic acid (coi 1.1, jar 1.1, opr 3) pathways. The results suggest that ROS production, mainly ·OH, is essential in the development of epinasty triggered by 2,4-D. Epinasty was also found to be regulated by Ca2+, protein phosphorylation and ethylene, although all these factors act downstream of ROS production. The use of Arabidopsis mutants appears to indicate that abscisic and jasmonic acid are not involved in regulating epinasty, although they could be involved in other symptoms induced by 2,4-D. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

Abscisic acid dynamics in roots detected with genetically encoded FRET sensors

PubMed Central

Jones, Alexander M; Danielson, Jonas ÅH; ManojKumar, Shruti N; Lanquar, Viviane; Grossmann, Guido; Frommer, Wolf B

2014-01-01

Cytosolic hormone levels must be tightly controlled at the level of influx, efflux, synthesis, degradation and compartmentation. To determine ABA dynamics at the single cell level, FRET sensors (ABACUS) covering a range ∼0.2–800 µM were engineered using structure-guided design and a high-throughput screening platform. When expressed in yeast, ABACUS1 detected concentrative ABA uptake mediated by the AIT1/NRT1.2 transporter. Arabidopsis roots expressing ABACUS1-2µ (Kd∼2 µM) and ABACUS1-80µ (Kd∼80 µM) respond to perfusion with ABA in a concentration-dependent manner. The properties of the observed ABA accumulation in roots appear incompatible with the activity of known ABA transporters (AIT1, ABCG40). ABACUS reveals effects of external ABA on homeostasis, that is, ABA-triggered induction of ABA degradation, modification, or compartmentation. ABACUS can be used to study ABA responses in mutants and quantitatively monitor ABA translocation and regulation, and identify missing components. The sensor screening platform promises to enable rapid fine-tuning of the ABA sensors and engineering of plant and animal hormone sensors to advance our understanding of hormone signaling. DOI: http://dx.doi.org/10.7554/eLife.01741.001 PMID:24737862

GID1 modulates stomatal response and submergence tolerance involving abscisic acid and gibberellic acid signaling in rice.

PubMed

Du, Hao; Chang, Yu; Huang, Fei; Xiong, Lizhong

2015-11-01

Plant responses to abiotic stresses are coordinated by arrays of growth and developmental programs. Gibberellic acid (GA) and abscisic acid (ABA) play critical roles in the developmental programs and environmental responses, respectively, through complex signaling and metabolism networks. However, crosstalk between the two phytohormones in stress responses remains largely unknown. In this study, we report that GIBBERELLIN-INSENSITIVE DWARF 1 (GID1), a soluble receptor for GA, regulates stomatal development and patterning in rice (Oryza sativa L.). The gid1 mutant showed impaired biosynthesis of endogenous ABA under drought stress conditions, but it exhibited enhanced sensitivity to exogenous ABA. Scanning electron microscope and infrared thermal image analysis indicated an increase in the stomatal conductance in the gid1 mutant under drought conditions. Interestingly, the gid1 mutant had increased levels of chlorophyll and carbohydrates under submergence conditions, and showed enhanced reactive oxygen species (ROS)-scavenging ability and submergence tolerance compared with the wild-type. Further analyses suggested that the function of GID1 in submergence responses is partially dependent on ABA, and GA signaling by GID1 is involved in submergence tolerance by modulating carbohydrate consumption. Taken together, these findings suggest GID1 plays distinct roles in stomatal response and submergence tolerance through both the ABA and GA signaling pathways in rice. © 2014 Institute of Botany, Chinese Academy of Sciences.

The Basic Leucine Zipper Transcription Factor ABSCISIC ACID RESPONSE ELEMENT-BINDING FACTOR2 Is an Important Transcriptional Regulator of Abscisic Acid-Dependent Grape Berry Ripening Processes1[W][OPEN

PubMed Central

Nicolas, Philippe; Lecourieux, David; Kappel, Christian; Cluzet, Stéphanie; Cramer, Grant; Delrot, Serge; Lecourieux, Fatma

2014-01-01

In grape (Vitis vinifera), abscisic acid (ABA) accumulates during fruit ripening and is thought to play a pivotal role in this process, but the molecular basis of this control is poorly understood. This work characterizes ABSCISIC ACID RESPONSE ELEMENT-BINDING FACTOR2 (VvABF2), a grape basic leucine zipper transcription factor belonging to a phylogenetic subgroup previously shown to be involved in ABA and abiotic stress signaling in other plant species. VvABF2 transcripts mainly accumulated in the berry, from the onset of ripening to the harvesting stage, and were up-regulated by ABA. Microarray analysis of transgenic grape cells overexpressing VvABF2 showed that this transcription factor up-regulates and/or modifies existing networks related to ABA responses. In addition, grape cells overexpressing VvABF2 exhibited enhanced responses to ABA treatment compared with control cells. Among the VvABF2-mediated responses highlighted in this study, the synthesis of phenolic compounds and cell wall softening were the most strongly affected. VvABF2 overexpression strongly increased the accumulation of stilbenes that play a role in plant defense and human health (resveratrol and piceid). In addition, the firmness of fruits from tomato (Solanum lycopersicum) plants overexpressing VvABF2 was strongly reduced. These data indicate that VvABF2 is an important transcriptional regulator of ABA-dependent grape berry ripening. PMID:24276949

Functional analysis of the pepper protein phosphatase, CaAIPP1, and its interacting partner CaAIRF1: Modulation of ABA signalling and the drought stress response.

PubMed

Baek, Woonhee; Lim, Chae Woo; Lee, Sung Chul

2017-10-01

Plant adaptive responses to abiotic stress are coordinated by restriction of plant growth and development. The plant hormone abscisic acid (ABA) is the key regulator of the response to abiotic stress, and its sensitivity determines abiotic stress tolerance levels. We previously showed that the E3 ubiquitin ligase CaAIRF1 functions as a positive regulator of ABA and drought stress via modulation of transcription and stability of the type 2C protein phosphatase CaADIP1. Here, we report the identification and functional analysis of a novel-type 2C phosphatase, CaAIPP1 (Capsicum annuum CaAIRF1 Interacting Protein Phosphatase 1). CaAIPP1 interacted with and was ubiquitinated by CaAIRF1. CaAIPP1 gene expression in pepper leaves was induced by ABA and drought. CaAIPP1 degradation was faster in crude protein extracts from ABA-treated pepper plants than in those from control plants. CaAIPP1-overexpressing plants displayed an ABA-hyposensitive phenotype during seed germination and seedling growth. Moreover, these plants exhibited a drought-sensitive phenotype characterized by high levels of transpirational water loss via decreased stomatal closure and reduced leaf temperatures. Our data indicate that CaAIPP1 is a negative regulator of the drought stress response via ABA-mediated signalling. Our findings provide a valuable insight into the plant defence mechanism that operates during drought stress. © 2017 John Wiley & Sons Ltd.

Rosmarinic acid induces rabbit articular chondrocyte differentiation by decreases matrix metalloproteinase-13 and inflammation by upregulating cyclooxygenase-2 expression.

PubMed

Eo, Seong-Hui; Kim, Song Ja

2017-09-18

Matrix metalloproteinases (MMPs) are known to play an important role in the degradation of the extracellular matrix and the pathological progression of osteoarthritis (OA). The natural polyphenolic compound rosmarinic acid (Ros. A) has been shown to suppress the inhibitory activity of matrix metalloproteinases (MMPs). However, the effects of Ros. A on OA have not been investigated. In the current study, primary articular chondrocytes were cultured from rabbit articular cartilage and treated with Ros. A. Phenotypic characterization was performed by western blotting to assess specific markers, prostaglandin E 2 (PGE 2 ) assays, and alcian blue staining to measure sulfated-proteoglycan production. We report that in rabbit articular chondrocytes, Ros. A increased type II collagen, sulfated-proteoglycan, cyclooxygenase-2 (COX-2), and PGE 2 production in a dose- and time-dependent manner. Furthermore, Ros. A suppressed the expression of MMP-13. In addition, treatment with Ros A activated extracellular signal-regulated kinase (ERK)-1/2 and p38 kinase signaling pathways. Inhibition of MMP-13 enhanced Ros. A-induced type II collagen expression and sulfated-proteoglycan synthesis but COX-2 and PGE 2 production were unchanged. Ros. A-mediated up-regulation of ERK phosphorylation was abolished by the MEK inhibitor, PD98059, which prevented induction of the associated inflammatory response. Inhibition of p38 kinase with SB203580 enhanced the increase in type II collagen expression via Ros. A-mediated down-regulation of MMP-13. Results suggest that ERK-1/2 regulates Ros. A-induced inflammation and that p38 regulates differentiation by inhibiting MMP-13 in rabbit articular chondrocytes.

Abscisic acid induces biosynthesis of bisbibenzyls and tolerance to UV-C in the liverwort Marchantia polymorpha.

PubMed

Kageyama, Akito; Ishizaki, Kimitsune; Kohchi, Takayuki; Matsuura, Hideyuki; Takahashi, Kosaku

2015-09-01

Environmental stresses are effective triggers for the biosynthesis of various secondary metabolites in plants, and phytohormones such as jasmonic acid and abscisic acid are known to mediate such responses in flowering plants. However, the detailed mechanism underlying the regulation of secondary metabolism in bryophytes remains unclear. In this study, the induction mechanism of secondary metabolites in the model liverwort Marchantia polymorpha was investigated. Abscisic acid (ABA) and ultraviolet irradiation (UV-C) were found to induce the biosynthesis of isoriccardin C, marchantin C, and riccardin F, which are categorized as bisbibenzyls, characteristic metabolites of liverworts. UV-C led to the significant accumulation of ABA. Overexpression of MpABI1, which encodes protein phosphatase 2C (PP2C) as a negative regulator of ABA signaling, suppressed accumulation of bisbibenzyls in response to ABA and UV-C irradiation and conferred susceptibility to UV-C irradiation. These data show that ABA plays a significant role in the induction of bisbibenzyl biosynthesis, which might confer tolerance against UV-C irradiation in M. polymorpha. Copyright © 2015 Elsevier Ltd. All rights reserved.

Negative regulation of ABA signaling by WRKY33 is critical for Arabidopsis immunity towards Botrytis cinerea 2100

PubMed Central

Liu, Shouan; Kracher, Barbara; Ziegler, Jörg; Birkenbihl, Rainer P; Somssich, Imre E

2015-01-01

The Arabidopsis mutant wrky33 is highly susceptible to Botrytis cinerea. We identified >1680 Botrytis-induced WRKY33 binding sites associated with 1576 Arabidopsis genes. Transcriptional profiling defined 318 functional direct target genes at 14 hr post inoculation. Comparative analyses revealed that WRKY33 possesses dual functionality acting either as a repressor or as an activator in a promoter-context dependent manner. We confirmed known WRKY33 targets involved in hormone signaling and phytoalexin biosynthesis, but also uncovered a novel negative role of abscisic acid (ABA) in resistance towards B. cinerea 2100. The ABA biosynthesis genes NCED3 and NCED5 were identified as direct targets required for WRKY33-mediated resistance. Loss-of-WRKY33 function resulted in elevated ABA levels and genetic studies confirmed that WRKY33 acts upstream of NCED3/NCED5 to negatively regulate ABA biosynthesis. This study provides the first detailed view of the genome-wide contribution of a specific plant transcription factor in modulating the transcriptional network associated with plant immunity. DOI: http://dx.doi.org/10.7554/eLife.07295.001 PMID:26076231

Nuclear-localized AtHSPR links abscisic acid-dependent salt tolerance and antioxidant defense in Arabidopsis.

PubMed

Yang, Tao; Zhang, Liang; Hao, Hongyan; Zhang, Peng; Zhu, Haowei; Cheng, Wei; Wang, Yongli; Wang, Xinyu; Wang, Chongying

2015-12-01

Salt stress from soil or irrigation water limits plant growth. A T-DNA insertion mutant in C24, named athspr (Arabidopsis thaliana heat shock protein-related), showed several phenotypes, including reduced organ size and enhanced sensitivity to environmental cues. The athspr mutant is severely impaired under salinity levels at which wild-type (WT) plants grow normally. AtHSPR encodes a nuclear-localized protein with ATPase activity, and its expression was enhanced by high salinity and abscisic acid (ABA). Overexpression (OE) of AtHSPR significantly enhanced tolerance to salt stress by increasing the activities of the antioxidant system and by maintaining K(+) /Na(+) homeostasis. Quantitative RT-PCR analyses showed that OE of AtHSPR increased the expression of ABA/stress-responsive, salt overly sensitive (SOS)-related and antioxidant-related genes. In addition, ABA content was reduced in athspr plants with or without salt stress, and exogenous ABA restored WT-like salt tolerance to athspr plants. athspr exhibited increased leaf stomatal density and stomatal index, slower ABA-induced stomatal closure and reduced drought tolerance relative to the WT. AtHSPR OE enhanced drought tolerance by reducing leaf water loss and stomatal aperture. Transcript profiling in athspr showed a differential salt-stress response for genes involved in accumulation of reactive oxygen species (ROS), ABA signaling, cell death, stress response and photosynthesis. Taken together, our results suggested that AtHSPR is involved in salt tolerance in Arabidopsis through modulation of ROS levels, ABA-dependent stomatal closure, photosynthesis and K(+) /Na(+) homeostasis. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

Abscisic Acid Antagonizes Ethylene Production through the ABI4-Mediated Transcriptional Repression of ACS4 and ACS8 in Arabidopsis.

PubMed

Dong, Zhijun; Yu, Yanwen; Li, Shenghui; Wang, Juan; Tang, Saijun; Huang, Rongfeng

2016-01-04

Increasing evidence has revealed that abscisic acid (ABA) negatively modulates ethylene biosynthesis, although the underlying mechanism remains unclear. To identify the factors involved, we conducted a screen for ABA-insensitive mutants with altered ethylene production in Arabidopsis. A dominant allele of ABI4, abi4-152, which produces a putative protein with a 16-amino-acid truncation at the C-terminus of ABI4, reduces ethylene production. By contrast, two recessive knockout alleles of ABI4, abi4-102 and abi4-103, result in increased ethylene evolution, indicating that ABI4 negatively regulates ethylene production. Further analyses showed that expression of the ethylene biosynthesis genes ACS4, ACS8, and ACO2 was significantly decreased in abi4-152 but increased in the knockout mutants, with partial dependence on ABA. Chromatin immunoprecipitation-quantitative PCR assays showed that ABI4 directly binds the promoters of these ethylene biosynthesis genes and that ABA enhances this interaction. A fusion protein containing the truncated ABI4-152 peptide accumulated to higher levels than its full-length counterpart in transgenic plants, suggesting that ABI4 is destabilized by its C terminus. Therefore, our results demonstrate that ABA negatively regulates ethylene production through ABI4-mediated transcriptional repression of the ethylene biosynthesis genes ACS4 and ACS8 in Arabidopsis. Copyright © 2016 The Author. Published by Elsevier Inc. All rights reserved.

Dissection of Arabidopsis NCED9 promoter regulatory regions reveals a role for ABA synthesized in embryos in the regulation of GA-dependent seed germination.

PubMed

Seo, Mitsunori; Kanno, Yuri; Frey, Anne; North, Helen M; Marion-Poll, Annie

2016-05-01

Nine-cis-epoxycarotenoid dioxygenase (NCED) catalyzes the key step of abscisic acid (ABA) biosynthesis. There are five genes encoding NCED in Arabidopsis, which differentially regulate ABA biosynthesis in a spatiotemporal manner in response to endogenous and environmental stimuli. Previous studies have shown that NCED9 is expressed in testa and embryos during seed development. In the present study, we have identified promoter regions required for the expression of NCED9 in testa and embryos, respectively. Electrophoretic mobility shift assays (EMSA) and yeast one-hybrid (Y1H) assays showed that several homeodomain-leucine zipper (HD-Zip) proteins, namely ATHBs, bound to the sequence required for expression of NCED9 in testa, suggesting that they redundantly regulate NCED9 expression. By expressing the NCED9 gene under the control of a deleted NCED9 promoter in an nced9 mutant expression was limited to embryos. Transformants were complemented for the paclobutrazol resistant germination phenotype of the mutant, suggesting that the ABA synthesis mediated by NCED9 in embryos plays an important role in the regulation of gibberellin (GA)-dependent seed germination. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Evaluating the involvement and interaction of abscisic acid and miRNA156 in the induction of anthocyanin biosynthesis in drought-stressed plants.

PubMed

González-Villagra, Jorge; Kurepin, Leonid V; Reyes-Díaz, Marjorie M

2017-08-01

ABA is involved in anthocyanin synthesis through the regulation of microRNA156, augmenting the level of expression of anthocyanin synthesis-related genes and, therefore, increasing anthocyanin level. Drought stress is the main cause of agricultural crop loss in the world. However, plants have developed mechanisms that allow them to tolerate drought stress conditions. At cellular level, drought stress induces changes in metabolite accumulation, including increases in anthocyanin levels due to upregulation of the anthocyanin biosynthetic pathway. Recent studies suggest that the higher anthocyanin content observed under drought stress conditions could be a consequence of a rise in the abscisic acid (ABA) concentration. This plant hormone crosses the plasma membrane by specific transporters, and it is recognized at the cytosolic level by receptors known as pyrabactin resistance (PYR)/regulatory component of ABA receptors (PYR/RCARs) that regulate downstream components. In this review, we discuss the hypothesis regarding the involvement of ABA in the regulation of microRNA156 (miRNA156), which is upregulated as part of dehydration stress responsiveness in different species. The miRNA156 upregulation produces a greater level of anthocyanin gene expression, forming the multienzyme complex that will synthesize an increased level of anthocyanins at the cytosolic face of the rough endoplasmic reticulum (RER). After synthesis, anthocyanins are transported from the RER to the vacuole by two possible models of transport: (1) membrane vesicle-mediated transport, or (2) membrane transporter-mediated transport. Thus, the aim was to analyze the recent findings on synthesis, transport and the possible mechanism by which ABA could increase anthocyanin synthesis under drought stress conditions potentially throughout microRNA156 (miRNA156).

F-box protein DOR functions as a novel inhibitory factor for abscisic acid-induced stomatal closure under drought stress in Arabidopsis,.

PubMed

Zhang, Yu'e; Xu, Wenying; Li, Zhonghui; Deng, Xing Wang; Wu, Weihua; Xue, Yongbiao

2008-12-01

Guard cells, which form stoma in leaf epidermis, sense and integrate environmental signals to modulate stomatal aperture in response to diverse conditions. Under drought stress, plants synthesize abscisic acid (ABA), which in turn induces a rapid closing of stoma, to prevent water loss by transpiration. However, many aspects of the molecular mechanism for ABA-mediated stomatal closure are still not understood. Here, we report a novel negative regulator of guard cell ABA signaling, DOR, in Arabidopsis (Arabidopsis thaliana). The DOR gene encodes a putative F-box protein, a member of the S-locus F-box-like family related to AhSLF-S(2) and specifically interacting with ASK14 and CUL1. A null mutation in DOR resulted in a hypersensitive ABA response of stomatal closing and a substantial increase of drought tolerance; in contrast, the transgenic plants overexpressing DOR were more susceptible to the drought stress. DOR is strongly expressed in guard cells and suppressed by ABA treatment, suggesting a negative feedback loop of DOR in ABA responses. Double-mutant analyses of dor with ABA-insensitive mutant abi1-1 showed that abi1-1 is epistatic to dor, but no apparent change of phospholipase Dalpha1 was detected between the wild type and dor. Affymetrix GeneChip analysis showed that DOR likely regulates ABA biosynthesis under drought stress. Taken together, our results demonstrate that DOR acts independent of phospholipase Dalpha1 in an ABA signaling pathway to inhibit the ABA-induced stomatal closure under drought stress.

Oxidative Stress Facilitates IFN-γ-Induced Mimic Extracellular Trap Cell Death in A549 Lung Epithelial Cancer Cells.

PubMed

Lin, Chiou-Feng; Chen, Chia-Ling; Chien, Shun-Yi; Tseng, Po-Chun; Wang, Yu-Chih; Tsai, Tsung-Ting

2016-01-01

We previously demonstrated that IFN-γ induces an autophagy-regulated mimic extracellular trap cell death (ETosis) in A549 human lung cancer cells. Regarding reactive oxygen species (ROS) are involved in ETosis, this study investigated the role of oxidative stress. After IFN-γ stimulation, a necrosis-like cell death mimic ETosis occurred accompanied by the inhibition of cell growth, aberrant nuclear staining, and nucleosome release. ROS were generated in a time-dependent manner with an increase in NADPH oxidase component protein expression. STAT1-mediated IFN regulatory factor-1 activation was essential for upregulating ROS production. By genetically silencing p47phox, IFN-γ-induced ROS and mimic ETosis were significantly attenuated. This mechanistic study indicated that ROS may mediate DNA damage followed by histone H3 citrullination. Furthermore, ROS promoted IFN-γ-induced mimic ETosis in cooperation with autophagy. These findings further demonstrate that ROS regulates IFN-γ-induced mimic ETosis in lung epithelial malignancy.

Oxidative Stress Facilitates IFN-γ-Induced Mimic Extracellular Trap Cell Death in A549 Lung Epithelial Cancer Cells

PubMed Central

Lin, Chiou-Feng; Chen, Chia-Ling; Chien, Shun-Yi; Tseng, Po-Chun; Wang, Yu-Chih; Tsai, Tsung-Ting

2016-01-01

We previously demonstrated that IFN-γ induces an autophagy-regulated mimic extracellular trap cell death (ETosis) in A549 human lung cancer cells. Regarding reactive oxygen species (ROS) are involved in ETosis, this study investigated the role of oxidative stress. After IFN-γ stimulation, a necrosis-like cell death mimic ETosis occurred accompanied by the inhibition of cell growth, aberrant nuclear staining, and nucleosome release. ROS were generated in a time-dependent manner with an increase in NADPH oxidase component protein expression. STAT1-mediated IFN regulatory factor-1 activation was essential for upregulating ROS production. By genetically silencing p47phox, IFN-γ-induced ROS and mimic ETosis were significantly attenuated. This mechanistic study indicated that ROS may mediate DNA damage followed by histone H3 citrullination. Furthermore, ROS promoted IFN-γ-induced mimic ETosis in cooperation with autophagy. These findings further demonstrate that ROS regulates IFN-γ-induced mimic ETosis in lung epithelial malignancy. PMID:27575372

Overlapping and distinct roles of AKIN10 and FUSCA3 in ABA and sugar signaling during seed germination.

PubMed

Tsai, Allen Yi-Lun; Gazzarrini, Sonia

2012-10-01

The Arabidopsis B3-domain transcription factor FUSCA3 (FUS3) is a master regulator of seed maturation and also a central modulator of hormonal responses during late embryogenesis and germination. Recently, we have identified AKIN10, the Arabidopsis ortholog of Snf1 (Sucrose Non-Fermenting-1)-Related Kinase1 (SnRK1), as a FUS3-interacting protein. We demonstrated that AKIN10 physically interacts with and phosphorylates FUS3 at its N-terminal region, and genetically interacts with FUS3 to regulate developmental phase transition and lateral organ growth. Snf1/AMPK/SnRK1 kinases are important sensors of the cellular energy level, and they are activated in response to starvation and cellular stress. Here we present findings that indicate FUS3 and AKIN10 functionally overlap in ABA signaling, but play different roles in sugar responses during germination. Seeds overexpressing FUS3 and AKIN10 both display ABA-hypersensitivity and delayed germination. The latter is partly dependent on de novo ABA synthesis in both genotypes, as delayed germination can be partially rescued by the ABA biosynthesis inhibitor, fluridone. However, seeds and seedlings overexpressing FUS3 and AKIN10 show different sugar responses. AKIN10-overexpressing seeds and seedlings are hypersensitive to glucose, while those overexpressing FUS3 display overall defects in osmotic stress, primarily during seedling growth, as they show increased sensitivity toward sorbitol and glucose. Hypersensitivity to sugar and/or osmotic stress during germination are partly dependent on de novo ABA synthesis for both genotypes, although are likely to act through distinct pathways. This data suggests that AKIN10 and FUS3 both act as positive regulators of seed responses to ABA, and that AKIN10 regulates sugar signaling while FUS3 mediates osmotic stress responses.

DNA Methylation Mediated Control of Gene Expression Is Critical for Development of Crown Gall Tumors

PubMed Central

Kneitz, Susanne; Weber, Dana; Fuchs, Joerg; Hedrich, Rainer; Deeken, Rosalia

2013-01-01

Crown gall tumors develop after integration of the T-DNA of virulent Agrobacterium tumefaciens strains into the plant genome. Expression of the T-DNA–encoded oncogenes triggers proliferation and differentiation of transformed plant cells. Crown gall development is known to be accompanied by global changes in transcription, metabolite levels, and physiological processes. High levels of abscisic acid (ABA) in crown galls regulate expression of drought stress responsive genes and mediate drought stress acclimation, which is essential for wild-type-like tumor growth. An impact of epigenetic processes such as DNA methylation on crown gall development has been suggested; however, it has not yet been investigated comprehensively. In this study, the methylation pattern of Arabidopsis thaliana crown galls was analyzed on a genome-wide scale as well as at the single gene level. Bisulfite sequencing analysis revealed that the oncogenes Ipt, IaaH, and IaaM were unmethylated in crown galls. Nevertheless, the oncogenes were susceptible to siRNA–mediated methylation, which inhibited their expression and subsequently crown gall growth. Genome arrays, hybridized with methylated DNA obtained by immunoprecipitation, revealed a globally hypermethylated crown gall genome, while promoters were rather hypomethylated. Mutants with reduced non-CG methylation developed larger tumors than the wild-type controls, indicating that hypermethylation inhibits plant tumor growth. The differential methylation pattern of crown galls and the stem tissue from which they originate correlated with transcriptional changes. Genes known to be transcriptionally inhibited by ABA and methylated in crown galls became promoter methylated upon treatment of A. thaliana with ABA. This suggests that the high ABA levels in crown galls may mediate DNA methylation and regulate expression of genes involved in drought stress protection. In summary, our studies provide evidence that epigenetic processes regulate gene expression, physiological processes, and the development of crown gall tumors. PMID:23408907

DNA methylation mediated control of gene expression is critical for development of crown gall tumors.

PubMed

Gohlke, Jochen; Scholz, Claus-Juergen; Kneitz, Susanne; Weber, Dana; Fuchs, Joerg; Hedrich, Rainer; Deeken, Rosalia

2013-01-01

Crown gall tumors develop after integration of the T-DNA of virulent Agrobacterium tumefaciens strains into the plant genome. Expression of the T-DNA-encoded oncogenes triggers proliferation and differentiation of transformed plant cells. Crown gall development is known to be accompanied by global changes in transcription, metabolite levels, and physiological processes. High levels of abscisic acid (ABA) in crown galls regulate expression of drought stress responsive genes and mediate drought stress acclimation, which is essential for wild-type-like tumor growth. An impact of epigenetic processes such as DNA methylation on crown gall development has been suggested; however, it has not yet been investigated comprehensively. In this study, the methylation pattern of Arabidopsis thaliana crown galls was analyzed on a genome-wide scale as well as at the single gene level. Bisulfite sequencing analysis revealed that the oncogenes Ipt, IaaH, and IaaM were unmethylated in crown galls. Nevertheless, the oncogenes were susceptible to siRNA-mediated methylation, which inhibited their expression and subsequently crown gall growth. Genome arrays, hybridized with methylated DNA obtained by immunoprecipitation, revealed a globally hypermethylated crown gall genome, while promoters were rather hypomethylated. Mutants with reduced non-CG methylation developed larger tumors than the wild-type controls, indicating that hypermethylation inhibits plant tumor growth. The differential methylation pattern of crown galls and the stem tissue from which they originate correlated with transcriptional changes. Genes known to be transcriptionally inhibited by ABA and methylated in crown galls became promoter methylated upon treatment of A. thaliana with ABA. This suggests that the high ABA levels in crown galls may mediate DNA methylation and regulate expression of genes involved in drought stress protection. In summary, our studies provide evidence that epigenetic processes regulate gene expression, physiological processes, and the development of crown gall tumors.

The Kinase Activity of Calcineurin B-like Interacting Protein Kinase 26 (CIPK26) Influences Its Own Stability and that of the ABA-regulated Ubiquitin Ligase, Keep on Going (KEG)

PubMed Central

Lyzenga, Wendy J.; Sullivan, Victoria; Liu, Hongxia; Stone, Sophia L.

2017-01-01

The Really Interesting New Gene (RING)-type E3 ligase, Keep on Going (KEG) plays a critical role in Arabidopsis growth after germination and the connections between KEG and hormone signaling pathways are expanding. With regards to abscisic acid (ABA) signaling, KEG targets ABA-responsive transcription factors abscisic acid insensitive 5, ABF1 and ABF3 for ubiquitination and subsequent degradation through the 26S proteasome. Regulation of E3 ligases through self-ubiquitination is common to RING-type E3 ligases and ABA promotes KEG self-ubiquitination and degradation. ABA-mediated degradation of KEG is phosphorylation-dependent; however, upstream signaling proteins that may regulate KEG stability have not been characterized. In this report, we show that CBL-Interacting Protein Kinase (CIPK) 26 can phosphorylate KEG in vitro. Using both in vitro and in planta degradation assays we provide evidence which suggests that the kinase activity of CIPK26 promotes the degradation of KEG. Furthermore, we found that the kinase activity of CIPK26 also influences its own stability; a constitutively active version is more stable than a wild type or a kinase dead version. Our results suggest a reciprocal regulation model wherein an activated and stable CIPK26 phosphorylates KEG to promote degradation of the E3. PMID:28443108

Transgenic Arabidopsis Plants Expressing the Type 1 Inositol 5-Phosphatase Exhibit Increased Drought Tolerance and Altered Abscisic Acid Signaling[W

PubMed Central

Perera, Imara Y.; Hung, Chiu-Yueh; Moore, Candace D.; Stevenson-Paulik, Jill; Boss, Wendy F.

2008-01-01

The phosphoinositide pathway and inositol-1,4,5-trisphosphate (InsP3) are implicated in plant responses to stress. To determine the downstream consequences of altered InsP3-mediated signaling, we generated transgenic Arabidopsis thaliana plants expressing the mammalian type I inositol polyphosphate 5-phosphatase (InsP 5-ptase), which specifically hydrolyzes soluble inositol phosphates and terminates the signal. Rapid transient Ca2+ responses to a cold or salt stimulus were reduced by ∼30% in these transgenic plants. Drought stress studies revealed, surprisingly, that the InsP 5-ptase plants lost less water and exhibited increased drought tolerance. The onset of the drought stress was delayed in the transgenic plants, and abscisic acid (ABA) levels increased less than in the wild-type plants. Stomatal bioassays showed that transgenic guard cells were less responsive to the inhibition of opening by ABA but showed an increased sensitivity to ABA-induced closure. Transcript profiling revealed that the drought-inducible ABA-independent transcription factor DREB2A and a subset of DREB2A-regulated genes were basally upregulated in the InsP 5-ptase plants, suggesting that InsP3 is a negative regulator of these DREB2A-regulated genes. These results indicate that the drought tolerance of the InsP 5-ptase plants is mediated in part via a DREB2A-dependent pathway and that constitutive dampening of the InsP3 signal reveals unanticipated interconnections between signaling pathways. PMID:18849493

Zyflamend Sensitizes Tumor Cells to TRAIL-Induced Apoptosis Through Up-Regulation of Death Receptors and Down-Regulation of Survival Proteins: Role of ROS-Dependent CCAAT/Enhancer-Binding Protein-Homologous Protein Pathway

PubMed Central

Kim, Ji Hye; Park, Byoungduck; Gupta, Subash C.; Kannappan, Ramaswamy; Sung, Bokyung

2012-01-01

Abstract Aim: TNF (tumor necrosis factor)-related apoptosis-inducing ligand (TRAIL), is a selective killer of tumor cells, although its potential is limited by the development of resistance. In this article, we investigated whether the polyherbal preparation Zyflamend® can sensitize tumor cells to TRAIL. Results: We found that Zyflamend potentiated TRAIL-induced apoptosis in human cancer cells. Zyflamend manifested its effects through several mechanisms. First, it down-regulated the expression of cell survival proteins known to be linked to resistance to TRAIL. Second, Zyflamend up-regulated the expression of pro-apoptotic protein, Bax. Third, Zyflamend up-regulated the expression of death receptors (DRs) for TRAIL. Up-regulation of DRs was critical as gene-silencing of these receptors significantly reduced the effect of Zyflamend on TRAIL-induced apoptosis. The up-regulation of DRs was dependent on CCAAT/enhancer-binding protein-homologous protein (CHOP), as Zyflamend induced CHOP, its gene-silencing abolished the induction of receptors, and mutation of the CHOP binding site on DR5 promoter abolished Zyflamend-mediated DR5 transactivation. Zyflamend mediated its effects through reactive oxygen species (ROS), as ROS quenching reduced its effect. Further, Zyflamend induced DR5 and CHOP and down-regulated the expression of cell survival proteins in nude mice bearing human pancreatic cancer cells. Innovation: Zyflamend can sensitize tumor cells to TRAIL through modulation of multiple cell signaling mechanisms that are linked to ROS. Conclusion: Zyflamend potentiates TRAIL-induced apoptosis through the ROS-CHOP-mediated up-regulation of DRs, increase in pro-apoptotic protein and down-regulation of cell survival proteins. Antioxid. Redox Signal. 16, 413–427. PMID:22004570

Can heavy metal pollution defend seed germination against heat stress? Effect of heavy metals (Cu(2+), Cd(2+) and Hg(2+)) on maize seed germination under high temperature.

PubMed

Deng, Benliang; Yang, Kejun; Zhang, Yifei; Li, Zuotong

2016-09-01

Heavy metal pollution, as well as greenhouse effect, has become a serious threat today. Both heavy metal and heat stresses can arrest seed germination. What response can be expected for seed germination under both stress conditions? Here, the effects of heavy metals (Cu(2+), Cd(2+) and Hg(2+)) on maize seed germination were investigated at 20 °C and 40 °C. Compared with 20 °C, heat stress induced thermodormancy. However, this thermodormancy could be significantly alleviated by the addition of a low concentration of heavy metals. Heavy metals, as well as heat stress induced H2O2 accumulation in germinating seeds. Interestingly, this low concentration of heavy metal that promoted seed germination could be partly blocked by DMTU (a specific ROS scavenger), irrespective of temperature. Accordingly, H2O2 addition reinforced this promoting effect on seed germination, which was induced by a low concentration of heavy metal. Furthermore, we found that the NADPH oxidase derived ROS was required for seed germination promoted by the heavy metals. Subsequently, treatment of seeds with fluridone (a specific inhibitor of ABA) or ABA significantly alleviated or aggravated thermodormancy, respectively. However, this alleviation or aggravation could be partly attenuated by a low concentration of heavy metals. In addition, germination that was inhibited by high concentrations of heavy metals was also partly reversed by fluridone. The obtained results support the idea that heavy metal-mediated ROS and hormone interaction can finally affect the thermodormancy release or not. Copyright © 2016 Elsevier Ltd. All rights reserved.

Abscisic acid induces a transient shift in signaling that enhances NF-κB-mediated parasite killing in the midgut of Anopheles stephensi without reducing lifespan or fecundity.

PubMed

Glennon, Elizabeth K K; Torrevillas, Brandi K; Morrissey, Shannon F; Ejercito, Jadrian M; Luckhart, Shirley

2017-07-13

Abscisic acid (ABA) is naturally present in mammalian blood and circulating levels can be increased by oral supplementation. We showed previously that oral ABA supplementation in a mouse model of Plasmodium yoelii 17XNL infection reduced parasitemia and gametocytemia, spleen and liver pathology, and parasite transmission to the mosquito Anopheles stephensi fed on these mice. Treatment of cultured Plasmodium falciparum with ABA at levels detected in our model had no effects on asexual growth or gametocyte formation in vitro. However, ABA treatment of cultured P. falciparum immediately prior to mosquito feeding significantly reduced oocyst development in A. stephensi via ABA-dependent synthesis of nitric oxide (NO) in the mosquito midgut. Here we describe the mechanisms of effects of ABA on mosquito physiology, which are dependent on phosphorylation of TGF-β-activated kinase 1 (TAK1) and associated with changes in homeostatic gene expression and activity of kinases that are central to metabolic regulation in the midgut epithelium. Collectively, the timing of these effects suggests a transient physiological shift that enhances NF-κB-dependent innate immunity without significantly altering mosquito lifespan or fecundity. ABA is a highly conserved regulator of immune and metabolic homeostasis within the malaria vector A. stephensi with potential as a transmission-blocking supplemental treatment.

Regulation of ROS Production and Vascular Function by Carbon Monoxide

PubMed Central

Choi, Yoon Kyung; Por, Elaine D.; Kwon, Young-Guen; Kim, Young-Myeong

2012-01-01

Carbon monoxide (CO) is a gaseous molecule produced from heme by heme oxygenase (HO). CO interacts with reduced iron of heme-containing proteins, leading to its involvement in various cellular events via its production of mitochondrial reactive oxygen species (ROS). CO-mediated ROS production initiates intracellular signal events, which regulate the expression of adaptive genes implicated in oxidative stress and functions as signaling molecule for promoting vascular functions, including angiogenesis and mitochondrial biogenesis. Therefore, CO generated either by exogenous delivery or by HO activity can be fundamentally involved in regulating mitochondria-mediated redox cascades for adaptive gene expression and improving blood circulation (i.e., O2 delivery) via neovascularization, leading to the regulation of mitochondrial energy metabolism. This paper will highlight the biological effects of CO on ROS generation and cellular redox changes involved in mitochondrial metabolism and angiogenesis. Moreover, cellular mechanisms by which CO is exploited for disease prevention and therapeutic applications will also be discussed. PMID:22928087

ABA-dependent inhibition of the ubiquitin proteasome system during germination at high temperature in Arabidopsis.

PubMed

Chiu, Rex Shun; Pan, Shiyue; Zhao, Rongmin; Gazzarrini, Sonia

2016-12-01

During germination, endogenous and environmental factors trigger changes in the transcriptome, translatome and proteome to break dormancy. In Arabidopsis thaliana, the ubiquitin proteasome system (UPS) degrades proteins that promote dormancy to allow germination. While research on the UPS has focused on the identification of proteasomal substrates, little information is known about the regulation of its activity. Here we characterized the activity of the UPS during dormancy release and maintenance by monitoring protein ubiquitination and degradation of two proteasomal substrates: Suc-LLVY-AMC, a well characterized synthetic substrate, and FUSCA3 (FUS3), a dormancy-promoting transcription factor degraded by the 26S proteasome. Our data indicate that proteasome activity and protein ubiquitination increase during imbibition at optimal temperature (21°C), and are required for seed germination. However, abscisic acid (ABA) and supraoptimal temperature (32°C) inhibit germination by dampening both protein ubiquitination and proteasome activity. Inhibition of UPS function by high temperature is reduced by the ABA biosynthesis inhibitor, fluridone, and in ABA biosynthetic mutants, suggesting that it is ABA dependent. Accordingly, inhibition of FUS3 degradation at 32°C is also dependent on ABA. Native gels show that inhibition of proteasome activity is caused by interference with the 26S/30S ratio as well as free 19S and 20S levels, impacting the proteasome degradation cycle. Transfer experiments show that ABA-mediated inhibition of proteasome activity at 21°C is restricted to the first 2 days of germination, a time window corresponding to seed sensitivity to environmental and ABA-mediated growth inhibition. Our data show that ABA and high temperature inhibit germination under unfavourable growth conditions by repressing the UPS. © 2016 The Authors The Plant Journal © 2016 John Wiley & Sons Ltd.

Role of thioproline on seed germination: interaction ROS-ABA and effects on antioxidative metabolism.

PubMed

Barba-Espin, Gregorio; Nicolas, Eduardo; Almansa, Maria Soledad; Cantero-Navarro, Elena; Albacete, Alfonso; Hernández, José Antonio; Díaz-Vivancos, Pedro

2012-10-01

In this work we investigate the effect of the imbibition of pea seeds with different thioproline (TP) concentrations on the germination percentage and the early growth of the seedlings. The interaction between TP and hydrogen peroxide (H₂O₂) treatments is also analysed in order to test if any synergy in germination and growth occurs. Although the imbibition of pea seeds in the presence of TP did not significantly improve the germination percentage, TP and/or H₂O₂ pre-treatments increased seedlings growth. This increase in seedling growth was reduced by abscisic acid (ABA) addition. Imbibition of pea seeds in the presence of ABA also reduced the endogenous H₂O₂ contents of pea seedlings in control and TP-treated seeds. The incubation of pea seeds with TP and/or H₂O₂ in presence or absence of ABA decreased the activity of H₂O₂-scavenging enzymes. The increase of the endogenous H₂O₂ contents observed in TP and/or H₂O₂ treatments in absence of ABA could be correlated with the decrease in these activities. Finally, the hormone profile of pea seedlings was investigated. The results show that the increase in seedling growth is correlated with a decrease in ABA in samples pre-treated with H₂O₂ and TP + H₂O₂. Nevertheless, no significant differences in endogenous ABA concentration were observed with the TP pre-treatment. This paper suggests a relationship between endogenous H₂O₂ contents and plant growth, so reinforcing the intricate crosstalk between reactive oxygen species (ROS) and plant hormones in seed germination signalling and early seedling development. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Omethoate treatment mitigates high salt stress inhibited maize seed germination.

PubMed

Yang, Kejun; Zhang, Yifei; Zhu, Lianhua; Li, Zuotong; Deng, Benliang

2018-01-01

Omethoate (OM) is a highly toxic organophophate insecticide, which is resistant to biodegradation in the environment and is widely used for pest control in agriculture. The effect of OM on maize seed germination was evaluated under salt stress. Salt (800mM) greatly reduced germination of maize seed and this could be reversed by OM. Additionally, H 2 O 2 treatment further improved the effect of OM on seed germination. Higher H 2 O 2 content was measured in OM treated seed compared to those with salt stress alone. Dimethylthiourea (DTMU), a specific scavenger of reactive oxygen species (ROS), inhibited the effect of OM on seed germination, as did IMZ (imidazole), an inhibitor of NADPH oxidase. Abscisic acid (ABA) inhibited the effect of OM on seed germination, whereas fluridone, a specific inhibitor of ABA biosynthesis, enhanced the effect of OM. Taken together, these findings suggest a role of ROS and ABA in the promotion of maize seed germination by OM under salt stress. Copyright © 2017 Elsevier Inc. All rights reserved.

Roles of a maize phytochrome-interacting factors protein ZmPIF3 in regulation of drought stress responses by controlling stomatal closure in transgenic rice without yield penalty.

PubMed

Gao, Yong; Wu, Meiqin; Zhang, Menjiao; Jiang, Wei; Liang, Enxing; Zhang, Dongping; Zhang, Changquan; Xiao, Ning; Chen, Jianmin

2018-06-05

ZmPIF3 plays an important role in ABA-mediated regulation of stomatal closure in the control of water loss, and can improve both drought tolerance and did not affect the grain yield in the transgenic rice. Phytochrome-interacting factors (PIFs) are a subfamily of basic helix-loop-helix (bHLH) transcription factors and play important roles in regulating plant growth and development. In our previous study, overexpression of a maize PIFs family gene, ZmPIF3, improved drought tolerance in transgenic rice. In this study, measurement of water loss rate, transpiration rate, stomatal conductance, guard cell aperture, density and length of ZmPIF3 transgenic plants showed that ZmPIF3 can enhance water-saving and drought-resistance by decreasing stomatal aperture and reducing transpiration in both transgenic rice and transgenic Arabidopsis. Scrutiny of sensitivity to ABA showed that ZmPIF3 transgenic rice was hypersensitive to ABA, while the endogenous ABA level was not significantly changed. These results indicate that ZmPIF3 plays a major role in the ABA signaling pathway. In addition, DGE results further suggest that ZmPIF3 participates in the ABA signaling pathway and regulates stomatal aperture in rice. Comparison analysis of the phenotype, physiology, and transcriptome of ZmPIF3 transgenic rice compared to control plants further suggests that ZmPIF3 is a positive regulator of ABA signaling and enhances water-saving and drought-resistance traits by reducing stomatal openings to control water loss. Moreover, investigation of the agronomic traits of ZmPIF3 transgenic rice from four cultivating seasons showed that ZmPIF3 expression increased the tiller and panicle number and did not affect the grain yield in the transgenic rice. These results demonstrate that ZmPIF3 is a promising candidate gene in the transgenic breeding of water-saving and drought-resistant rice plants and crop improvement.

Evolution of Abscisic Acid Synthesis and Signaling Mechanisms

PubMed Central

Hauser, Felix; Waadt, Rainer; Schroeder, Julian I.

2011-01-01

The plant hormone abscisic acid (ABA) mediates seed dormancy, controls seedling development and triggers tolerance to abiotic stresses, including drought. Core ABA signaling components consist of a recently identified group of ABA receptor proteins of the PYRABACTIN RESISTANCE (PYR)/REGULATORY COMPONENT OF ABA RECEPTOR (RCAR) family that act as negative regulators of members of the PROTEIN PHOSPHATASE 2C (PP2C) family. Inhibition of PP2C activity enables activation of SNF1-RELATED KINASE 2 (SnRK2) protein kinases, which target downstream components, including transcription factors, ion channels and NADPH oxidases. These and other components form a complex ABA signaling network. Here, an in depth analysis of the evolution of components in this ABA signaling network shows that (i) PYR/RCAR ABA receptor and ABF-type transcription factor families arose during land colonization of plants and are not found in algae and other species, (ii) ABA biosynthesis enzymes have evolved to plant- and fungal-specific forms, leading to different ABA synthesis pathways, (iii) existing stress signaling components, including PP2C phosphatases and SnRK kinases, were adapted for novel roles in this plant-specific network to respond to water limitation. In addition, evolutionarily conserved secondary structures in the PYR/RCAR ABA receptor family are visualized. PMID:21549957

Safflor yellow B suppresses angiotensin II-mediated human umbilical vein cell injury via regulation of Bcl-2/p22{sup phox} expression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chaoyun; He, Yanhao; Department of Pharmacology, Xi'an Jiaotong University School of Medicine, Key Laboratory of Environment and Genes Related to Disease, Ministry of Education, Xi'an, Shaanxi 710061

Intracellular reactive oxygen species (ROS) are derived from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Angiotensin II (Ang II) can cause endothelial dysfunction by promoting intracellular ROS generation. Safflor yellow B (SYB) effectively inhibits ROS generation by upregulating Bcl-2 expression. In this study, we examined the effects of SYB on Ang II-induced injury to human umbilical vein endothelial cells (HUVECs), and elucidated the roles of NADPH oxidase and Bcl-2. We treated cultured HUVECs with Ang II, SYB, and Bcl-2 siRNA, and determined NADPH oxidase activity and ROS levels. Furthermore, cellular and mitochondrial physiological states were evaluated, and the expression levels ofmore » target proteins were analyzed. Ang II significantly enhanced intracellular ROS levels, caused mitochondrial membrane dysfunction, and decreased cell viability, leading to apoptosis. This was associated with increased expression of AT1R and p22{sup phox}, increased NADPH oxidase activity, and an increased ratio of Bax/Bcl-2, leading to decreases in antioxidant enzyme activities, which were further strengthened after blocking Bcl-2. Compared to Ang II treatment alone, co-treatment with SYB significantly reversed HUVEC injury. Taken together, these results demonstrate that SYB could significantly protect endothelial cells from Ang II-induced cell damage, and that it does so by upregulating Bcl-2 expression and inhibiting ROS generation. - Highlights: • Angiotensin II depresses mitochondria physiological function. • Angiotensin II activates NADPH oxidase via up-regulating expresion of p22{sup phox}. • Bcl-2 plays a pivotal role in improving mitochondria function and regulates ROS level. • Inhibitor of Bcl-2 promotes angiotensin II mediated HUVEC injury. • SYB attenuates angiotensin II mediated HUVEC injury via up regulating Bcl-2 expression.« less

The core regulatory network of the abscisic acid pathway in banana: genome-wide identification and expression analyses during development, ripening, and abiotic stress.

PubMed

Hu, Wei; Yan, Yan; Shi, Haitao; Liu, Juhua; Miao, Hongxia; Tie, Weiwei; Ding, Zehong; Ding, XuPo; Wu, Chunlai; Liu, Yang; Wang, Jiashui; Xu, Biyu; Jin, Zhiqiang

2017-08-29

Abscisic acid (ABA) signaling plays a crucial role in developmental and environmental adaptation processes of plants. However, the PYL-PP2C-SnRK2 families that function as the core components of ABA signaling are not well understood in banana. In the present study, 24 PYL, 87 PP2C, and 11 SnRK2 genes were identified from banana, which was further supported by evolutionary relationships, conserved motif and gene structure analyses. The comprehensive transcriptomic analyses showed that banana PYL-PP2C-SnRK2 genes are involved in tissue development, fruit development and ripening, and response to abiotic stress in two cultivated varieties. Moreover, comparative expression analyses of PYL-PP2C-SnRK2 genes between BaXi Jiao (BX) and Fen Jiao (FJ) revealed that PYL-PP2C-SnRK2-mediated ABA signaling might positively regulate banana fruit ripening and tolerance to cold, salt, and osmotic stresses. Finally, interaction networks and co-expression assays demonstrated that the core components of ABA signaling were more active in FJ than in BX in response to abiotic stress, further supporting the crucial role of the genes in tolerance to abiotic stress in banana. This study provides new insights into the complicated transcriptional control of PYL-PP2C-SnRK2 genes, improves the understanding of PYL-PP2C-SnRK2-mediated ABA signaling in the regulation of fruit development, ripening, and response to abiotic stress, and identifies some candidate genes for genetic improvement of banana.

Role of abscisic acid in strigolactone-induced salt stress tolerance in arbuscular mycorrhizal Sesbania cannabina seedlings.

PubMed

Ren, Cheng-Gang; Kong, Cun-Cui; Xie, Zhi-Hong

2018-05-03

Strigolactones (SLs) are considered to be a novel class of phytohormone involved in plant defense responses. Currently, their relationships with other plant hormones, such as abscisic acid (ABA), during responses to salinity stress are largely unknown. In this study, the relationship between SL and ABA during the induction of H 2 O 2 - mediated tolerance to salt stress were studied in arbuscular mycorrhizal (AM) Sesbania cannabina seedlings. The SL levels increased after ABA treatments and decreased when ABA biosynthesis was inhibited in AM plants. Additionally, the expression levels of SL-biosynthesis genes in AM plants increased following treatments with exogenous ABA and H 2 O 2 . Furthermore, ABA-induced SL production was blocked by a pre-treatment with dimethylthiourea, which scavenges H 2 O 2 . In contrast, ABA production was unaffected by dimethylthiourea. Abscisic acid induced only partial and transient increases in the salt tolerance of TIS108 (a SL synthesis inhibitor) treated AM plants, whereas SL induced considerable and prolonged increases in salt tolerance after a pre-treatment with tungstate. These results strongly suggest that ABA is regulating the induction of salt tolerance by SL in AM S. cannabina seedlings.

Glutathionylation state of uncoupling protein-2 and the control of glucose-stimulated insulin secretion.

PubMed

Mailloux, Ryan J; Fu, Accalia; Robson-Doucette, Christine; Allister, Emma M; Wheeler, Michael B; Screaton, Robert; Harper, Mary-Ellen

2012-11-16

The role of reactive oxygen species (ROS) in glucose-stimulated insulin release remains controversial because ROS have been shown to both amplify and impede insulin release. In regard to preventing insulin release, ROS activates uncoupling protein-2 (UCP2), a mitochondrial inner membrane protein that negatively regulates glucose-stimulated insulin secretion (GSIS) by uncoupling oxidative phosphorylation. With our recent discovery that the UCP2-mediated proton leak is modulated by reversible glutathionylation, a process responsive to small changes in ROS levels, we resolved to determine whether glutathionylation is required for UCP2 regulation of GSIS. Using Min6 cells and pancreatic islets, we demonstrate that induction of glutathionylation not only deactivates UCP2-mediated proton leak but also enhances GSIS. Conversely, an increase in mitochondrial matrix ROS was found to deglutathionylate and activate UCP2 leak and impede GSIS. Glucose metabolism also decreased the total amount of cellular glutathionylated proteins and increased the cellular glutathione redox ratio (GSH/GSSG). Intriguingly, the provision of extracellular ROS (H(2)O(2), 10 μM) amplified GSIS and also activated UCP2. Collectively, our findings indicate that the glutathionylation status of UCP2 contributes to the regulation of GSIS, and different cellular sites and inducers of ROS can have opposing effects on GSIS, perhaps explaining some of the controversy surrounding the role of ROS in GSIS.

Glutathionylation State of Uncoupling Protein-2 and the Control of Glucose-stimulated Insulin Secretion*

PubMed Central

Mailloux, Ryan J.; Fu, Accalia; Robson-Doucette, Christine; Allister, Emma M.; Wheeler, Michael B.; Screaton, Robert; Harper, Mary-Ellen

2012-01-01

The role of reactive oxygen species (ROS) in glucose-stimulated insulin release remains controversial because ROS have been shown to both amplify and impede insulin release. In regard to preventing insulin release, ROS activates uncoupling protein-2 (UCP2), a mitochondrial inner membrane protein that negatively regulates glucose-stimulated insulin secretion (GSIS) by uncoupling oxidative phosphorylation. With our recent discovery that the UCP2-mediated proton leak is modulated by reversible glutathionylation, a process responsive to small changes in ROS levels, we resolved to determine whether glutathionylation is required for UCP2 regulation of GSIS. Using Min6 cells and pancreatic islets, we demonstrate that induction of glutathionylation not only deactivates UCP2-mediated proton leak but also enhances GSIS. Conversely, an increase in mitochondrial matrix ROS was found to deglutathionylate and activate UCP2 leak and impede GSIS. Glucose metabolism also decreased the total amount of cellular glutathionylated proteins and increased the cellular glutathione redox ratio (GSH/GSSG). Intriguingly, the provision of extracellular ROS (H2O2, 10 μm) amplified GSIS and also activated UCP2. Collectively, our findings indicate that the glutathionylation status of UCP2 contributes to the regulation of GSIS, and different cellular sites and inducers of ROS can have opposing effects on GSIS, perhaps explaining some of the controversy surrounding the role of ROS in GSIS. PMID:23035124

ABA Suppresses Root Hair Growth via the OBP4 Transcriptional Regulator1[OPEN

PubMed Central

Kawamura, Ayako; Schäfer, Sabine; Breuer, Christian; Shibata, Michitaro; Mitsuda, Nobutaka; Ohme-Takagi, Masaru; Matsui, Minami

2017-01-01

Plants modify organ growth and tune morphogenesis in response to various endogenous and environmental cues. At the cellular level, organ growth is often adjusted by alterations in cell growth, but the molecular mechanisms underlying this control remain poorly understood. In this study, we identify the DNA BINDING WITH ONE FINGER (DOF)-type transcription regulator OBF BINDING PROTEIN4 (OBP4) as a repressor of cell growth. Ectopic expression of OBP4 in Arabidopsis (Arabidopsis thaliana) inhibits cell growth, resulting in severe dwarfism and the repression of genes involved in the regulation of water transport, root hair development, and stress responses. Among the basic helix-loop-helix transcription factors known to control root hair growth, OBP4 binds the ROOT HAIR DEFECTIVE6-LIKE2 (RSL2) promoter to repress its expression. The accumulation of OBP4 proteins is detected in expanding root epidermal cells, and its expression level is increased by the application of abscisic acid (ABA) at concentrations sufficient to inhibit root hair growth. ABA-dependent induction of OBP4 is associated with the reduced expression of RSL2. Furthermore, ectopic expression of OBP4 or loss of RSL2 function results in ABA-insensitive root hair growth. Taken together, our results suggest that OBP4-mediated transcriptional repression of RSL2 contributes to the ABA-dependent inhibition of root hair growth in Arabidopsis. PMID:28167701

Transcriptional Regulation of Arabidopsis MIR168a and ARGONAUTE1 Homeostasis in Abscisic Acid and Abiotic Stress Responses1[W

PubMed Central

Li, Wei; Cui, Xiao; Meng, Zhaolu; Huang, Xiahe; Xie, Qi; Wu, Heng; Jin, Hailing; Zhang, Dabing; Liang, Wanqi

2012-01-01

The accumulation of a number of small RNAs in plants is affected by abscisic acid (ABA) and abiotic stresses, but the underlying mechanisms are poorly understood. The miR168-mediated feedback regulatory loop regulates ARGONAUTE1 (AGO1) homeostasis, which is crucial for gene expression modulation and plant development. Here, we reveal a transcriptional regulatory mechanism by which MIR168 controls AGO1 homeostasis during ABA treatment and abiotic stress responses in Arabidopsis (Arabidopsis thaliana). Plants overexpressing MIR168a and the AGO1 loss-of-function mutant ago1-27 display ABA hypersensitivity and drought tolerance, while the mir168a-2 mutant shows ABA hyposensitivity and drought hypersensitivity. Both the precursor and mature miR168 were induced under ABA and several abiotic stress treatments, but no obvious decrease for the target of miR168, AGO1, was shown under the same conditions. However, promoter activity analysis indicated that AGO1 transcription activity was increased under ABA and drought treatments, suggesting that transcriptional elevation of MIR168a is required for maintaining a stable AGO1 transcript level during the stress response. Furthermore, we showed both in vitro and in vivo that the transcription of MIR168a is directly regulated by four abscisic acid-responsive element (ABRE) binding factors, which bind to the ABRE cis-element within the MIR168a promoter. This ABRE motif is also found in the promoter of MIR168a homologs in diverse plant species. Our findings suggest that transcriptional regulation of miR168 and posttranscriptional control of AGO1 homeostasis may play an important and conserved role in stress response and signal transduction in plants. PMID:22247272

Transcriptional regulation of Arabidopsis MIR168a and argonaute1 homeostasis in abscisic acid and abiotic stress responses.

PubMed

Li, Wei; Cui, Xiao; Meng, Zhaolu; Huang, Xiahe; Xie, Qi; Wu, Heng; Jin, Hailing; Zhang, Dabing; Liang, Wanqi

2012-03-01

The accumulation of a number of small RNAs in plants is affected by abscisic acid (ABA) and abiotic stresses, but the underlying mechanisms are poorly understood. The miR168-mediated feedback regulatory loop regulates ARGONAUTE1 (AGO1) homeostasis, which is crucial for gene expression modulation and plant development. Here, we reveal a transcriptional regulatory mechanism by which MIR168 controls AGO1 homeostasis during ABA treatment and abiotic stress responses in Arabidopsis (Arabidopsis thaliana). Plants overexpressing MIR168a and the AGO1 loss-of-function mutant ago1-27 display ABA hypersensitivity and drought tolerance, while the mir168a-2 mutant shows ABA hyposensitivity and drought hypersensitivity. Both the precursor and mature miR168 were induced under ABA and several abiotic stress treatments, but no obvious decrease for the target of miR168, AGO1, was shown under the same conditions. However, promoter activity analysis indicated that AGO1 transcription activity was increased under ABA and drought treatments, suggesting that transcriptional elevation of MIR168a is required for maintaining a stable AGO1 transcript level during the stress response. Furthermore, we showed both in vitro and in vivo that the transcription of MIR168a is directly regulated by four abscisic acid-responsive element (ABRE) binding factors, which bind to the ABRE cis-element within the MIR168a promoter. This ABRE motif is also found in the promoter of MIR168a homologs in diverse plant species. Our findings suggest that transcriptional regulation of miR168 and posttranscriptional control of AGO1 homeostasis may play an important and conserved role in stress response and signal transduction in plants.

Exogenous strigolactone interacts with abscisic acid-mediated accumulation of anthocyanins in grapevine berries.

PubMed

Ferrero, Manuela; Pagliarani, Chiara; Novák, Ondrej; Ferrandino, Alessandra; Cardinale, Francesca; Visentin, Ivan; Schubert, Andrea

2018-04-23

Besides signalling to soil organisms, strigolactones (SLs) control above- and below-ground morphology, in particular shoot branching. Furthermore, SLs interact with stress responses, possibly thanks to a crosstalk with the abscisic acid (ABA) signal. In grapevine (Vitis vinifera L.), ABA drives the accumulation of anthocyanins over the ripening season. In this study, we investigated the effects of treatment with a synthetic strigolactone analogue, GR24, on anthocyanin accumulation in grape berries, in the presence or absence of exogenous ABA treatment. Experiments were performed both on severed, incubated berries, and on berries attached to the vine. Furthermore, we analysed the corresponding transcript concentrations of genes involved in anthocyanin biosynthesis, and in ABA biosynthesis, metabolism, and membrane transport. During the experiment time courses, berries showed the expected increase in soluble sugars and anthocyanins. GR24 treatment had no or little effect on anthocyanin accumulation, or on gene expression levels. Exogenous ABA treatment activated soluble sugar and anthocyanin accumulation, and enhanced expression of anthocyanin and ABA biosynthetic genes, and that of genes involved in ABA hydroxylation and membrane transport. Co-treatment of GR24 with ABA delayed anthocyanin accumulation, decreased expression of anthocyanin biosynthetic genes, and negatively affected ABA concentration. GR24 also enhanced the ABA-induced activation of ABA hydroxylase genes, while it down-regulated the ABA-induced activation of ABA transport genes. Our results show that GR24 affects the ABA-induced activation of anthocyanin biosynthesis in this non-climacteric fruit. We discuss possible mechanisms underlying this effect, and the potential role of SLs in ripening of non-ABA-treated berries.

Computational prediction and experimental verification of HVA1-like abscisic acid responsive promoters in rice (Oryza sativa).

PubMed

Ross, Christian; Shen, Qingxi J

2006-09-01

Abscisic acid (ABA) is one of the central plant hormones, responsible for controlling both maturation and germination in seeds, as well as mediating adaptive responses to desiccation, injury, and pathogen infection in vegetative tissues. Thorough analyses of two barley genes, HVA1 and HVA22, indicate that their response to ABA relies on the interaction of two cis-acting elements in their promoters, an ABA response element (ABRE) and a coupling element (CE). Together, they form an ABA response promoter complex (ABRC). Comparison of promoters of barley HVA1 and it rice orthologue indicates that the structures and sequences of their ABRCs are highly similar. Prediction of ABA responsive genes in the rice genome is then tractable to a bioinformatics approach based on the structures of the well-defined barley ABRCs. Here we describe a model developed based on the consensus, inter-element spacing and orientations of experimentally determined ABREs and CEs. Our search of the rice promoter database for promoters that fit the model has generated a partial list of genes in rice that have a high likelihood of being involved in the ABA signaling network. The ABA inducibility of some of the rice genes identified was validated with quantitative reverse transcription PCR (QPCR). By limiting our input data to known enhancer modules and experimentally derived rules, we have generated a high confidence subset of ABA-regulated genes. The results suggest that the pathways by which cereals respond to biotic and abiotic stresses overlap significantly, and that regulation is not confined to the level transcription. The large fraction of putative regulatory genes carrying HVA1-like enhancer modules in their promoters suggests the ABA signal enters at multiple points into a complex regulatory network that remains largely unmapped.

Key Role of ROS in the Process of 15-Lipoxygenase/15-Hydroxyeicosatetraenoiccid-Induced Pulmonary Vascular Remodeling in Hypoxia Pulmonary Hypertension

PubMed Central

Qiu, Yanli; Liu, Gaofeng; Sheng, Tingting; Yu, Xiufeng; Wang, Shuang; Zhu, Daling

2016-01-01

We previously reported that 15-lipoxygenase (15-LO) and its metabolite 15-hydroxyeicosatetraenoic acid (15-HETE) were up-regulated in pulmonary arterial cells from both pulmonary artery hypertension patients and hypoxic rats and that these factors mediated the progression of pulmonary hypertension (PH) by affecting the proliferation and apoptosis of pulmonary arterial (PA) cells. However, the underlying mechanisms of the remodeling induced by 15-HETE have remained unclear. As reactive oxygen species (ROS) and 15-LO are both induced by hypoxia, it is possible that ROS are involved in the events of hypoxia-induced 15-LO expression that lead to PH. We employed immunohistochemistry, tube formation assays, bromodeoxyuridine (BrdU) incorporation assays, and cell cycle analyses to explore the role of ROS in the process of 15-HETE-mediated hypoxic pulmonary hypertension (HPH). We found that exogenous 15-HETE facilitated the generation of ROS and that this effect was mainly localized to mitochondria. In particular, the mitochondrial electron transport chain and nicotinamide-adenine dinucleotide phosphate oxidase 4 (Nox4) were responsible for the significant 15-HETE-stimulated increase in ROS production. Moreover, ROS induced by 15-HETE stimulated endothelial cell (EC) migration and promoted pulmonary artery smooth muscle cell (PASMC) proliferation under hypoxia via the p38 MAPK pathway. These results indicated that 15-HETE-regulated ROS mediated hypoxia-induced pulmonary vascular remodeling (PVR) via the p38 MAPK pathway. PMID:26871724

The influence of abscisic acid on the ethylene biosynthesis pathway in the functioning of the flower abscission zone in Lupinus luteus.

PubMed

Wilmowicz, Emilia; Frankowski, Kamil; Kućko, Agata; Świdziński, Michał; de Dios Alché, Juan; Nowakowska, Anna; Kopcewicz, Jan

2016-11-01

Flower abscission is a highly regulated developmental process activated in response to exogenous (e.g. changing environmental conditions) and endogenous stimuli (e.g. phytohormones). Ethylene (ET) and abscisic acid (ABA) are very effective stimulators of flower abortion in Lupinus luteus, which is a widely cultivated species in Poland, Australia and Mediterranean countries. In this paper, we show that artificial activation of abscission by flower removal caused an accumulation of ABA in the abscission zone (AZ). Moreover, the blocking of that phytohormone's biosynthesis by NDGA (nordihydroguaiaretic acid) decreased the number of abscised flowers. However, the application of NBD - an inhibitor of ET action - reversed the stimulatory effect of ABA on flower abscission, indicating that ABA itself is not sufficient to turn on the organ separation. Our analysis revealed that exogenous ABA significantly accelerated the transcriptional activity of the ET biosynthesis genes ACC synthase (LlACS) and oxidase (LlACO), and moreover, strongly increased the level of 1-aminocyclopropane-1-carboxylic acid (ACC) - ET precursor, which was specifically localized within AZ cells. We cannot exclude the possibility that ABA mediates flower abscission processes by enhancing the ET biosynthesis rate. The findings of our study will contribute to the overall basic knowledge on the phytohormone-regulated generative organs abscission in L. luteus. Copyright © 2016 Elsevier GmbH. All rights reserved.

The Plant Cuticle Is Required for Osmotic Stress Regulation of Abscisic Acid Biosynthesis and Osmotic Stress Tolerance in Arabidopsis[W

PubMed Central

Wang, Zhen-Yu; Xiong, Liming; Li, Wenbo; Zhu, Jian-Kang; Zhu, Jianhua

2011-01-01

Osmotic stress activates the biosynthesis of abscisic acid (ABA). One major step in ABA biosynthesis is the carotenoid cleavage catalyzed by a 9-cis epoxycarotenoid dioxygenase (NCED). To understand the mechanism for osmotic stress activation of ABA biosynthesis, we screened for Arabidopsis thaliana mutants that failed to induce the NCED3 gene expression in response to osmotic stress treatments. The ced1 (for 9-cis epoxycarotenoid dioxygenase defective 1) mutant isolated in this study showed markedly reduced expression of NCED3 in response to osmotic stress (polyethylene glycol) treatments compared with the wild type. Other ABA biosynthesis genes are also greatly reduced in ced1 under osmotic stress. ced1 mutant plants are very sensitive to even mild osmotic stress. Map-based cloning revealed unexpectedly that CED1 encodes a putative α/β hydrolase domain-containing protein and is allelic to the BODYGUARD gene that was recently shown to be essential for cuticle biogenesis. Further studies discovered that other cutin biosynthesis mutants are also impaired in osmotic stress induction of ABA biosynthesis genes and are sensitive to osmotic stress. Our work demonstrates that the cuticle functions not merely as a physical barrier to minimize water loss but also mediates osmotic stress signaling and tolerance by regulating ABA biosynthesis and signaling. PMID:21610183

Overlapping and distinct roles of AKIN10 and FUSCA3 in ABA and sugar signaling during seed germination

PubMed Central

Tsai, Allen Yi-Lun; Gazzarrini, Sonia

2012-01-01

The Arabidopsis B3-domain transcription factor FUSCA3 (FUS3) is a master regulator of seed maturation and also a central modulator of hormonal responses during late embryogenesis and germination. Recently, we have identified AKIN10, the Arabidopsis ortholog of Snf1 (Sucrose Non-Fermenting-1)–Related Kinase1 (SnRK1), as a FUS3-interacting protein. We demonstrated that AKIN10 physically interacts with and phosphorylates FUS3 at its N-terminal region, and genetically interacts with FUS3 to regulate developmental phase transition and lateral organ growth. Snf1/AMPK/SnRK1 kinases are important sensors of the cellular energy level, and they are activated in response to starvation and cellular stress. Here we present findings that indicate FUS3 and AKIN10 functionally overlap in ABA signaling, but play different roles in sugar responses during germination. Seeds overexpressing FUS3 and AKIN10 both display ABA-hypersensitivity and delayed germination. The latter is partly dependent on de novo ABA synthesis in both genotypes, as delayed germination can be partially rescued by the ABA biosynthesis inhibitor, fluridone. However, seeds and seedlings overexpressing FUS3 and AKIN10 show different sugar responses. AKIN10-overexpressing seeds and seedlings are hypersensitive to glucose, while those overexpressing FUS3 display overall defects in osmotic stress, primarily during seedling growth, as they show increased sensitivity toward sorbitol and glucose. Hypersensitivity to sugar and/or osmotic stress during germination are partly dependent on de novo ABA synthesis for both genotypes, although are likely to act through distinct pathways. This data suggests that AKIN10 and FUS3 both act as positive regulators of seed responses to ABA, and that AKIN10 regulates sugar signaling while FUS3 mediates osmotic stress responses. PMID:22902692

Interaction Between ABA Signaling and Copper Homeostasis in Arabidopsis thaliana.

PubMed

Carrió-Seguí, Àngela; Romero, Paco; Sanz, Amparo; Peñarrubia, Lola

2016-07-01

ABA is involved in plant responses to non-optimal environmental conditions, including nutrient availability. Since copper (Cu) is a very important micronutrient, unraveling how ABA affects Cu uptake and distribution is relevant to ensure adequate Cu nutrition in plants subjected to stress conditions. Inversely, knowledge about how the plant nutritional status can interfere with ABA biosynthesis and signaling mechanisms is necessary to optimize stress tolerance in horticultural crops. Here the reciprocal influence between ABA and Cu content was addressed by using knockout mutants and overexpressing transgenic plants of high affinity plasma membrane Cu transporters (pmCOPT) with altered Cu uptake. Exogenous ABA inhibited pmCOPT expression and drastically modified COPT2-driven localization in roots. ABA regulated SPL7, the main transcription factor responsive for Cu deficiency responses, and subsequently affected expression of its targets. ABA biosynthesis (aba2) and signaling (hab1-1 abi1-2) mutants differentially responded to ABA according to Cu levels. Alteration of Cu homeostasis in the pmCOPT mutants affected ABA biosynthesis, transport and signaling as genes such as NCED3, WRKY40, HY5 and ABI5 were differentially modulated by Cu status, and also in the pmCOPT and ABA mutants. Altered Cu uptake resulted in modified plant sensitivity to salt-mediated increases in endogenous ABA. The overall results provide evidence for reciprocal cross-talk between Cu status and ABA metabolism and signaling. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Arabidopsis C3HC4-RING finger E3 ubiquitin ligase AtAIRP4 positively regulates stress-responsive abscisic acid signaling.

PubMed

Yang, Liang; Liu, Qiaohong; Liu, Zhibin; Yang, Hao; Wang, Jianmei; Li, Xufeng; Yang, Yi

2016-01-01

Degradation of proteins via the ubiquitin system is an important step in many stress signaling pathways in plants. E3 ligases recognize ligand proteins and dictate the high specificity of protein degradation, and thus, play a pivotal role in ubiquitination. Here, we identified a gene, named Arabidopsis thaliana abscisic acid (ABA)-insensitive RING protein 4 (AtAIRP4), which is induced by ABA and other stress treatments. AtAIRP4 encodes a cellular protein with a C3HC4-RING finger domain in its C-terminal side, which has in vitro E3 ligase activity. Loss of AtAIRP4 leads to a decrease in sensitivity of root elongation and stomatal closure to ABA, whereas overexpression of this gene in the T-DNA insertion mutant atairp4 effectively recovered the ABA-associated phenotypes. AtAIRP4 overexpression plants were hypersensitive to salt and osmotic stresses during seed germination, and showed drought avoidance compared with the wild-type and atairp4 mutant plants. In addition, the expression levels of ABA- and drought-induced marker genes in AtAIRP4 overexpression plants were markedly higher than those in the wild-type and atairp4 mutant plants. Hence, these results indicate that AtAIRP4 may act as a positive regulator of ABA-mediated drought avoidance and a negative regulator of salt tolerance in Arabidopsis. © 2015 The Authors. Journal of Integrative Plant Biology published by Wiley Publishing Asia Pty Ltd on behalf of Institute of Botany, Chinese Academy of Sciences.

MET18 Connects the Cytosolic Iron-Sulfur Cluster Assembly Pathway to Active DNA Demethylation in Arabidopsis

PubMed Central

Tang, Kai; Zhang, Huiming; Mangrauthia, Satendra K.; Lei, Mingguang; Hsu, Chuan-Chih; Hou, Yueh-Ju; Wang, Chunguo; Li, Yan; Tao, W. Andy; Zhu, Jian-Kang

2015-01-01

DNA demethylation mediated by the DNA glycosylase ROS1 helps determine genomic DNA methylation patterns and protects active genes from being silenced. However, little is known about the mechanism of regulation of ROS1 enzymatic activity. Using a forward genetic screen, we identified an anti-silencing (ASI) factor, ASI3, the dysfunction of which causes transgene promoter hyper-methylation and silencing. Map-based cloning identified ASI3 as MET18, a component of the cytosolic iron-sulfur cluster assembly (CIA) pathway. Mutation in MET18 leads to hyper-methylation at thousands of genomic loci, the majority of which overlap with hypermethylated loci identified in ros1 and ros1dml2dml3 mutants. Affinity purification followed by mass spectrometry indicated that ROS1 physically associates with MET18 and other CIA components. Yeast two-hybrid and split luciferase assays showed that ROS1 can directly interact with MET18 and another CIA component, AE7. Site-directed mutagenesis of ROS1 indicated that the conserved iron-sulfur motif is indispensable for ROS1 enzymatic activity. Our results suggest that ROS1-mediated active DNA demethylation requires MET18-dependent transfer of the iron-sulfur cluster, highlighting an important role of the CIA pathway in epigenetic regulation. PMID:26492035

Reactive Oxygen Species Function to Mediate the Fe Deficiency Response in an Fe-Efficient Apple Genotype: An Early Response Mechanism for Enhancing Reactive Oxygen Production.

PubMed

Sun, Chaohua; Wu, Ting; Zhai, Longmei; Li, Duyue; Zhang, Xinzhong; Xu, Xuefeng; Ma, Huiqin; Wang, Yi; Han, Zhenhai

2016-01-01

Reactive oxygen species (ROS) are important signaling molecules in plants that contribute to stress acclimation. This study demonstrated that ROS play a critical role in Fe deficiency-induced signaling at an early stage in Malus xiaojinensis . Once ROS production has been initiated, prolonged Fe starvation leads to activation of ROS scavenging mechanisms. Further, we demonstrated that ROS scavengers are involved in maintaining the cellular redox homeostasis during prolonged Fe deficiency treatment. Taken together, our results describe a feedback repression loop for ROS to preserve redox homeostasis and maintain a continuous Fe deficiency response in the Fe-efficient woody plant M. xiaojinensis . More broadly, this study reveals a new mechanism in which ROS mediate both positive and negative regulation of plant responses to Fe deficiency stress.

Quantitative proteomics-based analysis supports a significant role of GTG proteins in regulation of ABA response in Arabidopsis roots.

PubMed

Alvarez, Sophie; Roy Choudhury, Swarup; Hicks, Leslie M; Pandey, Sona

2013-03-01

Abscisic acid (ABA) is proposed to be perceived by multiple receptors in plants. We have previously reported on the role of two GPCR-type G-proteins (GTG proteins) as plasma membrane-localized ABA receptors in Arabidopsis thaliana. However, due to the presence of multiple transmembrane domains, detailed structural and biochemical characterization of GTG proteins remains limited. Since ABA induces substantial changes in the proteome of plants, a labeling LC-based quantitative proteomics approach was applied to elucidate the global effects and possible downstream targets of GTG1/GTG2 proteins. Quantitative differences in protein abundance between wild-type and gtg1gtg2 were analyzed for evaluation of the effect of ABA on the root proteome and its dependence on the presence of functional GTG1/GTG2 proteins. The results presented in this study reveal the most comprehensive ABA-responsive root proteome reported to date in Arabidopsis. Notably, the majority of ABA-responsive proteins required the presence of GTG proteins, supporting their key role in ABA signaling. These observations were further confirmed by additional experiments. Overall, comparison of the ABA-dependent protein abundance changes in wild-type versus gtg1gtg2 provides clues to their possible links with some of the well-established effectors of the ABA signaling pathways and their role in mediating phytohormone cross-talk.

Grape seed extract triggers apoptosis in Caco-2 human colon cancer cells through reactive oxygen species and calcium increase: extracellular signal-regulated kinase involvement.

PubMed

Dinicola, Simona; Mariggiò, Maria Addolorata; Morabito, Caterina; Guarnieri, Simone; Cucina, Alessandra; Pasqualato, Alessia; D'Anselmi, Fabrizio; Proietti, Sara; Coluccia, Pierpaolo; Bizzarri, Mariano

2013-09-14

Grape seed extract (GSE) from Italia, Palieri and Red Globe cultivars inhibits cell growth and induces apoptosis in Caco-2 human colon cancer cells in a dose-dependent manner. In order to investigate the mechanism(s) supporting the apoptotic process, we analysed reactive oxygen species (ROS) production, intracellular Ca2+ handling and extracellular signal-regulated kinase (ERK) activation. Upon exposure to GSE, ROS and intracellular Ca2+ levels increased in Caco-2 cells, concomitantly with ERK inactivation. As ERK activity is thought to be essential for promoting survival pathways, inhibition of this kinase is likely to play a relevant role in GSE-mediated anticancer effects. Indeed, pretreatment with N-acetyl cysteine, a ROS scavenger, reversed GSE-induced apoptosis, and promoted ERK phosphorylation. This effect was strengthened by ethylene glycol tetraacetic acid-mediated inhibition of extracellular Ca2+ influx. ROS and Ca2+ influx inhibition, in turn, increased ERK phosphorylation, and hence almost entirely suppressed GSE-mediated apoptosis. These data suggested that GSE triggers a previously unrecognised ERK-based mechanism, involving both ROS production and intracellular Ca2+ increase, eventually leading to apoptosis in cancer cells.

Quantitative phosphoproteomics identifies SnRK2 protein kinase substrates and reveals the effectors of abscisic acid action.

PubMed

Wang, Pengcheng; Xue, Liang; Batelli, Giorgia; Lee, Shinyoung; Hou, Yueh-Ju; Van Oosten, Michael J; Zhang, Huiming; Tao, W Andy; Zhu, Jian-Kang

2013-07-02

Sucrose nonfermenting 1 (SNF1)-related protein kinase 2s (SnRK2s) are central components of abscisic acid (ABA) signaling pathways. The snrk2.2/2.3/2.6 triple-mutant plants are nearly completely insensitive to ABA, suggesting that most of the molecular actions of ABA are triggered by the SnRK2s-mediated phosphorylation of substrate proteins. Only a few substrate proteins of the SnRK2s are known. To identify additional substrate proteins of the SnRK2s and provide insight into the molecular actions of ABA, we used quantitative phosphoproteomics to compare the global changes in phosphopeptides in WT and snrk2.2/2.3/2.6 triple mutant seedlings in response to ABA treatment. Among the 5,386 unique phosphorylated peptides identified in this study, we found that ABA can increase the phosphorylation of 166 peptides and decrease the phosphorylation of 117 peptides in WT seedlings. In the snrk2.2/2.3/2.6 triple mutant, 84 of the 166 peptides, representing 58 proteins, could not be phosphorylated, or phosphorylation was not increased under ABA treatment. In vitro kinase assays suggest that most of the 58 proteins can serve as substrates of the SnRK2s. The SnRK2 substrates include proteins involved in flowering time regulation, RNA and DNA binding, miRNA and epigenetic regulation, signal transduction, chloroplast function, and many other cellular processes. Consistent with the SnRK2 phosphorylation of flowering time regulators, the snrk2.2/2.3/2.6 triple mutant flowered significantly earlier than WT. These results shed new light on the role of the SnRK2 protein kinases and on the downstream effectors of ABA action, and improve our understanding of plant responses to adverse environments.

A gate-latch-lock mechanism for hormone signalling by abscisic acid receptors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melcher, Karsten; Ng, Ley-Moy; Zhou, X Edward

2010-01-12

Abscisic acid (ABA) is a ubiquitous hormone that regulates plant growth, development and responses to environmental stresses. Its action is mediated by the PYR/PYL/RCAR family of START proteins, but it remains unclear how these receptors bind ABA and, in turn, how hormone binding leads to inhibition of the downstream type 2C protein phosphatase (PP2C) effectors. Here we report crystal structures of apo and ABA-bound receptors as well as a ternary PYL2-ABA-PP2C complex. The apo receptors contain an open ligand-binding pocket flanked by a gate that closes in response to ABA by way of conformational changes in two highly conserved β-loopsmore » that serve as a gate and latch. Moreover, ABA-induced closure of the gate creates a surface that enables the receptor to dock into and competitively inhibit the PP2C active site. A conserved tryptophan in the PP2C inserts directly between the gate and latch, which functions to further lock the receptor in a closed conformation. Together, our results identify a conserved gate-latch-lock mechanism underlying ABA signalling.« less

Rosmarinic acid counteracts activation of hepatic stellate cells via inhibiting the ROS-dependent MMP-2 activity: Involvement of Nrf2 antioxidant system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Changfang; Zou, Yu; Liu, Yuzhang

Recently, oxidative stress is involved in hepatofibrogenesis. Matrix metalloproteinase-2 (MMP-2) is required for activation of hepatic stellate cells (HSCs) in response to reactive oxygen species (ROS). This study was designed to explore the hypothesis that the inhibitory effect of rosmarinic acid (RA) on HSCs activation might mainly result from its antioxidant capability by increasing the synthesis of glutathione (GSH) involved in nuclear factor kappa B (NF-κB)-dependent inhibition of MMP-2 activity. Here, we demonstrate that RA reverses activated HSCs to quiescent cells. Concomitantly, RA inhibits MMP-2 activity. RNA interference-imposed knockdown of NF-κB abolished down-regulation of MMP-2 by RA. RA-mediated inactivation ofmore » NF-κB could be blocked by the diphenyleneiodonium chloride (DPI; a ROS inhibitor). Conversely, transfection of dominant-negative (DN) mutant of extracellular signal-regulated kinases 2 (ERK2), c-Jun N-terminal kinase 1 (JNK1), or p38α kinase had no such effect. Simultaneously, RA suppresses ROS generation and lipid peroxidation (LPO) whereas increases cellular GSH in HSC-T6 cells. Furthermore, RA significantly increased antioxidant response element (ARE)-mediated luciferase activity, nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and catalytic subunits from glutamate cysteine ligase (GCLc) expression, but not modulatory subunits from GCL (GCLm). RA-mediated up-regulation of GClc is inhibited by the shRNA-induced Nrf2 knockdown. The knocking down of Nrf2 or buthionine sulfoximine (a GCL inhibitor) abolished RA-mediated inhibition of ROS. Collectively, these results provide novel insights into the mechanisms of RA as an antifibrogenic candidate in the prevention and treatment of liver fibrosis. - Highlights: • RA reverses activated HSCs to quiescent cells. • RA suppresses MMP-2 activity through a NF-κB-dependent pathway. • Inhibition of oxidative stress by RA is dependent on nuclear translocation of Nrf2. • RA-mediated down-regulation of MMP-2 was ROS-dependent.« less

Increased abscisic acid levels in transgenic maize overexpressing AtLOS5 mediated root ion fluxes and leaf water status under salt stress

PubMed Central

Zhang, Juan; Yu, Haiyue; Zhang, Yushi; Wang, Yubing; Li, Maoying; Zhang, Jiachang; Duan, Liusheng; Zhang, Mingcai; Li, Zhaohu

2016-01-01

Abscisic acid (ABA) is a vital cellular signal in plants, and effective ABA signalling is pivotal for stress tolerance. AtLOS5 encoding molybdenum cofactor sulphurase is a key regulator of ABA biosynthesis. Here, transgenic AtLOS5 plants were generated to explore the role of AtLOS5 in salt tolerance in maize. AtLOS5 overexpression significantly up-regulated the expression of ZmVp14-2, ZmAO, and ZmMOCO, and increased aldehyde oxidase activities, which enhanced ABA accumulation in transgenic plants under salt stress. Concurrently, AtLOS5 overexpression induced the expression of ZmNHX1, ZmCBL4, and ZmCIPK16, and enhanced the root net Na+ efflux and H+ influx, but decreased net K+ efflux, which maintained a high cytosolic K+/Na+ ratio in transgenic plants under salt stress. However, amiloride or sodium orthovanadate could significantly elevate K+ effluxes and decrease Na+ efflux and H+ influx in salt-treated transgenic roots, but the K+ effluxes were inhibited by TEA, suggesting that ion fluxes regulated by AtLOS5 overexpression were possibly due to activation of Na+/H+ antiport and K+ channels across the plasma membrane. Moreover, AtLOS5 overexpression could up-regulate the transcripts of ZmPIP1:1, ZmPIP1:5, and ZmPIP2:4, and enhance root hydraulic conductivity. Thus transgenic plants had higher leaf water potential and turgor, which was correlated with greater biomass accumulation under salt stress. Thus AtLOS5 overexpression induced the expression of ABA biosynthetic genes to promote ABA accumulation, which activated ion transporter and PIP aquaporin gene expression to regulate root ion fluxes and water uptake, thus maintaining high cytosolic K+ and Na+ homeostasis and better water status in maize exposed to salt stress. PMID:26743432

Seed dormancy and ABA signaling

PubMed Central

del Carmen Rodríguez-Gacio, María; Matilla-Vázquez, Miguel A

2009-01-01

The seed is an important organ in higher plants, it is an important organ for plant survival and species dispersion. The transition between seed dormancy and germination represents a critical stage in the plant life cycle and it is an important ecological and commercial trait. A dynamic balance of synthesis and catabolism of two antagonistic hormones, abscisic acid (ABA) and giberellins (GAs), controls the equilibrium between seed dormancy and germination. Embryonic ABA plays a central role in induction and maintenance of seed dormancy and also inhibits the transition from embryonic to germination growth. Therefore, the ABA metabolism must be highly regulated at both temporal and spatial levels during phase of dessication tolerance. On the other hand, the ABA levels do not depend exclusively on the seeds because sometimes it becomes a strong sink and imports it from the roots and rhizosphere through the xylem and/or phloem. These events are discussed in depth here. Likewise, the role of some recently characterized genes belonging to seeds of woody species and related to ABA signaling are also included. Finally, although four possible ABA receptors have been reported, not much is known about how they mediate ABA signaling transduction. However, new publications seem to show that almost all these receptors lack several properties to consider them as such. PMID:19875942

Ligand-activated PPARδ inhibits UVB-induced senescence of human keratinocytes via PTEN-mediated inhibition of superoxide production.

PubMed

Ham, Sun Ah; Hwang, Jung Seok; Yoo, Taesik; Lee, Hanna; Kang, Eun Sil; Park, Chankyu; Oh, Jae-Wook; Lee, Hoon Taek; Min, Gyesik; Kim, Jin-Hoi; Seo, Han Geuk

2012-05-15

UV radiation-mediated photodamage to the skin has been implicated in premature aging and photoaging-related skin cancer and melanoma. Little is known about the cellular events that underlie premature senescence, or how to impede these events. In the present study we demonstrate that PPARδ (peroxisome-proliferator-activated receptor δ) regulates UVB-induced premature senescence of normal keratinocytes. Activation of PPARδ by GW501516, a specific ligand of PPARδ, significantly attenuated UVB-mediated generation of ROS (reactive oxygen species) and suppressed senescence of human keratinocytes. Ligand-activated PPARδ up-regulated the expression of PTEN (phosphatase and tensin homologue deleted on chromosome 10) and suppressed the PI3K (phosphatidylinositol 3-kinase)/Akt pathway. Concomitantly, translocation of Rac1 to the plasma membrane, which leads to the activation of NADPH oxidases and generation of ROS, was significantly attenuated. siRNA (small interfering RNA)-mediated knockdown of PTEN abrogated the effects of PPARδ on cellular senescence, on PI3K/Akt/Rac1 signalling and on generation of ROS in keratinocytes exposed to UVB. Finally, when HR-1 hairless mice were treated with GW501516 before exposure to UVB, the number of senescent cells in the skin was significantly reduced. Thus ligand-activated PPARδ confers resistance to UVB-induced cellular senescence by up-regulating PTEN and thereby modulating PI3K/Akt/Rac1 signalling to reduce ROS generation in keratinocytes.

Hormonal regulation of gluconeogenesis in cereal aleurone is strongly cultivar-dependent and gibberellin action involves SLENDER1 but not GAMYB.

PubMed

Eastmond, Peter J; Jones, Russell L

2005-11-01

Storage oil is a major constituent in the cereal aleurone layer. The aim of this study was to investigate how gibberellin (GA) and abscisic acid (ABA) regulate conversion of oil to sugar in barley aleurone. The activity of the glyoxylate cycle enzyme isocitrate lyase (ICL) was surveyed in eight barley cultivars. Surprisingly, some cultivars do not require GA for the induction of ICL (e.g. Himalaya), whereas some do (e.g. Golden Promise). Furthermore, in Golden Promise, GA also stimulates triacylglycerol breakdown and enhances the net flux of carbon from acetate to sugar. In contrast, ABA strongly represses ICL activity and the flux of carbon from oil to sugar in both Golden Promise and Himalaya. Biolistics using a promoter reporter showed that GA and ABA regulate ICL at the level of transcription. Studies using barley and rice mutants and pharmacological agents show that GA-dependent induction of ICL activity is mediated by SLENDER1 and requires cGMP, but does not involve the transcription factor GAMYB. Gibberellin and ABA therefore act antagonistically to regulate gluconeogenesis in the aleurone layer as well as controlling the production and secretion of hydrolases into the starchy endosperm. We suggest that the variation between different barley cultivars might be a result of selective breeding to alter seed dormancy.

Hyperglycemia regulates TXNIP/TRX/ROS axis via p38 MAPK and ERK pathways in pancreatic cancer.

PubMed

Li, Wei; Wu, Zheng; Ma, Qingyong; Liu, Jiangbo; Xu, Qinhong; Han, Liang; Duan, Wanxing; Lv, Yunfu; Wang, Fengfei; Reindl, Katie M; Wu, Erxi

2014-01-01

Approximately 85% of pancreatic cancer patients suffer from glucose intolerance or even diabetes because high glucose levels can contribute to oxidative stress which promotes tumor development. As one of the reactive oxygen species (ROS)-regulating factors, thioredoxin-interacting protein (TXNIP), is involved in the maintenance of thioredoxin (TRX)-mediated redox regulation. In this study, we demonstrated that high glucose levels increased the expression of TXNIP in time- and concentration-dependent manners and modulated the activity of TRX and ROS production in pancreatic cancer cells, BxPC-3 and Panc-1. We also found that glucose activated both p38 MAPK and ERK pathways and inhibitors of these pathways impaired the TXNIP/TRX/ROS axis. Knockdown of TXNIP restored TRX activity and decreased ROS production under high glucose conditions. Moreover, we observed that the integrated optical density (IOD) of TXNIP staining as well as the protein and mRNA expression levels of TXNIP were higher in the tumor tissues of pancreatic cancer patients with diabetes. Taken together, these results indicate that hyperglycemia-induced TXNIP expression is involved in diabetes-mediated oxidative stress in pancreatic cancer via p38 MAPK and ERK pathways.

LeMYC2 acts as a negative regulator of blue light mediated photomorphogenic growth, and promotes the growth of adult tomato plants

PubMed Central

2014-01-01

Background Arabidopsis ZBF1/MYC2bHLH transcription factor is a repressor of photomorphogenesis, and acts as a point of cross talk in light, abscisic acid (ABA) and jasmonic acid (JA) signaling pathways. MYC2 also functions as a positive regulator of lateral root development and flowering time under long day conditions. However, the function of MYC2 in growth and development remains unknown in crop plants. Results Here, we report the functional analyses of LeMYC2 in tomato (Lycopersicon esculentum). The amino acid sequence of LeMYC2 showed extensive homology with Arabidopsis MYC2, containing the conserved bHLH domain. To study the function of LeMYC2 in tomato, overexpression and RNA interference (RNAi) LeMYC2 tomato transgenic plants were generated. Examination of seedling morphology, physiological responses and light regulated gene expression has revealed that LeMYC2 works as a negative regulator of blue light mediated photomorphogenesis. Furthermore, LeMYC2 specifically binds to the G-box of LeRBCS-3A promoter. Overexpression of LeMYC2 has led to increased root length with more number of lateral roots. The tomato plants overexpressing LeMYC2 have reduced internode distance with more branches, and display the opposite morphology to RNAi transgenic lines. Furthermore, this study shows that LeMYC2 promotes ABA and JA responsiveness. Conclusions Collectively, this study highlights that working in light, ABA and JA signaling pathways LeMYC2 works as an important regulator for growth and development in tomato plants. PMID:24483714

Sinapic acid or its derivatives interfere with abscisic acid homeostasis during Arabidopsis thaliana seed germination.

PubMed

Bi, Baodi; Tang, Jingliang; Han, Shuang; Guo, Jinggong; Miao, Yuchen

2017-06-06

Sinapic acid and its esters have broad functions in different stages of seed germination and plant development and are thought to play a role in protecting against ultraviolet irradiation. To better understand the interactions between sinapic acid esters and seed germination processes in response to various stresses, we analyzed the role of the plant hormone abscisic acid (ABA) in the regulation of sinapic acid esters involved in seed germination and early seedling growth. We found that exogenous sinapic acid promotes seed germination in a dose-dependent manner in Arabidopsis thaliana. High-performance liquid chromatography mass spectrometry analysis showed that exogenous sinapic acid increased the sinapoylcholine content of imbibed seeds. Furthermore, sinapic acid affected ABA catabolism, resulting in reduced ABA levels and increased levels of the ABA-glucose ester. Using mutants deficient in the synthesis of sinapate esters, we showed that the germination of mutant sinapoylglucose accumulator 2 (sng2) and bright trichomes 1 (brt1) seeds was more sensitive to ABA than the wild-type. Moreover, Arabidopsis mutants deficient in either abscisic acid deficient 2 (ABA2) or abscisic acid insensitive 3 (ABI3) displayed increased expression of the sinapoylglucose:choline sinapoyltransferase (SCT) and sinapoylcholine esterase (SCE) genes with sinapic acid treatment. This treatment also affected the accumulation of sinapoylcholine and free choline during seed germination. We demonstrated that sinapoylcholine, which constitutes the major phenolic component in seeds among various minor sinapate esters, affected ABA homeostasis during seed germination and early seedling growth in Arabidopsis. Our findings provide insights into the role of sinapic acid and its esters in regulating ABA-mediated inhibition of Arabidopsis seed germination in response to drought stress.

Identification of Open Stomata1-Interacting Proteins Reveals Interactions with Sucrose Non-fermenting1-Related Protein Kinases2 and with Type 2A Protein Phosphatases That Function in Abscisic Acid Responses1[OPEN

PubMed Central

Waadt, Rainer; Manalansan, Bianca; Rauniyar, Navin; Munemasa, Shintaro; Booker, Matthew A.; Brandt, Benjamin; Waadt, Christian; Nusinow, Dmitri A.; Kay, Steve A.; Kunz, Hans-Henning; Schumacher, Karin; DeLong, Alison; Yates, John R.; Schroeder, Julian I.

2015-01-01

The plant hormone abscisic acid (ABA) controls growth and development and regulates plant water status through an established signaling pathway. In the presence of ABA, pyrabactin resistance/regulatory component of ABA receptor proteins inhibit type 2C protein phosphatases (PP2Cs). This, in turn, enables the activation of Sucrose Nonfermenting1-Related Protein Kinases2 (SnRK2). Open Stomata1 (OST1)/SnRK2.6/SRK2E is a major SnRK2-type protein kinase responsible for mediating ABA responses. Arabidopsis (Arabidopsis thaliana) expressing an epitope-tagged OST1 in the recessive ost1-3 mutant background was used for the copurification and identification of OST1-interacting proteins after osmotic stress and ABA treatments. These analyses, which were confirmed using bimolecular fluorescence complementation and coimmunoprecipitation, unexpectedly revealed homo- and heteromerization of OST1 with SnRK2.2, SnRK2.3, OST1, and SnRK2.8. Furthermore, several OST1-complexed proteins were identified as type 2A protein phosphatase (PP2A) subunits and as proteins involved in lipid and galactolipid metabolism. More detailed analyses suggested an interaction network between ABA-activated SnRK2-type protein kinases and several PP2A-type protein phosphatase regulatory subunits. pp2a double mutants exhibited a reduced sensitivity to ABA during seed germination and stomatal closure and an enhanced ABA sensitivity in root growth regulation. These analyses add PP2A-type protein phosphatases as another class of protein phosphatases to the interaction network of SnRK2-type protein kinases. PMID:26175513

SOS2-LIKE PROTEIN KINASE5, an SNF1-RELATED PROTEIN KINASE3-Type Protein Kinase, Is Important for Abscisic Acid Responses in Arabidopsis through Phosphorylation of ABSCISIC ACID-INSENSITIVE51[OPEN

PubMed Central

Zhou, Xiaona; Hao, Hongmei; Zhang, Yuguo; Bai, Yili; Zhu, Wenbo; Qin, Yunxia; Yuan, Feifei; Zhao, Feiyi; Wang, Mengyao; Hu, Jingjiang; Xu, Hong; Guo, Aiguang; Zhao, Huixian; Zhao, Yang; Cao, Cuiling; Yang, Yongqing; Schumaker, Karen S.; Guo, Yan; Xie, Chang Gen

2015-01-01

Abscisic acid (ABA) plays an essential role in seed germination. In this study, we demonstrate that one SNF1-RELATED PROTEIN KINASE3-type protein kinase, SOS2-LIKE PROTEIN KINASE5 (PKS5), is involved in ABA signal transduction via the phosphorylation of an interacting protein, ABSCISIC ACID-INSENSITIVE5 (ABI5). We found that pks5-3 and pks5-4, two previously identified PKS5 superactive kinase mutants with point mutations in the PKS5 FISL/NAF (a conserved peptide that is necessary for interaction with SOS3 or SOS3-LIKE CALCIUM BINDING PROTEINs) motif and the kinase domain, respectively, are hypersensitive to ABA during seed germination. PKS5 was found to interact with ABI5 in yeast (Saccharomyces cerevisiae), and this interaction was further confirmed in planta using bimolecular fluorescence complementation. Genetic studies revealed that ABI5 is epistatic to PKS5. PKS5 phosphorylates a serine (Ser) residue at position 42 in ABI5 and regulates ABA-responsive gene expression. This phosphorylation was induced by ABA in vivo and transactivated ABI5. Expression of ABI5, in which Ser-42 was mutated to alanine, could not fully rescue the ABA-insensitive phenotypes of the abi5-8 and pks5-4abi5-8 mutants. In contrast, mutating Ser-42 to aspartate rescued the ABA insensitivity of these mutants. These data demonstrate that PKS5-mediated phosphorylation of ABI5 at Ser-42 is critical for the ABA regulation of seed germination and gene expression in Arabidopsis (Arabidopsis thaliana). PMID:25858916

Identification of Open Stomata1-Interacting Proteins Reveals Interactions with Sucrose Non-fermenting1-Related Protein Kinases2 and with Type 2A Protein Phosphatases That Function in Abscisic Acid Responses

DOE PAGES

Waadt, Rainer; Manalansan, Bianca; Rauniyar, Navin; ...

2015-09-04

The plant hormone abscisic acid (ABA) controls growth and development and regulates plant water status through an established signaling pathway. In the presence of ABA, pyrabactin resistance/regulatory component of ABA receptor proteins inhibit type 2C protein phosphatases (PP2Cs). This, in turn, enables the activation of Sucrose Nonfermenting1-Related Protein Kinases2 (SnRK2). Open Stomata1 (OST1)/SnRK2.6/SRK2E is a major SnRK2-type protein kinase responsible for mediating ABA responses. Arabidopsis (Arabidopsis thaliana) expressing an epitope-tagged OST1 in the recessive ost1-3 mutant background was used for the copurification and identification of OST1-interacting proteins after osmotic stress and ABA treatments. Furthemore, these analyses, which were confirmed usingmore » bimolecular fluorescence complementation and coimmunoprecipitation, unexpectedly revealed homo- and heteromerization of OST1 with SnRK2.2, SnRK2.3, OST1, and SnRK2.8. Furthermore, several OST1-complexed proteins were identified as type 2A protein phosphatase (PP2A) subunits and as proteins involved in lipid and galactolipid metabolism. More detailed analyses suggested an interaction network between ABA-activated SnRK2-type protein kinases and several PP2A-type protein phosphatase regulatory subunits. pp2a double mutants exhibited a reduced sensitivity to ABA during seed germination and stomatal closure and an enhanced ABA sensitivity in root growth regulation. Our analyses add PP2A-type protein phosphatases as another class of protein phosphatases to the interaction network of SnRK2-type protein kinases.« less

ROS regulation of axonal mitochondrial transport is mediated by Ca2+ and JNK in Drosophila

PubMed Central

Liao, Pin-Chao; Tandarich, Lauren C.

2017-01-01

Mitochondria perform critical functions including aerobic ATP production and calcium (Ca2+) homeostasis, but are also a major source of reactive oxygen species (ROS) production. To maintain cellular function and survival in neurons, mitochondria are transported along axons, and accumulate in regions with high demand for their functions. Oxidative stress and abnormal mitochondrial axonal transport are associated with neurodegenerative disorders. However, we know little about the connection between these two. Using the Drosophila third instar larval nervous system as the in vivo model, we found that ROS inhibited mitochondrial axonal transport more specifically, primarily due to reduced flux and velocity, but did not affect transport of other organelles. To understand the mechanisms underlying these effects, we examined Ca2+ levels and the JNK (c-Jun N-terminal Kinase) pathway, which have been shown to regulate mitochondrial transport and general fast axonal transport, respectively. We found that elevated ROS increased Ca2+ levels, and that experimental reduction of Ca2+ to physiological levels rescued ROS-induced defects in mitochondrial transport in primary neuron cell cultures. In addition, in vivo activation of the JNK pathway reduced mitochondrial flux and velocities, while JNK knockdown partially rescued ROS-induced defects in the anterograde direction. We conclude that ROS have the capacity to regulate mitochondrial traffic, and that Ca2+ and JNK signaling play roles in mediating these effects. In addition to transport defects, ROS produces imbalances in mitochondrial fission-fusion and metabolic state, indicating that mitochondrial transport, fission-fusion steady state, and metabolic state are closely interrelated in the response to ROS. PMID:28542430

Reactive Oxygen Species Function to Mediate the Fe Deficiency Response in an Fe-Efficient Apple Genotype: An Early Response Mechanism for Enhancing Reactive Oxygen Production

PubMed Central

Sun, Chaohua; Wu, Ting; Zhai, Longmei; Li, Duyue; Zhang, Xinzhong; Xu, Xuefeng; Ma, Huiqin; Wang, Yi; Han, Zhenhai

2016-01-01

Reactive oxygen species (ROS) are important signaling molecules in plants that contribute to stress acclimation. This study demonstrated that ROS play a critical role in Fe deficiency-induced signaling at an early stage in Malus xiaojinensis. Once ROS production has been initiated, prolonged Fe starvation leads to activation of ROS scavenging mechanisms. Further, we demonstrated that ROS scavengers are involved in maintaining the cellular redox homeostasis during prolonged Fe deficiency treatment. Taken together, our results describe a feedback repression loop for ROS to preserve redox homeostasis and maintain a continuous Fe deficiency response in the Fe-efficient woody plant M. xiaojinensis. More broadly, this study reveals a new mechanism in which ROS mediate both positive and negative regulation of plant responses to Fe deficiency stress. PMID:27899933

The role of Nox1 and Nox2 in GPVI-dependent platelet activation and thrombus formation☆

PubMed Central

Walsh, T.G.; Berndt, M.C.; Carrim, N.; Cowman, J.; Kenny, D.; Metharom, P.

2014-01-01

Background Activation of the platelet-specific collagen receptor, glycoprotein (GP) VI, induces intracellular reactive oxygen species (ROS) production; however the relevance of ROS to GPVI-mediated platelet responses remains unclear. Objective The objective of this study was to explore the role of the ROS-producing NADPH oxidase (Nox)1 and 2 complexes in GPVI-dependent platelet activation and collagen-induced thrombus formation. Methods and results ROS production was measured by quantitating changes in the oxidation-sensitive dye, H2DCF-DA, following platelet activation with the GPVI-specific agonist, collagen related peptide (CRP). Using a pharmacological inhibitor specific for Nox1, 2-acetylphenothiazine (ML171), and Nox2 deficient mice, we show that Nox1 is the key Nox homolog regulating GPVI-dependent ROS production. Nox1, but not Nox2, was essential for CRP-dependent thromboxane (Tx)A2 production, which was mediated in part through p38 MAPK signaling; while neither Nox1 nor Nox2 was significantly involved in regulating CRP-induced platelet aggregation/integrin αIIbβ3 activation, platelet spreading, or dense granule and α-granule release (ATP release and P-selectin surface expression, respectively). Ex-vivo perfusion analysis of mouse whole blood revealed that both Nox1 and Nox2 were involved in collagen-mediated thrombus formation at arterial shear. Conclusion Together these results demonstrate a novel role for Nox1 in regulating GPVI-induced ROS production, which is essential for optimal p38 activation and subsequent TxA2 production, providing an explanation for reduced thrombus formation following Nox1 inhibition. PMID:24494191

Functional characterization of NAC55 transcription factor from oilseed rape (Brassica napus L.) as a novel transcriptional activator modulating reactive oxygen species accumulation and cell death.

PubMed

Niu, Fangfang; Wang, Chen; Yan, Jingli; Guo, Xiaohua; Wu, Feifei; Yang, Bo; Deyholos, Michael K; Jiang, Yuan-Qing

2016-09-01

NAC transcription factors (TFs) are plant-specific and play important roles in development, responses to biotic and abiotic cues and hormone signaling. So far, only a few NAC genes have been reported to regulate cell death. In this study, we identified and characterized a NAC55 gene isolated from oilseed rape (Brassica napus L.). BnaNAC55 responds to multiple stresses, including cold, heat, abscisic acid (ABA), jasmonic acid (JA) and a necrotrophic fungal pathogen Sclerotinia sclerotiorum. BnaNAC55 has transactivation activity and is located in the nucleus. BnaNAC55 is able to form homodimers in planta. Unlike ANAC055, full-length BnaNAC55, but not either the N-terminal NAC domain or C-terminal regulatory domain, induces ROS accumulation and hypersensitive response (HR)-like cell death when expressed both in oilseed rape protoplasts and Nicotiana benthamiana. Furthermore, BnaNAC55 expression causes obvious nuclear DNA fragmentation. Moreover, quantitative reverse transcription PCR (qRT-PCR) analysis identified that the expression levels of multiple genes regulating ROS production and scavenging, defense response as well as senescence are significantly induced. Using a dual luciferase reporter assay, we further confirm that BnaNAC55 could activate the expression of a few ROS and defense-related gene expression. Taken together, our work has identified a novel NAC TF from oilseed rape that modulates ROS accumulation and cell death.

The regulator of G-protein signaling proteins involved in sugar and abscisic acid signaling in Arabidopsis seed germination.

PubMed

Chen, Yun; Ji, Fangfang; Xie, Hong; Liang, Jiansheng; Zhang, Jianhua

2006-01-01

The regulator of G-protein signaling (RGS) proteins, recently identified in Arabidopsis (Arabidopsis thaliana; named as AtRGS1), has a predicted seven-transmembrane structure as well as an RGS box with GTPase-accelerating activity and thus desensitizes the G-protein-mediated signaling. The roles of AtRGS1 proteins in Arabidopsis seed germination and their possible interactions with sugars and abscisic acid (ABA) were investigated in this study. Using seeds that carry a null mutation in the genes encoding RGS protein (AtRGS1) and the alpha-subunit (AtGPA1) of the G protein in Arabidopsis (named rgs1-2 and gpa1-3, respectively), our genetic evidence proved the involvement of the AtRGS1 protein in the modulation of seed germination. In contrast to wild-type Columbia-0 and gpa1-3, stratification was found not to be required and the after-ripening process had no effect on the rgs1-2 seed germination. In addition, rgs1-2 seed germination was insensitive to glucose (Glc) and sucrose. The insensitivities of rgs1-2 to Glc and sucrose were not due to a possible osmotic stress because the germination of rgs1-2 mutant seeds showed the same response as those of gpa1-3 mutants and wild type when treated with the same concentrations of mannitol and sorbitol. The gpa1-3 seed germination was hypersensitive while rgs1-2 was less sensitive to exogenous ABA. The different responses to ABA largely diminished and the inhibitory effects on seed germination by exogenous ABA and Glc were markedly alleviated when endogenous ABA biosynthesis was inhibited. Hypersensitive responses of seed germination to both Glc and ABA were also observed in the overexpressor of AtRGS1. Analysis of the active endogenous ABA levels and the expression of NCED3 and ABA2 genes showed that Glc significantly stimulated the ABA biosynthesis and increased the expression of NCED3 and ABA2 genes in germinating Columbia seeds, but not in rgs1-2 mutant seeds. These data suggest that AtRGS1 proteins are involved in the regulation of seed germination. The hyposensitivity of rgs1-2 mutant seed germination to Glc might be the result of the impairment of ABA biosynthesis during seed germination.

The Regulator of G-Protein Signaling Proteins Involved in Sugar and Abscisic Acid Signaling in Arabidopsis Seed Germination1

PubMed Central

Chen, Yun; Ji, Fangfang; Xie, Hong; Liang, Jiansheng; Zhang, Jianhua

2006-01-01

The regulator of G-protein signaling (RGS) proteins, recently identified in Arabidopsis (Arabidopsis thaliana; named as AtRGS1), has a predicted seven-transmembrane structure as well as an RGS box with GTPase-accelerating activity and thus desensitizes the G-protein-mediated signaling. The roles of AtRGS1 proteins in Arabidopsis seed germination and their possible interactions with sugars and abscisic acid (ABA) were investigated in this study. Using seeds that carry a null mutation in the genes encoding RGS protein (AtRGS1) and the α-subunit (AtGPA1) of the G protein in Arabidopsis (named rgs1-2 and gpa1-3, respectively), our genetic evidence proved the involvement of the AtRGS1 protein in the modulation of seed germination. In contrast to wild-type Columbia-0 and gpa1-3, stratification was found not to be required and the after-ripening process had no effect on the rgs1-2 seed germination. In addition, rgs1-2 seed germination was insensitive to glucose (Glc) and sucrose. The insensitivities of rgs1-2 to Glc and sucrose were not due to a possible osmotic stress because the germination of rgs1-2 mutant seeds showed the same response as those of gpa1-3 mutants and wild type when treated with the same concentrations of mannitol and sorbitol. The gpa1-3 seed germination was hypersensitive while rgs1-2 was less sensitive to exogenous ABA. The different responses to ABA largely diminished and the inhibitory effects on seed germination by exogenous ABA and Glc were markedly alleviated when endogenous ABA biosynthesis was inhibited. Hypersensitive responses of seed germination to both Glc and ABA were also observed in the overexpressor of AtRGS1. Analysis of the active endogenous ABA levels and the expression of NCED3 and ABA2 genes showed that Glc significantly stimulated the ABA biosynthesis and increased the expression of NCED3 and ABA2 genes in germinating Columbia seeds, but not in rgs1-2 mutant seeds. These data suggest that AtRGS1 proteins are involved in the regulation of seed germination. The hyposensitivity of rgs1-2 mutant seed germination to Glc might be the result of the impairment of ABA biosynthesis during seed germination. PMID:16361523

Novel Phosphorylation and Ubiquitination Sites Regulate Reactive Oxygen Species-dependent Degradation of Anti-apoptotic c-FLIP Protein*

PubMed Central

Wilkie-Grantham, Rachel P.; Matsuzawa, Shu-Ichi; Reed, John C.

2013-01-01

The cytosolic protein c-FLIP (cellular Fas-associated death domain-like interleukin 1β-converting enzyme inhibitory protein) is an inhibitor of death receptor-mediated apoptosis that is up-regulated in a variety of cancers, contributing to apoptosis resistance. Several compounds found to restore sensitivity of cancer cells to TRAIL, a TNF family death ligand with promising therapeutic potential, act by targeting c-FLIP ubiquitination and degradation by the proteasome. The generation of reactive oxygen species (ROS) has been implicated in c-FLIP protein degradation. However, the mechanism by which ROS post-transcriptionally regulate c-FLIP protein levels is not well understood. We show here that treatment of prostate cancer PPC-1 cells with the superoxide generators menadione, paraquat, or buthionine sulfoximine down-regulates c-FLIP long (c-FLIPL) protein levels, which is prevented by the proteasome inhibitor MG132. Furthermore, pretreatment of PPC-1 cells with a ROS scavenger prevented ubiquitination and loss of c-FLIPL protein induced by menadione or paraquat. We identified lysine 167 as a novel ubiquitination site of c-FLIPL important for ROS-dependent degradation. We also identified threonine 166 as a novel phosphorylation site and demonstrate that Thr-166 phosphorylation is required for ROS-induced Lys-167 ubiquitination. The mutation of either Thr-166 or Lys-167 was sufficient to stabilize c-FLIP protein levels in PPC-1, HEK293T, and HeLa cancer cells treated with menadione or paraquat. Accordingly, expression of c-FLIP T166A or K167R mutants protected cells from ROS-mediated sensitization to TRAIL-induced cell death. Our findings reveal novel ROS-dependent post-translational modifications of the c-FLIP protein that regulate its stability, thus impacting sensitivity of cancer cells to TRAIL. PMID:23519470

Novel phosphorylation and ubiquitination sites regulate reactive oxygen species-dependent degradation of anti-apoptotic c-FLIP protein.

PubMed

Wilkie-Grantham, Rachel P; Matsuzawa, Shu-Ichi; Reed, John C

2013-05-03

The cytosolic protein c-FLIP (cellular Fas-associated death domain-like interleukin 1β-converting enzyme inhibitory protein) is an inhibitor of death receptor-mediated apoptosis that is up-regulated in a variety of cancers, contributing to apoptosis resistance. Several compounds found to restore sensitivity of cancer cells to TRAIL, a TNF family death ligand with promising therapeutic potential, act by targeting c-FLIP ubiquitination and degradation by the proteasome. The generation of reactive oxygen species (ROS) has been implicated in c-FLIP protein degradation. However, the mechanism by which ROS post-transcriptionally regulate c-FLIP protein levels is not well understood. We show here that treatment of prostate cancer PPC-1 cells with the superoxide generators menadione, paraquat, or buthionine sulfoximine down-regulates c-FLIP long (c-FLIP(L)) protein levels, which is prevented by the proteasome inhibitor MG132. Furthermore, pretreatment of PPC-1 cells with a ROS scavenger prevented ubiquitination and loss of c-FLIP(L) protein induced by menadione or paraquat. We identified lysine 167 as a novel ubiquitination site of c-FLIP(L) important for ROS-dependent degradation. We also identified threonine 166 as a novel phosphorylation site and demonstrate that Thr-166 phosphorylation is required for ROS-induced Lys-167 ubiquitination. The mutation of either Thr-166 or Lys-167 was sufficient to stabilize c-FLIP protein levels in PPC-1, HEK293T, and HeLa cancer cells treated with menadione or paraquat. Accordingly, expression of c-FLIP T166A or K167R mutants protected cells from ROS-mediated sensitization to TRAIL-induced cell death. Our findings reveal novel ROS-dependent post-translational modifications of the c-FLIP protein that regulate its stability, thus impacting sensitivity of cancer cells to TRAIL.

Reactive Oxygen Species in Metabolic and Inflammatory Signaling.

PubMed

Forrester, Steven J; Kikuchi, Daniel S; Hernandes, Marina S; Xu, Qian; Griendling, Kathy K

2018-03-16

Reactive oxygen species (ROS) are well known for their role in mediating both physiological and pathophysiological signal transduction. Enzymes and subcellular compartments that typically produce ROS are associated with metabolic regulation, and diseases associated with metabolic dysfunction may be influenced by changes in redox balance. In this review, we summarize the current literature surrounding ROS and their role in metabolic and inflammatory regulation, focusing on ROS signal transduction and its relationship to disease progression. In particular, we examine ROS production in compartments such as the cytoplasm, mitochondria, peroxisome, and endoplasmic reticulum and discuss how ROS influence metabolic processes such as proteasome function, autophagy, and general inflammatory signaling. We also summarize and highlight the role of ROS in the regulation metabolic/inflammatory diseases including atherosclerosis, diabetes mellitus, and stroke. In order to develop therapies that target oxidative signaling, it is vital to understand the balance ROS signaling plays in both physiology and pathophysiology, and how manipulation of this balance and the identity of the ROS may influence cellular and tissue homeostasis. An increased understanding of specific sources of ROS production and an appreciation for how ROS influence cellular metabolism may help guide us in the effort to treat cardiovascular diseases. © 2018 American Heart Association, Inc.

Common and unique elements of the ABA-regulated transcriptome of Arabidopsis guard cells

PubMed Central

2011-01-01

Background In the presence of drought and other desiccating stresses, plants synthesize and redistribute the phytohormone abscisic acid (ABA). ABA promotes plant water conservation by acting on specialized cells in the leaf epidermis, guard cells, which border and regulate the apertures of stomatal pores through which transpirational water loss occurs. Following ABA exposure, solute uptake into guard cells is rapidly inhibited and solute loss is promoted, resulting in inhibition of stomatal opening and promotion of stomatal closure, with consequent plant water conservation. There is a wealth of information on the guard cell signaling mechanisms underlying these rapid ABA responses. To investigate ABA regulation of gene expression in guard cells in a systematic genome-wide manner, we analyzed data from global transcriptomes of guard cells generated with Affymetrix ATH1 microarrays, and compared these results to ABA regulation of gene expression in leaves and other tissues. Results The 1173 ABA-regulated genes of guard cells identified by our study share significant overlap with ABA-regulated genes of other tissues, and are associated with well-defined ABA-related promoter motifs such as ABREs and DREs. However, we also computationally identified a unique cis-acting motif, GTCGG, associated with ABA-induction of gene expression specifically in guard cells. In addition, approximately 300 genes showing ABA-regulation unique to this cell type were newly uncovered by our study. Within the ABA-regulated gene set of guard cells, we found that many of the genes known to encode ion transporters associated with stomatal opening are down-regulated by ABA, providing one mechanism for long-term maintenance of stomatal closure during drought. We also found examples of both negative and positive feedback in the transcriptional regulation by ABA of known ABA-signaling genes, particularly with regard to the PYR/PYL/RCAR class of soluble ABA receptors and their downstream targets, the type 2C protein phosphatases. Our data also provide evidence for cross-talk at the transcriptional level between ABA and another hormonal inhibitor of stomatal opening, methyl jasmonate. Conclusions Our results engender new insights into the basic cell biology of guard cells, reveal common and unique elements of ABA-regulation of gene expression in guard cells, and set the stage for targeted biotechnological manipulations to improve plant water use efficiency. PMID:21554708

ROS-mediated redox signaling during cell differentiation in plants.

PubMed

Schmidt, Romy; Schippers, Jos H M

2015-08-01

Reactive oxygen species (ROS) have emerged in recent years as important regulators of cell division and differentiation. The cellular redox state has a major impact on cell fate and multicellular organism development. However, the exact molecular mechanisms through which ROS manifest their regulation over cellular development are only starting to be understood in plants. ROS levels are constantly monitored and any change in the redox pool is rapidly sensed and responded upon. Different types of ROS cause specific oxidative modifications, providing the basic characteristics of a signaling molecule. Here we provide an overview of ROS sensors and signaling cascades that regulate transcriptional responses in plants to guide cellular differentiation and organ development. Although several redox sensors and cascades have been identified, they represent only a first glimpse on the impact that redox signaling has on plant development and growth. We provide an initial evaluation of ROS signaling cascades involved in cell differentiation in plants and identify potential avenues for future studies. This article is part of a Special Issue entitled Redox regulation of differentiation and de-differentiation. Copyright © 2015 Elsevier B.V. All rights reserved.

Cross-species approaches to seed dormancy and germination: conservation and biodiversity of ABA-regulated mechanisms and the Brassicaceae DOG1 genes.

PubMed

Graeber, Kai; Linkies, Ada; Müller, Kerstin; Wunchova, Andrea; Rott, Anita; Leubner-Metzger, Gerhard

2010-05-01

Seed dormancy is genetically determined with substantial environmental influence mediated, at least in part, by the plant hormone abscisic acid (ABA). The ABA-related transcription factor ABI3/VP1 (ABA INSENSITIVE3/VIVIPAROUS1) is widespread among green plants. Alternative splicing of its transcripts appears to be involved in regulating seed dormancy, but the role of ABI3/VP1 goes beyond seeds and dormancy. In contrast, DOG1 (DELAY OF GERMINATION 1), a major quantitative trait gene more specifically involved in seed dormancy, was so far only known from Arabidopsis thaliana (AtDOG1) and whether it also has roles during the germination of non-dormant seeds was not known. Seed germination of Lepidium sativum ('garden cress') is controlled by ABA and its antagonists gibberellins and ethylene and involves the production of apoplastic hydroxyl radicals. We found orthologs of AtDOG1 in the Brassicaceae relatives L. sativum (LesaDOG1) and Brassica rapa (BrDOG1) and compared their gene structure and the sequences of their transcripts expressed in seeds. Tissue-specific analysis of LesaDOG1 transcript levels in L. sativum seeds showed that they are degraded upon imbibition in the radicle and the micropylar endosperm. ABA inhibits germination in that it delays radicle protrusion and endosperm weakening and it increased LesaDOG1 transcript levels during early germination due to enhanced transcription and/or inhibited degradation. A reduced decrease in LesaDOG1 transcript levels upon ABA treatment is evident in the late germination phase in both tissues. This temporal and ABA-related transcript expression pattern suggests a role for LesaDOG1 in the control of germination timing of non-dormant L. sativum seeds. The possible involvement of the ABA-related transcription factors ABI3 and ABI5 in the regulation of DOG1 transcript expression is discussed. Other species of the monophyletic genus Lepidium showed coat or embryo dormancy and are therefore highly suited for comparative seed biology.

RING Type E3 Ligase CaAIR1 in Pepper Acts in the Regulation of ABA Signaling and Drought Stress Response.

PubMed

Park, Chanmi; Lim, Chae Woo; Baek, Woonhee; Lee, Sung Chul

2015-09-01

Several E3 ubiquitin ligases have been associated with the response to abiotic and biotic stresses in higher plants. Here, we report that the hot pepper (Capsicum annuum) ABA-Insensitive RING protein 1 gene (CaAIR1) is essential for a hypersensitive response to drought stress. CaAIR1 contains a C3HC4-type RING finger motif, which plays a role for attachment of ubiquitins to the target protein, and a putative transmembrane domain. The expression levels of CaAIR1 are up-regulated in pepper leaves by ABA treatments, drought and NaCl, suggesting its role in the response to abiotic stress. Our analysis showed that CaAIR1 displays self-ubiquitination and is localized in the nucleus. We generated CaAIR1-silenced peppers via virus-induced gene silencing (VIGS) and CaAIR1-overexpressing (OX) transgenic Arabidopsis plants to evaluate their responses to ABA and drought. VIGS of CaAIR1 in pepper plants conferred an enhanced tolerance to drought stress, which was accompanied by low levels of transpirational water loss in the drought-treated leaves. CaAIR1-OX plants displayed an impaired sensitivity to ABA during seed germination, seedling and adult stages. Moreover, these plants showed enhanced sensitivity to drought stress because of reduced stomatal closure and decreased expression of stress-responsive genes. Thus, our data indicate that CaAIR1 is a negative regulator of the ABA-mediated drought stress tolerance mechanism. © The Author 2015. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Identification of low Ca(2+) stress-induced embryo apoptosis response genes in Arachis hypogaea by SSH-associated library lift (SSHaLL).

PubMed

Chen, Hua; Zhang, Chong; Cai, Tie Cheng; Deng, Ye; Zhou, Shuangbiao; Zheng, Yixiong; Ma, Shiwei; Tang, Ronghua; Varshney, Rajeev K; Zhuang, Weijian

2016-02-01

Calcium is a universal signal in the regulation of wide aspects in biology, but few are known about the function of calcium in the control of early embryo development. Ca(2+) deficiency in soil induces early embryo abortion in peanut, producing empty pods, which is a general problem; however, the underlying mechanism remains unclear. In this study, embryo abortion was characterized to be caused by apoptosis marked with cell wall degradation. Using a method of SSH cDNA libraries associated with library lift (SSHaLL), 62 differentially expressed genes were isolated from young peanut embryos. These genes were classified to be stress responses, catabolic process, carbohydrate and lipid metabolism, embryo morphogenesis, regulation, etc. The cell retardation with cell wall degradation was caused by up-regulated cell wall hydrolases and down-regulated cellular synthases genes. HsfA4a, which was characterized to be important to embryo development, was significantly down-regulated under Ca(2+) -deficient conditions from 15 days after pegging (DAP) to 30 DAP. Two AhCYP707A4 genes, encoding abscisic acid (ABA) 8'-hydroxylases, key enzymes for ABA catabolism, were up-regulated by 21-fold under Ca(2+) -deficient conditions upstream of HsfA4a, reducing the ABA level in early embryos. Over-expression of AhCYP707A4 in Nicotiana benthamiana showed a phenotype of low ABA content with high numbers of aborted embryos, small pods and less seeds, which confirms that AhCYP707A4 is a key player in regulation of Ca(2+) deficiency-induced embryo abortion via ABA-mediated apoptosis. The results elucidated the mechanism of low Ca(2+) -induced embryo abortion and described the method for other fields of study. © 2015 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

The Brown Midrib Leaf (bml) Mutation in Rice (Oryza sativa L.) Causes Premature Leaf Senescence and the Induction of Defense Responses.

PubMed

Akhter, Delara; Qin, Ran; Nath, Ujjal Kumar; Alamin, Md; Jin, Xiaoli; Shi, Chunhai

2018-04-09

Isolating and characterizing mutants with altered senescence phenotypes is one of the ways to understand the molecular basis of leaf aging. Using ethyl methane sulfonate mutagenesis, a new rice ( Oryza sativa ) mutant, brown midrib leaf ( bml ), was isolated from the indica cultivar 'Zhenong34'. The bml mutants had brown midribs in their leaves and initiated senescence prematurely, at the onset of heading. The mutants had abnormal cells with degraded chloroplasts and contained less chlorophyll compared to the wild type (WT). The bml mutant showed excessive accumulation of reactive oxygen species (ROS), increased activities of superoxide dismutase, catalase, and malondialdehyde, upregulation of senescence-induced STAY-GREEN genes and senescence-related transcription factors, and down regulation of photosynthesis-related genes. The levels of abscisic acid (ABA) and jasmonic acid (JA) were increased in bml with the upregulation of some ABA and JA biosynthetic genes. In pathogen response, bml demonstrated higher resistance against Xanthomonas oryzae pv. oryzae and upregulation of four pathogenesis-related genes compared to the WT. A genetic study confirmed that the bml trait was caused by a single recessive nuclear gene ( BML ). A map-based cloning using insertion/deletion markers confirmed that BML was located in the 57.32kb interval between the L5IS7 and L5IS11 markers on the short arm of chromosome 5. A sequence analysis of the candidate region identified a 1 bp substitution (G to A) in the 5'-UTR (+98) of bml . BML is a candidate gene associated with leaf senescence, ROS regulation, and disease response, also involved in hormone signaling in rice. Therefore, this gene might be useful in marker-assisted backcrossing/gene editing to improve rice cultivars.

Importance of ABA homeostasis under terminal drought stress in regulating grain filling events

PubMed Central

Govind, Geetha; Seiler, Christiane; Wobus, Ulrich

2011-01-01

Recent studies suggest that abscisic acid (ABA) at its basal level plays an important role during seed set and grain filling events. Under drought stress ABA levels were found to be significantly enhanced in the developing seed. Until now we lacked an understanding of (1) ABA homeostasis in developing seeds under terminal drought and (2) the interactive role of ABA in regulating the starch biosynthesis pathway in developing grains under terminal drought. We have recently reported the possible regulation of ABA homeostasis in source (flag leaf) and sink (developing grains) tissues under post-anthesis drought stress in barley and concluded that significantly enhanced ABA levels in developing grains are due to strong activation of the ABA deconjugation pathway and fine regulation of the ABA biosynthesis-degradation pathway.1 Additionally, we provided evidence for the role of ABA in differential regulation of starch biosynthesis genes and a significant upregulation of starch degradation beta amylase genes under drought, i.e., ABA not only influences the rate of starch accumulation but also starch quality. PMID:21778825

Arabidopsis basic leucine zipper transcription factors involved in an abscisic acid-dependent signal transduction pathway under drought and high-salinity conditions

PubMed Central

Uno, Yuichi; Furihata, Takashi; Abe, Hiroshi; Yoshida, Riichiro; Shinozaki, Kazuo; Yamaguchi-Shinozaki, Kazuko

2000-01-01

The induction of the dehydration-responsive Arabidopsis gene, rd29B, is mediated mainly by abscisic acid (ABA). Promoter analysis of rd29B indicated that two ABA-responsive elements (ABREs) are required for the dehydration-responsive expression of rd29B as cis-acting elements. Three cDNAs encoding basic leucine zipper (bZIP)-type ABRE-binding proteins were isolated by using the yeast one-hybrid system and were designated AREB1, AREB2, and AREB3 (ABA-responsive element binding protein). Transcription of the AREB1 and AREB2 genes is up-regulated by drought, NaCl, and ABA treatment in vegetative tissues. In a transient transactivation experiment using Arabidopsis leaf protoplasts, both the AREB1 and AREB2 proteins activated transcription of a reporter gene driven by ABRE. AREB1 and AREB2 required ABA for their activation, because their transactivation activities were repressed in aba2 and abi1 mutants and enhanced in an era1 mutant. Activation of AREBs by ABA was suppressed by protein kinase inhibitors. These results suggest that both AREB1 and AREB2 function as transcriptional activators in the ABA-inducible expression of rd29B, and further that ABA-dependent posttranscriptional activation of AREB1 and AREB2, probably by phosphorylation, is necessary for their maximum activation by ABA. Using cultured Arabidopsis cells, we demonstrated that a specific ABA-activated protein kinase of 42-kDa phosphorylated conserved N-terminal regions in the AREB proteins. PMID:11005831

Arabidopsis basic leucine zipper transcription factors involved in an abscisic acid-dependent signal transduction pathway under drought and high-salinity conditions.

PubMed

Uno, Y; Furihata, T; Abe, H; Yoshida, R; Shinozaki, K; Yamaguchi-Shinozaki, K

2000-10-10

The induction of the dehydration-responsive Arabidopsis gene, rd29B, is mediated mainly by abscisic acid (ABA). Promoter analysis of rd29B indicated that two ABA-responsive elements (ABREs) are required for the dehydration-responsive expression of rd29B as cis-acting elements. Three cDNAs encoding basic leucine zipper (bZIP)-type ABRE-binding proteins were isolated by using the yeast one-hybrid system and were designated AREB1, AREB2, and AREB3 (ABA-responsive element binding protein). Transcription of the AREB1 and AREB2 genes is up-regulated by drought, NaCl, and ABA treatment in vegetative tissues. In a transient transactivation experiment using Arabidopsis leaf protoplasts, both the AREB1 and AREB2 proteins activated transcription of a reporter gene driven by ABRE. AREB1 and AREB2 required ABA for their activation, because their transactivation activities were repressed in aba2 and abi1 mutants and enhanced in an era1 mutant. Activation of AREBs by ABA was suppressed by protein kinase inhibitors. These results suggest that both AREB1 and AREB2 function as transcriptional activators in the ABA-inducible expression of rd29B, and further that ABA-dependent posttranscriptional activation of AREB1 and AREB2, probably by phosphorylation, is necessary for their maximum activation by ABA. Using cultured Arabidopsis cells, we demonstrated that a specific ABA-activated protein kinase of 42-kDa phosphorylated conserved N-terminal regions in the AREB proteins.

RNA sequencing supports distinct reactive oxygen species-mediated pathways of apoptosis by high and low size mass fractions of Bay leaf (Lauris nobilis) in HT-29 cells.

PubMed

Rodd, Annabelle L; Ververis, Katherine; Sayakkarage, Dheeshana; Khan, Abdul W; Rafehi, Haloom; Ziemann, Mark; Loveridge, Shanon J; Lazarus, Ross; Kerr, Caroline; Lockett, Trevor; El-Osta, Assam; Karagiannis, Tom C; Bennett, Louise E

2015-08-01

Anti-proliferative and pro-apoptotic effects of Bay leaf (Laurus nobilis) in mammalian cancer and HT-29 adenocarcinoma cells have been previously attributed to effects of polyphenolic and essential oil chemical species. Recently, we demonstrated differentiated growth-regulating effects of high (HFBL) versus low molecular mass (LFBL) aqueous fractions of bay leaf and now confirm by comparative effects on gene expression, that HFBL and LFBL suppress HT-29 growth by distinct mechanisms. Induction of intra-cellular lesions including DNA strand breakage by extra-cellular HFBL, invoked the hypothesis that iron-mediated reactive oxygen species with capacity to penetrate cell membrane, were responsible for HFBL-mediated effects, supported by equivalent effects of HFBL in combination with γ radiation. Activities of HFBL and LFBL were interpreted to reflect differentiated responses to iron-mediated reactive oxygen species (ROS), occurring either outside or inside cells. In the presence of LFBL, apoptotic death was relatively delayed compared with HFBL. ROS production by LFBL mediated p53-dependent apoptosis and recovery was suppressed by promoting G1/S phase arrest and failure of cellular tight junctions. In comparison, intra-cellular anti-oxidant protection exerted by LFBL was absent for extra-cellular HFBL (likely polysaccharide-rich), which potentiated more rapid apoptosis by producing DNA double strand breaks. Differentiated effects on expression of genes regulating ROS defense and chromatic condensation by LFBL versus HFBL, were observed. The results support ferrous iron in cell culture systems and potentially in vivo, can invoke different extra-cellular versus intra-cellular ROS-mediated chemistries, that may be regulated by exogenous, including dietary species.

Reactive oxygen species are required for zoledronic acid-induced apoptosis in osteoclast precursors and mature osteoclast-like cells

PubMed Central

Tai, Ta-Wei; Chen, Ching-Yu; Su, Fong-Chin; Tu, Yuan-Kun; Tsai, Tsung-Ting; Lin, Chiou-Feng; Jou, I.-Ming

2017-01-01

Inhibiting osteoclasts and osteoclast precursors to reduce bone resorption is an important strategy to treat osteoclast-related diseases, such as osteoporosis, inflammatory bone loss, and malignant bone metastasis. However, the mechanism by which apoptosis is induced in the osteoclasts and their precursors are not completely understood. Here, we used nitrogen-containing bisphosphonate zoledronic acid (ZA) to induce cell apoptosis in human and murine osteoclast precursors and mature osteoclast-like cells. Caspase-3-mediated cell apoptosis occurred following the ZA (100 μM) treatment. Reactive oxygen species (ROS) were also generated in a time-dependent manner. Following knock-down of the p47phox expression, which is required for ROS activation, or co-treatment with the ROS inhibitor, N-acetyl-L-cysteine, ZA-induced apoptosis was significantly suppressed in both osteoclast precursors and mature osteoclast-like cells. The ROS-activated mitogen-activated protein kinases pathways did not trigger cell apoptosis. However, a ROS-regulated Mcl-1 decrease simultaneously with glycogen synthase kinase (GSK)-3β promoted cell apoptosis. These findings show that ZA induces apoptosis in osteoclast precursors and mature osteoclast-like cells by triggering ROS- and GSK-3β-mediated Mcl-1 down-regulation. PMID:28281643

Apoptosis induction by silica nanoparticles mediated through reactive oxygen species in human liver cell line HepG2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmad, Javed; Ahamed, Maqusood, E-mail: maqusood@gmail.com; Akhtar, Mohd Javed

Silica nanoparticles are increasingly utilized in various applications including agriculture and medicine. In vivo studies have shown that liver is one of the primary target organ of silica nanoparticles. However, possible mechanisms of hepatotoxicity caused by silica nanoparticles still remain unclear. In this study, we explored the reactive oxygen species (ROS) mediated apoptosis induced by well-characterized 14 nm silica nanoparticles in human liver cell line HepG2. Silica nanoparticles (25–200 μg/ml) induced a dose-dependent cytotoxicity in HepG2 cells. Silica nanoparticles were also found to induce oxidative stress in dose-dependent manner indicated by induction of ROS and lipid peroxidation and depletion ofmore » glutathione (GSH). Quantitative real-time PCR and immunoblotting results showed that both the mRNA and protein expressions of cell cycle checkpoint gene p53 and apoptotic genes (bax and caspase-3) were up-regulated while the anti-apoptotic gene bcl-2 was down-regulated in silica nanoparticles treated cells. Moreover, co-treatment of ROS scavenger vitamin C significantly attenuated the modulation of apoptotic markers along with the preservation of cell viability caused by silica nanoparticles. Our data demonstrated that silica nanoparticles induced apoptosis in human liver cells, which is ROS mediated and regulated through p53, bax/bcl-2 and caspase pathways. This study suggests that toxicity mechanisms of silica nanoparticles should be further investigated at in vivo level. -- Highlights: ► We explored the mechanisms of toxicity caused by silica NPs in human liver HepG2 cells. ► Silica NPs induced a dose-dependent cytotoxicity in HepG2 cells. ► Silica NPs induced ROS generation and oxidative stress in a dose-dependent manner. ► Silica NPs were also modulated apoptosis markers both at mRNA and protein levels. ► ROS mediated apoptosis induced by silica NPs was preserved by vitamin C.« less

ABA-insensitive3, ABA-insensitive5, and DELLAs Interact to activate the expression of SOMNUS and other high-temperature-inducible genes in imbibed seeds in Arabidopsis.

PubMed

Lim, Soohwan; Park, Jeongmoo; Lee, Nayoung; Jeong, Jinkil; Toh, Shigeo; Watanabe, Asuka; Kim, Junghyun; Kang, Hyojin; Kim, Dong Hwan; Kawakami, Naoto; Choi, Giltsu

2013-12-01

Seeds monitor the environment to germinate at the proper time, but different species respond differently to environmental conditions, particularly light and temperature. In Arabidopsis thaliana, light promotes germination but high temperature suppresses germination. We previously reported that light promotes germination by repressing SOMNUS (SOM). Here, we examined whether high temperature also regulates germination through SOM and found that high temperature activates SOM expression. Consistent with this, som mutants germinated more frequently than the wild type at high temperature. The induction of SOM mRNA at high temperature required abscisic acid (ABA) and gibberellic acid biosynthesis, and ABA-insensitive3 (ABI3), ABI5, and DELLAs positively regulated SOM expression. Chromatin immunoprecipitation assays indicated that ABI3, ABI5, and DELLAs all target the SOM promoter. At the protein level, ABI3, ABI5, and DELLAs all interact with each other, suggesting that they form a complex on the SOM promoter to activate SOM expression at high temperature. We found that high-temperature-inducible genes frequently have RY motifs and ABA-responsive elements in their promoters, some of which are targeted by ABI3, ABI5, and DELLAs in vivo. Taken together, our data indicate that ABI3, ABI5, and DELLAs mediate high-temperature signaling to activate the expression of SOM and other high-temperature-inducible genes, thereby inhibiting seed germination.

Abscisic acid negatively regulates post-penetration resistance of Arabidopsis to the biotrophic powdery mildew fungus.

PubMed

Xiao, Xiang; Cheng, Xi; Yin, Kangquan; Li, Huali; Qiu, Jin-Long

2017-08-01

Pytohormone abscisic acid (ABA) plays important roles in defense responses. Nonetheless, how ABA regulates plant resistance to biotrophic fungi remains largely unknown. Arabidopsis ABA-deficient mutants, aba2-1 and aba3-1, displayed enhanced resistance to the biotrophic powdery mildew fungus Golovinomyces cichoracearum. Moreover, exogenously administered ABA increased the susceptibility of Arabidopsis to G. cichoracearum. Arabidopsis ABA perception components mutants, abi1-1 and abi2-1, also displayed similar phenotypes to ABA-deficient mutants in resistance to G. cichoracearum. However, the resistance to G. cichoracearum is not changed in downstream ABA signaling transduction mutants, abi3-1, abi4-1, and abi5-1. Microscopic examination revealed that hyphal growth and conidiophore production of G. cichoracearum were compromised in the ABA deficient mutants, even though pre-penetration and penetration growth of the fungus were not affected. In addition, salicylic acid (SA) and MPK3 are found to be involved in ABA-regulated resistance to G. cichoracearum. Our work demonstrates that ABA negatively regulates post-penetration resistance of Arabidopsis to powdery mildew fungus G. cichoracearum, probably through antagonizing the function of SA.

The regulation of vascular endothelial growth factor-induced microvascular permeability requires Rac and reactive oxygen species.

PubMed

Monaghan-Benson, Elizabeth; Burridge, Keith

2009-09-18

Vascular permeability is a complex process involving the coordinated regulation of multiple signaling pathways in the endothelial cell. It has long been documented that vascular endothelial growth factor (VEGF) greatly enhances microvascular permeability; however, the molecular mechanisms controlling VEGF-induced permeability remain unknown. Treatment of microvascular endothelial cells with VEGF led to an increase in reactive oxygen species (ROS) production. ROS are required for VEGF-induced permeability as treatment with the free radical scavenger, N-acetylcysteine, inhibited this effect. Additionally, treatment with VEGF caused ROS-dependent tyrosine phosphorylation of both vascular-endothelial (VE)-cadherin and beta-catenin. Rac1 was required for the VEGF-induced increase in permeability and adherens junction protein phosphorylation. Knockdown of Rac1 inhibited VEGF-induced ROS production consistent with Rac lying upstream of ROS in this pathway. Collectively, these data suggest that VEGF leads to a Rac-mediated generation of ROS, which, in turn, elevates the tyrosine phosphorylation of VE-cadherin and beta-catenin, ultimately regulating adherens junction integrity.

ORA47 (octadecanoid-responsive AP2/ERF-domain transcription factor 47) regulates jasmonic acid and abscisic acid biosynthesis and signaling through binding to a novel cis-element.

PubMed

Chen, Hsing-Yu; Hsieh, En-Jung; Cheng, Mei-Chun; Chen, Chien-Yu; Hwang, Shih-Ying; Lin, Tsan-Piao

2016-07-01

ORA47 (octadecanoid-responsive AP2/ERF-domain transcription factor 47) of Arabidopsis thaliana is an AP2/ERF domain transcription factor that regulates jasmonate (JA) biosynthesis and is induced by methyl JA treatment. The regulatory mechanism of ORA47 remains unclear. ORA47 is shown to bind to the cis-element (NC/GT)CGNCCA, which is referred to as the O-box, in the promoter of ABI2. We proposed that ORA47 acts as a connection between ABA INSENSITIVE1 (ABI1) and ABI2 and mediates an ABI1-ORA47-ABI2 positive feedback loop. PORA47:ORA47-GFP transgenic plants were used in a chromatin immunoprecipitation (ChIP) assay to show that ORA47 participates in the biosynthesis and/or signaling pathways of nine phytohormones. Specifically, many abscisic acid (ABA) and JA biosynthesis and signaling genes were direct targets of ORA47 under stress conditions. The JA content of the P35S:ORA47-GR lines was highly induced under wounding and moderately induced under water stress relative to that of the wild-type plants. The wounding treatment moderately increased ABA accumulation in the transgenic lines, whereas the water stress treatment repressed the ABA content. ORA47 is proposed to play a role in the biosynthesis of JA and ABA and in regulating the biosynthesis and/or signaling of a suite of phytohormone genes when plants are subjected to wounding and water stress. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Differences in respiration between dormant and non-dormant buds suggest the involvement of ABA in the development of endodormancy in grapevines.

PubMed

Parada, Francisca; Noriega, Ximena; Dantas, Débora; Bressan-Smith, Ricardo; Pérez, Francisco J

2016-08-20

Grapevine buds (Vitis vinifera L) enter endodormancy (ED) after perceiving the short-day (SD) photoperiod signal and undergo metabolic changes that allow them to survive the winter temperatures. In the present study, we observed an inverse relationship between the depth of ED and the respiration rate of grapevine buds. Moreover, the respiration of dormant and non-dormant buds differed in response to temperature and glucose, two stimuli that normally increase respiration in plant tissues. While respiration in non-dormant buds rose sharply in response to both stimuli, respiration in dormant buds was only slightly affected. This suggests that a metabolic inhibitor is present. Here, we propose that the plant hormone abscisic acid (ABA) could be this inhibitor. ABA inhibits respiration in non-dormant buds and represses the expression of respiratory genes, such as ALTERNATIVE NADH DEHYDROGENASE (VaND1, VvaND2), CYTOCHROME OXIDASE (VvCOX6) and CYTOCHROME C (VvCYTC), and induces the expression of VvSnRK1, a gene encoding a member of a highly conserved family of protein kinases that act as energy sensors and regulate gene expression in response to energy depletion. In addition to inducing ED the SD-photoperiod up-regulated the expression of VvNCED, a gene that encodes a key enzyme in ABA synthesis. Taken together, these results suggest that ABA through the mediation of VvSnRK1, could play a key role in the regulation of the metabolic changes accompanying the entry into ED of grapevine buds. Copyright © 2016 Elsevier GmbH. All rights reserved.

ABA signaling in stress-response and seed development.

PubMed

Nakashima, Kazuo; Yamaguchi-Shinozaki, Kazuko

2013-07-01

KEY MESSAGE : We review the recent progress on ABA signaling, especially ABA signaling for ABA-dependent gene expression, including the AREB/ABF regulon, SnRK2 protein kinase, 2C-type protein phosphatases and ABA receptors. Drought negatively impacts plant growth and the productivity of crops. Drought causes osmotic stress to organisms, and the osmotic stress causes dehydration in plant cells. Abscisic acid (ABA) is produced under osmotic stress conditions, and it plays an important role in the stress response and tolerance of plants. ABA regulates many genes under osmotic stress conditions. It also regulates gene expression during seed development and germination. The ABA-responsive element (ABRE) is the major cis-element for ABA-responsive gene expression. ABRE-binding protein (AREB)/ABRE-binding factor (ABF) transcription factors (TFs) regulate ABRE-dependent gene expression. Other TFs are also involved in ABA-responsive gene expression. SNF1-related protein kinases 2 are the key regulators of ABA signaling including the AREB/ABF regulon. Recently, ABA receptors and group A 2C-type protein phosphatases were shown to govern the ABA signaling pathway. Moreover, recent studies have suggested that there are interactions between the major ABA signaling pathway and other signaling factors in stress-response and seed development. The control of the expression of ABA signaling factors may improve tolerance to environmental stresses.

Early bioelectric activities mediate redox-modulated regeneration

PubMed Central

Ferreira, Fernando; Luxardi, Guillaume; Reid, Brian

2016-01-01

Reactive oxygen species (ROS) and electric currents modulate regeneration; however, the interplay between biochemical and biophysical signals during regeneration remains poorly understood. We investigate the interactions between redox and bioelectric activities during tail regeneration in Xenopus laevis tadpoles. We show that inhibition of NADPH oxidase-mediated production of ROS, or scavenging or blocking their diffusion into cells, impairs regeneration and consistently regulates the dynamics of membrane potential, transepithelial potential (TEP) and electric current densities (JI) during regeneration. Depletion of ROS mimics the altered TEP and JI observed in the non-regenerative refractory period. Short-term application of hydrogen peroxide (H2O2) rescues (from depleted ROS) and induces (from the refractory period) regeneration, TEP increase and JI reversal. H2O2 is therefore necessary for and sufficient to induce regeneration and to regulate TEP and JI. Epistasis assays show that voltage-gated Na+ channels act downstream of H2O2 to modulate regeneration. Altogether, these results suggest a novel mechanism for regeneration via redox-bioelectric orchestration. PMID:27827821

miR394 and LCR are involved in Arabidopsis salt and drought stress responses in an abscisic acid-dependent manner

PubMed Central

2013-01-01

Background MicroRNAs (miRNAs) are a class of short, endogenous non-coding small RNAs that have ability to base pair with their target mRNAs to induce their degradation in plants. miR394a/b are conserved small RNAs and its target gene LCR (LEAF CURLING RESPONSIVENESS) encodes an F-box protein (SKP1-Cullin/CDC53-F-box) but whether miR394a/b and its target gene LCR are involved in regulation of plant response to abscisic acid (ABA) and abiotic stresses is unknown. Results Mature miR394 and precursor miR394a/b are shown to be slightly induced by ABA. By contrast, LCR expression is depressed by ABA. Analysis of LCR and its promoter (pLCR::GUS) revealed that LCR is expressed at all development stages. MIR394a/b over-expression (35S::MIR394a/b) and lcr (LCR loss of function) mutant plants are hypersensitive to salt stress, but LCR over-expressing (35S::m5LCR) plants display the salt-tolerant phenotype. Both 35S::MIR394a/b and lcr plants are highly tolerant to severe drought stress compared with wild-type, but 35S::m5LCR plants are susceptible to water deficiency. Over-expression of MIR394a/b led to ABA hypersensitivity and ABA-associated phenotypes, whereas 35S::m5LCR plants show ABA resistance phenotypes. Moreover, 35S::MIR394a/b plants accumulated higher levels of ABA-induced hydrogen peroxide and superoxide anion radicals than wild-type and 35S::m5LCR plants. Expressions of ABA- and stress-responsive genes, ABI3, ABI4, ABI5, ABF3, and ABF4 are up-regulated in MIR394a/b over-expressing plants but down-regulated in 35S::m5LCR plants. Over-expression of MIR394a in abi4-1 or abi5-1 background resulted in loss of ABA-sensitivity in 35S::MIR394a plants. Conclusions The silencing of LCR mRNA by miR394 is essential to maintain a certain phenotype favorable for the adaptive response to abiotic stresses. The contrasting phenotypes of salt and drought responses may be mediated by a functional balance between miR394 and LCR. If the balance is perturbed in case of the abiotic stress, an identical phenotype related to the stress response occurs, resulting in either ABA sensitive or insensitive response. Thus, miR394-regulated LCR abundance may allow plants to fine-tune their responses to ABA and abiotic stress. PMID:24330668

miR394 and LCR are involved in Arabidopsis salt and drought stress responses in an abscisic acid-dependent manner.

PubMed

Song, Jian Bo; Gao, Shuai; Sun, Di; Li, Hua; Shu, Xia Xia; Yang, Zhi Min

2013-12-11

MicroRNAs (miRNAs) are a class of short, endogenous non-coding small RNAs that have ability to base pair with their target mRNAs to induce their degradation in plants. miR394a/b are conserved small RNAs and its target gene LCR (LEAF CURLING RESPONSIVENESS) encodes an F-box protein (SKP1-Cullin/CDC53-F-box) but whether miR394a/b and its target gene LCR are involved in regulation of plant response to abscisic acid (ABA) and abiotic stresses is unknown. Mature miR394 and precursor miR394a/b are shown to be slightly induced by ABA. By contrast, LCR expression is depressed by ABA. Analysis of LCR and its promoter (pLCR::GUS) revealed that LCR is expressed at all development stages. MIR394a/b over-expression (35S::MIR394a/b) and lcr (LCR loss of function) mutant plants are hypersensitive to salt stress, but LCR over-expressing (35S::m5LCR) plants display the salt-tolerant phenotype. Both 35S::MIR394a/b and lcr plants are highly tolerant to severe drought stress compared with wild-type, but 35S::m5LCR plants are susceptible to water deficiency. Over-expression of MIR394a/b led to ABA hypersensitivity and ABA-associated phenotypes, whereas 35S::m5LCR plants show ABA resistance phenotypes. Moreover, 35S::MIR394a/b plants accumulated higher levels of ABA-induced hydrogen peroxide and superoxide anion radicals than wild-type and 35S::m5LCR plants. Expressions of ABA- and stress-responsive genes, ABI3, ABI4, ABI5, ABF3, and ABF4 are up-regulated in MIR394a/b over-expressing plants but down-regulated in 35S::m5LCR plants. Over-expression of MIR394a in abi4-1 or abi5-1 background resulted in loss of ABA-sensitivity in 35S::MIR394a plants. The silencing of LCR mRNA by miR394 is essential to maintain a certain phenotype favorable for the adaptive response to abiotic stresses. The contrasting phenotypes of salt and drought responses may be mediated by a functional balance between miR394 and LCR. If the balance is perturbed in case of the abiotic stress, an identical phenotype related to the stress response occurs, resulting in either ABA sensitive or insensitive response. Thus, miR394-regulated LCR abundance may allow plants to fine-tune their responses to ABA and abiotic stress.

Establishing glucose- and ABA-regulated transcription networks in Arabidopsis by microarray analysis and promoter classification using a Relevance Vector Machine.

PubMed

Li, Yunhai; Lee, Kee Khoon; Walsh, Sean; Smith, Caroline; Hadingham, Sophie; Sorefan, Karim; Cawley, Gavin; Bevan, Michael W

2006-03-01

Establishing transcriptional regulatory networks by analysis of gene expression data and promoter sequences shows great promise. We developed a novel promoter classification method using a Relevance Vector Machine (RVM) and Bayesian statistical principles to identify discriminatory features in the promoter sequences of genes that can correctly classify transcriptional responses. The method was applied to microarray data obtained from Arabidopsis seedlings treated with glucose or abscisic acid (ABA). Of those genes showing >2.5-fold changes in expression level, approximately 70% were correctly predicted as being up- or down-regulated (under 10-fold cross-validation), based on the presence or absence of a small set of discriminative promoter motifs. Many of these motifs have known regulatory functions in sugar- and ABA-mediated gene expression. One promoter motif that was not known to be involved in glucose-responsive gene expression was identified as the strongest classifier of glucose-up-regulated gene expression. We show it confers glucose-responsive gene expression in conjunction with another promoter motif, thus validating the classification method. We were able to establish a detailed model of glucose and ABA transcriptional regulatory networks and their interactions, which will help us to understand the mechanisms linking metabolism with growth in Arabidopsis. This study shows that machine learning strategies coupled to Bayesian statistical methods hold significant promise for identifying functionally significant promoter sequences.

NOX4-mediated ROS production induces apoptotic cell death via down-regulation of c-FLIP and Mcl-1 expression in combined treatment with thioridazine and curcumin.

PubMed

Seo, Seung Un; Kim, Tae Hwan; Kim, Dong Eun; Min, Kyoung-Jin; Kwon, Taeg Kyu

2017-10-01

Thioridazine is known to have anti-tumor effects by inhibiting PI3K/Akt signaling, which is an important signaling pathway in cell survival. However, thioridazine alone does not induce apoptosis in head and neck squamous cell carcinoma (AMC-HN4), human breast carcinoma (MDA-MB231), and human glioma (U87MG) cells. Therefore, we investigated whether combined treatment with thioridazine and curcumin induces apoptosis. Combined treatment with thioridazine and curcumin markedly induced apoptosis in cancer cells without inducing apoptosis in human normal mesangial cells and human normal umbilical vein cells (EA.hy926). We found that combined treatment with thioridazine and curcumin had synergistic effects in AMC-HN4 cells. Among apoptosis-related proteins, thioridazine plus curcumin induced down-regulation of c-FLIP and Mcl-1 expression at the post-translational levels in a proteasome-dependent manner. Augmentation of proteasome activity was related to the up-regulation of proteasome subunit alpha 5 (PSMA5) expression in curcumin plus thioridazine-treated cells. Combined treatment with curcumin and thioridazine produced intracellular ROS in a NOX4-dependent manner, and ROS-mediated activation of Nrf2/ARE signaling played a critical role in the up-regulation of PSMA5 expression. Furthermore, ectopic expression of c-FLIP and Mcl-1 inhibited apoptosis in thioridazine and curcumin-treated cells. Therefore, we demonstrated that thioridazine plus curcumin induces proteasome activity by up-regulating PSMA5 expression via NOX4-mediated ROS production and that down-regulation of c-FLIP and Mcl-1 expression post-translationally is involved in apoptosis. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Transcriptomic analysis of rice aleurone cells identified a novel abscisic acid response element.

PubMed

Watanabe, Kenneth A; Homayouni, Arielle; Gu, Lingkun; Huang, Kuan-Ying; Ho, Tuan-Hua David; Shen, Qingxi J

2017-09-01

Seeds serve as a great model to study plant responses to drought stress, which is largely mediated by abscisic acid (ABA). The ABA responsive element (ABRE) is a key cis-regulatory element in ABA signalling. However, its consensus sequence (ACGTG(G/T)C) is present in the promoters of only about 40% of ABA-induced genes in rice aleurone cells, suggesting other ABREs may exist. To identify novel ABREs, RNA sequencing was performed on aleurone cells of rice seeds treated with 20 μM ABA. Gibbs sampling was used to identify enriched elements, and particle bombardment-mediated transient expression studies were performed to verify the function. Gene ontology analysis was performed to predict the roles of genes containing the novel ABREs. This study revealed 2443 ABA-inducible genes and a novel ABRE, designated as ABREN, which was experimentally verified to mediate ABA signalling in rice aleurone cells. Many of the ABREN-containing genes are predicted to be involved in stress responses and transcription. Analysis of other species suggests that the ABREN may be monocot specific. This study also revealed interesting expression patterns of genes involved in ABA metabolism and signalling. Collectively, this study advanced our understanding of diverse cis-regulatory sequences and the transcriptomes underlying ABA responses in rice aleurone cells. © 2017 John Wiley & Sons Ltd.

Redox Regulation of Mitochondrial Function

PubMed Central

Handy, Diane E.

2012-01-01

Abstract Redox-dependent processes influence most cellular functions, such as differentiation, proliferation, and apoptosis. Mitochondria are at the center of these processes, as mitochondria both generate reactive oxygen species (ROS) that drive redox-sensitive events and respond to ROS-mediated changes in the cellular redox state. In this review, we examine the regulation of cellular ROS, their modes of production and removal, and the redox-sensitive targets that are modified by their flux. In particular, we focus on the actions of redox-sensitive targets that alter mitochondrial function and the role of these redox modifications on metabolism, mitochondrial biogenesis, receptor-mediated signaling, and apoptotic pathways. We also consider the role of mitochondria in modulating these pathways, and discuss how redox-dependent events may contribute to pathobiology by altering mitochondrial function. Antioxid. Redox Signal. 16, 1323–1367. PMID:22146081

Solanum lycopersicum IAA15 functions in the 2,4-dichlorophenoxyacetic acid herbicide mechanism of action by mediating abscisic acid signalling.

PubMed

Xu, Tao; Wang, Yanling; Liu, Xin; Gao, Song; Qi, Mingfang; Li, Tianlai

2015-07-01

2,4-Dichlorophenoxyacetic acid (2,4-D), an important plant growth regulator, is the herbicide most commonly used worldwide to control weeds. However, broad-leaf fruits and vegetables are extremely sensitive to herbicides, which can cause damage and result in lost crops when applied in a manner inconsistent with the directions. Despite detailed knowledge of the mechanism of 2,4-D, the regulation of auxin signalling is still unclear. For example, although the major mediators of auxin signalling, including auxin/indole acetic acid (AUX/IAA) proteins and auxin response factors (ARFs), are known to mediate auxinic herbicides, the underlying mechanisms are still unclear. In this study, the effects of 2,4-D on AUX/IAA gene expression in tomato were investigated, and the two most notably up-regulated genes, SlIAA15 and SlIAA29, were selected for further study. Western blotting revealed the substantial accumulation of both SlIAA15 and SlIAA29, and the expression levels of the corresponding genes were increased following abscisic acid (ABA) and ethylene treatment. Overexpressing SlIAA15, but not SlIAA29, induced a 2,4-D herbicide damage phenotype. The 35S::SlIAA15 line exhibited a strong reduction in leaf stomatal density and altered expression of some R2R3 MYB genes that are putatively involved in the regulation of stomatal differentiation. Further study revealed that root elongation in 35S::SlIAA15 was sensitive to ABA treatment, and was most probably due to the altered expression of an ABA signal transduction gene. In addition, the altered auxin sensitivities of SlIAA15 transformants were also explored. These results suggested that SlIAA15 plays an important role in determining the effects of the herbicide 2,4-D. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

A role for intestinal TLR4-driven inflammatory response during activity-based anorexia

PubMed Central

Belmonte, Liliana; Achamrah, Najate; Nobis, Séverine; Guérin, Charlène; Riou, Gaëtan; Bôle-Feysot, Christine; Boyer, Olivier; Richard, Vincent; Rego, Jean Claude Do; Déchelotte, Pierre; Goichon, Alexis; Coëffier, Moïse

2016-01-01

Anorexia nervosa (AN) is associated with low-grade systemic inflammation and altered gut microbiota. However, the molecular origin of the inflammation remains unknown. Toll-like receptors are key regulators of innate immune response and their activation seems also to be involved in the control of food intake. We used activity-based anorexia (ABA) model to investigate the role of TLR4 and its contribution in anorexia-associated low-grade inflammation. Here, we found that ABA affected early the intestinal inflammatory status and the hypothalamic response. Indeed, TLR4 was upregulated both on colonic epithelial cells and intestinal macrophages, leading to elevated downstream mucosal cytokine production. These mucosal changes occurred earlier than hypothalamic changes driving to increased levels of IL-1β and IL-1R1 as well as increased levels of plasma corticosterone. Paradoxically, TLR4-deficient mice exhibited greater vulnerability to ABA with increased mortality rate, suggesting a major contribution of TLR4-mediated responses during ABA-induced weight loss. PMID:27779218

A role for intestinal TLR4-driven inflammatory response during activity-based anorexia.

PubMed

Belmonte, Liliana; Achamrah, Najate; Nobis, Séverine; Guérin, Charlène; Riou, Gaëtan; Bôle-Feysot, Christine; Boyer, Olivier; Richard, Vincent; Rego, Jean Claude Do; Déchelotte, Pierre; Goichon, Alexis; Coëffier, Moïse

2016-10-25

Anorexia nervosa (AN) is associated with low-grade systemic inflammation and altered gut microbiota. However, the molecular origin of the inflammation remains unknown. Toll-like receptors are key regulators of innate immune response and their activation seems also to be involved in the control of food intake. We used activity-based anorexia (ABA) model to investigate the role of TLR4 and its contribution in anorexia-associated low-grade inflammation. Here, we found that ABA affected early the intestinal inflammatory status and the hypothalamic response. Indeed, TLR4 was upregulated both on colonic epithelial cells and intestinal macrophages, leading to elevated downstream mucosal cytokine production. These mucosal changes occurred earlier than hypothalamic changes driving to increased levels of IL-1β and IL-1R1 as well as increased levels of plasma corticosterone. Paradoxically, TLR4-deficient mice exhibited greater vulnerability to ABA with increased mortality rate, suggesting a major contribution of TLR4-mediated responses during ABA-induced weight loss.

Abscisic Acid Synthesis and Response

PubMed Central

Finkelstein, Ruth

2013-01-01

Abscisic acid (ABA) is one of the “classical” plant hormones, i.e. discovered at least 50 years ago, that regulates many aspects of plant growth and development. This chapter reviews our current understanding of ABA synthesis, metabolism, transport, and signal transduction, emphasizing knowledge gained from studies of Arabidopsis. A combination of genetic, molecular and biochemical studies has identified nearly all of the enzymes involved in ABA metabolism, almost 200 loci regulating ABA response, and thousands of genes regulated by ABA in various contexts. Some of these regulators are implicated in cross-talk with other developmental, environmental or hormonal signals. Specific details of the ABA signaling mechanisms vary among tissues or developmental stages; these are discussed in the context of ABA effects on seed maturation, germination, seedling growth, vegetative stress responses, stomatal regulation, pathogen response, flowering, and senescence. PMID:24273463

Comparative Study on Reagents Involved in Grape Bud Break and Their Effects on Different Metabolites and Related Gene Expression during Winter

PubMed Central

Khalil-Ur-Rehman, Muhammad; Wang, Wu; Xu, Yan-Shuai; Haider, Muhammad S.; Li, Chun-Xia; Tao, Jian-Min

2017-01-01

To elucidate promoting and inhibiting effects of hydrogen cynamide (HC) and abscisic acid (ABA) on quiescence release of grape buds, physiological and molecular approaches were used to explore the mechanisms of quiescence based on metabolic and gene expression analysis. Physiological and molecular mechanisms involved in bud quiescence of grape were studied before and after application of HC, ABA, and ABA-HC. The data showed that ABA inhibited proclamation of quiescence in grape buds and attenuated the influence of HC. Bud quiescence was promoted and regulated by HC and ABA pre-treatment on buds of grape cultivar “Shine Muscat” with 5% HC, 100 μM ABA and combination of ABA-HC (5% HC+100 μM ABA) during quiescence under forcing condition. Exogenous application of ABA elevated superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX) related specific activities, while catalase (CAT) activity was increased during initial period of forcing and then decreased. The concentration of plant growth hormones including gibberellins (GA) and indole acetic acid increased by HC application but decreased the ABA contents under forcing condition. ABA increased the fructose content during quiescence under forcing condition while sucrose and total soluble sugars peaked in HC treated buds as compared to control. Genes related to ABA pathway, protein phosphatase 2C (PP2C family) were down regulated in the buds treated with HC, ABA and ABA-HC as compared to control while two genes related to GA pathway (GID1 family), out of which one gene showed down regulation during initial period of forcing while other gene was up regulated in response to HC and ABA-HC treatments as compared to control. Exogenous ABA application up regulated genes related to antioxidant enzymes as compared to control. The gene probable fructose-bisphosphate aldolase 1, chloroplastic-like, was up regulated in response to ABA treatment as compared to control. Analysis of metabolites and related gene expression pattern would provide a comprehensive view of quiescence after HC, ABA, and ABA-HC treatments in grape buds which may helpful for ultimate improvement in table grape production. PMID:28824676

Transcriptional up-regulation of antioxidant genes by PPARδ inhibits angiotensin II-induced premature senescence in vascular smooth muscle cells.

PubMed

Kim, Hyo Jung; Ham, Sun Ah; Paek, Kyung Shin; Hwang, Jung Seok; Jung, Si Young; Kim, Min Young; Jin, Hanna; Kang, Eun Sil; Woo, Im Sun; Kim, Hye Jung; Lee, Jae Heun; Chang, Ki Churl; Han, Chang Woo; Seo, Han Geuk

2011-03-25

This study evaluated peroxisome proliferator-activated receptor (PPAR) δ as a potential target for therapeutic intervention in Ang II-induced senescence in human vascular smooth muscle cells (hVSMCs). Activation of PPARδ by GW501516, a specific agonist of PPARδ, significantly inhibited the Ang II-induced premature senescence of hVSMCs. Agonist-activated PPARδ suppressed the generation of Ang II-triggered reactive oxygen species (ROS) with a concomitant reduction in DNA damage. Notably, GW501516 up-regulated the expression of antioxidant genes, such as glutathione peroxidase 1, thioredoxin 1, manganese superoxide dismutase and heme oxygenase 1. siRNA-mediated down-regulation of these antioxidant genes almost completely abolished the effects of GW501516 on ROS production and premature senescence in hVSMCs treated with Ang II. Taken together, the enhanced transcription of antioxidant genes is responsible for the PPARδ-mediated inhibition of premature senescence through sequestration of ROS in hVSMCs treated with Ang II. Copyright © 2011 Elsevier Inc. All rights reserved.

Febuxostat, an Inhibitor of Xanthine Oxidase, Suppresses Lipopolysaccharide-Induced MCP-1 Production via MAPK Phosphatase-1-Mediated Inactivation of JNK

PubMed Central

Nomura, Johji; Busso, Nathalie; Ives, Annette; Tsujimoto, Syunsuke; Tamura, Mizuho; So, Alexander; Yamanaka, Yoshihiro

2013-01-01

Excess reactive oxygen species (ROS) formation can trigger various pathological conditions such as inflammation, in which xanthine oxidase (XO) is one major enzymatic source of ROS. Although XO has been reported to play essential roles in inflammatory conditions, the molecular mechanisms underlying the involvement of XO in inflammatory pathways remain unclear. Febuxostat, a selective and potent inhibitor of XO, effectively inhibits not only the generation of uric acid but also the formation of ROS. In this study, therefore, we examined the effects of febuxostat on lipopolysaccharide (LPS)-mediated inflammatory responses. Here we show that febuxostat suppresses LPS-induced MCP-1 production and mRNA expression via activating MAPK phosphatase-1 (MKP-1) which, in turn, leads to dephosphorylation and inactivation of JNK in macrophages. Moreover, these effects of febuxostat are mediated by inhibiting XO-mediated intracellular ROS production. Taken together, our data suggest that XO mediates LPS-induced phosphorylation of JNK through ROS production and MKP-1 inactivation, leading to MCP-1 production in macrophages. These studies may bring new insights into the novel role of XO in regulating inflammatory process through MAPK phosphatase, and demonstrate the potential use of XO inhibitor in modulating the inflammatory processes. PMID:24086554

Redox-regulated growth factor survival signaling.

PubMed

Woolley, John F; Corcoran, Aoife; Groeger, Gillian; Landry, William D; Cotter, Thomas G

2013-11-20

Once the thought of as unwanted byproducts of cellular respiration in eukaryotes, reactive oxygen species (ROS) have been shown to facilitate essential physiological roles. It is now understood that ROS are critical mediators of intracellular signaling. Control of signal transduction downstream of growth factor receptors by ROS is a complex process whose details are only recently coming to light. Indeed, recent evidence points to control of signal propagation by ROS at multiple levels in the typical cascade. Growth factor stimulation activates nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Noxs) at the membrane, producing superoxide in the extracellular matrix, which is catalyzed to the membrane-permeable hydrogen peroxide (H2O2) that mediates intracellular signaling events. The potential for H2O2, however, to disrupt cellular functions by damaging proteins and nucleic acids demands that its levels are kept in check by receptor-associated peroxiredoxins. This interplay of Nox and peroxiredoxin activity moderates levels of H2O2 sufficiently to modify signaling partners locally. Among the best studied of these partners are redox-controlled phosphatases that are inactivated by H2O2. Phosphatases regulate signal propagation downstream of receptors, and thus their inactivation allows a further level of control. Transmission of information further downstream to targets such as transcription factors, themselves regulated by ROS, completes this pathway. Thus, signal propagation or attenuation can be dictated by ROS at multiple points. Given the complex nature of these processes, we envisage the emerging trends in the field of redox signaling in the context of growth factor stimulation.

Magmas functions as a ROS regulator and provides cytoprotection against oxidative stress-mediated damages

PubMed Central

Srivastava, S; Sinha, D; Saha, P P; Marthala, H; D'Silva, P

2014-01-01

Redox imbalance generates multiple cellular damages leading to oxidative stress-mediated pathological conditions such as neurodegenerative diseases and cancer progression. Therefore, maintenance of reactive oxygen species (ROS) homeostasis is most important that involves well-defined antioxidant machinery. In the present study, we have identified for the first time a component of mammalian protein translocation machinery Magmas to perform a critical ROS regulatory function. Magmas overexpression has been reported in highly metabolically active tissues and cancer cells that are prone to oxidative damage. We found that Magmas regulates cellular ROS levels by controlling its production as well as scavenging. Magmas promotes cellular tolerance toward oxidative stress by enhancing antioxidant enzyme activity, thus preventing induction of apoptosis and damage to cellular components. Magmas enhances the activity of electron transport chain (ETC) complexes, causing reduced ROS production. Our results suggest that J-like domain of Magmas is essential for maintenance of redox balance. The function of Magmas as a ROS sensor was found to be independent of its role in protein import. The unique ROS modulatory role of Magmas is highlighted by its ability to increase cell tolerance to oxidative stress even in yeast model organism. The cytoprotective capability of Magmas against oxidative damage makes it an important candidate for future investigation in therapeutics of oxidative stress-related diseases. PMID:25165880

β-Aminobutyric acid increases abscisic acid accumulation and desiccation tolerance and decreases water use but fails to improve grain yield in two spring wheat cultivars under soil drying.

PubMed

Du, Yan-Lei; Wang, Zhen-Yu; Fan, Jing-Wei; Turner, Neil C; Wang, Tao; Li, Feng-Min

2012-08-01

A pot experiment was conducted to investigate the effect of the non-protein amino acid, β-aminobutyric acid (BABA), on the homeostasis between reactive oxygen species (ROS) and antioxidant defence during progressive soil drying, and its relationship with the accumulation of abscisic acid (ABA), water use, grain yield, and desiccation tolerance in two spring wheat (Triticum aestivum L.) cultivars released in different decades and with different yields under drought. Drenching the soil with 100 µM BABA increased drought-induced ABA production, leading to a decrease in the lethal leaf water potential (Ψ) used to measure desiccation tolerance, decreased water use, and increased water use efficiency for grain (WUEG) under moderate water stress. In addition, at severe water stress levels, drenching the soil with BABA reduced ROS production, increased antioxidant enzyme activity, and reduced the oxidative damage to lipid membranes. The data suggest that the addition of BABA triggers ABA accumulation that acts as a non-hydraulic root signal, thereby closing stomata, and reducing water use at moderate stress levels, and also reduces the production of ROS and increases the antioxidant defence enzymes at severe stress levels, thus increasing the desiccation tolerance. However, BABA treatment had no effect on grain yield of wheat when water availability was limited. The results suggest that there are ways of effectively priming the pre-existing defence pathways, in addition to genetic means, to improve the desiccation tolerance and WUEG of wheat.

Transcriptional up-regulation of antioxidant genes by PPAR{delta} inhibits angiotensin II-induced premature senescence in vascular smooth muscle cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Hyo Jung; Ham, Sun Ah; Paek, Kyung Shin

2011-03-25

Research highlights: {yields} Activation of PPAR{delta} by GW501516 significantly inhibited Ang II-induced premature senescence in hVSMCs. {yields} Agonist-activated PPAR{delta} suppressed generation of Ang II-triggered ROS with a concomitant reduction in DNA damage. {yields} GW501516 up-regulated expression of antioxidant genes, such as GPx1, Trx1, Mn-SOD and HO-1. {yields} Knock-down of these antioxidant genes abolished the effects of GW501516 on ROS production and premature senescence. -- Abstract: This study evaluated peroxisome proliferator-activated receptor (PPAR) {delta} as a potential target for therapeutic intervention in Ang II-induced senescence in human vascular smooth muscle cells (hVSMCs). Activation of PPAR{delta} by GW501516, a specific agonist ofmore » PPAR{delta}, significantly inhibited the Ang II-induced premature senescence of hVSMCs. Agonist-activated PPAR{delta} suppressed the generation of Ang II-triggered reactive oxygen species (ROS) with a concomitant reduction in DNA damage. Notably, GW501516 up-regulated the expression of antioxidant genes, such as glutathione peroxidase 1, thioredoxin 1, manganese superoxide dismutase and heme oxygenase 1. siRNA-mediated down-regulation of these antioxidant genes almost completely abolished the effects of GW501516 on ROS production and premature senescence in hVSMCs treated with Ang II. Taken together, the enhanced transcription of antioxidant genes is responsible for the PPAR{delta}-mediated inhibition of premature senescence through sequestration of ROS in hVSMCs treated with Ang II.« less

Mycobacterium avium MAV2052 protein induces apoptosis in murine macrophage cells through Toll-like receptor 4.

PubMed

Lee, Kang-In; Choi, Han-Gyu; Son, Yeo-Jin; Whang, Jake; Kim, Kwangwook; Jeon, Heat Sal; Park, Hye-Soo; Back, Yong Woo; Choi, Seunga; Kim, Seong-Woo; Choi, Chul Hee; Kim, Hwa-Jung

2016-04-01

Mycobacterium avium and its sonic extracts induce apoptosis in macrophages. However, little is known about the M. avium components regulating macrophage apoptosis. In this study, using multidimensional fractionation, we identified MAV2052 protein, which induced macrophage apoptosis in M. avium culture filtrates. The recombinant MAV2052 induced macrophage apoptosis in a caspase-dependent manner. The loss of mitochondrial transmembrane potential (ΔΨm), mitochondrial translocation of Bax, and release of cytochrome c from mitochondria were observed in macrophages treated with MAV2052. Further, reactive oxygen species (ROS) production was required for the apoptosis induced by MAV2052. In addition, ROS and mitogen-activated protein kinases were involved in MAV2052-mediated TNF-α and IL-6 production. ROS-mediated activation of apoptosis signal-regulating kinase 1 (ASK1)-JNK pathway was a major signaling pathway for MAV2052-induced apoptosis. Moreover, MAV2052 bound to Toll-like receptor (TLR) 4 molecule and MAV2052-induced ROS production, ΔΨm loss, and apoptosis were all significantly reduced in TLR4(-/-) macrophages. Altogether, our results suggest that MAV2052 induces apoptotic cell death through TLR4 dependent ROS production and JNK pathway in murine macrophages.

Analysis of plant hormone profiles in response to moderate dehydration stress.

PubMed

Urano, Kaoru; Maruyama, Kyonoshin; Jikumaru, Yusuke; Kamiya, Yuji; Yamaguchi-Shinozaki, Kazuko; Shinozaki, Kazuo

2017-04-01

Plant responses to dehydration stress are mediated by highly complex molecular systems involving hormone signaling and metabolism, particularly the major stress hormone abscisic acid (ABA) and ABA-dependent gene expression. To understand the roles of plant hormones and their interactions during dehydration, we analyzed the plant hormone profiles with respect to dehydration responses in Arabidopsis thaliana wild-type (WT) plants and ABA biosynthesis mutants (nced3-2). We developed a procedure for moderate dehydration stress, and then investigated temporal changes in the profiles of ABA, jasmonic acid isoleucine (JA-Ile), salicylic acid (SA), cytokinin (trans-zeatin, tZ), auxin (indole-acetic acid, IAA), and gibberellin (GA 4 ), along with temporal changes in the expression of key genes involved in hormone biosynthesis. ABA levels increased in a bi-phasic pattern (at the early and late phases) in response to moderate dehydration stress. JA-Ile levels increased slightly in WT plants and strongly increased in nced3-2 mutant plants at 72 h after the onset of dehydration. The expression profiles of dehydration-inducible genes displayed temporal responses in an ABA-dependent manner. The early phase of ABA accumulation correlated with the expression of touch-inducible genes and was independent of factors involved in the major ABA regulatory pathway, including the ABA-responsive element-binding (AREB/ABF) transcription factor. JA-Ile, SA, and tZ were negatively regulated during the late dehydration response phase. Transcriptome analysis revealed important roles for hormone-related genes in metabolism and signaling during dehydration-induced plant responses. © 2016 The Authors The Plant Journal © 2016 John Wiley & Sons Ltd.

Responses of In vitro-Grown Plantlets (Vitis vinifera) to Grapevine leafroll-Associated Virus-3 and PEG-Induced Drought Stress.

PubMed

Cui, Zhen-Hua; Bi, Wen-Lu; Hao, Xin-Yi; Xu, Yan; Li, Peng-Min; Walker, M Andrew; Wang, Qiao-Chun

2016-01-01

Stresses caused by viral diseases and drought have long threatened sustainable production of grapevine. These two stresses frequently occur simultaneously in many of grapevine growing regions of the world. We studied responses of in vitro-grown plantlets (Vitis vinifera) to Grapevine leafroll associated virus-3 (GLRaV-3) and PEG-induced drought stress. Results showed that stress induced by either virus infection or drought had negative effects on vegetative growth, caused significant decreases and increases in total soluble protein and free proline, respectively, induced obvious cell membrane damage and cell death, and markedly increased accumulations of [Formula: see text] and H2O2. Co-stress by virus and drought had much severer effects than single stress on the said parameters. Virus infection alone did not cause significant alternations in activities of POD, ROS, and SOD, and contents of MDA, which, however, markedly increased in the plantlets when grown under single drought stress and co-stress by the virus and drought. Levels of ABA increased, while those of IAA decreased in the plantlets stressed by virus infection or drought. Simultaneous stresses by the virus and drought had co-effects on the levels of ABA and IAA. Up-regulation of expressions of ABA biosynthesis genes and down-regulation of expressions of IAA biosynthesis genes were responsible for the alternations of ABA and IAA levels induced by either the virus infection or drought stress and co-stress by them. Experimental strategies established in the present study using in vitro system facilitate investigations on 'pure' biotic and abiotic stress on plants. The results obtained here provide new insights into adverse effects of stress induced by virus and drought, in single and particularly their combination, on plants, and allow us to re-orientate agricultural managements toward sustainable development of the agriculture.

Mitochondria-derived reactive oxygen species drive GANT61-induced mesothelioma cell apoptosis.

PubMed

Lim, Chuan Bian; Prêle, Cecilia M; Baltic, Svetlana; Arthur, Peter G; Creaney, Jenette; Watkins, D Neil; Thompson, Philip J; Mutsaers, Steven E

2015-01-30

Gli transcription factors of the Hedgehog (Hh) pathway have been reported to be drivers of malignant mesothelioma (MMe) cell survival. The Gli inhibitor GANT61 induces apoptosis in various cancer cell models, and has been associated directly with Gli inhibition. However various chemotherapeutics can induce cell death through generation of reactive oxygen species (ROS) but whether ROS mediates GANT61-induced apoptosis is unknown. In this study human MMe cells were treated with GANT61 and the mechanisms regulating cell death investigated. Exposure of MMe cells to GANT61 led to G1 phase arrest and apoptosis, which involved ROS but not its purported targets, GLI1 or GLI2. GANT61 triggered ROS generation and quenching of ROS protected MMe cells from GANT61-induced apoptosis. Furthermore, we demonstrated that mitochondria are important in mediating GANT61 effects: (1) ROS production and apoptosis were blocked by mitochondrial inhibitor rotenone; (2) GANT61 promoted superoxide formation in mitochondria; and (3) mitochondrial DNA-deficient LO68 cells failed to induce superoxide, and were more resistant to apoptosis induced by GANT61 than wild-type cells. Our data demonstrate for the first time that GANT61 induces apoptosis by promoting mitochondrial superoxide generation independent of Gli inhibition, and highlights the therapeutic potential of mitochondrial ROS-mediated anticancer drugs in MMe.

ABA-INSENSITIVE3, ABA-INSENSITIVE5, and DELLAs Interact to Activate the Expression of SOMNUS and Other High-Temperature-Inducible Genes in Imbibed Seeds in Arabidopsis[W

PubMed Central

Lim, Soohwan; Park, Jeongmoo; Lee, Nayoung; Jeong, Jinkil; Toh, Shigeo; Watanabe, Asuka; Kim, Junghyun; Kang, Hyojin; Kim, Dong Hwan; Kawakami, Naoto; Choi, Giltsu

2013-01-01

Seeds monitor the environment to germinate at the proper time, but different species respond differently to environmental conditions, particularly light and temperature. In Arabidopsis thaliana, light promotes germination but high temperature suppresses germination. We previously reported that light promotes germination by repressing SOMNUS (SOM). Here, we examined whether high temperature also regulates germination through SOM and found that high temperature activates SOM expression. Consistent with this, som mutants germinated more frequently than the wild type at high temperature. The induction of SOM mRNA at high temperature required abscisic acid (ABA) and gibberellic acid biosynthesis, and ABA-INSENSITIVE3 (ABI3), ABI5, and DELLAs positively regulated SOM expression. Chromatin immunoprecipitation assays indicated that ABI3, ABI5, and DELLAs all target the SOM promoter. At the protein level, ABI3, ABI5, and DELLAs all interact with each other, suggesting that they form a complex on the SOM promoter to activate SOM expression at high temperature. We found that high-temperature-inducible genes frequently have RY motifs and ABA-responsive elements in their promoters, some of which are targeted by ABI3, ABI5, and DELLAs in vivo. Taken together, our data indicate that ABI3, ABI5, and DELLAs mediate high-temperature signaling to activate the expression of SOM and other high-temperature-inducible genes, thereby inhibiting seed germination. PMID:24326588

Characterization of StABF1, a stress-responsive bZIP transcription factor from Solanum tuberosum L. that is phosphorylated by StCDPK2 in vitro.

PubMed

Muñiz García, María Noelia; Giammaria, Verónica; Grandellis, Carolina; Téllez-Iñón, María Teresa; Ulloa, Rita María; Capiati, Daniela Andrea

2012-04-01

ABF/AREB bZIP transcription factors mediate plant abiotic stress responses by regulating the expression of stress-related genes. These proteins bind to the abscisic acid (ABA)-responsive element (ABRE), which is the major cis-acting regulatory sequence in ABA-dependent gene expression. In an effort to understand the molecular mechanisms of abiotic stress resistance in cultivated potato (Solanum tuberosum L.), we have cloned and characterized an ABF/AREB-like transcription factor from potato, named StABF1. The predicted protein shares 45-57% identity with A. thaliana ABFs proteins and 96% identity with the S. lycopersicum SlAREB1 and presents all of the distinctive features of ABF/AREB transcription factors. Furthermore, StABF1 is able to bind to the ABRE in vitro. StABF1 gene is induced in response to ABA, drought, salt stress and cold, suggesting that it might be a key regulator of ABA-dependent stress signaling pathways in cultivated potato. StABF1 is phosphorylated in response to ABA and salt stress in a calcium-dependent manner, and we have identified a potato CDPK isoform (StCDPK2) that phosphorylates StABF1 in vitro. Interestingly, StABF1 expression is increased during tuber development and by tuber-inducing conditions (high sucrose/nitrogen ratio) in leaves. We also found that StABF1 calcium-dependent phosphorylation is stimulated by tuber-inducing conditions and inhibited by gibberellic acid, which inhibits tuberization.

Antidepressant effects of abscisic acid mediated by the downregulation of corticotrophin-releasing hormone gene expression in rats.

PubMed

Qi, Cong-Cong; Zhang, Zhi; Fang, Hui; Liu, Ji; Zhou, Nan; Ge, Jin-Fang; Chen, Fang-Han; Xiang, Cheng-Bin; Zhou, Jiang-Ning

2014-10-31

Corticotrophin-releasing hormone (CRH) is considered to be the central driving force of the hypothalamic-pituitary-adrenal axis, which plays a key role in the stress response and depression. Clinical reports have suggested that excess retinoic acid (RA) is associated with depression. Abscisic acid (ABA) and RA are direct derivatives of carotenoids and share a similar molecular structure. Here, we proposed that ABA also plays a role in the regulation of CRH activity sharing with the RA signaling pathway. [3H]-ABA radioimmunoassay demonstrated that the hypothalamus of rats shows the highest concentration of ABA compared with the cortex and the hippocampus under basal conditions. Under acute stress, ABA concentrations increased in the serum, but decreased in the hypothalamus and were accompanied by increased corticosterone in the serum and c-fos expression in the hypothalamus. Moreover, chronic ABA administration increased sucrose intake and decreased the mRNA expression of CRH and retinoic acid receptor alpha (RARα) in the hypothalamus of rats. Furthermore, ABA improved the symptom of chronic unpredictable mild stress in model rats, as indicated by increased sucrose intake, increased swimming in the forced swim test, and reduced mRNA expression of CRH and RARα in the rat hypothalamus. In vitro, CRH expression decreased after ABA treatment across different neural cells. In BE(2)-C cells, ABA inhibited a series of retinoid receptor expression, including RARα, a receptor that could facilitate CRH expression directly. These results suggest that ABA may play a role in the pathogenesis of depression by downregulating CRH mRNA expression shared with the RA signaling pathway. © The Author 2014. Published by Oxford University Press on behalf of CINP.

Reactive oxygen species activate differentiation gene transcription of acute myeloid leukemia cells via the JNK/c-JUN signaling pathway.

PubMed

Lam, Chung Fan; Yeung, Hoi Ting; Lam, Yuk Man; Ng, Ray Kit

2018-05-01

Reactive oxygen species (ROS) and altered cellular redox status are associated with many malignancies. Acute myeloid leukemia (AML) cells are maintained at immature state by differentiation blockade, which involves deregulation of transcription factors in myeloid differentiation. AML cells can be induced to differentiate by phorbol-12-myristate-13-acetate (PMA), which possesses pro-oxidative activity. However, the signaling events mediated by ROS in the activation of transcriptional program during AML differentiation has not been fully elucidated. Here, we investigated AML cell differentiation by treatment with PMA and ROS scavenger N-acetyl-l-cysteine (NAC). We observed elevation of intracellular ROS level in the PMA-treated AML cells, which correlated with differentiated cell morphology and increased CD11b + mature cell population. The effect of PMA can be abolished by NAC co-treatment, supporting the involvement of ROS in the process. Moreover, we demonstrated that short ROS elevation mediated cell cycle arrest, but failed to activate myeloid gene transcription; whereas prolonged ROS elevation activated JNK/c-JUN signaling pathway. Inhibition of JNK suppressed the expression of key myeloid transcriptional regulators c-JUN, SPI-1 and MAFB, and prevented AML cells from undergoing terminal differentiation. These findings provide new insights into the crucial role of JNK/c-Jun signaling pathway in the activation of transcriptional program during ROS-mediated AML differentiation. Copyright © 2018 Elsevier Ltd. All rights reserved.

Negative Regulation of Leptin-induced Reactive Oxygen Species (ROS) Formation by Cannabinoid CB1 Receptor Activation in Hypothalamic Neurons.

PubMed

Palomba, Letizia; Silvestri, Cristoforo; Imperatore, Roberta; Morello, Giovanna; Piscitelli, Fabiana; Martella, Andrea; Cristino, Luigia; Di Marzo, Vincenzo

2015-05-29

The adipocyte-derived, anorectic hormone leptin was recently shown to owe part of its regulatory effects on appetite-regulating hypothalamic neuropeptides to the elevation of reactive oxygen species (ROS) levels in arcuate nucleus (ARC) neurons. Leptin is also known to exert a negative regulation on hypothalamic endocannabinoid levels and hence on cannabinoid CB1 receptor activity. Here we investigated the possibility of a negative regulation by CB1 receptors of leptin-mediated ROS formation in the ARC. Through pharmacological and molecular biology experiments we report data showing that leptin-induced ROS accumulation is 1) blunted by arachidonyl-2'-chloroethylamide (ACEA) in a CB1-dependent manner in both the mouse hypothalamic cell line mHypoE-N41 and ARC neuron primary cultures, 2) likewise blocked by a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, troglitazone, in a manner inhibited by T0070907, a PPAR-γ antagonist that also inhibited the ACEA effect on leptin, 3) blunted under conditions of increased endocannabinoid tone due to either pharmacological or genetic inhibition of endocannabinoid degradation in mHypoE-N41 and primary ARC neuronal cultures from MAGL(-/-) mice, respectively, and 4) associated with reduction of both PPAR-γ and catalase activity, which are reversed by both ACEA and troglitazone. We conclude that CB1 activation reverses leptin-induced ROS formation and hence possibly some of the ROS-mediated effects of the hormone by preventing PPAR-γ inhibition by leptin, with subsequent increase of catalase activity. This mechanism might underlie in part CB1 orexigenic actions under physiopathological conditions accompanied by elevated hypothalamic endocannabinoid levels. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Comprehensive Analysis of ABA Effects on Ethylene Biosynthesis and Signaling during Tomato Fruit Ripening.

PubMed

Mou, Wangshu; Li, Dongdong; Bu, Jianwen; Jiang, Yuanyuan; Khan, Zia Ullah; Luo, Zisheng; Mao, Linchun; Ying, Tiejin

2016-01-01

ABA has been widely acknowledged to regulate ethylene biosynthesis and signaling during fruit ripening, but the molecular mechanism underlying the interaction between these two hormones are largely unexplored. In the present study, exogenous ABA treatment obviously promoted fruit ripening as well as ethylene emission, whereas NDGA (Nordihydroguaiaretic acid, an inhibitor of ABA biosynthesis) application showed the opposite biological effects. Combined RNA-seq with time-course RT-PCR analysis, our study not only helped to illustrate how ABA regulated itself at the transcription level, but also revealed that ABA can facilitate ethylene production and response probably by regulating some crucial genes such as LeACS4, LeACO1, GR and LeETR6. In addition, investigation on the fruits treated with 1-MCP immediately after ABA exposure revealed that ethylene might be essential for the induction of ABA biosynthesis and signaling at the onset of fruit ripening. Furthermore, some specific transcription factors (TFs) known as regulators of ethylene synthesis and sensibility (e.g. MADS-RIN, TAGL1, CNR and NOR) were also observed to be ABA responsive, which implied that ABA influenced ethylene action possibly through the regulation of these TFs expression. Our comprehensive physiological and molecular-level analysis shed light on the mechanism of cross-talk between ABA and ethylene during the process of tomato fruit ripening.

Comprehensive Analysis of ABA Effects on Ethylene Biosynthesis and Signaling during Tomato Fruit Ripening

PubMed Central

Bu, Jianwen; Jiang, Yuanyuan; Khan, Zia Ullah; Luo, Zisheng; Mao, Linchun; Ying, Tiejin

2016-01-01

ABA has been widely acknowledged to regulate ethylene biosynthesis and signaling during fruit ripening, but the molecular mechanism underlying the interaction between these two hormones are largely unexplored. In the present study, exogenous ABA treatment obviously promoted fruit ripening as well as ethylene emission, whereas NDGA (Nordihydroguaiaretic acid, an inhibitor of ABA biosynthesis) application showed the opposite biological effects. Combined RNA-seq with time-course RT-PCR analysis, our study not only helped to illustrate how ABA regulated itself at the transcription level, but also revealed that ABA can facilitate ethylene production and response probably by regulating some crucial genes such as LeACS4, LeACO1, GR and LeETR6. In addition, investigation on the fruits treated with 1-MCP immediately after ABA exposure revealed that ethylene might be essential for the induction of ABA biosynthesis and signaling at the onset of fruit ripening. Furthermore, some specific transcription factors (TFs) known as regulators of ethylene synthesis and sensibility (e.g. MADS-RIN, TAGL1, CNR and NOR) were also observed to be ABA responsive, which implied that ABA influenced ethylene action possibly through the regulation of these TFs expression. Our comprehensive physiological and molecular-level analysis shed light on the mechanism of cross-talk between ABA and ethylene during the process of tomato fruit ripening. PMID:27100326

Enhanced Secondary- and Hormone Metabolism in Leaves of Arbuscular Mycorrhizal Medicago truncatula1[OPEN

PubMed Central

Adolfsson, Lisa; Šimura, Jan; Beebo, Azeez; Aboalizadeh, Jila; Široká, Jitka

2017-01-01

Arbuscular mycorrhizas (AM) are the most common symbiotic associations between a plant’s root compartment and fungi. They provide nutritional benefit (mostly inorganic phosphate [Pi]), leading to improved growth, and nonnutritional benefits, including defense responses to environmental cues throughout the host plant, which, in return, delivers carbohydrates to the symbiont. However, how transcriptional and metabolic changes occurring in leaves of AM plants differ from those induced by Pi fertilization is poorly understood. We investigated systemic changes in the leaves of mycorrhized Medicago truncatula in conditions with no improved Pi status and compared them with those induced by high-Pi treatment in nonmycorrhized plants. Microarray-based genome-wide profiling indicated up-regulation by mycorrhization of genes involved in flavonoid, terpenoid, jasmonic acid (JA), and abscisic acid (ABA) biosynthesis as well as enhanced expression of MYC2, the master regulator of JA-dependent responses. Accordingly, total anthocyanins and flavonoids increased, and most flavonoid species were enriched in AM leaves. Both the AM and Pi treatments corepressed iron homeostasis genes, resulting in lower levels of available iron in leaves. In addition, higher levels of cytokinins were found in leaves of AM- and Pi-treated plants, whereas the level of ABA was increased specifically in AM leaves. Foliar treatment of nonmycorrhized plants with either ABA or JA induced the up-regulation of MYC2, but only JA also induced the up-regulation of flavonoid and terpenoid biosynthetic genes. Based on these results, we propose that mycorrhization and Pi fertilization share cytokinin-mediated improved shoot growth, whereas enhanced ABA biosynthesis and JA-regulated flavonoid and terpenoid biosynthesis in leaves are specific to mycorrhization. PMID:28698354

Enhanced Secondary- and Hormone Metabolism in Leaves of Arbuscular Mycorrhizal Medicago truncatula.

PubMed

Adolfsson, Lisa; Nziengui, Hugues; Abreu, Ilka N; Šimura, Jan; Beebo, Azeez; Herdean, Andrei; Aboalizadeh, Jila; Široká, Jitka; Moritz, Thomas; Novák, Ondřej; Ljung, Karin; Schoefs, Benoît; Spetea, Cornelia

2017-09-01

Arbuscular mycorrhizas (AM) are the most common symbiotic associations between a plant's root compartment and fungi. They provide nutritional benefit (mostly inorganic phosphate [P i ]), leading to improved growth, and nonnutritional benefits, including defense responses to environmental cues throughout the host plant, which, in return, delivers carbohydrates to the symbiont. However, how transcriptional and metabolic changes occurring in leaves of AM plants differ from those induced by P i fertilization is poorly understood. We investigated systemic changes in the leaves of mycorrhized Medicago truncatula in conditions with no improved P i status and compared them with those induced by high-P i treatment in nonmycorrhized plants. Microarray-based genome-wide profiling indicated up-regulation by mycorrhization of genes involved in flavonoid, terpenoid, jasmonic acid (JA), and abscisic acid (ABA) biosynthesis as well as enhanced expression of MYC2 , the master regulator of JA-dependent responses. Accordingly, total anthocyanins and flavonoids increased, and most flavonoid species were enriched in AM leaves. Both the AM and P i treatments corepressed iron homeostasis genes, resulting in lower levels of available iron in leaves. In addition, higher levels of cytokinins were found in leaves of AM- and P i -treated plants, whereas the level of ABA was increased specifically in AM leaves. Foliar treatment of nonmycorrhized plants with either ABA or JA induced the up-regulation of MYC2 , but only JA also induced the up-regulation of flavonoid and terpenoid biosynthetic genes. Based on these results, we propose that mycorrhization and P i fertilization share cytokinin-mediated improved shoot growth, whereas enhanced ABA biosynthesis and JA-regulated flavonoid and terpenoid biosynthesis in leaves are specific to mycorrhization. © 2017 American Society of Plant Biologists. All Rights Reserved.

Transcriptome Analysis of ABA/JA-Dual Responsive Genes in Rice Shoot and Root.

PubMed

Kim, Jin-Ae; Bhatnagar, Nikita; Kwon, Soon Jae; Min, Myung Ki; Moon, Seok-Jun; Yoon, In Sun; Kwon, Taek-Ryoun; Kim, Sun Tae; Kim, Beom-Gi

2018-01-01

The phytohormone abscisic acid (ABA) enables plants to adapt to adverse environmental conditions through the modulation of metabolic pathways and of growth and developmental programs. We used comparative microarray analysis to identify genes exhibiting ABA-dependent expression and other hormone-dependent expression among them in Oryza sativa shoot and root. We identified 854 genes as significantly up- or down-regulated in root or shoot under ABA treatment condition. Most of these genes had similar expression profiles in root and shoot under ABA treatment condition, whereas 86 genes displayed opposite expression responses in root and shoot. To examine the crosstalk between ABA and other hormones, we compared the expression profiles of the ABA-dependently regulated genes under several different hormone treatment conditions. Interestingly, around half of the ABA-dependently expressed genes were also regulated by jasmonic acid based on microarray data analysis. We searched the promoter regions of these genes for cis-elements that could be responsible for their responsiveness to both hormones, and found that ABRE and MYC2 elements, among others, were common to the promoters of genes that were regulated by both ABA and JA. These results show that ABA and JA might have common gene expression regulation system and might explain why the JA could function for both abiotic and biotic stress tolerance.

Reactive Oxygen Species-Producing Myeloid Cells Act as a Bone Marrow Niche for Sterile Inflammation-Induced Reactive Granulopoiesis.

PubMed

Zhu, Haiyan; Kwak, Hyun-Jeong; Liu, Peng; Bajrami, Besnik; Xu, Yuanfu; Park, Shin-Young; Nombela-Arrieta, Cesar; Mondal, Subhanjan; Kambara, Hiroto; Yu, Hongbo; Chai, Li; Silberstein, Leslie E; Cheng, Tao; Luo, Hongbo R

2017-04-01

Both microbial infection and sterile inflammation augment bone marrow (BM) neutrophil production, but whether the induced accelerated granulopoiesis is mediated by a common pathway and the nature of such a pathway are poorly defined. We recently established that BM myeloid cell-derived reactive oxygen species (ROS) externally regulate myeloid progenitor proliferation and differentiation in bacteria-elicited emergency granulopoiesis. In this article, we show that BM ROS levels are also elevated during sterile inflammation. Similar to in microbial infection, ROS were mainly generated by the phagocytic NADPH oxidase in Gr1 + myeloid cells. The myeloid cells and their ROS were uniformly distributed in the BM when visualized by multiphoton intravital microscopy, and ROS production was both required and sufficient for sterile inflammation-elicited reactive granulopoiesis. Elevated granulopoiesis was mediated by ROS-induced phosphatase and tensin homolog oxidation and deactivation, leading to upregulated PtdIns(3,4,5)P3 signaling and increased progenitor cell proliferation. Collectively, these results demonstrate that, although infection-induced emergency granulopoiesis and sterile inflammation-elicited reactive granulopoiesis are triggered by different stimuli and are mediated by distinct upstream signals, the pathways converge to NADPH oxidase-dependent ROS production by BM myeloid cells. Thus, BM Gr1 + myeloid cells represent a key hematopoietic niche that supports accelerated granulopoiesis in infective and sterile inflammation. This niche may be an excellent target in various immune-mediated pathologies or immune reconstitution after BM transplantation. Copyright © 2017 by The American Association of Immunologists, Inc.

Reactive oxygen species-producing myeloid cells act as a bone marrow niche for sterile inflammation-induced reactive granulopoiesis

PubMed Central

Zhu, Haiyan; Kwak, Hyun-Jeong; Liu, Peng; Bajrami, Besnik; Xu, Yuanfu; Park, Shin-Young; Nombela-Arrieta, Cesar; Mondal, Subhanjan; Kambara, Hiroto; Yu, Hongbo; Chai, Li; Silberstein, Leslie E.; Cheng, Tao; Luo, Hongbo R.

2017-01-01

Summary Both microbial infection and sterile inflammation augment bone marrow (BM) neutrophil production, but whether the induced accelerated granulopoiesis is mediated by a common pathway and the nature of such a pathway are poorly defined. We recently established that BM myeloid cell-derived reactive oxygen species (ROS) externally regulate myeloid progenitor proliferation and differentiation in bacteria-elicited emergency granulopoiesis. Here we show that BM ROS levels are also elevated during sterile inflammation. Similar to in microbial infection, ROS were mainly generated by the phagocytic NADPH oxidase in Gr1+ myeloid cells. The myeloid cells and their ROS were uniformly distributed in the BM when visualized by multi-photon intravital microscopy, and ROS production was both required and sufficient for sterile inflammation-elicited reactive granulopoiesis. Elevated granulopoiesis was mediated by ROS-induced PTEN oxidation and deactivation leading to upregulated PtdIns(3,4,5)P3 signaling and increased progenitor cell proliferation. Collectively, these results demonstrate that although infection-induced emergency granulopoiesis and sterile inflammation-elicited reactive granulopoiesis are triggered by different stimuli and are mediated by distinct upstream signals, the pathways converge to NADPH oxidase-dependent ROS production by BM myeloid cells. Thus, BM Gr1+ myeloid cells represent a key hematopoietic niche that supports accelerated granulopoiesis in both infective and sterile inflammation. This niche may be an excellent target in various immune-mediated pathologies or immune reconstitution after BM transplantation. PMID:28235862

6-Shogaol enhances renal carcinoma Caki cells to TRAIL-induced apoptosis through reactive oxygen species-mediated cytochrome c release and down-regulation of c-FLIP(L) expression.

PubMed

Han, Min Ae; Woo, Seon Min; Min, Kyoung-jin; Kim, Shin; Park, Jong-Wook; Kim, Dong Eun; Kim, Sang Hyun; Choi, Yung Hyun; Kwon, Taeg Kyu

2015-02-25

6-Shogaol, a potent bioactive compound in ginger (Zingiber officinale Roscoe), has been reported for anti-inflammatory and anti-cancer activity. In this study, we investigated the effect of 6-shogaol to enhance tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis. The combined treatment with 6-shogaol and TRAIL markedly induces apoptosis in various cancer cells (renal carcinoma Caki cells, breast carcinoma MDA-MB-231 cells and glioma U118MG cells), but not in normal mesangial cells and normal mouse kidney cells. 6-Shogaol reduced the mitochondrial membrane potential (MMP) and released cytochrome c from mitochondria to cytosol via Bax activation. Furthermore, we found that 6-shogaol induced down-regulation of c-FLIP(L) expression at the post-translational levels and the overexpression of c-FLIP(L) markedly inhibited 6-shogaol plus TRAIL-induced apoptosis. Moreover, 6-shogaol increased reactive oxygen species (ROS) production in Caki cells. Pretreatment with ROS scavengers attenuated 6-shogaol plus TRAIL-induced apoptosis through inhibition of MMP reduction and down-regulation of c-FLIP(L) expression. In addition, 6-gingerol, another phenolic alkanone isolated from ginger, did not enhance TRAIL-induced apoptosis and down-regulate c-FLIP(L) expression. Taken together, our results demonstrated that 6-shogaol enhances TRAIL-mediated apoptosis in renal carcinoma Caki cells via ROS-mediated cytochrome c release and down-regulation of c-FLIP(L) expression. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

The role of abscisic acid in regulating cucumber fruit development and ripening and its transcriptional regulation.

PubMed

Wang, Yanping; Wang, Ya; Ji, Kai; Dai, Shengjie; Hu, Ying; Sun, Liang; Li, Qian; Chen, Pei; Sun, Yufei; Duan, Chaorui; Wu, Yan; Luo, Hao; Zhang, Dian; Guo, Yangdong; Leng, Ping

2013-03-01

Cucumber (Cucumis sativus L.), a kind of fruit usually harvested at the immature green stage, belongs to non-climacteric fruit. To investigate the contribution of abscisic acid (ABA) to cucumber fruit development and ripening, variation in ABA level was investigated and a peak in ABA level was found in pulp before fruit get fully ripe. To clarify this point further, exogenous ABA was applied to cucumber fruits at two different development stages. Results showed that ABA application at the turning stage promotes cucumber fruit ripening, while application at the immature green stage had inconspicuous effects. In addition, with the purpose of understanding the transcriptional regulation of ABA, two partial cDNAs of CsNCED1 and CsNCED2 encoding 9-cis-epoxycarotenoid dioxygenase (NCED), a key enzyme in ABA biosynthetic pathway; one partial cDNA of CsCYP707A1 for 8'-hydroxylase, a key enzyme in the oxidative catabolism of ABA and two partial cDNAs of CsBG1 and CsBG2 for β-glucosidase (BG) that hydrolyzes ABA glucose ester (ABA-GE) to release active ABA were cloned from cucumber. The DNA and deduced amino acid sequences of these obtained genes respectively showed high similarities to their homologous genes in other plants. Real-time PCR analysis revealed that ABA content may be regulated by its biosynthesis (CsNCEDs), catabolism (CsCYP707A1) and reactivation genes (CsBGs) at the transcriptional level during cucumber fruit development and ripening, in response to ABA application, dehydration and pollination, among which CsNCED1, CsCYP707A1 and CsBG1 were highly expressed in pulp and may play more important roles in regulating ABA metabolism. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Salt-specific regulation of the cytosolic O-acetylserine(thiol)lyase gene from Arabidopsis thaliana is dependent on abscisic acid.

PubMed

Barroso, C; Romero, L C; Cejudo, F J; Vega, J M; Gotor, C

1999-07-01

The expression of Atcys-3A gene coding for cytosolic O-acetylserine(thiol)lyase, a key enzyme in cysteine biosynthesis, from Arabidopsis thaliana is significantly induced by exposure to salt and heavy-metal stresses. Addition of NaCl to mature plants induced a rapid accumulation of the mRNA throughout the leaf lamina and roots, and later on in stems, being mainly restricted to vascular tissues. The salt-specific regulation of Atcys-3A was also mediated by abscisic acid (ABA) since: (1) exogenous addition of ABA to the culture medium mimicked the salt-induced plant response by raising the level of Atcys-3A transcript, and (2) Arabidopsis mutants aba-1 and abi2-1 were not able to respond to NaCl. Our results suggest that a high rate of cysteine biosynthesis is required in Arabidopsis under salt stress necessary for a plant protection or adaptation mechanism. This hypothesis was supported by the observation that intracellular levels of cysteine and glutathione increased up to 3-fold after salt treatment.

Involvement of Abscisic Acid in PSII Photodamage and D1 Protein Turnover for Light-Induced Premature Senescence of Rice Flag Leaves

PubMed Central

Wang, Fubiao; Liu, Jianchao; Chen, Minxue; Zhou, Lujian; Li, Zhaowei; Zhao, Qian; Pan, Gang; Zaidi, Syed-Hassan-Raza; Cheng, Fangmin

2016-01-01

D1 protein in the PSII reaction center is the major target of photodamage, and it exhibits the highest turnover rate among all the thylakoid proteins. In this paper, rice psf (premature senescence of flag leaves) mutant and its wild type were used to investigate the genotype-dependent alteration in PSII photo-damage and D1 protein turnover during leaf senescence and its relation to ABA accumulation in senescent leaves. The symptom and extent of leaf senescence of the psf mutant appeared to be sunlight-dependent under natural field condition. The psf also displayed significantly higher levels of ABA accumulation in senescent leaves than the wild type. However, the premature senescence lesion of psf leaves could be alleviated by shaded treatment, concomitantly with the strikingly suppressed ABA level in the shaded areas of flag leaves. The change in ABA concentration contributed to the regulation of shade-delayed leaf senescence. The participation of ABA in the timing of senescence initiation and in the subsequent rate of leaf senescence was closely associated with PSII photodamage and D1 protein turnover during leaf senescence, in which the transcriptional expression of several key genes (psbA, psbB, psbC and OsFtsH2) involved in D1 protein biosynthesis and PSII repair cycle was seriously suppressed by the significantly increased ABA level. This response resulted in the low rate of D1 protein synthesis and impaired repair recovery in the presence of ABA. The psf showed evidently decreased D1 protein amount in the senescent leaves. Both the inhibition of de novo synthesized D1 protein and the slow rate of proteolytic removal for the photodamaged D1 protein was among the most crucial steps for the linkage between light-dependent leaf senescence and the varying ABA concentration in psf mutant leaves. OsFtsH2 transcriptional expression possibly played an important role in the regulation of D1 protein turnover and PSII repair cycle in relation to ABA mediated leaf senescence. PMID:27532299

Stanniocalcin-1 Protects a Mouse Model from Renal Ischemia-Reperfusion Injury by Affecting ROS-Mediated Multiple Signaling Pathways.

PubMed

Liu, Dajun; Shang, Huiping; Liu, Ying

2016-07-12

Stanniocalcin-1 (STC-1) protects against renal ischemia-reperfusion injury (RIRI). However, the molecular mechanisms remain widely unknown. STC-1 inhibits reactive oxygen species (ROS), whereas most ROS-mediated pathways are associated with ischemic injury. Therefore, to explore the mechanism, the effects of STC-1 on ROS-medicated pathways were studied. Non-traumatic vascular clamps were used to establish RIRI mouse models. The serum levels of STC-1, interleukin-6 (IL-6), interferon (IFN) γ, P53, and capase-3 were measured by ELISA kits. Superoxide dismutase (SOD) and malondialdehyde (MDA) were measured by fluorescence spectrofluorometer. All these molecules changed significantly in a RIRI model mouse when compared with those in a sham control. Kidney cells were isolated from sham and model mice. STC-1 was overexpressed or knockout in these kidney cells. The molecules in ROS-medicated pathways were measured by real-time quantitative PCR and Western blot. The results showed that STC-1 is an effective ROS scavenger. The serum levels of STC-1, MDA and SOD activity were increased while the serum levels of IL-6, iIFN-γ, P53, and capase-3 were decreased in a model group when compared with a sham control (p < 0.05). Furthermore, the levels of STC-1,p53, phosphorylated mitogen-activated protein kinase kinase (p-MEKK-1), c-Jun N-terminal kinase (p-JNK), extracellular signal-regulated kinase (p-ERK), IkB kinase (p-IKK), nuclear factor (NF) κB, apoptosis signal-regulating kinase 1 (ASK-1) and caspase-3 changed significantly in kidney cells isolated from a RIRI model when compared to those isolated from a sham control (p < 0.05). Meanwhile, STC-1 overexpression or silence caused significant changes of the levels of these ROS-mediated molecules. Therefore, STC-1 maybe improve anti-inflammation, anti-oxidant and anti-apoptosis activities by affecting ROS-mediated pathways, especially the phospho-modifications of the respective proteins, resulting in the increase of SOD and reduce of capase-3, p53, IL-6 and IFN-γ.

Early bioelectric activities mediate redox-modulated regeneration.

PubMed

Ferreira, Fernando; Luxardi, Guillaume; Reid, Brian; Zhao, Min

2016-12-15

Reactive oxygen species (ROS) and electric currents modulate regeneration; however, the interplay between biochemical and biophysical signals during regeneration remains poorly understood. We investigate the interactions between redox and bioelectric activities during tail regeneration in Xenopus laevis tadpoles. We show that inhibition of NADPH oxidase-mediated production of ROS, or scavenging or blocking their diffusion into cells, impairs regeneration and consistently regulates the dynamics of membrane potential, transepithelial potential (TEP) and electric current densities (J I ) during regeneration. Depletion of ROS mimics the altered TEP and J I observed in the non-regenerative refractory period. Short-term application of hydrogen peroxide (H 2 O 2 ) rescues (from depleted ROS) and induces (from the refractory period) regeneration, TEP increase and J I reversal. H 2 O 2 is therefore necessary for and sufficient to induce regeneration and to regulate TEP and J I Epistasis assays show that voltage-gated Na + channels act downstream of H 2 O 2 to modulate regeneration. Altogether, these results suggest a novel mechanism for regeneration via redox-bioelectric orchestration. © 2016. Published by The Company of Biologists Ltd.

Abscisic acid-activated SNRK2 protein kinases function in the gene-regulation pathway of ABA signal transduction by phosphorylating ABA response element-binding factors.

PubMed

Kobayashi, Yuhko; Murata, Michiharu; Minami, Hideyuki; Yamamoto, Shuhei; Kagaya, Yasuaki; Hobo, Tokunori; Yamamoto, Akiko; Hattori, Tsukaho

2005-12-01

The plant hormone abscisic acid (ABA) induces gene expression via the ABA-response element (ABRE) present in the promoters of ABA-regulated genes. A group of bZIP proteins have been identified as ABRE-binding factors (ABFs) that activate transcription through this cis element. A rice ABF, TRAB1, has been shown to be activated via ABA-dependent phosphorylation. While a large number of signalling factors have been identified that are involved in stomatal regulation by ABA, relatively less is known about the ABA-signalling pathway that leads to gene expression. We have shown recently that three members of the rice SnRK2 protein kinase family, SAPK8, SAPK9 and SAPK10, are activated by ABA signal as well as by hyperosmotic stress. Here we show that transient overexpression in cultured cell protoplasts of these ABA-activated SnRK2 protein kinases leads to the activation of an ABRE-regulated promoter, suggesting that these kinases are involved in the gene-regulation pathway of ABA signalling. We further show several lines of evidence that these ABA-activated SnRK2 protein kinases directly phosphorylate TRAB1 in response to ABA. Kinetic analysis of SAPK10 activation and TRAB1 phosphorylation indicated that the latter immediately followed the former. TRAB1 was found to be phosphorylated not only in response to ABA, but also in response to hyperosmotic stress, which was interpreted as the consequence of phosphorylation of TRAB1 by hyperosmotically activated SAPKs. Physical interaction between TRAB1 and SAPK10 in vivo was demonstrated by a co-immunoprecipitation experiment. Finally, TRAB1 was phosphorylated in vitro by the ABA-activated SnRK2 protein kinases at Ser102, which is phosphorylated in vivo in response to ABA and is critical for the activation function.

Inhibition of FUSCA3 degradation at high temperature is dependent on ABA signaling and is regulated by the ABA/GA ratio.

PubMed

Chiu, Rex Shun; Saleh, Yazan; Gazzarrini, Sonia

2016-11-01

During seed imbibition at supra-optimal temperature, an increase in the abscisic acid (ABA)/gibberellin (GA) ratio imposes secondary dormancy to prevent germination (thermoinhibition). FUSCA3 (FUS3), a positive regulator of seed dormancy, accumulates in seeds imbibed at high temperature and increases ABA levels to inhibit germination. Recently, we showed that ABA inhibits FUS3 degradation at high temperature, and that ABA and high temperature also inhibit the ubiquitin-proteasome system, by dampening both proteasome activity and protein polyubiquitination. Here, we investigated the role of ABA signaling components and the ABA antagonizing hormone, GA, in the regulation of FUS3 levels. We show that the ABA receptor mutant, pyl1-1, is less sensitive to ABA and thermoinhibition. In this mutant background, FUS3 degradation in vitro is faster. Similarly, GA alleviates thermoinhibition and also increases FUS3 degradation. These results indicate that inhibition of FUS3 degradation at high temperature is dependent on a high ABA/GA ratio and a functional ABA signaling pathway. Thus, FUS3 constitutes an important node in ABA-GA crosstalk during germination at supra-optimal temperature.

Memory responses of jasmonic acid-associated Arabidopsis genes to a repeated dehydration stress.

PubMed

Liu, Ning; Staswick, Paul E; Avramova, Zoya

2016-11-01

Dehydration stress activates numerous genes co-regulated by diverse signaling pathways. Upon repeated exposures, however, a subset of these genes does not respond maintaining instead transcription at their initial pre-stressed levels ('revised-response' genes). Most of these genes are involved in jasmonic acid (JA) biosynthesis, JA-signaling and JA-mediated stress responses. How these JA-associated genes are regulated to provide different responses to similar dehydration stresses is an enigma. Here, we investigate molecular mechanisms that contribute to this transcriptional behavior. The memory-mechanism is stress-specific: one exposure to dehydration stress or to abscisic acid (ABA) is required to prevent transcription in the second. Both ABA-mediated and JA-mediated pathways are critical for the activation of these genes, but the two signaling pathways interact differently during a single or multiple encounters with dehydration stress. Synthesis of JA during the first (S1) but not the second dehydration stress (S2) accounts for the altered transcriptional responses. We propose a model for these memory responses, wherein lack of MYC2 and of JA synthesis in S2 is responsible for the lack of expression of downstream genes. The similar length of the memory displayed by different memory-type genes suggests biological relevance for transcriptional memory as a gene-regulating mechanism during recurring bouts of drought. © 2016 John Wiley & Sons Ltd.

Abscisic acid regulates pinoresinol-lariciresinol reductase gene expression and secoisolariciresinol accumulation in developing flax (Linum usitatissimum L.) seeds.

PubMed

Renouard, Sullivan; Corbin, Cyrielle; Lopez, Tatiana; Montguillon, Josiane; Gutierrez, Laurent; Lamblin, Frédéric; Lainé, Eric; Hano, Christophe

2012-01-01

Secoisolariciresinol diglucoside (SDG), the main phytoestrogenic lignan of Linum usitatissimum, is accumulated in the seed coat of flax during its development and pinoresinol-lariciresinol reductase (PLR) is a key enzyme in flax for its synthesis. The promoter of LuPLR1, a flax gene encoding a pinoresinol lariciresinol reductase, contains putative regulatory boxes related to transcription activation by abscisic acid (ABA). Gel mobility shift experiments evidenced an interaction of nuclear proteins extracted from immature flax seed coat with a putative cis-acting element involved in ABA response. As ABA regulates a number of physiological events during seed development and maturation we have investigated its involvement in the regulation of this lignan synthesis by different means. ABA and SDG accumulation time courses in the seed as well as LuPLR1 expression were first determined in natural conditions. These results showed that ABA timing and localization of accumulation in the flax seed coat could be correlated with the LuPLR1 gene expression and SDG biosynthesis. Experimental modulations of ABA levels were performed by exogenous application of ABA or fluridone, an inhibitor of ABA synthesis. When submitted to exogenous ABA, immature seeds synthesized 3-times more SDG, whereas synthesis of SDG was reduced in immature seeds treated with fluridone. Similarly, the expression of LuPLR1 gene in the seed coat was up-regulated by exogenous ABA and down-regulated when fluridone was applied. These results demonstrate that SDG biosynthesis in the flax seed coat is positively controlled by ABA through the transcriptional regulation of LuPLR1 gene.

Subcellular Redox Signaling.

PubMed

Zhu, Liping; Lu, Yankai; Zhang, Jiwei; Hu, Qinghua

2017-01-01

Oxidative and antioxidative system of cells and tissues maintains a balanced state under physiological conditions. A disruption in this balance of redox status has been associated with numerous pathological processes. Reactive oxygen species (ROS) as a major redox signaling generates in a spatiotemporally dependent manner. Subcellular organelles such as mitochondria, endoplasmic reticulum, plasma membrane and nuclei contribute to the production of ROS. In addition to downstream effects of ROS signaling regulated by average ROS changes in cytoplasm, whether subcelluar ROS mediate biological effect(s) has drawn greater attentions. With the advance in redox-sensitive probes targeted to different subcellular compartments, the investigation of subcellular ROS signaling and its associated cellular function has become feasible. In this review, we discuss the subcellular ROS signaling, with particular focus on mechanisms of subcellular ROS production and its downstream effects.

[Isolation of ABA-regulated genes in Oryza sativa through fluorescent differential display PCR (FDD-PCR)].

PubMed

Xu, Shou Ling; Shen, Si Shi; Xu, Zhi Hong; Xue, Hong Wei

2002-12-01

Abscisic acid (ABA) was critical in plant seed development and response to environmental factors such as stress situations. To study the possible ABA related signaling transduction pathways, we tried to isolate the ABA-regulated genes through fluorescent differential display PCR (FDD-PCR) technology using rice seedling as materials (treated with ABA for 2, 4, 8 and 12h). In the 17 fragments isolated, 14 and 3 clones were up-and down-regulated respectively. Sequence analyses revealed that the encoded proteins were involved in photosynthesis (7 fragments), signal transduction (1 fragments), transcription (2 fragments), metabolism and resistance (6 fragments), and unknown protein (1 fragments). 3 clones, encoding putative alpha/beta hydrolase fold, putative vacuolar H+ -ATPase B subunit, putative tyrosine phosphatase, were confirmed to be regulated under ABA treatment by RT-PCR and northern blot analysis. FDD-PCR and possible functional mechanisms of ABA were discussed.

Hydroxychavicol, a betel leaf component, inhibits prostate cancer through ROS-driven DNA damage and apoptosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gundala, Sushma Reddy; Yang, Chunhua; Mukkavilli, Rao

Dietary phytochemicals are excellent ROS-modulating agents and have been shown to effectively enhance ROS levels beyond toxic threshold in cancer cells to ensure their selective killing while leaving normal cells unscathed. Here we demonstrate that hydroxychavicol (HC), extracted and purified from Piper betel leaves, significantly inhibits growth and proliferation via ROS generation in human prostate cancer, PC-3 cells. HC perturbed cell-cycle kinetics and progression, reduced clonogenicity and mediated cytotoxicity by ROS-induced DNA damage leading to activation of several pro-apoptotic molecules. In addition, HC treatment elicited a novel autophagic response as evidenced by the appearance of acidic vesicular organelles and increasedmore » expression of autophagic markers, LC3-IIb and beclin-1. Interestingly, quenching of ROS with tiron, an antioxidant, offered significant protection against HC-induced inhibition of cell growth and down regulation of caspase-3, suggesting the crucial role of ROS in mediating cell death. The collapse of mitochondrial transmembrane potential by HC further revealed the link between ROS generation and induction of caspase-mediated apoptosis in PC-3 cells. Our data showed remarkable inhibition of prostate tumor xenografts by ∼ 72% upon daily oral administration of 150 mg/kg bw HC by quantitative tumor volume measurements and non-invasive real-time bioluminescent imaging. HC was well-tolerated at this dosing level without any observable toxicity. This is the first report to demonstrate the anti-prostate cancer efficacy of HC in vitro and in vivo, which is perhaps attributable to its selective prooxidant activity to eliminate cancer cells thus providing compelling grounds for future preclinical studies to validate its potential usefulness for prostate cancer management. - Highlights: • HC perturbs cell-cycle progression by induction of reactive oxygen species (ROS). • HC mediated cytotoxicity by ROS-induced DNA damage leading to apoptosis. • HC induced ROS-mediated autophagic response. • It inhibited prostate tumor growth by ∼ 72% without any observable toxicity. • Its anticancer efficacy is likely due to its selective prooxidant activity.« less

Folic acid protects against arsenic-mediated embryo toxicity by up-regulating the expression of Dvr1

PubMed Central

Ma, Yan; Zhang, Chen; Gao, Xiao-Bo; Luo, Hai-Yan; Chen, Yang; Li, Hui-hua; Ma, Xu; Lu, Cai-Ling

2015-01-01

As a nutritional factor, folic acid can prevent cardiac and neural defects during embryo development. Our previous study showed that arsenic impairs embryo development by down-regulating Dvr1/GDF1 expression in zebrafish. Here, we investigated whether folic acid could protect against arsenic-mediated embryo toxicity. We found that folic acid supplementation increases hatching and survival rates, decreases malformation rate and ameliorates abnormal cardiac and neural development of zebrafish embryos exposed to arsenite. Both real-time PCR analysis and whole in-mount hybridization showed that folic acid significantly rescued the decrease in Dvr1 expression caused by arsenite. Subsequently, our data demonstrated that arsenite significantly decreased cell viability and GDF1 mRNA and protein levels in HEK293ET cells, while folic acid reversed these effects. Folic acid attenuated the increase in subcellular reactive oxygen species (ROS) levels and oxidative adaptor p66Shc protein expression in parallel with the changes in GDF1 expression and cell viability. P66Shc knockdown significantly inhibited the production of ROS and the down-regulation of GDF1 induced by arsenite. Our data demonstrated that folic acid supplementation protected against arsenic-mediated embryo toxicity by up-regulating the expression of Dvr1/GDF1, and folic acid enhanced the expression of GDF1 by decreasing p66Shc expression and subcellular ROS levels. PMID:26537450

NADPH oxidase 2-derived reactive oxygen species signal contributes to bradykinin-induced matrix metalloproteinase-9 expression and cell migration in brain astrocytes

PubMed Central

2012-01-01

Background Matrix metalloproteinase-9 (MMP-9) plays a crucial role in pathological processes of brain inflammation, injury, and neurodegeneration. Moreover, bradykinin (BK) induces the expression of several inflammatory proteins in brain astrocytes. Recent studies have suggested that increased oxidative stress is implicated in the brain inflammation and injury. However, whether BK induced MMP-9 expression mediated through oxidative stress remains virtually unknown. Herein we investigated the role of redox signals in BK-induced MMP-9 expression in rat brain astrocytes (RBA-1 cells). Results In the study, we first demonstrated that reactive oxygen species (ROS) plays a crucial role in BK-induced MMP-9 expression in cultured brain astrocytes (in vitro) and animal brain tissue (in vivo) models. Next, BK-induced MMP-9 expression is mediated through a Ca2+-mediated PKC-α linking to p47phox/NADPH oxidase 2 (Nox2)/ROS signaling pathway. Nox2-dependent ROS generation led to activation and up-regulation of the downstream transcriptional factor AP-1 (i.e. c-Fos and c-Jun), which bound to MMP-9 promoter region, and thereby turned on transcription of MMP-9 gene. Functionally, BK-induced MMP-9 expression enhanced astrocytic migration. Conclusions These results demonstrated that in RBA-1 cells, activation of AP-1 (c-Fos/c-Jun) by the PKC-α-mediated Nox2/ROS signals is essential for up-regulation of MMP-9 and cell migration enhanced by BK. PMID:23176293

Pleiotrophin-induced endothelial cell migration is regulated by xanthine oxidase-mediated generation of reactive oxygen species.

PubMed

Tsirmoula, Sotiria; Lamprou, Margarita; Hatziapostolou, Maria; Kieffer, Nelly; Papadimitriou, Evangelia

2015-03-01

Pleiotrophin (PTN) is a heparin-binding growth factor that induces cell migration through binding to its receptor protein tyrosine phosphatase beta/zeta (RPTPβ/ζ) and integrin alpha v beta 3 (ανβ3). In the present work, we studied the effect of PTN on the generation of reactive oxygen species (ROS) in human endothelial cells and the involvement of ROS in PTN-induced cell migration. Exogenous PTN significantly increased ROS levels in a concentration and time-dependent manner in both human endothelial and prostate cancer cells, while knockdown of endogenous PTN expression in prostate cancer cells significantly down-regulated ROS production. Suppression of RPTPβ/ζ through genetic and pharmacological approaches, or inhibition of c-src kinase activity abolished PTN-induced ROS generation. A synthetic peptide that blocks PTN-ανβ3 interaction abolished PTN-induced ROS generation, suggesting that ανβ3 is also involved. The latter was confirmed in CHO cells that do not express β3 or over-express wild-type β3 or mutant β3Y773F/Y785F. PTN increased ROS generation in cells expressing wild-type β3 but not in cells not expressing or expressing mutant β3. Phosphoinositide 3-kinase (PI3K) or Erk1/2 inhibition suppressed PTN-induced ROS production, suggesting that ROS production lays down-stream of PI3K or Erk1/2 activation by PTN. Finally, ROS scavenging and xanthine oxidase inhibition completely abolished both PTN-induced ROS generation and cell migration, while NADPH oxidase inhibition had no effect. Collectively, these data suggest that xanthine oxidase-mediated ROS production is required for PTN-induced cell migration through the cell membrane functional complex of ανβ3 and RPTPβ/ζ and activation of c-src, PI3K and ERK1/2 kinases. Copyright © 2015 Elsevier Inc. All rights reserved.

GCN5L1 modulates cross-talk between mitochondria and cell signaling to regulate FoxO1 stability and gluconeogenesis.

PubMed

Wang, Lingdi; Scott, Iain; Zhu, Lu; Wu, Kaiyuan; Han, Kim; Chen, Yong; Gucek, Marjan; Sack, Michael N

2017-09-12

The mitochondrial enriched GCN5-like 1 (GCN5L1) protein has been shown to modulate mitochondrial protein acetylation, mitochondrial content and mitochondrial retrograde signaling. Here we show that hepatic GCN5L1 ablation reduces fasting glucose levels and blunts hepatic gluconeogenesis without affecting systemic glucose tolerance. PEPCK and G6Pase transcript levels are downregulated in hepatocytes from GCN5L1 liver specific knockout mice and their upstream regulator, FoxO1 protein levels are decreased via proteasome-dependent degradation and via reactive oxygen species mediated ERK-1/2 phosphorylation. ERK inhibition restores FoxO1, gluconeogenic enzyme expression and glucose production. Reconstitution of mitochondrial-targeted GCN5L1 blunts mitochondrial ROS, ERK activation and increases FoxO1, gluconeogenic enzyme expression and hepatocyte glucose production. We suggest that mitochondrial GCN5L1 modulates post-translational control of FoxO1, regulates gluconeogenesis and controls metabolic pathways via mitochondrial ROS mediated ERK activation. Exploring mechanisms underpinning GCN5L1 mediated ROS signaling may expand our understanding of the role of mitochondria in gluconeogenesis control.Hepatic gluconeogenesis is tightly regulated at transcriptional level and is essential for survival during prolonged fasting. Here Wang et al. show that the mitochondrial enriched GCN5-like 1 protein controls hepatic glucose production by regulating FoxO1 protein levels via proteasome-dependent degradation and, in turn, gluconeogenic gene expression.

Shoot-derived abscisic acid promotes root growth.

PubMed

McAdam, Scott A M; Brodribb, Timothy J; Ross, John J

2016-03-01

The phytohormone abscisic acid (ABA) plays a major role in regulating root growth. Most work to date has investigated the influence of root-sourced ABA on root growth during water stress. Here, we tested whether foliage-derived ABA could be transported to the roots, and whether this foliage-derived ABA had an influence on root growth under well-watered conditions. Using both application studies of deuterium-labelled ABA and reciprocal grafting between wild-type and ABA-biosynthetic mutant plants, we show that both ABA levels in the roots and root growth in representative angiosperms are controlled by ABA synthesized in the leaves rather than sourced from the roots. Foliage-derived ABA was found to promote root growth relative to shoot growth but to inhibit the development of lateral roots. Increased root auxin (IAA) levels in plants with ABA-deficient scions suggest that foliage-derived ABA inhibits root growth through the root growth-inhibitor IAA. These results highlight the physiological and morphological importance, beyond the control of stomata, of foliage-derived ABA. The use of foliar ABA as a signal for root growth has important implications for regulating root to shoot growth under normal conditions and suggests that leaf rather than root hydration is the main signal for regulating plant responses to moisture. © 2015 John Wiley & Sons Ltd.

Erythrocyte NADPH oxidase activity modulated by Rac GTPases, PKC, and plasma cytokines contributes to oxidative stress in sickle cell disease

PubMed Central

Pushkaran, Suvarnamala; Konstantinidis, Diamantis G.; Koochaki, Sebastian; Malik, Punam; Mohandas, Narla; Zheng, Yi; Joiner, Clinton H.; Kalfa, Theodosia A.

2013-01-01

Chronic inflammation has emerged as an important pathogenic mechanism in sickle cell disease (SCD). One component of this inflammatory response is oxidant stress mediated by reactive oxygen species (ROS) generated by leukocytes, endothelial cells, plasma enzymes, and sickle red blood cells (RBC). Sickle RBC ROS generation has been attributed to sickle hemoglobin auto-oxidation and Fenton chemistry reactions catalyzed by denatured heme moieties bound to the RBC membrane. In this study, we demonstrate that a significant part of ROS production in sickle cells is mediated enzymatically by NADPH oxidase, which is regulated by protein kinase C, Rac GTPase, and intracellular Ca2+ signaling within the sickle RBC. Moreover, plasma from patients with SCD and isolated cytokines, such as transforming growth factor β1 and endothelin-1, enhance RBC NADPH oxidase activity and increase ROS generation. ROS-mediated damage to RBC membrane components is known to contribute to erythrocyte rigidity and fragility in SCD. Erythrocyte ROS generation, hemolysis, vaso-occlusion, and the inflammatory response to tissue damage may therefore act in a positive-feedback loop to drive the pathophysiology of sickle cell disease. These findings suggest a novel pathogenic mechanism in SCD and may offer new therapeutic targets to counteract inflammation and RBC rigidity and fragility in SCD. PMID:23349388

Gibberellin–Abscisic Acid Balances during Arbuscular Mycorrhiza Formation in Tomato

PubMed Central

Martín-Rodríguez, José A.; Huertas, Raúl; Ho-Plágaro, Tania; Ocampo, Juan A.; Turečková, Veronika; Tarkowská, Danuše; Ludwig-Müller, Jutta; García-Garrido, José M.

2016-01-01

Plant hormones have become appropriate candidates for driving functional plant mycorrhization programs, including the processes that regulate the formation of arbuscules in arbuscular mycorrhizal (AM) symbiosis. Here, we examine the role played by ABA/GA interactions regulating the formation of AM in tomato. We report differences in ABA and GA metabolism between control and mycorrhizal roots. Active synthesis and catabolism of ABA occur in AM roots. GAs level increases as a consequence of a symbiosis-induced mechanism that requires functional arbuscules which in turn is dependent on a functional ABA pathway. A negative interaction in their metabolism has been demonstrated. ABA attenuates GA-biosynthetic and increases GA-catabolic gene expression leading to a reduction in bioactive GAs. Vice versa, GA activated ABA catabolism mainly in mycorrhizal roots. The negative impact of GA3 on arbuscule abundance in wild-type plants is partially offset by treatment with ABA and the application of a GA biosynthesis inhibitor rescued the arbuscule abundance in the ABA-deficient sitiens mutant. These findings, coupled with the evidence that ABA application leads to reduce bioactive GA1, support the hypothesis that ABA could act modifying bioactive GA level to regulate AM. Taken together, our results suggest that these hormones perform essential functions and antagonize each other by oppositely regulating AM formation in tomato roots. PMID:27602046

Expression of ABA Metabolism-Related Genes Suggests Similarities and Differences Between Seed Dormancy and Bud Dormancy of Peach (Prunus persica)

PubMed Central

Wang, Dongling; Gao, Zhenzhen; Du, Peiyong; Xiao, Wei; Tan, Qiuping; Chen, Xiude; Li, Ling; Gao, Dongsheng

2016-01-01

Dormancy inhibits seed and bud growth of perennial plants until the environmental conditions are optimal for survival. Previous studies indicated that certain co-regulation pathways exist in seed and bud dormancy. In our study, we found that seed and bud dormancy are similar to some extent but show different reactions to chemical treatments that induce breaking of dormancy. Whether the abscisic acid (ABA) regulatory networks are similar in dormant peach seeds and buds is not well known; however, ABA is generally believed to play a critical role in seed and bud dormancy. In peach, some genes putatively involved in ABA synthesis and catabolism were identified and their expression patterns were studied to learn more about ABA homeostasis and the possible crosstalk between bud dormancy and seed dormancy mechanisms. The analysis demonstrated that two 9-cis-epoxycarotenoid dioxygenase-encoding genes seem to be key in regulating ABA biosynthesis to induce seed and bud dormancy. Three CYP707As play an overlapping role in controlling ABA inactivation, resulting in dormancy-release. In addition, Transcript analysis of ABA metabolism-related genes was much similar demonstrated that ABA pathways was similar in the regulation of vegetative and flower bud dormancy, whereas, expression patterns of ABA metabolism-related genes were different in seed dormancy showed that ABA pathway maybe different in regulating seed dormancy in peach. PMID:26793222

Pathogen exploitation of an abscisic acid- and jasmonate-inducible MAPK phosphatase and its interception by Arabidopsis immunity.

PubMed

Mine, Akira; Berens, Matthias L; Nobori, Tatsuya; Anver, Shajahan; Fukumoto, Kaori; Winkelmüller, Thomas M; Takeda, Atsushi; Becker, Dieter; Tsuda, Kenichi

2017-07-11

Phytopathogens promote virulence by, for example, exploiting signaling pathways mediated by phytohormones such as abscisic acid (ABA) and jasmonate (JA). Some plants can counteract pathogen virulence by invoking a potent form of immunity called effector-triggered immunity (ETI). Here, we report that ABA and JA mediate inactivation of the immune-associated MAP kinases (MAPKs), MPK3 and MPK6, in Arabidopsis thaliana ABA induced expression of genes encoding the protein phosphatases 2C (PP2Cs), HAI1 , HAI2 , and HAI3 through ABF/AREB transcription factors. These three HAI PP2Cs interacted with MPK3 and MPK6 and were required for ABA-mediated MPK3/MPK6 inactivation and immune suppression. The bacterial pathogen Pseudomonas syringae pv. tomato ( Pto ) DC3000 activates ABA signaling and produces a JA-mimicking phytotoxin, coronatine (COR), that promotes virulence. We found that Pto DC3000 induces HAI1 through COR-mediated activation of MYC2, a master transcription factor in JA signaling. HAI1 dephosphorylated MPK3 and MPK6 in vitro and was necessary for COR-mediated suppression of MPK3/MPK6 activation and immunity. Intriguingly, upon ETI activation, A. thaliana plants overcame the HAI1-dependent virulence of COR by blocking JA signaling. Finally, we showed conservation of induction of HAI PP2Cs by ABA and JA in other Brassicaceae species. Taken together, these results suggest that ABA and JA signaling pathways, which are hijacked by the bacterial pathogen, converge on the HAI PP2Cs that suppress activation of the immune-associated MAPKs. Also, our data unveil interception of JA-signaling activation as a host counterstrategy against the bacterial suppression of MAPKs during ETI.

ABFs, a family of ABA-responsive element binding factors.

PubMed

Choi, H; Hong, J; Ha, J; Kang, J; Kim, S Y

2000-01-21

Abscisic acid (ABA) plays an important role in environmental stress responses of higher plants during vegetative growth. One of the ABA-mediated responses is the induced expression of a large number of genes, which is mediated by cis-regulatory elements known as abscisic acid-responsive elements (ABREs). Although a number of ABRE binding transcription factors have been known, they are not specifically from vegetative tissues under induced conditions. Considering the tissue specificity of ABA signaling pathways, factors mediating ABA-dependent stress responses during vegetative growth phase may thus have been unidentified so far. Here, we report a family of ABRE binding factors isolated from young Arabidopsis plants under stress conditions. The factors, isolated by a yeast one-hybrid system using a prototypical ABRE and named as ABFs (ABRE binding factors) belong to a distinct subfamily of bZIP proteins. Binding site selection assay performed with one ABF showed that its preferred binding site is the strong ABRE, CACGTGGC. ABFs can transactivate an ABRE-containing reporter gene in yeast. Expression of ABFs is induced by ABA and various stress treatments, whereas their induction patterns are different from one another. Thus, a new family of ABRE binding factors indeed exists that have the potential to activate a large number of ABA/stress-responsive genes in Arabidopsis.

Induction of apoptosis by plumbagin through reactive oxygen species-mediated inhibition of topoisomerase II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawiak, Anna; Piosik, Jacek; Stasilojc, Grzegorz

2007-09-15

Reactive oxygen species (ROS) have been recognized as key molecules, which can selectively modify proteins and therefore regulate cellular signalling including apoptosis. Plumbagin, a naphthoquinone exhibiting antitumor activity, is known to generate ROS and has been found to inhibit the activity of topoisomerase II (Topo II) through the stabilization of the Topo II-DNA cleavable complex. The objective of this research was to clarify the role of ROS and Topo II inhibition in the induction of apoptosis mediated by plumbagin. As determined by the comet assay, plumbagin induced DNA cleavage in HL-60 cells, whereas in a cell line with reduced Topomore » II activity-HL-60/MX2, the level of DNA damage was significantly decreased. The onset of DNA strand break formation in HL-60 cells was delayed in comparison with the generation of intracellular ROS. In HL-60/MX2 cells, ROS were generated at a similar rate, whereas a significant reduction in the level of DNA damage was detected. The pretreatment of cells with N-acetylcysteine (NAC) attenuated plumbagin-induced DNA damage, pointing out to the involvement of ROS generation in cleavable complex formation. These results suggest that plumbagin-induced ROS does not directly damage DNA but requires the involvement of Topo II. Furthermore, experiments carried out using light spectroscopy indicated no direct interactions between plumbagin and DNA. The induction of apoptosis was significantly delayed in HL-60/MX2 cells indicating the involvement of Topo II inhibition in plumbagin-mediated apoptosis. Thus, these findings strongly suggest ROS-mediated inhibition of Topo II as an important mechanism contributing to the apoptosis-inducing properties of plumbagin.« less

Drought coping strategies in cotton: increased crop per drop.

PubMed

Ullah, Abid; Sun, Heng; Yang, Xiyan; Zhang, Xianlong

2017-03-01

The growth and yield of many crops, including cotton, are affected by water deficit. Cotton has evolved drought specific as well as general morpho-physiological, biochemical and molecular responses to drought stress, which are discussed in this review. The key physiological responses against drought stress in cotton, including stomata closing, root development, cellular adaptations, photosynthesis, abscisic acid (ABA) and jasmonic acid (JA) production and reactive oxygen species (ROS) scavenging, have been identified by researchers. Drought stress induces the expression of stress-related transcription factors and genes, such as ROS scavenging, ABA or mitogen-activated protein kinases (MAPK) signalling genes, which activate various drought-related pathways to induce tolerance in the plant. It is crucial to elucidate and induce drought-tolerant traits via quantitative trait loci (QTL) analysis, transgenic approaches and exogenous application of substances. The current review article highlights the natural as well as engineered drought tolerance strategies in cotton. © 2017 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Antagonistic Basic Helix-Loop-Helix/bZIP Transcription Factors Form Transcriptional Modules That Integrate Light and Reactive Oxygen Species Signaling in Arabidopsis[W

PubMed Central

Chen, Dongqin; Xu, Gang; Tang, Weijiang; Jing, Yanjun; Ji, Qiang; Fei, Zhangjun; Lin, Rongcheng

2013-01-01

The critical developmental switch from heterotrophic to autotrophic growth of plants involves light signaling transduction and the production of reactive oxygen species (ROS). ROS function as signaling molecules that regulate multiple developmental processes, including cell death. However, the relationship between light and ROS signaling remains unclear. Here, we identify transcriptional modules composed of the basic helix-loop-helix and bZIP transcription factors PHYTOCHROME-INTERACTING FACTOR1 (PIF1), PIF3, ELONGATED HYPOCOTYL5 (HY5), and HY5 HOMOLOGY (HYH) that bridge light and ROS signaling to regulate cell death and photooxidative response. We show that pif mutants release more singlet oxygen and exhibit more extensive cell death than the wild type during Arabidopsis thaliana deetiolation. Genome-wide expression profiling indicates that PIF1 represses numerous ROS and stress-related genes. Molecular and biochemical analyses reveal that PIF1/PIF3 and HY5/HYH physically interact and coordinately regulate the expression of five ROS-responsive genes by directly binding to their promoters. Furthermore, PIF1/PIF3 and HY5/HYH function antagonistically during the seedling greening process. In addition, phytochromes, cryptochromes, and CONSTITUTIVE PHOTOMORPHOGENIC1 act upstream to regulate ROS signaling. Together, this study reveals that the PIF1/PIF3-HY5/HYH transcriptional modules mediate crosstalk between light and ROS signaling and sheds light on a new mechanism by which plants adapt to the light environments. PMID:23645630

A negative regulator encoded by a rice WRKY gene represses both abscisic acid and gibberellins signaling in aleurone cells.

PubMed

Zhang, Zhong-Lin; Shin, Margaret; Zou, Xiaolu; Huang, Jianzhi; Ho, Tun-hua David; Shen, Qingxi J

2009-05-01

Abscisic acid (ABA) and gibberellins (GAs) control several developmental processes including seed maturation, dormancy, and germination. The antagonism of these two hormones is well-documented. However, recent data from transcription profiling studies indicate that they can function as agonists in regulating the expression of many genes although the underlying mechanism is unclear. Here we report a rice WRKY gene, OsWRKY24, which encodes a protein that functions as a negative regulator of both GA and ABA signaling. Overexpression of OsWRKY24 via particle bombardment-mediated transient expression in aleurone cells represses the expression of two reporter constructs: the beta-glucuronidase gene driven by the GA-inducible Amy32b alpha-amylase promoter (Amy32b-GUS) and the ABA-inducible HVA22 promoter (HVA22-GUS). OsWRKY24 is unlikely a general repressor because it has little effect on the expression of the luciferase reporter gene driven by a constitutive ubiquitin promoter (UBI-Luciferase). As to the GA signaling, OsWRKY24 differs from OsWRKY51 and -71, two negative regulators specifically function in the GA signaling pathway, in several ways. First, OsWRKY24 contains two WRKY domains while OsWRKY51 and -71 have only one; both WRKY domains are essential for the full repressing activity of OsWRKY24. Second, binding of OsWRKY24 to the Amy32b promoter appears to involve sequences in addition to the TGAC cores of the W-boxes. Third, unlike OsWRKY71, OsWRKY24 is stable upon GA treatment. Together, these data demonstrate that OsWRKY24 is a novel type of transcriptional repressor that inhibits both GA and ABA signaling.

A myo-inositol-1-phosphate synthase gene, IbMIPS1, enhances salt and drought tolerance and stem nematode resistance in transgenic sweet potato.

PubMed

Zhai, Hong; Wang, Feibing; Si, Zengzhi; Huo, Jinxi; Xing, Lei; An, Yanyan; He, Shaozhen; Liu, Qingchang

2016-02-01

Myo-inositol-1-phosphate synthase (MIPS) is a key rate limiting enzyme in myo-inositol biosynthesis. The MIPS gene has been shown to improve tolerance to abiotic stresses in several plant species. However, its role in resistance to biotic stresses has not been reported. In this study, we found that expression of the sweet potato IbMIPS1 gene was induced by NaCl, polyethylene glycol (PEG), abscisic acid (ABA) and stem nematodes. Its overexpression significantly enhanced stem nematode resistance as well as salt and drought tolerance in transgenic sweet potato under field conditions. Transcriptome and real-time quantitative PCR analyses showed that overexpression of IbMIPS1 up-regulated the genes involved in inositol biosynthesis, phosphatidylinositol (PI) and ABA signalling pathways, stress responses, photosynthesis and ROS-scavenging system under salt, drought and stem nematode stresses. Inositol, inositol-1,4,5-trisphosphate (IP3 ), phosphatidic acid (PA), Ca(2+) , ABA, K(+) , proline and trehalose content was significantly increased, whereas malonaldehyde (MDA), Na(+) and H2 O2 content was significantly decreased in the transgenic plants under salt and drought stresses. After stem nematode infection, the significant increase of inositol, IP3 , PA, Ca(2+) , ABA, callose and lignin content and significant reduction of MDA content were found, and a rapid increase of H2 O2 levels was observed, peaked at 1 to 2 days and thereafter declined in the transgenic plants. This study indicates that the IbMIPS1 gene has the potential to be used to improve the resistance to biotic and abiotic stresses in plants. © 2015 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

SiASR4, the Target Gene of SiARDP from Setaria italica, Improves Abiotic Stress Adaption in Plants.

PubMed

Li, Jianrui; Dong, Yang; Li, Cong; Pan, Yanlin; Yu, Jingjuan

2016-01-01

Drought and other types of abiotic stresses negatively affect plant growth and crop yields. The abscisic acid-, stress-, and ripening-induced (ASR) proteins play important roles in the protection of plants against abiotic stress. However, the regulatory pathway of the gene encoding this protein remains to be elucidated. In this study, the foxtail millet ( Setaria italica ) ASR gene, SiASR4 , was cloned and characterized. SiASR4 localized to the cell nucleus, cytoplasm and cytomembrane, and the protein contained 102 amino acids, including an ABA/WDS (abscisic acid/water-deficit stress) domain, with a molecular mass of 11.5 kDa. The abundance of SiASR4 transcripts increased after treatment with ABA, NaCl, and PEG in foxtail millet seedlings. It has been reported that the S. italica ABA-responsive DRE-binding protein (SiARDP) binds to a DNA sequence with a CCGAC core and that there are five dehydration-responsive element (DRE) motifs within the SiASR4 promoter. Our analyses demonstrated that the SiARDP protein could bind to the SiASR4 promoter in vitro and in vivo . The expression of SiASR4 increased in SiARDP -overexpressing plants. SiASR4 -transgenic Arabidopsis and SiASR4 -overexpressing foxtail millet exhibited enhanced tolerance to drought and salt stress. Furthermore, the transcription of stress-responsive and reactive oxygen species (ROS) scavenger-associated genes was activated in SiASR4 transgenic plants. Together, these findings show that SiASR4 functions in the adaption to drought and salt stress and is regulated by SiARDP via an ABA-dependent pathway.

Arabidopsis ROP-interactive CRIB motif-containing protein 1 (RIC1) positively regulates auxin signalling and negatively regulates abscisic acid (ABA) signalling during root development.

PubMed

Choi, Yunjung; Lee, Yuree; Kim, Soo Young; Lee, Youngsook; Hwang, Jae-Ung

2013-05-01

Auxin and abscisic acid (ABA) modulate numerous aspects of plant development together, mostly in opposite directions, suggesting that extensive crosstalk occurs between the signalling pathways of the two hormones. However, little is known about the nature of this crosstalk. We demonstrate that ROP-interactive CRIB motif-containing protein 1 (RIC1) is involved in the interaction between auxin- and ABA-regulated root growth and lateral root formation. RIC1 expression is highly induced by both hormones, and expressed in the roots of young seedlings. Whereas auxin-responsive gene induction and the effect of auxin on root growth and lateral root formation were suppressed in the ric1 knockout, ABA-responsive gene induction and the effect of ABA on seed germination, root growth and lateral root formation were potentiated. Thus, RIC1 positively regulates auxin responses, but negatively regulates ABA responses. Together, our results suggest that RIC1 is a component of the intricate signalling network that underlies auxin and ABA crosstalk. © 2012 Blackwell Publishing Ltd.

Induction of specific micro RNA (miRNA) species by ROS-generating metal sulfates in primary human brain cells

PubMed Central

Lukiw, Walter J.; Pogue, Aileen I.

2007-01-01

Iron- and aluminum-sulfate together, at nanomolar concentrations, trigger the production of reactive oxygen species (ROS) in cultures of human brain cells. Previous studies have shown that following ROS induction, a family of pathogenic brain genes that promote inflammatory signalling, cellular apoptosis and brain cell death is significantly over-expressed. Notably, iron- and aluminum-sulfate induce genes in cultured human brain cells that exhibit expression patterns similar to those observed to be up-regulated in moderate- to late-stage Alzheimer's disease (AD). In this study we have extended our investigations to analyze the expression of micro RNA (miRNA) populations in iron- and aluminum-sulfate treated human neural cells in primary culture. The main finding was that these ROS-generating neurotoxic metal sulfates also up-regulate a specific set of miRNAs that includes miR-9, miR-125b and miR-128. Notably, these same miRNAs are up-regulated in AD brain. These findings further support the idea that iron- and aluminum-sulfates induce genotoxicity via a ROS-mediated up-regulation of specific regulatory elements and pathogenic genes that redirect brain cell fate towards progressive dysfunction and apoptotic cell death. PMID:17629564

Ecophysiological response to seasonal variations in water availability in the arborescent, endemic plant Vellozia gigantea.

PubMed

Morales, Melanie; Garcia, Queila S; Munné-Bosch, Sergi

2015-03-01

The physiological response of plants growing in their natural habitat is strongly determined by seasonal variations in environmental conditions and the interaction of abiotic and biotic stresses. Here, leaf water and nutrient contents, changes in cellular redox state and endogenous levels of stress-related phytohormones (abscisic acid (ABA), salicylic acid and jasmonates) were examined during the rainy and dry season in Vellozia gigantea, an endemic species growing at high elevations in the rupestrian fields of the Espinhaço Range in Brazil. Enhanced stomatal closure and increased ABA levels during the dry season were associated with an efficient control of leaf water content. Moreover, reductions in 12-oxo-phytodienoic acid (OPDA) levels during the dry season were observed, while levels of other jasmonates, such as jasmonic acid and jasmonoyl-isoleucine, were not affected. Changes in ABA and OPDA levels correlated with endogenous concentrations of iron and silicon, hydrogen peroxide, and vitamin E, thus indicating complex interactions between water and nutrient contents, changes in cellular redox state and endogenous hormone concentrations. Results also suggested crosstalk between activation of mechanisms for drought stress tolerance (as mediated by ABA) and biotic stress resistance (mediated by jasmonates), in which vitamin E levels may serve as a control point. It is concluded that, aside from a tight ABA-associated regulation of stomatal closure during the dry season, crosstalk between activation of abiotic and biotic defences, and nutrient accumulation in leaves may be important modulators of plant stress responses in plants growing in their natural habitat. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Function of ABA in Stomatal Defense against Biotic and Drought Stresses

PubMed Central

Lim, Chae Woo; Baek, Woonhee; Jung, Jangho; Kim, Jung-Hyun; Lee, Sung Chul

2015-01-01

The plant hormone abscisic acid (ABA) regulates many key processes involved in plant development and adaptation to biotic and abiotic stresses. Under stress conditions, plants synthesize ABA in various organs and initiate defense mechanisms, such as the regulation of stomatal aperture and expression of defense-related genes conferring resistance to environmental stresses. The regulation of stomatal opening and closure is important to pathogen defense and control of transpirational water loss. Recent studies using a combination of approaches, including genetics, physiology, and molecular biology, have contributed considerably to our understanding of ABA signal transduction. A number of proteins associated with ABA signaling and responses—especially ABA receptors—have been identified. ABA signal transduction initiates signal perception by ABA receptors and transfer via downstream proteins, including protein kinases and phosphatases. In the present review, we focus on the function of ABA in stomatal defense against biotic and abiotic stresses, through analysis of each ABA signal component and the relationships of these components in the complex network of interactions. In particular, two ABA signal pathway models in response to biotic and abiotic stress were proposed, from stress signaling to stomatal closure, involving the pyrabactin resistance (PYR)/PYR-like (PYL) or regulatory component of ABA receptor (RCAR) family proteins, 2C-type protein phosphatases, and SnRK2-type protein kinases. PMID:26154766

Regulation of carotenoid and ABA accumulation during the development and germination of Nicotiana plumbaginifolia seeds.

PubMed

Frey, Anne; Boutin, Jean-Pierre; Sotta, Bruno; Mercier, Raphaël; Marion-Poll, Annie

2006-08-01

Abscisic acid (ABA) is derived from epoxycarotenoid cleavage and regulates seed development and maturation. A detailed carotenoid analysis was undertaken to study the contribution of epoxycarotenoid synthesis to the regulation of ABA accumulation in Nicotiana plumbaginifolia developing seeds. Maximal accumulation of xanthophylls occurred at mid-development in wild type seeds, when total ABA levels also peaked. In contrast, in ABA-deficient mutants xanthophyll synthesis was delayed, in agreement with the retardation in seed maturation. Seed dormancy was restored in mutants impaired in the conversion of zeaxanthin into violaxanthin by zeaxanthin epoxidase (ZEP), by the introduction of the Arabidopsis AtZEP gene under the control of promoters inducing expression during later stages of seed development compared to wild type NpZEP, and in dry and imbibed seeds. Alterations in the timing and level of ZEP expression did not highly affect the temporal regulation of ABA accumulation in transgenic seeds, despite notable perturbations in xanthophyll accumulation. Therefore, major regulatory control of ABA accumulation might occur downstream of epoxycarotenoid synthesis.

Rapid Quantification of Abscisic Acid by GC-MS/MS for Studies of Abiotic Stress Response.

PubMed

Verslues, Paul E

2017-01-01

Drought and low water potential induce large increases in Abscisic Acid (ABA ) content of plant tissue. This increased ABA content is essential to regulate downstream stress resistance responses; however, the mechanisms regulating ABA accumulation are incompletely known. Thus, the ability to accurately quantify ABA at high throughput and low cost is important for plant stress research. We have combined and modified several previously published protocols to establish a rapid ABA analysis protocol using gas chromatography-tandem mass spectrometry (GC-MS/MS). Derivatization of ABA is performed with (trimethylsilyl)-diazomethane rather than the harder to prepare diazomethane. Sensitivity of the analysis is sufficient that small samples of low water potential treated Arabidopsis thaliana seedlings can be routinely analyzed in reverse genetic studies of putative stress regulators as well as studies of natural variation in ABA accumulation.

Isoprene emission protects photosynthesis but reduces plant productivity during drought in transgenic tobacco (Nicotiana tabacum) plants.

PubMed

Ryan, Annette C; Hewitt, C Nicholas; Possell, Malcolm; Vickers, Claudia E; Purnell, Anna; Mullineaux, Philip M; Davies, William J; Dodd, Ian C

2014-01-01

Isoprene protects the photosynthetic apparatus of isoprene-emitting plants from oxidative stress. The role of isoprene in the response of plants to drought is less clear. Water was withheld from transgenic isoprene-emitting and non-emitting tobacco (Nicotiana tabacum) plants, to examine: the response of isoprene emission to plant water deficit; a possible relationship between concentrations of the drought-induced phytohormone abscisic acid (ABA) and isoprene; and whether isoprene affected foliar reactive oxygen species (ROS) and lipid peroxidation levels. Isoprene emission did not affect whole-plant water use, foliar ABA concentration or leaf water potential under water deficit. Compared with well-watered controls, droughted non-emitting plants significantly increased ROS content (31-46%) and lipid peroxidation (30-47%), concomitant with decreased operating and maximum efficiencies of photosystem II photochemistry and lower leaf and whole-plant water use efficiency (WUE). Droughted isoprene-emitting plants showed no increase in ROS content or lipid peroxidation relative to well-watered controls, despite isoprene emission decreasing before leaf wilting. Although isoprene emission protected the photosynthetic apparatus and enhanced leaf and whole-plant WUE, non-emitting plants had 8-24% more biomass under drought, implying that isoprene emission incurred a yield penalty. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

STAT5A-mediated NOX5-L expression promotes the proliferation and metastasis of breast cancer cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dho, So Hee; Radioisotope Research Division, Department of Research Reactor Utilization, Korea Atomic Energy Research Institute, Daejeon 305-353; Kim, Ji Young

NADPH oxidase (NOX) generates reactive oxygen species (ROS) and has been suggested to mediate cell proliferation in some cancers. Here, we show that an increase in the expression of NOX5 long form (NOX5-L) is critical for tumor progression in breast tumor tissues. Immunostaining of clinical samples indicated that NOX5 was overexpressed in 41.1% of breast ductal carcinoma samples. NOX5-L depletion consistently suppressed cell proliferation, invasion, and migration in vitro. Antibody-mediated neutralization of NOX5-L attenuated tumor progression in a mouse xenograft model. Promoter analysis revealed that NOX5-L expression is regulated by STAT5A in breast cancer cells. Based on our novel findings,more » we suggest that inhibition of NOX5-L may be a promising therapeutic strategy that exerts anti-cancer effects via the modulation of ROS-mediated cell signaling. - Highlights: • The ROS-generating protein, NOX5-L, determines cellular proliferation and metastasis in subset of breast tumor. • Tumor growth was attenuated by the treatment of anti-NOX5-L antibody in a xenograft model. • NOX5-L expression is transcriptionally regulated by STAT5A in breast cancer cells.« less

Reactive oxygen species upregulate expression of muscle atrophy-associated ubiquitin ligase Cbl-b in rat L6 skeletal muscle cells.

PubMed

Uchida, Takayuki; Sakashita, Yoshihiro; Kitahata, Kanako; Yamashita, Yui; Tomida, Chisato; Kimori, Yuki; Komatsu, Akio; Hirasaka, Katsuya; Ohno, Ayako; Nakao, Reiko; Higashitani, Atsushi; Higashibata, Akira; Ishioka, Noriaki; Shimazu, Toru; Kobayashi, Takeshi; Okumura, Yuushi; Choi, Inho; Oarada, Motoko; Mills, Edward M; Teshima-Kondo, Shigetada; Takeda, Shin'ichi; Tanaka, Eiji; Tanaka, Keiji; Sokabe, Masahiro; Nikawa, Takeshi

2018-06-01

Unloading-mediated muscle atrophy is associated with increased reactive oxygen species (ROS) production. We previously demonstrated that elevated ubiquitin ligase casitas B-lineage lymphoma-b (Cbl-b) resulted in the loss of muscle volume (Nakao R, Hirasaka K, Goto J, Ishidoh K, Yamada C, Ohno A, Okumura Y, Nonaka I, Yasutomo K, Baldwin KM, Kominami E, Higashibata A, Nagano K, Tanaka K, Yasui N, Mills EM, Takeda S, Nikawa T. Mol Cell Biol 29: 4798-4811, 2009). However, the pathological role of ROS production associated with unloading-mediated muscle atrophy still remains unknown. Here, we showed that the ROS-mediated signal transduction caused by microgravity or its simulation contributes to Cbl-b expression. In L6 myotubes, the assessment of redox status revealed that oxidized glutathione was increased under microgravity conditions, and simulated microgravity caused a burst of ROS, implicating ROS as a critical upstream mediator linking to downstream atrophic signaling. ROS generation activated the ERK1/2 early-growth response protein (Egr)1/2-Cbl-b signaling pathway, an established contributing pathway to muscle volume loss. Interestingly, antioxidant treatments such as N-acetylcysteine and TEMPOL, but not catalase, blocked the clinorotation-mediated activation of ERK1/2. The increased ROS induced transcriptional activity of Egr1 and/or Egr2 to stimulate Cbl-b expression through the ERK1/2 pathway in L6 myoblasts, since treatment with Egr1/2 siRNA and an ERK1/2 inhibitor significantly suppressed clinorotation-induced Cbl-b and Egr expression, respectively. Promoter and gel mobility shift assays revealed that Cbl-b was upregulated via an Egr consensus oxidative responsive element at -110 to -60 bp of the Cbl-b promoter. Together, this indicates that under microgravity conditions, elevated ROS may be a crucial mechanotransducer in skeletal muscle cells, regulating muscle mass through Cbl-b expression activated by the ERK-Egr signaling pathway.

The redox-sensing gene Nrf2 affects intestinal homeostasis, insecticide resistance, and Zika virus susceptibility in the mosquito Aedes aegypti.

PubMed

Bottino-Rojas, Vanessa; Talyuli, Octavio A C; Carrara, Luana; Martins, Ademir J; James, Anthony A; Oliveira, Pedro L; Paiva-Silva, Gabriela O

2018-06-08

Production and degradation of reactive oxygen species (ROS) are extensively regulated to ensure proper cellular responses to various environmental stimuli and stresses. Moreover, physiologically generated ROS function as secondary messengers that can influence tissue homeostasis. The cap'n'collar transcription factor known as nuclear factor erythroid-derived factor 2 (Nrf2) coordinates an evolutionarily conserved transcriptional activation pathway that mediates antioxidant and detoxification responses in many animal species, including insects and mammals. Here, we show that Nrf2-mediated signaling affects embryo survival, midgut homeostasis, and redox biology in Aedes aegypti , a mosquito species vector of dengue, Zika, and other disease-causing viruses. We observed that AeNrf2 silencing increases ROS levels and stimulates intestinal stem cell proliferation. Because ROS production is a major aspect of innate immunity in mosquito gut, we found that a decrease in Nrf2 signaling results in reduced microbiota growth and Zika virus infection. Moreover, we provide evidence that AeNrf2 signaling also controls transcriptional adaptation of A. aegypti to insecticide challenge. Therefore, we conclude that Nrf2-mediated response regulates assorted gene clusters in A. aegypti that determine cellular and midgut redox balance, affecting overall xenobiotic resistance and vectorial adaptation of the mosquito. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Synthetic polymeric substrates as potent pro-oxidant versus anti-oxidant regulators of cytoskeletal remodeling and cell apoptosis.

PubMed

Sung, Hak-Joon; Chandra, Prafulla; Treiser, Matthew D; Liu, Er; Iovine, Carmine P; Moghe, Prabhas V; Kohn, Joachim

2009-03-01

The role of reactive oxygen species (ROS)-mediated cell signal transduction pathways emanating from engineered cell substrates remains unclear. To elucidate the role, polymers derived from the amino acid L-tyrosine were used as synthetic matrix substrates. Variations in their chemical properties were created by co-polymerizing hydrophobic L-tyrosine derivatives with uncharged hydrophilic poly(ethylene glycol) (PEG, Mw = 1,000 Da), and negatively charged desaminotyrosyl-tyrosine (DT). These substrates were characterized for their intrinsic ability to generate ROS, as well as their ability to elicit Saos-2 cell responses in terms of intracellular ROS production, actin remodeling, and apoptosis. PEG-containing substrates induced both exogenous and intracellular ROS production, whereas the charged substrates reduced production of both types, indicating a coupling of exogenous ROS generation and intracellular ROS production. Furthermore, PEG-mediated ROS induction caused nuclear translocation of glyceraldehyde-3-phosphate dehydrogenase and an increase in caspase-3 activity, confirming a link with apoptosis. PEG-rich pro-oxidant substrates caused cytoskeletal actin remodeling through beta-actin cleavage by caspase-3 into fractins. The fractins co-localized to the mitochondria and reduced the mitochondrial membrane potential. The remnant cytosolic beta-actin was polymerized and condensed, events consistent with apoptotic cell shrinkage. The cytoskeletal remodeling was integral to the further augmentation of intracellular ROS production. Conversely, the anti-oxidant DT-containing charged substrates suppressed the entire cascade of apoptotic progression. We demonstrate that ROS activity serves an important role in "outside-in" signaling for cells grown on substrates: the ROS activity couples exogenous stress, driven by substrate composition, to changes in intracellular signaling. This signaling causes cell apoptosis, which is mediated by actin remodeling.

Damage-induced reactive oxygen species regulate vimentin and dynamic collagen-based projections to mediate wound repair

PubMed Central

Freisinger, Chrissy; Rindy, Julie; Golenberg, Netta; Frecentese, Grace; Gibson, Angela; Eliceiri, Kevin W

2018-01-01

Tissue injury leads to early wound-associated reactive oxygen species (ROS) production that mediate tissue regeneration. To identify mechanisms that function downstream of redox signals that modulate regeneration, a vimentin reporter of mesenchymal cells was generated by driving GFP from the vimentin promoter in zebrafish. Early redox signaling mediated vimentin reporter activity at the wound margin. Moreover, both ROS and vimentin were necessary for collagen production and reorganization into projections at the leading edge of the wound. Second harmonic generation time-lapse imaging revealed that the collagen projections were associated with dynamic epithelial extensions at the wound edge during wound repair. Perturbing collagen organization by burn wound disrupted epithelial projections and subsequent wound healing. Taken together our findings suggest that ROS and vimentin integrate early wound signals to orchestrate the formation of collagen-based projections that guide regenerative growth during efficient wound repair. PMID:29336778

Identification of a cis-regulatory region of a gene in Arabidopsis thaliana whose induction by dehydration is mediated by abscisic acid and requires protein synthesis.

PubMed

Iwasaki, T; Yamaguchi-Shinozaki, K; Shinozaki, K

1995-05-20

In Arabidopsis thaliana, the induction of a dehydration-responsive gene, rd22, is mediated by abscisic acid (ABA) but the gene does not include any sequence corresponding to the consensus ABA-responsive element (ABRE), RYACGTGGYR, in its promoter region. The cis-regulatory region of the rd22 promoter was identified by monitoring the expression of beta-glucuronidase (GUS) activity in leaves of transgenic tobacco plants transformed with chimeric gene fusions constructed between 5'-deleted promoters of rd22 and the coding region of the GUS reporter gene. A 67-bp nucleotide fragment corresponding to positions -207 to -141 of the rd22 promoter conferred responsiveness to dehydration and ABA on a non-responsive promoter. The 67-bp fragment contains the sequences of the recognition sites for some transcription factors, such as MYC, MYB, and GT-1. The fact that accumulation of rd22 mRNA requires protein synthesis raises the possibility that the expression of rd22 might be regulated by one of these trans-acting protein factors whose de novo synthesis is induced by dehydration or ABA. Although the structure of the RD22 protein is very similar to that of a non-storage seed protein, USP, of Vicia faba, the expression of the GUS gene driven by the rd22 promoter in non-stressed transgenic Arabidopsis plants was found mainly in flowers and bolted stems rather than in seeds.

Function of reactive oxygen species during animal development: passive or active?

PubMed

Covarrubias, Luis; Hernández-García, David; Schnabel, Denhí; Salas-Vidal, Enrique; Castro-Obregón, Susana

2008-08-01

Oxidative stress is considered causal of aging and pathological cell death, however, very little is known about its function in the natural processes that support the formation of an organism. It is generally thought that cells must continuously protect themselves from the possible damage caused by reactive oxygen species (ROS) (passive ROS function). However, presently, ROS are recognized as physiologically relevant molecules that mediate cell responses to a variety of stimuli, and the activities of several molecules, some developmentally relevant, are directly or indirectly regulated by oxidative stress (active ROS function). Here we review recent data that are suggestive of specific ROS functions during development of animals, particularly mammals.

P-HYDROXYPHENYLPYRUVATE DIOXYGENASE from Medicago sativa is involved in vitamin E biosynthesis and abscisic acid-mediated seed germination

PubMed Central

Jiang, Jishan; Chen, Zhihong; Ban, Liping; Wu, Yudi; Huang, Jianping; Chu, Jinfang; Fang, Shuang; Wang, Zan; Gao, Hongwen; Wang, Xuemin

2017-01-01

P-HYDROXYPHENYLPYRUVATE DIOXYGENASE (HPPD) is the first committed enzyme involved in the biosynthesis of vitamin E, and is characterized by catalyzing the conversion of p-hydroxyphenyl pyruvate (HPP) to homogentisic acid (HGA). Here, an HPPD gene was cloned from Medicago sativa L. and designated MsHPPD, which was expressed at high levels in alfalfa leaves. PEG 6000 (polyethylene glycol), NaCl, abscisic acid and salicylic acid were shown to significantly induce MsHPPD expression, especially in the cotyledons and root tissues. Overexpression of MsHPPD was found to significantly increase the level of β-tocotrienol and the total vitamin E content in Arabidopsis seeds. Furthermore, these transgenic Arabidopsis seeds exhibited an accelerated germination time, compared with wild-type seeds under normal conditions, as well as under NaCl and ABA treatments. Meanwhile, the expression level of several genes associated with ABA biosynthesis (NCED3, NCED5 and NCED9) and the ABA signaling pathway (RAB18, ABI3 and ABI5) were significantly down-regulated in MsHPPD-overexpressing transgenic lines, as well as the total free ABA content. Taken together, these results demonstrate that MsHPPD functions not only in the vitamin E biosynthetic pathway, but also plays a critical role in seed germination via affecting ABA biosynthesis and signaling. PMID:28084442

Abscisic acid accumulation modulates auxin transport in the root tip to enhance proton secretion for maintaining root growth under moderate water stress.

PubMed

Xu, Weifeng; Jia, Liguo; Shi, Weiming; Liang, Jiansheng; Zhou, Feng; Li, Qianfeng; Zhang, Jianhua

2013-01-01

Maintenance of root growth is essential for plant adaptation to soil drying. Here, we tested the hypothesis that auxin transport is involved in mediating ABA's modulation by activating proton secretion in the root tip to maintain root growth under moderate water stress. Rice and Arabidopsis plants were raised under a hydroponic system and subjected to moderate water stress (-0.47 MPa) with polyethylene glycol (PEG). ABA accumulation, auxin transport and plasma membrane H(+)-ATPase activity at the root tip were monitored in addition to the primary root elongation and root hair density. We found that moderate water stress increases ABA accumulation and auxin transport in the root apex. Additionally, ABA modulation is involved in the regulation of auxin transport in the root tip. The transported auxin activates the plasma membrane H(+)-ATPase to release more protons along the root tip in its adaption to moderate water stress. The proton secretion in the root tip is essential in maintaining or promoting primary root elongation and root hair development under moderate water stress. These results suggest that ABA accumulation modulates auxin transport in the root tip, which enhances proton secretion for maintaining root growth under moderate water stress. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

Gladiolus hybridus ABSCISIC ACID INSENSITIVE 5 (GhABI5) is an important transcription factor in ABA signaling that can enhance Gladiolus corm dormancy and Arabidopsis seed dormancy.

PubMed

Wu, Jian; Seng, Shanshan; Sui, Juanjuan; Vonapartis, Eliana; Luo, Xian; Gong, Benhe; Liu, Chen; Wu, Chenyu; Liu, Chao; Zhang, Fengqin; He, Junna; Yi, Mingfang

2015-01-01

The phytohormone abscisic acid (ABA) regulates plant development and is crucial for abiotic stress response. In this study, cold storage contributes to reducing endogenous ABA content, resulting in dormancy breaking of Gladiolus. The ABA inhibitor fluridone also promotes germination, suggesting that ABA is an important hormone that regulates corm dormancy. Here, we report the identification and functional characterization of the Gladiolus ABI5 homolog (GhABI5), which is a basic leucine zipper motif transcriptional factor (TF). GhABI5 is expressed in dormant vegetative organs (corm, cormel, and stolon) as well as in reproductive organs (stamen), and it is up-regulated by ABA or drought. Complementation analysis reveals that GhABI5 rescues the ABA insensitivity of abi5-3 during seed germination and induces the expression of downstream ABA response genes in Arabidopsis thaliana (EM1, EM6, and RD29B). Down-regulation of GhABI5 in dormant cormels via virus induced gene silence promotes sprouting and reduces the expression of downstream genes (GhLEA and GhRD29B). The results of this study reveal that GhABI5 regulates bud dormancy (vegetative organ) in Gladiolus in addition to its well-studied function in Arabidopsis seeds (reproductive organ).

The Putative E3 Ubiquitin Ligase ECERIFERUM9 Regulates Abscisic Acid Biosynthesis and Response during Seed Germination and Postgermination Growth in Arabidopsis1[W][OPEN

PubMed Central

Zhao, Huayan; Zhang, Huoming; Cui, Peng; Ding, Feng; Wang, Guangchao; Li, Rongjun; Jenks, Matthew A.; Lü, Shiyou; Xiong, Liming

2014-01-01

The ECERIFERUM9 (CER9) gene encodes a putative E3 ubiquitin ligase that functions in cuticle biosynthesis and the maintenance of plant water status. Here, we found that CER9 is also involved in abscisic acid (ABA) signaling in seeds and young seedlings of Arabidopsis (Arabidopsis thaliana). The germinated embryos of the mutants exhibited enhanced sensitivity to ABA during the transition from reversible dormancy to determinate seedling growth. Expression of the CER9 gene is closely related to ABA levels and displays a similar pattern to that of ABSCISIC ACID-INSENSITIVE5 (ABI5), which encodes a positive regulator of ABA responses in seeds. cer9 mutant seeds exhibited delayed germination that is independent of seed coat permeability. Quantitative proteomic analyses showed that cer9 seeds had a protein profile similar to that of the wild type treated with ABA. Transcriptomics analyses revealed that genes involved in ABA biosynthesis or signaling pathways were differentially regulated in cer9 seeds. Consistent with this, high levels of ABA were detected in dry seeds of cer9. Blocking ABA biosynthesis by fluridone treatment or by combining an ABA-deficient mutation with cer9 attenuated the phenotypes of cer9. Whereas introduction of the abi1-1, abi3-1, or abi4-103 mutation could completely eliminate the ABA hypersensitivity of cer9, introduction of abi5 resulted only in partial suppression. These results indicate that CER9 is a novel negative regulator of ABA biosynthesis and the ABA signaling pathway during seed germination. PMID:24812105

Variable responses of small and large human hepatocytes to hypoxia and hypoxia/reoxygenation (H–R)

PubMed Central

Bhogal, Ricky H.; Weston, Christopher J.; Curbishley, Stuart M.; Bhatt, Anand N.; Adams, David H.; Afford, Simon C.

2011-01-01

Hypoxia and hypoxia–reoxygenation (H–R) regulate human hepatocyte cell death by mediating the accumulation of reactive oxygen species (ROS). Hepatocytes within the liver are organised into peri-portal (PP) and peri-venous (PV) subpopulations. PP and PV hepatocytes differ in size and function. We investigated whether PP and PV human hepatocytes exhibit differential susceptibility to hypoxic stress. Isolated hepatocytes were used in an in vitro model of hypoxia and H–R. ROS production and cell death were assessed using flow cytometry. PV, and not PP hepatocytes, accumulate intracellular ROS in a mitochondrial dependent manner during hypoxia and H–R. This increased ROS regulates hepatocyte apoptosis and necrosis via a mitochondrial pathway. These findings have implications on the understanding of liver injury and application of potential therapeutic strategies. PMID:21356211

ROS mediated EGFR/MEK/ERK/HIF-1α Loop Regulates Glucose metabolism in pancreatic cancer.

PubMed

Wang, Gang; Li, Yifeng; Yang, Zeyu; Xu, Weina; Yang, Yifan; Tan, Xiaodong

2018-06-12

To investigate the glycometabolism associated mechanism in invasion and metastasis of pancreatic cancer, We screened out genes involved in anaerobic glycolysis headed by HIF-1α,using pre-established a pair of pancreatic cancer cell lines. In this study, we further detected the glucose metabolism state not only in the cells but all also in two groups of patients with different SUVmax on 18 F-FDG PET/CT. The data suggests that ROS mediated EGFR/MEK/ERK/HIF-1α loop is activated in high glucose metabolic samples both in vitro and in vivo: The increasing of HIF-1α expression is controlled by activation of EGFR/MEK/ERK pathway in hypoxia condition, HIF-1α inhibits excessive release of ROS, the reduction of ROS further activates EGFR to form a positive feedback loop. This difference is closely related to invasion and metastasis capacity of pancreatic cancer, and can be rescued by separate or combined inhibition of EGFR or HIF-1α in various degree. These results indicate a new clue to develop therapy of pancreatic cancer by regulating the glucose metabolism. Copyright © 2018 Elsevier Inc. All rights reserved.

The targeted delivery of the c-Src peptide complexed with schizophyllan to macrophages inhibits polymicrobial sepsis and ulcerative colitis in mice.

PubMed

Kim, Ye-Ram; Hwang, Jangsun; Koh, Hyun-Jung; Jang, Kiseok; Lee, Jong-Dae; Choi, Jonghoon; Yang, Chul-Su

2016-05-01

Hyper-inflammatory responses triggered by intracellular reactive oxygen species (ROS) can lead to a variety of diseases, including sepsis and colitis. However, the regulators of this process remain poorly defined. In this study, we demonstrate that c-Src is a negative regulator of cellular ROS generation through its binding to p47phox. This molecule also competitively inhibits the NADPH oxidase complex (NOX) assembly. Furthermore, we developed the schizophyllan (SPG)-c-Src SH3 peptide, which is a β-1,3-glucan conjugated c-Src SH3-derived peptide composed of amino acids 91-108 and 121-140 of c-Src. The SPG-SH3 peptide has a significant therapeutic effect on mouse ROS-mediated inflammatory disease models, cecal-ligation-puncture-induced sepsis, and dextran sodium sulfate-induced colitis. It does so by inhibiting the NOX subunit assembly and proinflammatory mediator production. Therefore, the SPG-SH3 peptide is a potential therapeutic agent for ROS-associated lethal inflammatory diseases. Our findings provide clues for the development of new peptide-base drugs that will target p47phox. Copyright © 2016 Elsevier Ltd. All rights reserved.

Rice ABI5-Like1 Regulates Abscisic Acid and Auxin Responses by Affecting the Expression of ABRE-Containing Genes1[W][OA

PubMed Central

Yang, Xi; Yang, Ya-Nan; Xue, Liang-Jiao; Zou, Mei-Juan; Liu, Jian-Ying; Chen, Fan; Xue, Hong-Wei

2011-01-01

Abscisic acid (ABA) regulates plant development and is crucial for plant responses to biotic and abiotic stresses. Studies have identified the key components of ABA signaling in Arabidopsis (Arabidopsis thaliana), some of which regulate ABA responses by the transcriptional regulation of downstream genes. Here, we report the functional identification of rice (Oryza sativa) ABI5-Like1 (ABL1), which is a basic region/leucine zipper motif transcription factor. ABL1 is expressed in various tissues and is induced by the hormones ABA and indole-3-acetic acid and stress conditions including salinity, drought, and osmotic pressure. The ABL1 deficiency mutant, abl1, shows suppressed ABA responses, and ABL1 expression in the Arabidopsis abi5 mutant rescued the ABA sensitivity. The ABL1 protein is localized to the nucleus and can directly bind ABA-responsive elements (ABREs; G-box) in vitro. A gene expression analysis by DNA chip hybridization confirms that a large proportion of down-regulated genes of abl1 are involved in stress responses, consistent with the transcriptional activating effects of ABL1. Further studies indicate that ABL1 regulates the plant stress responses by regulating a series of ABRE-containing WRKY family genes. In addition, the abl1 mutant is hypersensitive to exogenous indole-3-acetic acid, and some ABRE-containing genes related to auxin metabolism or signaling are altered under ABL1 deficiency, suggesting that ABL1 modulates ABA and auxin responses by directly regulating the ABRE-containing genes. PMID:21546455

Evolutionarily Conserved Regulatory Mechanisms of Abscisic Acid Signaling in Land Plants: Characterization of ABSCISIC ACID INSENSITIVE1-Like Type 2C Protein Phosphatase in the Liverwort Marchantia polymorpha1[C][OA

PubMed Central

Tougane, Ken; Komatsu, Kenji; Bhyan, Salma Begum; Sakata, Yoichi; Ishizaki, Kimitsune; Yamato, Katsuyuki T.; Kohchi, Takayuki; Takezawa, Daisuke

2010-01-01

Abscisic acid (ABA) is postulated to be a ubiquitous hormone that plays a central role in seed development and responses to environmental stresses of vascular plants. However, in liverworts (Marchantiophyta), which represent the oldest extant lineage of land plants, the role of ABA has been least emphasized; thus, very little information is available on the molecular mechanisms underlying ABA responses. In this study, we isolated and characterized MpABI1, an ortholog of ABSCISIC ACID INSENSITIVE1 (ABI1), from the liverwort Marchantia polymorpha. The MpABI1 cDNA encoded a 568-amino acid protein consisting of the carboxy-terminal protein phosphatase 2C (PP2C) domain and a novel amino-terminal regulatory domain. The MpABI1 transcript was detected in the gametophyte, and its expression level was increased by exogenous ABA treatment in the gemma, whose growth was strongly inhibited by ABA. Experiments using green fluorescent protein fusion constructs indicated that MpABI1 was mainly localized in the nucleus and that its nuclear localization was directed by the amino-terminal domain. Transient overexpression of MpABI1 in M. polymorpha and Physcomitrella patens cells resulted in suppression of ABA-induced expression of the wheat Em promoter fused to the β -glucuronidase gene. Transgenic P. patens expressing MpABI1 and its mutant construct, MpABI1-d2, lacking the amino-terminal domain, had reduced freezing and osmotic stress tolerance, and associated with reduced accumulation of ABA-induced late embryogenesis abundant-like boiling-soluble proteins. Furthermore, ABA-induced morphological changes leading to brood cells were not prominent in these transgenic plants. These results suggest that MpABI1 is a negative regulator of ABA signaling, providing unequivocal molecular evidence of PP2C-mediated ABA response mechanisms functioning in liverworts. PMID:20097789

Evolutionarily conserved regulatory mechanisms of abscisic acid signaling in land plants: characterization of ABSCISIC ACID INSENSITIVE1-like type 2C protein phosphatase in the liverwort Marchantia polymorpha.

PubMed

Tougane, Ken; Komatsu, Kenji; Bhyan, Salma Begum; Sakata, Yoichi; Ishizaki, Kimitsune; Yamato, Katsuyuki T; Kohchi, Takayuki; Takezawa, Daisuke

2010-03-01

Abscisic acid (ABA) is postulated to be a ubiquitous hormone that plays a central role in seed development and responses to environmental stresses of vascular plants. However, in liverworts (Marchantiophyta), which represent the oldest extant lineage of land plants, the role of ABA has been least emphasized; thus, very little information is available on the molecular mechanisms underlying ABA responses. In this study, we isolated and characterized MpABI1, an ortholog of ABSCISIC ACID INSENSITIVE1 (ABI1), from the liverwort Marchantia polymorpha. The MpABI1 cDNA encoded a 568-amino acid protein consisting of the carboxy-terminal protein phosphatase 2C (PP2C) domain and a novel amino-terminal regulatory domain. The MpABI1 transcript was detected in the gametophyte, and its expression level was increased by exogenous ABA treatment in the gemma, whose growth was strongly inhibited by ABA. Experiments using green fluorescent protein fusion constructs indicated that MpABI1 was mainly localized in the nucleus and that its nuclear localization was directed by the amino-terminal domain. Transient overexpression of MpABI1 in M. polymorpha and Physcomitrella patens cells resulted in suppression of ABA-induced expression of the wheat Em promoter fused to the beta -glucuronidase gene. Transgenic P. patens expressing MpABI1 and its mutant construct, MpABI1-d2, lacking the amino-terminal domain, had reduced freezing and osmotic stress tolerance, and associated with reduced accumulation of ABA-induced late embryogenesis abundant-like boiling-soluble proteins. Furthermore, ABA-induced morphological changes leading to brood cells were not prominent in these transgenic plants. These results suggest that MpABI1 is a negative regulator of ABA signaling, providing unequivocal molecular evidence of PP2C-mediated ABA response mechanisms functioning in liverworts.

Role of plant growth regulators as chemical signals in plant-microbe interactions: a double edged sword.

PubMed

Spence, Carla; Bais, Harsh

2015-10-01

Growth regulators act not only as chemicals that modulate plant growth but they also act as signal molecules under various biotic and abiotic stresses. Of all growth regulators, abscisic acid (ABA) is long known for its role in modulating plants response against both biotic and abiotic stress. Although the genetic information for ABA biosynthesis in plants is well documented, the knowledge about ABA biosynthesis in other organisms is still in its infancy. It is known that various microbes including bacteria produce and secrete ABA, but the overall functional significance of why ABA is synthesized by microbes is not known. Here we discuss the functional involvement of ABA biosynthesis by a pathogenic fungus. Furthermore, we propose that ABA biosynthesis in plant pathogenic fungi could be targeted for novel fungicidal discovery. Copyright © 2015 Elsevier Ltd. All rights reserved.

Three WRKY transcription factors additively repress abscisic acid and gibberellin signaling in aleurone cells.

PubMed

Zhang, Liyuan; Gu, Lingkun; Ringler, Patricia; Smith, Stanley; Rushton, Paul J; Shen, Qingxi J

2015-07-01

Members of the WRKY transcription factor superfamily are essential for the regulation of many plant pathways. Functional redundancy due to duplications of WRKY transcription factors, however, complicates genetic analysis by allowing single-mutant plants to maintain wild-type phenotypes. Our analyses indicate that three group I WRKY genes, OsWRKY24, -53, and -70, act in a partially redundant manner. All three showed characteristics of typical WRKY transcription factors: each localized to nuclei and yeast one-hybrid assays indicated that they all bind to W-boxes, including those present in their own promoters. Quantitative real time-PCR (qRT-PCR) analyses indicated that the expression levels of the three WRKY genes varied in the different tissues tested. Particle bombardment-mediated transient expression analyses indicated that all three genes repress the GA and ABA signaling in a dosage-dependent manner. Combination of all three WRKY genes showed additive antagonism of ABA and GA signaling. These results suggest that these WRKY proteins function as negative transcriptional regulators of GA and ABA signaling. However, different combinations of these WRKY genes can lead to varied strengths in suppression of their targets. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

GhABF2, a bZIP transcription factor, confers drought and salinity tolerance in cotton (Gossypium hirsutum L.).

PubMed

Liang, Chengzhen; Meng, Zhaohong; Meng, Zhigang; Malik, Waqas; Yan, Rong; Lwin, Khin Myat; Lin, Fazhuang; Wang, Yuan; Sun, Guoqing; Zhou, Tao; Zhu, Tao; Li, Jianying; Jin, Shuangxia; Guo, Sandui; Zhang, Rui

2016-10-07

The bZIP transcription factor (TF) act as an important regulator for the abscisic acid (ABA) mediated abiotic stresses signaling pathways in plants. Here, we reported the cloning and characterization of GhABF2, encoding for typical cotton bZIP TF. Overexpression of GhABF2 significantly improved drought and salt stress tolerance both in Arabidopsis and cotton. However, silencing of GhABF2 made transgenic cotton sensitive to PEG osmotic and salt stress. Expression of GhABF2 was induced by drought and ABA treatments but repressed by high salinity. Transcriptome analysis indicated that GhABF2 increases drought and salt tolerance by regulating genes related to ABA, drought and salt response. The proline contents, activity of superoxide dismutase (SOD) and catalase (CAT) were also significantly increased in GhABF2-overexpression cottons in comparison to wild type after drought and salt treatment. Further, an increase in fiber yield under drought and saline-alkali wetland exhibited the important role of GhABF2 in enhancing the drought and salt tolerance in transgenic lines. In conclusion, manipulation of GhABF2 by biotechnological tools could be a sustainable strategy to deploy drought and salt tolerance in cotton.

Muramyl dipeptide (MDP) induces reactive oxygen species (ROS) generation via the NOD2/COX-2/NOX4 signaling pathway in human umbilical vein endothelial cells (HUVECs).

PubMed

Kong, Ling-Jun; Liu, Xiao-Qian; Xue, Ying; Gao, Wei; Lv, Qian-Zhou

2018-03-20

Vascular endothelium dysfunction caused by oxidative stress accelerates the pathologic process of cardiovascular diseases. NOD2, an essential receptor of innate immune system, has been demonstrated to play a critical role in atherosclerosis. Here, the aim of our study was to investigate the effect and underlying molecular mechanism of muramyl dipeptide (MDP) on NOX4-mediated ROS generation in human umbilical vein endothelial cells (HUVECs). 2,7-dichlorofluorescein diacetate staining was to measure the intracellular ROS level and showed MDP promoted ROS production in a time- and dose-dependent manner. The mRNA and protein levels of NOX4 and COX-2 were detected by real-time PCR and western blot. Small interfering RNA (siRNA) was used to silence NOD2 or COX-2 gene expression and investigate the mechanism of NOD2-mediated signaling pathway in HUVECs. Data showed that MDP induced NOX4 and COX-2 expression in a time- and dose-dependent manner. NOD2 knock-down suppressed up-regulation of COX-2 and NOX4 in HUVECs treated with MDP. Furthermore, silence of COX-2 in HUVECs down-regulated the NOX4 expression after MDP stimulation. Collectively, we indicated that NOD2 played a leading role in MDP-induced COX-2/NOX4/ROS signaling pathway in HUVECs, which was a novel regulatory mechanism in the progress of ROS generation.

Mutations of genes in synthesis of the carotenoid precursors of ABA lead to pre-harvest sprouting and photo-oxidation in rice

PubMed Central

Fang, Jun; Chai, Chenglin; Qian, Qian; Li, Chunlai; Tang, Jiuyou; Sun, Lei; Huang, Zejun; Guo, Xiaoli; Sun, Changhui; Liu, Min; Zhang, Yan; Lu, Qingtao; Wang, Yiqin; Lu, Congming; Han, Bin; Chen, Fan; Cheng, Zhukuan; Chu, Chengcai

2008-01-01

Pre-harvest sprouting (PHS) or vivipary in cereals is an important agronomic trait that results in significant economic loss. A considerable number of mutations that cause PHS have been identified in several species. However, relatively few viviparous mutants in rice (Oryza sativa L.) have been reported. To explore the mechanism of PHS in rice, we carried out an extensive genetic screening and identified 12 PHS mutants (phs). Based on their phenotypes, these phs mutants were classified into three groups. Here we characterize in detail one of these groups, which contains mutations in genes encoding major enzymes of the carotenoid biosynthesis pathway, including phytoene desaturase (OsPDS), ζ-carotene desaturase (OsZDS), carotenoid isomerase (OsCRTISO) and lycopene β-cyclase (β-OsLCY), which are essential for the biosynthesis of carotenoid precursors of ABA. As expected, the amount of ABA was reduced in all four phs mutants compared with that in the wild type. Chlorophyll fluorescence analysis revealed the occurrence of photoinhibition in the photosystem and decreased capacity for eliminating excess energy by thermal dissipation. The greatly increased activities of reactive oxygen species (ROS) scavenging enzymes, and reduced photosystem (PS) II core proteins CP43, CP47 and D1 in leaves of the Oscrtiso/phs3-1 mutant and OsLCY RNAi transgenic rice indicated that photo-oxidative damage occurred in PS II, consistent with the accumulation of ROS in these plants. These results suggest that the impairment of carotenoid biosynthesis causes photo-oxidation and ABA-deficiency phenotypes, of which the latter is a major factor controlling the PHS trait in rice. PMID:18208525

Redox signaling: Potential arbitrator of autophagy and apoptosis in therapeutic response.

PubMed

Zhang, Lu; Wang, Kui; Lei, Yunlong; Li, Qifu; Nice, Edouard Collins; Huang, Canhua

2015-12-01

Redox signaling plays important roles in the regulation of cell death and survival in response to cancer therapy. Autophagy and apoptosis are discrete cellular processes mediated by distinct groups of regulatory and executioner molecules, and both are thought to be cellular responses to various stress conditions including oxidative stress, therefore controlling cell fate. Basic levels of reactive oxygen species (ROS) may function as signals to promote cell proliferation and survival, whereas increase of ROS can induce autophagy and apoptosis by damaging cellular components. Growing evidence in recent years argues for ROS that below detrimental levels acting as intracellular signal transducers that regulate autophagy and apoptosis. ROS-regulated autophagy and apoptosis can cross-talk with each other. However, how redox signaling determines different cell fates by regulating autophagy and apoptosis remains unclear. In this review, we will focus on understanding the delicate molecular mechanism by which autophagy and apoptosis are finely orchestrated by redox signaling and discuss how this understanding can be used to develop strategies for the treatment of cancer. Copyright © 2015 Elsevier Inc. All rights reserved.

A rapid and transient ROS generation by cadmium triggers apoptosis via caspase-dependent pathway in HepG2 cells and this is inhibited through N-acetylcysteine-mediated catalase upregulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oh, Seon-Hee; Lim, Sung-Chul

2006-05-01

Although reactive oxygen species (ROS) have been implicated in cadmium (Cd)-induced hepatotoxicity, the role of ROS in this pathway remains unclear. Therefore, we attempted to determine the molecular mechanisms relevant to Cd-induced cell death in HepG2 cells. Cd was found to induce apoptosis in the HepG2 cells in a time- and dose-dependent fashion, as confirmed by DNA fragmentation analysis and TUNEL staining. In the early stages, both rapid and transient ROS generation triggered apoptosis via Fas activation and subsequent caspase-8-dependent Bid cleavage, as well as by calpain-mediated mitochondrial Bax cleavage. The timing of Bid activation was coincided with the timingmore » at which the mitochondrial transmembrane potential (MMP) collapsed as well as the cytochrome c (Cyt c) released into the cytosol. Furthermore, mitochondrial permeability transition (MPT) pore inhibitors, such as cyclosporin A (CsA) and bongkrekic acid (BA), did not block Cd-induced ROS generation, MMP collapse and Cyt c release. N-acetylcysteine (NAC) pretreatment resulted in the complete inhibition of the Cd-induced apoptosis via catalase upregulation and subsequent Fas downregulation. NAC treatment also completely blocked the Cd-induced intracellular ROS generation, MMP collapse and Cyt c release, indicating that Cd-induced mitochondrial dysfunction may be regulated indirectly by ROS-mediated signaling pathway. Taken together, a rapid and transient ROS generation by Cd triggers apoptosis via caspase-dependent pathway and subsequent mitochondrial pathway. NAC inhibits Cd-induced apoptosis through the blocking of ROS generation as well as the catalase upregulation.« less

Reactive oxygen species are involved in regulating alpha1-adrenoceptor-activated vascular smooth muscle contraction.

PubMed

Tsai, Ming-Ho; Jiang, Meei Jyh

2010-08-23

Reactive oxygen species (ROS) were shown to mediate aberrant contractility in hypertension, yet the physiological roles of ROS in vascular smooth muscle contraction have remained elusive. This study aimed to examine whether ROS regulate alpha1-adrenoceptor-activated contraction by altering myosin phosphatase activities. Using endothelium-denuded rat tail artery (RTA) strips, effects of anti-oxidants on isometric force, ROS production, phosphorylation of the 20-kDa myosin light chain (MLC20), and myosin phosphatase stimulated by alpha1-adrenoceptor agonist phenylephrine were examined. An antioxidant, N-acetyl-L-cysteine (NAC), and two NADPH oxidase inhibitors, apocynin and VAS2870, dose-dependently inhibited contraction activated by phenylephrine. Phenylephrine stimulated superoxide anion production that was diminished by the pretreatment of apocynin, VAS2870, superoxide scavenger tiron or mitochondria inhibitor rotenone, but not by xanthine oxidase inhibitor allopurinol or cyclooxygenase inhibitor indomethacin. Concurrently, NADPH oxidase activity in RTA homogenates increased within 1 min upon phenylephrine stimulation, sustained for 10 min, and was abolished by the co-treatment with apocynin, but not allopurinol or rotenone. Phenylephrine-induced MLC20 phosphorylation was dose-dependently decreased by apocynin. Furthermore, apocynin inhibited phenylephrine-stimulated RhoA translocation to plasma membrane and phosphorylation of both myosin phosphatase regulatory subunit MYPT1Thr855 and myosin phosphatase inhibitor CPI-17Thr38. ROS, probably derived from NADPH oxidase and mitochondria, partially regulate alpha1-adrenoceptor-activated smooth muscle contraction by altering myosin phosphatase-mediated MLC20 phosphorylation through both RhoA/Rho kinase- and CPI-17-dependent pathways.

Upregulation of Hsp72 mediates anoxia/reoxygenation neuroprotection in the freshwater turtle via modulation of ROS.

PubMed

Kesaraju, Shailaja; Nayak, Gauri; Prentice, Howard M; Milton, Sarah L

2014-09-25

The neuroprotective role of Hsp72 has been demonstrated in several ischemic/stroke models to occur primarily through mediation of apoptotic pathways, and a number of heat shock proteins are upregulated in animal models capable of extended anoxic survival. In the present study, we investigated the role of Hsp72 on cell death and apoptotic regulators in one anoxia tolerant model system, the freshwater turtle Trachemys scripta. Since Hsp72 is known to regulate apoptosis through interactions with Bcl-2, we manipulated the levels of Hsp72 and Bcl-2 with siRNA in neuronally enriched primary cell cultures and examined downstream effects. The knockdown of either Hsp72 or Bcl-2 induced cell death during anoxia and reoxygenation. Knockdown of Bcl-2 resulted in increases in apoptotic markers and increased ROS levels 2-fold. However, significant knockdown of Hsp72 did not have any effect on the expression of key mitochondrial apoptotic regulators such as Cytochrome c and caspase-3. Hsp72 knockdown however significantly increased apoptosis inducing factor in both anoxia and reoxygenation and resulted in a six-fold induction of hydrogen peroxide levels. These findings suggest that the neuroprotection offered by Hsp72 in the anoxia/reoxygenation tolerant turtle is through the mediation of ROS levels and not through modulation of caspase-dependent pathways. Copyright © 2014 Elsevier B.V. All rights reserved.

The Putative E3 Ubiquitin Ligase ECERIFERUM9 Regulates Abscisic Acid Biosynthesis and Response during Seed Germination and Postgermination Growth in Arabidopsis.

PubMed

Zhao, Huayan; Zhang, Huoming; Cui, Peng; Ding, Feng; Wang, Guangchao; Li, Rongjun; Jenks, Matthew A; Lü, Shiyou; Xiong, Liming

2014-07-01

The ECERIFERUM9 (CER9) gene encodes a putative E3 ubiquitin ligase that functions in cuticle biosynthesis and the maintenance of plant water status. Here, we found that CER9 is also involved in abscisic acid (ABA) signaling in seeds and young seedlings of Arabidopsis (Arabidopsis thaliana). The germinated embryos of the mutants exhibited enhanced sensitivity to ABA during the transition from reversible dormancy to determinate seedling growth. Expression of the CER9 gene is closely related to ABA levels and displays a similar pattern to that of ABSCISIC ACID-INSENSITIVE5 (ABI5), which encodes a positive regulator of ABA responses in seeds. cer9 mutant seeds exhibited delayed germination that is independent of seed coat permeability. Quantitative proteomic analyses showed that cer9 seeds had a protein profile similar to that of the wild type treated with ABA. Transcriptomics analyses revealed that genes involved in ABA biosynthesis or signaling pathways were differentially regulated in cer9 seeds. Consistent with this, high levels of ABA were detected in dry seeds of cer9. Blocking ABA biosynthesis by fluridone treatment or by combining an ABA-deficient mutation with cer9 attenuated the phenotypes of cer9. Whereas introduction of the abi1-1, abi3-1, or abi4-103 mutation could completely eliminate the ABA hypersensitivity of cer9, introduction of abi5 resulted only in partial suppression. These results indicate that CER9 is a novel negative regulator of ABA biosynthesis and the ABA signaling pathway during seed germination. © 2014 American Society of Plant Biologists. All Rights Reserved.

Mucosal reactive oxygen species decrease virulence by disrupting Campylobacter jejuni phosphotyrosine signaling

PubMed Central

Corcionivoschi, Nicolae; Alvarez, Luis A.; Sharp, Thomas H.; Strengert, Monika; Alemka, Abofu; Mantell, Judith; Verkade, Paul; Knaus, Ulla G.; Bourke, Billy

2013-01-01

Summary Reactive oxygen species (ROS) play key roles in mucosal defense, yet how they are induced and the consequences for pathogens are unclear. We report that ROS generated by epithelial NADPH oxidases (Nox1/Duox2) during Campylobacter jejuni infection impair bacterial capsule formation and virulence by altering bacterial signal transduction. Upon C. jejuni invasion, ROS released from the intestinal mucosa inhibit the bacterial phosphotyrosine network that is regulated by the outer membrane tyrosine kinase Cjtk (Cj1170/OMP50). ROS-mediated Cjtk inactivation results in an overall decrease in the phosphorylation of C. jejuni outer membrane / periplasmic proteins including UDP-GlcNAc/Glc 4-epimerase (Gne), an enzyme required for N-glycosylation and capsule formation. Cjtk positively regulates Gne by phosphorylating an active site tyrosine, while loss of Cjtk or ROS treatment inhibits Gne activity, causing altered polysaccharide synthesis. Thus, epithelial NADPH oxidases are an early antibacterial defense system in the intestinal mucosa that modifies virulence by disrupting bacterial signaling. PMID:22817987

The Zinc Finger Transcription Factor SlZFP2 Negatively Regulates Abscisic Acid Biosynthesis and Fruit Ripening in Tomato1

PubMed Central

Weng, Lin; Zhao, Fangfang; Li, Rong; Xu, Changjie; Chen, Kunsong

2015-01-01

Abscisic acid (ABA) regulates plant development and adaptation to environmental conditions. Although the ABA biosynthesis pathway in plants has been thoroughly elucidated, how ABA biosynthetic genes are regulated at the molecular level during plant development is less well understood. Here, we show that the tomato (Solanum lycopersicum) zinc finger transcription factor SlZFP2 is involved in the regulation of ABA biosynthesis during fruit development. Overexpression of SlZFP2 resulted in multiple phenotypic changes, including more branches, early flowering, delayed fruit ripening, lighter seeds, and faster seed germination, whereas down-regulation of its expression caused problematic fruit set, accelerated ripening, and inhibited seed germination. SlZFP2 represses ABA biosynthesis during fruit development through direct suppression of the ABA biosynthetic genes NOTABILIS, SITIENS, and FLACCA and the aldehyde oxidase SlAO1. We also show that SlZFP2 regulates fruit ripening through transcriptional suppression of the ripening regulator COLORLESS NON-RIPENING. Using bacterial one-hybrid screening and a selected amplification and binding assay, we identified the (A/T)(G/C)TT motif as the core binding sequence of SlZFP2. Furthermore, by RNA sequencing profiling, we found that 193 genes containing the SlZFP2-binding motifs in their promoters were differentially expressed in 2 d post anthesis fruits between the SlZFP2 RNA interference line and its nontransgenic sibling. We propose that SlZFP2 functions as a repressor to fine-tune ABA biosynthesis during fruit development and provides a potentially valuable tool for dissecting the role of ABA in fruit ripening. PMID:25637453

Up-regulation of miR-26a promotes apoptosis of hypoxic rat neonatal cardiomyocytes by repressing GSK-3β protein expression.

PubMed

Suh, Jong Hui; Choi, Eunmi; Cha, Min-Ji; Song, Byeong-Wook; Ham, Onju; Lee, Se-Yeon; Yoon, Cheesoon; Lee, Chang-Yeon; Park, Jun-Hee; Lee, Sun Hee; Hwang, Ki-Chul

2012-06-29

Myocardial ischemia is the major cause of morbidity and mortality due to cardiovascular diseases. This disease is a severe stress condition that causes extensive biochemical changes which trigger cardiac cell death. Stress conditions such as deprivation of glucose and oxygen activate the endoplasmic reticulum in the cytoplasm of cells, including cardiomyocytes, to generate and propagate apoptotic signals in response to these conditions. microRNAs (miRNAs) are a class of small non-coding RNAs that mediate posttranscriptional gene silencing. The miRNAs play important roles in regulating cardiac physiological and pathological events such as hypertrophy, apoptosis, and heart failure. However, the roles of miRNAs in reactive oxygen species (ROS)-mediated injury on cardiomyocytes are uncertain. In this study, we identified at the apoptotic concentration of H(2)O(2), miR-26a expression was increased. To determine the potential roles of miR-26a in H(2)O(2)-mediated cardiac apoptosis, miR-26a expression was regulated by a miR-26a or an anti-miR-26a. Overexpression of miR-26a increased apoptosis as determined by upregulation of Annexin V/PI positive cell population, caspase-3 activity and expression of pro-apoptotic signal molecules, whereas inhibition of miR-26a reduced apoptosis. We identified GSK3B as a direct downstream target of miR-26a. Furthermore, miR-26a attenuated viability and increased caspase-3 activity in normal cardiomyocytes. This study demonstrates that miR-26a promotes ROS-induced apoptosis in cardiomyocytes. Thus, miR-26a affects ROS-mediated gene regulation and cellular injury response. Copyright © 2012 Elsevier Inc. All rights reserved.

Gladiolus hybridus ABSCISIC ACID INSENSITIVE 5 (GhABI5) is an important transcription factor in ABA signaling that can enhance Gladiolus corm dormancy and Arabidopsis seed dormancy

PubMed Central

Wu, Jian; Seng, Shanshan; Sui, Juanjuan; Vonapartis, Eliana; Luo, Xian; Gong, Benhe; Liu, Chen; Wu, Chenyu; Liu, Chao; Zhang, Fengqin; He, Junna; Yi, Mingfang

2015-01-01

The phytohormone abscisic acid (ABA) regulates plant development and is crucial for abiotic stress response. In this study, cold storage contributes to reducing endogenous ABA content, resulting in dormancy breaking of Gladiolus. The ABA inhibitor fluridone also promotes germination, suggesting that ABA is an important hormone that regulates corm dormancy. Here, we report the identification and functional characterization of the Gladiolus ABI5 homolog (GhABI5), which is a basic leucine zipper motif transcriptional factor (TF). GhABI5 is expressed in dormant vegetative organs (corm, cormel, and stolon) as well as in reproductive organs (stamen), and it is up-regulated by ABA or drought. Complementation analysis reveals that GhABI5 rescues the ABA insensitivity of abi5-3 during seed germination and induces the expression of downstream ABA response genes in Arabidopsis thaliana (EM1, EM6, and RD29B). Down-regulation of GhABI5 in dormant cormels via virus induced gene silence promotes sprouting and reduces the expression of downstream genes (GhLEA and GhRD29B). The results of this study reveal that GhABI5 regulates bud dormancy (vegetative organ) in Gladiolus in addition to its well-studied function in Arabidopsis seeds (reproductive organ). PMID:26579187

A cytochrome P450, OsDSS1, is involved in growth and drought stress responses in rice (Oryza sativa L.).

PubMed

Tamiru, Muluneh; Undan, Jerwin R; Takagi, Hiroki; Abe, Akira; Yoshida, Kakoto; Undan, Jesusa Q; Natsume, Satoshi; Uemura, Aiko; Saitoh, Hiromasa; Matsumura, Hideo; Urasaki, Naoya; Yokota, Takao; Terauchi, Ryohei

2015-05-01

Cytochrome P450s are among the largest protein coding gene families in plant genomes. However, majority of the genes remain uncharacterized. Here, we report the characterization of dss1, a rice mutant showing dwarfism and reduced grain size. The dss1 phenotype is caused by a non-synonymous point mutation we identified in DSS1, which is member of a P450 gene cluster located on rice chromosome 3 and corresponds to the previously reported CYP96B4/SD37 gene. Phenotypes of several dwarf mutants characterized in rice are associated with defects in the biosynthesis or perception of the phytohormones gibberellins (GAs) and brassinosteroids (BRs). However, both GA and BR failed to rescue the dss1 phenotype. Hormone profiling revealed the accumulation of abscisic acid (ABA) and ABA metabolites, as well as significant reductions in GA19 and GA53 levels, precursors of the bioactive GA1, in the mutant. The dss1 contents of cytokinin and auxins were not significantly different from wild-type plants. Consistent with the accumulation of ABA and metabolites, germination and early growth was delayed in dss1, which also exhibited an enhanced tolerance to drought. Additionally, expressions of members of the DSS1/CYP96B gene cluster were regulated by drought stress and exogenous ABA. RNA-seq-based transcriptome profiling revealed, among others, that cell wall-related genes and genes involved in lipid metabolism were up- and down-regulated in dss1, respectively. Taken together, these findings suggest that DSS1 mediates growth and stress responses in rice by fine-tuning GA-to-ABA balance, and might as well play a role in lipid metabolism.

Variable responses of small and large human hepatocytes to hypoxia and hypoxia/reoxygenation (H-R).

PubMed

Bhogal, Ricky H; Weston, Christopher J; Curbishley, Stuart M; Bhatt, Anand N; Adams, David H; Afford, Simon C

2011-03-23

Hypoxia and hypoxia-reoxygenation (H-R) regulate human hepatocyte cell death by mediating the accumulation of reactive oxygen species (ROS). Hepatocytes within the liver are organised into peri-portal (PP) and peri-venous (PV) subpopulations. PP and PV hepatocytes differ in size and function. We investigated whether PP and PV human hepatocytes exhibit differential susceptibility to hypoxic stress. Isolated hepatocytes were used in an in vitro model of hypoxia and H-R. ROS production and cell death were assessed using flow cytometry. PV, and not PP hepatocytes, accumulate intracellular ROS in a mitochondrial dependent manner during hypoxia and H-R. This increased ROS regulates hepatocyte apoptosis and necrosis via a mitochondrial pathway. These findings have implications on the understanding of liver injury and application of potential therapeutic strategies. Copyright © 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

SnRK1A-Interacting Negative Regulators Modulate the Nutrient Starvation Signaling Sensor SnRK1 in Source-Sink Communication in Cereal Seedlings under Abiotic Stress[C][W

PubMed Central

Lin, Chien-Ru; Lee, Kuo-Wei; Chen, Chih-Yu; Hong, Ya-Fang; Chen, Jyh-Long; Lu, Chung-An; Chen, Ku-Ting; Ho, Tuan-Hua David; Yu, Su-May

2014-01-01

In plants, source-sink communication plays a pivotal role in crop productivity, yet the underlying regulatory mechanisms are largely unknown. The SnRK1A protein kinase and transcription factor MYBS1 regulate the sugar starvation signaling pathway during seedling growth in cereals. Here, we identified plant-specific SnRK1A-interacting negative regulators (SKINs). SKINs antagonize the function of SnRK1A, and the highly conserved GKSKSF domain is essential for SKINs to function as repressors. Overexpression of SKINs inhibits the expression of MYBS1 and hydrolases essential for mobilization of nutrient reserves in the endosperm, leading to inhibition of seedling growth. The expression of SKINs is highly inducible by drought and moderately by various stresses, which is likely related to the abscisic acid (ABA)–mediated repression of SnRK1A under stress. Overexpression of SKINs enhances ABA sensitivity for inhibition of seedling growth. ABA promotes the interaction between SnRK1A and SKINs and shifts the localization of SKINs from the nucleus to the cytoplasm, where it binds SnRK1A and prevents SnRK1A and MYBS1 from entering the nucleus. Our findings demonstrate that SnRK1A plays a key role regulating source-sink communication during seedling growth. Under abiotic stress, SKINs antagonize the function of SnRK1A, which is likely a key factor restricting seedling vigor. PMID:24569770

A new brominated chalcone derivative suppresses the growth of gastric cancer cells in vitro and in vivo involving ROS mediated up-regulation of DR5 and 4 expression and apoptosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Saiyang; Li, Tingyu; Zhang, Yanbing

A new series of 20 brominated chalcone derivatives were designed, synthesized, and investigated for their effects against the growth of four cancer cell lines (EC109, SKNSH, HepG2, MGC803). Among them, compound 19 which given chemical name of H72, was the most potent one on gastric cancer cell lines (i.e. MGC803, HGC27, SGC7901) with IC{sub 50s} ranged from 3.57 to 5.61 μM. H72 exhibited less cytotoxicity to non-malignant gastric epithelial cells GES-1. H72 treatment of MGC803 and HGC27 induced generation of reactive oxygen species (ROS) leading to activation of caspase 9/3 cascade and mitochondria mediated apoptosis. H72 also up-regulated the expressionmore » of DR5, DR4 and Bim{sub EL}, and down-regulated the expression of Bid, Bcl-xL, and XIAP. N-acetyl cysteine (NAC), a ROS scavenger completely blocked these effects of H72 in MGC803 cells. Intraperitoneal administration of H72 significantly inhibited the growth of MGC803 cells in vivo in a xenograft mouse model without observed toxicity. These results indicated that H72 is a lead brominated chalcone derivate and deserves further investigation for prevention and treatment of gastric cancer. - Highlights: • 20 brominated chalcone derivatives were designed and synthesized. • H72 caused potent cytotoxic activity against MGC803 and less against GES1. • H72 led to activation of caspase 9/3 cascade and mitochondria mediated apoptosis. • H72 induced generation of reactive oxygen species (ROS). • H72 significantly inhibited the growth of MGC803 cells in vivo.« less

A Mechanism for the Temporal Potentiation of Genipin to the Cytotoxicity of Cisplatin in Colon Cancer Cells.

PubMed

Wang, Ruihua; MoYung, K C; Zhao, Y J; Poon, Karen

2016-01-01

To investigate the potentiation effect of Genipin to Cisplatin induced cell senescence in HCT-116 colon cancer cells in vitro. Cell viability was estimated by Propidium iodide and Hoechst 3342, reactive oxygen species (ROS) with DHE, mitochondrial membrane potential (MMP) with JC-1 MMP assay Kit and electron current production with microbial fuel cells (MFC). Genipin inhibited the UCP2 mediated anti-oxidative proton leak significantly promoted the Cisplatin induced ROS and subsequent cell death, which was similar to that of UCP2-siRNA. Cells treated with Cisplatin alone or combined with Genipin, ROS negatively, while MMP positively correlated with cell viability. Cisplatin induced ROS was significantly decreased by detouring electrons to MFC, or increased by Genipin combined treatment. Compensatory effects of UCP2 up-regulation with time against Genipin treatment were suggested. Shorter the Genipin treatment before Cisplatin better promoted the Cisplatin induced ROS and subsequent cell death. The interaction of leaked electron with Cisplatin was important during ROS generation. Inhibition of UCP2-mediated proton leak with Genipin potentiated the cytotoxicity of Cisplatin. Owing to the compensatory effects against Genipin, shorter Genipin treatment before Cisplatin was recommended in order to achieve better potentiation effect.

Quinacrine induces apoptosis in human leukemia K562 cells via p38 MAPK-elicited BCL2 down-regulation and suppression of ERK/c-Jun-mediated BCL2L1 expression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Changchien, Jung-Jung; Chen, Ying-Jung; Huang, Chia-Hui

2015-04-01

Although previous studies have revealed the anti-cancer activity of quinacrine, its effect on leukemia is not clearly resolved. We sought to explore the cytotoxic effect and mechanism of quinacrine action in human leukemia K562 cells. Quinacrine induced K562 cell apoptosis accompanied with ROS generation, mitochondrial depolarization, and down-regulation of BCL2L1 and BCL2. Upon exposure to quinacrine, ROS-mediated p38 MAPK activation and ERK inactivation were observed in K562 cells. Quinacrine-induced cell death and mitochondrial depolarization were suppressed by the p38MAPK inhibitor SB202190 and constitutively active MEK1 over-expression. Activation of p38 MAPK was shown to promote BCL2 degradation. Further, ERK inactivation suppressedmore » c-Jun-mediated transcriptional expression of BCL2L1. Over-expression of BCL2L1 and BCL2 attenuated quinacrine-evoked mitochondrial depolarization and rescued the viability of quinacrine-treated cells. Taken together, our data indicate that quinacrine-induced K562 cell apoptosis is mediated through mitochondrial alterations triggered by p38 MAPK-mediated BCL2 down-regulation and suppression of ERK/c-Jun-mediated BCL2L1 expression. - Highlights: • Quinacrine induces K562 cell apoptosis via down-regulation of BCL2 and BCL2L1. • Quinacrine induces p38 MAPK activation and ERK inactivation in K562 cells. • Quinacrine elicits p38 MAPK-mediated BCL2 down-regulation. • Quinacrine suppresses ERK/c-Jun-mediated BCL2L1 expression.« less

Short-term and continuing stresses differentially interplay with multiple hormones to regulate plant survival and growth.

PubMed

Yang, Cangjing; Liu, Jingjing; Dong, Xinran; Cai, Zhenying; Tian, Weidong; Wang, Xuelu

2014-05-01

The stress phytohormone, abscisic acid (ABA), plays important roles in facilitating plants to survive and grow well under a wide range of stress conditions. Previous gene expression studies mainly focused on plant responses to short-term ABA treatment, but the effect of sustained ABA treatment and their difference are poorly studied. Here, we treated plants with ABA for 1 h or 9 d, and our genome-wide analysis indicated the differentially regulated genes under the two conditions were tremendously different. We analyzed other hormones' signaling changes by using their whole sets of known responsive genes as reporters and integrating feedback regulation of their biosynthesis. We found that, under short-term ABA treatment, signaling outputs of growth-promoting hormones, brassinosteroids and gibberellins, and a biotic stress-responsive hormone, jasmonic acid, were significantly inhibited, while auxin and ethylene signaling outputs were promoted. However, sustained ABA treatment repressed cytokinin and gibberellin signaling, but stimulated auxin signaling. Using several sets of hormone-related mutants, we found candidates in corresponding hormonal signaling pathways, including receptors or transcription regulators, are essential in responding to ABA. Our findings indicate interactions of ABA-dependent stress signals with hormones at different levels are involved in plants to survive under transient stress and to adapt to continuing stressful environments.

The effect of dehydroglyasperin C on UVB-mediated MMPs expression in human HaCaT cells.

PubMed

Xuan, Song Hua; Park, Young Min; Ha, Ji Hoon; Jeong, Yoon Ju; Park, Soo Nam

2017-12-01

The ultraviolet B (UVB) from solar radiation increases the generation of reactive oxygen species (ROS), which mediate the production of matrix metalloproteinases (MMPs), and acts mainly on the epidermis layer of the skin. This study was aimed at assessing the anti-photoaging effects of dehydroglyasperin C isolated from Glycyrrhiza uralensis Fisch on MMPs levels in HaCaT human keratinocytes and to elucidate the underlying mechanism. The cell viability was measured by MTT assay. Expression, phosphorylation and enzymatic activity of the protein were examined using ELISA, Western blot or gelatin zymography. Intracellular ROS measurement was evaluated by fluorescent ELISA and 2',7'-dichlorodihydrofluorescein diacetate (H 2 DCF-DA) assay. In the present study, we found that dehydroglyasperin C markedly inhibited UVB-mediated expression of collagenase (MMP-1) and gelatinase (MMP-9) by inhibiting ROS generation. Dehydroglyasperin C treatment also decreased the UVB irradiation-mediated activation of mitogen-activated protein kinase (MAPK), c-Jun phosphorylation, and c-Fos expression. In addition, the down-regulation of UVB-induced c-Jun phosphorylation caused by dehydroglyasperin C treatment was more than the down-regulation of c-Fos expression in the HaCaT human keratinocytes. Our results indicated that dehydroglyasperin C may function as a potential anti-photoaging agent by inhibiting UVB-mediated MMPs expression via suppression of MAPK and AP-1 signaling. Copyright © 2017 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

SCFAtPP2-B11 modulates ABA signaling by facilitating SnRK2.3 degradation in Arabidopsis thaliana

PubMed Central

Ren, Ziyin; Zhi, Liya; Yao, Bin; Su, Chao; Liu, Liu; Li, Xia

2017-01-01

The phytohormone abscisic acid (ABA) is an essential part of the plant response to abiotic stressors such as drought. Upon the perception of ABA, pyrabactin resistance (PYR)/PYR1-like (PYL)/regulatory components of ABA receptor (RCAR) proteins interact with co-receptor protein phosphatase type 2Cs to permit activation Snf1-related protein kinase2 (SnRK2) kinases, which switch on ABA signaling by phosphorylating various target proteins. Thus, SnRK2 kinases are central regulators of ABA signaling. However, the mechanisms that regulate SnRK2 degradation remain elusive. Here, we show that SnRK2.3 is degradated by 26S proteasome system and ABA promotes its degradation. We found that SnRK2.3 interacts with AtPP2-B11 directly. AtPP2-B11 is an F-box protein that is part of a SKP1/Cullin/F-box E3 ubiquitin ligase complex that negatively regulates plant responses to ABA by specifically promoting the degradation of SnRK2.3. AtPP2-B11 was induced by ABA, and the knockdown of AtPP2-B11 expression markedly increased the ABA sensitivity of plants during seed germination and postgerminative development. Overexpression of AtPP2-B11 does not affect ABA sensitivity, but inhibits the ABA hypersensitive phenotypes of SnRK2.3 overexpression lines. These results reveal a novel mechanism through which AtPP2-B11 specifically degrades SnRK2.3 to attenuate ABA signaling and the abiotic stress response in Arabidopsis. PMID:28787436

Cadmium induces autophagy through ROS-dependent activation of the LKB1-AMPK signaling in skin epidermal cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Son, Young-Ok; Wang Xin; Hitron, John Andrew

2011-09-15

Cadmium is a toxic heavy metal which is environmentally and occupationally relevant. The mechanisms underlying cadmium-induced autophagy are not yet completely understood. The present study shows that cadmium induces autophagy, as demonstrated by the increase of LC3-II formation and the GFP-LC3 puncta cells. The induction of autophagosomes was directly visualized by electron microscopy in cadmium-exposed skin epidermal cells. Blockage of LKB1 or AMPK by siRNA transfection suppressed cadmium-induced autophagy. Cadmium-induced autophagy was inhibited in dominant-negative AMPK-transfected cells, whereas it was accelerated in cells transfected with the constitutively active form of AMPK. mTOR signaling, a negative regulator of autophagy, was downregulatedmore » in cadmium-exposed cells. In addition, cadmium generated reactive oxygen species (ROS) at relatively low levels, and caused poly(ADP-ribose) polymerase-1 (PARP) activation and ATP depletion. Inhibition of PARP by pharmacological inhibitors or its siRNA transfection suppressed ATP reduction and autophagy in cadmium-exposed cells. Furthermore, cadmium-induced autophagy signaling was attenuated by either exogenous addition of catalase and superoxide dismutase, or by overexpression of these enzymes. Consequently, these results suggest that cadmium-mediated ROS generation causes PARP activation and energy depletion, and eventually induces autophagy through the activation of LKB1-AMPK signaling and the down-regulation of mTOR in skin epidermal cells. - Highlights: > Cadmium, a toxic heavy metal, induces autophagic cell death through ROS-dependent activation of the LKB1-AMPK signaling. > Cadmium generates intracellular ROS at low levels and this leads to severe DNA damage and PARP activation, resulting in ATP depletion, which are the upstream events of LKB1-AMPK-mediated autophagy. > This novel finding may contribute to further understanding of cadmium-mediated diseases.« less

Abrus agglutinin promotes irreparable DNA damage by triggering ROS generation followed by ATM-p73 mediated apoptosis in oral squamous cell carcinoma.

PubMed

Sinha, Niharika; Panda, Prashanta K; Naik, Prajna P; Das, Durgesh N; Mukhopadhyay, Subhadip; Maiti, Tapas K; Shanmugam, Muthu K; Chinnathambi, Arunachalam; Zayed, M E; Alharbi, Sulaiman A; Sethi, Gautam; Agarwal, Rajesh; Bhutia, Sujit K

2017-11-01

Oral cancer, a type of head and neck cancer, is ranked as one of the top most malignancies in India. Herein, we evaluated the anticancer efficacy of Abrus agglutinin (AGG), a plant lectin, in oral squamous cell carcinoma. AGG selectively inhibited cell growth, and caused cell cycle arrest and mitochondrial apoptosis through a reactive oxygen species (ROS)-mediated ATM-p73 dependent pathway in FaDu cells. AGG-induced ROS accumulation was identified as the major mechanism regulating apoptosis, DNA damage and DNA-damage response, which were significantly reversed by ROS scavenger N-acetylcysteine (NAC). Moreover, AGG was found to interact with mitochondrial manganese-dependent superoxide dismutase that might inhibit its activity and increase ROS in FaDu cells. In oral cancer p53 is mutated, thus we focused on p73; AGG resulted in p73 upregulation and knock down of p73 caused a decrease in AGG-induced apoptosis. Interestingly, AGG-dependent p73 expression was found to be regulated by ROS, which was reversed by NAC treatment. A reduction in the level of p73 in AGG-treated shATM cells was found to be associated with a decreased apoptosis. Moreover, administration of AGG (50 μg/kg body weight) significantly inhibited the growth of FaDu xenografts in athymic nude mice. In immunohistochemical analysis, the xenografts from AGG-treated mice displayed a decrease in PCNA expression and an increase in caspase-3 activation as compared to the controls. In conclusion, we established a connection among ROS, ATM and p73 in AGG-induced apoptosis, which might be useful in enhancing the therapeutic targeting of p53 deficient oral squamous cell carcinoma. © 2017 Wiley Periodicals, Inc.

Enhanced Mitochondrial Transient Receptor Potential Channel, Canonical Type 3-Mediated Calcium Handling in the Vasculature From Hypertensive Rats.

PubMed

Wang, Bin; Xiong, Shiqiang; Lin, Shaoyang; Xia, Weijie; Li, Qiang; Zhao, Zhigang; Wei, Xing; Lu, Zongshi; Wei, Xiao; Gao, Peng; Liu, Daoyan; Zhu, Zhiming

2017-07-15

Mitochondrial Ca 2+ homeostasis is fundamental to the regulation of mitochondrial reactive oxygen species (ROS) generation and adenosine triphosphate production. Recently, transient receptor potential channel, canonical type 3 (TRPC3), has been shown to localize to the mitochondria and to play a role in maintaining mitochondrial calcium homeostasis. Inhibition of TRPC3 attenuates vascular calcium influx in spontaneously hypertensive rats (SHRs). However, it remains elusive whether mitochondrial TRPC3 participates in hypertension by increasing mitochondrial calcium handling and ROS production. In this study we demonstrated increased TRPC3 expression in purified mitochondria in the vasculature from SHRs, which facilitates enhanced mitochondrial calcium uptake and ROS generation compared with Wistar-Kyoto rats. Furthermore, inhibition of TRPC3 by its specific inhibitor, Pyr3, significantly decreased the vascular mitochondrial ROS production and H 2 O 2 synthesis and increased adenosine triphosphate content. Administration of telmisartan can improve these abnormalities. This beneficial effect was associated with improvement of the mitochondrial respiratory function through recovering the activity of pyruvate dehydrogenase in the vasculature of SHRs. In vivo, chronic administration of telmisartan suppressed TRPC3-mediated excessive mitochondrial ROS generation and vasoconstriction in the vasculature of SHRs. More importantly, TRPC3 knockout mice exhibited significantly ameliorated hypertension through reduction of angiotensin II-induced mitochondrial ROS generation. Together, we give experimental evidence for a potential mechanism by which enhanced TRPC3 activity at the cytoplasmic and mitochondrial levels contributes to redox signaling and calcium dysregulation in the vasculature from SHRs. Angiotensin II or telmisartan can regulate [Ca 2+ ] mito , ROS production, and mitochondrial energy metabolism through targeting TRPC3. © 2017 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley.

The Rose (Rosa hybrida) NAC Transcription Factor 3 Gene, RhNAC3, Involved in ABA Signaling Pathway Both in Rose and Arabidopsis

PubMed Central

Lü, Peitao; Liu, Jitao; Gao, Junping; Zhang, Changqing

2014-01-01

Plant transcription factors involved in stress responses are generally classified by their involvement in either the abscisic acid (ABA)-dependent or the ABA-independent regulatory pathways. A stress-associated NAC gene from rose (Rosa hybrida), RhNAC3, was previously found to increase dehydration tolerance in both rose and Arabidopsis. However, the regulatory mechanism involved in RhNAC3 action is still not fully understood. In this study, we isolated and analyzed the upstream regulatory sequence of RhNAC3 and found many stress-related cis-elements to be present in the promoter, with five ABA-responsive element (ABRE) motifs being of particular interest. Characterization of Arabidopsis thaliana plants transformed with the putative RhNAC3 promoter sequence fused to the β-glucuronidase (GUS) reporter gene revealed that RhNAC3 is expressed at high basal levels in leaf guard cells and in vascular tissues. Moreover, the ABRE motifs in the RhNAC3 promoter were observed to have a cumulative effect on the transcriptional activity of this gene both in the presence and absence of exogenous ABA. Overexpression of RhNAC3 in A. thaliana resulted in ABA hypersensitivity during seed germination and promoted leaf closure after ABA or drought treatments. Additionally, the expression of 11 ABA-responsive genes was induced to a greater degree by dehydration in the transgenic plants overexpressing RhNAC3 than control lines transformed with the vector alone. Further analysis revealed that all these genes contain NAC binding cis-elements in their promoter regions, and RhNAC3 was found to partially bind to these putative NAC recognition sites. We further found that of 219 A. thaliana genes previously shown by microarray analysis to be regulated by heterologous overexpression RhNAC3, 85 are responsive to ABA. In rose, the expression of genes downstream of the ABA-signaling pathways was also repressed in RhNAC3-silenced petals. Taken together, we propose that the rose RhNAC3 protein could mediate ABA signaling both in rose and in A. thaliana. PMID:25290154

The rose (Rosa hybrida) NAC transcription factor 3 gene, RhNAC3, involved in ABA signaling pathway both in rose and Arabidopsis.

PubMed

Jiang, Guimei; Jiang, Xinqiang; Lü, Peitao; Liu, Jitao; Gao, Junping; Zhang, Changqing

2014-01-01

Plant transcription factors involved in stress responses are generally classified by their involvement in either the abscisic acid (ABA)-dependent or the ABA-independent regulatory pathways. A stress-associated NAC gene from rose (Rosa hybrida), RhNAC3, was previously found to increase dehydration tolerance in both rose and Arabidopsis. However, the regulatory mechanism involved in RhNAC3 action is still not fully understood. In this study, we isolated and analyzed the upstream regulatory sequence of RhNAC3 and found many stress-related cis-elements to be present in the promoter, with five ABA-responsive element (ABRE) motifs being of particular interest. Characterization of Arabidopsis thaliana plants transformed with the putative RhNAC3 promoter sequence fused to the β-glucuronidase (GUS) reporter gene revealed that RhNAC3 is expressed at high basal levels in leaf guard cells and in vascular tissues. Moreover, the ABRE motifs in the RhNAC3 promoter were observed to have a cumulative effect on the transcriptional activity of this gene both in the presence and absence of exogenous ABA. Overexpression of RhNAC3 in A. thaliana resulted in ABA hypersensitivity during seed germination and promoted leaf closure after ABA or drought treatments. Additionally, the expression of 11 ABA-responsive genes was induced to a greater degree by dehydration in the transgenic plants overexpressing RhNAC3 than control lines transformed with the vector alone. Further analysis revealed that all these genes contain NAC binding cis-elements in their promoter regions, and RhNAC3 was found to partially bind to these putative NAC recognition sites. We further found that of 219 A. thaliana genes previously shown by microarray analysis to be regulated by heterologous overexpression RhNAC3, 85 are responsive to ABA. In rose, the expression of genes downstream of the ABA-signaling pathways was also repressed in RhNAC3-silenced petals. Taken together, we propose that the rose RhNAC3 protein could mediate ABA signaling both in rose and in A. thaliana.

The Role of Reactive-Oxygen-Species in Microbial Persistence and Inflammation

PubMed Central

Spooner, Ralee; Yilmaz, Özlem

2011-01-01

The mechanisms of chronic infections caused by opportunistic pathogens are of keen interest to both researchers and health professionals globally. Typically, chronic infectious disease can be characterized by an elevation in immune response, a process that can often lead to further destruction. Reactive-Oxygen-Species (ROS) have been strongly implicated in the aforementioned detrimental response by host that results in self-damage. Unlike excessive ROS production resulting in robust cellular death typically induced by acute infection or inflammation, lower levels of ROS produced by host cells are increasingly recognized to play a critical physiological role for regulating a variety of homeostatic cellular functions including growth, apoptosis, immune response, and microbial colonization. Sources of cellular ROS stimulation can include “danger-signal-molecules” such as extracellular ATP (eATP) released by stressed, infected, or dying cells. Particularly, eATP-P2X7 receptor mediated ROS production has been lately found to be a key modulator for controlling chronic infection and inflammation. There is growing evidence that persistent microbes can alter host cell ROS production and modulate eATP-induced ROS for maintaining long-term carriage. Though these processes have yet to be fully understood, exploring potential positive traits of these “injurious” molecules could illuminate how opportunistic pathogens maintain persistence through physiological regulation of ROS signaling. PMID:21339989

The basic biology of redoxosomes in cytokine-mediated signal transduction and implications for disease-specific therapies.

PubMed

Spencer, Netanya Y; Engelhardt, John F

2014-03-18

Redox reactions have been established as major biological players in many cellular signaling pathways. Here we review mechanisms of redox signaling with an emphasis on redox-active signaling endosomes. Signals are transduced by relatively few reactive oxygen species (ROS), through very specific redox modifications of numerous proteins and enzymes. Although ROS signals are typically associated with cellular injury, these signaling pathways are also critical for maintaining cellular health at homeostasis. An important component of ROS signaling pertains to localization and tightly regulated signal transduction events within discrete microenvironments of the cell. One major aspect of this specificity is ROS compartmentalization within membrane-enclosed organelles such as redoxosomes (redox-active endosomes) and the nuclear envelope. Among the cellular proteins that produce superoxide are the NADPH oxidases (NOXes), transmembrane proteins that are implicated in many types of redox signaling. NOXes produce superoxide on only one side of a lipid bilayer; as such, their orientation dictates the compartmentalization of ROS and the local control of signaling events limited by ROS diffusion and/or movement through channels associated with the signaling membrane. NOX-dependent ROS signaling pathways can also be self-regulating, with molecular redox sensors that limit the local production of ROS required for effective signaling. ROS regulation of the Rac-GTPase, a required co-activator of many NOXes, is an example of this type of sensor. A deeper understanding of redox signaling pathways and the mechanisms that control their specificity will provide unique therapeutic opportunities for aging, cancer, ischemia-reperfusion injury, and neurodegenerative diseases.

The Basic Biology of Redoxosomes in Cytokine-Mediated Signal Transduction and Implications for Disease-Specific Therapies

PubMed Central

2015-01-01

Redox reactions have been established as major biological players in many cellular signaling pathways. Here we review mechanisms of redox signaling with an emphasis on redox-active signaling endosomes. Signals are transduced by relatively few reactive oxygen species (ROS), through very specific redox modifications of numerous proteins and enzymes. Although ROS signals are typically associated with cellular injury, these signaling pathways are also critical for maintaining cellular health at homeostasis. An important component of ROS signaling pertains to localization and tightly regulated signal transduction events within discrete microenvironments of the cell. One major aspect of this specificity is ROS compartmentalization within membrane-enclosed organelles such as redoxosomes (redox-active endosomes) and the nuclear envelope. Among the cellular proteins that produce superoxide are the NADPH oxidases (NOXes), transmembrane proteins that are implicated in many types of redox signaling. NOXes produce superoxide on only one side of a lipid bilayer; as such, their orientation dictates the compartmentalization of ROS and the local control of signaling events limited by ROS diffusion and/or movement through channels associated with the signaling membrane. NOX-dependent ROS signaling pathways can also be self-regulating, with molecular redox sensors that limit the local production of ROS required for effective signaling. ROS regulation of the Rac-GTPase, a required co-activator of many NOXes, is an example of this type of sensor. A deeper understanding of redox signaling pathways and the mechanisms that control their specificity will provide unique therapeutic opportunities for aging, cancer, ischemia-reperfusion injury, and neurodegenerative diseases. PMID:24555469

MIR846 and MIR842 comprise a cistronic MIRNA pair that is regulated by abscisic acid by alternative splicing in roots of Arabidopsis

PubMed Central

Jia, Fan; Rock, Christopher D.

2013-01-01

MicroRNAs (miRNAs) are ~21-nucleotide long endogenous small RNAs that regulate gene expression through post-transcriptional or transcriptional gene silencing (PTGS/TGS) and/or translational inhibition. miRNAs can arise from the “exon” of a MIRNA gene, from an intron (e.g. mirtrons in animals), or from the antisense strand of a protein coding gene (natural antisense microRNAs, nat-miRNAs). Here we demonstrate that two functionally related miRNAs, miR842 and miR846, arise from the same transcription unit but from alternate splicing isoforms. miR846 is expressed only from Isoform1 while in Isoforms2 and -3, a part of pre-miR846 containing the miRNA* sequence is included in the intron. The splicing of the intron truncates the pre-MIRNA and disrupts the expression of the mature miR846.. We name this novel phenomenon splicing-regulated miRNA. Abscisic acid (ABA) is shown to mediate the alternative splicing event by reducing the functional Isoform1 and increasing the non-functional Isoform3, thus repressing the expression of miR846 concomitant with accumulation of an ABA-inducible target jacalin At5g28520 mRNA, whose cleavage was shown by modified 5′-RACE. This regulation shows the functional importance of splicing-regulated miRNA and suggests possible mechanisms for altered ABA response phenotypes of miRNA biogenesis mutants. A. lyrata-MIR842 and Aly-MIR846 have conserved genomic arrangements with A. thaliana and candidate target jacalins, similar primary transcript structures and intron processing, and better miRNA-miRNA* pairings, suggesting that the interactions between ABA, MIR842, MIR846 and jacalins are similar in A. lyrata. Together, splicing-regulated miRNAs, nat-miRNAs/inc-miRNAs and mirtrons illustrate the complexity of MIRNA genes, the importance of introns in the biogenesis and regulation of miRNAs, and raise questions about the processes and molecular mechanisms that drive MIRNA evolution. PMID:23341152

Cadmium stress alters the redox reaction and hormone balance in oilseed rape (Brassica napus L.) leaves.

PubMed

Yan, Hui; Filardo, Fiona; Hu, Xiaotao; Zhao, Xiaomin; Fu, DongHui

2016-02-01

In order to understand the physiological response of oilseed rape (Brassica napus L.) leaves to cadmium (Cd) stress and exploit the physiological mechanisms involved in Cd tolerance, macro-mineral and chlorophyll concentrations, reactive oxygen species (ROS) accumulation, activities of enzymatic antioxidants, nonenzymatic compounds metabolism, endogenous hormonal changes, and balance in leaves of oilseed rape exposed to 0, 100, or 200 μM CdSO4 were investigated. The results showed that under Cd exposure, Cd concentrations in the leaves continually increased while macro-minerals and chlorophyll concentrations decreased significantly. Meanwhile, with increased Cd stress, superoxide anion (O2(• -)) production rate and hydrogen peroxide (H2O2) concentrations in the leaves increased significantly, which caused malondialdehyde (MDA) accumulation and oxidative stress. For scavenging excess accumulated ROS and alleviating oxidative injury in the leaves, the activity of enzymatic antioxidants, such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), was increased significantly at certain stress levels. However, with increased Cd stress, the antioxidant enzyme activities all showed a trend towards reduction. The nonenzymatic antioxidative compounds, such as proline and total soluble sugars, accumulated continuously with increased Cd stress to play a long-term role in scavenging ROS. In addition, ABA levels also increased continuously with Cd stress while ZR decreased and the ABA/ZR ratio increased, which might also be providing a protective role against Cd toxicity.

Oxido-reductive regulation of vascular remodeling by receptor tyrosine kinase ROS1

PubMed Central

Ali, Ziad A.; de Jesus Perez, Vinicio; Yuan, Ke; Orcholski, Mark; Pan, Stephen; Qi, Wei; Chopra, Gaurav; Adams, Christopher; Kojima, Yoko; Leeper, Nicholas J.; Qu, Xiumei; Zaleta-Rivera, Kathia; Kato, Kimihiko; Yamada, Yoshiji; Oguri, Mitsutoshi; Kuchinsky, Allan; Hazen, Stanley L.; Jukema, J. Wouter; Ganesh, Santhi K.; Nabel, Elizabeth G.; Channon, Keith; Leon, Martin B.; Charest, Alain; Quertermous, Thomas; Ashley, Euan A.

2014-01-01

Angioplasty and stenting is the primary treatment for flow-limiting atherosclerosis; however, this strategy is limited by pathological vascular remodeling. Using a systems approach, we identified a role for the network hub gene glutathione peroxidase-1 (GPX1) in pathological remodeling following human blood vessel stenting. Constitutive deletion of Gpx1 in atherosclerotic mice recapitulated this phenotype of increased vascular smooth muscle cell (VSMC) proliferation and plaque formation. In an independent patient cohort, gene variant pair analysis identified an interaction of GPX1 with the orphan protooncogene receptor tyrosine kinase ROS1. A meta-analysis of the only genome-wide association studies of human neointima-induced in-stent stenosis confirmed the association of the ROS1 variant with pathological remodeling. Decreased GPX1 expression in atherosclerotic mice led to reductive stress via a time-dependent increase in glutathione, corresponding to phosphorylation of the ROS1 kinase activation site Y2274. Loss of GPX1 function was associated with both oxidative and reductive stress, the latter driving ROS1 activity via s-glutathiolation of critical residues of the ROS1 tyrosine phosphatase SHP-2. ROS1 inhibition with crizotinib and deglutathiolation of SHP-2 abolished GPX1-mediated increases in VSMC proliferation while leaving endothelialization intact. Our results indicate that GPX1-dependent alterations in oxido-reductive stress promote ROS1 activation and mediate vascular remodeling. PMID:25401476

Transcriptome analysis reveals key roles of AtLBR-2 in LPS-induced defense responses in plants.

PubMed

Iizasa, Sayaka; Iizasa, Ei'ichi; Watanabe, Keiichi; Nagano, Yukio

2017-12-29

Lipopolysaccharide (LPS) from Gram-negative bacteria cause innate immune responses in animals and plants. The molecules involved in LPS signaling in animals are well studied, whereas those in plants are not yet as well documented. Recently, we identified Arabidopsis AtLBR-2, which binds to LPS from Pseudomonas aeruginosa (pLPS) directly and regulates pLPS-induced defense responses, such as pathogenesis-related 1 (PR1) expression and reactive oxygen species (ROS) production. In this study, we investigated the pLPS-induced transcriptomic changes in wild-type (WT) and the atlbr-2 mutant Arabidopsis plants using RNA-Seq technology. RNA-Seq data analysis revealed that pLPS treatment significantly altered the expression of 2139 genes, with 605 up-regulated and 1534 down-regulated genes in WT. Gene ontology (GO) analysis on these genes showed that GO terms, "response to bacterium", "response to salicylic acid (SA) stimulus", and "response to abscisic acid (ABA) stimulus" were enriched amongst only in up-regulated genes, as compared to the genes that were down-regulated. Comparative analysis of differentially expressed genes between WT and the atlbr-2 mutant revealed that 65 genes were up-regulated in WT but not in the atlbr-2 after pLPS treatment. Furthermore, GO analysis on these 65 genes demonstrated their importance for the enrichment of several defense-related GO terms, including "response to bacterium", "response to SA stimulus", and "response to ABA stimulus". We also found reduced levels of pLPS-induced conjugated SA glucoside (SAG) accumulation in atlbr-2 mutants, and no differences were observed in the gene expression levels in SA-treated WT and the atlbr-2 mutants. These 65 AtLBR-2-dependent up-regulated genes appear to be important for the enrichment of some defense-related GO terms. Moreover, AtLBR-2 might be a key molecule that is indispensable for the up-regulation of defense-related genes and for SA signaling pathway, which is involved in defense against pathogens containing LPS.

A Role for Barley CRYPTOCHROME1 in Light Regulation of Grain Dormancy and Germination[W][OPEN

PubMed Central

Barrero, Jose M.; Downie, A. Bruce; Xu, Qian; Gubler, Frank

2014-01-01

It is well known that abscisic acid (ABA) plays a central role in the regulation of seed dormancy and that transcriptional regulation of genes encoding ABA biosynthetic and degradation enzymes is responsible for determining ABA content. However, little is known about the upstream signaling pathways impinging on transcription to ultimately regulate ABA content or how environmental signals (e.g., light and cold) might direct such expression in grains. Our previous studies indicated that light is a key environmental signal inhibiting germination in dormant grains of barley (Hordeum vulgare), wheat (Triticum aestivum), and Brachypodium distachyon and that this effect attenuates as after-ripening progresses further. We found that the blue component of the light spectrum inhibits completion of germination in barley by inducing the expression of the ABA biosynthetic gene 9-cis-epoxycarotenoid dioxygenase and dampening expression of ABA 8’-hydroxylase, thus increasing ABA content in the grain. We have now created barley transgenic lines downregulating the genes encoding the blue light receptors CRYTOCHROME (CRY1) and CRY2. Our results demonstrate that CRY1 is the key receptor perceiving and transducing the blue light signal in dormant grains. PMID:24642944

TabHLH1, a bHLH-type transcription factor gene in wheat, improves plant tolerance to Pi and N deprivation via regulation of nutrient transporter gene transcription and ROS homeostasis.

PubMed

Yang, Tongren; Hao, Lin; Yao, Sufei; Zhao, Yuanyuan; Lu, Wenjing; Xiao, Kai

2016-07-01

Basic helix-loop-helix (bHLH) transcription factors (TFs) comprise a large TF family and act as crucial regulators in various biological processes in plants. Here, we report the functional characterization of TabHLH1, a bHLH TF member in wheat (Triticum aestivum). TabHLH1 shares conserved bHLH domain and targets to nucleus with transactivation activity. Upon Pi and N deprivation, the expression of TabHLH1 was up-regulated in roots and leaves, showing a pattern to be gradually increased within 23-h treatment regimes. The lines with overexpression of TabHLH1 exhibited drastically improved tolerance to Pi and N deprivation, showing larger plant phenotype, more biomass, higher concentration and more accumulation of P and N than wild type (WT) upon the Pi- and N-starvation stresses. NtPT1 and NtNRT2.2, the genes encoding phosphate transporter (PT) and nitrate transporter (NRT) in tobacco, respectively, showed up-regulated expression in TabHLH1-overexpressing plants; knockdown expression of them led to deteriorated growth feature, lowered biomass, and decreased nutrient accumulation of plants under Pi- and N-deficient conditions. Compared with WT, the TabHLH1-overexpressing plants also showed lowered reactive oxygen species (ROS) accumulation and improved antioxidant enzyme (AE) activities, such as those of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). NtSOD1, NtCAT1, and NtPOD1;6 that encode SOD, CAT, and POD, respectively, were up-regulated in TabHLH1-overexpressing plants. Further knockdown of these AE gene expression caused reduced antioxidant enzymatic activities, indicative of their crucial roles in mediating cellular ROS homeostasis in Pi- and N-starvation conditions. Together, TabHLH1 plays an important role in mediating adaptation to the Pi- and N-starvation stresses through transcriptional regulation of a set of genes encoding PT, NRT and AEs that mediate the taken up of Pi and N and the cellular homeostasis of ROS initiated by the nutrient stresses. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Elucidation and functional characterization of CsPSY and CsUGT promoters in Crocus sativus L.

PubMed Central

Bhat, Archana; Mishra, Sonal; Kaul, Sanjana

2018-01-01

The dried stigmas of Crocus sativus constitute the saffron, which is considered to be the costliest spice of the world. Saffron is valuable for its constituents, which are mainly apocarotenoids. In order to enhance the production of apocarotenoids, it is imperative to understand the regulation of apocarotenoid biosynthetic pathway. In C. sativus, although the pathway has been elucidated, the information regarding the regulation of the pathwaygenes is scanty. During the present investigation, the characterization of promoters regulating the expression of two important genes i.e. CsPSY and CsUGT was performed. We successfully cloned the promoters of both the genes, which were functionally characterized in Crocus sativus and Nicotiana tabaccum. In silico analysis of the promoters demonstrated the presence of several important cis regulatory elements responding tolight, hormonesand interaction with transcription factors (TFs). Further analysis suggested the regulation of CsPSY promoter by Abscisic acid (ABA) and that of CsUGT by Gibberellic acid (GA). In addition, we also observed ABA and GA mediated modulation in the expression of significant TFs and CsPSY and CsUGT transcripts. Overall, the study addresses issues related to regulation of key genes of apocarotenoid pathway in C.sativus. PMID:29634744

Elucidation and functional characterization of CsPSY and CsUGT promoters in Crocus sativus L.

PubMed

Bhat, Archana; Mishra, Sonal; Kaul, Sanjana; Dhar, Manoj K

2018-01-01

The dried stigmas of Crocus sativus constitute the saffron, which is considered to be the costliest spice of the world. Saffron is valuable for its constituents, which are mainly apocarotenoids. In order to enhance the production of apocarotenoids, it is imperative to understand the regulation of apocarotenoid biosynthetic pathway. In C. sativus, although the pathway has been elucidated, the information regarding the regulation of the pathwaygenes is scanty. During the present investigation, the characterization of promoters regulating the expression of two important genes i.e. CsPSY and CsUGT was performed. We successfully cloned the promoters of both the genes, which were functionally characterized in Crocus sativus and Nicotiana tabaccum. In silico analysis of the promoters demonstrated the presence of several important cis regulatory elements responding tolight, hormonesand interaction with transcription factors (TFs). Further analysis suggested the regulation of CsPSY promoter by Abscisic acid (ABA) and that of CsUGT by Gibberellic acid (GA). In addition, we also observed ABA and GA mediated modulation in the expression of significant TFs and CsPSY and CsUGT transcripts. Overall, the study addresses issues related to regulation of key genes of apocarotenoid pathway in C.sativus.

Hydroxychavicol, a betel leaf component, inhibits prostate cancer through ROS-driven DNA damage and apoptosis.

PubMed

Gundala, Sushma Reddy; Yang, Chunhua; Mukkavilli, Rao; Paranjpe, Rutugandha; Brahmbhatt, Meera; Pannu, Vaishali; Cheng, Alice; Reid, Michelle D; Aneja, Ritu

2014-10-01

Dietary phytochemicals are excellent ROS-modulating agents and have been shown to effectively enhance ROS levels beyond toxic threshold in cancer cells to ensure their selective killing while leaving normal cells unscathed. Here we demonstrate that hydroxychavicol (HC), extracted and purified from Piper betel leaves, significantly inhibits growth and proliferation via ROS generation in human prostate cancer, PC-3 cells. HC perturbed cell-cycle kinetics and progression, reduced clonogenicity and mediated cytotoxicity by ROS-induced DNA damage leading to activation of several pro-apoptotic molecules. In addition, HC treatment elicited a novel autophagic response as evidenced by the appearance of acidic vesicular organelles and increased expression of autophagic markers, LC3-IIb and beclin-1. Interestingly, quenching of ROS with tiron, an antioxidant, offered significant protection against HC-induced inhibition of cell growth and down regulation of caspase-3, suggesting the crucial role of ROS in mediating cell death. The collapse of mitochondrial transmembrane potential by HC further revealed the link between ROS generation and induction of caspase-mediated apoptosis in PC-3 cells. Our data showed remarkable inhibition of prostate tumor xenografts by ~72% upon daily oral administration of 150mg/kg bw HC by quantitative tumor volume measurements and non-invasive real-time bioluminescent imaging. HC was well-tolerated at this dosing level without any observable toxicity. This is the first report to demonstrate the anti-prostate cancer efficacy of HC in vitro and in vivo, which is perhaps attributable to its selective prooxidant activity to eliminate cancer cells thus providing compelling grounds for future preclinical studies to validate its potential usefulness for prostate cancer management. Copyright © 2014 Elsevier Inc. All rights reserved.

Hydroxychavicol, a betel leaf component, inhibits prostate cancer through ROS-driven DNA damage and apoptosis

PubMed Central

Gundala, Sushma Reddy; Yang, Chunhua; Mukkavilli, Rao; Paranjpe, Rutugandha; Brahmbhatt, Meera; Pannu, Vaishali; Cheng, Alice; Reid, Michelle D.; Aneja, Ritu

2015-01-01

Dietary phytochemicals are excellent ROS-modulating agents and have been shown to effectively enhance ROS levels beyond toxic threshold in cancer cells to ensure their selective killing while leaving normal cells unscathed. Here we demonstrate that hydroxychavicol (HC), extracted and purified from Piper betel leaves, significantly inhibits growth and proliferation via ROS generation in human prostate cancer, PC-3 cells. HC perturbed cell-cycle kinetics and progression, reduced clonogenicity and mediated cytotoxicity by ROS-induced DNA damage leading to activation of several pro-apoptotic molecules. In addition, HC treatment elicited a novel autophagic response as evidenced by the appearance of acidic vesicular organelles and increased expression of autophagic markers, LC3-IIb and beclin-1. Interestingly, quenching of ROS with tiron, an antioxidant, offered significant protection against HC-induced inhibition of cell growth and down regulation of caspase-3, suggesting the crucial role of ROS in mediating cell death. The collapse of mitochondrial transmembrane potential by HC further revealed the link between ROS generation and induction of caspase-mediated apoptosis in PC-3 cells. Our data showed remarkable inhibition of prostate tumor xenografts by ~72% upon daily oral administration of 150 mg/kg bw HC by quantitative tumor volume measurements and non-invasive real-time bioluminescent imaging. HC was well-tolerated at this dosing level without any observable toxicity. This is the first report to demonstrate the anti-prostate efficacy of HC in vitro and in vivo, which is perhaps attributable to its selective prooxidant activity to eliminate cancer cells thus providing compelling grounds for future preclinical studies to validate its potential usefulness for prostate cancer management. PMID:25064160

Peroxiredoxin 2 regulates PGF2α-induced corpus luteum regression in mice by inhibiting ROS-dependent JNK activation.

PubMed

Park, Sun-Ji; Kim, Jung-Hak; Kim, Tae-Shin; Lee, Sang-Rae; Park, Jeen-Woo; Lee, Seunghoon; Kim, Jin-Man; Lee, Dong-Seok

2017-07-01

Luteal regression is a natural and necessary event to regulate the reproductive process in all mammals. Prostaglandin F2α (PGF2α) is the main factor that causes functional and structural regression of the corpus luteum (CL). It is well known that PGF2α-mediated ROS generation is closely involved in luteal regression. Peroxiredoxin 2 (Prx2) as an antioxidant enzyme plays a protective role against oxidative stress-induced cell death. However, the effect of Prx2 on PGF2α-induced luteal regression has not been reported. Here, we investigated the role of Prx2 in functional and structural CL regression induced by PGF2α-mediated ROS using Prx2-deficient (-/-) mice. We found that PGF2α-induced ROS generation was significantly higher in Prx2-/- MEF cells compared with that in wild-type (WT) cells, which induced apoptosis by activating JNK-mediated apoptotic signaling pathway. Also, PGF2α treatment in the CL derived from Prx2-/- mice promoted the reduction of steroidogenic enzyme expression and the activation of JNK and caspase3. Compared to WT mice, serum progesterone levels and luteal expression of steroidogenic enzymes decreased more rapidly whereas JNK and caspase3 activations were significantly increased in Prx2-/- mice injected with PGF2α. However, the impaired steroidogenesis and PGF2α-induced JNK-dependent apoptosis were rescued by the addition of the antioxidant N-acetyl-L-cysteine (NAC). This is the first study to demonstrate that Prx2 deficiency ultimately accelerated the PGF2α-induced luteal regression through activation of the ROS-dependent JNK pathway. These findings suggest that Prx2 plays a crucial role in preventing accelerated luteal regression via inhibition of the ROS/JNK pathway. Copyright © 2017 Elsevier Inc. All rights reserved.

Mitochondrial reactive oxygen species regulate the strength of inhibitory GABA-mediated synaptic transmission

NASA Astrophysics Data System (ADS)

Accardi, Michael V.; Daniels, Bryan A.; Brown, Patricia M. G. E.; Fritschy, Jean-Marc; Tyagarajan, Shiva K.; Bowie, Derek

2014-01-01

Neuronal communication imposes a heavy metabolic burden in maintaining ionic gradients essential for action potential firing and synaptic signalling. Although cellular metabolism is known to regulate excitatory neurotransmission, it is still unclear whether the brain’s energy supply affects inhibitory signalling. Here we show that mitochondrial-derived reactive oxygen species (mROS) regulate the strength of postsynaptic GABAA receptors at inhibitory synapses of cerebellar stellate cells. Inhibition is strengthened through a mechanism that selectively recruits α3-containing GABAA receptors into synapses with no discernible effect on resident α1-containing receptors. Since mROS promotes the emergence of postsynaptic events with unique kinetic properties, we conclude that newly recruited α3-containing GABAA receptors are activated by neurotransmitter released onto discrete postsynaptic sites. Although traditionally associated with oxidative stress in neurodegenerative disease, our data identify mROS as a putative homeostatic signalling molecule coupling cellular metabolism to the strength of inhibitory transmission.

Gene expression patterns regulating the seed metabolism in relation to deterioration/ageing of primed mung bean (Vigna radiata L.) seeds.

PubMed

Sharma, Satyendra Nath; Maheshwari, Ankita; Sharma, Chitra; Shukla, Nidhi

2018-03-01

We are proposing mechanisms to account for the loss of viability (seed deterioration/ageing) and enhancement in seed quality (post-storage priming treatment). In order to understand the regulatory mechanism of these traits, we conducted controlled deterioration (CD) test for up to 8 d using primed mung bean seeds and examined how CD effects the expression of many genes, regulating the seed metabolism in relation to CD and priming. Germination declined progressively with increased duration of CD, and the priming treatment completely/partially reversed the inhibition depending on the duration of CD. The loss of germination capacity by CD was accompanied by a reduction in total RNA content and RNA integrity, indicating that RNA quantity and quality impacts seed longevity. Expression analysis revealed that biosynthesis genes of GA, ethylene, ABA and ROS-scavenging enzymes were differentially affected in response to duration of CD and priming, suggesting coordinately regulated mechanisms for controlling the germination capacity of seeds by modifying the permeability characteristics of biological membranes and activities of different enzymes. ABA genes were highly expressed when germination was delayed and inhibited by CD. Whereas, GA and ethylene genes were more highly expressed when germination was enhanced and permitted by priming under similar conditions. GSTI, a well characterized enzyme family involved in stress tolerance, was expressed in primed seeds over the period of CD, suggesting an additional protection against deterioration. The results are discussed in light of understanding the mechanisms underlying longevity/priming which are important issues economically and ecologically. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Free radicals mediate systemic acquired resistance.

PubMed

Wang, Caixia; El-Shetehy, Mohamed; Shine, M B; Yu, Keshun; Navarre, Duroy; Wendehenne, David; Kachroo, Aardra; Kachroo, Pradeep

2014-04-24

Systemic acquired resistance (SAR) is a form of resistance that protects plants against a broad spectrum of secondary infections. However, exploiting SAR for the protection of agriculturally important plants warrants a thorough investigation of the mutual interrelationships among the various signals that mediate SAR. Here, we show that nitric oxide (NO) and reactive oxygen species (ROS) serve as inducers of SAR in a concentration-dependent manner. Thus, genetic mutations that either inhibit NO/ROS production or increase NO accumulation (e.g., a mutation in S-nitrosoglutathione reductase [GSNOR]) abrogate SAR. Different ROS function additively to generate the fatty-acid-derived azelaic acid (AzA), which in turn induces production of the SAR inducer glycerol-3-phosphate (G3P). Notably, this NO/ROS→AzA→G3P-induced signaling functions in parallel with salicylic acid-derived signaling. We propose that the parallel operation of NO/ROS and SA pathways facilitates coordinated regulation in order to ensure optimal induction of SAR. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Negative Regulation of Abscisic Acid Signaling by the Fagus sylvatica FsPP2C1 Plays A Role in Seed Dormancy Regulation and Promotion of Seed Germination1

PubMed Central

González-García, Mary Paz; Rodríguez, Dolores; Nicolás, Carlos; Rodríguez, Pedro Luis; Nicolás, Gregorio; Lorenzo, Oscar

2003-01-01

FsPP2C1 was previously isolated from beech (Fagus sylvatica) seeds as a functional protein phosphatase type-2C (PP2C) with all the conserved features of these enzymes and high homology to ABI1, ABI2, and PP2CA, PP2Cs identified as negative regulators of ABA signaling. The expression of FsPP2C1 was induced upon abscisic acid (ABA) treatment and was also up-regulated during early weeks of stratification. Furthermore, this gene was specifically expressed in ABA-treated seeds and was hardly detectable in vegetative tissues. In this report, to provide genetic evidence on FsPP2C1 function in seed dormancy and germination, we used an overexpression approach in Arabidopsis because transgenic work is not feasible in beech. Constitutive expression of FsPP2C1 under the cauliflower mosaic virus 35S promoter confers ABA insensitivity in Arabidopsis seeds and, consequently, a reduced degree of seed dormancy. Additionally, transgenic 35S:FsPP2C1 plants are able to germinate under unfavorable conditions, as inhibitory concentrations of mannitol, NaCl, or paclobutrazol. In vegetative tissues, Arabidopsis FsPP2C1 transgenic plants show ABA-resistant early root growth and diminished induction of the ABA-response genes RAB18 and KIN2, but no effect on stomatal closure regulation. Seed and vegetative phenotypes of Arabidopsis 35S:FsPP2C1 plants suggest that FsPP2C1 negatively regulates ABA signaling. The ABA inducibility of FsPP2C1 expression, together with the transcript accumulation mainly in seeds, suggest that it could play an important role modulating ABA signaling in beechnuts through a negative feedback loop. Finally, we suggest that negative regulation of ABA signaling by FsPP2C1 is a factor contributing to promote the transition from seed dormancy to germination during early weeks of stratification. PMID:12970481

Temperature Variation under Continuous Light Restores Tomato Leaf Photosynthesis and Maintains the Diurnal Pattern in Stomatal Conductance

PubMed Central

Haque, Mohammad S.; de Sousa, Alexandra; Soares, Cristiano; Kjaer, Katrine H.; Fidalgo, Fernanda; Rosenqvist, Eva; Ottosen, Carl-Otto

2017-01-01

The response of tomato plants (Solanum lycopersicum L. cv. Aromata) to continuous light (CL) in relation to photosynthesis, abscisic acid (ABA) and reactive oxygen species (ROS) was investigated to improve the understanding of the development and/or alleviation of CL-induced leaf injury in constant and diurnal temperature fluctuations with similar daily light integral and daily mean temperature. The plants were grown in three photoperiodic treatments for 15 days; One treatment with a 16/8 h light/dark period and a light/dark temperature of 27/17°C (Control), two CL treatments with 24 h photoperiods, one with a constant temperature of 24°C (CLCT) and the other one with variable temperature of 27/17°C for 16/8 ho, respectively (CLVT). A diurnal pattern of stomatal conductance (gs) and [ABA] was observed in the plants grown in the control and CLVT conditions, while the plants in CLCT conditions experienced a significant decrease in stomatal conductance aligned with an increase in ABA. The net photosynthesis (A) was significantly reduced in CLCT, aligned with a significant decrease in the maximum rate of Rubisco carboxylation (Vcmax), the maximum rate of electron transport (Jmax) and mesophyll diffusion conductance to CO2 (gm) in comparison to the control and CLVT. An increased production of H2O2 and O2•- linked with increased activities of antioxidative enzymes was seen in both CL treatments, but despite of this, leaf injuries were only observed in the CLCT treatment. The results suggest that the diurnal temperature fluctuations alleviated the CL injury symptoms, probably because the diurnal cycles of cellular mechanisms were maintained. The ROS were shown not to be directly involved in CL-induced leaf injury, since both ROS production and scavenging was highest in CLVT without leaf chlorotic symptoms. PMID:28979273

Silibinin induces mitochondrial NOX4-mediated endoplasmic reticulum stress response and its subsequent apoptosis.

PubMed

Kim, Sang-Hun; Kim, Kwang-Youn; Yu, Sun-Nyoung; Seo, Young-Kyo; Chun, Sung-Sik; Yu, Hak-Sun; Ahn, Soon-Cheol

2016-07-12

Silibinin, a biologically active compound of milk thistle, has chemopreventive effects on cancer cell lines. Recently it was reported that silibinin inhibited tumor growth through activation of the apoptotic signaling pathway. Although various evidences showed multiple signaling pathways of silibinin in apoptosis, there were no reports to address the clear mechanism of ROS-mediated pathway in prostate cancer PC-3 cells. Several studies suggested that reactive oxygen species (ROS) play an important role in various signaling cascades, but the primary source of ROS was currently unclear. The effect of silibinin was investigated on cell growth of prostate cell lines by MTT assay. We examined whether silibinin induced apoptosis through production of ROS using flow cytometry. Expression of apoptosis-, endoplasmic reticulum (ER)-related protein and gene were determined by western blotting and RT-PCR, respectively. Results showed that silibinin triggered mitochondrial ROS production through NOX4 expression and finally led to induce apoptosis. In addition, mitochondrial ROS caused ER stress through disruption of Ca(2+) homeostasis. Co-treatment of ROS inhibitor reduced the silibinin-induced apoptosis through the inhibition of NOX4 expression, resulting in reduction of both Ca(2+) level and ER stress response. Taken together, silibinin induced mitochondrial ROS-dependent apoptosis through NOX4, which is associated with disruption of Ca(2+) homeostasis and ER stress response. Therefore, the regulation of NOX4, mitochondrial ROS producer, could be a potential target for the treatment of prostate cancer.

A central role for oxygen-sensitive K+ channels and mitochondria in the specialized oxygen-sensing system.

PubMed

Archer, Stephen L; Michelakis, Evangelos D; Thébaud, Bernard; Bonnet, Sebastien; Moudgil, Rohit; Wu, Xi-Chen; Weir, E Kenneth

2006-01-01

Mammals possess a specialized O2-sensing system (SOS), which compensates for encounters with hypoxia that occur during development, disease, and at altitude. Consisting of the resistance pulmonary arteries (PA), ductus arteriosus, carotid body, neuroepithelial body, systemic arteries, fetal adrenomedullary cell and fetoplacental arteries, the SOS optimizes O2-uptake and delivery. Hypoxic pulmonary vasoconstriction (HPV), a vasomotor response of resistance PAs to alveolar hypoxia, optimizes ventilation/perfusion matching and systemic pO2. Though modulated by the endothelium, HPV's core mechanism resides in the smooth muscle cell (SMC). The Redox Theory proposes that HPV results from the coordinated action of a redox sensor (proximal mitochondrial electron transport chain) which generates a diffusible mediator (a reactive O2 species, ROS) that regulates effector proteins (voltage-gated K(v) channels). Hypoxic withdrawal of ROS inhibits K(v)1.5 and K(v)2.1, depolarizes PASMCs, activates voltage-gated Ca2+ channels, increasing Ca2+ influx and causing vasoconstriction. Hypoxia's effect on ROS (decrease vs. increase) and the molecular origins of ROS (mitochondria vs. NADPH oxidase) remains controversial. Distal to this pathway, Rho kinase regulates the contractile apparatus' sensitivity to Ca2+. Also, a role for cADP ribose as a redox-regulated mediator of intracellular Ca2+ release has been proposed. Despite tissue heterogeneity in the SOS's output (vasomotion versus neurosecretion), O2-sensitive K+ channels constitute a conserved effector mechanism. Disorders of the O2-sensing may contribute to diseases, such as pulmonary hypertension.

Abscisic acid (ABA) is involved in phenolic compounds biosynthesis, mainly anthocyanins, in leaves of Aristotelia chilensis plants (Mol.) subjected to drought stress.

PubMed

González-Villagra, Jorge; Cohen, Jerry D; Reyes-Díaz, Marjorie M

2018-06-20

Abscisic acid (ABA) regulates the physiological and biochemical mechanisms required to tolerate drought stress, which is considered as an important abiotic stress. It has been postulated that ABA might be involved in regulation of plant phenolic compounds biosynthesis, especially anthocyanins that accumulate in plants subjected to drought stress; however, the evidence for this postulate remains elusive. Therefore, we studied whether ABA is involved in phenolic compounds accumulation, especially anthocyanin biosynthesis, using drought stressed Aristotelia chilensis plants, an endemic berry in Chile. Our approach was to use fluridone, an ABA biosynthesis inhibitor, and then subsequent ABA applications to young and fully-expanded leaves of drought stressed A. chilensis plants during 24, 48 and 72 h of the experiment. Plants were harvested and leaves were collected separately to determine the biochemical status. We observed that fluridone treatments significantly decreased ABA concentrations and total anthocyanin (TA) concentrations in stressed plants, including both young and fully-expanded leaves. TA concentrations following fluridone treatment were reduced around 5-fold, reaching control plant levels. ABA application restored ABA levels as well as TA concentrations in stressed plant at the 48 h of the experiment. We also observed that TA concentrations followed the same pattern as ABA concentrations in the ABA treated plants. qRT-PCR revealed that AcUFGT gene expression decreased in fully-expanded leaves of stressed plants treated with fluridone, while a subsequent ABA application increased AcUFGT expression. Taken together, our results suggest that ABA is involved in the regulation of anthocyanin biosynthesis under drought stress. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Hypericin-mediated sonodynamic therapy induces autophagy and decreases lipids in THP-1 macrophage by promoting ROS-dependent nuclear translocation of TFEB.

PubMed

Li, Xuesong; Zhang, Xin; Zheng, Longbin; Kou, Jiayuan; Zhong, Zhaoyu; Jiang, Yueqing; Wang, Wei; Dong, Zengxiang; Liu, Zhongni; Han, Xiaobo; Li, Jing; Tian, Ye; Zhao, Yajun; Yang, Liming

2016-12-22

Lipid catabolism disorder is the primary cause of atherosclerosis. Transcription factor EB (TFEB) prevents atherosclerosis by activating macrophage autophagy to promote lipid degradation. Hypericin-mediated sonodynamic therapy (HY-SDT) has been proved non-invasively inducing THP-1-derived macrophage apoptosis; however, it is unknown whether macrophage autophagy could be triggered by HY-SDT to influence cellular lipid catabolism via regulating TFEB. Here, we report that HY-SDT resulted in the time-dependent THP-1-derived macrophage autophagy activation through AMPK/AKT/mTOR pathway. Besides, TFEB nuclear translocation in macrophage was triggered by HY-SDT to promote autophagy activation and lysosome regeneration which enhanced lipid degradation in response to atherogenic lipid stressors. Moreover, following HY-SDT, the ABCA1 expression level was increased to promote lipid efflux in macrophage, and the expression levels of CD36 and SR-A were decreased to inhibit lipid uptake, both of which were prevented by TFEB knockdown. These results indicated that TFEB nuclear translocation activated by HY-SDT was not only the key regulator of autophagy activation and lysosome regeneration in macrophage to promote lipolysis, but also had a crucial role in reverse cholesterol transporters to decrease lipid uptake and increase lipid efflux. Reactive oxygen species (ROS) were adequately generated in macrophage by HY-SDT. Further, ROS scavenger N-acetyl-l-cysteine abolished HY-SDT-induced TFEB nuclear translocation and autophagy activation, implying that ROS were the primary upstream factors responsible for these effects during HY-SDT. In summary, our data indicate that HY-SDT decreases lipid content in macrophage by promoting ROS-dependent nuclear translocation of TFEB to influence consequent autophagy activation and cholesterol transporters. Thus, HY-SDT may be beneficial for atherosclerosis via TFEB regulation to ameliorate lipid overload in atherosclerotic plaques.

Hydroxyl radical mediates cisplatin-induced apoptosis in human hair follicle dermal papilla cells and keratinocytes through Bcl-2-dependent mechanism.

PubMed

Luanpitpong, Sudjit; Nimmannit, Ubonthip; Chanvorachote, Pithi; Leonard, Stephen S; Pongrakhananon, Varisa; Wang, Liying; Rojanasakul, Yon

2011-08-01

Induction of massive apoptosis of hair follicle cells by chemotherapy has been implicated in the pathogenesis of chemotherapy-induced alopecia (CIA), but the underlying mechanisms of regulation are not well understood. The present study investigated the apoptotic effect of cisplatin in human hair follicle dermal papilla cells and HaCaT keratinocytes, and determined the identity and role of specific reactive oxygen species (ROS) involved in the process. Treatment of the cells with cisplatin induced ROS generation and a parallel increase in caspase activation and apoptotic cell death. Inhibition of ROS generation by antioxidants inhibited the apoptotic effect of cisplatin, indicating the role of ROS in the process. Studies using specific ROS scavengers further showed that hydroxyl radical, but not hydrogen peroxide or superoxide anion, is the primary oxidative species responsible for the apoptotic effect of cisplatin. Electron spin resonance studies confirmed the formation of hydroxyl radicals induced by cisplatin. The mechanism by which hydroxyl radical mediates the apoptotic effect of cisplatin was shown to involve down-regulation of the anti-apoptotic protein Bcl-2 through ubiquitin-proteasomal degradation. Bcl-2 was also shown to have a negative regulatory role on hydroxyl radical. Together, our results indicate an essential role of hydroxyl radical in cisplatin-induced cell death of hair follicle cells through Bcl-2 regulation. Since CIA is a major side effect of cisplatin and many other chemotherapeutic agents with no known effective treatments, the knowledge gained from this study could be useful in the design of preventive treatment strategies for CIA through localized therapy without compromising the chemotherapy efficacy.

The endogenous plant hormones and ratios regulate sugar and dry matter accumulation in Jerusalem artichoke in salt-soil.

PubMed

Li, Lingling; Shao, Tianyun; Yang, Hui; Chen, Manxia; Gao, Xiumei; Long, Xiaohua; Shao, Hongbo; Liu, Zhaopu; Rengel, Zed

2017-02-01

The changes in content of endogenous hormones in stolons and tubers of Jerusalem artichoke (Helianthus tuberosus L.) regulate tuber growth, but the specific knowledge about the importance of balance among the endogenous hormones is lacking. Two varieties of Jerusalem artichoke (NY-1 and QY-2) were tested for the endogenous zeatin (ZT), auxins (IAA), gibberellins (GA 3 ) and abscisic acid (ABA) in regulating sugar and dry matter accumulation in tubers. The dry matter content and sugar accumulation in tubers were correlated positively with endogenous ZT and negatively with GA 3 content and GA 3 /ABA and IAA/ABA content ratios. Throughout the tuber formation, ZT content was higher in NY-1 than QY-2 tubers, whereas ABA content was higher in QY-2 than NY-1 tubers. The content ratios GA 3 /ABA and IAA/ABA were greater in NY-1 than QY-2 before tuber initiation, but QY-2 surpassed NY-1 during the tuber growth stage. The GA 3 /ABA and IAA/ABA content ratios declined during tuber growth. The results suggested that a dynamic balance of endogenous hormones played an important role in tuber development. Copyright © 2016 Elsevier B.V. All rights reserved.

Identification, cloning and characterization of R2R3-MYB gene family in canola (Brassica napus L.) identify a novel member modulating ROS accumulation and hypersensitive-like cell death

PubMed Central

Chen, Bisi; Niu, Fangfang; Liu, Wu-Zhen; Yang, Bo; Zhang, Jingxiao; Ma, Jieyu; Cheng, Hao; Han, Feng; Jiang, Yuan-Qing

2016-01-01

The R2R3-MYB proteins comprise one of the largest families of transcription factors in plants. Although genome-wide analysis of this family has been carried out in some plant species, little is known about R2R3-MYB genes in canola (Brassica napus L.). In this study, we have identified 76 R2R3-MYB genes in the canola genome through mining of expressed sequence tags (ESTs). The cDNA sequences of 44 MYB genes were successfully cloned. The transcriptional activities of BnaMYB proteins encoded by these genes were assayed in yeast. The subcellular localizations of representative R2R3-MYB proteins were investigated through GFP fusion. Besides, the transcript abundance level analysis during abiotic conditions and ABA treatment identified a group of R2R3-MYB genes that responded to one or more treatments. Furthermore, we identified a previously functionally unknown MYB gene-BnaMYB78, which modulates reactive oxygen species (ROS)-dependent cell death in Nicotiana benthamiana, through regulating the transcription of a few ROS- and defence-related genes. Taken together, this study has provided a solid foundation for understanding the roles and regulatory mechanism of canola R2R3-MYB genes. PMID:26800702

Endodermal ABA Signaling Promotes Lateral Root Quiescence during Salt Stress in Arabidopsis Seedlings[C][W

PubMed Central

Duan, Lina; Dietrich, Daniela; Ng, Chong Han; Chan, Penny Mei Yeen; Bhalerao, Rishikesh; Bennett, Malcolm J.; Dinneny, José R.

2013-01-01

The endodermal tissue layer is found in the roots of vascular plants and functions as a semipermeable barrier, regulating the transport of solutes from the soil into the vascular stream. As a gateway for solutes, the endodermis may also serve as an important site for sensing and responding to useful or toxic substances in the environment. Here, we show that high salinity, an environmental stress widely impacting agricultural land, regulates growth of the seedling root system through a signaling network operating primarily in the endodermis. We report that salt stress induces an extended quiescent phase in postemergence lateral roots (LRs) whereby the rate of growth is suppressed for several days before recovery begins. Quiescence is correlated with sustained abscisic acid (ABA) response in LRs and is dependent upon genes necessary for ABA biosynthesis, signaling, and transcriptional regulation. We use a tissue-specific strategy to identify the key cell layers where ABA signaling acts to regulate growth. In the endodermis, misexpression of the ABA insensitive1-1 mutant protein, which dominantly inhibits ABA signaling, leads to a substantial recovery in LR growth under salt stress conditions. Gibberellic acid signaling, which antagonizes the ABA pathway, also acts primarily in the endodermis, and we define the crosstalk between these two hormones. Our results identify the endodermis as a gateway with an ABA-dependent guard, which prevents root growth into saline environments. PMID:23341337

Mapping of oxidative stress response elements of the caveolin-1 promoter.

PubMed

Bartholomew, Janine N; Galbiati, Ferruccio

2010-01-01

According to the "free radical theory" of aging, normal aging occurs as the result of tissue damages inflicted by reactive oxygen species (ROS). ROS are known to induce cellular senescence, and senescent cells are believed to contribute to organismal aging. The molecular mechanisms that mediate the cellular response to oxidants remain to be fully identified. We have shown that oxidative stress induces cellular senescence through activation of the caveolin-1 promoter and upregulation of caveolin-1 protein expression. Here, we describe how reactive oxygen species activate the caveolin-1 promoter and how the signaling may be assayed. These approaches provide insight into the functional role of caveolin-1 and potentially allow the identification of novel ROS-regulated genes that are part of the signaling machinery regulating cellular senescence/aging.

NADPH oxidase/ROS-dependent PYK2 activation is involved in TNF-α-induced matrix metalloproteinase-9 expression in rat heart-derived H9c2 cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Chuen-Mao, E-mail: chuenmao@mail.cgu.edu.tw; Heart Failure Center, Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital at Keelung, Keelung, Taiwan; Lee, I-Ta

TNF-α plays a mediator role in the pathogenesis of chronic heart failure contributing to cardiac remodeling and peripheral vascular disturbances. The implication of TNF-α in inflammatory responses has been shown to be mediated through up-regulation of matrix metalloproteinase-9 (MMP-9). However, the detailed mechanisms of TNF-α-induced MMP-9 expression in rat embryonic-heart derived H9c2 cells are largely not defined. We demonstrated that in H9c2 cells, TNF-α induced MMP-9 mRNA and protein expression associated with an increase in the secretion of pro-MMP-9. TNF-α-mediated responses were attenuated by pretreatment with the inhibitor of ROS (N-acetyl-L-cysteine, NAC), NADPH oxidase [apocynin (APO) or diphenyleneiodonium chloride (DPI)],more » MEK1/2 (U0126), p38 MAPK (SB202190), JNK1/2 (SP600125), NF-κB (Bay11-7082), or PYK2 (PF-431396) and transfection with siRNA of TNFR1, p47{sup phox}, p42, p38, JNK1, p65, or PYK2. Moreover, TNF-α markedly induced NADPH oxidase-derived ROS generation in these cells. TNF-α-enhanced p42/p44 MAPK, p38 MAPK, JNK1/2, and NF-κB (p65) phosphorylation and in vivo binding of p65 to the MMP-9 promoter were inhibited by U0126, SB202190, SP600125, NAC, DPI, or APO. In addition, TNF-α-mediated PYK2 phosphorylation was inhibited by NAC, DPI, or APO. PYK2 inhibition could reduce TNF-α-stimulated MAPKs and NF-κB activation. Thus, in H9c2 cells, we are the first to show that TNF-α-induced MMP-9 expression is mediated through a TNFR1/NADPH oxidase/ROS/PYK2/MAPKs/NF-κB cascade. We demonstrated that NADPH oxidase-derived ROS generation is involved in TNF-α-induced PYK2 activation in these cells. Understanding the regulation of MMP-9 expression and NADPH oxidase activation by TNF-α on H9c2 cells may provide potential therapeutic targets of chronic heart failure. - Highlights: • TNF-α induces MMP-9 secretion and expression via a TNFR1-dependent pathway. • TNF-α induces ROS/PYK2-dependent MMP-9 expression in H9c2 cells. • TNF-α induces MMP-9 expression via a NADPH oxidase/ROS-dependent NF-κB signaling. • TNF-α activates MAPK phosphorylation through NADPH oxidase/ROS generation.« less

Reactive Oxygen Species (ROS): Beneficial Companions of Plants’ Developmental Processes

PubMed Central

Singh, Rachana; Singh, Samiksha; Parihar, Parul; Mishra, Rohit K.; Tripathi, Durgesh K.; Singh, Vijay P.; Chauhan, Devendra K.; Prasad, Sheo M.

2016-01-01

Reactive oxygen species (ROS) are generated inevitably in the redox reactions of plants, including respiration and photosynthesis. In earlier studies, ROS were considered as toxic by-products of aerobic pathways of the metabolism. But in recent years, concept about ROS has changed because they also participate in developmental processes of plants by acting as signaling molecules. In plants, ROS regulate many developmental processes such as cell proliferation and differentiation, programmed cell death, seed germination, gravitropism, root hair growth and pollen tube development, senescence, etc. Despite much progress, a comprehensive update of advances in the understanding of the mechanisms evoked by ROS that mediate in cell proliferation and development are fragmentry and the matter of ROS perception and the signaling cascade remains open. Therefore, keeping in view the above facts, an attempt has been made in this article to summarize the recent findings regarding updates made in the regulatory action of ROS at various plant developmental stages, which are still not well-known. PMID:27729914

The TrkAIII oncoprotein inhibits mitochondrial free radical ROS-induced death of SH-SY5Y neuroblastoma cells by augmenting SOD2 expression and activity at the mitochondria, within the context of a tumour stem cell-like phenotype.

PubMed

Ruggeri, Pierdomenico; Farina, Antonietta R; Di Ianni, Natalia; Cappabianca, Lucia; Ragone, Marzia; Ianni, Giulia; Gulino, Alberto; Mackay, Andrew R

2014-01-01

The developmental and stress-regulated alternative TrkAIII splice variant of the NGF receptor TrkA is expressed by advanced stage human neuroblastomas (NBs), correlates with worse outcome in high TrkA expressing unfavourable tumours and exhibits oncogenic activity in NB models. In the present study, we report that constitutive TrkAIII expression in human SH-SY5Y NB cells inhibits Rotenone, Paraquat and LY83583-induced mitochondrial free radical reactive oxygen species (ROS)-mediated death by stimulating SOD2 expression, increasing mitochondrial SOD2 activity and attenuating mitochondrial free radical ROS production, in association with increased mitochondrial capacity to produce H2O2, within the context of a more tumour stem cell-like phenotype. This effect can be reversed by the specific TrkA tyrosine kinase inhibitor GW441756, by the multi-kinase TrkA inhibitors K252a, CEP-701 and Gö6976, which inhibit SOD2 expression, and by siRNA knockdown of SOD2 expression, which restores the sensitivity of TrkAIII expressing SH-SY5Y cells to Rotenone, Paraquat and LY83583-induced mitochondrial free radical ROS production and ROS-mediated death. The data implicate the novel TrkAIII/SOD2 axis in promoting NB resistance to mitochondrial free radical-mediated death and staminality, and suggest that the combined use of TrkAIII and/or SOD2 inhibitors together with agents that induce mitochondrial free radical ROS-mediated death could provide a therapeutic advantage that may also target the stem cell niche in high TrkA expressing unfavourable NB.

The TrkAIII Oncoprotein Inhibits Mitochondrial Free Radical ROS-Induced Death of SH-SY5Y Neuroblastoma Cells by Augmenting SOD2 Expression and Activity at the Mitochondria, within the Context of a Tumour Stem Cell-like Phenotype

PubMed Central

Di Ianni, Natalia; Cappabianca, Lucia; Ragone, Marzia; Ianni, Giulia; Gulino, Alberto; Mackay, Andrew R.

2014-01-01

The developmental and stress-regulated alternative TrkAIII splice variant of the NGF receptor TrkA is expressed by advanced stage human neuroblastomas (NBs), correlates with worse outcome in high TrkA expressing unfavourable tumours and exhibits oncogenic activity in NB models. In the present study, we report that constitutive TrkAIII expression in human SH-SY5Y NB cells inhibits Rotenone, Paraquat and LY83583-induced mitochondrial free radical reactive oxygen species (ROS)-mediated death by stimulating SOD2 expression, increasing mitochondrial SOD2 activity and attenuating mitochondrial free radical ROS production, in association with increased mitochondrial capacity to produce H2O2, within the context of a more tumour stem cell-like phenotype. This effect can be reversed by the specific TrkA tyrosine kinase inhibitor GW441756, by the multi-kinase TrkA inhibitors K252a, CEP-701 and Gö6976, which inhibit SOD2 expression, and by siRNA knockdown of SOD2 expression, which restores the sensitivity of TrkAIII expressing SH-SY5Y cells to Rotenone, Paraquat and LY83583-induced mitochondrial free radical ROS production and ROS-mediated death. The data implicate the novel TrkAIII/SOD2 axis in promoting NB resistance to mitochondrial free radical-mediated death and staminality, and suggest that the combined use of TrkAIII and/or SOD2 inhibitors together with agents that induce mitochondrial free radical ROS-mediated death could provide a therapeutic advantage that may also target the stem cell niche in high TrkA expressing unfavourable NB. PMID:24736663

Transcriptome of the floral transition in Rosa chinensis 'Old Blush'.

PubMed

Guo, Xuelian; Yu, Chao; Luo, Le; Wan, Huihua; Zhen, Ni; Xu, Tingliang; Tan, Jiongrui; Pan, Huitang; Zhang, Qixiang

2017-02-23

The floral transition plays a vital role in the life of ornamental plants. Despite progress in model plants, the molecular mechanisms of flowering regulation remain unknown in perennial plants. Rosa chinensis 'Old Blush' is a unique plant that can flower continuously year-round. In this study, gene expression profiles associated with the flowering transition were comprehensively analyzed during floral transition in the rose. According to the transcriptomic profiles, 85,663 unigenes and 1,637 differentially expressed genes (DEGs) were identified, among which 32 unigenes were involved in the circadian clock, sugar metabolism, hormone, and autonomous pathways. A hypothetical model for the regulation of floral transition was proposed in which the candidate genes function synergistically the floral transition process. Hormone contents and biosynthesis and metabolism genes fluctuated during the rose floral transition process. Gibberellins (GAs) inhibited rose floral transition, the content of GAs gradually decreased and GA2ox and SCL13 were upregulated from vegetative (VM) meristem to floral meristem (FM). Auxin plays an affirmative part in mediating floral transition, auxin content and auxin-related gene expression levels were gradually upregulated during the floral transition of the rose. However, ABA content and ABA signal genes were gradually downregulated, suggesting that ABA passively regulates the rose floral transition by participating in sugar signaling. Furthermore, sugar content and sugar metabolism genes increased during floral transition in the rose, which may be a further florigenic signal that activates floral transition. Additionally, FRI, FY, DRM1, ELIP, COP1, CO, and COL16 are involved in the circadian clock and autonomous pathway, respectively, and they play a positively activating role in regulating floral transition. Overall, physiological changes associated with genes involved in the circadian clock or autonomous pathway collectively regulated the rose floral transition. Our results summarize a valuable collective of gene expression profiles characterizing the rose floral transition. The DEGs are candidates for functional analyses of genes affecting the floral transition in the rose, which is a precious resource that reveals the molecular mechanism of mediating floral transition in other perennial plants.

Duox2-induced innate immune responses in the respiratory epithelium and intranasal delivery of Duox2 DNA using polymer that mediates immunization.

PubMed

Jeon, Yung Jin; Kim, Hyun Jik

2018-05-01

Respiratory mucosa especially nasal epithelium is well known as the first-line barrier of air-borne pathogens. High levels of reactive oxygen species (ROS) are detected in in vitro cultured human epithelial cells and in vivo lung. With identification of NADPH oxidase (Nox) system of respiratory epithelium, the antimicrobial role of ROS has been studied. Duox2 is the most abundant Nox isoform and produces the regulated amount of ROS in respiratory epithelium. Duox2-derived ROS are involved in antiviral innate immune responses but more studies are needed to verify the mechanism. In respiratory epithelium, Duox2-derived ROS is critical for recognition of virus through families retinoic acid-inducible gene-I (RIG-I) and melanoma differentiation-associated protein 5 (MDA5) at the early stage of antiviral innate immune responses. Various secreted interferons (IFNs) play essential roles for antiviral host defense by downstream cell signaling, and transcription of IFN-stimulated genes is started to suppress viral replication. Type I and type III IFNs are verified more responsible for influenza A virus (IAV) infection in respiratory epithelium and Duox2 is required to regulate IFN-related immune responses. Transient overexpression of Duox2 using cationic polymer polyethylenimine (PEI) induces secretion of type I and type III IFNs and significantly attenuated IAV replication in respiratory epithelium. Here, we discuss Duox2-mediated antiviral innate immune responses and the role of Duox2 as a mucosal vaccine to resist respiratory viral infection.

Effects of abscisic acid and xanthoxin on elongation and gravitropism in primary roots of Zea mays

NASA Technical Reports Server (NTRS)

Lee, J. S.; Hasenstein, K. H.; Mulkey, T. J.; Yang, R. L.; Evans, M. L.

1990-01-01

We examined the involvement of abscisic acid (ABA) and xanthoxin (Xan) in maize root gravitropism by (1) testing the ability of ABA to allow positive gravitropism in dark-grown seedlings of the maize cultivar LG11, a cultivar known to require light for positive gravitropism of the primary root, (2) comparing curvature in roots in which half of the cap had been excised and replaced with agar containing either ABA or indole-3-acetic acid (IAA), (3) measuring gravitropism in roots of seedlings submerged in oxygenated solutions of ABA or IAA and (4) testing the effect of Xan on root elongation. Using a variety of methods of applying ABA to the root, we found that ABA did not cause horizontally-oriented primary roots of dark-grown seedlings to become positively gravitropic. Replacing half of the root cap of vertically oriented roots with an agar block containing ABA had little or no effect on curvature relative to that of controls in which the half cap was replaced by a plain agar block. Replacement of the removed half cap with IAA either canceled or reversed the curvature displayed by controls. When light-grown seedlings were submerged in ABA they responded strongly to gravistimulation while those in IAA did not. Xan (up to 0.1 mM) did not affect root elongation. The results indicate that ABA is not a likely mediator of root gravitropism and that the putative ABA precursor, Xan, lacks the appropriate growth-inhibiting properties to serve as a mediator of root gravitropism.

Cross-talk between abscisic acid-dependent and abscisic acid-independent pathways during abiotic stress.

PubMed

Roychoudhury, Aryadeep; Paul, Saikat; Basu, Supratim

2013-07-01

Salinity, drought and low temperature are the common forms of abiotic stress encountered by land plants. To cope with these adverse environmental factors, plants execute several physiological and metabolic responses. Both osmotic stress (elicited by water deficit or high salt) and cold stress increase the endogenous level of the phytohormone abscisic acid (ABA). ABA-dependent stomatal closure to reduce water loss is associated with small signaling molecules like nitric oxide, reactive oxygen species and cytosolic free calcium, and mediated by rapidly altering ion fluxes in guard cells. ABA also triggers the expression of osmotic stress-responsive (OR) genes, which usually contain single/multiple copies of cis-acting sequence called abscisic acid-responsive element (ABRE) in their upstream regions, mostly recognized by the basic leucine zipper-transcription factors (TFs), namely, ABA-responsive element-binding protein/ABA-binding factor. Another conserved sequence called the dehydration-responsive element (DRE)/C-repeat, responding to cold or osmotic stress, but not to ABA, occurs in some OR promoters, to which the DRE-binding protein/C-repeat-binding factor binds. In contrast, there are genes or TFs containing both DRE/CRT and ABRE, which can integrate input stimuli from salinity, drought, cold and ABA signaling pathways, thereby enabling cross-tolerance to multiple stresses. A strong candidate that mediates such cross-talk is calcium, which serves as a common second messenger for abiotic stress conditions and ABA. The present review highlights the involvement of both ABA-dependent and ABA-independent signaling components and their interaction or convergence in activating the stress genes. We restrict our discussion to salinity, drought and cold stress.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cha, Min-Ji; Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, 250 Seongsanno, Seodamun-gu, Seoul 120-752; Jang, Jin-Kyung

Highlights: •CaMKIIδ mediates H{sub 2}O{sub 2}-induced Ca{sup 2+} overload in cardiomyocytes. •miR-145 can inhibit Ca{sup 2+} overload. •A luciferase assay confirms that miR-145 functions as a CaMKIIδ-targeting miRNA. •Overexpression of miR-145 regulates CaMKIIδ-related genes and ameliorates apoptosis. -- Abstract: A change in intracellular free calcium (Ca{sup 2+}) is a common signaling mechanism of reperfusion-induced cardiomyocyte death. Calcium/calmodulin dependent protein kinase II (CaMKII) is a critical regulator of Ca{sup 2+} signaling and mediates signaling pathways responsible for functions in the heart including hypertrophy, apoptosis, arrhythmia, and heart disease. MicroRNAs (miRNA) are involved in the regulation of cell response, including survival, proliferation,more » apoptosis, and development. However, the roles of miRNAs in Ca{sup 2+}-mediated apoptosis of cardiomyocytes are uncertain. Here, we determined the potential role of miRNA in the regulation of CaMKII dependent apoptosis and explored its underlying mechanism. To determine the potential roles of miRNAs in H{sub 2}O{sub 2}-mediated Ca{sup 2+} overload, we selected and tested 6 putative miRNAs that targeted CaMKIIδ, and showed that miR-145 represses CaMKIIδ protein expression and Ca{sup 2+} overload. We confirmed CaMKIIδ as a direct downstream target of miR-145. Furthermore, miR-145 regulates Ca{sup 2+}-related signals and ameliorates apoptosis. This study demonstrates that miR-145 regulates reactive oxygen species (ROS)-induced Ca{sup 2+} overload in cardiomyocytes. Thus, miR-145 affects ROS-mediated gene regulation and cellular injury responses.« less

Abscisic acid promotes proteasome-mediated degradation of the transcription coactivator NPR1 in Arabidopsis thaliana.

PubMed

Ding, Yezhang; Dommel, Matthew; Mou, Zhonglin

2016-04-01

Proteasome-mediated turnover of the transcription coactivator NPR1 is pivotal for efficient activation of the broad-spectrum plant immune responses known as localized acquired resistance (LAR) and systemic acquired resistance (SAR) in adjacent and systemic tissues, respectively, and requires the CUL3-based E3 ligase and its adaptor proteins, NPR3 and NPR4, which are receptors for the signaling molecule salicylic acid (SA). It has been shown that SA prevents NPR1 turnover under non-inducing and LAR/SAR-inducing conditions, but how cellular NPR1 homeostasis is maintained remains unclear. Here, we show that the phytohormone abscisic acid (ABA) and SA antagonistically influence cellular NPR1 protein levels. ABA promotes NPR1 degradation via the CUL3(NPR) (3/) (NPR) (4) complex-mediated proteasome pathway, whereas SA may protect NPR1 from ABA-promoted degradation through phosphorylation. Furthermore, we demonstrate that the timing and strength of SA and ABA signaling are critical in modulating NPR1 accumulation and target gene expression. Perturbing ABA or SA signaling in adjacent tissues alters the temporal dynamic pattern of NPR1 accumulation and target gene transcription. Finally, we show that sequential SA and ABA treatment leads to dynamic changes in NPR1 protein levels and target gene expression. Our results revealed a tight correlation between sequential SA and ABA signaling and dynamic changes in NPR1 protein levels and NPR1-dependent transcription in plant immune responses. © 2016 The Authors The Plant Journal © 2016 John Wiley & Sons Ltd.

Rice Stomatal Closure Requires Guard Cell Plasma Membrane ATP-Binding Cassette Transporter RCN1/OsABCG5.

PubMed

Matsuda, Shuichi; Takano, Sho; Sato, Moeko; Furukawa, Kaoru; Nagasawa, Hidetaka; Yoshikawa, Shoko; Kasuga, Jun; Tokuji, Yoshihiko; Yazaki, Kazufumi; Nakazono, Mikio; Takamure, Itsuro; Kato, Kiyoaki

2016-03-07

Water stress is one of the major environmental stresses that affect agricultural production worldwide. Water loss from plants occurs primarily through stomatal pores. Here, we report that an Oryza sativa half-size ATP-binding cassette (ABC) subfamily G protein, RCN1/OsABCG5, is involved in stomatal closure mediated by phytohormone abscisic acid (ABA) accumulation in guard cells. We found that the GFP-RCN1/OsABCG5-fusion protein was localized at the plasma membrane in guard cells. The percentage of guard cell pairs containing both ABA and GFP-RCN1/OsABCG5 increased after exogenous ABA treatment, whereas they were co-localized in guard cell pairs regardless of whether exogenous ABA was applied. ABA application resulted in a smaller increase in the percentage of guard cell pairs containing ABA in rcn1 mutant (A684P) and RCN1-RNAi than in wild-type plants. Furthermore, polyethylene glycol (drought stress)-inducible ABA accumulation in guard cells did not occur in rcn1 mutants. Stomata closure mediated by exogenous ABA application was strongly reduced in rcn1 mutants. Finally, rcn1 mutant plants had more rapid water loss from detached leaves than the wild-type plants. These results indicate that in response to drought stress, RCN1/OsABCG5 is involved in accumulation of ABA in guard cells, which is indispensable for stomatal closure. Copyright © 2016 The Author. Published by Elsevier Inc. All rights reserved.

Chronic restraint stress inhibits hair growth via substance P mediated by reactive oxygen species in mice.

PubMed

Liu, Nan; Wang, Lin-Hui; Guo, Ling-Ling; Wang, Guo-Qing; Zhou, Xi-Ping; Jiang, Yan; Shang, Jing; Murao, Koji; Chen, Jing-Wei; Fu, Wen-Qing; Zhang, Guo-Xing

2013-01-01

Solid evidence has demonstrated that psychoemotional stress induced alteration of hair cycle through neuropeptide substance P (SP) mediated immune response, the role of reactive oxygen species (ROS) in brain-skin-axis regulation system remains unknown. The present study aims to investigate possible mechanisms of ROS in regulation of SP-mast cell signal pathway in chronic restraint stress (CRS, a model of chronic psychoemotional stress) which induced abnormal of hair cycle. Our results have demonstrated that CRS actually altered hair cycle by inhibiting hair follicle growth in vivo, prolonging the telogen stage and delaying subsequent anagen and catagen stage. Up-regulation of SP protein expression in cutaneous peripheral nerve fibers and activation of mast cell were observed accompanied with increase of lipid peroxidation levels and reduction of the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in CRS mice skin. In addition, SP receptor antagonist (RP67580) reduced mast cell activations and lipid peroxidation levels as well as increased GSH-Px activity and normalized hair cycle. Furthermore, antioxidant Tempol (a free radical scavenger) also restored hair cycle, reduced SP protein expression and mast cell activation. Our study provides the first solid evidence for how ROS play a role in regulation of psychoemotional stress induced SP-Mast cell pathway which may provide a convincing rationale for antioxidant application in clinical treatment with psychological stress induced hair loss.

Lycopene inhibits regulator of calcineurin 1-mediated apoptosis by reducing oxidative stress and down-regulating Nucling in neuronal cells.

PubMed

Lim, Seiyoung; Hwang, Sinwoo; Yu, Ji Hoon; Lim, Joo Weon; Kim, Hyeyoung

2017-05-01

Regulator of calcineurin 1 (RCAN1) is located on the Down syndrome critical region (DSCR) locus in human chromosome 21. Oxidative stress and overexpression of RCAN1 are implicated in neuronal impairment in Down's syndrome (DS) and Alzheimer's disease (AD). Serum level of lycopene, an antioxidant pigment, is low in DS and AD patients, which may be related to neuronal damage. The present study is to investigate whether lycopene inhibits apoptosis by reducing ROS levels, NF-κB activation, expression of the apoptosis regulator Nucling, cell viability, and indices of apoptosis (cytochrome c release, caspase-3 activation) in RCAN1-overexpressing neuronal cells. Cells transfected with either pcDNA or RCAN1 were treated with or without lycopene. Lycopene decreased intracellular and mitochondrial ROS levels, NF-κB activity, and Nucling expression while it reversed decrease in mitochondrial membrane potential, mitochondrial respiration, and glycolytic function in RCAN1-overexpressing cells. Lycopene inhibited cell death, DNA fragmentation, caspase-3 activation, and cytochrome c release in RCAN1-overexpressing cells. Lycopene inhibits RCAN1-mediated apoptosis by reducing ROS levels and by inhibiting NF-κB activation, Nucling induction, and the increase in apoptotic indices in neuronal cells. Consumption of lycopene-rich foods may prevent oxidative stress-associated neuronal damage in some pathologic conditions such as DS or AD. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Differential activation of genes related to aluminium tolerance in two contrasting rice cultivars.

PubMed

Roselló, Maite; Poschenrieder, Charlotte; Gunsé, Benet; Barceló, Juan; Llugany, Mercè

2015-11-01

Rice (Oryza sativa) is a highly Al-tolerant crop. Among other mechanisms, a higher expression of STAR1/STAR2 (sensitive to Al rhizotoxicity1/2) genes and of Nrat1 (NRAMP Aluminium Transporter 1), and ALS1 (Aluminium sensitive 1) can at least in part be responsible for the inducible Al tolerance in this species. Here we analysed the responses to Al in two contrasting rice varieties. All analysed toxicity/tolerance markers (root elongation, Evans blue, morin and haematoxylin staining) indicated higher Al-tolerance in variety Nipponbare, than in variety Modan. Nipponbare accumulated much less Al in the roots than Modan. Aluminium supply caused stronger expression of STAR1 in Nipponbare than in Modan. A distinctively higher increase of Al-induced abscisic acid (ABA) accumulation was found in the roots of Nipponbare than in Modan. Highest ABA levels were observed in Nipponbare after 48 h exposure to Al. This ABA peak was coincident in time with the highest expression level of STAR1. It is proposed that ABA may be required for cell wall remodulation facilitated by the enhanced UDP-glucose transport to the walls through STAR1/STAR2. Contrastingly, in the roots of Modan the expression of both Nrat1 coding for a plasma membrane Al-transporter and of ALS1 coding for a tonoplast-localized Al transporter was considerably enhanced. Moreover, Modan had a higher Al-induced expression of ASR1 a gene that has been proposed to code for a reactive oxygen scavenging protein. In conclusion, the Al-exclusion strategy of Nipponbare, at least in part mediated by STAR1 and probably regulated by ABA, provided better protection against Al toxicity than the accumulation and internal detoxification strategy of Modan mediated by Nrat1, ALS1 and ARS1. Copyright © 2015 Elsevier Inc. All rights reserved.

β-Sitosterol targets Trx/Trx1 reductase to induce apoptosis in A549 cells via ROS mediated mitochondrial dysregulation and p53 activation.

PubMed

Rajavel, Tamilselvam; Packiyaraj, Pandian; Suryanarayanan, Venkatesan; Singh, Sanjeev Kumar; Ruckmani, Kandasamy; Pandima Devi, Kasi

2018-02-01

β-Sitosterol (BS), a major bioactive constituent present in plants and vegetables has shown potent anticancer effect against many human cancer cells, but the underlying mechanism remain elusive on NSCLC cancers. We found that BS significantly inhibited the growth of A549 cells without harming normal human lung and PBMC cells. Further, BS treatment triggered apoptosis via ROS mediated mitochondrial dysregulation as evidenced by caspase-3 & 9 activation, Annexin-V/PI positive cells, PARP inactivation, loss of MMP, Bcl-2-Bax ratio alteration and cytochrome c release. Moreover, generation of ROS species and subsequent DNA stand break were found upon BS treatment which was reversed by addition of ROS scavenger (NAC). Indeed BS treatment increased p53 expression and its phosphorylation at Ser15, while silencing the p53 expression by pifithrin-α, BS induced apoptosis was reduced in A549 cells. Furthermore, BS induced apoptosis was also observed in NCI-H460 cells (p53 wild) but not in the NCI-H23 cells (p53 mutant). Down-regulation of Trx/Trx1 reductase contributed to the BS induced ROS accumulation and mitochondrial mediated apoptotic cell death in A549 and NCI-H460 cells. Taken together, our findings provide evidence for the novel anti-cancer mechanism of BS which could be developed as a promising chemotherapeutic drug against NSCLC cancers.

Nitric oxide and redox mechanisms in the immune response

PubMed Central

Wink, David A.; Hines, Harry B.; Cheng, Robert Y. S.; Switzer, Christopher H.; Flores-Santana, Wilmarie; Vitek, Michael P.; Ridnour, Lisa A.; Colton, Carol A.

2011-01-01

The role of redox molecules, such as NO and ROS, as key mediators of immunity has recently garnered renewed interest and appreciation. To regulate immune responses, these species trigger the eradication of pathogens on the one hand and modulate immunosuppression during tissue-restoration and wound-healing processes on the other. In the acidic environment of the phagosome, a variety of RNS and ROS is produced, thereby providing a cauldron of redox chemistry, which is the first line in fighting infection. Interestingly, fluctuations in the levels of these same reactive intermediates orchestrate other phases of the immune response. NO activates specific signal transduction pathways in tumor cells, endothelial cells, and monocytes in a concentration-dependent manner. As ROS can react directly with NO-forming RNS, NO bioavailability and therefore, NO response(s) are changed. The NO/ROS balance is also important during Th1 to Th2 transition. In this review, we discuss the chemistry of NO and ROS in the context of antipathogen activity and immune regulation and also discuss similarities and differences between murine and human production of these intermediates. PMID:21233414

Global transcriptional profiling of a cold-tolerant rice variety under moderate cold stress reveals different cold stress response mechanisms.

PubMed

Zhao, Junliang; Zhang, Shaohong; Yang, Tifeng; Zeng, Zichong; Huang, Zhanghui; Liu, Qing; Wang, Xiaofei; Leach, Jan; Leung, Hei; Liu, Bin

2015-07-01

Gene expression profiling under severe cold stress (4°C) has been conducted in plants including rice. However, rice seedlings are frequently exposed to milder cold stresses under natural environments. To understand the responses of rice to milder cold stress, a moderately low temperature (8°C) was used for cold treatment prior to genome-wide profiling of gene expression in a cold-tolerant japonica variety, Lijiangxintuanheigu (LTH). A total of 5557 differentially expressed genes (DEGs) were found at four time points during moderate cold stress. Both the DEGs and differentially expressed transcription factor genes were clustered into two groups based on their expression, suggesting a two-phase response to cold stress and a determinative role of transcription factors in the regulation of stress response. The induction of OsDREB2A under cold stress is reported for the first time in this study. Among the anti-oxidant enzyme genes, glutathione peroxidase (GPX) and glutathione S-transferase (GST) were upregulated, suggesting that the glutathione system may serve as the main reactive oxygen species (ROS) scavenger in LTH. Changes in expression of genes in signal transduction pathways for auxin, abscisic acid (ABA) and salicylic acid (SA) imply their involvement in cold stress responses. The induction of ABA response genes and detection of enriched cis-elements in DEGs suggest that ABA signaling pathway plays a dominant role in the cold stress response. Our results suggest that rice responses to cold stress vary with the specific temperature imposed and the rice genotype. © 2014 Scandinavian Plant Physiology Society.

Abscisic Acid Regulates Auxin Homeostasis in Rice Root Tips to Promote Root Hair Elongation

PubMed Central

Wang, Tao; Li, Chengxiang; Wu, Zhihua; Jia, Yancui; Wang, Hong; Sun, Shiyong; Mao, Chuanzao; Wang, Xuelu

2017-01-01

Abscisic acid (ABA) plays an essential role in root hair elongation in plants, but the regulatory mechanism remains to be elucidated. In this study, we found that exogenous ABA can promote rice root hair elongation. Transgenic rice overexpressing SAPK10 (Stress/ABA-activated protein kinase 10) had longer root hairs; rice plants overexpressing OsABIL2 (OsABI-Like 2) had attenuated ABA signaling and shorter root hairs, suggesting that the effect of ABA on root hair elongation depends on the conserved PYR/PP2C/SnRK2 ABA signaling module. Treatment of the DR5-GUS and OsPIN-GUS lines with ABA and an auxin efflux inhibitor showed that ABA-induced root hair elongation depends on polar auxin transport. To examine the transcriptional response to ABA, we divided rice root tips into three regions: short root hair, long root hair and root tip zones; and conducted RNA-seq analysis with or without ABA treatment. Examination of genes involved in auxin transport, biosynthesis and metabolism indicated that ABA promotes auxin biosynthesis and polar auxin transport in the root tip, which may lead to auxin accumulation in the long root hair zone. Our findings shed light on how ABA regulates root hair elongation through crosstalk with auxin biosynthesis and transport to orchestrate plant development. PMID:28702040

miR-5591-5p regulates the effect of ADSCs in repairing diabetic wound via targeting AGEs/AGER/JNK signaling axis.

PubMed

Li, Qiang; Xia, Sizhan; Yin, Yating; Guo, Yanping; Chen, Feifei; Jin, Peisheng

2018-05-11

Advanced glycation end products/advanced glycation end products receptor (AGEs/AGER) interaction triggers reactive oxygen species (ROS) generation and activates downstream signal pathways and induces apoptosis in endothelial progenitor cells. A number of studies have revealed the involvement of microRNAs (miRNAs) in regulating intracellular ROS production and apoptosis. However, few studies explore the role of miRNAs in regulating the effect of adipose tissue-derived stem cells (ADSCs) in repairing diabetic wound and the associated cellular mechanisms remain unclear. In this study, ADSCs were exposed to AGEs, then siRNA for AGER was transfected into ADSCs. We found that AGEs/AGER axis induced ROS generation and apoptosis in ADSCs. AGEs treatment downregulated miR-5591-5p in ADSCs, which directly targeted AGER. miR-5591-5p suppressed AGEs/AGER axis-mediated ROS generation and apoptosis in ADSCs in vitro. In addition, miR-5591-5p promoted cell survival and enhanced the ability of ADSCs for repairing cutaneous wound in vivo. Furthermore, we confirmed that c-jun kinase (JNK) signal was involved in the inhibitory effect of miR-5591-5p on AGEs/AGER axis-induced ROS generation and apoptosis in ADSCs. Thus, these results indicated that miR-5591-5p targeting AGEs/AGER/JNK signaling axis possibly regulates the effect of ADSCs in repairing diabetic wound.

Plant responses to water stress

PubMed Central

Kar, Rup Kumar

2011-01-01

Terrestrial plants most often encounter drought stress because of erratic rainfall which has become compounded due to present climatic changes.Responses of plants to water stress may be assigned as either injurious change or tolerance index. One of the primary and cardinal changes in response to drought stress is the generation of reactive oxygen species (ROS), which is being considered as the cause of cellular damage. However, recently a signaling role of such ROS in triggering the ROS scavenging system that may confer protection or tolerance against stress is emerging. Such scavenging system consists of antioxidant enzymes like SOD, catalase and peroxidases, and antioxidant compounds like ascorbate, reduced glutathione; a balance between ROS generation and scavenging ultimately determines the oxidative load. As revealed in case of defence against pathogen, signaling via ROS is initiated by NADPH oxidase-catalyzed superoxide generation in the apoplastic space (cell wall) followed by conversion to hydrogen peroxide by the activity of cell wall-localized SOD. Wall peroxidase may also play role in ROS generation for signaling. Hydrogen peroxide may use Ca2+ and MAPK pathway as downstream signaling cascade. Plant hormones associated with stress responses like ABA and ethylene play their role possibly via a cross talk with ROS towards stress tolerance, thus projecting a dual role of ROS under drought stress. PMID:22057331

Abscisic Acid–Responsive Guard Cell Metabolomes of Arabidopsis Wild-Type and gpa1 G-Protein Mutants[C][W

PubMed Central

Jin, Xiaofen; Wang, Rui-Sheng; Zhu, Mengmeng; Jeon, Byeong Wook; Albert, Reka; Chen, Sixue; Assmann, Sarah M.

2013-01-01

Individual metabolites have been implicated in abscisic acid (ABA) signaling in guard cells, but a metabolite profile of this specialized cell type is lacking. We used liquid chromatography–multiple reaction monitoring mass spectrometry for targeted analysis of 85 signaling-related metabolites in Arabidopsis thaliana guard cell protoplasts over a time course of ABA treatment. The analysis utilized ∼350 million guard cell protoplasts from ∼30,000 plants of the Arabidopsis Columbia accession (Col) wild type and the heterotrimeric G-protein α subunit mutant, gpa1, which has ABA-hyposensitive stomata. These metabolomes revealed coordinated regulation of signaling metabolites in unrelated biochemical pathways. Metabolites clustered into different temporal modules in Col versus gpa1, with fewer metabolites showing ABA-altered profiles in gpa1. Ca2+-mobilizing agents sphingosine-1-phosphate and cyclic adenosine diphosphate ribose exhibited weaker ABA-stimulated increases in gpa1. Hormone metabolites were responsive to ABA, with generally greater responsiveness in Col than in gpa1. Most hormones also showed different ABA responses in guard cell versus mesophyll cell metabolomes. These findings suggest that ABA functions upstream to regulate other hormones, and are also consistent with G proteins modulating multiple hormonal signaling pathways. In particular, indole-3-acetic acid levels declined after ABA treatment in Col but not gpa1 guard cells. Consistent with this observation, the auxin antagonist α-(phenyl ethyl-2-one)-indole-3-acetic acid enhanced ABA-regulated stomatal movement and restored partial ABA sensitivity to gpa1. PMID:24368793

Separating Active and Passive Influences on Stomatal Control of Transpiration[OPEN

PubMed Central

McAdam, Scott A.M.; Brodribb, Timothy J.

2014-01-01

Motivated by studies suggesting that the stomata of ferns and lycophytes do not conform to the standard active abscisic acid (ABA) -mediated stomatal control model, we examined stomatal behavior in a conifer species (Metasequoia glyptostroboides) that is phylogenetically midway between the fern and angiosperm clades. Similar to ferns, daytime stomatal closure in response to moderate water stress seemed to be a passive hydraulic process in M. glyptostroboides immediately alleviated by rehydrating excised shoots. Only after prolonged exposure to more extreme water stress did active ABA-mediated stomatal closure become important, because foliar ABA production was triggered after leaf turgor loss. The influence of foliar ABA on stomatal conductance and stomatal aperture was highly predictable and additive with the passive hydraulic influence. M. glyptostroboides thus occupies a stomatal behavior type intermediate between the passively controlled ferns and the characteristic ABA-dependent stomatal closure described in angiosperm herbs. These results highlight the importance of considering phylogeny as a major determinant of stomatal behavior. PMID:24488969

Separating active and passive influences on stomatal control of transpiration.

PubMed

McAdam, Scott A M; Brodribb, Timothy J

2014-04-01

Motivated by studies suggesting that the stomata of ferns and lycophytes do not conform to the standard active abscisic acid (ABA) -mediated stomatal control model, we examined stomatal behavior in a conifer species (Metasequoia glyptostroboides) that is phylogenetically midway between the fern and angiosperm clades. Similar to ferns, daytime stomatal closure in response to moderate water stress seemed to be a passive hydraulic process in M. glyptostroboides immediately alleviated by rehydrating excised shoots. Only after prolonged exposure to more extreme water stress did active ABA-mediated stomatal closure become important, because foliar ABA production was triggered after leaf turgor loss. The influence of foliar ABA on stomatal conductance and stomatal aperture was highly predictable and additive with the passive hydraulic influence. M. glyptostroboides thus occupies a stomatal behavior type intermediate between the passively controlled ferns and the characteristic ABA-dependent stomatal closure described in angiosperm herbs. These results highlight the importance of considering phylogeny as a major determinant of stomatal behavior.

6-Shogaol, an active compound of ginger, alleviates allergic dermatitis-like skin lesions via cytokine inhibition by activating the Nrf2 pathway

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Gunhyuk, E-mail: uranos5@kiom.re.kr

Allergic dermatitis (AD) clinically presents with skin erythematous plaques, eruption, and elevated serum IgE, and T helper cell type 2 and 1 (Th2 and Th1) cytokine levels. 6-Shogaol [1-(4-hydroxy-methoxyphenyl)-4-decen-one], a pungent compound isolated from ginger, has shown anti-inflammatory effects, but its inhibitory effects on AD are unknown. The aim of this study was to examine whether 6-shogaol inhibits AD-like skin lesions and their underlying mechanism in vivo and in vitro. An AD-like response was induced by tumor necrosis factor-α (TNF-α) + IFN-γ in human keratinocytes or by 2,4-dinitrochlorobenzene (DNCB) in mice. In vivo, 6-shogaol inhibited the development of DNCB-induced AD-likemore » skin lesions and scratching behavior, and showed significant reduction in Th2/1-mediated inflammatory cytokines, IgE, TNF-α, IFN-γ, thymus and activation-regulated chemokine, IL-1, 4, 12, and 13, cyclooxygenase-2, and nitric oxide synthase levels. In vitro, 6-shogaol inhibited reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPKs) signaling, and increased the levels of total glutathione, heme oxygenase-1, and quinone 1 via nuclear factor erythroid 2 related factor 2 (Nrf2) activation. 6-Shogaol can alleviate AD-like skin lesions by inhibiting immune mediators via regulating the ROS/MAPKs/Nrf2 signaling pathway, and may be an effective alternative therapy for AD. - Highlights: • 6-Shogaol inhibited Th2/1-mediated inflammatory mediators in vitro and in vivo. • 6-Shogaol regulated ROS/MAPKs/Nrf2 signaling pathway. • 6-Shogaol can protect against the development of AD-like skin lesions.« less

Abscisic acid regulation of DC8, a carrot embryonic gene. [Daucus carota

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hatzopoulos, P.; Fong, F.; Sung, Z.R.

1990-10-01

DC8 encodes a hydrophylic 66 kilodalton protein located in the cytoplasm and cell walls of carrot (Daucus carota) embryo and endosperm. During somatic embryogenesis, the levels of DC8 mRNA and protein begin to increase 5 days after removal of auxin. To study the role of abscisic acid (ABA) in the regulation of DC8 gene, fluridone, 1-methyl-3-phenyl,-5(3-trifluoro-methyl-phenyl)-4(1H)-pyridinone, was used to inhibit the endogenous ABA content of the embryos. Fluridone, 50 micrograms per milliliter, effectively inhibits the accumulation of ABA in globular-tage embryos. Western and Northern analysis show that when fluridone is added to the culture medium DC8 protein and mRNA decreasemore » to very low levels. ABA added to fluridone supplemented culture media restores the DC8 protein and mRNA to control levels. Globular-stage embryos contain 0.9 to 1.4 {times} 10{sup {minus}7} molar ABA while 10{sup {minus}6} molar exogenously supplied ABA is the optimal concentration for restoration of DC8 protein accumulation in fluridone-treated embryos. The mRNA level is increased after 15 minutes of ABA addition and reaches maximal levels by 60 minutes. Evidence is presented that, unlike other ABA-regulated genes, DC8 is not induced in nonembryonic tissues via desiccation nor addition of ABA.« less

Mutations in the Arabidopsis Lst8 and Raptor genes encoding partners of the TOR complex, or inhibition of TOR activity decrease abscisic acid (ABA) synthesis.

PubMed

Kravchenko, Alena; Citerne, Sylvie; Jéhanno, Isabelle; Bersimbaev, Rakhmetkazhi I; Veit, Bruce; Meyer, Christian; Leprince, Anne-Sophie

2015-11-27

The Target of Rapamycin (TOR) kinase regulates essential processes in plant growth and development by modulation of metabolism and translation in response to environmental signals. In this study, we show that abscisic acid (ABA) metabolism is also regulated by the TOR kinase. Indeed ABA hormone level strongly decreases in Lst8-1 and Raptor3g mutant lines as well as in wild-type (WT) Arabidopsis plants treated with AZD-8055, a TOR inhibitor. However the growth and germination of these lines are more sensitive to exogenous ABA. The diminished ABA hormone accumulation is correlated with lower transcript levels of ZEP, NCED3 and AAO3 biosynthetic enzymes, and higher transcript amount of the CYP707A2 gene encoding a key-enzyme in abscisic acid catabolism. These results suggest that the TOR signaling pathway is implicated in the regulation of ABA accumulation in Arabidopsis. Copyright © 2015 Elsevier Inc. All rights reserved.

Abscisic Acid Regulation of Root Hydraulic Conductivity and Aquaporin Gene Expression Is Crucial to the Plant Shoot Growth Enhancement Caused by Rhizosphere Humic Acids.

PubMed

Olaetxea, Maite; Mora, Verónica; Bacaicoa, Eva; Garnica, María; Fuentes, Marta; Casanova, Esther; Zamarreño, Angel M; Iriarte, Juan C; Etayo, David; Ederra, Iñigo; Gonzalo, Ramón; Baigorri, Roberto; García-Mina, Jose M

2015-12-01

The physiological and metabolic mechanisms behind the humic acid-mediated plant growth enhancement are discussed in detail. Experiments using cucumber (Cucumis sativus) plants show that the shoot growth enhancement caused by a structurally well-characterized humic acid with sedimentary origin is functionally associated with significant increases in abscisic acid (ABA) root concentration and root hydraulic conductivity. Complementary experiments involving a blocking agent of cell wall pores and water root transport (polyethylenglycol) show that increases in root hydraulic conductivity are essential in the shoot growth-promoting action of the model humic acid. Further experiments involving an inhibitor of ABA biosynthesis in root and shoot (fluridone) show that the humic acid-mediated enhancement of both root hydraulic conductivity and shoot growth depended on ABA signaling pathways. These experiments also show that a significant increase in the gene expression of the main root plasma membrane aquaporins is associated with the increase of root hydraulic conductivity caused by the model humic acid. Finally, experimental data suggest that all of these actions of model humic acid on root functionality, which are linked to its beneficial action on plant shoot growth, are likely related to the conformational structure of humic acid in solution and its interaction with the cell wall at the root surface. © 2015 American Society of Plant Biologists. All Rights Reserved.

Abscisic Acid Regulation of Root Hydraulic Conductivity and Aquaporin Gene Expression Is Crucial to the Plant Shoot Growth Enhancement Caused by Rhizosphere Humic Acids1

PubMed Central

Bacaicoa, Eva; Garnica, María; Fuentes, Marta; Casanova, Esther; Etayo, David; Ederra, Iñigo; Gonzalo, Ramón

2015-01-01

The physiological and metabolic mechanisms behind the humic acid-mediated plant growth enhancement are discussed in detail. Experiments using cucumber (Cucumis sativus) plants show that the shoot growth enhancement caused by a structurally well-characterized humic acid with sedimentary origin is functionally associated with significant increases in abscisic acid (ABA) root concentration and root hydraulic conductivity. Complementary experiments involving a blocking agent of cell wall pores and water root transport (polyethylenglycol) show that increases in root hydraulic conductivity are essential in the shoot growth-promoting action of the model humic acid. Further experiments involving an inhibitor of ABA biosynthesis in root and shoot (fluridone) show that the humic acid-mediated enhancement of both root hydraulic conductivity and shoot growth depended on ABA signaling pathways. These experiments also show that a significant increase in the gene expression of the main root plasma membrane aquaporins is associated with the increase of root hydraulic conductivity caused by the model humic acid. Finally, experimental data suggest that all of these actions of model humic acid on root functionality, which are linked to its beneficial action on plant shoot growth, are likely related to the conformational structure of humic acid in solution and its interaction with the cell wall at the root surface. PMID:26450705

The putative glutamate receptor 1.1 (AtGLR1.1) in Arabidopsis thaliana regulates abscisic acid biosynthesis and signaling to control development and water loss.

PubMed

Kang, Jiman; Mehta, Sohum; Turano, Frank J

2004-10-01

The involvement of the putative glutamate receptor 1.1 (AtGLR1.1) gene in the regulation of abscisic acid (ABA) biosynthesis and signaling was investigated in Arabidopsis. Seeds from AtGLR1.1-deficient (antiAtGLR1.1) lines had increased sensitivity to exogenous ABA with regard to the effect of the hormone on the inhibition of seed germination and root growth. Seed germination, which was inhibited by an animal ionotropic glutamate receptor antagonist, 6,7-dinitroquinoxaline-2,3-[1H,4H]-dione, was restored by co-incubation with an inhibitor of ABA biosynthesis, fluridone. These results confirm that germination in antiAtGLR1.1 lines was inhibited by increased ABA. When antiAtGLR1.1 and WT seeds were co-incubated in fluridone and exogenous ABA, the antiAtGLR1.1 seeds were more sensitive to ABA. In addition, the antiAtGLR1.1 lines exhibited altered expression of ABA biosynthetic (ABA) and signaling (ABI) genes, when compared with WT. Combining the physiological and molecular results suggest that ABA biosynthesis and signaling in antiAtGLR1.1 lines are altered. ABA levels in leaves of antiAtGLR1.1 lines are higher than those in WT. In addition, the antiAtGLR1.1 lines had reduced stomatal apertures, and exhibited enhanced drought tolerance due to deceased water loss compared with WT lines. The results from these experiments imply that ABA biosynthesis and signaling can be regulated through AtGLR1.1 to trigger pre- and post-germination arrest and changes in whole plant responses to water stress. Combined with our earlier results, these findings suggest that AtGLR1.1 integrates and regulates the different aspects of C, N and water balance that are required for normal plant growth and development.

Genome-wide targeted prediction of ABA responsive genes in rice based on over-represented cis-motif in co-expressed genes.

PubMed

Lenka, Sangram K; Lohia, Bikash; Kumar, Abhay; Chinnusamy, Viswanathan; Bansal, Kailash C

2009-02-01

Abscisic acid (ABA), the popular plant stress hormone, plays a key role in regulation of sub-set of stress responsive genes. These genes respond to ABA through specific transcription factors which bind to cis-regulatory elements present in their promoters. We discovered the ABA Responsive Element (ABRE) core (ACGT) containing CGMCACGTGB motif as over-represented motif among the promoters of ABA responsive co-expressed genes in rice. Targeted gene prediction strategy using this motif led to the identification of 402 protein coding genes potentially regulated by ABA-dependent molecular genetic network. RT-PCR analysis of arbitrarily chosen 45 genes from the predicted 402 genes confirmed 80% accuracy of our prediction. Plant Gene Ontology (GO) analysis of ABA responsive genes showed enrichment of signal transduction and stress related genes among diverse functional categories.

Molecular mimicry regulates ABA signaling by SnRK2 kinases and PP2C phosphatases.

PubMed

Soon, Fen-Fen; Ng, Ley-Moy; Zhou, X Edward; West, Graham M; Kovach, Amanda; Tan, M H Eileen; Suino-Powell, Kelly M; He, Yuanzheng; Xu, Yong; Chalmers, Michael J; Brunzelle, Joseph S; Zhang, Huiming; Yang, Huaiyu; Jiang, Hualiang; Li, Jun; Yong, Eu-Leong; Cutler, Sean; Zhu, Jian-Kang; Griffin, Patrick R; Melcher, Karsten; Xu, H Eric

2012-01-06

Abscisic acid (ABA) is an essential hormone for plants to survive environmental stresses. At the center of the ABA signaling network is a subfamily of type 2C protein phosphatases (PP2Cs), which form exclusive interactions with ABA receptors and subfamily 2 Snfl-related kinase (SnRK2s). Here, we report a SnRK2-PP2C complex structure, which reveals marked similarity in PP2C recognition by SnRK2 and ABA receptors. In the complex, the kinase activation loop docks into the active site of PP2C, while the conserved ABA-sensing tryptophan of PP2C inserts into the kinase catalytic cleft, thus mimicking receptor-PP2C interactions. These structural results provide a simple mechanism that directly couples ABA binding to SnRK2 kinase activation and highlight a new paradigm of kinase-phosphatase regulation through mutual packing of their catalytic sites.

A novel cold-inducible zinc finger protein from soybean, SCOF-1, enhances cold tolerance in transgenic plants.

PubMed

Kim, J C; Lee, S H; Cheong, Y H; Yoo, C M; Lee, S I; Chun, H J; Yun, D J; Hong, J C; Lee, S Y; Lim, C O; Cho, M J

2001-02-01

Cold stress on plants induces changes in the transcription of cold response genes. A cDNA clone encoding C2H2-type zinc finger protein, SCOF-1, was isolated from soybean. The transcription of SCOF-1 is specifically induced by low temperature and abscisic acid (ABA) but not by dehydration or high salinity. Constitutive overexpression of SCOF-1 induced cold-regulated (COR) gene expression and enhanced cold tolerance of non-acclimated transgenic Arabidopsis and tobacco plants. SCOF-1 localized to the nucleus but did not bind directly to either C-repeat/dehydration (CRT/DRE) or ABA responsive element (ABRE), cis-acting DNA regulatory elements present in COR gene promoters. However, SCOF-1 greatly enhanced the DNA binding activity of SGBF-1, a soybean G-box binding bZIP transcription factor, to ABRE in vitro. SCOF-1 also interacted with SGBF-1 in a yeast two-hybrid system. The SGBF-1 transactivated the beta-glucuronidase reporter gene driven by the ABRE element in Arabidopsis leaf protoplasts. Furthermore, the SCOF-1 enhanced ABRE-dependent gene expression mediated by SGBF-1. These results suggest that SCOF-1 may function as a positive regulator of COR gene expression mediated by ABRE via protein-protein interaction, which in turn enhances cold tolerance of plants.

Thioredoxin-interacting Protein Mediates High Glucose-induced Reactive Oxygen Species Generation by Mitochondria and the NADPH Oxidase, Nox4, in Mesangial Cells*

PubMed Central

Shah, Anu; Xia, Ling; Goldberg, Howard; Lee, Ken W.; Quaggin, Susan E.; Fantus, I. George

2013-01-01

Thioredoxin-interacting protein (TxNIP) is up-regulated by high glucose and is associated with oxidative stress. It has been implicated in hyperglycemia-induced β-cell dysfunction and apoptosis. As high glucose and oxidative stress mediate diabetic nephropathy (DN), the contribution of TxNIP was investigated in renal mesangial cell reactive oxygen species (ROS) generation and collagen synthesis. To determine the role of TxNIP, mouse mesangial cells (MC) cultured from wild-type C3H and TxNIP-deficient Hcb-19 mice were incubated in HG. Confocal microscopy was used to measure total and mitochondrial ROS production (DCF and MitoSOX) and collagen IV. Trx and NADPH oxidase activities were assayed and NADPH oxidase isoforms, Nox2 and Nox4, and antioxidant enzymes were determined by immunoblotting. C3H MC exposed to HG elicited a significant increase in cellular and mitochondrial ROS as well as Nox4 protein expression and NADPH oxidase activation, whereas Hcb-19 MC showed no response. Trx activity was attenuated by HG only in C3H MC. These defects in Hcb-19 MC were not due to increased antioxidant enzymes or scavenging of ROS, but associated with decreased ROS generation. Adenovirus-mediated overexpression of TxNIP in Hcb-19 MC and TxNIP knockdown with siRNA in C3H confirmed the specific role of TxNIP. Collagen IV accumulation in HG was markedly reduced in Hcb-19 cells. TxNIP is a critical component of the HG-ROS signaling pathway, required for the induction of mitochondrial and total cell ROS and the NADPH oxidase isoform, Nox4. TxNIP is a potential target to prevent DN. PMID:23329835

Lipid peroxidation and apoptotic response in rat brain areas induced by long-term administration of nandrolone: the mutual crosstalk between ROS and NF-kB.

PubMed

Turillazzi, Emanuela; Neri, Margherita; Cerretani, Daniela; Cantatore, Santina; Frati, Paola; Moltoni, Laura; Busardò, Francesco Paolo; Pomara, Cristoforo; Riezzo, Irene; Fineschi, Vittorio

2016-04-01

The aim of this study was to evaluate the played by oxidative stress in the apoptotic response in different brain areas of rats chronically treated with supra-physiological doses of nandrolone decanoate (ND). Immunohistochemical study and Western blot analysis were performed to evaluate cells' apoptosis and to measure the effects of expression of specific mediators, such as NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells), Bcl-2 (B-cell lymphoma 2), SMAC/DIABLO (second mitochondria-derived activator of caspases/direct IAP-binding protein with low PI) and VMAT2 (vesicular monoamine transporter 2) on apoptosis. The results of the present study indicate that a long-term administration of ND promotes oxidative injury in rat brain specific areas. A link between oxidative stress and NF-κB signalling pathways is supported by our results. In addition to high levels of oxidative stress, we consistently observed a strong immunopositivity to NF-κB. It has been argued that one of the pathways leading to the activation of NF-κB could be under reactive oxygen species (ROS)-mediated control. In fact, growing evidence suggests that although in limited doses, endogenous ROS may play an activating role in NF-κB signalling, while above a certain threshold, they may negatively impact upon this signalling. However, a mutual crosstalk between ROS and NF-κB exists and recent studies have shown that ROS activity is subject to negative feedback regulation by NF-κB, and that this negative regulation of ROS is the means through which NF-κB counters programmed cells. © 2016 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

Expression of an Arabidopsis molybdenum cofactor sulphurase gene in soybean enhances drought tolerance and increases yield under field conditions.

PubMed

Li, Yajun; Zhang, Jiachang; Zhang, Juan; Hao, Ling; Hua, Jinping; Duan, Liusheng; Zhang, Mingcai; Li, Zhaohu

2013-08-01

LOS5/ABA3 gene encoding molybdenum cofactor sulphurase is involved in aldehyde oxidase (AO) activity in Arabidopsis, which indirectly regulates ABA biosynthesis and increased stress tolerance. Here, we used a constitutive super promoter to drive LOS5/ABA3 overexpression in soybean (Glycine max L.) to enhance drought tolerance in growth chamber and field conditions. Expression of LOS5/ABA3 was up-regulated by drought stress, which led to increasing AO activity and then a notable increase in ABA accumulation. Transgenic soybean under drought stress had reduced water loss by decreased stomatal aperture size and transpiration rate, which alleviated leaf wilting and maintained higher relative water content. Exposed to drought stress, transgenic soybean exhibited reduced cell membrane damage by reducing electrolyte leakage and production of malondialdehyde and promoting proline accumulation and antioxidant enzyme activities. Also, overexpression of LOS5/ABA3 enhanced expression of stress-up-regulated genes. Furthermore, the seed yield of transgenic plants is at least 21% higher than that of wide-type plants under drought stress conditions in the field. These data suggest that overexpression of LOS5/ABA3 could improve drought tolerance in transgenic soybean via enhanced ABA accumulation, which could activate expression of stress-up-regulated genes and cause a series of physiological and biochemical resistant responses. © 2013 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

Maize DRE-binding proteins DBF1 and DBF2 are involved in rab17 regulation through the drought-responsive element in an ABA-dependent pathway.

PubMed

Kizis, Dimosthenis; Pagès, Montserrat

2002-06-01

The abscisic acid-responsive gene rab17 of maize is expressed during late embryogenesis, and is induced by ABA and desiccation in embryo and vegetative tissues. ABRE and DRE cis-elements are involved in regulation of the gene by ABA and drought. Using yeast one-hybrid screening, we isolated two cDNAs encoding two new DRE-binding proteins, designated DBF1 and DBF2, that are members of the AP2/EREBP transcription factor family. Analysis of mRNA accumulation profiles showed that DBF1 is induced during maize embryogenesis and after desiccation, NaCl and ABA treatments in plant seedlings, whereas the DBF2 mRNA is not induced. DNA-binding preferences of DBFs were analysed by electrophoretic mobility shift assays, and showed that both DBF1 and DBF2 bound to the wild-type DRE2 element, but not to the DRE2 mutant or to the DRE1 element which differs only in a single nucleotide. Transactivation activity using particle bombardment showed that DBF1 functioned as activator of DRE2-dependent transcription of rab17 promoter by ABA, whereas DBF2 overexpression had a repression action downregulating not only the basal promoter activity, but also the ABA effect. These results show that ABA plays a role in the regulation of DBF activity, and suggests the existence of an ABA-dependent pathway for the regulation of genes through the C-repeat/DRE element.

Arabidopsis type B cytokinin response regulators ARR1, ARR10, and ARR12 negatively regulate plant responses to drought

PubMed Central

Nguyen, Kien Huu; Ha, Chien Van; Nishiyama, Rie; Watanabe, Yasuko; Leyva-González, Marco Antonio; Fujita, Yasunari; Tran, Uven Thi; Li, Weiqiang; Tanaka, Maho; Seki, Motoaki; Schaller, G. Eric; Herrera-Estrella, Luis; Tran, Lam-Son Phan

2016-01-01

In this study, we used a loss-of-function approach to elucidate the functions of three Arabidopsis type B response regulators (ARRs)—namely ARR1, ARR10, and ARR12—in regulating the Arabidopsis plant responses to drought. The arr1,10,12 triple mutant showed a significant increase in drought tolerance versus WT plants, as indicated by its higher relative water content and survival rate on drying soil. This enhanced drought tolerance of arr1,10,12 plants can be attributed to enhanced cell membrane integrity, increased anthocyanin biosynthesis, abscisic acid (ABA) hypersensitivity, and reduced stomatal aperture, but not to altered stomatal density. Further drought-tolerance tests of lower-order double and single mutants indicated that ARR1, ARR10, and ARR12 negatively and redundantly control plant responses to drought, with ARR1 appearing to bear the most critical function among the three proteins. In agreement with these findings, a comparative genome-wide analysis of the leaves of arr1,10,12 and WT plants under both normal and dehydration conditions suggested a cytokinin (CK) signaling-mediated network controlling plant adaptation to drought via many dehydration/drought- and/or ABA-responsive genes that can provide osmotic adjustment and protection to cellular and membrane structures. Expression of all three ARR genes was repressed by dehydration and ABA treatments, inferring that plants down-regulate these genes as an adaptive mechanism to survive drought. Collectively, our results demonstrate that repression of CK response, and thus CK signaling, is one of the strategies plants use to cope with water deficit, providing novel insight for the design of drought-tolerant plants by genetic engineering. PMID:26884175

Arabidopsis type B cytokinin response regulators ARR1, ARR10, and ARR12 negatively regulate plant responses to drought.

PubMed

Nguyen, Kien Huu; Ha, Chien Van; Nishiyama, Rie; Watanabe, Yasuko; Leyva-González, Marco Antonio; Fujita, Yasunari; Tran, Uven Thi; Li, Weiqiang; Tanaka, Maho; Seki, Motoaki; Schaller, G Eric; Herrera-Estrella, Luis; Tran, L S

2016-03-15

In this study, we used a loss-of-function approach to elucidate the functions of three Arabidopsis type B response regulators (ARRs)--namely ARR1, ARR10, and ARR12--in regulating the Arabidopsis plant responses to drought. The arr1,10,12 triple mutant showed a significant increase in drought tolerance versus WT plants, as indicated by its higher relative water content and survival rate on drying soil. This enhanced drought tolerance of arr1,10,12 plants can be attributed to enhanced cell membrane integrity, increased anthocyanin biosynthesis, abscisic acid (ABA) hypersensitivity, and reduced stomatal aperture, but not to altered stomatal density. Further drought-tolerance tests of lower-order double and single mutants indicated that ARR1, ARR10, and ARR12 negatively and redundantly control plant responses to drought, with ARR1 appearing to bear the most critical function among the three proteins. In agreement with these findings, a comparative genome-wide analysis of the leaves of arr1,10,12 and WT plants under both normal and dehydration conditions suggested a cytokinin (CK) signaling-mediated network controlling plant adaptation to drought via many dehydration/drought- and/or ABA-responsive genes that can provide osmotic adjustment and protection to cellular and membrane structures. Expression of all three ARR genes was repressed by dehydration and ABA treatments, inferring that plants down-regulate these genes as an adaptive mechanism to survive drought. Collectively, our results demonstrate that repression of CK response, and thus CK signaling, is one of the strategies plants use to cope with water deficit, providing novel insight for the design of drought-tolerant plants by genetic engineering.

A role for jasmonates in the release of dormancy by cold stratification in wheat

PubMed Central

Xu, Qian; Truong, Thy T.; Barrero, Jose M.; Jacobsen, John V.; Hocart, Charles H.; Gubler, Frank

2016-01-01

Hydration at low temperatures, commonly referred to as cold stratification, is widely used for releasing dormancy and triggering germination in a wide range of species including wheat. However, the molecular mechanism that underlies its effect on germination has largely remained unknown. Our previous studies showed that methyl-jasmonate, a derivative of jasmonic acid (JA), promotes dormancy release in wheat. In this study, we found that cold-stimulated germination of dormant grains correlated with a transient increase in JA content and expression of JA biosynthesis genes in the dormant embryos after transfer to 20 oC. The induction of JA production was dependent on the extent of cold imbibition and precedes germination. Blocking JA biosynthesis with acetylsalicylic acid (ASA) inhibited the cold-stimulated germination in a dose-dependent manner. In addition, we have explored the relationship between JA and abscisic acid (ABA), a well-known dormancy promoter, in cold regulation of dormancy. We found an inverse relationship between JA and ABA content in dormant wheat embryos following stratification. ABA content decreased rapidly in response to stratification, and the decrease was reversed by addition of ASA. Our results indicate that the action of JA on cold-stratified grains is mediated by suppression of two key ABA biosynthesis genes, TaNCED1 and TaNCED2. PMID:27140440

Abscisic acid is a negative regulator of root gravitropism in Arabidopsis thaliana.

PubMed

Han, Woong; Rong, Honglin; Zhang, Hanma; Wang, Myeong-Hyeon

2009-01-23

The plant hormone abscisic acid (ABA) plays a role in root gravitropism and has led to an intense debate over whether ABA acts similar to auxin by translating the gravitational signal into directional root growth. While tremendous advances have been made in the past two decades in establishing the role of auxin in root gravitropism, little progress has been made in characterizing the role of ABA in this response. In fact, roots of plants that have undetectable levels of ABA and that display a normal gravitropic response have raised some serious doubts about whether ABA plays any role in root gravitropism. Here, we show strong evidence that ABA plays a role opposite to that of auxin and that it is a negative regulator of the gravitropic response of Arabidopsis roots.

Arabidopsis DREB2C modulates ABA biosynthesis during germination.

PubMed

Je, Jihyun; Chen, Huan; Song, Chieun; Lim, Chae Oh

2014-09-12

Plant dehydration-responsive element binding factors (DREBs) are transcriptional regulators of the APETELA2/Ethylene Responsive element-binding Factor (AP2/ERF) family that control expression of abiotic stress-related genes. We show here that under conditions of mild heat stress, constitutive overexpression seeds of transgenic DREB2C overexpression Arabidopsis exhibit delayed germination and increased abscisic acid (ABA) content compared to untransformed wild-type (WT). Treatment with fluridone, an inhibitor of the ABA biosynthesis abrogated these effects. Expression of an ABA biosynthesis-related gene, 9-cis-epoxycarotenoid dioxygenase 9 (NCED9) was up-regulated in the DREB2C overexpression lines compared to WT. DREB2C was able to trans-activate expression of NCED9 in Arabidopsis leaf protoplasts in vitro. Direct and specific binding of DREB2C to a complete DRE on the NCED9 promoter was observed in electrophoretic mobility shift assays. Exogenous ABA treatment induced DREB2C expression in germinating seeds of WT. Vegetative growth of transgenic DREB2C overexpression lines was more strongly inhibited by exogenous ABA compared to WT. These results suggest that DREB2C is a stress- and ABA-inducible gene that acts as a positive regulator of ABA biosynthesis in germinating seeds through activating NCED9 expression. Copyright © 2014 Elsevier Inc. All rights reserved.

Abscisic Acid Down-Regulates Hydraulic Conductance of Grapevine Leaves in Isohydric Genotypes Only1[OPEN

PubMed Central

Masclef, Diane; Lebon, Eric; Christophe, Angélique

2017-01-01

Plants evolved different strategies to cope with water stress. While isohydric species maintain their midday leaf water potential (ΨM) under soil water deficit by closing their stomata, anisohydric species maintain higher stomatal aperture and exhibit substantial reductions in ΨM. It was hypothesized that isohydry is related to a locally higher sensitivity of stomata to the drought-hormone abscisic acid (ABA). Interestingly, recent lines of evidence in Arabidopsis (Arabidopsis thaliana) suggested that stomatal responsiveness is also controlled by an ABA action on leaf water supply upstream from stomata. Here, we tested the possibility in grapevine (Vitis vinifera) that different genotypes ranging from near isohydric to more anisohydric may have different sensitivities in these ABA responses. Measurements on whole plants in drought conditions were combined with assays on detached leaves fed with ABA. Two different methods consistently showed that leaf hydraulic conductance (Kleaf) was down-regulated by exogenous ABA, with strong variations depending on the genotype. Importantly, variation between isohydry and anisohydry correlated with Kleaf sensitivity to ABA, with Kleaf in the most anisohydric genotypes being unresponsive to the hormone. We propose that the observed response of Kleaf to ABA may be part of the overall ABA regulation of leaf water status. PMID:28899961

Introduction to the Thematic Minireview Series: Redox metabolism and signaling.

PubMed

Banerjee, Ruma

2017-10-13

Life on oxygen predisposes cells to reactive oxygen species (ROS) generation by electron slippage in the electron transfer chain. Aerobic metabolism also generates superoxide (O 2 ̇̄ ) and hydrogen peroxide (H 2 O 2 ) as bona fide products in reactions involving 1- or 2-electron reduction of O 2 Although often viewed as dangerous, ROS are now recognized as important messengers in redox signaling pathways. A delicate balance between needed versus excessive ROS production distinguishes health from an array of disease states. A collection of provocative reviews in this thematic series discusses the relative importance of mitochondrial sites for ROS production, ROS signaling-mediated regulation of cellular stress responses and thermogenesis, and how O 2 deficiency leads to metabolic reprograming in cancer. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Regulation of necrotic cell death p53, PARP1 and Cyclophilin D -overlapping pathways of regulated necrosis?

PubMed Central

Ying, Yuan; Padanilam, Babu J.

2017-01-01

In contrast to apoptosis and autophagy, necrotic cell death was considered to be a random, passive cell death without definable mediators. However, this dogma has been challenged by recent developments suggesting that necrotic cell death can also be a regulated process. Regulated necrosis includes multiple cell death modalities such as necroptosis, parthanatos, ferroptosis, pyroptosis, and mitochondrial permeability transition pore (MPTP)-mediated necrosis. Several distinctive executive molecules, particularly residing on the mitochondrial inner and outer membrane, amalgamating to form the MPTP have been defined. The c-subunit of the F1F0ATP synthase on the inner membrane and Bax/Bak on the outer membrane are considered to be the long sought components that form the MPTP. Opening of the MPTP results in loss of mitochondrial inner membrane potential, disruption of ATP production, increased ROS production, organelle swelling, mitochondrial dysfunction and consequent necrosis. Cyclophilin D, along with adenine nucleotide translocator (ANT) and the phosphate carrier (PiC) are considered to be important regulators involved in the opening of MPTP. Increased production of ROS can further trigger other necrotic pathways mediated through molecules such as PARP1, leading to irreversible cell damage. This review examines the roles of PARP1 and cyclophilin D in necrotic cell death. The hierarchical role of p53 in regulation and integration of key components of signaling pathway to elicit MPTP-mediated necrosis and ferroptosis is explored. In the context of recent insights, the indistinct role of necroptosis signaling in tubular necrosis after ischemic kidney injury is scrutinized. We conclude by discussing the participation of p53, PARP1 and cyclophilin D and their overlapping pathways to elicit MPTP-mediated necrosis and ferroptosis in acute kidney injury. PMID:27048819

Regulation of necrotic cell death: p53, PARP1 and cyclophilin D-overlapping pathways of regulated necrosis?

PubMed

Ying, Yuan; Padanilam, Babu J

2016-06-01

In contrast to apoptosis and autophagy, necrotic cell death was considered to be a random, passive cell death without definable mediators. However, this dogma has been challenged by recent developments suggesting that necrotic cell death can also be a regulated process. Regulated necrosis includes multiple cell death modalities such as necroptosis, parthanatos, ferroptosis, pyroptosis, and mitochondrial permeability transition pore (MPTP)-mediated necrosis. Several distinctive executive molecules, particularly residing on the mitochondrial inner and outer membrane, amalgamating to form the MPTP have been defined. The c-subunit of the F1F0ATP synthase on the inner membrane and Bax/Bak on the outer membrane are considered to be the long sought components that form the MPTP. Opening of the MPTP results in loss of mitochondrial inner membrane potential, disruption of ATP production, increased ROS production, organelle swelling, mitochondrial dysfunction and consequent necrosis. Cyclophilin D, along with adenine nucleotide translocator and the phosphate carrier are considered to be important regulators involved in the opening of MPTP. Increased production of ROS can further trigger other necrotic pathways mediated through molecules such as PARP1, leading to irreversible cell damage. This review examines the roles of PARP1 and cyclophilin D in necrotic cell death. The hierarchical role of p53 in regulation and integration of key components of signaling pathway to elicit MPTP-mediated necrosis and ferroptosis is explored. In the context of recent insights, the indistinct role of necroptosis signaling in tubular necrosis after ischemic kidney injury is scrutinized. We conclude by discussing the participation of p53, PARP1 and cyclophilin D and their overlapping pathways to elicit MPTP-mediated necrosis and ferroptosis in acute kidney injury.

Cytosolic calcium mediates RIP1/RIP3 complex-dependent necroptosis through JNK activation and mitochondrial ROS production in human colon cancer cells.

PubMed

Sun, Wen; Wu, Xiaxia; Gao, Hongwei; Yu, Jie; Zhao, Wenwen; Lu, Jin-Jian; Wang, Jinhua; Du, Guanhua; Chen, Xiuping

2017-07-01

Necroptosis is a form of programmed necrosis mediated by signaling complexes with receptor-interacting protein 1 (RIP1) and RIP3 kinases as the main mediators. However, the underlying execution pathways of this phenomenon have yet to be elucidated in detail. In this study, a RIP1/RIP3 complex was formed in 2-methoxy-6-acetyl-7-methyljuglone (MAM)-treated HCT116 and HT29 colon cancer cells. With this formation, mitochondrial reactive oxygen species (ROS) levels increased, mitochondrial depolarization occurred, and ATP concentrations decreased. This process was identified as necroptosis. This finding was confirmed by experiments showing that MAM-induced cell death was attenuated by the pharmacological or genetic blockage of necroptosis signaling, including RIP1 inhibitor necrostatin-1s (Nec-1s) and siRNA-mediated gene silencing of RIP1 and RIP3, but was unaffected by caspase inhibitor z-vad-fmk or necrosis inhibitor 2-(1H-Indol-3-yl)-3-pentylamino-maleimide (IM54). Transmission electron microscopy (TEM) analysis further revealed the ultrastructural features of MAM-induced necroptosis. MAM-induced RIP1/RIP3 complex triggered necroptosis through cytosolic calcium (Ca 2+ ) accumulation and sustained c-Jun N-terminal kinase (JNK) activation. Both calcium chelator BAPTA-AM and JNK inhibitor SP600125 could attenuate necroptotic features, including mitochondrial ROS elevation, mitochondrial depolarization, and ATP depletion. 2-thenoyltrifluoroacetone (TTFA), which is a mitochondrial complex II inhibitor, was found to effectively reverse both MAM induced mitochondrial ROS generation and cell death, indicating the complex II was the ROS-producing site. The essential role of mitochondrial ROS was confirmed by the protective effect of overexpression of manganese superoxide dismutase (MnSOD). MAM-induced necroptosis was independent of TNFα, p53, MLKL, and lysosomal membrane permeabilization. In summary, our study demonstrated that RIP1/RIP3 complex-triggered cytosolic calcium accumulation is a critical mediator in MAM-induced necroptosis through sustained JNK activation and mitochondrial ROS production. Our study also provided new insights into the molecular regulation of necroptosis in human colon cancer cells. Copyright © 2017 Elsevier Inc. All rights reserved.

Group A PP2Cs evolved in land plants as key regulators of intrinsic desiccation tolerance

PubMed Central

Komatsu, Kenji; Suzuki, Norihiro; Kuwamura, Mayuri; Nishikawa, Yuri; Nakatani, Mao; Ohtawa, Hitomi; Takezawa, Daisuke; Seki, Motoaki; Tanaka, Maho; Taji, Teruaki; Hayashi, Takahisa; Sakata, Yoichi

2013-01-01

Vegetative desiccation tolerance is common in bryophytes, although this character has been lost in most vascular plants. The moss Physcomitrella patens survives complete desiccation if treated with abscisic acid (ABA). Group A protein phosphatases type 2C (PP2C) are negative regulators of abscisic acid signalling. Here we show that the elimination of Group A PP2C is sufficient to ensure P. patens survival to full desiccation, without ABA treatment, although its growth is severely hindered. Microarray analysis shows that the Group A PP2C-regulated genes exclusively overlap with genes exhibiting a high level of ABA induction. Group A PP2C disruption weakly affects ABA-activated kinase activity, indicating Group A PP2C action downstream of these kinases in the moss. We propose that Group A PP2C emerged in land plants to repress desiccation tolerance mechanisms, possibly facilitating plants propagation on land, whereas ABA releases the intrinsic desiccation tolerance from Group A PP2C regulation. PMID:23900426

Activation of the Liver X Receptor by Agonist TO901317 Improves Hepatic Insulin Resistance via Suppressing Reactive Oxygen Species and JNK Pathway.

PubMed

Dong, Ying; Gao, Guirong; Fan, Hongyan; Li, Shengxian; Li, Xuhang; Liu, Wei

2015-01-01

Activation of Liver X receptors (LXRs), key transcriptional regulators of glucose metabolism, normalizes glycemia and improves insulin sensitivity in rodent models with insulin resistance. However, the molecular mechanism is unclear. This study is aimed to elucidate the mechanism of LXRs-mediated liver glucose metabolic regulation in vitro and in vivo. Db/db mice were used as an in vivo model of diabetes; palmitate (PA)-stimulated HepG2 cells were used as an in vitro cell model with impairment of insulin signaling. TO901317 (TO) was chosen as the LXRs agonist. We demonstrated that TO treatment for 14 days potently improved the hepatic glucose metabolism in db/db mice, including fasting blood glucose, fasting insulin level, and HOMA-IR. TO had no effect on the glucose metabolism in normal WT mice. TO-mediated activation of hepatic LXRs led to strong inhibition of ROS production accompanied by inactivation of JNK pathway and re-activation of Akt pathway. TO also suppressed the expression of gluconeogenic genes such as PEPCK and G-6-pase in db/db mice, but not in WT mice. In HepG2 cells, TO almost completely restored PA-induced Akt inactivation, and suppressed PA-stimulated ROS production and JNK activation. Interestingly, basal level of ROS was also inhibited by TO in HepG2 cells. TO significantly inhibited PA-stimulated expressions of gluconeogenic genes. Finally, we found that anti-oxidative genes, such as Nrf2, were up-regulated after LXRs activation by TO. These results strongly support the notion that activation of LXRs is critical in suppression of liver gluconeogenesis and improvement of insulin sensitivity in diabetic individuals. At molecular levels, the mode of action appears to be as fellows: under diabetic condition, ROS production is increased, JNK is activated, and Akt activity is inhibited; TO-mediated LXR activation potently inhibits ROS production, increases anti-oxidative gene expressions, suppresses JNK activation, and restores Akt activity. Our data provide new evidence to support LXRs as promising therapeutic targets for anti-diabetic drug development.

The Structure of Arabidopsis thaliana OST1 Provides Insights into the Kinase Regulation Mechanism in Response to Osmotic Stress

PubMed Central

Yunta, Cristina; Martínez-Ripoll, Martín; Zhu, Jian-Kang; Albert, Armando

2013-01-01

SnRK [SNF1 (sucrose non-fermenting-1)-related protein kinase] 2.6 [open stomata 1 (OST1)] is well characterized at molecular and physiological levels to control stomata closure in response to water-deficit stress. OST1 is a member of a family of 10 protein kinases from Arabidopsis thaliana (SnRK2) that integrates abscisic acid (ABA)-dependent and ABA-independent signals to coordinate the cell response to osmotic stress. A subgroup of protein phosphatases type 2C binds OST1 and keeps the kinase dephosphorylated and inactive. Activation of OST1 relies on the ABA-dependent inhibition of the protein phosphatases type 2C and the subsequent self-phosphorylation of the kinase. The OST1 ABA-independent activation depends on a short sequence motif that is conserved among all the members of the SnRK2 family. However, little is known about the molecular mechanism underlying this regulation. The crystallographic structure of OST1 shows that ABA-independent regulation motif stabilizes the conformation of the kinase catalytically essential α C helix, and it provides the basis of the ABA-independent regulation mechanism for the SnRK2 family of protein kinases. PMID:21983340

Jacalin Lectin At5g28520 Is Regulated By ABA and miR846

PubMed Central

Jia, Fan; Rock, Christopher D.

2013-01-01

Plant microRNAs (miRNAs) are important regulators of development and stress responses and are oftentimes under transcriptional regulation by stresses and plant hormones. We recently showed that polycistronic MIR842 and MIR846 are expressed from the same primary transcript which is subject to alternative splicing. ABA treatment affects the alternative splicing of the primary cistronic transcript which results in differential expression of the two miRNAs that are predicted to target the same family of jacalin lectin genes. One variant of miR846 in roots can direct the cleavage of AT5G28520, which is also highly upregulated by ABA in roots. In this addendum, we present additional results further supporting the regulation of AT5G28520 by MIR846 using a T-DNA insertion line mapping upstream of MIR842 and MIR846. We also show that AT5G28520 is transcriptionally induced by ABA and this induction is subject to ABA signaling effectors in seedlings. Based on previous results and data presented in this paper, we propose an interaction loop between MIR846, AT5G28520 and ABA in roots. PMID:23603955

Transcriptional regulation of abscisic acid signal core components during cucumber seed germination and under Cu²⁺, Zn²⁺, NaCl and simulated acid rain stresses.

PubMed

Wang, Yanping; Wang, Ya; Kai, Wenbin; Zhao, Bo; Chen, Pei; Sun, Liang; Ji, Kai; Li, Qian; Dai, Shengjie; Sun, Yufei; Wang, Yidong; Pei, Yuelin; Leng, Ping

2014-03-01

Abscisic acid (ABA) is an important phytohormone that regulates lots of physiological and biochemical processes in plant life cycle, especially in seed germination and stress responses. For exploring the transcriptional regulation of ABA signal transduction during cucumber (Cucumis sativus L.) seed germination and under Cu(2+), Zn(2+), NaCl and simulated acid rain stresses, nine CsPYLs, three group A CsPP2Cs and two subclass III CsSnRK2s were identified from cucumber genome, which respectively showed high sequence similarities and highly conserved domains with homologous genes in Arabidopsis. Based on Real-time PCR analysis, most of the tested genes' expression decreased during cucumber seed germination, which was in accordance with the ABA level variation. In addition, according to the absolute expression, CsPYL1, CsPYL3, CsPP2C5, CsABI1, CsSnRK2.3 and CsSnRK2.4 were highly expressed, indicating that they may play more important roles in ABA signaling during cucumber seed germination. Moreover, most of these highly expressed genes, except CsPYL3, were up-regulated by ABA treatment. Meanwhile, most of the tested genes' expression dramatically changed at the initial water uptake phase, indicating that this period may be critical in the regulation of ABA on seed germination. Under Cu(2+), Zn(2+), NaCl and simulated acid rain stresses, cucumber seed germination percentage decreased and ABA content increased. Meanwhile, the expression of ABA signal transduction core components genes showed specific response to a particular stress and was not always consist with ABA variation. Generally, the expression of CsPYL1, CsPYL3, CsABI1, CsSnRK2.3 and CsSnRK2.4 was sensitive to 120 mM NaCl and 0.5 mM Cu(2+) treatments. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Putrescine Is Involved in Arabidopsis Freezing Tolerance and Cold Acclimation by Regulating Abscisic Acid Levels in Response to Low Temperature1

PubMed Central

Cuevas, Juan C.; López-Cobollo, Rosa; Alcázar, Rubén; Zarza, Xavier; Koncz, Csaba; Altabella, Teresa; Salinas, Julio; Tiburcio, Antonio F.; Ferrando, Alejandro

2008-01-01

The levels of endogenous polyamines have been shown to increase in plant cells challenged with low temperature; however, the functions of polyamines in the regulation of cold stress responses are unknown. Here, we show that the accumulation of putrescine under cold stress is essential for proper cold acclimation and survival at freezing temperatures because Arabidopsis (Arabidopsis thaliana) mutants defective in putrescine biosynthesis (adc1, adc2) display reduced freezing tolerance compared to wild-type plants. Genes ADC1 and ADC2 show different transcriptional profiles upon cold treatment; however, they show similar and redundant contributions to cold responses in terms of putrescine accumulation kinetics and freezing sensitivity. Our data also demonstrate that detrimental consequences of putrescine depletion during cold stress are due, at least in part, to alterations in the levels of abscisic acid (ABA). Reduced expression of NCED3, a key gene involved in ABA biosynthesis, and down-regulation of ABA-regulated genes are detected in both adc1 and adc2 mutant plants under cold stress. Complementation analysis of adc mutants with ABA and reciprocal complementation tests of the aba2-3 mutant with putrescine support the conclusion that putrescine controls the levels of ABA in response to low temperature by modulating ABA biosynthesis and gene expression. PMID:18701673

Stomatal VPD Response: There Is More to the Story Than ABA.

PubMed

Merilo, Ebe; Yarmolinsky, Dmitry; Jalakas, Pirko; Parik, Helen; Tulva, Ingmar; Rasulov, Bakhtier; Kilk, Kalle; Kollist, Hannes

2018-01-01

Guard cells shrink and close stomatal pores when air humidity decreases (i.e. when the difference between the vapor pressures of leaf and atmosphere [VPD] increases). The role of abscisic acid (ABA) in VPD-induced stomatal closure has been studied using ABA-related mutants that respond to VPD in some studies and not in others. The importance of ABA biosynthesis in guard cells versus vasculature for whole-plant stomatal regulation is unclear as well. Here, we show that Arabidopsis ( Arabidopsis thaliana ) lines carrying mutations in different steps of ABA biosynthesis as well as pea ( Pisum sativum ) wilty and tomato ( Solanum lycopersicum ) flacca ABA-deficient mutants had higher stomatal conductance compared with wild-type plants. To characterize the role of ABA production in different cells, we generated transgenic plants where ABA biosynthesis was rescued in guard cells or phloem companion cells of an ABA-deficient mutant. In both cases, the whole-plant stomatal conductance, stunted growth phenotype, and leaf ABA level were restored to wild-type values, pointing to the redundancy of ABA sources and to the effectiveness of leaf ABA transport. All ABA-deficient lines closed their stomata rapidly and extensively in response to high VPD, whereas plants with mutated protein kinase OST1 showed stunted VPD-induced responses. Another strongly ABA-insensitive mutant, defective in the six ABA PYR/RCAR receptors, responded to changes in VPD in both directions strongly and symmetrically, indicating that its VPD-induced closure could be passive hydraulic. We discuss that both the VPD-induced passive hydraulic stomatal closure and the stomatal VPD regulation of ABA-deficient mutants may be conditional on the initial pretreatment stomatal conductance. © 2018 American Society of Plant Biologists. All Rights Reserved.

RhHB1 mediates the antagonism of gibberellins to ABA and ethylene during rose (Rosa hybrida) petal senescence.

PubMed

Lü, Peitao; Zhang, Changqing; Liu, Jitao; Liu, Xiaowei; Jiang, Guimei; Jiang, Xinqiang; Khan, Muhammad Ali; Wang, Liangsheng; Hong, Bo; Gao, Junping

2014-05-01

Rose (Rosa hybrida) is one of the most important ornamental plants worldwide; however, senescence of its petals terminates the ornamental value of the flower, resulting in major economic loss. It is known that the hormones abscisic acid (ABA) and ethylene promote petal senescence, while gibberellins (GAs) delay the process. However, the molecular mechanisms underlying the antagonistic effects amongst plant hormones during petal senescence are still unclear. Here we isolated RhHB1, a homeodomain-leucine zipper I transcription factor gene, from rose flowers. Quantitative RT-PCR and GUS reporter analyses showed that RhHB1 was strongly expressed in senescing petals, and its expression was induced by ABA or ethylene in petals. ABA or ethylene treatment clearly accelerated rose petal senescence, while application of the gibberellin GA3 delayed the process. However, silencing of RhHB1 delayed the ABA- or ethylene-mediated senescence, and resulted in higher petal anthocyanin levels and lower expression of RhSAG12. Moreover, treatment with paclobutrazol, an inhibitor of GA biosynthesis, repressed these delays. In addition, silencing of RhHB1 blocked the ABA- or ethylene-induced reduction in expression of the GA20 oxidase encoded by RhGA20ox1, a gene in the GA biosynthetic pathway. Furthermore, RhHB1 directly binds to the RhGA20ox1 promoter, and silencing of RhGA20ox1 promoted petal senescence. Eight senescence-related genes showed substantial differences in expression in petals after treatment with GA3 or paclobutrazol. These results suggest that RhHB1 mediates the antagonistic effect of GAs on ABA and ethylene during rose petal senescence, and that the promotion of petal senescence by ABA or ethylene operates through an RhHB1-RhGA20ox1 regulatory checkpoint. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

Proteomic analysis reveals differential accumulation of small heat shock proteins and late embryogenesis abundant proteins between ABA-deficient mutant vp5 seeds and wild-type Vp5 seeds in maize

PubMed Central

Wu, Xiaolin; Gong, Fangping; Yang, Le; Hu, Xiuli; Tai, Fuju; Wang, Wei

2014-01-01

ABA is a major plant hormone that plays important roles during many phases of plant life cycle, including seed development, maturity and dormancy, and especially the acquisition of desiccation tolerance. Understanding of the molecular basis of ABA-mediated plant response to stress is of interest not only in basic research on plant adaptation but also in applied research on plant productivity. Maize mutant viviparous-5 (vp5), deficient in ABA biosynthesis in seeds, is a useful material for studying ABA-mediated response in maize. Due to carotenoid deficiency, vp5 endosperm is white, compared to yellow Vp5 endosperm. However, the background difference at proteome level between vp5 and Vp5 seeds is unclear. This study aimed to characterize proteome alterations of maize vp5 seeds and to identify ABA-dependent proteins during seed maturation. We compared the embryo and endosperm proteomes of vp5 and Vp5 seeds by gel-based proteomics. Up to 46 protein spots, most in embryos, were found to be differentially accumulated between vp5 and Vp5. The identified proteins included small heat shock proteins (sHSPs), late embryogenesis abundant (LEA) proteins, stress proteins, storage proteins and enzymes among others. However, EMB564, the most abundant LEA protein in maize embryo, accumulated in comparable levels between vp5 and Vp5 embryos, which contrasted to previously characterized, greatly lowered expression of emb564 mRNA in vp5 embryos. Moreover, LEA proteins and sHSPs displayed differential accumulations in vp5 embryos: six out of eight identified LEA proteins decreased while nine sHSPs increased in abundance. Finally, we discussed the possible causes of global proteome alterations, especially the observed differential accumulation of identified LEA proteins and sHSPs in vp5 embryos. The data derived from this study provides new insight into ABA-dependent proteins and ABA-mediated response during maize seed maturation. PMID:25653661

Reactive Oxygen Species-Mediated Cellular Stress Response and Lipid Accumulation in Oleaginous Microorganisms: The State of the Art and Future Perspectives

PubMed Central

Shi, Kun; Gao, Zhen; Shi, Tian-Qiong; Song, Ping; Ren, Lu-Jing; Huang, He; Ji, Xiao-Jun

2017-01-01

Microbial oils, which are mainly extracted from yeasts, molds, and algae, have been of considerable interest as food additives and biofuel resources due to their high lipid content. While these oleaginous microorganisms generally produce only small amounts of lipids under optimal growth conditions, their lipid accumulation machinery can be induced by environmental stresses, such as nutrient limitation and an inhospitable physical environmental. As common second messengers of many stress factors, reactive oxygen species (ROS) may act as a regulator of cellular responses to extracellular environmental signaling. Furthermore, increasing evidence indicates that ROS may act as a mediator of lipid accumulation, which is associated with dramatic changes in the transcriptome, proteome, and metabolome. However, the specific mechanisms of ROS involvement in the crosstalk between extracellular stress signaling and intracellular lipid synthesis require further investigation. Here, we summarize current knowledge on stress-induced lipid biosynthesis and the putative role of ROS in the control of lipid accumulation in oleaginous microorganisms. Understanding such links may provide guidance for the development of stress-based strategies to enhance microbial lipid production. PMID:28507542

Vascular Cell Adhesion Molecule-1 Expression and Signaling During Disease: Regulation by Reactive Oxygen Species and Antioxidants

PubMed Central

Marchese, Michelle E.; Abdala-Valencia, Hiam

2011-01-01

Abstract The endothelium is immunoregulatory in that inhibiting the function of vascular adhesion molecules blocks leukocyte recruitment and thus tissue inflammation. The function of endothelial cells during leukocyte recruitment is regulated by reactive oxygen species (ROS) and antioxidants. In inflammatory sites and lymph nodes, the endothelium is stimulated to express adhesion molecules that mediate leukocyte binding. Upon leukocyte binding, these adhesion molecules activate endothelial cell signal transduction that then alters endothelial cell shape for the opening of passageways through which leukocytes can migrate. If the stimulation of this opening is blocked, inflammation is blocked. In this review, we focus on the endothelial cell adhesion molecule, vascular cell adhesion molecule-1 (VCAM-1). Expression of VCAM-1 is induced on endothelial cells during inflammatory diseases by several mediators, including ROS. Then, VCAM-1 on the endothelium functions as both a scaffold for leukocyte migration and a trigger of endothelial signaling through NADPH oxidase-generated ROS. These ROS induce signals for the opening of intercellular passageways through which leukocytes migrate. In several inflammatory diseases, inflammation is blocked by inhibition of leukocyte binding to VCAM-1 or by inhibition of VCAM-1 signal transduction. VCAM-1 signal transduction and VCAM-1-dependent inflammation are blocked by antioxidants. Thus, VCAM-1 signaling is a target for intervention by pharmacological agents and by antioxidants during inflammatory diseases. This review discusses ROS and antioxidant functions during activation of VCAM-1 expression and VCAM-1 signaling in inflammatory diseases. Antioxid. Redox Signal. 15, 1607–1638. PMID:21050132

Abscisic acid-dependent regulation of small rubber particle protein gene expression in Taraxacum brevicorniculatum is mediated by TbbZIP1.

PubMed

Fricke, Julia; Hillebrand, Andrea; Twyman, Richard M; Prüfer, Dirk; Schulze Gronover, Christian

2013-04-01

Natural rubber is a high-molecular-mass biopolymer found in the latex of >2,500 plant species, including Hevea brasiliensis, Parthenium argentatum and Taraxacum spp. The active sites of rubber biosynthesis are rubber particles, which comprise a hydrophobic rubber core surrounded by a phospholipid monolayer membrane containing species-dependent lipids and associated proteins. Small rubber particle proteins are the most abundant rubber particle-associated proteins in Taraxacum brevicorniculatum (TbSRPPs) and may promote rubber biosynthesis by stabilizing the rubber particle architecture. We investigated the transcriptional regulation of genes encoding SRPPs and identified a bZIP transcription factor (TbbZIP.1) similar to the Arabidopsis thaliana ABI5-ABF-AREB subfamily, which is thought to include downstream targets of ABA and/or abiotic stress-inducible protein kinases. The TbbZIP.1 gene was predominantly expressed in laticifers and regulates the expression of TbSRPP genes in an ABA-dependent manner. The individual TbSRPP genes showed distinct induction profiles, suggesting diverse roles in rubber biosynthesis and stress adaptation. The potential involvement of TbSRPPs in the adaptation of T. brevicorniculatum plants to environmental stress is discussed based on our current knowledge of the stress-response roles of SRPPs and their homologs, and the protective function of latex and rubber against pathogens. Our data suggest that TbSRPPs contribute to stress tolerance in T. brevicorniculatum and that their effects are mediated by TbbZIP.1.

Surviving a Dry Future: Abscisic Acid (ABA)-Mediated Plant Mechanisms for Conserving Water under Low Humidity

PubMed Central

McAdam, Scott A. M.

2017-01-01

Angiosperms are able to respond rapidly to the first sign of dry conditions, a decrease in air humidity, more accurately described as an increase in the vapor pressure deficit between the leaf and the atmosphere (VPD), by abscisic acid (ABA)-mediated stomatal closure. The genes underlying this response offer valuable candidates for targeted selection of crop varieties with improved drought tolerance, a critical goal for current plant breeding programs, to maximize crop production in drier and increasingly marginalized environments, and meet the demands of a growing population in the face of a changing climate. Here, we review current understanding of the genetic mechanisms underpinning ABA-mediated stomatal closure, a key means for conserving water under dry conditions, examine how these mechanisms evolved, and discuss what remains to be investigated. PMID:29113039

Arabidopsis WRKY6 Transcription Factor Acts as a Positive Regulator of Abscisic Acid Signaling during Seed Germination and Early Seedling Development

PubMed Central

Wu, Wei-Hua; Chen, Yi-Fang

2016-01-01

The phytohormone abscisic acid (ABA) plays important roles during seed germination and early seedling development. Here, we characterized the function of the Arabidopsis WRKY6 transcription factor in ABA signaling. The transcript of WRKY6 was repressed during seed germination and early seedling development, and induced by exogenous ABA. The wrky6-1 and wrky6-2 mutants were ABA insensitive, whereas WRKY6-overexpressing lines showed ABA-hypersensitive phenotypes during seed germination and early seedling development. The expression of RAV1 was suppressed in the WRKY6-overexpressing lines and elevated in the wrky6 mutants, and the expression of ABI3, ABI4, and ABI5, which was directly down-regulated by RAV1, was enhanced in the WRKY6-overexpressing lines and repressed in the wrky6 mutants. Electrophoretic mobility shift and chromatin immunoprecipitation assays showed that WRKY6 could bind to the RAV1 promoter in vitro and in vivo. Overexpression of RAV1 in WRKY6-overexpressing lines abolished their ABA-hypersensitive phenotypes, and the rav1 wrky6-2 double mutant showed an ABA-hypersensitive phenotype, similar to rav1 mutant. Together, the results demonstrated that the Arabidopsis WRKY6 transcription factor played important roles in ABA signaling by directly down-regulating RAV1 expression. PMID:26829043

Brachypodium distachyon BdPP2CA6 Interacts with BdPYLs and BdSnRK2 and Positively Regulates Salt Tolerance in Transgenic Arabidopsis

PubMed Central

Zhang, Fan; Wei, Qiuhui; Shi, Jiaochun; Jin, Xia; He, Yuan; Zhang, Yang; Luo, Qingchen; Wang, Yuesheng; Chang, Junli; Yang, Guangxiao; He, Guangyuan

2017-01-01

The phytohormone abscisic acid (ABA) is essential in plant responding to biotic and abiotic stresses. Although ABA signaling model is well established in Arabidopsis, ABA receptor PYL family and clade A PP2C subfamily are not yet characterized in monocot model plant Brachypodium distachyon. In this study, we identified 12 PYLs and 8 clade A PP2Cs from B. distachyon genome and successfully cloned 12 PYLs and 7 clade A PP2Cs. Bioinformatic and expression analyses showed that most of the identified genes respond to several signal molecules and abiotic stresses. Protein–protein interaction analysis revealed that many BdPYLs and BdPP2CAs participate in the classic ABA-PYL-PP2C-SnRK2 signaling pathway. A clade A PP2C, designated BdPP2CA6, interacted with BdPYL11 in the absence of ABA and localized in nucleus. Most clade A PP2C members from Arabidopsis showed negatively regulation in ABA signaling pathway, whereas BdPP2CA6-overexpression transgenic Arabidopsis showed ABA hypersensitive phenotype, resulting in enhanced stomatal closure and salinity tolerance. Our results indicate that BdPP2CA6 positively regulates ABA and stress signal pathway in transgenic Arabidopsis plant seedlings. PMID:28293246

Connexin32 plays a crucial role in ROS-mediated endoplasmic reticulum stress apoptosis signaling pathway in ischemia reperfusion-induced acute kidney injury.

PubMed

Gu, Yu; Huang, Fei; Wang, Yanling; Chen, Chaojin; Wu, Shan; Zhou, Shaoli; Hei, Ziqing; Yuan, Dongdong

2018-05-04

Ischemia-reperfusion (I/R)-induced acute kidney injury (AKI) not only prolongs the length of hospital stay, but also seriously affects the patient's survival rate. Although our previous investigation has verified that reactive oxygen species (ROS) transferred through gap junction composed of connexin32 (Cx32) contributed to AKI, its underlying mechanisms were not fully understood and viable preventive or therapeutic regimens were still lacking. Among various mechanisms involved in organs I/R-induced injuries, endoplasmic reticulum stress (ERS)-related apoptosis is currently considered to be an important participant. Thus, in present study, we focused on the underlying mechanisms of I/R-induced AKI, and postulated that Cx32 mediated ROS/ERS/apoptosis signal pathway activation played an important part in I/R-induced AKI. We established renal I/R models with Cx32 +/+ and Cx32 -/- mice, which underwent double kidneys clamping and recanalization. ROS scavenger (N-acetylcysteine, NAC) and ERS inhibitors (4-phenyl butyric acid, 4-PBA, and tauroursodeoxycholic acid, TUDCA) were used to decrease the content of ROS and attenuate ERS activation, respectively. Renal damage was progressively exacerbated in a time-dependent manner at the reperfusion stage, that was consistent with the alternation of ERS activation, including glucose regulated protein 78 (BiP/GRP78), X box-binding protein1, and C/EBP homologous protein expression. TUDCA or 4-PBA application attenuated I/R-induced ERS activation and protected against renal tubular epithelial cells apoptosis and renal damage. Cx32 deficiency decreased ROS generation and distribution between the neighboring cells, which attenuated I/R-induced ERS activation, and improved cell apoptosis and renal damage. Cx32 mediated ROS/ERS/apoptosis signal pathway activation played an important part in I/R-induced AKI. Cx32 deficiency, ROS elimination, and ERS inhibition all could protect against I/R-induced AKI.

Molecular Mimicry Regulates ABA Signaling by SnRK2 Kinases and PP2C Phosphatases

PubMed Central

Soon, Fen-Fen; Ng, Ley-Moy; Zhou, X. Edward; West, Graham M.; Kovach, Amanda; Tan, M. H. Eileen; Suino-Powell, Kelly M.; He, Yuanzheng; Xu, Yong; Chalmers, Michael J.; Brunzelle, Joseph S.; Zhang, Huiming; Yang, Huaiyu; Jiang, Hualiang; Li, Jun; Yong, Eu-Leong; Cutler, Sean; Zhu, Jian-Kang; Griffin, Patrick R.; Melcher, Karsten; Xu, H. Eric

2013-01-01

Abscisic acid (ABA) is an essential hormone for plants to survive environmental stresses. At the center of the ABA signaling network is a subfamily of type 2C protein phosphatases (PP2Cs), which form exclusive interactions with ABA receptors and subfamily 2 Snfl-related kinase (SnRK2s). Here, we report a SnRK2-PP2C complex structure, which reveals marked similarity in PP2C recognition by SnRK2 and ABA receptors. In the complex, the kinase activation loop docks into the active site of PP2C, while the conserved ABA-sensing tryptophan of PP2C inserts into the kinase catalytic cleft, thus mimicking receptor-PP2C interactions. These structural results provide a simple mechanism that directly couples ABA binding to SnRK2 kinase activation and highlight a new paradigm of kinase-phosphatase regulation through mutual packing of their catalytic sites. PMID:22116026

Molecular Mimicry Regulates ABA Signaling by SnRK2 Kinases and PP2C Phosphatases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soon, Fen-Fen; Ng, Ley-Moy; Zhou, X. Edward

Abscisic acid (ABA) is an essential hormone for plants to survive environmental stresses. At the center of the ABA signaling network is a subfamily of type 2C protein phosphatases (PP2Cs), which form exclusive interactions with ABA receptors and subfamily 2 Snfl-related kinase (SnRK2s). Here, we report a SnRK2-PP2C complex structure, which reveals marked similarity in PP2C recognition by SnRK2 and ABA receptors. In the complex, the kinase activation loop docks into the active site of PP2C, while the conserved ABA-sensing tryptophan of PP2C inserts into the kinase catalytic cleft, thus mimicking receptor-PP2C interactions. These structural results provide a simple mechanismmore » that directly couples ABA binding to SnRK2 kinase activation and highlight a new paradigm of kinase-phosphatase regulation through mutual packing of their catalytic sites.« less

Anti-transpirant activity in xylem sap from flooded tomato (Lycopersicon esculentum Mill.) plants is not due to pH-mediated redistributions of root- or shoot-sourced ABA.

PubMed

Else, Mark A; Taylor, June M; Atkinson, Christopher J

2006-01-01

In flooded soils, the rapid effects of decreasing oxygen availability on root metabolic activity are likely to generate many potential chemical signals that may impact on stomatal apertures. Detached leaf transpiration tests showed that filtered xylem sap, collected at realistic flow rates from plants flooded for 2 h and 4 h, contained one or more factors that reduced stomatal apertures. The closure could not be attributed to increased root output of the glucose ester of abscisic acid (ABA-GE), since concentrations and deliveries of ABA conjugates were unaffected by soil flooding. Although xylem sap collected from the shoot base of detopped flooded plants became more alkaline within 2 h of flooding, this rapid pH change of 0.5 units did not alter partitioning of root-sourced ABA sufficiently to prompt a transient increase in xylem ABA delivery. More shoot-sourced ABA was detected in the xylem when excised petiole sections were perfused with pH 7 buffer, compared with pH 6 buffer. Sap collected from the fifth oldest leaf of "intact" well-drained plants and plants flooded for 3 h was more alkaline, by approximately 0.4 pH units, than sap collected from the shoot base. Accordingly, xylem [ABA] was increased 2-fold in sap collected from the fifth oldest petiole compared with the shoot base of flooded plants. However, water loss from transpiring, detached leaves was not reduced when the pH of the feeding solution containing 3-h-flooded [ABA] was increased from 6.7 to 7.1 Thus, the extent of the pH-mediated, shoot-sourced ABA redistribution was not sufficient to raise xylem [ABA] to physiologically active levels. Using a detached epidermis bioassay, significant non-ABA anti-transpirant activity was also detected in xylem sap collected at intervals during the first 24 h of soil flooding.

The Citrus ABA signalosome: identification and transcriptional regulation during sweet orange fruit ripening and leaf dehydration.

PubMed

Romero, Paco; Lafuente, María T; Rodrigo, María J

2012-08-01

The abscisic acid (ABA) signalling core in plants include the cytosolic ABA receptors (PYR/PYL/RCARs), the clade-A type 2C protein phosphatases (PP2CAs), and the subclass III SNF1-related protein kinases 2 (SnRK2s). The aim of this work was to identify these ABA perception system components in sweet orange and to determine the influence of endogenous ABA on their transcriptional regulation during fruit development and ripening, taking advantage of the comparative analysis between a wild-type and a fruit-specific ABA-deficient mutant. Transcriptional changes in the ABA signalosome during leaf dehydration were also studied. Six PYR/PYL/RCAR, five PP2CA, and two subclass III SnRK2 genes, homologous to those of Arabidopsis, were identified in the Citrus genome. The high degree of homology and conserved motifs for protein folding and for functional activity suggested that these Citrus proteins are bona fide core elements of ABA perception in orange. Opposite expression patterns of CsPYL4 and CsPYL5 and ABA accumulation were found during ripening, although there were few differences between varieties. In contrast, changes in expression of CsPP2CA genes during ripening paralleled those of ABA content and agreeed with the relevant differences between wild-type and mutant fruit transcript accumulation. CsSnRK2 gene expression continuously decreased with ripening and no remarkable differences were found between cultivars. Overall, dehydration had a minor effect on CsPYR/PYL/RCAR and CsSnRK2 expression in vegetative tissue, whereas CsABI1, CsAHG1, and CsAHG3 were highly induced by water stress. The global results suggest that responsiveness to ABA changes during citrus fruit ripening, and leaf dehydration was higher in the CsPP2CA gene negative regulators than in the other ABA signalosome components.

The Citrus ABA signalosome: identification and transcriptional regulation during sweet orange fruit ripening and leaf dehydration

PubMed Central

Rodrigo, María J.

2012-01-01

The abscisic acid (ABA) signalling core in plants include the cytosolic ABA receptors (PYR/PYL/RCARs), the clade-A type 2C protein phosphatases (PP2CAs), and the subclass III SNF1-related protein kinases 2 (SnRK2s). The aim of this work was to identify these ABA perception system components in sweet orange and to determine the influence of endogenous ABA on their transcriptional regulation during fruit development and ripening, taking advantage of the comparative analysis between a wild-type and a fruit-specific ABA-deficient mutant. Transcriptional changes in the ABA signalosome during leaf dehydration were also studied. Six PYR/PYL/RCAR, five PP2CA, and two subclass III SnRK2 genes, homologous to those of Arabidopsis, were identified in the Citrus genome. The high degree of homology and conserved motifs for protein folding and for functional activity suggested that these Citrus proteins are bona fide core elements of ABA perception in orange. Opposite expression patterns of CsPYL4 and CsPYL5 and ABA accumulation were found during ripening, although there were few differences between varieties. In contrast, changes in expression of CsPP2CA genes during ripening paralleled those of ABA content and agreeed with the relevant differences between wild-type and mutant fruit transcript accumulation. CsSnRK2 gene expression continuously decreased with ripening and no remarkable differences were found between cultivars. Overall, dehydration had a minor effect on CsPYR/PYL/RCAR and CsSnRK2 expression in vegetative tissue, whereas CsABI1, CsAHG1, and CsAHG3 were highly induced by water stress. The global results suggest that responsiveness to ABA changes during citrus fruit ripening, and leaf dehydration was higher in the CsPP2CA gene negative regulators than in the other ABA signalosome components. PMID:22888124

Reciprocal regulation of TGF-β and reactive oxygen species: A perverse cycle for fibrosis

PubMed Central

Liu, Rui-Ming; Desai, Leena P.

2015-01-01

Transforming growth factor beta (TGF-β) is the most potent pro-fibrogenic cytokine and its expression is increased in almost all of fibrotic diseases. Although signaling through Smad pathway is believed to play a central role in TGF-β's fibrogenesis, emerging evidence indicates that reactive oxygen species (ROS) modulate TGF-β's signaling through different pathways including Smad pathway. TGF-β1 increases ROS production and suppresses antioxidant enzymes, leading to a redox imbalance. ROS, in turn, induce/activate TGF-β1 and mediate many of TGF-β's fibrogenic effects, forming a vicious cycle (see graphic flow chart on the right). Here, we review the current knowledge on the feed-forward mechanisms between TGF-β1 and ROS in the development of fibrosis. Therapeutics targeting TGF-β-induced and ROS-dependent cellular signaling represents a novel approach in the treatment of fibrotic disorders. PMID:26496488

SR/ER-mitochondrial local communication: Calcium and ROS

PubMed Central

Csordás, György; Hajnóczky, György

2009-01-01

Mitochondria form junctions with the sarco/endoplasmic reticulum (SR/ER), which support signal transduction and biosynthetic pathways and affect organellar distribution. Recently, these junctions have received attention because of their pivotal role in mediating calcium signal propagation to the mitochondria, which is important for both ATP production and mitochondrial cell death. Many of the SR/ER-mitochondrial calcium transporters and signaling proteins are sensitive to redox regulation and are directly exposed to the reactive oxygen species (ROS) produced in the mitochondria and SR/ER. Although ROS has been emerging as a novel signaling entity, the redox signaling of the SR/ER-mitochondrial interface is yet to be elucidated. We describe here possible mechanisms of the mutual interaction between local Ca2+ and ROS signaling in the control of SR/ER-mitochondrial function. PMID:19527680

Loss of Sirt3 Limits Bone Marrow Cell-Mediated Angiogenesis and Cardiac Repair in Post-Myocardial Infarction

PubMed Central

Zeng, Heng; Li, Lanfang; Chen, Jian-Xiong

2014-01-01

Sirtuin-3 (Sirt3) has a critical role in the regulation of human aging and reactive oxygen species (ROS) formation. A recent study has identified Sirt3 as an essential regulator of stem cell aging. This study investigated whether Sirt3 is necessary for bone marrow cell (BMC)-mediated cardiac repair in post-myocardial infarction (MI). In vitro, BMC-derived endothelial progenitor cells (EPCs) from wild type (WT) and Sirt3KO mice were cultured. EPC angiogenesis, ROS formation and apoptosis were assessed. In vivo, WT and Sirt3 KO mice were subjected to MI and BMCs from WT and Sirt3 KO mice were injected into ischemic area immediately. The expression of VEGF and VEGFR2 was reduced in Sirt3KO-EPCs. Angiogenic capacities and colony formation were significantly impaired in Sirt3KO-EPCs compared to WT-EPCs. Loss of Sirt3 further enhanced ROS formation and apoptosis in EPCs. Overexpression of Sirt3 or treatment with NADPH oxidase inhibitor apocynin (Apo, 200 and 400 microM) rescued these abnormalities. In post-MI mice, BMC treatment increased number of Sca1+/c-kit+ cells; enhanced VEGF expression and angiogenesis whereas Sirt3KO-BMC treatment had little effects. BMC treatment also attenuated NADPH oxidase subunits p47phox and gp91phox expression, and significantly reduced ROS formation, apoptosis, fibrosis and hypertrophy in post-MI mice. Sirt3KO-BMC treatment did not display these beneficial effects. In contrast, Sirt3KO mice treated with BMCs from WT mice attenuated myocardial apoptosis, fibrosis and improved cardiac function. Our data demonstrate that Sirt3 is essential for BMC therapy; and loss of Sirt3 limits BMC-mediated angiogenesis and cardiac repair in post-MI. PMID:25192254

Protective Effects of N-Acetyl Cysteine against Diesel Exhaust Particles-Induced Intracellular ROS Generates Pro-Inflammatory Cytokines to Mediate the Vascular Permeability of Capillary-Like Endothelial Tubes

PubMed Central

Tseng, Chia-Yi; Chang, Jing-Fen; Wang, Jhih-Syuan; Chang, Yu-Jung; Gordon, Marion K.; Chao, Ming-Wei

2015-01-01

Exposure to diesel exhaust particles (DEP) is associated with pulmonary and cardiovascular diseases. Previous studies using in vitro endothelial tubes as a simplified model of capillaries have found that DEP-induced ROS increase vascular permeability with rearrangement or internalization of adherens junctional VE-cadherin away from the plasma membrane. This allows DEPs to penetrate into the cell and capillary lumen. In addition, pro-inflammatory cytokines are up-regulated and mediate vascular permeability in response to DEP. However, the mechanisms through which these DEP-induced pro-inflammatory cytokines increase vascular permeability remain unknown. Hence, we examined the ability of DEP to induce permeability of human umbilical vein endothelial cell tube cells to investigate these mechanisms. Furthermore, supplementation with NAC reduces ROS production following exposure to DEP. HUVEC tube cells contributed to a pro-inflammatory response to DEP-induced intracellular ROS generation. Endothelial oxidative stress induced the release of TNF-α and IL-6 from tube cells, subsequently stimulating the secretion of VEGF-A independent of HO-1. Our data suggests that DEP-induced intracellular ROS and release of the pro-inflammatory cytokines TNF- α and IL-6, which would contribute to VEGF-A secretion and disrupt cell-cell borders and increase vasculature permeability. Addition of NAC suppresses DEP-induced ROS efficiently and reduces subsequent damages by increasing endogenous glutathione. PMID:26148005

Diversity and Evolution of AbaR Genomic Resistance Islands in Acinetobacter baumannii Strains of European Clone I▿†

PubMed Central

Krizova, Lenka; Dijkshoorn, Lenie; Nemec, Alexandr

2011-01-01

To assess the diversity of AbaR genomic resistance islands in Acinetobacter baumannii European clone I (MLST clonal complex 1), we investigated 26 multidrug-resistant strains of this major clone isolated from hospitals in 21 cities of 10 European countries between 1984 and 2005. Each strain harbored an AbaR structure integrated at the same position in the chromosomal ATPase gene. AbaR3, including four subtypes based on variations in class 1 integron cassettes, and AbaR10 were found in 15 and 2 strains, respectively, whereas a new, unique AbaR variant was discovered in each of the other 9 strains. These new variants, designated AbaR11 to AbaR19 (19.8 kb to 57.5 kb), seem to be truncated derivatives of AbaR3, likely resulting from the deletions of its internal parts mediated by either IS26 elements (AbaR12 to AbaR19) or homologous recombination (AbaR11). AbaR3 was detected in all 10 strains isolated in 1984 to 1991, while AbaR11 to AbaR19 were carried only by strains isolated since 1997. Our results and those from previous publications suggest that AbaR3 is the original form of AbaR in European clone I, which may have provided strains of the lineage with a selective advantage facilitating their spread in European hospitals in the 1980s or before. PMID:21537009

Interactions between the S-domain receptor kinases and AtPUB-ARM E3 ubiquitin ligases suggest a conserved signaling pathway in Arabidopsis.

PubMed

Samuel, Marcus A; Mudgil, Yashwanti; Salt, Jennifer N; Delmas, Frédéric; Ramachandran, Shaliny; Chilelli, Andrea; Goring, Daphne R

2008-08-01

The Arabidopsis (Arabidopsis thaliana) genome encompasses multiple receptor kinase families with highly variable extracellular domains. Despite their large numbers, the various ligands and the downstream interacting partners for these kinases have been deciphered only for a few members. One such member, the S-receptor kinase, is known to mediate the self-incompatibility (SI) response in Brassica. S-receptor kinase has been shown to interact and phosphorylate a U-box/ARM-repeat-containing E3 ligase, ARC1, which, in turn, acts as a positive regulator of the SI response. In an effort to identify conserved signaling pathways in Arabidopsis, we performed yeast two-hybrid analyses of various S-domain receptor kinase family members with representative Arabidopsis plant U-box/ARM-repeat (AtPUB-ARM) E3 ligases. The kinase domains from S-domain receptor kinases were found to interact with ARM-repeat domains from AtPUB-ARM proteins. These kinase domains, along with M-locus protein kinase, a positive regulator of SI response, were also able to phosphorylate the ARM-repeat domains in in vitro phosphorylation assays. Subcellular localization patterns were investigated using transient expression assays in tobacco (Nicotiana tabacum) BY-2 cells and changes were detected in the presence of interacting kinases. Finally, potential links to the involvement of these interacting modules to the hormone abscisic acid (ABA) were investigated. Interestingly, AtPUB9 displayed redistribution to the plasma membrane of BY-2 cells when either treated with ABA or coexpressed with the active kinase domain of ARK1. As well, T-DNA insertion mutants for ARK1 and AtPUB9 lines were altered in their ABA sensitivity during germination and acted at or upstream of ABI3, indicating potential involvement of these proteins in ABA responses.

Mechanisms of regulation of cell-mediated immunity. III. The characterization of azobenzenearsonate-specific suppressor T-cell- derived-suppressor factors

PubMed Central

1979-01-01

Delayed type hypersensitivity to the hapten azobenzenearsonate (ABA) can be induced and suppressed by the administration of hapten-coupled syngeneic spleen cells by the appropriate route. Suppressor T cells stimulated by the intravenous administration of ABA-coupled spleen cells have been shown to produce a discrete subcellular factor(s) which is capable of suppressing delayed type hypersensitivity to azobenzenearsonate in the mouse. Such suppressor factors may be produced by the mechanical disruption of suppressor cells or by placing such suppressor cells in culture for 24 h. The suppressor factor(s) (SF) derived from ABA-specific suppressor cells exhibit biological specificity for the suppression of ABA delayed type hypersensitivity (DTH), but not trinitro-phenyl DTH, as well as the capacity to bind to ABA immunoadsorbents. Passage of suppressor factor(s) over reverse immunoadsorbents utilizing a rabbit anti-mouse F(ab')2 antiserum demonstrated that the antigen-specific T-cell derived SF does not bear conventional immunoglobulin markers. The suppressor factor(s) are not immunoglobulin molecules was further demonstrated by the inability of anti-ABA antibodies to suppress ABA DTH. Gel filtration of ABA suppressor factor(s) showed that the majority of the suppressive activity was present in a fraction with molecular weight ranging between 6.8 x 10(4) and 3.3 x 10(4) daltons. We also analyzed for the presence of determinants encoded by the H-2 major histocompatibility complex (MHC) and found that immunoadsorbents prepared utilizing antisera capable of interacting with gene products of the whole or selected gene regions of H-2 MHC, i.e., B10.D2 anti-B10.A and B10 anti- B10.A immunoadsorbents, retained the suppressive activity of ABA-SF. Elution of such columns with glycine HCl buffers (pH 2.8) permitted recovery of specific suppressive activity. Taken collectively such data supports the notion that suppressor T-cell-derived ABA suppressor factors have antigen-binding specificity as well as determinants controlled by the K end of the H-2 MHC. The distribution of strains capable of making SF has also been analyzed. The relationship of the antigen-binding specificity to VH gene products is discussed in this and the companion paper. PMID:312894

Cloning and characterization of a novel Gladiolus hybridus AFP family gene (GhAFP-like) related to corm dormancy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Jian; Seng, Shanshan; Carianopol, Carina

Abscisic acid (ABA) is an important phytohormone controlling seed dormancy. AFPs (ABA INSENSITIVE FIVE BINDING PROTEINS) are reported to be negative regulators of the ABA signaling pathway. The involvement of AFPs in dormant vegetative organs remains poorly understood. Here, we isolated and characterized a novel AFP family member from Gladiolus dormant cormels, GhAFP-like, containing three conserved domains of the AFP family. Quantitative PCR analysis revealed that GhAFP-like was expressed in dormant organs and its expression was down-regulated along with corm storage. GhAFP-like was verified to be a nuclear-localized protein. Overexpressing GhAFP-like in Arabidopsis thaliana not only showed weaker seed dormancymore » with insensitivity to ABA, but also changed the expression of some ABA related genes. In addition, a primary root elongation assay showed GhAFP-like may involve in auxin signaling response. The results in this study indicate that GhAFP-like acts as a negative regulator in ABA signaling and is related to dormancy. - Highlights: • GhAFP-like is expessed in dormant corm. • Overexpressing GhAFP-like showed early germination and insensitivity to ABA. • Overexpressing GhAFP-like changed ABI5 downstream genes expression.« less

The Role and Regulation of ABI5 (ABA-Insensitive 5) in Plant Development, Abiotic Stress Responses and Phytohormone Crosstalk

PubMed Central

Skubacz, Anna; Daszkowska-Golec, Agata; Szarejko, Iwona

2016-01-01

ABA Insensitive 5 (ABI5) is a basic leucine zipper transcription factor that plays a key role in the regulation of seed germination and early seedling growth in the presence of ABA and abiotic stresses. ABI5 functions in the core ABA signaling, which is composed of PYR/PYL/RCAR receptors, PP2C phosphatases and SnRK2 kinases, through the regulation of the expression of genes that contain the ABSCISIC ACID RESPONSE ELEMENT (ABRE) motif within their promoter region. The regulated targets include stress adaptation genes, e.g., LEA proteins. However, the expression and activation of ABI5 is not only dependent on the core ABA signaling. Many transcription factors such as ABI3, ABI4, MYB7 and WRKYs play either a positive or a negative role in the regulation of ABI5 expression. Additionally, the stability and activity of ABI5 are also regulated by other proteins through post-translational modifications such as phosphorylation, ubiquitination, sumoylation and S-nitrosylation. Moreover, ABI5 also acts as an ABA and other phytohormone signaling integrator. Components of auxin, cytokinin, gibberellic acid, jasmonate and brassinosteroid signaling and metabolism pathways were shown to take part in ABI5 regulation and/or to be regulated by ABI5. Monocot orthologs of AtABI5 have been identified. Although their roles in the molecular and physiological adaptations during abiotic stress have been elucidated, knowledge about their detailed action still remains elusive. Here, we describe the recent advances in understanding the action of ABI5 in early developmental processes and the adaptation of plants to unfavorable environmental conditions. We also focus on ABI5 relation to other phytohormones in the abiotic stress response of plants. PMID:28018412

Fluoride induces oxidative damage and SIRT1/autophagy through ROS-mediated JNK signaling.

PubMed

Suzuki, Maiko; Bandoski, Cheryl; Bartlett, John D

2015-12-01

Fluoride is an effective caries prophylactic, but at high doses can also be an environmental health hazard. Acute or chronic exposure to high fluoride doses can result in dental enamel and skeletal and soft tissue fluorosis. Dental fluorosis is manifested as mottled, discolored, porous enamel that is susceptible to dental caries. Fluoride induces cell stress, including endoplasmic reticulum stress and oxidative stress, which leads to impairment of ameloblasts responsible for dental enamel formation. Recently we reported that fluoride activates SIRT1 and autophagy as an adaptive response to protect cells from stress. However, it still remains unclear how SIRT1/autophagy is regulated in dental fluorosis. In this study, we demonstrate that fluoride exposure generates reactive oxygen species (ROS) and the resulting oxidative damage is counteracted by SIRT1/autophagy induction through c-Jun N-terminal kinase (JNK) signaling in ameloblasts. In the mouse-ameloblast-derived cell line LS8, fluoride induced ROS, mitochondrial damage including cytochrome-c release, up-regulation of UCP2, attenuation of ATP synthesis, and H2AX phosphorylation (γH2AX), which is a marker of DNA damage. We evaluated the effects of the ROS inhibitor N-acetylcysteine (NAC) and the JNK inhibitor SP600125 on fluoride-induced SIRT1/autophagy activation. NAC decreased fluoride-induced ROS generation and attenuated JNK and c-Jun phosphorylation. NAC decreased SIRT1 phosphorylation and formation of the autophagy marker LC3II, which resulted in an increase in the apoptosis mediators γH2AX and cleaved/activated caspase-3. SP600125 attenuated fluoride-induced SIRT1 phosphorylation, indicating that fluoride activates SIRT1/autophagy via the ROS-mediated JNK pathway. In enamel organs from rats or mice treated with 50, 100, or 125 ppm fluoride for 6 weeks, cytochrome-c release and the DNA damage markers 8-oxoguanine, p-ATM, and γH2AX were increased compared to those in controls (0 ppm fluoride). These results suggest that fluoride-induced ROS generation causes mitochondrial damage and DNA damage, which may lead to impairment of ameloblast function. To counteract this impairment, SIRT1/autophagy is induced via JNK signaling to protect cells/ameloblasts from fluoride-induced oxidative damage that may cause dental fluorosis. Copyright © 2015 Elsevier Inc. All rights reserved.

Fluoride induces oxidative damage and SIRT1/autophagy through ROS-mediated JNK signaling

PubMed Central

Suzuki, Maiko; Bandoski, Cheryl; Bartlett, John D.

2015-01-01

Fluoride is an effective caries prophylactic, but at high doses can also be an environmental health hazard. Acute or chronic exposure to high fluoride doses can result in dental enamel and skeletal and soft tissue fluorosis. Dental fluorosis is manifested as mottled, discolored, porous enamel that is susceptible to dental caries. Fluoride induces cell stress, including endoplasmic reticulum stress and oxidative stress, which leads to impairment of ameloblasts responsible for dental enamel formation. Recently we reported that fluoride activates SIRT1 and autophagy as an adaptive response to protect cells from stress. However, it still remains unclear how SIRT1/autophagy is regulated in dental fluorosis. In this study, we demonstrate that fluoride exposure generates reactive oxygen species (ROS) and the resulting oxidative damage is counteracted by SIRT1/autophagy induction through c-Jun N-terminal kinase (JNK) signaling in ameloblasts. In the mouse-ameloblast-derived cell line LS8, fluoride induced ROS, mitochondrial damage including cytochrome-c release, up-regulation of UCP2, attenuation of ATP synthesis, and H2AX phosphorylation (γH2AX), which is a marker of DNA damage. We evaluated the effects of the ROS inhibitor N-acetylcysteine (NAC) and the JNK inhibitor SP600125 on fluoride-induced SIRT1/autophagy activation. NAC decreased fluoride-induced ROS generation and attenuated JNK and c-Jun phosphorylation. NAC decreased SIRT1 phosphorylation and formation of the autophagy marker LC3II, which resulted in an increase in the apoptosis mediators γH2AX and cleaved/activated caspase-3. SP600125 attenuated fluoride-induced SIRT1 phosphorylation, indicating that fluoride activates SIRT1/autophagy via the ROS-mediated JNK pathway. In enamel organs from rats or mice treated with 50, 100, or 125 ppm fluoride for 6 weeks, cytochrome-c release and the DNA damage markers 8-oxoguanine, p-ATM, and γH2AX were increased compared to those in controls (0 ppm fluoride). These results suggest that fluoride-induced ROS generation causes mitochondrial damage and DNA damage, which may lead to impairment of ameloblast function. To counteract this impairment, SIRT1/autophagy is induced via JNK signaling to protect cells/ameloblasts from fluoride-induced oxidative damage that may cause dental fluorosis. PMID:26431905

ABA-Induced Stomatal Closure Involves ALMT4, a Phosphorylation-Dependent Vacuolar Anion Channel of Arabidopsis[OPEN

PubMed Central

Baetz, Ulrike; Huck, Nicola V.; Zhang, Jingbo

2017-01-01

Stomatal pores are formed between a pair of guard cells and allow plant uptake of CO2 and water evaporation. Their aperture depends on changes in osmolyte concentration of guard cell vacuoles, specifically of K+ and Mal2−. Efflux of Mal2− from the vacuole is required for stomatal closure; however, it is not clear how the anion is released. Here, we report the identification of ALMT4 (ALUMINUM ACTIVATED MALATE TRANSPORTER4) as an Arabidopsis thaliana ion channel that can mediate Mal2− release from the vacuole and is required for stomatal closure in response to abscisic acid (ABA). Knockout mutants showed impaired stomatal closure in response to the drought stress hormone ABA and increased whole-plant wilting in response to drought and ABA. Electrophysiological data show that ALMT4 can mediate Mal2− efflux and that the channel activity is dependent on a phosphorylatable C-terminal serine. Dephosphomimetic mutants of ALMT4 S382 showed increased channel activity and Mal2− efflux. Reconstituting the active channel in almt4 mutants impaired growth and stomatal opening. Phosphomimetic mutants were electrically inactive and phenocopied the almt4 mutants. Surprisingly, S382 can be phosphorylated by mitogen-activated protein kinases in vitro. In brief, ALMT4 likely mediates Mal2− efflux during ABA-induced stomatal closure and its activity depends on phosphorylation. PMID:28874508

Abscisic acid ameliorates the systemic sclerosis fibroblast phenotype in vitro

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruzzone, Santina, E-mail: santina.bruzzone@unige.it; Centre of Excellence for Biomedical Research, University of Genova, Viale Benedetto XV 9, 16132 Genova; Advanced Biotechnology Center, Largo Rosanna Benzi 10, 16132 Genova

Highlights: Black-Right-Pointing-Pointer ABA is an endogenous hormone in humans, regulating different cell responses. Black-Right-Pointing-Pointer ABA reverts some of the functions altered in SSc fibroblasts to a normal phenotype. Black-Right-Pointing-Pointer UV-B irradiation increases ABA content in SSc cultures. Black-Right-Pointing-Pointer SSc fibroblasts could benefit from exposure to ABA and/or to UV-B. -- Abstract: The phytohormone abscisic acid (ABA) has been recently identified as an endogenous hormone in humans, regulating different cell functions, including inflammatory processes, insulin release and glucose uptake. Systemic sclerosis (SSc) is a chronic inflammatory disease resulting in fibrosis of skin and internal organs. In this study, we investigated themore » effect of exogenous ABA on fibroblasts obtained from healthy subjects and from SSc patients. Migration of control fibroblasts induced by ABA was comparable to that induced by transforming growth factor-{beta} (TGF-{beta}). Conversely, migration toward ABA, but not toward TGF-{beta}, was impaired in SSc fibroblasts. In addition, ABA increased cell proliferation in fibroblasts from SSc patients, but not from healthy subjects. Most importantly, presence of ABA significantly decreased collagen deposition by SSc fibroblasts, at the same time increasing matrix metalloproteinase-1 activity and decreasing the expression level of tissue inhibitor of metalloproteinase (TIMP-1). Thus, exogenously added ABA appeared to revert some of the functions altered in SSc fibroblasts to a normal phenotype. Interestingly, ABA levels in plasma from SSc patients were found to be significantly lower than in healthy subjects. UV-B irradiation induced an almost 3-fold increase in ABA content in SSc cultures. Altogether, these results suggest that the fibrotic skin lesions in SSc patients could benefit from exposure to high(er) ABA levels.« less

Transcriptome profiling of postharvest strawberry fruit in response to exogenous auxin and abscisic acid.

PubMed

Chen, Jingxin; Mao, Linchun; Lu, Wenjing; Ying, Tiejin; Luo, Zisheng

2016-01-01

Auxin and abscisic acid regulate strawberry fruit ripening and senescence through cross-talk of their signal transduction pathways that further modulate the structural genes related to physico-chemical properties of fruit. The physiological and transcriptomic changes in harvested strawberry fruits in responses to IAA, ABA and their combination were analyzed. Exogenous IAA delayed the ripening process of strawberries after harvest while ABA promoted the postharvest ripening. However, treatment with a combination of IAA and ABA did not slow down nor accelerate the postharvest ripening in the strawberry fruits. At the molecular level, exogenous IAA up regulated the expressions of genes related to IAA signaling, including AUX/IAA, ARF, TOPLESS and genes encoding E3 ubiquitin protein ligase and annexin, and down regulated genes related to pectin depolymerization, cell wall degradation, sucrose and anthocyanin biosyntheses. In contrast, exogenous ABA induced genes related to fruit softening, and genes involved in signaling pathways including SKP1, HSPs, CK2, and SRG1. Comparison of transcriptomes in responses to individual treatments with IAA or ABA or the combination revealed that there were cooperative and antagonistic actions between IAA and ABA in fruit. However, 17% of the differentially expressed unigenes in response to the combination of IAA and ABA were unique and were not found in those unigenes responding to either IAA or ABA alone. The analyses also found that receptor-like kinases and ubiquitin ligases responded to both IAA and ABA, which seemed to play a pivotal role in both hormones' signaling pathways and thus might be the cross-talk points of both hormones.

AtRH57, a DEAD-box RNA helicase, is involved in feedback inhibition of glucose-mediated abscisic acid accumulation during seedling development and additively affects pre-ribosomal RNA processing with high glucose.

PubMed

Hsu, Yi-Feng; Chen, Yun-Chu; Hsiao, Yu-Chun; Wang, Bing-Jyun; Lin, Shih-Yun; Cheng, Wan-Hsing; Jauh, Guang-Yuh; Harada, John J; Wang, Co-Shine

2014-01-01

The Arabidopsis thaliana T-DNA insertion mutant rh57-1 exhibited hypersensitivity to glucose (Glc) and abscisic acid (ABA). The other two rh57 mutants also showed Glc hypersensitivity similar to rh57-1, strongly suggesting that the Glc-hypersensitive feature of these mutants results from mutation of AtRH57. rh57-1 and rh57-3 displayed severely impaired seedling growth when grown in Glc concentrations higher than 3%. The gene, AtRH57 (At3g09720), was expressed in all Arabidopsis organs and its transcript was significantly induced by ABA, high Glc and salt. The new AtRH57 belongs to class II DEAD-box RNA helicase gene family. Transient expression of AtRH57-EGFP (enhanced green fluorescent protein) in onion cells indicated that AtRH57 was localized in the nucleus and nucleolus. Purified AtRH57-His protein was shown to unwind double-stranded RNA independent of ATP in vitro. The ABA biosynthesis inhibitor fluridone profoundly redeemed seedling growth arrest mediated by sugar. rh57-1 showed increased ABA levels when exposed to high Glc. Quantitative real time polymerase chain reaction analysis showed that AtRH57 acts in a signaling network downstream of HXK1. A feedback inhibition of ABA accumulation mediated by AtRH57 exists within the sugar-mediated ABA signaling. AtRH57 mutation and high Glc conditions additively caused a severe defect in small ribosomal subunit formation. The accumulation of abnormal pre-rRNA and resistance to protein synthesis-related antibiotics were observed in rh57 mutants and in the wild-type Col-0 under high Glc conditions. These results suggested that AtRH57 plays an important role in rRNA biogenesis in Arabidopsis and participates in response to sugar involving Glc- and ABA signaling during germination and seedling growth. © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.

Macranthoidin B Modulates Key Metabolic Pathways to Enhance ROS Generation and Induce Cytotoxicity and Apoptosis in Colorectal Cancer.

PubMed

Fan, Xing; Rao, Jun; Zhang, Ziwei; Li, Dengfeng; Cui, Wenhao; Zhang, Jun; Wang, Hua; Tou, Fangfang; Zheng, Zhi; Shen, Qiang

2018-01-01

Induction of oxidative stress and reactive oxygen species (ROS) mediated-apoptosis have been utilized as effective strategies in anticancer therapy. Macranthoidin B (MB) is a potent inducer of ROS-mediated apoptosis in cancer, but its mechanism of action is poorly understood. Superoxide production with MB exposure in colorectal cancer (CRC) cells was measured using lucigenin chemiluminescence and real-time PCR. MB's inhibitory effect on proliferation and viability of CRC cells was determined by proliferation assays. MB's effect on apoptosis of CRC cells was determined by Western blotting and annexin V-FITC/PI staining. MB's effect on the growth of CRC xenografts in mice was assessed. An established metabolomics profiling platform combining ultra-performance liquid chromatography-tandem mass spectrometry (LC-MS) with gas chromatography-mass spectrometry (GC-MS) was performed to determine MB's effect on total metabolite variation in CRC cells. We found that MB increases ROS generation via modulating key metabolic pathways. Using metabolomics profiling platform combining LC-MS with GC-MS, a total of 236 metabolites were identified in HCT-116 cells in which 31 metabolites were determined to be significantly regulated (p ≤ 0.05) after MB exposure. A number of key metabolites revealed by metabolomics analysis include glucose, fructose, citrate, arginine, phenylalanine, and S-adenosylhomocysteine (SAH), suggesting specific modulation of metabolism on carbohydrates, amino acids and peptides, lipids, nucleotide, cofactors and vitamins in HCT-116 CRC cells with MB treatment highly associated with apoptosis triggered by enhanced ROS and activated caspase-3. Our results demonstrate that MB represses CRC cell proliferation by inducing ROS-mediated apoptosis. © 2018 The Author(s). Published by S. Karger AG, Basel.

DNA-Demethylase Regulated Genes Show Methylation-Independent Spatiotemporal Expression Patterns

PubMed Central

Schumann, Ulrike; Lee, Joanne; Kazan, Kemal; Ayliffe, Michael; Wang, Ming-Bo

2017-01-01

Recent research has indicated that a subset of defense-related genes is downregulated in the Arabidopsis DNA demethylase triple mutant rdd (ros1 dml2 dml3) resulting in increased susceptibility to the fungal pathogen Fusarium oxysporum. In rdd plants these downregulated genes contain hypermethylated transposable element sequences (TE) in their promoters, suggesting that this methylation represses gene expression in the mutant and that these sequences are actively demethylated in wild-type plants to maintain gene expression. In this study, the tissue-specific and pathogen-inducible expression patterns of rdd-downregulated genes were investigated and the individual role of ROS1, DML2, and DML3 demethylases in these spatiotemporal regulation patterns was determined. Large differences in defense gene expression were observed between pathogen-infected and uninfected tissues and between root and shoot tissues in both WT and rdd plants, however, only subtle changes in promoter TE methylation patterns occurred. Therefore, while TE hypermethylation caused decreased gene expression in rdd plants it did not dramatically effect spatiotemporal gene regulation, suggesting that this latter regulation is largely methylation independent. Analysis of ros1-3, dml2-1, and dml3-1 single gene mutant lines showed that promoter TE hypermethylation and defense-related gene repression was predominantly, but not exclusively, due to loss of ROS1 activity. These data demonstrate that DNA demethylation of TE sequences, largely by ROS1, promotes defense-related gene expression but does not control spatiotemporal expression in Arabidopsis. Summary: Ros1-mediated DNA demethylation of promoter transposable elements is essential for activation of defense-related gene expression in response to fungal infection in Arabidopsis thaliana. PMID:28894455

Moderate extracellular acidification inhibits capsaicin-induced cell death through regulating calcium mobilization, NF-{kappa}B translocation and ROS production in synoviocytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Fen; Yang, Shuang; Zhao, Dan

Highlights: Black-Right-Pointing-Pointer Moderate extracellular acidification regulates intracellular Ca{sup 2+} mobilization. Black-Right-Pointing-Pointer Moderate acidification activates NF-{kappa}B nuclear translocation in synoviocytes. Black-Right-Pointing-Pointer Moderate acidification depresses the ROS production induced by capsaicin. Black-Right-Pointing-Pointer Moderate acidification inhibits capsaicin-caused synoviocyte death. -- Abstract: We previously show the expression of transient receptor potential vanilloid 1 (TRPV1) in primary synoviocytes from collagen-induced arthritis (CIA) rats. Capsaicin and lowered extracellular pH from 7.4 to 5.5 induce cell death through TRPV1-mediated Ca{sup 2+} entry and reactive oxygen species (ROS) production. However, under the pathological condition in rheumatoid arthritis, the synovial fluid is acidified to a moderate level (about pHmore » 6.8). In the present study, we examined the effects of pH 6.8 on the TRPV1-mediated cell death. Our finding is different or even opposite from what was observed at pH 5.5. We found that the moderate extracellular acidification (from pH 7.4 to 6.8) inhibited the capsaicin-induced Ca{sup 2+} entry through attenuating the activity of TRPV1. In the mean time, it triggered a phospholipse C (PLC)-related Ca{sup 2+} release from intracellular stores. The nuclear translocation of NF-{kappa}B was found at pH 6.8, and this also depends on PLC activation. Moreover, the capsaicin-evoked massive ROS production and cell death were depressed at pH 6.8, both of which are dependent on the activation of PLC and NF-{kappa}B. Taken together, these results suggested that the moderate extracellular acidification inhibited the capsaicin-induced synoviocyte death through regulating Ca{sup 2+} mobilization, activating NF-{kappa}B nuclear translocation and depressing ROS production.« less

A 14-3-3 Family Protein from Wild Soybean (Glycine Soja) Regulates ABA Sensitivity in Arabidopsis

PubMed Central

Sun, Xiaoli; Sun, Mingzhe; Jia, Bowei; Chen, Chao; Qin, Zhiwei; Yang, Kejun; Shen, Yang; Meiping, Zhang; Mingyang, Cong; Zhu, Yanming

2015-01-01

It is widely accepted that the 14-3-3 family proteins are key regulators of multiple stress signal transduction cascades. By conducting genome-wide analysis, researchers have identified the soybean 14-3-3 family proteins; however, until now, there is still no direct genetic evidence showing the involvement of soybean 14-3-3s in ABA responses. Hence, in this study, based on the latest Glycine max genome on Phytozome v10.3, we initially analyzed the evolutionary relationship, genome organization, gene structure and duplication, and three-dimensional structure of soybean 14-3-3 family proteins systematically. Our results suggested that soybean 14-3-3 family was highly evolutionary conserved and possessed segmental duplication in evolution. Then, based on our previous functional characterization of a Glycine soja 14-3-3 protein GsGF14o in drought stress responses, we further investigated the expression characteristics of GsGF14o in detail, and demonstrated its positive roles in ABA sensitivity. Quantitative real-time PCR analyses in Glycine soja seedlings and GUS activity assays in PGsGF14O:GUS transgenic Arabidopsis showed that GsGF14o expression was moderately and rapidly induced by ABA treatment. As expected, GsGF14o overexpression in Arabidopsis augmented the ABA inhibition of seed germination and seedling growth, promoted the ABA induced stomata closure, and up-regulated the expression levels of ABA induced genes. Moreover, through yeast two hybrid analyses, we further demonstrated that GsGF14o physically interacted with the AREB/ABF transcription factors in yeast cells. Taken together, results presented in this study strongly suggested that GsGF14o played an important role in regulation of ABA sensitivity in Arabidopsis. PMID:26717241

A Novel Wheat C-bZIP Gene, TabZIP14-B, Participates in Salt and Freezing Tolerance in Transgenic Plants

PubMed Central

Zhang, Lina; Zhang, Lichao; Xia, Chuan; Gao, Lifeng; Hao, Chenyang; Zhao, Guangyao; Jia, Jizeng; Kong, Xiuying

2017-01-01

The group C-bZIP transcription factors (TFs) are involved in diverse biological processes, such as the regulation of seed storage protein (SSP) production and the responses to pathogen challenge and abiotic stress. However, our knowledge of the abiotic functions of group C-bZIP genes in wheat remains limited. Here, we present the function of a novel TabZIP14-B gene in wheat. This gene belongs to the group C-bZIP TFs and contains six exons and five introns; three haplotypes were identified among accessions of tetraploid and hexaploid wheat. A subcellular localization analysis indicated that TabZIP14-B was targeted to the nucleus of tobacco epidermal cells. A transactivation assay demonstrated that TabZIP14-B showed transcriptional activation ability and was capable of binding the abscisic acid (ABA) responsive element (ABRE) in yeast. RT-qPCR revealed that TabZIP14-B was expressed in the roots, stems, leaves, and young spikes and was up-regulated by exogenous ABA, salt, low-temperature, and polyethylene glycol (PEG) stress treatments. Furthermore, Arabidopsis plants overexpressing TabZIP14-B exhibited enhanced tolerance to salt, freezing stresses and ABA sensitivity. Overexpression of TabZIP14-B resulted in increased expression of the AtRD29A, AtCOR47, AtRD20, AtGSTF6, and AtRAB18 genes and changes in several physiological characteristics. These results suggest that TabZIP14-B could function as a positive regulator in mediating the abiotic stress response. PMID:28536588

Overexpression of StNF-YB3.1 reduces photosynthetic capacity and tuber production, and promotes ABA-mediated stomatal closure in potato (Solanum tuberosum L.).

PubMed

Xuanyuan, Guochao; Lu, Congming; Zhang, Ruofang; Jiang, Jiming

2017-08-01

Nuclear factor Y (NF-Y) is one of the most ubiquitous transcription factors (TFs), comprising NF-YA, NF-YB and NF-YC subunits, and has been identified and reported in various aspects of development for plants and animals. In this work, StNF-YB3.1, a putative potato NF-YB subunit encoding gene, was isolated from Solanum tuberosum by rapid amplification of cDNA ends (RACE). Overexpression of StNF-YB3.1 in potato (cv. Atlantic) resulted in accelerated onset of flowering, and significant increase in leaf chlorophyll content in field trials. However, transgenic potato plants overexpressing StNF-YB3.1 (OEYB3.1) showed significant decreases in photosynthetic rate and stomatal conductance both at tuber initiation and bulking stages. OEYB3.1 lines were associated with significantly fewer tuber numbers and yield reduction. Guard cell size and stomatal density were not changed in OEYB3.1 plants, whereas ABA-mediated stomatal closure was accelerated compared to that of wild type plants because of the up-regulation of genes for ABA signaling, such as StCPK10-like, StSnRK2.6/OST1-like, StSnRK2.7-like and StSLAC1-like. We speculate that the acceleration of stomatal closure was a possible reason for the significantly decreased stomatal conductance and photosynthetic rate. Copyright © 2017 Elsevier B.V. All rights reserved.

Mitochondria and FOXO3: breath or die.

PubMed

Hagenbuchner, Judith; Ausserlechner, Michael J

2013-01-01

Forkhead box O (FOXO) transcription factors are regulators of cell-type specific apoptosis and cell cycle arrest but also control longevity and reactive oxygen species (ROS). ROS-control by FOXO is mediated by transcriptional activation of detoxifying enzymes such as Superoxide dismutase 2 (SOD2), Catalase or Sestrins or by the repression of mitochondrial respiratory chain proteins resulting in reduced mitochondrial activity. FOXO3 also regulates the adaptation to hypoxia by reducing mitochondrial mass and oxygen consumption during HIF-1α activation. In neuronal tumor cells, FOXO3 triggers ROS-accumulation as a consequence of transient mitochondrial outer membrane permeabilization, which is essential for FOXO3-induced apoptosis in these cells. Cellular ROS levels are affected by the FOXO-targets Bim, BclxL, and Survivin. All three proteins localize to mitochondria and affect mitochondrial membrane potential, respiration and cellular ROS levels. Bim-activation by FOXO3 causes mitochondrial depolarization resulting in a transitory decrease of respiration and ROS production. Survivin, on the other hand, actively changes mitochondrial architecture, respiration-efficacy and energy metabolism. This ability distinguishes Survivin from other anti-apoptotic proteins such as BclxL, which inhibits ROS by inactivating Bim but does not alter mitochondrial function. Importantly, FOXO3 simultaneously also activates ROS-detoxification via induction of SESN3. In this paper we discuss the hypothesis that the delicate balance between ROS-accumulation by Bim-triggered mitochondrial damage, mitochondrial architecture and ROS-detoxifying proteins determines cell fate. We provide evidence for a FOXO self-reactivating loop and for novel functions of FOXO3 in controlling mitochondrial respiration of neuronal cells, which further supports the current view that FOXO transcription factors are information-integrating sentinels of cellular stress and critical modulators of cell homeostasis.

Calcium-dependent protein kinase 21 phosphorylates 14-3-3 proteins in response to ABA signaling and salt stress in rice.

PubMed

Chen, Yixing; Zhou, Xiaojin; Chang, Shu; Chu, Zhilin; Wang, Hanmeng; Han, Shengcheng; Wang, Yingdian

2017-12-02

The calcium-dependent protein kinases (CDPKs) are a class of plant-specific kinase that directly bind Ca 2+ and mediate the calcium-signaling pathways to play important physiological roles in growth and development. The rice genome contains 31 CDPK genes, one of which, OsCPK21, is known to modulate the abscisic acid (ABA) and salt stress responses in this crop; however, the molecular mechanisms underlying this regulation are largely unknown. In the present study, we performed yeast two-hybrid screening, glutathione S-transferase pull-down, co-immunoprecipitation, and bimolecular fluorescence complementation assays to confirm the interaction between OsCPK21 and one of its putative targets, Os14-3-3 (OsGF14e). We used an in vitro kinase assay and site-directed mutagenesis to verify that OsCPK21 phosphorylates OsGF14e at Tyr-138. We used real-time PCR to reveal that several ABA and salt inducible genes were more highly expressed in the OsCPK21-OE and OsGF14e WT-OE plants than in the mutant OsGF14e Y138A-OE and wild-type plants. These results suggest that OsCPK21 phosphorylates OsGF14e to facilitate the response to ABA and salt stress. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Abscisic Acid Transport and Homeostasis in the Context of Stomatal Regulation.

PubMed

Merilo, Ebe; Jalakas, Pirko; Laanemets, Kristiina; Mohammadi, Omid; Hõrak, Hanna; Kollist, Hannes; Brosché, Mikael

2015-09-01

The discovery of cytosolic ABA receptors is an important breakthrough in stomatal research; signaling via these receptors is involved in determining the basal stomatal conductance and stomatal responsiveness. However, the source of ABA in guard cells is still not fully understood. The level of ABA increases in guard cells by de novo synthesis, recycling from inactive conjugates via β-glucosidases BG1 and BG2 and by import, whereas it decreases by hydroxylation, conjugation, and export. ABA importers include the NRT1/PTR family protein AIT1, ATP-binding cassette protein ABCG40, and possibly ABCG22, whereas the DTX family member DTX50 and ABCG25 function as ABA exporters. Here, we review the proteins involved in ABA transport and homeostasis and their physiological role in stomatal regulation. Recent experiments suggest that functional redundancy probably exists among ABA transporters between vasculature and guard cells and ABA recycling proteins, as stomatal functioning remained intact in abcg22, abcg25, abcg40, ait1, and bg1bg2 mutants. Only the initial response to reduced air humidity was significantly delayed in abcg22. Considering the reports showing autonomous ABA synthesis in guard cells, we discuss that rapid stomatal responses to atmospheric factors might depend primarily on guard cell-synthesized ABA, whereas in the case of long-term soil water deficit, ABA synthesized in the vasculature might have a significant role. Copyright © 2015 The Author. Published by Elsevier Inc. All rights reserved.

Agmatine Reduces Lipopolysaccharide-Mediated Oxidant Response via Activating PI3K/Akt Pathway and Up-Regulating Nrf2 and HO-1 Expression in Macrophages

PubMed Central

Chai, Jianshen; Luo, Li; Hou, Fengyan; Fan, Xia; Yu, Jing; Ma, Wei; Tang, Wangqi; Yang, Xue; Zhu, Junyu; Kang, Wenyuan; Yan, Jun; Liang, Huaping

2016-01-01

Macrophages are key responders of inflammation and are closely related with oxidative stress. Activated macrophages can enhance oxygen depletion, which causes an overproduction of reactive oxygen species (ROS) and leads to further excessive inflammatory response and tissue damage. Agmatine, an endogenous metabolite of L-arginine, has recently been shown to have neuroprotective effects based on its antioxidant properties. However, the antioxidant effects of agmatine in peripheral tissues and cells, especially macrophages, remain unclear. In this study we explored the role of agmatine in mediating antioxidant effects in RAW 264.7 cells and studied its antioxidant mechanism. Our data demonstrate that agmatine is an activator of Nrf2 signaling that markedly enhances Nrf2 nuclear translocation, increases nuclear Nrf2 protein level, up-regulates the expression of the Nrf2 downstream effector HO-1, and attenuates ROS generation induced by Lipopolysaccharide (LPS). We further demonstrated that the agmatine-induced activation of Nrf2 is likely through the PI3K/Akt pathway. LY294002, a specific PI3K/Akt inhibitor, abolished agmatine-induced HO-1 up-regulation and ROS suppression significantly. Inhibiting HO-1 pathway significantly attenuated the antioxidant effect of agmatine which the products of HO-1 enzymatic activity contributed to. Furthermore, the common membrane receptors of agmatine were evaluated, revealing that α2-adrenoceptor, I1-imidazoline receptor or I2-imidazoline receptor are not required by the antioxidant properties of agmatine. Taken together, our findings revealed that agmatine has antioxidant activity against LPS-induced ROS accumulation in RAW 264.7 cells involving HO-1 expression induced by Nrf2 via PI3K/Akt pathway activation. PMID:27685463

AREB1, AREB2, and ABF3 are master transcription factors that cooperatively regulate ABRE-dependent ABA signaling involved in drought stress tolerance and require ABA for full activation.

PubMed

Yoshida, Takuya; Fujita, Yasunari; Sayama, Hiroko; Kidokoro, Satoshi; Maruyama, Kyonoshin; Mizoi, Junya; Shinozaki, Kazuo; Yamaguchi-Shinozaki, Kazuko

2010-02-01

A myriad of drought stress-inducible genes have been reported, and many of these are activated by abscisic acid (ABA). In the promoter regions of such ABA-regulated genes, conserved cis-elements, designated ABA-responsive elements (ABREs), control gene expression via bZIP-type AREB/ABF transcription factors. Although all three members of the AREB/ABF subfamily, AREB1, AREB2, and ABF3, are upregulated by ABA and water stress, it remains unclear whether these are functional homologs. Here, we report that all three AREB/ABF transcription factors require ABA for full activation, can form hetero- or homodimers to function in nuclei, and can interact with SRK2D/SnRK2.2, an SnRK2 protein kinase that was identified as a regulator of AREB1. Along with the tissue-specific expression patterns of these genes and the subcellular localization of their encoded proteins, these findings clearly indicate that AREB1, AREB2, and ABF3 have largely overlapping functions. To elucidate the role of these AREB/ABF transcription factors, we generated an areb1 areb2 abf3 triple mutant. Large-scale transcriptome analysis, which showed that stress-responsive gene expression is remarkably impaired in the triple mutant, revealed novel AREB/ABF downstream genes in response to water stress, including many LEA class and group-Ab PP2C genes and transcription factors. The areb1 areb2 abf3 triple mutant is more resistant to ABA than are the other single and double mutants with respect to primary root growth, and it displays reduced drought tolerance. Thus, these results indicate that AREB1, AREB2, and ABF3 are master transcription factors that cooperatively regulate ABRE-dependent gene expression for ABA signaling under conditions of water stress.

Abscisic acid (ABA) and key proteins in its perception and signaling pathways are ancient, but their roles have changed through time.

PubMed

Sussmilch, Frances C; Atallah, Nadia M; Brodribb, Timothy J; Banks, Jo Ann; McAdam, Scott A M

2017-09-02

Homologs of the Arabidopsis core abscisic acid (ABA) signaling component OPEN STOMATA1 (OST1) are best known for their role in closing stomata in angiosperm species. We recently characterized a fern OST1 homolog, GAMETOPHYTES ABA INSENSITIVE ON ANTHERDIOGEN 1 (GAIA1), which is not required for stomatal closure in ferns, consistent with physiologic evidence that shows the stomata of these plants respond passively to changes in leaf water status. Instead, gaia1 mutants reveal a critical role in ABA signaling for spore dormancy and sex determination, in a system regulated by antagonism between ABA and the gibberellin (GA)-derived fern hormone antheridiogen (A CE ). ABA and key proteins, including ABA receptors from the PYR/PYL/RCAR family and negative regulators of ABA-signaling from Group A of the type-2C protein phosphatases (PP2Cs), in addition to OST1 homologs, can be found in all terrestrial land plant lineages, ranging from liverworts that lack stomata, to angiosperms. As land plants have evolved and diversified over the past 450 million years, so too have the roles of this important plant hormone and the genes involved in its signaling and perception.

Enhancing tolerance of rice (Oryza sativa) to simulated acid rain by exogenous abscisic acid.

PubMed

Wu, Xi; Liang, Chanjuan

2017-02-01

Abscisic acid (ABA) regulates much important plant physiological and biochemical processes and induces tolerance to different stresses. Here, we studied the regulation of exogenous ABA on adaptation of rice seedlings to simulated acid rain (SAR) stress by measuring biomass dry weight, stomatal conductance, net photosynthesis rate, nutrient elements, and endogenous hormones. The application of 10 μM ABA alleviated the SAR-induced inhibition on growth, stomatal conductance, net photosynthesis rate, and decreases in contents of nutrient (K, Mg, N, and P) and hormone (auxin, gibberellins, and zeatin). Moreover, 10 μM ABA could stimulate the Ca content as signaling molecules under SAR stress. Contrarily, the application of 100 μM ABA aggravated the SAR-induced inhibition on growth, stomatal conductance, net photosynthesis rate, and contents of nutrient and hormone. The results got after a 5-day recovery (without SAR) show that exogenous 10 μM ABA can promote self-restoration process in rice whereas 100 μM ABA hindered the restoration by increasing deficiency of nutrients and disturbing the balance of hormones. These results confirmed that exogenous ABA at proper concentration could enhance the tolerance of rice to SAR stress.

Class IA phosphoinositide 3-kinase β and δ regulate neutrophil oxidase activation in response to Aspergillus fumigatus hyphae.

PubMed

Boyle, Keith B; Gyori, David; Sindrilaru, Anca; Scharffetter-Kochanek, Karin; Taylor, Philip R; Mócsai, Attila; Stephens, Len R; Hawkins, Phillip T

2011-03-01

An effective immune response to the ubiquitous fungus Aspergillus fumigatus is dependent upon production of reactive oxygen species (ROS) by the NADPH oxidase. This is evidenced by the acute sensitivity of oxidase-deficient humans and mice to invasive aspergillosis. Neutrophils are recruited to the lungs shortly postinfection and respond by phagocytosing conidia and mediating extracellular killing of germinated hyphae in a ROS-dependent manner. However, the signaling mechanisms regulating the generation of ROS in response to hyphae are poorly understood. PI3Ks are important regulators of numerous cellular processes, with much recent work describing unique roles for the different class I PI3K isoforms. We showed by live-cell imaging that the lipid products of class I PI3Ks accumulated at the hyphal-bound neutrophil plasma membrane. Further, we used pharmacological and genetic approaches to demonstrate essential, but overlapping, roles for PI3Kβ and PI3Kδ in the ROS and spreading responses of murine neutrophils to Aspergillus hyphae. Hyphal-induced ROS responses were substantially inhibited by deletion of the common β2-integrin subunit CD18, with only a minor, redundant role for Dectin-1. However, addition of soluble algal glucans plus the genetic deletion of CD18 were required to significantly inhibit activation of the PI3K-effector protein kinase B. Hyphal ROS responses were also totally dependent on the presence of Syk, but not its ITAM-containing adaptor proteins FcRγ or DAP12, and the Vav family of Rac-guanine nucleotide exchange factors. These results start to define the signaling network controlling neutrophil ROS responses to A. fumigatus hyphae.

Seleno-short-chain chitosan induces apoptosis in human non-small-cell lung cancer A549 cells through ROS-mediated mitochondrial pathway.

PubMed

Zhao, Yana; Zhang, Shaojing; Wang, Pengfei; Fu, Shengnan; Wu, Di; Liu, Anjun

2017-12-01

Seleno-short-chain chitosan (SSCC) is a synthesized chitosan derivative. In this study, antitumor activity and underlying mechanism of SSCC on human non-small-cell lung cancer A549 cells were investigated in vitro. The MTT assay showed that SSCC could inhibit cell viability in a dose- and time-dependent manner, and 200 μg/ml SSCC exhibited significantly toxic effects on A549 cells. The cell cycle assay showed that SSCC triggered S phase cell cycle arrest in a dose- and time-dependent manner, which was related to a downregulation of S phase associated cyclin A. The DAPI staining and Annexin V-FITC/PI double staining identified that the SSCC could induce A549 cells apoptosis. Further studies found that SSCC led to the generation of reactive oxygen species (ROS) and the disruption of mitochondrial membrane potential (MMP) by DCFH-DA and Rhodamin 123 staining, respectively. Meanwhile, free radical scavengers N-acetyl-L-cysteine (NAC) pretreatment confirmed that SSCC-induced A549 cells apoptosis was associated with ROS generation. Furthermore, real-time PCR and western blot assay showed that SSCC up-regulated Bax and down-regulated Bcl-2, subsequently incited the release of cytochrome c from mitochondria to cytoplasm, activated the increase of cleaved-caspase 3 and finally induced A549 cells apoptosis in vitro. In general, the present study demonstrated that SSCC induced A549 cells apoptosis via ROS-mediated mitochondrial apoptosis pathway.

Nickel (II)-induced cytotoxicity and apoptosis in human proximal tubule cells through a ROS- and mitochondria-mediated pathway

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yi-Fen; Shyu, Huey-Wen; Chang, Yi-Chuang

2012-03-01

Nickel compounds are known to be toxic and carcinogenic in kidney and lung. In this present study, we investigated the roles of reactive oxygen species (ROS) and mitochondria in nickel (II) acetate-induced cytotoxicity and apoptosis in the HK-2 human renal cell line. The results showed that the cytotoxic effects of nickel (II) involved significant cell death and DNA damage. Nickel (II) increased the generation of ROS and induced a noticeable reduction of mitochondrial membrane potential (MMP). Analysis of the sub-G1 phase showed a significant increase in apoptosis in HK-2 cells after nickel (II) treatment. Pretreatment with N-acetylcysteine (NAC) not onlymore » inhibited nickel (II)-induced cell death and DNA damage, but also significantly prevented nickel (II)-induced loss of MMP and apoptosis. Cell apoptosis triggered by nickel (II) was characterized by the reduced protein expression of Bcl-2 and Bcl-xL and the induced the protein expression of Bad, Bcl-Xs, Bax, cytochrome c and caspases 9, 3 and 6. The regulation of the expression of Bcl-2-family proteins, the release of cytochrome c and the activation of caspases 9, 3 and 6 were inhibited in the presence of NAC. These results suggest that nickel (II) induces cytotoxicity and apoptosis in HK-2 cells via ROS generation and that the mitochondria-mediated apoptotic signaling pathway may be involved in the positive regulation of nickel (II)-induced renal cytotoxicity.« less

Involvement of p38 MAPK- and JNK-modulated expression of Bcl-2 and Bax in Naja nigricollis CMS-9-induced apoptosis of human leukemia K562 cells.

PubMed

Chen, Ying-Jung; Liu, Wen-Hsin; Kao, Pei-Hsiu; Wang, Jeh-Jeng; Chang, Long-Sen

2010-06-15

CMS-9, a phospholipase A(2) (PLA(2)) isolated from Naja nigricollis venom, induced apoptosis of human leukemia K562 cells, characterized by mitochondrial depolarization, modulation of Bcl-2 family members, cytochrome c release and activation of caspases 9 and 3. Moreover, an increase in intracellular Ca2+ concentration and the production of reactive oxygen species (ROS) was noted. Pretreatment with BAPTA-AM (Ca2+ chelator) and N-acetylcysteine (NAC, ROS scavenger) proved that Ca2+ was an upstream event in inducing ROS generation. Upon exposure to CMS-9, activation of p38 MAPK and JNK was observed in K562 cells. BAPTA-AM or NAC abrogated CMS-9-elicited p38 MAPK and JNK activation, and rescued viability of CMS-9-treated K562 cells. SB202190 (p38 MAPK inhibitor) and SP600125 (JNK inhibitor) suppressed CMS-9-induced dissipation of mitochondrial membrane potential, Bcl-2 down-regulation, Bax up-regulation and increased mitochondrial translocation of Bax. Inactivation of PLA(2) activity reduced drastically the cytotoxicity of CMS-9, and a combination of lysophosphatidylcholine and stearic acid mimicked the cytotoxic effects of CMS-9. Taken together, our data suggest that CMS-9-induced apoptosis of K562 cells is catalytic activity-dependent and is mediated through mitochondria-mediated death pathway triggered by Ca2+/ROS-evoked p38 MAPK and JNK activation. 2010 Elsevier Ltd. All rights reserved.

Hexamethoxylated Monocarbonyl Analogues of Curcumin Cause G2/M Cell Cycle Arrest in NCI-H460 Cells via Michael Acceptor-Dependent Redox Intervention.

PubMed

Li, Yan; Zhang, Li-Ping; Dai, Fang; Yan, Wen-Jing; Wang, Hai-Bo; Tu, Zhi-Shan; Zhou, Bo

2015-09-09

Curcumin, derived from the dietary spice turmeric, holds promise for cancer prevention. This prompts much interest in investigating the action mechanisms of curcumin and its analogues. Two symmetrical hexamethoxy-diarylpentadienones (1 and 2) as cucumin analogues were reported to possess significantly enhanced cytotoxicity compared with the parent molecule. However, the detailed mechanisms remain unclear. In this study, compounds 1 and 2 were identified as the G2/M cell cycle arrest agents to mediate the cytotoxicity toward NCI-H460 cells via Michael acceptor-dependent redox intervention. Compared with curcumin, they could more easily induce a burst of reactive oxygen species (ROS) and collapse of the redox buffering system. One possible reason is that they could more effectively target intracellular TrxR to convert this antioxidant enzyme into a ROS promoter. Additionally, they caused up-regulation of p53 and p21 and down-regulation of redox-sensitive Cdc25C along with cyclin B1/Cdk1 in a Michael acceptor- and ROS-dependent fashion. Interestingly, in comparison with compound 2, compound 1 displayed a relatively weak ability to generate ROS but increased cell cycle arrest activity and cytotoxicity probably due to its Michael acceptor-dependent microtubule-destabilizing effect and greater GST-inhibitory activity, as well as its enhanced cellular uptake. This work provides useful information for understanding Michael acceptor-dependent and redox-mediated cytotoxic mechanisms of curcumin and its active analogues.

APE/Ref-1 makes fine-tuning of CD40-induced B cell proliferation.

PubMed

Merluzzi, Sonia; Gri, Giorgia; Gattei, Valter; Pagano, Michele; Pucillo, Carlo

2008-08-01

Apurinic/apyrimidinic endonuclease-1/Redox factor-1, a multifunctional DNA base excision repair and redox regulation enzyme, plays an important role in oxidative signalling, transcription factor regulation, and cell cycle control. Recently, we have demonstrated that following the triggering of CD40 on B cells, APE/Ref-1 translocates from the cytoplasm to the nucleus and regulates the activity of B cell-specific transcription factors. In the present paper we investigate whether APE/Ref-1 plays a role in controlling CD40-mediated B cell proliferation too. We demonstrate a concurrent increase in proliferation and decrease in apoptosis of primary mouse B cells activated by CD40 cross-linking and transfected with functional APE/Ref-1 antisense oligonucleotide. Moreover, we provide evidence that a redox-mediated signalling mechanism is involved in this process and we propose that APE/Ref-1, controlling the intracellular redox state, may also affect the cell cycle by inducing nucleus-cytoplasm redistribution of p21. Together, these findings suggest that APE/Ref-1 could act as a negative regulator in an adaptive response to elevated ROS levels following CD40 cross-linking. Considering the important role of ROS and APE/Ref-1 in CD40-mediated B cell proliferation, our data will contribute to understand the mechanisms of tumor escape and suggest APE/Ref-1 as a novel target for tumor therapeutic approaches.

APE/Ref-1 makes fine-tuning of CD40-induced B cell proliferation

PubMed Central

Merluzzi, Sonia; Gri, Giorgia; Gattei, Valter; Pagano, Michele; Pucillo, Carlo

2009-01-01

Apurinic/apyrimidinic endonuclease-1/Redox factor-1, a multifunctional DNA base excision repair and redox regulation enzyme, plays an important role in oxidative signalling, transcription factor regulation, and cell cycle control. Recently, we have demonstrated that following the triggering of CD40 on B cells, APE/Ref-1 translocates from the cytoplasm to the nucleus and regulates the activity of B cell-specific transcription factors. In the present paper we investigate whether APE/Ref-1 plays a role in controlling CD40-mediated B cell proliferation too. We demonstrate a concurrent increase in proliferation and decrease in apoptosis of primary mouse B cells activated by CD40 cross-linking and transfected with functional APE/Ref-1 antisense oligonucleotide. Moreover, we provide evidence that a redox-mediated signalling mechanism is involved in this process and we propose that APE/Ref-1, controlling the intracellular redox state, may also affect the cell cycle by inducing nucleus-cytoplasm redistribution of p21. Together, these findings suggest that APE/Ref-1 could act as a negative regulator in an adaptive response to elevated ROS levels following CD40 cross-linking. Considering the important role of ROS and APE/Ref-1 in CD40-mediated B cell proliferation, our data will contribute to understand the mechanisms of tumor escape and suggest APE/Ref-1 as a novel target for tumor therapeutic approaches. PMID:18617267

An ABA-mimicking ligand that reduces water loss and promotes drought resistance in plants

PubMed Central

Cao, Minjie; Liu, Xue; Zhang, Yan; Xue, Xiaoqian; Zhou, X Edward; Melcher, Karsten; Gao, Pan; Wang, Fuxing; Zeng, Liang; Zhao, Yang; Zhao, Yang; Deng, Pan; Zhong, Dafang; Zhu, Jian-Kang; Xu, H Eric; Xu, Yong

2013-01-01

Abscisic acid (ABA) is the most important hormone for plants to resist drought and other abiotic stresses. ABA binds directly to the PYR/PYL family of ABA receptors, resulting in inhibition of type 2C phosphatases (PP2C) and activation of downstream ABA signaling. It is envisioned that intervention of ABA signaling by small molecules could help plants to overcome abiotic stresses such as drought, cold and soil salinity. However, chemical instability and rapid catabolism by plant enzymes limit the practical application of ABA itself. Here we report the identification of a small molecule ABA mimic (AM1) that acts as a potent activator of multiple members of the family of ABA receptors. In Arabidopsis, AM1 activates a gene network that is highly similar to that induced by ABA. Treatments with AM1 inhibit seed germination, prevent leaf water loss, and promote drought resistance. We solved the crystal structure of AM1 in complex with the PYL2 ABA receptor and the HAB1 PP2C, which revealed that AM1 mediates a gate-latch-lock interacting network, a structural feature that is conserved in the ABA-bound receptor/PP2C complex. Together, these results demonstrate that a single small molecule ABA mimic can activate multiple ABA receptors and protect plants from water loss and drought stress. Moreover, the AM1 complex crystal structure provides a structural basis for designing the next generation of ABA-mimicking small molecules. PMID:23835477

Expression analysis of β-glucosidase genes that regulate abscisic acid homeostasis during watermelon (Citrullus lanatus) development and under stress conditions.

PubMed

Li, Qian; Li, Ping; Sun, Liang; Wang, Yanping; Ji, Kai; Sun, Yufei; Dai, Shengjie; Chen, Pei; Duan, Chaorui; Leng, Ping

2012-01-01

The aim of this study was to obtain new insights into the mechanisms that regulate endogenous abscisic acid (ABA) levels by β-glucosidase genes during the development of watermelons (Citrullus lanatus) and under drought stress conditions. In total, five cDNAs from watermelons were cloned by using reverse transcription-PCR (RT-PCR). They included three cDNAs (ClBG1, ClBG2 and ClBG3) homologous to those that encode β-glucosidase l that hydrolyzes the ABA glucose ester (ABA-GE) to release active ABA, ClNCED4, which encodes 9-cis-epoxycarotenoid dioxygenase (NCED), a key enzyme in ABA biosynthesis, and ClCYP707A1, encoding ABA 8'-hydroxylase. A BLAST homology search revealed that the sequences of cDNAs and the deduced amino acids of these genes showed a high degree of homology to comparable molecules of other plant species. During fruit development and ripening, the expressions of ClBG1, ClNCED4 and ClCYP707A1 were relatively low at an early stage, increased rapidly along with fruit ripening, and reached the highest levels at 27 days after full bloom (DAFB) at the harvest stage. This trend was consistent with the accumulation of ABA. The ClBG2 gene on the other hand was highly expressed at 5 DAFB, and then decreased gradually with fruit development. Unlike ClBG1 and ClBG2, the expression of ClBG3 was low at an early stage; its expression peak occurred at 15 DAFB and then declined to the lowest point. When watermelon seedlings were subjected to drought stress, expressions of ClBG1 and ClCYP707A1 were significantly down-regulated, while expressions of ClBG2 and ClNCED4 were up-regulated in the roots, stems and leaves. The expression of ClBG3 was down-regulated in root tissue, but was up-regulated in stems and leaves. In conclusion, endogenous ABA content was modulated by a dynamic balance between biosynthesis and catabolism regulated by ClNCED4, ClCYP707A1 and ClBGs during development and under drought stress condition. It seems likely that β-glucosidase genes are important for this regulation process. Copyright © 2011 Elsevier GmbH. All rights reserved.

Glutathione Efflux and Cell Death

PubMed Central

2012-01-01

Abstract Significance: Glutathione (GSH) depletion is a central signaling event that regulates the activation of cell death pathways. GSH depletion is often taken as a marker of oxidative stress and thus, as a consequence of its antioxidant properties scavenging reactive species of both oxygen and nitrogen (ROS/RNS). Recent Advances: There is increasing evidence demonstrating that GSH loss is an active phenomenon regulating the redox signaling events modulating cell death activation and progression. Critical Issues: In this work, we review the role of GSH depletion by its efflux, as an important event regulating alterations in the cellular redox balance during cell death independent from oxidative stress and ROS/RNS formation. We discuss the mechanisms involved in GSH efflux during cell death progression and the redox signaling events by which GSH depletion regulates the activation of the cell death machinery. Future Directions: The evidence summarized here clearly places GSH transport as a central mechanism mediating redox signaling during cell death progression. Future studies should be directed toward identifying the molecular identity of GSH transporters mediating GSH extrusion during cell death, and addressing the lack of sensitive approaches to quantify GSH efflux. Antioxid. Redox Signal. 17, 1694–1713. PMID:22656858

Oxygen Consumption and Usage During Physical Exercise: The Balance Between Oxidative Stress and ROS-Dependent Adaptive Signaling

PubMed Central

Zhao, Zhongfu; Koltai, Erika; Ohno, Hideki; Atalay, Mustafa

2013-01-01

Abstract The complexity of human DNA has been affected by aerobic metabolism, including endurance exercise and oxygen toxicity. Aerobic endurance exercise could play an important role in the evolution of Homo sapiens, and oxygen was not important just for survival, but it was crucial to redox-mediated adaptation. The metabolic challenge during physical exercise results in an elevated generation of reactive oxygen species (ROS) that are important modulators of muscle contraction, antioxidant protection, and oxidative damage repair, which at moderate levels generate physiological responses. Several factors of mitochondrial biogenesis, such as peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), mitogen-activated protein kinase, and SIRT1, are modulated by exercise-associated changes in the redox milieu. PGC-1α activation could result in decreased oxidative challenge, either by upregulation of antioxidant enzymes and/or by an increased number of mitochondria that allows lower levels of respiratory activity for the same degree of ATP generation. Endogenous thiol antioxidants glutathione and thioredoxin are modulated with high oxygen consumption and ROS generation during physical exercise, controlling cellular function through redox-sensitive signaling and protein–protein interactions. Endurance exercise-related angiogenesis, up to a significant degree, is regulated by ROS-mediated activation of hypoxia-inducible factor 1α. Moreover, the exercise-associated ROS production could be important to DNA methylation and post-translation modifications of histone residues, which create heritable adaptive conditions based on epigenetic features of chromosomes. Accumulating data indicate that exercise with moderate intensity has systemic and complex health-promoting effects, which undoubtedly involve regulation of redox homeostasis and signaling. Antioxid. Redox Signal. 18, 1208–1246. PMID:22978553

ROS dependent copper toxicity in Hydra-biochemical and molecular study.

PubMed

Zeeshan, Mohammed; Murugadas, Anbazhagan; Ghaskadbi, Surendra; Rajendran, Ramasamy Babu; Akbarsha, Mohammad Abdulkader

2016-01-01

Copper, an essential microelement, is known to be toxic to aquatic life at concentrations higher than that could be tolerated. Copper-induced oxidative stress has been documented in vitro, yet the in vivo effects of metal-induced oxidative stress have not been extensively studied in the lower invertebrates. The objective of the present study has been to find the effect of ROS-mediated toxicity of environmentally relevant concentrations of copper at organismal and cellular levels in Hydra magnipapillata. Exposure to copper at sublethal concentrations (0.06 and 0.1mg/L) for 24 or 48h resulted in generation of significant levels of intracellular reactive oxygen species (ROS). We infer that the free radicals here originate predominantly at the lysosomes but partly at the mitochondria also as visualized by H2-DHCFDA staining. Quantitative real-time PCR of RNA extracted from copper-exposed polyps revealed dose-dependent up-regulation of all antioxidant response genes (CAT, SOD, GPx, GST, GR, G6PD). Concurrent increase of Hsp70 and FoxO genes suggests the ability of polyps to respond to stress, which at 48h was not the same as at 24h. Interestingly, the transcript levels of all genes were down-regulated at 48h as compared to 24h incubation period. Comet assay indicated copper as a powerful genotoxicant, and the DNA damage was dose- as well as duration-dependent. Western blotting of proteins (Bax, Bcl-2 and caspase-3) confirmed ROS-mediated mitochondrial cell death in copper-exposed animals. These changes correlated well with changes in morphology, regeneration and aspects of reproduction. Taken together, the results indicate increased production of intracellular ROS in Hydra on copper exposure. Copyright © 2016 Elsevier Inc. All rights reserved.

Doxorubicin-induced necrosis is mediated by poly-(ADP-ribose) polymerase 1 (PARP1) but is independent of p53.

PubMed

Shin, Hyeon-Jun; Kwon, Hyuk-Kwon; Lee, Jae-Hyeok; Gui, Xiangai; Achek, Asma; Kim, Jae-Ho; Choi, Sangdun

2015-11-02

Necrosis, unregulated cell death, is characterized by plasma membrane rupture as well as nuclear and cellular swelling. However, it has recently been reported that necrosis is a regulated form of cell death mediated by poly-(ADP-ribose) polymerase 1 (PARP1). PARP1 is thought to mediate necrosis by inducing DNA damage, although this remains unconfirmed. In this study, we examined the mechanisms of PARP1-mediated necrosis following doxorubicin (DOX)-induced DNA damage in human kidney proximal tubular (HK-2) cells. DOX initiated DNA damage response (DDR) and upregulated PARP1 and p53 expression, resulting in morphological changes similar to those observed during necrosis. Additionally, DOX induced mitochondrial hyper-activation, as evidenced by increased mitochondrial respiration and cytosolic ATP (cATP) production. However, DOX affected mitochondrial mass. DOX-induced DNA damage, cytosolic reactive oxygen species (cROS) generation, and mitochondrial hyper-activation decreased in cells with inhibited PARP1 expression, while generation of nitric oxide (NO) and mitochondrial ROS (mROS) remained unaffected. Moreover, DOX-induced DNA damage, cell cycle changes, and oxidative stress were not affected by p53 inhibition. These findings suggest that DNA damage induced necrosis through a PARP1-dependent and p53-independent pathway.

Doxorubicin-induced necrosis is mediated by poly-(ADP-ribose) polymerase 1 (PARP1) but is independent of p53

PubMed Central

Shin, Hyeon-Jun; Kwon, Hyuk-Kwon; Lee, Jae-Hyeok; Gui, Xiangai; Achek, Asma; Kim, Jae-Ho; Choi, Sangdun

2015-01-01

Necrosis, unregulated cell death, is characterized by plasma membrane rupture as well as nuclear and cellular swelling. However, it has recently been reported that necrosis is a regulated form of cell death mediated by poly-(ADP-ribose) polymerase 1 (PARP1). PARP1 is thought to mediate necrosis by inducing DNA damage, although this remains unconfirmed. In this study, we examined the mechanisms of PARP1-mediated necrosis following doxorubicin (DOX)-induced DNA damage in human kidney proximal tubular (HK-2) cells. DOX initiated DNA damage response (DDR) and upregulated PARP1 and p53 expression, resulting in morphological changes similar to those observed during necrosis. Additionally, DOX induced mitochondrial hyper-activation, as evidenced by increased mitochondrial respiration and cytosolic ATP (cATP) production. However, DOX affected mitochondrial mass. DOX-induced DNA damage, cytosolic reactive oxygen species (cROS) generation, and mitochondrial hyper-activation decreased in cells with inhibited PARP1 expression, while generation of nitric oxide (NO) and mitochondrial ROS (mROS) remained unaffected. Moreover, DOX-induced DNA damage, cell cycle changes, and oxidative stress were not affected by p53 inhibition. These findings suggest that DNA damage induced necrosis through a PARP1-dependent and p53-independent pathway. PMID:26522181

Shikonin Isolated from Lithospermum erythrorhizon Downregulates Proinflammatory Mediators in Lipopolysaccharide-Stimulated BV2 Microglial Cells by Suppressing Crosstalk between Reactive Oxygen Species and NF-κB.

PubMed

Prasad, Rajapaksha Gedara; Choi, Yung Hyun; Kim, Gi-Young

2015-03-01

According to the expansion of lifespan, neuronal disorder based on inflammation has been social problem. Therefore, we isolated shikonin from Lithospermum erythrorhizon and evaluated anti-inflammatory effects of shikonin in lipopolysaccharide (LSP)-stimulated BV2 microglial cells. Shikonin dose-dependently inhibits the expression of the proinflammatory mediators, nitric oxide (NO), prostaglandin E2 (PGE2), and tumor necrosis factor-α (TNF-α) as well as their main regulatory genes and products such as inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and TNF-α in LPS-stimulated BV2 microglial cells. Additionally, shikonin suppressed the LPS-induced DNA-binding activity of nuclear factor-κB (NF-κB) to regulate the key regulatory genes of the proinflammatory mediators, such as iNOS, COX-2, and TNF-α, accompanied with downregulation of reactive oxygen species (ROS) generation. The results indicate that shikonin may downregulate the expression of proinflammatory genes involved in the synthesis of NO, PGE2, and TNF-α in LPS-treated BV2 microglial cells by suppressing ROS and NF-κB. Taken together, our results revealed that shikonin exerts downregulation of proinflammatory mediators by interference the ROS and NF-κB signaling pathway.

Shikonin Isolated from Lithospermum erythrorhizon Downregulates Proinflammatory Mediators in Lipopolysaccharide-Stimulated BV2 Microglial Cells by Suppressing Crosstalk between Reactive Oxygen Species and NF-κB

PubMed Central

Prasad, Rajapaksha Gedara; Choi, Yung Hyun; Kim, Gi-Young

2015-01-01

According to the expansion of lifespan, neuronal disorder based on inflammation has been social problem. Therefore, we isolated shikonin from Lithospermum erythrorhizon and evaluated anti-inflammatory effects of shikonin in lipopolysaccharide (LSP)-stimulated BV2 microglial cells. Shikonin dose-dependently inhibits the expression of the proinflammatory mediators, nitric oxide (NO), prostaglandin E2 (PGE2), and tumor necrosis factor-α (TNF-α) as well as their main regulatory genes and products such as inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and TNF-α in LPS-stimulated BV2 microglial cells. Additionally, shikonin suppressed the LPS-induced DNA-binding activity of nuclear factor-κB (NF-κB) to regulate the key regulatory genes of the proinflammatory mediators, such as iNOS, COX-2, and TNF-α, accompanied with downregulation of reactive oxygen species (ROS) generation. The results indicate that shikonin may downregulate the expression of proinflammatory genes involved in the synthesis of NO, PGE2, and TNF-α in LPS-treated BV2 microglial cells by suppressing ROS and NF-κB. Taken together, our results revealed that shikonin exerts downregulation of proinflammatory mediators by interference the ROS and NF-κB signaling pathway. PMID:25767678

Isolation and functional characterisation of two new bZIP maize regulators of the ABA responsive gene rab28.

PubMed

Nieva, Claudia; Busk, Peter K; Domínguez-Puigjaner, Eva; Lumbreras, Victoria; Testillano, Pilar S; Risueño, Maria-Carmen; Pagès, Montserrat

2005-08-01

The plant hormone abscisic acid regulates gene expression in response to growth stimuli and abiotic stress. Previous studies have implicated members of the bZIP family of transcription factors as mediators of abscisic acid dependent gene expression through the ABRE cis-element. Here, we identify two new maize bZIP transcription factors, EmBP-2 and ZmBZ-1 related to EmBP-1 and OsBZ-8 families. They are differentially expressed during embryo development; EmBP-2 is constitutive, whereas ZmBZ-1 is abscisic acid-inducible and accumulates during late embryogenesis. Both factors are nuclear proteins that bind to ABREs and activate transcription of the abscisic acid-inducible gene rab28 from maize. EmBP-2 and ZmBZ-1 are phosphorylated by protein kinase CK2 and phosphorylation alters their DNA binding properties. Our data suggest that EmBP-2 and ZmBZ-1 are involved in the expression of abscisic acid inducible genes such as rab28 and their activity is modulated by ABA and by phosphorylation.

Ubiad1 Is an Antioxidant Enzyme that Regulates eNOS Activity by CoQ10 Synthesis

PubMed Central

Mugoni, Vera; Postel, Ruben; Catanzaro, Valeria; De Luca, Elisa; Turco, Emilia; Digilio, Giuseppe; Silengo, Lorenzo; Murphy, Michael P.; Medana, Claudio; Stainier, Didier Y.R.; Bakkers, Jeroen; Santoro, Massimo M.

2013-01-01

Summary Protection against oxidative damage caused by excessive reactive oxygen species (ROS) by an antioxidant network is essential for the health of tissues, especially in the cardiovascular system. Here, we identified a gene with important antioxidant features by analyzing a null allele of zebrafish ubiad1, called barolo (bar). bar mutants show specific cardiovascular failure due to oxidative stress and ROS-mediated cellular damage. Human UBIAD1 is a nonmitochondrial prenyltransferase that synthesizes CoQ10 in the Golgi membrane compartment. Loss of UBIAD1 reduces the cytosolic pool of the antioxidant CoQ10 and leads to ROS-mediated lipid peroxidation in vascular cells. Surprisingly, inhibition of eNOS prevents Ubiad1-dependent cardiovascular oxidative damage, suggesting a crucial role for this enzyme and nonmitochondrial CoQ10 in NO signaling. These findings identify UBIAD1 as a nonmitochondrial CoQ10-forming enzyme with specific cardiovascular protective function via the modulation of eNOS activity. PMID:23374346

Synthesis and Biological Activity of 2',3'-iso-Aryl-abscisic Acid Analogs.

PubMed

Wan, Chuan; Wang, Mingan; Yang, Dongyan; Han, Xiaoqiang; Che, Chuanliang; Ding, Shanshan; Xiao, Yumei; Qin, Zhaohai

2017-12-15

2',3'- iso -Benzoabscisic acid ( iso -PhABA), an excellent selective abscisic acid (ABA) analog, was developed in our previous work. In order to find its more structure-activity information, some structural modifications were completed in this paper, including the substitution of phenyl ring and replacing the ring with heterocycles. Thus, 16 novel analogs of iso -PhABA were synthesized and screened with three bioassays, Arabidopsis and lettuce seed germination and rice seedling elongation. Some of them, i.e., 2',3'- iso -pyridoabscisic acid ( iso -PyABA) and 2',3'- iso -franoabscisic acid ( iso -FrABA), displayed good bioactivities that closed to iso -PhABA and natural (+)-ABA. Some others, for instance, substituted- iso -PhABA, exhibited certain selectivity to different physiological process when compared to iso -PhABA or (+)-ABA. These analogs not only provided new candidates of ABA-like synthetic plant growth regulators (PGRs) for practical application, but also new potential selective agonist/antagonist for probing the specific function of ABA receptors.

Peroxisome proliferator-activated receptor δ inhibits Porphyromonas gingivalis lipopolysaccharide-induced activation of matrix metalloproteinase-2 by downregulating NADPH oxidase 4 in human gingival fibroblasts.

PubMed

Yoo, T; Ham, S A; Hwang, J S; Lee, W J; Paek, K S; Oh, J W; Kim, J H; Do, J T; Han, C W; Kim, J H; Seo, H G

2016-10-01

We investigated the roles of peroxisome proliferator-activated receptor δ (PPARδ) in Porphyromonas gingivalis-derived lipopolysaccharide (Pg-LPS)-induced activation of matrix metalloproteinase 2 (MMP-2). In human gingival fibroblasts (HGFs), activation of PPARδ by GW501516, a specific ligand of PPARδ, inhibited Pg-LPS-induced activation of MMP-2 and generation of reactive oxygen species (ROS), which was associated with reduced expression of NADPH oxidase 4 (Nox4). These effects were significantly smaller in the presence of small interfering RNA targeting PPARδ or the specific PPARδ inhibitor GSK0660, indicating that PPARδ is involved in these events. In addition, modulation of Nox4 expression by small interfering RNA influenced the effect of PPARδ on MMP-2 activity, suggesting a mechanism in which Nox4-derived ROS modulates MMP-2 activity. Furthermore, c-Jun N-terminal kinase and p38, but not extracellular signal-regulated kinase, mediated PPARδ-dependent inhibition of MMP-2 activity in HGFs treated with Pg-LPS. Concomitantly, PPARδ-mediated inhibition of MMP-2 activity was associated with the restoration of types I and III collagen to levels approaching those in HGFs not treated with Pg-LPS. These results indicate that PPARδ-mediated downregulation of Nox4 modulates cellular redox status, which in turn plays a critical role in extracellular matrix homeostasis through ROS-dependent regulation of MMP-2 activity. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Optical studies of oxidative stress in pulmonary artery endothelial cells

NASA Astrophysics Data System (ADS)

Ghanian, Zahra; Sepehr, Reyhaneh; Eis, Annie; Kondouri, Ganesh; Ranji, Mahsa

2015-03-01

Reactive oxygen species (ROS) play an essential role in facilitating signal transduction processes within the cell and modulating the injuries. However, the generation of ROS is tightly controlled both spatially and temporally within the cell, making the study of ROS dynamics particularly difficult. This study present a novel protocol to quantify the dynamic of the mitochondrial superoxide as a precursor of reactive oxygen species. To regulate the mitochondrial superoxide level, metabolic perturbation was induced by administration of potassium cyanide (KCN). The presented method was able to monitor and measure the superoxide production rate over time. Our results demonstrated that the metabolic inhibitor, potassium cyanide (KCN) induced a significant increase in the rate of superoxide production in mitochondria of fetal pulmonary artery endothelial cells (FPAEC). Presented method sets the stage to study different ROS mediated injuries in vitro.

Redox signaling in the cardiomyocyte: From physiology to failure.

PubMed

Santos, Celio X C; Raza, Sadaf; Shah, Ajay M

2016-05-01

The specific effect of oxygen and reactive oxygen species (ROS) in mediating post-translational modification of protein targets has emerged as a key mechanism regulating signaling components, a process termed redox signaling. ROS act in the post-translational modification of multiple target proteins including receptors, kinases, phosphatases, ion channels and transcription factors. Both O2 and ROS are major source of electrons in redox reactions in aerobic organisms. Because the heart has the highest O2 consumption among body organs, it is not surprising that redox signaling is central to heart function and pathophysiology. In this article, we review some of the main cardiac redox signaling pathways and their roles in the cardiomyocyte and in heart failure, with particular focus on the specific molecular targets of ROS in the heart. Copyright © 2016 Elsevier Ltd. All rights reserved.

Nitric oxide signals ROS scavenger-mediated enhancement of PAL activity in nitrogen-deficient Matricaria chamomilla roots: side effects of scavengers.

PubMed

Kovácik, Jozef; Klejdus, Borivoj; Backor, Martin

2009-06-15

Owing to the abundance of phenolic metabolites in plant tissue, their accumulation represents an important tool for stress protection. However, the regulation of phenolic metabolism is still poorly known. The regulatory role of reactive oxygen species (ROS) in the activity of phenylalanine ammonia-lyase (PAL) in nitrogen (N)-deficient chamomile roots treated for 24 h was studied using three ROS scavengers [dithiothreitol (DTT), salicylhydroxamic acid, and sodium benzoate]. Scavengers decreased the level of hydrogen peroxide and/or superoxide (and up-regulated ascorbate/guaiacol peroxidase and glutathione reductase), but, surprisingly, stimulated PAL activity. This up-regulation was correlated with increases in nitric oxide (NO) content, total soluble phenols, selected phenolic acids, and, partially, lignin (being expressed the most in DTT-exposed roots). We therefore tested the hypothesis that NO may be involved in these changes. Application of 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) decreased PAL activity and the accumulation of soluble phenols in all treatments. Exogenous H(2)O(2) and NO also stimulated PAL activity and the accumulation of phenols. We conclude that NO, in addition to hydrogen peroxide, may regulate PAL activity during N deficiency. The anomalous effect of PTIO on NO content and possible mechanism of ROS scavenger-evoked NO increases in light of the current knowledge are also discussed.

Reactive Oxygen Species Generated by NADPH Oxidases Promote Radicle Protrusion and Root Elongation during Rice Seed Germination

PubMed Central

Li, Wen-Yan; Chen, Bing-Xian; Chen, Zhong-Jian; Gao, Yin-Tao; Chen, Zhuang; Liu, Jun

2017-01-01

Seed germination is a complicated biological process that requires regulation through various enzymatic and non-enzymatic mechanisms. Although it has been recognized that reactive oxygen species (ROS) regulate radicle emergence and root elongation in a non-enzymatic manner during dicot seed germination, the role of ROS in monocot seed germination remains unknown. NADPH oxidases (NOXs) are the major ROS producers in plants; however, whether and how NOXs regulate rice seed germination through ROS generation remains unclear. Here, we report that diphenyleneiodinium (DPI), a specific NOX inhibitor, potently inhibited embryo and seedling growth—especially that of the radicle and of root elongation—in a dose-dependent manner. Notably, the DPI-mediated inhibition of radicle and root growth could be eliminated by transferring seedlings from DPI to water. Furthermore, ROS production/accumulation during rice seed germination was quantified via histochemistry. Superoxide radicals (O2−), hydrogen peroxide (H2O2) and hydroxyl radicals (•OH) accumulated steadily in the coleorhiza, radicle and seedling root of germinating rice seeds. Expression profiles of the nine typical NOX genes were also investigated. According to quantitative PCR, OsNOX5, 7 and 9 were expressed relatively higher. When seeds were incubated in water, OsNOX5 expression progressively increased in the embryo from 12 to 48 h, whereas OsNOX7 and 9 expressions increased from 12 to 24 h and decreased thereafter. As expected, DPI inhibits the expression at predetermined time points for each of these genes. Taken together, these results suggest that ROS produced by NOXs are involved in radicle and root elongation during rice seed germination, and OsNOX5, 7 and 9 could play crucial roles in rice seed germination. These findings will facilitate further studies of the roles of ROS generated by NOXs during seed germination and seedling establishment and also provide valuable information for the regulation of NOX family gene expression in germinating seeds of monocot cereals. PMID:28098759

Light Inhibition of Shoot Regeneration Is Regulated by Endogenous Abscisic Acid Level in Calli Derived from Immature Barley Embryos

PubMed Central

Rikiishi, Kazuhide; Matsuura, Takakazu; Ikeda, Yoko; Maekawa, Masahiko

2015-01-01

Shoot regeneration in calli derived from immature barley embryos is regulated by light conditions during the callus-induction period. Barley cultivars Kanto Nijo-5 (KN5) and K-3 (K3) showed lower efficiency of shoot regeneration in a 16-h photoperiod during callus-induction than those in continuous darkness, whereas shoot regeneration was enhanced in cultures under a 16-h photoperiod in Golden Promise (GP) and Lenins (LN). These cultivars were classified as photo-inhibition type (KN5 and K3) or photo-induction type (GP and LN) according to their response to light. Contents of endogenous plant hormones were determined in calli cultured under a 16-h photoperiod and continuous darkness. In photo-inhibition type, higher accumulation of abscisic acid (ABA) was detected in calli cultured under a 16-h photoperiod, whereas calli showed lower levels of endogenous ABA in continuous darkness. However, cultivars of photo-induction type showed lower levels of ABA in calli cultured under both light conditions, similarly to photo-inhibition type in continuous darkness. Exogenous ABA inhibited the callus growth and shoot regeneration independent of light conditions in all cultivars. In photo-inhibition type, lower levels of endogenous ABA induced by ABA biosynthesis inhibitor, fluridone, reduced the photo-inhibition of shoot regeneration. Expression of ABA biosynthesis gene, HvNCED1, in calli was regulated by the light conditions. Higher expression was observed in calli cultured under a 16-h photoperiod. These results indicate that ABA biosynthesis could be activated through the higher expression of HvNCED1 in a 16-h photoperiod and that the higher accumulations of ABA inhibit shoot regeneration in the photo-inhibition type cultivars. PMID:26670930

Mouse lung fibroblasts are highly susceptible to necroptosis in a reactive oxygen species-dependent manner.

PubMed

Hussain, Muadh; Zimmermann, Vanessa; van Wijk, Sjoerd J L; Fulda, Simone

2018-07-01

Mouse embryonic fibroblasts (MEFs) have extensively been used to study necroptosis, a recently identified form of programmed cell death. However, very little is yet known about the role of necroptosis and its regulation by reactive oxygen species (ROS) in cell types naturally exposed to high oxygen levels such as mouse lung fibroblasts (MLFs). Here, we discover that MLFs are highly susceptible to undergo necroptosis in a ROS-dependent manner upon exposure to a prototypic death receptor-mediated necroptotic stimulus, i.e. cotreatment with tumor necrosis factor (TNF)α, Smac mimetic and the caspase inhibitor zVAD.fmk (TSZ). Kinetic analysis revealed that TSZ rapidly induces cell death in MLFs. Pharmacological inhibition of receptor-interacting protein kinase (RIPK)1 by necrostatin-1 (Nec-1) or RIPK3 by GSK'872 significantly rescues TSZ-stimulated cell death. Also, genetic silencing of RIPK3 or mixed lineage kinase domain-like pseudokinase (MLKL) significantly protects MLFs from TSZ-mediated cell death. Prior to cell death, TSZ significantly increases production of ROS. Importantly, addition of radical scavengers such as butylated hydroxyanisole (BHA) or α-Tocopherol (α-Toc) significantly suppresses TSZ-induced cell death in parallel with a significant reduction of ROS generation. Consistently, BHA prevented TSZ-triggered phosphorylation of MLKL similar to the addition of GSK'872. Thus, our study demonstrates for the first time that MLFs are prone to undergo necroptosis in response to a prototypic necroptotic stimulus and identifies ROS as important mediators of TSZ-triggered necroptosis. Copyright © 2018 Elsevier Inc. All rights reserved.

Shoot bending promotes flower bud formation by miRNA-mediated regulation in apple (Malus domestica Borkh.).

PubMed

Xing, Libo; Zhang, Dong; Zhao, Caiping; Li, Youmei; Ma, Juanjuan; An, Na; Han, Mingyu

2016-02-01

Flower induction in apple (Malus domestica Borkh.) trees plays an important life cycle role, but young trees produce fewer and inferior quality flower buds. Therefore, shoot bending has become an important cultural practice, significantly promoting the capacity to develop more flower buds during the growing seasons. Additionally, microRNAs (miRNAs) play essential roles in plant growth, flower induction and stress responses. In this study, we identified miRNAs potentially involved in the regulation of bud growth, and flower induction and development, as well as in the response to shoot bending. Of the 195 miRNAs identified, 137 were novel miRNAs. The miRNA expression profiles revealed that the expression levels of 68 and 27 known miRNAs were down-regulated and up-regulated, respectively, in response to shoot bending, and that the 31 differentially expressed novel miRNAs between them formed five major clusters. Additionally, a complex regulatory network associated with auxin, cytokinin, abscisic acid (ABA) and gibberellic acid (GA) plays important roles in cell division, bud growth and flower induction, in which related miRNAs and targets mediated regulation. Among them, miR396, 160, 393, and their targets associated with AUX, miR159, 319, 164, and their targets associated with ABA and GA, and flowering-related miRNAs and genes, regulate bud growth and flower bud formation in response to shoot bending. Meanwhile, the flowering genes had significantly higher expression levels during shoot bending, suggesting that they are involved in this regulatory process. This study provides a framework for the future analysis of miRNAs associated with multiple hormones and their roles in the regulation of bud growth, and flower induction and formation in response to shoot bending in apple trees. © 2015 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Overexpression of Poplar Pyrabactin Resistance-Like Abscisic Acid Receptors Promotes Abscisic Acid Sensitivity and Drought Resistance in Transgenic Arabidopsis.

PubMed

Yu, Jingling; Yang, Lei; Liu, Xiaobing; Tang, Renjie; Wang, Yuan; Ge, Haiman; Wu, Mengting; Zhang, Jiang; Zhao, Fugeng; Luan, Sheng; Lan, Wenzhi

2016-01-01

Drought stress is an important environmental factor limiting productivity of plants, especially fast growing species with high water consumption like poplar. Abscisic acid (ABA) is a phytohormone that positively regulates seed dormancy and drought resistance. The PYR1 (Pyrabactin Resistance 1)/ PYRL (PYR-Like)/ RCAR (Regulatory Component of ABA Receptor) (PYR/PYL/RCAR) ABA receptor family has been identified and widely characterized in Arabidopsis thaliana. However, their functions in poplars remain unknown. Here, we report that 2 of 14 PYR/PYL/RCAR orthologues in poplar (Populus trichocarpa) (PtPYRLs) function as a positive regulator of the ABA signal transduction pathway. The Arabidopsis transient expression and yeast two-hybrid assays showed the interaction among PtPYRL1 and PtPYRL5, a clade A protein phosphatase 2C, and a SnRK2, suggesting that a core signalling complex for ABA signaling pathway exists in poplars. Phenotypic analysis of PtPYRL1 and PtPYRL5 transgenic Arabidopsis showed that these two genes positively regulated the ABA responses during the seed germination. More importantly, the overexpression of PtPYRL1 and PtPYRL5 substantially improved ABA sensitivity and drought stress tolerance in transgenic plants. In summary, we comprehensively uncovered the properties of PtPYRL1 and PtPYRL5, which might be good target genes to genetically engineer drought-Resistant plants.

Redox regulation of mitochondrial function with emphasis on cysteine oxidation reactions☆

PubMed Central

Mailloux, Ryan J.; Jin, Xiaolei; Willmore, William G.

2013-01-01

Mitochondria have a myriad of essential functions including metabolism and apoptosis. These chief functions are reliant on electron transfer reactions and the production of ATP and reactive oxygen species (ROS). The production of ATP and ROS are intimately linked to the electron transport chain (ETC). Electrons from nutrients are passed through the ETC via a series of acceptor and donor molecules to the terminal electron acceptor molecular oxygen (O2) which ultimately drives the synthesis of ATP. Electron transfer through the respiratory chain and nutrient oxidation also produces ROS. At high enough concentrations ROS can activate mitochondrial apoptotic machinery which ultimately leads to cell death. However, if maintained at low enough concentrations ROS can serve as important signaling molecules. Various regulatory mechanisms converge upon mitochondria to modulate ATP synthesis and ROS production. Given that mitochondrial function depends on redox reactions, it is important to consider how redox signals modulate mitochondrial processes. Here, we provide the first comprehensive review on how redox signals mediated through cysteine oxidation, namely S-oxidation (sulfenylation, sulfinylation), S-glutathionylation, and S-nitrosylation, regulate key mitochondrial functions including nutrient oxidation, oxidative phosphorylation, ROS production, mitochondrial permeability transition (MPT), apoptosis, and mitochondrial fission and fusion. We also consider the chemistry behind these reactions and how they are modulated in mitochondria. In addition, we also discuss emerging knowledge on disorders and disease states that are associated with deregulated redox signaling in mitochondria and how mitochondria-targeted medicines can be utilized to restore mitochondrial redox signaling. PMID:24455476

Redox regulation of mitochondrial function with emphasis on cysteine oxidation reactions.

PubMed

Mailloux, Ryan J; Jin, Xiaolei; Willmore, William G

2014-01-01

Mitochondria have a myriad of essential functions including metabolism and apoptosis. These chief functions are reliant on electron transfer reactions and the production of ATP and reactive oxygen species (ROS). The production of ATP and ROS are intimately linked to the electron transport chain (ETC). Electrons from nutrients are passed through the ETC via a series of acceptor and donor molecules to the terminal electron acceptor molecular oxygen (O2) which ultimately drives the synthesis of ATP. Electron transfer through the respiratory chain and nutrient oxidation also produces ROS. At high enough concentrations ROS can activate mitochondrial apoptotic machinery which ultimately leads to cell death. However, if maintained at low enough concentrations ROS can serve as important signaling molecules. Various regulatory mechanisms converge upon mitochondria to modulate ATP synthesis and ROS production. Given that mitochondrial function depends on redox reactions, it is important to consider how redox signals modulate mitochondrial processes. Here, we provide the first comprehensive review on how redox signals mediated through cysteine oxidation, namely S-oxidation (sulfenylation, sulfinylation), S-glutathionylation, and S-nitrosylation, regulate key mitochondrial functions including nutrient oxidation, oxidative phosphorylation, ROS production, mitochondrial permeability transition (MPT), apoptosis, and mitochondrial fission and fusion. We also consider the chemistry behind these reactions and how they are modulated in mitochondria. In addition, we also discuss emerging knowledge on disorders and disease states that are associated with deregulated redox signaling in mitochondria and how mitochondria-targeted medicines can be utilized to restore mitochondrial redox signaling.

Integrins engage mitochondrial function for signal transduction by a mechanism dependent on Rho GTPases

PubMed Central

Werner, Erica; Werb, Zena

2002-01-01

We show here the transient activation of the small GTPase Rac, followed by a rise in reactive oxygen species (ROS), as necessary early steps in a signal transduction cascade that lead to NFκB activation and collagenase-1 (CL-1)/matrix metalloproteinase-1 production after integrin-mediated cell shape changes. We show evidence indicating that this constitutes a new mechanism for ROS production mediated by small GTPases. Activated RhoA also induced ROS production and up-regulated CL-1 expression. A Rac mutant (L37) that prevents reorganization of the actin cytoskeleton prevented integrin-induced CL-1 expression, whereas mutations that abrogate Rac binding to the neutrophil NADPH membrane oxidase in vitro (H26 and N130) did not. Instead, ROS were produced by integrin-induced changes in mitochondrial function, which were inhibited by Bcl-2 and involved transient membrane potential loss. The cells showing this transient decrease in mitochondrial membrane potential were already committed to CL-1 expression. These results unveil a new molecular mechanism of signal transduction triggered by integrin engagement where a global mitochondrial metabolic response leads to gene expression rather than apoptosis. PMID:12119354

Integrins engage mitochondrial function for signal transduction by a mechanism dependent on Rho GTPases.

PubMed

Werner, Erica; Werb, Zena

2002-07-22

We show here the transient activation of the small GTPase Rac, followed by a rise in reactive oxygen species (ROS), as necessary early steps in a signal transduction cascade that lead to NFkappaB activation and collagenase-1 (CL-1)/matrix metalloproteinase-1 production after integrin-mediated cell shape changes. We show evidence indicating that this constitutes a new mechanism for ROS production mediated by small GTPases. Activated RhoA also induced ROS production and up-regulated CL-1 expression. A Rac mutant (L37) that prevents reorganization of the actin cytoskeleton prevented integrin-induced CL-1 expression, whereas mutations that abrogate Rac binding to the neutrophil NADPH membrane oxidase in vitro (H26 and N130) did not. Instead, ROS were produced by integrin-induced changes in mitochondrial function, which were inhibited by Bcl-2 and involved transient membrane potential loss. The cells showing this transient decrease in mitochondrial membrane potential were already committed to CL-1 expression. These results unveil a new molecular mechanism of signal transduction triggered by integrin engagement where a global mitochondrial metabolic response leads to gene expression rather than apoptosis.

Interaction of Osmotic Stress, Temperature, and Abscisic Acid in the Regulation of Gene Expression in Arabidopsis

PubMed Central

Xiong, Liming; Ishitani, Manabu; Zhu, Jian-Kang

1999-01-01

The impact of simultaneous environmental stresses on plants and how they respond to combined stresses compared with single stresses is largely unclear. By using a transgene (RD29A-LUC) consisting of the firefly luciferase coding sequence (LUC) driven by the stress-responsive RD29A promoter, we investigated the interactive effects of temperature, osmotic stress, and the phytohormone abscisic acid (ABA) in the regulation of gene expression in Arabidopsis seedlings. Results indicated that both positive and negative interactions exist among the studied stress factors in regulating gene expression. At a normal growth temperature (22°C), osmotic stress and ABA act synergistically to induce the transgene expression. Low temperature inhibits the response to osmotic stress or to combined treatment of osmotic stress and ABA, whereas low temperature and ABA treatments are additive in inducing transgene expression. Although high temperature alone does not activate the transgene, it significantly amplifies the effects of ABA and osmotic stress. The effect of multiple stresses in the regulation of RD29A-LUC expression in signal transduction mutants was also studied. The results are discussed in the context of cold and osmotic stress signal transduction pathways. PMID:9880362

Melatonin-mediated upregulation of Sirt3 attenuates sodium fluoride-induced hepatotoxicity by activating the MT1-PI3K/AKT-PGC-1α signaling pathway.

PubMed

Song, Chao; Zhao, Jiamin; Fu, Beibei; Li, Dan; Mao, Tingchao; Peng, Wei; Wu, Haibo; Zhang, Yong

2017-11-01

Mitochondrial reactive oxygen species (ROS) production has been implicated in the pathogenesis of fluoride toxicity in liver. Melatonin, an indolamine synthesized in the pineal gland, was previously shown to protect against sodium fluoride (NaF)-induced hepatotoxicity. This study investigated the protective effects of melatonin pretreatment on NaF-induced hepatotoxicity and elucidates the potential mechanism of melatonin-mediated protection. Reducing mitochondrial ROS by melatonin substantially attenuated NaF-induced NADPH oxidase 4 (Nox4) upregulation and cytotoxicity in L-02 cells. Melatonin exerted its hepatoprotective effects by upregulating Sirtuin 3 (Sirt3) expression level and its activity. Melatonin increased the activity of manganese superoxide dismutase (SOD2) by promoting Sirt3-mediated deacetylation and promoted SOD2 expression through Sirt3-regulated DNA-binding activity of forkhead box O3 (FoxO3a), thus inhibiting the production of mitochondrial ROS induced by NaF. Notably, increased peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α) by melatonin activated the Sirt3 expression, which was regulated by an estrogen-related receptor (ERR) binding element (ERRE) mapped to Sirt3 promoter region. Analysis of the cell signaling pathway profiling systems and specific pathway inhibition indicated that melatonin enhances PGC-1α expression by activating the PI3K/AKT signaling pathway. Importantly, inhibition of melatonin receptor (MT)-1 blocked the melatonin-activated PI3K/AKT-PGC-1α-Sirt3 signaling. Mechanistic study revealed that the protective effects of melatonin were associated with down-regulation of JNK1/2 phosphorylation. Our findings provided a theoretical basis that melatonin mitigated NaF-induced hepatotoxicity, which, in part, was mediated through the activation of the Sirt3 pathway. Copyright © 2017 Elsevier Inc. All rights reserved.

Prx I Suppresses K-ras-Driven Lung Tumorigenesis by Opposing Redox-Sensitive ERK/Cyclin D1 Pathway

PubMed Central

Park, Young-Ho; Kim, Sun-Uk; Lee, Bo-Kyoung; Kim, Hyun-Sun; Song, In-Sung; Shin, Hye-Jun; Han, Ying-Hao; Chang, Kyu-Tae; Kim, Jin-Man; Lee, Dong-Seok; Kim, Yeul-Hong; Choi, Chang-Min; Kim, Bo-Yeon

2013-01-01

Abstract Aims: Coupled responses of mutated K-ras and oxidative stress are often an important etiological factor in non–small-cell lung cancer (NSCLC). However, relatively few studies have examined the control mechanism of oxidative stress in oncogenic K-ras-driven NSCLC progression. Here, we studied whether the redox signaling pathway governed by peroxiredoxin I (Prx I) is involved in K-rasG12D-mediated lung adenocarcinogenesis. Results: Using human-lung adenocarcinoma tissues and lung-specific K-rasG12D-transgenic mice, we found that Prx I was significantly up-regulated in the tumor regions via activation of nuclear erythroid 2-related factor 2 (Nrf2) transcription. Interestingly, the increased reactive oxygen species (ROS) by null mutation of Prx I greatly promoted K-rasG12D-driven lung tumorigenesis in number and size, which appeared to require the activation of the ROS-dependent extracellular signal-regulated kinase (ERK)/cyclin D1 pathway. Innovation: Taken together, these results suggest that Prx I functions as an Nrf2-dependently inducible tumor suppressant in K-ras-driven lung adenocarcinogenesis by opposing ROS/ERK/cyclin D1 pathway activation. Conclusion: These findings provide a better understanding of oxidative stress-mediated lung tumorigenesis. Antioxid. Redox Signal. 19, 482–496. PMID:23186333

A Central Role of Abscisic Acid in Stress-Regulated Carbohydrate Metabolism

PubMed Central

Kempa, Stefan; Krasensky, Julia; Dal Santo, Silvia; Kopka, Joachim; Jonak, Claudia

2008-01-01

Background Abiotic stresses adversely affect plant growth and development. The hormone abscisic acid (ABA) plays a central role in the response and adaptation to environmental constraints. However, apart from the well established role of ABA in regulating gene expression programmes, little is known about its function in plant stress metabolism. Principal Findings Using an integrative multiparallel approach of metabolome and transcriptome analyses, we studied the dynamic response of the model glyophyte Arabidopsis thaliana to ABA and high salt conditions. Our work shows that salt stress induces complex re-adjustment of carbohydrate metabolism and that ABA triggers the initial steps of carbon mobilisation. Significance These findings open new perspectives on how high salinity and ABA impact on central carbohydrate metabolism and highlight the power of iterative combinatorial approaches of non-targeted and hypothesis-driven experiments in stress biology. PMID:19081841

A transcription factor hierarchy defines an environmental stress response network.

PubMed

Song, Liang; Huang, Shao-Shan Carol; Wise, Aaron; Castanon, Rosa; Nery, Joseph R; Chen, Huaming; Watanabe, Marina; Thomas, Jerushah; Bar-Joseph, Ziv; Ecker, Joseph R

2016-11-04

Environmental stresses are universally encountered by microbes, plants, and animals. Yet systematic studies of stress-responsive transcription factor (TF) networks in multicellular organisms have been limited. The phytohormone abscisic acid (ABA) influences the expression of thousands of genes, allowing us to characterize complex stress-responsive regulatory networks. Using chromatin immunoprecipitation sequencing, we identified genome-wide targets of 21 ABA-related TFs to construct a comprehensive regulatory network in Arabidopsis thaliana Determinants of dynamic TF binding and a hierarchy among TFs were defined, illuminating the relationship between differential gene expression patterns and ABA pathway feedback regulation. By extrapolating regulatory characteristics of observed canonical ABA pathway components, we identified a new family of transcriptional regulators modulating ABA and salt responsiveness and demonstrated their utility to modulate plant resilience to osmotic stress. Copyright © 2016, American Association for the Advancement of Science.

The Arabidopsis KINβγ Subunit of the SnRK1 Complex Regulates Pollen Hydration on the Stigma by Mediating the Level of Reactive Oxygen Species in Pollen

PubMed Central

Zhao, Ting Ting; Li, Fei; Jia, Xiao Na; Zhao, Xin-Ying; Zhang, Xian Sheng

2016-01-01

Pollen–stigma interactions are essential for pollen germination. The highly regulated process of pollen germination includes pollen adhesion, hydration, and germination on the stigma. However, the internal signaling of pollen that regulates pollen–stigma interactions is poorly understood. KINβγ is a plant-specific subunit of the SNF1-related protein kinase 1 complex which plays important roles in the regulation of plant development. Here, we showed that KINβγ was a cytoplasm- and nucleus-localized protein in the vegetative cells of pollen grains in Arabidopsis. The pollen of the Arabidopsis kinβγ mutant could not germinate on stigma, although it germinated normally in vitro. Further analysis revealed the hydration of kinβγ mutant pollen on the stigma was compromised. However, adding water to the stigma promoted the germination of the mutant pollen in vivo, suggesting that the compromised hydration of the mutant pollen led to its defective germination. In kinβγ mutant pollen, the structure of the mitochondria and peroxisomes was destroyed, and their numbers were significantly reduced compared with those in the wild type. Furthermore, we found that the kinβγ mutant exhibited reduced levels of reactive oxygen species (ROS) in pollen. The addition of H2O2 in vitro partially compensated for the reduced water absorption of the mutant pollen, and reducing ROS levels in pollen by overexpressing Arabidopsis CATALASE 3 resulted in compromised hydration of pollen on the stigma. These results indicate that Arabidopsis KINβγ is critical for the regulation of ROS levels by mediating the biogenesis of mitochondria and peroxisomes in pollen, which is required for pollen–stigma interactions during pollination. PMID:27472382

Astaxanthin alleviates oxidative stress insults-related derangements in human vascular endothelial cells exposed to glucose fluctuations.

PubMed

Abdelzaher, Lobna A; Imaizumi, Takahiro; Suzuki, Tokiko; Tomita, Kengo; Takashina, Michinori; Hattori, Yuichi

2016-04-01

Glycemic fluctuations may play a critical role in the pathogenesis of diabetic complications, such as cardiovascular disease. We investigated whether the oxycarotenoid astaxanthin can reduce the detrimental effects of fluctuating glucose on vascular endothelial cells. Human umbilical venous endothelial cells were incubated for 3 days in media containing 5.5mM glucose, 22 mM glucose, or 5.5mM glucose alternating with 22 mM glucose in the absence or presence of astaxanthin or N-acetyl-L-cysteine (NAC). Constant high glucose increased reactive oxygen species (ROS) generation, but such an effect was more pronounced in fluctuating glucose. This was associated with up-regulated p22(phox) expression and down-regulated peroxisome proliferator activated receptor-γ coactivator (PGC-1α) expression. Astaxanthin inhibited ROS generation, p22(phox) up-regulation, and PGC-1α down-regulation by the stimuli of glucose fluctuation. Fluctuating glucose, but not constant high glucose, significantly decreased the endothelial nitric oxide synthase (eNOS) phosphorylation level at Ser-1177 without affecting total eNOS expression, which was prevented by astaxanthin as well as by the anti-oxidant NAC. Transferase-mediated dUTP nick end labeling (TUNEL) showed increased cell apoptosis in fluctuating glucose. Glucose fluctuation also resulted in up-regulating gene expression of pro-inflammatory mediators, interleukin-6 and intercellular adhesion molecule-1. These adverse changes were subdued by astaxanthin. The phosphorylation levels of c-Jun N-terminal kinase (JNK) and p38 were significantly increased by glucose fluctuations, and astaxanthin significantly inhibited the increase in JNK and p38 phosphorylation. Taken together, our results suggest that astaxanthin can protect vascular endothelial cells against glucose fluctuation by reducing ROS generation. Copyright © 2016 Elsevier Inc. All rights reserved.

Melatonin enhances lipid production in Monoraphidium sp. QLY-1 under nitrogen deficiency conditions via a multi-level mechanism.

PubMed

Zhao, Yongteng; Li, Dafei; Xu, Jun-Wei; Zhao, Peng; Li, Tao; Ma, Huixian; Yu, Xuya

2018-07-01

In this study, melatonin (MT) promoted lipid accumulation in Monoraphidium sp. QLY-1 under nitrogen deficiency conditions. The lipid accumulation increased 1.22- and 1.36-fold compared with a nitrogen-starved medium and a normal BG-11 medium, respectively. The maximum lipid content was 51.38%. The reactive oxygen species (ROS) level in the presence of melatonin was lower than that in the control group, likely because of the high antioxidant activities. The application of melatonin upregulated the gibberellin acid (GA) production and rbcL and accD expression levels but downregulated the abscisic acid (ABA) content and pepc expression levels. These findings demonstrated that exogenous melatonin could further improve the lipid production in Monoraphidium sp. QLY-1 by regulating antioxidant systems, signalling molecules, and lipid biosynthesis-related gene expression under nitrogen deficiency conditions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Alleviation of Drought Stress by Hydrogen Sulfide Is Partially Related to the Abscisic Acid Signaling Pathway in Wheat.

PubMed

Ma, Dongyun; Ding, Huina; Wang, Chenyang; Qin, Haixia; Han, Qiaoxia; Hou, Junfeng; Lu, Hongfang; Xie, Yingxin; Guo, Tiancai

2016-01-01

Little information is available describing the effects of exogenous H2S on the ABA pathway in the acquisition of drought tolerance in wheat. In this study, we investigated the physiological parameters, the transcription levels of several genes involved in the abscisic acid (ABA) metabolism pathway, and the ABA and H2S contents in wheat leaves and roots under drought stress in response to exogenous NaHS treatment. The results showed that pretreatment with NaHS significantly increased plant height and the leaf relative water content of seedlings under drought stress. Compared with drought stress treatment alone, H2S application increased antioxidant enzyme activities and reduced MDA and H2O2 contents in both leaves and roots. NaHS pretreatment increased the expression levels of ABA biosynthesis and ABA reactivation genes in leaves; whereas the expression levels of ABA biosynthesis and ABA catabolism genes were up-regulated in roots. These results indicated that ABA participates in drought tolerance induced by exogenous H2S, and that the responses in leaves and roots are different. The transcription levels of genes encoding ABA receptors were up-regulated in response to NaHS pretreatment under drought conditions in both leaves and roots. Correspondingly, the H2S contents in leaves and roots were increased by NaHS pretreatment, while the ABA contents of leaves and roots decreased. This implied that there is complex crosstalk between these two signal molecules, and that the alleviation of drought stress by H2S, at least in part, involves the ABA signaling pathway.

Alleviation of Drought Stress by Hydrogen Sulfide Is Partially Related to the Abscisic Acid Signaling Pathway in Wheat

PubMed Central

Wang, Chenyang; Qin, Haixia; Han, Qiaoxia; Hou, Junfeng; Lu, Hongfang; Xie, Yingxin; Guo, Tiancai

2016-01-01

Little information is available describing the effects of exogenous H2S on the ABA pathway in the acquisition of drought tolerance in wheat. In this study, we investigated the physiological parameters, the transcription levels of several genes involved in the abscisic acid (ABA) metabolism pathway, and the ABA and H2S contents in wheat leaves and roots under drought stress in response to exogenous NaHS treatment. The results showed that pretreatment with NaHS significantly increased plant height and the leaf relative water content of seedlings under drought stress. Compared with drought stress treatment alone, H2S application increased antioxidant enzyme activities and reduced MDA and H2O2 contents in both leaves and roots. NaHS pretreatment increased the expression levels of ABA biosynthesis and ABA reactivation genes in leaves; whereas the expression levels of ABA biosynthesis and ABA catabolism genes were up-regulated in roots. These results indicated that ABA participates in drought tolerance induced by exogenous H2S, and that the responses in leaves and roots are different. The transcription levels of genes encoding ABA receptors were up-regulated in response to NaHS pretreatment under drought conditions in both leaves and roots. Correspondingly, the H2S contents in leaves and roots were increased by NaHS pretreatment, while the ABA contents of leaves and roots decreased. This implied that there is complex crosstalk between these two signal molecules, and that the alleviation of drought stress by H2S, at least in part, involves the ABA signaling pathway. PMID:27649534

The transcriptional regulatory network in the drought response and its crosstalk in abiotic stress responses including drought, cold, and heat.

PubMed

Nakashima, Kazuo; Yamaguchi-Shinozaki, Kazuko; Shinozaki, Kazuo

2014-01-01

Drought negatively impacts plant growth and the productivity of crops around the world. Understanding the molecular mechanisms in the drought response is important for improvement of drought tolerance using molecular techniques. In plants, abscisic acid (ABA) is accumulated under osmotic stress conditions caused by drought, and has a key role in stress responses and tolerance. Comprehensive molecular analyses have shown that ABA regulates the expression of many genes under osmotic stress conditions, and the ABA-responsive element (ABRE) is the major cis-element for ABA-responsive gene expression. Transcription factors (TFs) are master regulators of gene expression. ABRE-binding protein and ABRE-binding factor TFs control gene expression in an ABA-dependent manner. SNF1-related protein kinases 2, group A 2C-type protein phosphatases, and ABA receptors were shown to control the ABA signaling pathway. ABA-independent signaling pathways such as dehydration-responsive element-binding protein TFs and NAC TFs are also involved in stress responses including drought, heat, and cold. Recent studies have suggested that there are interactions between the major ABA signaling pathway and other signaling factors in stress responses. The important roles of these TFs in crosstalk among abiotic stress responses will be discussed. Control of ABA or stress signaling factor expression can improve tolerance to environmental stresses. Recent studies using crops have shown that stress-specific overexpression of TFs improves drought tolerance and grain yield compared with controls in the field.

Redox regulation of plant stem cell fate.

PubMed

Zeng, Jian; Dong, Zhicheng; Wu, Haijun; Tian, Zhaoxia; Zhao, Zhong

2017-10-02

Despite the importance of stem cells in plant and animal development, the common mechanisms of stem cell maintenance in both systems have remained elusive. Recently, the importance of hydrogen peroxide (H 2 O 2 ) signaling in priming stem cell differentiation has been extensively studied in animals. Here, we show that different forms of reactive oxygen species (ROS) have antagonistic roles in plant stem cell regulation, which were established by distinct spatiotemporal patterns of ROS-metabolizing enzymes. The superoxide anion (O2·-) is markedly enriched in stem cells to activate WUSCHEL and maintain stemness, whereas H 2 O 2 is more abundant in the differentiating peripheral zone to promote stem cell differentiation. Moreover, H 2 O 2 negatively regulates O2·- biosynthesis in stem cells, and increasing H 2 O 2 levels or scavenging O2·- leads to the termination of stem cells. Our results provide a mechanistic framework for ROS-mediated control of plant stem cell fate and demonstrate that the balance between O2·- and H 2 O 2 is key to stem cell maintenance and differentiation. © 2017 The Authors.

Pepper protein phosphatase type 2C, CaADIP1 and its interacting partner CaRLP1 antagonistically regulate ABA signalling and drought response.

PubMed

Lim, Chae Woo; Lee, Sung Chul

2016-07-01

Abscisic acid (ABA) is a key phytohormone that regulates plant growth and developmental processes, including seed germination and stomatal closing. Here, we report the identification and functional characterization of a novel type 2C protein phosphatase, CaADIP1 (Capsicum annuum ABA and Drought-Induced Protein phosphatase 1). The expression of CaADIP1 was induced in pepper leaves by ABA, drought and NaCl treatments. Arabidopsis plants overexpressing CaADIP1 (CaADIP1-OX) exhibited an ABA-hyposensitive and drought-susceptible phenotype. We used a yeast two-hybrid screening assay to identify CaRLP1 (Capsicum annuum RCAR-Like Protein 1), which interacts with CaADIP1 in the cytoplasm and nucleus. In contrast to CaADIP1-OX plants, CaRLP1-OX plants displayed an ABA-hypersensitive and drought-tolerant phenotype, which was characterized by low levels of transpirational water loss and increased expression of stress-responsive genes relative to those of wild-type plants. In CaADIP1-OX/CaRLP1-OX double transgenic plants, ectopic expression of the CaRLP1 gene led to strong suppression of CaADIP1-induced ABA hyposensitivity during the germinative and post-germinative stages, indicating that CaADIP1 and CaRLP1 act in the same signalling pathway and CaADIP1 functions downstream of CaRLP1. Our results indicate that CaADIP1 and its interacting partner CaRLP1 antagonistically regulate the ABA-dependent defense signalling response to drought stress. © 2016 John Wiley & Sons Ltd.

The maize WRKY transcription factor ZmWRKY17 negatively regulates salt stress tolerance in transgenic Arabidopsis plants.

PubMed

Cai, Ronghao; Dai, Wei; Zhang, Congsheng; Wang, Yan; Wu, Min; Zhao, Yang; Ma, Qing; Xiang, Yan; Cheng, Beijiu

2017-12-01

We cloned and characterized the ZmWRKY17 gene from maize. Overexpression of ZmWRKY17 in Arabidopsis led to increased sensitivity to salt stress and decreased ABA sensitivity through regulating the expression of some ABA- and stress-responsive genes. The WRKY transcription factors have been reported to function as positive or negative regulators in many different biological processes including plant development, defense regulation and stress response. This study isolated a maize WRKY gene, ZmWRKY17, and characterized its role in tolerance to salt stress by generating transgenic Arabidopsis plants. Expression of the ZmWRKY17 was up-regulated by drought, salt and abscisic acid (ABA) treatments. ZmWRKY17 was localized in the nucleus with no transcriptional activation in yeast. Yeast one-hybrid assay showed that ZmWRKY17 can specifically bind to W-box, and it can activate W-box-dependent transcription in planta. Heterologous overexpression of ZmWRKY17 in Arabidopsis remarkably reduced plant tolerance to salt stress, as determined through physiological analyses of the cotyledons greening rate, root growth, relative electrical leakage and malondialdehyde content. Additionally, ZmWRKY17 transgenic plants showed decreased sensitivity to ABA during seed germination and early seedling growth. Transgenic plants accumulated higher content of ABA than wild-type (WT) plants under NaCl condition. Transcriptome and quantitative real-time PCR analyses revealed that some stress-related genes in transgenic seedlings showed lower expression level than that in the WT when treated with NaCl. Taken together, these results suggest that ZmWRKY17 may act as a negative regulator involved in the salt stress responses through ABA signalling.

Antagonistic effects of acetylshikonin on LPS-induced NO and PGE2 production in BV2 microglial cells via inhibition of ROS/PI3K/Akt-mediated NF-κB signaling and activation of Nrf2-dependent HO-1.

PubMed

Jayasooriya, Rajapaksha Gedara Prasad Tharanga; Lee, Kyoung-Tae; Choi, Yung Hyun; Moon, Sung-Kwon; Kim, Wun-Jae; Kim, Gi-Young

2015-10-01

Although acetylshikonin (ACS) is known to have antioxidant and antitumor activities, whether ACS regulates the expression of proinflammatory mediators in lipopolysaccharide (LPS)-stimulated microglial cells remains unclear. In this study, it was found that ACS isolated from Lithospermum erythrorhizon inhibits LPS-induced nitric oxide (NO) and prostaglandin E2 (PGE2) release by suppressing the expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) in BV2 microglial cells. Furthermore, ACS reduced the LPS-induced DNA-binding activity of nuclear factor-κB (NF-κB) and subsequently suppressed iNOS and COX-2 expression. Consistent with these data, ACS attenuated the phosphorylation of PI3K and Akt and suppressed the DNA-binding activity of NF-κB by inducing the generation of reactive oxygen species (ROS) in LPS-stimulated cells. In addition, ACS enhanced heme oxygenase-1 (HO-1) expression via nuclear factor-erythroid 2-related factor 2 (Nrf2) activation. Zinc protoporphyrin, a specific HO-1 inhibitor, partially attenuated the antagonistic effects of ACS on LPS-induced NO and PGE2 production. By contrast, the presence of cobalt protoporphyrin, a specific HO-1 inducer, potently suppressed LPS-induced NO and PGE2 production. These data indicate that ACS downregulates proinflammatory mediators such as NO and PGE2 by suppressing PI3K/Akt-dependent NF-κB activity induced by ROS as well as inducing Nrf2-dependent HO-1 activity. Taken together, ACS might be a good candidate to regulate LPS-mediated inflammatory diseases.

Reactive oxygen species regulate DNA copy number in isolated yeast mitochondria by triggering recombination-mediated replication.

PubMed

Hori, Akiko; Yoshida, Minoru; Shibata, Takehiko; Ling, Feng

2009-02-01

Mitochondrial DNA (mtDNA) encodes proteins that are essential for cellular ATP production. Reactive oxygen species (ROS) are respiratory byproducts that damage mtDNA and other cellular components. In Saccharomyces cerevisiae, the oxidized base excision-repair enzyme Ntg1 introduces a double-stranded break (DSB) at the mtDNA replication origin ori5; this DSB initiates the rolling-circle mtDNA replication mediated by the homologous DNA pairing protein Mhr1. Thus, ROS may play a role in the regulation of mtDNA copy number. Here, we show that the treatment of isolated mitochondria with low concentrations of hydrogen peroxide increased mtDNA copy number in an Ntg1- and Mhr1-dependent manner. This treatment elevated the DSB levels at ori5 of hypersuppressive [rho(-)] mtDNA only if Ntg1 was active. In vitro Ntg1-treatment of hypersuppressive [rho(-)] mtDNA extracted from hydrogen peroxide-treated mitochondria revealed increased oxidative modifications at ori5 loci. We also observed that purified Ntg1 created breaks in single-stranded DNA harboring oxidized bases, and that ori5 loci have single-stranded character. Furthermore, chronic low levels of hydrogen peroxide increased in vivo mtDNA copy number. We therefore propose that ROS act as a regulator of mtDNA copy number, acting through the Mhr1-dependent initiation of rolling-circle replication promoted by Ntg1-induced DSB in the single-stranded regions at ori5.

Abscisic Acid and abiotic stress signaling.

PubMed

Tuteja, Narendra

2007-05-01

Abiotic stress is severe environmental stress, which impairs crop production on irrigated land worldwide. Overall, the susceptibility or tolerance to the stress in plants is a coordinated action of multiple stress responsive genes, which also cross-talk with other components of stress signal transduction pathways. Plant responses to abiotic stress can be determined by the severity of the stress and by the metabolic status of the plant. Abscisic acid (ABA) is a phytohormone critical for plant growth and development and plays an important role in integrating various stress signals and controlling downstream stress responses. Plants have to adjust ABA levels constantly in responce to changing physiological and environmental conditions. To date, the mechanisms for fine-tuning of ABA levels remain elusive. The mechanisms by which plants respond to stress include both ABA-dependent and ABA-independent processes. Various transcription factors such as DREB2A/2B, AREB1, RD22BP1 and MYC/MYB are known to regulate the ABA-responsive gene expression through interacting with their corrosponding cis-acting elements such as DRE/CRT, ABRE and MYCRS/MYBRS, respectively. Understanding these mechanisms is important to improve stress tolerance in crops plants. This article first describes the general pathway for plant stress response followed by roles of ABA and transcription factors in stress tolerance including the regulation of ABA biosynthesis.

Abscisic Acid and Abiotic Stress Signaling

PubMed Central

2007-01-01

Abiotic stress is severe environmental stress, which impairs crop production on irrigated land worldwide. Overall, the susceptibility or tolerance to the stress in plants is a coordinated action of multiple stress responsive genes, which also cross-talk with other components of stress signal transduction pathways. Plant responses to abiotic stress can be determined by the severity of the stress and by the metabolic status of the plant. Abscisic acid (ABA) is a phytohormone critical for plant growth and development and plays an important role in integrating various stress signals and controlling downstream stress responses. Plants have to adjust ABA levels constantly in responce to changing physiological and environmental conditions. To date, the mechanisms for fine-tuning of ABA levels remain elusive. The mechanisms by which plants respond to stress include both ABA-dependent and ABA-independent processes. Various transcription factors such as DREB2A/2B, AREB1, RD22BP1 and MYC/MYB are known to regulate the ABA-responsive gene expression through interacting with their corrosponding cis-acting elements such as DRE/CRT, ABRE and MYCRS/MYBRS, respectively. Understanding these mechanisms is important to improve stress tolerance in crops plants. This article first describes the general pathway for plant stress response followed by roles of ABA and transcription factors in stress tolerance including the regulation of ABA biosynthesis. PMID:19516981

Sugar-mediated semidian oscillation of gene expression in the cassava storage root regulates starch synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jansson, Christer; Baguma, Yona; Sun, Chuanxin

Starch branching enzyme (SBE) activity in the cassava storage root exhibited a diurnal fluctuation, dictated by a transcriptional oscillation of the corresponding SBE genes. The peak of SBE activity coincided with the onset of sucrose accumulation in the storage, and we conclude that the oscillatory mechanism keeps the starch synthetic apparatus in the storage root sink in tune with the flux of sucrose from the photosynthetic source. When storage roots were uncoupled from the source, SBE expression could be effectively induced by exogenous sucrose. Turanose, a sucrose isomer that cannot be metabolized by plants, mimicked the effect of sucrose, demonstratingmore » that downstream metabolism of sucrose was not necessary for signal transmission. Also glucose and glucose-1-P induced SBE expression. Interestingly, induction by sucrose, turanose and glucose but not glucose-1-P sustained an overt semidian (12-h) oscillation in SBE expression and was sensitive to the hexokinase (HXK) inhibitor glucosamine. These results suggest a pivotal regulatory role for HXK during starch synthesis. Abscisic acid (ABA) was another potent inducer of SBE expression. Induction by ABA was similar to that of glucose-1-P in that it bypassed the semidian oscillator. Both the sugar and ABA signaling cascades were disrupted by okadaic acid, a protein phosphatase inhibitor. Based on these findings, we propose a model for sugar signaling in regulation of starch synthesis in the cassava storage root.« less

Increases in reactive oxygen species enhance vascular endothelial cell migration through a mechanism dependent on the transient receptor potential melastatin 4 ion channel.

PubMed

Sarmiento, Daniela; Montorfano, Ignacio; Cerda, Oscar; Cáceres, Mónica; Becerra, Alvaro; Cabello-Verrugio, Claudio; Elorza, Alvaro A; Riedel, Claudia; Tapia, Pablo; Velásquez, Luis A; Varela, Diego; Simon, Felipe

2015-03-01

A hallmark of severe inflammation is reactive oxygen species (ROS) overproduction induced by increased inflammatory mediators secretion. During systemic inflammation, inflammation mediators circulating in the bloodstream interact with endothelial cells (ECs) raising intracellular oxidative stress at the endothelial monolayer. Oxidative stress mediates several pathological functions, including an exacerbated EC migration. Because cell migration critically depends on calcium channel-mediated Ca(2+) influx, the molecular identification of the calcium channel involved in oxidative stress-modulated EC migration has been the subject of intense investigation. The transient receptor potential melastatin 4 (TRPM4) protein is a ROS-modulated non-selective cationic channel that performs several cell functions, including regulating intracellular Ca(2+) overload and Ca(2+) oscillation. This channel is expressed in multiple tissues, including ECs, and contributes to the migration of certain immune cells. However, whether the TRPM4 ion channel participates in oxidative stress-mediated EC migration is not known. Herein, we investigate whether oxidative stress initiates or enhances EC migration and study the role played by the ROS-modulated TRPM4 ion channel in oxidative stress-mediated EC migration. We demonstrate that oxidative stress enhances, but does not initiate, EC migration in a dose-dependent manner. Notably, we demonstrate that the TRPM4 ion channel is critical in promoting H2O2-enhanced EC migration. These results show that TRPM4 is a novel pharmacological target for the possible treatment of severe inflammation and other oxidative stress-mediated inflammatory diseases. Copyright © 2014 Elsevier Inc. All rights reserved.

Jasmonates: Multifunctional Roles in Stress Tolerance

PubMed Central

Ahmad, Parvaiz; Rasool, Saiema; Gul, Alvina; Sheikh, Subzar A.; Akram, Nudrat A.; Ashraf, Muhammad; Kazi, A. M.; Gucel, Salih

2016-01-01

Jasmonates (JAs) [Jasmonic acid (JA) and methyl jasmonates (MeJAs)] are known to take part in various physiological processes. Exogenous application of JAs so far tested on different plants under abiotic stresses particularly salinity, drought, and temperature (low/high) conditions have proved effective in improving plant stress tolerance. However, its extent of effectiveness entirely depends on the type of plant species tested or its concentration. The effects of introgression or silencing of different JA- and Me-JA-related genes have been summarized in this review, which have shown a substantial role in improving crop yield and quality in different plants under stress or non-stress conditions. Regulation of JAs synthesis is impaired in stressed as well as unstressed plant cells/tissues, which is believed to be associated with a variety of metabolic events including signal transduction. Although, mitogen activated protein kinases (MAPKs) are important components of JA signaling and biosynthesis pathways, nitric oxide, ROS, calcium, ABA, ethylene, and salicylic acid are also important mediators of plant growth and development during JA signal transduction and synthesis. The exploration of other signaling molecules can be beneficial to examine the details of underlying molecular mechanisms of JA signal transduction. Much work is to be done in near future to find the proper answers of the questions like action of JA related metabolites, and identification of universal JA receptors etc. Complete signaling pathways involving MAPKs, CDPK, TGA, SIPK, WIPK, and WRKY transcription factors are yet to be investigated to understand the complete mechanism of action of JAs. PMID:27379115

Ornithine Decarboxylase-Mediated Production of Putrescine Influences Ganoderic Acid Biosynthesis by Regulating Reactive Oxygen Species in Ganoderma lucidum

PubMed Central

Wu, Chen-Gao; Tian, Jia-Long; Liu, Rui; Cao, Peng-Fei; Zhang, Tian-Jun; Ren, Ang; Shi, Liang

2017-01-01

ABSTRACT Putrescine is an important polyamine that participates in a variety of stress responses. Ornithine decarboxylase (ODC) is a key enzyme that catalyzes the biosynthesis of putrescine. A homolog of the gene encoding ODC was cloned from Ganoderma lucidum. In the ODC-silenced strains, the transcript levels of the ODC gene and the putrescine content were significantly decreased. The ODC-silenced strains were more sensitive to oxidative stress. The content of ganoderic acid was increased by approximately 43 to 46% in the ODC-silenced strains. The content of ganoderic acid could be recovered after the addition of exogenous putrescine. Additionally, the content of reactive oxygen species (ROS) was significantly increased by approximately 1.3-fold in the ODC-silenced strains. The ROS content was significantly reduced after the addition of exogenous putrescine. The gene transcript levels and the activities of four major antioxidant enzymes were measured to further explore the effect of putrescine on the intracellular ROS levels. Further studies showed that the effect of the ODC-mediated production of putrescine on ROS might be a factor influencing the biosynthesis of ganoderic acid. Our study reports the role of putrescine in large basidiomycetes, providing a basis for future studies of the physiological functions of putrescine in microbes. IMPORTANCE It is well known that ODC and the ODC-mediated production of putrescine play an important role in resisting various environmental stresses, but there are few reports regarding the mechanisms underlying the effect of putrescine on secondary metabolism in microorganisms, particularly in fungi. G. lucidum is gradually becoming a model organism for studying environmental regulation and metabolism. In this study, a homolog of the gene encoding ODC was cloned in Ganoderma lucidum. We found that the transcript level of the ODC gene and the content of putrescine were significantly decreased in the ODC-silenced strains. The content of ganoderic acid was significantly increased in the ODC-silenced strains. Further studies showed that the effect of the ODC-mediated production of putrescine on ROS might be a factor influencing the biosynthesis of ganoderic acid. Our study reports the role of putrescine in large basidiomycetes, providing a basis for future studies of the physiological functions of putrescine in microbes. PMID:28802268