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Sample records for 1-2 affects arabidopsis

  1. Eukaryotic release factor 1-2 affects Arabidopsis responses to glucose and phytohormones during germination and early seedling development

    PubMed Central

    Zhou, Xiangjun; Cooke, Peter; Li, Li

    2010-01-01

    Germination and early seedling development are coordinately regulated by glucose and phytohormones such as ABA, GA, and ethylene. However, the molecules that affect plant responses to glucose and phytohormones remain to be fully elucidated. Eukaryotic release factor 1 (eRF1) is responsible for the recognition of the stop codons in mRNAs during protein synthesis. Accumulating evidence indicates that eRF1 functions in other processes in addition to translation termination. The physiological role of eRF1-2, a member of the eRF1 family, in Arabidopsis was examined here. The eRF1-2 gene was found to be specifically induced by glucose. Arabidopsis plants overexpressing eRF1-2 were hypersensitive to glucose during germination and early seedling development. Such hypersensitivity to glucose was accompanied by a dramatic reduction of the expression of glucose-regulated genes, chlorophyll a/b binding protein and plastocyanin. The hypersensitive response was not due to the enhanced accumulation of ABA. In addition, the eRF1-2 overexpressing plants showed increased sensitivity to paclobutrazol, an inhibitor of GA biosynthesis, and exogenous GA restored their normal growth. By contrast, the loss-of-function erf1-2 mutant exhibited resistance to paclobutrazol, suggesting that eRF1-2 may exert a negative effect on the GA signalling pathway. Collectively, these data provide evidence in support of a novel role of eRF1-2 in affecting glucose and phytohormone responses in modulating plant growth and development. PMID:19939886

  2. Eukaryotic release factor 1-2 affects Arabidopsis responses to glucose and phytohormones during germination and early seedling development

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Germination and early seedling development are coordinately regulated by glucose and phytohormones such as ABA, GA and ethylene. However, the molecules that affect plant responses to glucose and phytohormones remain to be fully elucidated. Eukaryotic release factor 1 (eRF1) is responsible for recogn...

  3. HY5 regulates nitrite reductase 1 (NIR1) and ammonium transporter1;2 (AMT1;2) in Arabidopsis seedlings.

    PubMed

    Huang, Lifen; Zhang, Hongcheng; Zhang, Huiyong; Deng, Xing Wang; Wei, Ning

    2015-09-01

    HY5 (Long Hypocotyles 5) is a key transcription factor in Arabidopsis thaliana that has a pivotal role in seedling development. Soil nitrogen is an essential macronutrient, and its uptake, assimilation and metabolism are influenced by nutrient availability and by lights. To understand the role of HY5 in nitrogen assimilation pathways, we examined the phenotype as well as the expression of selected nitrogen assimilation-related genes in hy5 mutant grown under various nitrogen limiting and nitrogen sufficient conditions, or different light conditions. We report that HY5 positively regulates nitrite reductase gene NIR1 and negatively regulates the ammonium transporter gene AMT1;2 under all nitrogen and light conditions tested, while it affects several other genes in a nitrogen supply-dependent manner. HY5 is not required for light induction of NIR1, AMT1;2 and NIA genes, but it is necessary for high level expression of NIR1 and NIA under optimal nutrient and light conditions. In addition, nitrogen deficiency exacerbates the abnormal root system of hy5. Together, our results suggest that HY5 exhibits the growth-promoting activity only when sufficient nutrients, including lights, are provided, and that HY5 has a complex involvement in nitrogen acquisition and metabolism in Arabidopsis seedlings. PMID:26259199

  4. Manipulation of hemoglobin expression affects Arabidopsis shoot organogenesis.

    PubMed

    Wang, Yaping; Elhiti, Mohamed; Hebelstrup, Kim H; Hill, Robert D; Stasolla, Claudio

    2011-10-01

    Over the past few years non-symbiotic plant hemoglobins have been described in a variety of plant species where they fulfill several functions ranging from detoxification processes to basic aspects of plant growth and post-embryonic development. To date no information is available on the role of hemoglobins during in vitro morphogenesis. Shoot organogenesis was induced in Arabidopsis lines constitutively expressing class 1, 2 and 3 hemoglobins (GLB1, 2 and 3) and lines in which the respective genes were either downregulated by RNAi (GLB1) or knocked out (GLB2 and GLB3). The process was executed by culturing root explants on an initial auxin-rich callus induction medium (CIM) followed by a transfer onto a cytokinin-containing shoot induction medium (SIM). While the repression of GLB2 inhibited organogenesis the over-expression of GLB1 or GLB2 enhanced the number of shoots produced in culture, and altered the transcript levels of genes participating in cytokinin perception and signalling. The up-regulation of GLB1 or GLB2 activated CKI1 and AHK3, genes encoding cytokinin receptors and affected the transcript levels of cytokinin responsive regulators (ARRs). The expression of Type-A ARRs (ARR4, 5, 7, 15, and 16), feed-back repressors of the cytokinin pathway, was repressed in both hemoglobin over-expressors whereas that of several Type-B ARRs (ARR2, 12, and 13), transcription activators of cytokinin-responsive genes, was induced. Such changes enhanced the sensitivity of the root explants to cytokinin allowing the 35S::GLB1 and 35S::GLB2 lines to produce shoots at low cytokinin concentrations which did not promote organogenesis in the WT line. These results show that manipulation of hemoglobin can modify shoot organogenesis in Arabidopsis and possibly in those systems partially or completely unresponsive to applications of exogenous cytokinins. PMID:21741261

  5. Arabidopsis nucleolin affects plant development and patterning.

    PubMed

    Petricka, Jalean Joyanne; Nelson, Timothy Mark

    2007-05-01

    Nucleolin is a major nucleolar protein implicated in many aspects of ribosomal biogenesis, including early events such as processing of the large 35S preribosomal RNA. We found that the Arabidopsis (Arabidopsis thaliana) parallel1 (parl1) mutant, originally identified by its aberrant leaf venation, corresponds to the Arabidopsis nucleolin gene. parl1 mutants display parallel leaf venation, aberrant localization of the provascular marker Athb8:beta-glucuronidase, the auxin-sensitive reporter DR5:beta-glucuronidase, and auxin-dependent growth defects. PARL1 is highly similar to the yeast (Saccharomyces cerevisiae) nucleolin NUCLEAR SIGNAL RECOGNITION 1 (NSR1) multifunctional protein; the Arabidopsis PARL1 gene can rescue growth defects of yeast nsr1 null mutants. This suggests that PARL1 protein may have roles similar to those of the yeast nucleolin in nuclear signal recognition, ribosomal processing, and ribosomal subunit accumulation. Based on the range of auxin-related defects in parl1 mutants, we propose that auxin-dependent organ growth and patterning is highly sensitive to the efficiency of nucleolin-dependent ribosomal processing. PMID:17369435

  6. Salt Stress Affects the Redox Status of Arabidopsis Root Meristems

    PubMed Central

    Jiang, Keni; Moe-Lange, Jacob; Hennet, Lauriane; Feldman, Lewis J.

    2016-01-01

    We report the redox status (profiles) for specific populations of cells that comprise the Arabidopsis root tip. For recently germinated, 3–5-day-old seedlings we show that the region of the root tip with the most reduced redox status includes the root cap initials, the quiescent center and the most distal portion of the proximal meristem, and coincides with (overlays) the region of the auxin maximum. As one moves basally, further into the proximal meristem, and depending on the growth conditions, the redox status becomes more oxidized, with a 5–10 mV difference in redox potential between the two borders delimiting the proximal meristem. At the point on the root axis at which cells of the proximal meristem cease division and enter the transition zone, the redox potential levels off, and remains more or less unchanged throughout the transition zone. As cells leave the transition zone and enter the zone of elongation the redox potentials become more oxidized. Treating roots with salt (50, 100, and 150 mM NaCl) results in marked changes in root meristem structure and development, and is preceded by changes in the redox profile, which flattens, and initially becomes more oxidized, with pronounced changes in the redox potentials of the root cap, the root cap initials and the quiescent center. Roots exposed to relatively mild levels of salt (<100 mM) are able to re-establish a normal, pre-salt treatment redox profile 3–6 days after exposure to salt. Coincident with the salt-associated changes in redox profiles are changes in the distribution of auxin transporters (AUX1, PIN1/2), which become more diffuse in their localization. We conclude that salt stress affects root meristem maintenance, in part, through changes in redox and auxin transport. PMID:26904053

  7. Flavonols Accumulate Asymmetrically and Affect Auxin Transport in Arabidopsis1[C][W][OA

    PubMed Central

    Kuhn, Benjamin M.; Geisler, Markus; Bigler, Laurent; Ringli, Christoph

    2011-01-01

    Flavonoids represent a class of secondary metabolites with diverse functions in plants including ultraviolet protection, pathogen defense, and interspecies communication. They are also known as modulators of signaling processes in plant and animal systems and therefore are considered to have beneficial effects as nutraceuticals. The rol1-2 (for repressor of lrx1) mutation of Arabidopsis (Arabidopsis thaliana) induces aberrant accumulation of flavonols and a cell-growth phenotype in the shoot. The hyponastic cotyledons, aberrant shape of pavement cells, and deformed trichomes in rol1-2 mutants are suppressed by blocking flavonoid biosynthesis, suggesting that the altered flavonol accumulation in these plants induces the shoot phenotype. Indeed, the identification of several transparent testa, myb, and fls1 (for flavonol synthase1) alleles in a rol1-2 suppressor screen provides genetic evidence that flavonols interfere with shoot development in rol1-2 seedlings. The increased accumulation of auxin in rol1-2 seedlings appears to be caused by a flavonol-induced modification of auxin transport. Quantification of auxin export from mesophyll protoplasts revealed that naphthalene-1-acetic acid but not indole-3-acetic acid transport is affected by the rol1-2 mutation. Inhibition of flavonol biosynthesis in rol1-2 fls1-3 restores naphthalene-1-acetic acid transport to wild-type levels, indicating a very specific mode of action of flavonols on the auxin transport machinery. PMID:21502189

  8. Transcriptome analysis of the aquaporin AtPIP1;2 deficient line in Arabidopsis thaliana

    PubMed Central

    Boudichevskaia, Anastassia; Heckwolf, Marlies; Althaus, Lea; Kaldenhoff, Ralf

    2015-01-01

    Atmospheric CO2 impacts all aspects of plant development. It has changed in the past and is predicted to change further on. Studies on the response of crop plants to low and elevated CO2 concerning growth, productivity and physiological processes are intense. In contrast, the molecular mechanisms of cellular CO2 exchange are still under discussion. At the same time it becomes more and more accepted that carbon dioxide is transported across cellular biomembranes by CO2 conducting aquaporins. Our recent study (Boudichevskaia et al., 2015) demonstrates that the lack of a single gene product – aquaporin AtPIP1;2 – resulted in massive transcriptional reprogramming in Arabidopsis as a consequence of reduced tissue CO2 diffusion rates. Therefore, the transcriptome data of the aquaporin AtPIP1;2 deficient line can be used in the comparative expression analyses for better understanding the role of aquaporins with regard to CO2 and water transport in plants. Here we describe a gene expression dataset generated for three biological replicates per genotype on Affymetrix platform. We provide detailed methods and analysis on microarray data which has been deposited in Gene Expression Omnibus (GEO): GSE62167. Additionally, we provide the R code for data preprocessing and quality control. PMID:26484207

  9. Dominance variation across six herbicides of the Arabidopsis thaliana csr1-1 and csr1-2 resistance alleles.

    PubMed

    Roux, Fabrice; Matéjicek, Annick; Gasquez, Jacques; Reboud, Xavier

    2005-11-01

    Dominance of a resistance trait can be defined as a measure of the relative position of the phenotype of the heterozygote RS compared with the phenotype of the two corresponding homozygotes, SS and RR. This parameter has been shown to have primary importance in the dynamics of pesticide resistance evolution. Literature on insecticide resistance suggests that dominance levels in the presence of insecticide vary greatly from completely recessive to completely dominant. With insecticides, both the chemical applied and the dosages used have been demonstrated to affect the dominance. By contrast, almost all herbicide resistances have been found to be inherited as partially to totally dominant traits. This discrepancy between weeds and insects may partly result from the methodologies applied to measure the dominance, ie a single dose for herbicide versus several doses for insecticide. Using two well-known resistances (csr1-1 and csr1-2) to acetolactate synthase (ALS) inhibitors in Arabidopsis thaliana (L) Heynh (mouse-ear cress), we used several herbicide doses to determine the dominance level to six ALS-inhibiting herbicides. The dominance level in the presence of herbicide varied from completely dominant to completely recessive, depending on the resistance allele and the herbicide tested. The dominance of the csr1-1 and csr1-2 resistance alleles ranged from 0 (completely recessive) to 1.1 (dominant) and from 0 to 0.3 (partially dominant), respectively. The recessivity of some resistance alleles in the presence of herbicide could lead to the development of improved resistance management in order to delay or avoid herbicide resistance evolution, especially in the control of outcrossing weed species. PMID:16007690

  10. A Nitrogen-Regulated Glutamine Amidotransferase (GAT1_2.1) Represses Shoot Branching in Arabidopsis[C][W

    PubMed Central

    Zhu, Huifen; Kranz, Robert G.

    2012-01-01

    Shoot branching in plants is regulated by many environmental cues and by specific hormones such as strigolactone (SL). We show that the GAT1_2.1 gene (At1g15040) is repressed over 50-fold by nitrogen stress, and is also involved in branching control. At1g15040 is predicted to encode a class I glutamine amidotransferase (GAT1), a superfamily for which Arabidopsis (Arabidopsis thaliana) has 30 potential members. Most members can be categorized into known biosynthetic pathways, for the amidation of known acceptor molecules (e.g. CTP synthesis). Some members, like GAT1_2.1, are of unknown function, likely involved in amidation of unknown acceptors. A gat1_2.1 mutant exhibits a significant increase in shoot branching, similar to mutants in SL biosynthesis. The results suggest that GAT1_2.1 is not involved in SL biosynthesis since exogenously applied GR24 (a synthetic SL) does not correct the mutant phenotype. The subfamily of GATs (GATase1_2), with At1g15040 as the founding member, appears to be present in all plants (including mosses), but not other organisms. This suggests a plant-specific function such as branching control. We discuss the possibility that the GAT1_2.1 enzyme may activate SLs (e.g. GR24) by amidation, or more likely could embody a new pathway for repression of branching. PMID:22885937

  11. The FRIABLE1 Gene Product Affects Cell Adhesion in Arabidopsis

    PubMed Central

    Neumetzler, Lutz; Humphrey, Tania; Lumba, Shelley; Snyder, Stephen; Yeats, Trevor H.; Usadel, Björn; Vasilevski, Aleksandar; Patel, Jignasha; Rose, Jocelyn K. C.; Persson, Staffan; Bonetta, Dario

    2012-01-01

    Cell adhesion in plants is mediated predominantly by pectins, a group of complex cell wall associated polysaccharides. An Arabidopsis mutant, friable1 (frb1), was identified through a screen of T-DNA insertion lines that exhibited defective cell adhesion. Interestingly, the frb1 plants displayed both cell and organ dissociations and also ectopic defects in organ separation. The FRB1 gene encodes a Golgi-localized, plant specific protein with only weak sequence similarities to known proteins (DUF246). Unlike other cell adhesion deficient mutants, frb1 mutants do not have reduced levels of adhesion related cell wall polymers, such as pectins. Instead, FRB1 affects the abundance of galactose- and arabinose-containing oligosaccharides in the Golgi. Furthermore, frb1 mutants displayed alteration in pectin methylesterification, cell wall associated extensins and xyloglucan microstructure. We propose that abnormal FRB1 action has pleiotropic consequences on wall architecture, affecting both the extensin and pectin matrices, with consequent changes to the biomechanical properties of the wall and middle lamella, thereby influencing cell-cell adhesion. PMID:22916179

  12. Phytochrome B affects responsiveness to gibberellins in Arabidopsis.

    PubMed Central

    Reed, J W; Foster, K R; Morgan, P W; Chory, J

    1996-01-01

    Plant responses to red and far-red light are mediated by a family of photoreceptors called phytochromes. Arabidopsis thaliana seedlings lacking one of the phytochromes, phyB, have elongated hypocotyls and other tissues, suggesting that they may have an alteration in hormone physiology. We have studied the possibility that phyB mutations affect seedling gibberellin (GA) perception and metabolism by testing the responsiveness of wild-type and phyB seedlings to exogenous GAs. The phyB mutant elongates more than the wild type in response to the same exogenous concentrations of GA3 or GA4, showing that the mutation causes an increase in responsiveness to GAs. Among GAs that we were able to detect, we found no significant difference in endogenous levels between wild-type and phyB mutant seedlings. However, GA4 levels were below our limit of detectability, and the concentration of that active GA could have varied between wild-type and phyB mutant seedlings. These results suggest that, although GAs are required for hypocotyl cell elongation, phyB does not act primarily by changing total seedling GA levels but rather by decreasing seedling responsiveness to GAs. PMID:8819329

  13. Carrageenans, Sulphated Polysaccharides of Red Seaweeds, Differentially Affect Arabidopsis thaliana Resistance to Trichoplusia ni (Cabbage Looper)

    PubMed Central

    Sangha, Jatinder S.; Khan, Wajahatullah; Ji, Xiuhong; Zhang, Junzeng; Mills, Aaron A. S.; Critchley, Alan T.; Prithiviraj, Balakrishnan

    2011-01-01

    Carrageenans are a collective family of linear, sulphated galactans found in a number of commercially important species of marine red alga. These polysaccharides are known to elicit defense responses in plant and animals and possess anti-viral properties. We investigated the effect of foliar application of ι-, κ- and λ-carrageenans (representing various levels of sulphation) on Arabidopsis thaliana in resistance to the generalist insect Trichoplusia ni (cabbage looper) which is known to cause serious economic losses in crop plants. Plants treated with ι- and κ-carrageenan showed reduced leaf damage, whereas those treated with λ- carrageenan were similar to that of the control. In a no-choice test, larval weight was reduced by more than 20% in ι- and κ- carrageenan treatments, but unaffected by λ-carrageenan. In multiple choice tests, carrageenan treated plants attracted fewer T. ni larvae by the fourth day following infestation as compared to the control. The application of carrageenans did not affect oviposition behaviour of T. ni. Growth of T. ni feeding on an artificial diet amended with carrageenans was not different from that fed with untreated control diet. ι-carrageenan induced the expression of defense genes; PR1, PDF1.2, and TI1, but κ- and λ-carrageenans did not. Besides PR1, PDF1.2, and TI1, the indole glucosinolate biosynthesis genes CYP79B2, CYP83B1 and glucosinolate hydrolysing QTL, ESM1 were up-regulated by ι-carrageenan treatment at 48 h post infestation. Gas chromatography-mass spectrometry analysis of carrageenan treated leaves showed increased concentrations of both isothiocyanates and nitriles. Taken together, these results show that carrageenans have differential effects on Arabidopsis resistance to T. ni and that the degree of sulphation of the polysaccharide chain may well mediate this effect. PMID:22046375

  14. Phytochrome B and REVEILLE1/2-mediated signalling controls seed dormancy and germination in Arabidopsis.

    PubMed

    Jiang, Zhimin; Xu, Gang; Jing, Yanjun; Tang, Weijiang; Lin, Rongcheng

    2016-01-01

    Seeds maintain a dormant state to withstand adverse conditions and germinate when conditions become favourable to give rise to a new generation of flowering plants. Seed dormancy and germination are tightly controlled by internal and external signals. Although phytochrome photoreceptors are proposed to regulate primary seed dormancy, the underlying molecular mechanism remains elusive. Here we show that the REVEILLE1 (RVE1) and RVE2 transcription factors promote primary seed dormancy and repress red/far-red-light-reversible germination downstream of phytochrome B (phyB) in Arabidopsis thaliana. RVE1 and RVE2 expression is downregulated after imbibition and by phyB. RVE1 directly binds to the promoter of GIBBERELLIN 3-OXIDASE 2, inhibits its transcription and thus suppresses the biosynthesis of bioactive gibberellins. In addition, DELAY OF GERMINATION 1 also acts downstream of phyB. This study identifies a signalling pathway that integrates environmental light input with internal factors to control both seed dormancy and germination. PMID:27506149

  15. Phytochrome B and REVEILLE1/2-mediated signalling controls seed dormancy and germination in Arabidopsis

    PubMed Central

    Jiang, Zhimin; Xu, Gang; Jing, Yanjun; Tang, Weijiang; Lin, Rongcheng

    2016-01-01

    Seeds maintain a dormant state to withstand adverse conditions and germinate when conditions become favourable to give rise to a new generation of flowering plants. Seed dormancy and germination are tightly controlled by internal and external signals. Although phytochrome photoreceptors are proposed to regulate primary seed dormancy, the underlying molecular mechanism remains elusive. Here we show that the REVEILLE1 (RVE1) and RVE2 transcription factors promote primary seed dormancy and repress red/far-red-light-reversible germination downstream of phytochrome B (phyB) in Arabidopsis thaliana. RVE1 and RVE2 expression is downregulated after imbibition and by phyB. RVE1 directly binds to the promoter of GIBBERELLIN 3-OXIDASE 2, inhibits its transcription and thus suppresses the biosynthesis of bioactive gibberellins. In addition, DELAY OF GERMINATION 1 also acts downstream of phyB. This study identifies a signalling pathway that integrates environmental light input with internal factors to control both seed dormancy and germination. PMID:27506149

  16. Zinc Oxide Nanoparticles Affect Biomass Accumulation and Photosynthesis in Arabidopsis

    PubMed Central

    Wang, Xiaoping; Yang, Xiyu; Chen, Siyu; Li, Qianqian; Wang, Wei; Hou, Chunjiang; Gao, Xiao; Wang, Li; Wang, Shucai

    2016-01-01

    Dramatic increase in the use of nanoparticles (NPs) in a variety of applications greatly increased the likelihood of the release of NPs into the environment. Zinc oxide nanoparticles (ZnO NPs) are among the most commonly used NPs, and it has been shown that ZnO NPs were harmful to several different plants. We report here the effects of ZnO NPs exposure on biomass accumulation and photosynthesis in Arabidopsis. We found that 200 and 300 mg/L ZnO NPs treatments reduced Arabidopsis growth by ∼20 and 80%, respectively, in comparison to the control. Pigments measurement showed that Chlorophyll a and b contents were reduced more than 50%, whereas carotenoid contents remain largely unaffected in 300 mg/L ZnO NPs treated Arabidopsis plants. Consistent with this, net rate of photosynthesis, leaf stomatal conductance, intercellular CO2 concentration and transpiration rate were all reduced more than 50% in 300 mg/L ZnO NPs treated plants. Quantitative RT-PCR results showed that expression levels of chlorophyll synthesis genes including CHLOROPHYLL A OXYGENASE (CAO), CHLOROPHYLL SYNTHASE (CHLG), COPPER RESPONSE DEFECT 1 (CRD1), MAGNESIUM-PROTOPORPHYRIN IX METHYLTRANSFERASE (CHLM) and MG-CHELATASE SUBUNIT D (CHLD), and photosystem structure gene PHOTOSYSTEM I SUBUNIT D-2 (PSAD2), PHOTOSYSTEM I SUBUNIT E-2 (PSAE2), PHOTOSYSTEM I SUBUNIT K (PSAK) and PHOTOSYSTEM I SUBUNIT K (PSAN) were reduced about five folds in 300 mg/L ZnO NPs treated plants. On the other hand, elevated expression, though to different degrees, of several carotenoids synthesis genes including GERANYLGERANYL PYROPHOSPHATE SYNTHASE 6 (GGPS6), PHYTOENE SYNTHASE (PSY) PHYTOENE DESATURASE (PDS), and ZETA-CAROTENE DESATURASE (ZDS) were observed in ZnO NPs treated plants. Taken together, these results suggest that toxicity effects of ZnO NPs observed in Arabidopsis was likely due to the inhibition of the expression of chlorophyll synthesis genes and photosystem structure genes, which results in the inhibition of

  17. Zinc Oxide Nanoparticles Affect Biomass Accumulation and Photosynthesis in Arabidopsis.

    PubMed

    Wang, Xiaoping; Yang, Xiyu; Chen, Siyu; Li, Qianqian; Wang, Wei; Hou, Chunjiang; Gao, Xiao; Wang, Li; Wang, Shucai

    2015-01-01

    Dramatic increase in the use of nanoparticles (NPs) in a variety of applications greatly increased the likelihood of the release of NPs into the environment. Zinc oxide nanoparticles (ZnO NPs) are among the most commonly used NPs, and it has been shown that ZnO NPs were harmful to several different plants. We report here the effects of ZnO NPs exposure on biomass accumulation and photosynthesis in Arabidopsis. We found that 200 and 300 mg/L ZnO NPs treatments reduced Arabidopsis growth by ∼20 and 80%, respectively, in comparison to the control. Pigments measurement showed that Chlorophyll a and b contents were reduced more than 50%, whereas carotenoid contents remain largely unaffected in 300 mg/L ZnO NPs treated Arabidopsis plants. Consistent with this, net rate of photosynthesis, leaf stomatal conductance, intercellular CO2 concentration and transpiration rate were all reduced more than 50% in 300 mg/L ZnO NPs treated plants. Quantitative RT-PCR results showed that expression levels of chlorophyll synthesis genes including CHLOROPHYLL A OXYGENASE (CAO), CHLOROPHYLL SYNTHASE (CHLG), COPPER RESPONSE DEFECT 1 (CRD1), MAGNESIUM-PROTOPORPHYRIN IX METHYLTRANSFERASE (CHLM) and MG-CHELATASE SUBUNIT D (CHLD), and photosystem structure gene PHOTOSYSTEM I SUBUNIT D-2 (PSAD2), PHOTOSYSTEM I SUBUNIT E-2 (PSAE2), PHOTOSYSTEM I SUBUNIT K (PSAK) and PHOTOSYSTEM I SUBUNIT K (PSAN) were reduced about five folds in 300 mg/L ZnO NPs treated plants. On the other hand, elevated expression, though to different degrees, of several carotenoids synthesis genes including GERANYLGERANYL PYROPHOSPHATE SYNTHASE 6 (GGPS6), PHYTOENE SYNTHASE (PSY) PHYTOENE DESATURASE (PDS), and ZETA-CAROTENE DESATURASE (ZDS) were observed in ZnO NPs treated plants. Taken together, these results suggest that toxicity effects of ZnO NPs observed in Arabidopsis was likely due to the inhibition of the expression of chlorophyll synthesis genes and photosystem structure genes, which results in the inhibition of

  18. Seed Production Affects Maternal Growth and Senescence in Arabidopsis.

    PubMed

    Wuest, Samuel Elias; Philipp, Matthias Anton; Guthörl, Daniela; Schmid, Bernhard; Grossniklaus, Ueli

    2016-05-01

    Correlative control (influence of one organ over another organ) of seeds over maternal growth is one of the most obvious phenotypic expressions of the trade-off between growth and reproduction. However, the underlying molecular mechanisms are largely unknown. Here, we characterize the physiological and molecular effects of correlative inhibition by seeds on Arabidopsis (Arabidopsis thaliana) inflorescences, i.e. global proliferative arrest (GPA) during which all maternal growth ceases upon the production of a given number of seeds. We observed transcriptional responses to growth- and branching-inhibitory hormones, and low mitotic activity in meristems upon GPA, but found that meristems retain their identity and proliferative potential. In shoot tissues, we detected the induction of stress- and senescence-related gene expression upon fruit production and GPA, and a drop in chlorophyll levels, suggestive of altered source-sink relationships between vegetative shoot and reproductive tissues. Levels of shoot reactive oxygen species, however, strongly decreased upon GPA, a phenomenon that is associated with bud dormancy in some perennials. Indeed, gene expression changes in arrested apical inflorescences after fruit removal resembled changes observed in axillary buds following release from apical dominance. This suggests that GPA represents a form of bud dormancy, and that dominance is gradually transferred from growing inflorescences to maturing seeds, allowing offspring control over maternal resources, simultaneously restricting offspring number. This would provide a mechanistic explanation for the constraint between offspring quality and quantity. PMID:27009281

  19. Allyl isothiocyanate affects the cell cycle of Arabidopsis thaliana

    PubMed Central

    Åsberg, Signe E.; Bones, Atle M.; Øverby, Anders

    2015-01-01

    Isothiocyanates (ITCs) are degradation products of glucosinolates present in members of the Brassicaceae family acting as herbivore repellents and antimicrobial compounds. Recent results indicate that allyl ITC (AITC) has a role in defense responses such as glutathione depletion, ROS generation and stomatal closure. In this study we show that exposure to non-lethal concentrations of AITC causes a shift in the cell cycle distribution of Arabidopsis thaliana leading to accumulation of cells in S-phases and a reduced number of cells in non-replicating phases. Furthermore, transcriptional analysis revealed an AITC-induced up-regulation of the gene encoding cyclin-dependent kinase A while several genes encoding mitotic proteins were down-regulated, suggesting an inhibition of mitotic processes. Interestingly, visualization of DNA synthesis indicated that exposure to AITC reduced the rate of DNA replication. Taken together, these results indicate that non-lethal concentrations of AITC induce cells of A. thaliana to enter the cell cycle and accumulate in S-phases, presumably as a part of a defensive response. Thus, this study suggests that AITC has several roles in plant defense and add evidence to the growing data supporting a multifunctional role of glucosinolates and their degradation products in plants. PMID:26042144

  20. Gibberellins inhibit adventitious rooting in hybrid aspen and Arabidopsis by affecting auxin transport.

    PubMed

    Mauriat, Mélanie; Petterle, Anna; Bellini, Catherine; Moritz, Thomas

    2014-05-01

    Knowledge of processes involved in adventitious rooting is important to improve both fundamental understanding of plant physiology and the propagation of numerous plants. Hybrid aspen (Populus tremula × tremuloïdes) plants overexpressing a key gibberellin (GA) biosynthesis gene (AtGA20ox1) grow rapidly but have poor rooting efficiency, which restricts their clonal propagation. Therefore, we investigated the molecular basis of adventitious rooting in Populus and the model plant Arabidopsis. The production of adventitious roots (ARs) in tree cuttings is initiated from the basal stem region, and involves the interplay of several endogenous and exogenous factors. The roles of several hormones in this process have been characterized, but the effects of GAs have not been fully investigated. Here, we show that a GA treatment negatively affects the numbers of ARs produced by wild-type hybrid aspen cuttings. Furthermore, both hybrid aspen plants and intact Arabidopsis seedlings overexpressing AtGA20ox1, PttGID1.1 or PttGID1.3 genes (with a 35S promoter) produce few ARs, although ARs develop from the basal stem region of hybrid aspen and the hypocotyl of Arabidopsis. In Arabidopsis, auxin and strigolactones are known to affect AR formation. Our data show that the inhibitory effect of GA treatment on adventitious rooting is not mediated by perturbation of the auxin signalling pathway, or of the strigolactone biosynthetic and signalling pathways. Instead, GAs appear to act by perturbing polar auxin transport, in particular auxin efflux in hybrid aspen, and both efflux and influx in Arabidopsis. PMID:24547703

  1. Post-Synthetic Defucosylation of AGP by Aspergillus nidulans α-1,2-Fucosidase Expressed in Arabidopsis Apoplast Induces Compensatory Upregulation of α-1,2-Fucosyltransferases

    PubMed Central

    Pogorelko, Gennady V.; Reem, Nathan T.; Young, Zachary T.; Chambers, Lauran; Zabotina, Olga A.

    2016-01-01

    Cell walls are essential components of plant cells which perform a variety of important functions for the different cell types, tissues and organs of a plant. Besides mechanical function providing cell shape, cell walls participate in intercellular communication, defense during plant-microbe interactions, and plant growth. The plant cell wall consists predominantly of polysaccharides with the addition of structural glycoproteins, phenolic esters, minerals, lignin, and associated enzymes. Alterations in the cell wall composition created through either changes in biosynthesis of specific constituents or their post-synthetic modifications in the apoplast compromise cell wall integrity and frequently induce plant compensatory responses as a result of these alterations. Here we report that post-synthetic removal of fucose residues specifically from arabinogalactan proteins in the Arabidopsis plant cell wall induces differential expression of fucosyltransferases and leads to the root and hypocotyl elongation changes. These results demonstrate that the post-synthetic modification of cell wall components presents a valuable approach to investigate the potential signaling pathways induced during plant responses to such modifications that usually occur during plant development and stress responses. PMID:27448235

  2. Post-Synthetic Defucosylation of AGP by Aspergillus nidulans α-1,2-Fucosidase Expressed in Arabidopsis Apoplast Induces Compensatory Upregulation of α-1,2-Fucosyltransferases.

    PubMed

    Pogorelko, Gennady V; Reem, Nathan T; Young, Zachary T; Chambers, Lauran; Zabotina, Olga A

    2016-01-01

    Cell walls are essential components of plant cells which perform a variety of important functions for the different cell types, tissues and organs of a plant. Besides mechanical function providing cell shape, cell walls participate in intercellular communication, defense during plant-microbe interactions, and plant growth. The plant cell wall consists predominantly of polysaccharides with the addition of structural glycoproteins, phenolic esters, minerals, lignin, and associated enzymes. Alterations in the cell wall composition created through either changes in biosynthesis of specific constituents or their post-synthetic modifications in the apoplast compromise cell wall integrity and frequently induce plant compensatory responses as a result of these alterations. Here we report that post-synthetic removal of fucose residues specifically from arabinogalactan proteins in the Arabidopsis plant cell wall induces differential expression of fucosyltransferases and leads to the root and hypocotyl elongation changes. These results demonstrate that the post-synthetic modification of cell wall components presents a valuable approach to investigate the potential signaling pathways induced during plant responses to such modifications that usually occur during plant development and stress responses. PMID:27448235

  3. Gamma-aminobutyric acid depletion affects stomata closure and drought tolerance of Arabidopsis thaliana.

    PubMed

    Mekonnen, Dereje Worku; Flügge, Ulf-Ingo; Ludewig, Frank

    2016-04-01

    A rapid accumulation of γ-aminobutyric acid (GABA) during biotic and abiotic stresses is well documented. However, the specificity of the response and the primary role of GABA under such stress conditions are hardly understood. To address these questions, we investigated the response of the GABA-depleted gad1/2 mutant to drought stress. GABA is primarily synthesized from the decarboxylation of glutamate by glutamate decarboxylase (GAD) which exists in five copies in the genome of Arabidopsis thaliana. However, only GAD1 and GAD2 are abundantly expressed, and knockout of these two copies dramatically reduced the GABA content. Phenotypic analysis revealed a reduced shoot growth of the gad1/2 mutant. Furthermore, the gad1/2 mutant was wilted earlier than the wild type following a prolonged drought stress treatment. The early-wilting phenotype was due to an increase in stomata aperture and a defect in stomata closure. The increase in stomata aperture contributed to higher stomatal conductance. The drought oversensitive phenotype of the gad1/2 mutant was reversed by functional complementation that increases GABA level in leaves. The functionally complemented gad1/2 x pop2 triple mutant contained more GABA than the wild type. Our findings suggest that GABA accumulation during drought is a stress-specific response and its accumulation induces the regulation of stomatal opening thereby prevents loss of water. PMID:26940489

  4. Arabidopsis AtADF1 is functionally affected by mutations on actin binding sites.

    PubMed

    Dong, Chun-Hai; Tang, Wei-Ping; Liu, Jia-Yao

    2013-03-01

    The plant actin depolymerizing factor (ADF) binds to both monomeric and filamentous actin, and is directly involved in the depolymerization of actin filaments. To better understand the actin binding sites of the Arabidopsis thaliana L. AtADF1, we generated mutants of AtADF1 and investigated their functions in vitro and in vivo. Analysis of mutants harboring amino acid substitutions revealed that charged residues (Arg98 and Lys100) located at the α-helix 3 and forming an actin binding site together with the N-terminus are essential for both G- and F-actin binding. The basic residues on the β-strand 5 (K82/A) and the α-helix 4 (R135/A, R137/A) form another actin binding site that is important for F-actin binding. Using transient expression of CFP-tagged AtADF1 mutant proteins in onion (Allium cepa) peel epidermal cells and transgenic Arabidopsis thaliana L. plants overexpressing these mutants, we analyzed how these mutant proteins regulate actin organization and affect seedling growth. Our results show that the ADF mutants with a lower affinity for actin filament binding can still be functional, unless the affinity for actin monomers is also affected. The G-actin binding activity of the ADF plays an essential role in actin binding, depolymerization of actin polymers, and therefore in the control of actin organization. PMID:23190411

  5. Arabidopsis protein arginine methyltransferase 3 is required for ribosome biogenesis by affecting precursor ribosomal RNA processing

    PubMed Central

    Hang, Runlai; Liu, Chunyan; Ahmad, Ayaz; Zhang, Yong; Lu, Falong; Cao, Xiaofeng

    2014-01-01

    Ribosome biogenesis is a fundamental and tightly regulated cellular process, including synthesis, processing, and assembly of rRNAs with ribosomal proteins. Protein arginine methyltransferases (PRMTs) have been implicated in many important biological processes, such as ribosome biogenesis. Two alternative precursor rRNA (pre-rRNA) processing pathways coexist in yeast and mammals; however, how PRMT affects ribosome biogenesis remains largely unknown. Here we show that Arabidopsis PRMT3 (AtPRMT3) is required for ribosome biogenesis by affecting pre-rRNA processing. Disruption of AtPRMT3 results in pleiotropic developmental defects, imbalanced polyribosome profiles, and aberrant pre-rRNA processing. We further identify an alternative pre-rRNA processing pathway in Arabidopsis and demonstrate that AtPRMT3 is required for the balance of these two pathways to promote normal growth and development. Our work uncovers a previously unidentified function of PRMT in posttranscriptional regulation of rRNA, revealing an extra layer of complexity in the regulation of ribosome biogenesis. PMID:25352672

  6. Ectopic expression of TAPETUM DETERMINANT1 affects ovule development in Arabidopsis.

    PubMed

    Huang, Jian; Wijeratne, Asela J; Tang, Chong; Zhang, Tianyu; Fenelon, Rebecca E; Owen, Heather A; Zhao, Dazhong

    2016-03-01

    Plants have evolved to extensively employ leucine-rich repeat receptor-like kinases (LRR-RLKs), the largest family of RLKs, to control growth, development, and defense. In Arabidopsis thaliana, the EXCESS MICROSPOROCYTES1 (EMS1) LRR-RLK and its potential small protein ligand TAPETUM DETERMINANT1 (TPD1) are specifically required for anther cell differentiation; however, TPD1 and EMS1 orthologs also control megaspore mother cell proliferation in rice and maize ovules. Here, the molecular function of TPD1 was demonstrated during ovule development in Arabidopsis using a gain-of-function approach. In ovules, the EMS1 gene was primarily expressed in nucellus epidermis and chalaza, whereas the expression of TPD1 was weakly restricted to the distal end of integuments. Ectopic expression of TPD1 caused pleiotropic defects in ovule and seed development. RNA sequencing analysis showed that ectopic expression of TPD1 altered expression of auxin signaling genes and core cell-cycle genes during ovule development. Moreover, ectopic expression of TPD1 not only affected auxin response but also enhanced expression of cyclin genes CYCD3;3 and CYCA2;3 in ovules. Thus, these results provide insight into the molecular mechanism by which TPD1-EMS1 signaling controls plant development possibly via regulation of auxin signaling and cell-cycle genes. PMID:26685185

  7. Natural Variation in Epigenetic Pathways Affects the Specification of Female Gamete Precursors in Arabidopsis[OPEN

    PubMed Central

    Rodríguez-Leal, Daniel; León-Martínez, Gloria; Abad-Vivero, Ursula; Vielle-Calzada, Jean-Philippe

    2015-01-01

    In angiosperms, the transition to the female gametophytic phase relies on the specification of premeiotic gamete precursors from sporophytic cells in the ovule. In Arabidopsis thaliana, a single diploid cell is specified as the premeiotic female gamete precursor. Here, we show that ecotypes of Arabidopsis exhibit differences in megasporogenesis leading to phenotypes reminiscent of defects in dominant mutations that epigenetically affect the specification of female gamete precursors. Intraspecific hybridization and polyploidy exacerbate these defects, which segregate quantitatively in F2 populations derived from ecotypic hybrids, suggesting that multiple loci control cell specification at the onset of female meiosis. This variation in cell differentiation is influenced by the activity of ARGONAUTE9 (AGO9) and RNA-DEPENDENT RNA POLYMERASE6 (RDR6), two genes involved in epigenetic silencing that control the specification of female gamete precursors. The pattern of transcriptional regulation and localization of AGO9 varies among ecotypes, and abnormal gamete precursors in ovules defective for RDR6 share identity with ectopic gamete precursors found in selected ecotypes. Our results indicate that differences in the epigenetic control of cell specification lead to natural phenotypic variation during megasporogenesis. We propose that this mechanism could be implicated in the emergence and evolution of the reproductive alternatives that prevail in flowering plants. PMID:25829442

  8. Natural variation in epigenetic pathways affects the specification of female gamete precursors in Arabidopsis.

    PubMed

    Rodríguez-Leal, Daniel; León-Martínez, Gloria; Abad-Vivero, Ursula; Vielle-Calzada, Jean-Philippe

    2015-04-01

    In angiosperms, the transition to the female gametophytic phase relies on the specification of premeiotic gamete precursors from sporophytic cells in the ovule. In Arabidopsis thaliana, a single diploid cell is specified as the premeiotic female gamete precursor. Here, we show that ecotypes of Arabidopsis exhibit differences in megasporogenesis leading to phenotypes reminiscent of defects in dominant mutations that epigenetically affect the specification of female gamete precursors. Intraspecific hybridization and polyploidy exacerbate these defects, which segregate quantitatively in F2 populations derived from ecotypic hybrids, suggesting that multiple loci control cell specification at the onset of female meiosis. This variation in cell differentiation is influenced by the activity of ARGONAUTE9 (AGO9) and RNA-DEPENDENT RNA POLYMERASE6 (RDR6), two genes involved in epigenetic silencing that control the specification of female gamete precursors. The pattern of transcriptional regulation and localization of AGO9 varies among ecotypes, and abnormal gamete precursors in ovules defective for RDR6 share identity with ectopic gamete precursors found in selected ecotypes. Our results indicate that differences in the epigenetic control of cell specification lead to natural phenotypic variation during megasporogenesis. We propose that this mechanism could be implicated in the emergence and evolution of the reproductive alternatives that prevail in flowering plants. PMID:25829442

  9. SPL8, an SBP-box gene that affects pollen sac development in Arabidopsis.

    PubMed

    Unte, Ulrike S; Sorensen, Anna-Marie; Pesaresi, Paolo; Gandikota, Madhuri; Leister, Dario; Saedler, Heinz; Huijser, Peter

    2003-04-01

    SQUAMOSA PROMOTER BINDING PROTEIN-box genes (SBP-box genes) encode plant-specific proteins that share a highly conserved DNA binding domain, the SBP domain. Although likely to represent transcription factors, little is known about their role in development. In Arabidopsis, SBP-box genes constitute a structurally heterogeneous family of 16 members known as SPL genes. For one of these genes, SPL8, we isolated three independent transposon-tagged mutants, all of which exhibited a strong reduction in fertility. Microscopic analysis revealed that this reduced fertility is attributable primarily to abnormally developed microsporangia, which exhibit premeiotic abortion of the sporocytes. In addition to its role in microsporogenesis, the SPL8 knockout also seems to affect megasporogenesis, trichome formation on sepals, and stamen filament elongation. The SPL8 mutants described help to uncover the roles of SBP-box genes in plant development. PMID:12671094

  10. SPL8, an SBP-Box Gene That Affects Pollen Sac Development in Arabidopsis

    PubMed Central

    Unte, Ulrike S.; Sorensen, Anna-Marie; Pesaresi, Paolo; Gandikota, Madhuri; Leister, Dario; Saedler, Heinz; Huijser, Peter

    2003-01-01

    SQUAMOSA PROMOTER BINDING PROTEIN–box genes (SBP-box genes) encode plant-specific proteins that share a highly conserved DNA binding domain, the SBP domain. Although likely to represent transcription factors, little is known about their role in development. In Arabidopsis, SBP-box genes constitute a structurally heterogeneous family of 16 members known as SPL genes. For one of these genes, SPL8, we isolated three independent transposon-tagged mutants, all of which exhibited a strong reduction in fertility. Microscopic analysis revealed that this reduced fertility is attributable primarily to abnormally developed microsporangia, which exhibit premeiotic abortion of the sporocytes. In addition to its role in microsporogenesis, the SPL8 knockout also seems to affect megasporogenesis, trichome formation on sepals, and stamen filament elongation. The SPL8 mutants described help to uncover the roles of SBP-box genes in plant development. PMID:12671094

  11. cis-Jasmone induces Arabidopsis genes that affect the chemical ecology of multitrophic interactions with aphids and their parasitoids

    PubMed Central

    Bruce, Toby J. A.; Matthes, Michaela C.; Chamberlain, Keith; Woodcock, Christine M.; Mohib, Abdul; Webster, Ben; Smart, Lesley E.; Birkett, Michael A.; Pickett, John A.; Napier, Johnathan A.

    2008-01-01

    It is of adaptive value for a plant to prepare its defenses when a threat is detected, and certain plant volatiles associated with insect damage, such as cis-jasmone (CJ), are known to switch-on defense metabolism. We used aphid and aphid parasitoid responses to Arabidopsis thaliana as a model system for studying gene expression and defense chemistry and its impact at different trophic levels. Differential responses to volatiles of induced Arabidopsis occurred for specialist and generalist insects: the generalist aphid, Myzus persicae, was repelled, whereas the specialist, Lipaphis erysimi, was attracted; the generalist aphid parasitoid Aphidius ervi was attracted, but the specialist parasitoid Diaeretiella rapae was not affected. A. ervi also spent longer foraging on induced plants than on untreated ones. Transcriptomic analyses of CJ-induced Arabidopsis plants revealed that a limited number of genes, including a gene for a cytochrome P450, CYP81D11, were strongly up-regulated in the treated plants. We examined transgenic Arabidopsis lines constitutively overexpressing this gene in bioassays and found insect responses similar to those obtained for wild-type plants induced with CJ, indicating the importance of this gene in the CJ-activated defense response. Genes involved in glucosinolate biosynthesis and catabolism are unaffected by CJ and, because these genes relate to interactions with herbivores and parasitoids specific to this family of plants (Brassicaceae), this finding may explain the differences in behavioral response of specialist and generalist insects. PMID:18356298

  12. CIPK23 is involved in iron acquisition of Arabidopsis by affecting ferric chelate reductase activity.

    PubMed

    Tian, Qiuying; Zhang, Xinxin; Yang, An; Wang, Tianzuo; Zhang, Wen-Hao

    2016-05-01

    Iron deficiency is one of the major limiting factors affecting quality and production of crops in calcareous soils. Numerous signaling molecules and transcription factors have been demonstrated to play a regulatory role in adaptation of plants to iron deficiency. However, the mechanisms underlying the iron deficiency-induced physiological processes remain to be fully dissected. Here, we demonstrated that the protein kinase CIPK23 was involved in iron acquisition. Lesion of CIPK23 rendered Arabidopsis mutants hypersensitive to iron deficiency, as evidenced by stronger chlorosis in young leaves and lower iron concentration than wild-type plants under iron-deficient conditions by down-regulating ferric chelate reductase activity. We found that iron deficiency evoked an increase in cytosolic Ca(2+) concentration and the elevated Ca(2+) would bind to CBL1/CBL9, leading to activation of CIPK23. These novel findings highlight the involvement of calcium-dependent CBL-CIPK23 complexes in the regulation of iron acquisition. Moreover, mutation of CIPK23 led to changes in contents of mineral elements, suggesting that CBL-CIPK23 complexes could be as "nutritional sensors" to sense and regulate the mineral homeostasis in Arabisopsis. PMID:26993237

  13. Common gas phase molecules from fungi affect seed germination and plant health in Arabidopsis thaliana

    PubMed Central

    2014-01-01

    Fungal volatile organic compounds (VOCs) play important ecophysiological roles in mediating inter-kingdom signaling with arthropods but less is known about their interactions with plants. In this study, Arabidopsis thaliana was used as a model in order to test the physiological effects of 23 common vapor-phase fungal VOCs that included alcohols, aldehydes, ketones, and other chemical classes. After exposure to a shared atmosphere with the 23 individual VOCs for 72 hrs, seeds were assayed for rate of germination and seedling formation; vegetative plants were assayed for fresh weight and chlorophyll concentration. All but five of the VOCs tested (1-decene, 2-n-heptylfuran, nonanal, geosmin and -limonene) had a significant effect in inhibiting either germination, seedling formation or both. Seedling formation was entirely inhibited by exposure to 1-octen-3-one, 2-ethylhexanal, 3-methylbutanal, and butanal. As assayed by a combination of fresh weight and chlorophyll concentration, 2-ethylhexanal had a negative impact on two-week-old vegetative plants. Three other compounds (1-octen-3-ol, 2-ethylhexanal, and 2-heptylfuran) decreased fresh weight alone. Most of the VOCs tested did not change the fresh weight or chlorophyll concentration of vegetative plants. In summary, when tested as single compounds, fungal VOCs affected A. thaliana in positive, negative or neutral ways. PMID:25045602

  14. Higher endogenous methionine in transgenic Arabidopsis seeds affects the composition of storage proteins and lipids.

    PubMed

    Cohen, Hagai; Pajak, Agnieszka; Pandurangan, Sudhakar; Amir, Rachel; Marsolais, Frédéric

    2016-06-01

    Previous in vitro studies demonstrate that exogenous application of the sulfur-containing amino acid methionine into cultured soybean cotyledons and seedlings reduces the level of methionine-poor storage proteins and elevates those that are methionine-rich. However, the effect of higher endogenous methionine in seeds on the composition of storage products in vivo is not studied yet. We have recently produced transgenic Arabidopsis seeds having significantly higher levels of methionine. In the present work we used these seeds as a model system and profiled them for changes in the abundances of 12S-globulins and 2S-albumins, the two major groups of storage proteins, using 2D-gels and MALDI-MS detection. The findings suggest that higher methionine affects from a certain threshold the accumulation of several subunits of 12S-globulins and 2S-albumins, regardless of their methionine contents, resulting in higher total protein contents. The mRNA abundances of most of the genes encoding these proteins were either correlated or not correlated with the abundances of these proteins, implying that methionine may regulate storage proteins at both transcriptional and post-transcriptional levels. The elevations in total protein contents resulted in reduction of total lipids and altered the fatty acid composition. Altogether, the data provide new insights into the regulatory roles of elevated methionine levels on seed composition. PMID:26888094

  15. Flavonoid accumulation in Arabidopsis repressed in lignin synthesis affects auxin transport and plant growth.

    PubMed

    Besseau, Sébastien; Hoffmann, Laurent; Geoffroy, Pierrette; Lapierre, Catherine; Pollet, Brigitte; Legrand, Michel

    2007-01-01

    In Arabidopsis thaliana, silencing of hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyl transferase (HCT), a lignin biosynthetic gene, results in a strong reduction of plant growth. We show that, in HCT-silenced plants, lignin synthesis repression leads to the redirection of the metabolic flux into flavonoids through chalcone synthase activity. Several flavonol glycosides and acylated anthocyanin were shown to accumulate in higher amounts in silenced plants. By contrast, sinapoylmalate levels were barely affected, suggesting that the synthesis of that phenylpropanoid compound might be HCT-independent. The growth phenotype of HCT-silenced plants was shown to be controlled by light and to depend on chalcone synthase expression. Histochemical analysis of silenced stem tissues demonstrated altered tracheary elements. The level of plant growth reduction of HCT-deficient plants was correlated with the inhibition of auxin transport. Suppression of flavonoid accumulation by chalcone synthase repression in HCT-deficient plants restored normal auxin transport and wild-type plant growth. By contrast, the lignin structure of the plants simultaneously repressed for HCT and chalcone synthase remained as severely altered as in HCT-silenced plants, with a large predominance of nonmethoxylated H units. These data demonstrate that the reduced size phenotype of HCT-silenced plants is not due to the alteration of lignin synthesis but to flavonoid accumulation. PMID:17237352

  16. Arabidopsis FH1 Formin Affects Cotyledon Pavement Cell Shape by Modulating Cytoskeleton Dynamics.

    PubMed

    Rosero, Amparo; Oulehlová, Denisa; Stillerová, Lenka; Schiebertová, Petra; Grunt, Michal; Žárský, Viktor; Cvrčková, Fatima

    2016-03-01

    Plant cell morphogenesis involves concerted rearrangements of microtubules and actin microfilaments. We previously reported that FH1, the main Arabidopsis thaliana housekeeping Class I membrane-anchored formin, contributes to actin dynamics and microtubule stability in rhizodermis cells. Here we examine the effects of mutations affecting FH1 (At3g25500) on cell morphogenesis and above-ground organ development in seedlings, as well as on cytoskeletal organization and dynamics, using a combination of confocal and variable angle epifluorescence microscopy with a pharmacological approach. Homozygous fh1 mutants exhibited cotyledon epinasty and had larger cotyledon pavement cells with more pronounced lobes than the wild type. The pavement cell shape alterations were enhanced by expression of the fluorescent microtubule marker GFP-microtubule-associated protein 4 (MAP4). Mutant cotyledon pavement cells exhibited reduced density and increased stability of microfilament bundles, as well as enhanced dynamics of microtubules. Analogous results were also obtained upon treatments with the formin inhibitor SMIFH2 (small molecule inhibitor of formin homology 2 domains). Pavement cell shape in wild-type (wt) and fh1 plants in some situations exhibited a differential response towards anti-cytoskeletal drugs, especially the microtubule disruptor oryzalin. Our observations indicate that FH1 participates in the control of microtubule dynamics, possibly via its effects on actin, subsequently influencing cell morphogenesis and macroscopic organ development. PMID:26738547

  17. Genes of the most conserved WOX clade in plants affect root and flower development in Arabidopsis

    PubMed Central

    2008-01-01

    Background The Wuschel related homeobox (WOX) family proteins are key regulators implicated in the determination of cell fate in plants by preventing cell differentiation. A recent WOX phylogeny, based on WOX homeodomains, showed that all of the Physcomitrella patens and Selaginella moellendorffii WOX proteins clustered into a single orthologous group. We hypothesized that members of this group might preferentially share a significant part of their function in phylogenetically distant organisms. Hence, we first validated the limits of the WOX13 orthologous group (WOX13 OG) using the occurrence of other clade specific signatures and conserved intron insertion sites. Secondly, a functional analysis using expression data and mutants was undertaken. Results The WOX13 OG contained the most conserved plant WOX proteins including the only WOX detected in the highly proliferating basal unicellular and photosynthetic organism Ostreococcus tauri. A large expansion of the WOX family was observed after the separation of mosses from other land plants and before monocots and dicots have arisen. In Arabidopsis thaliana, AtWOX13 was dynamically expressed during primary and lateral root initiation and development, in gynoecium and during embryo development. AtWOX13 appeared to affect the floral transition. An intriguing clade, represented by the functional AtWOX14 gene inside the WOX13 OG, was only found in the Brassicaceae. Compared to AtWOX13, the gene expression profile of AtWOX14 was restricted to the early stages of lateral root formation and specific to developing anthers. A mutational insertion upstream of the AtWOX14 homeodomain sequence led to abnormal root development, a delay in the floral transition and premature anther differentiation. Conclusion Our data provide evidence in favor of the WOX13 OG as the clade containing the most conserved WOX genes and established a functional link to organ initiation and development in Arabidopsis, most likely by preventing premature

  18. Action spectrum of photoinhibition in leaves of wild type and npq1-2 and npq4-1 mutants of Arabidopsis thaliana.

    PubMed

    Sarvikas, Päivi; Hakala, Marja; Pätsikkä, Eija; Tyystjärvi, Taina; Tyystjärvi, Esa

    2006-03-01

    Photoinhibition is light-induced inactivation of PSII. Hypotheses about the photoreceptor(s) of photoinhibition include the Chl antenna of PSII, manganese of the oxygen-evolving complex (OEC), uncoupled Chl and iron-sulfur centres. We measured the action spectrum of photoinhibition in vivo from wild-type Arabidopsis thaliana L. and from the npq1-2 and npq4-1 mutants defective in non-photochemical quenching (NPQ) of excitations of the PSII antenna. The in vivo action spectrum was found to resemble closely the in vitro action spectra published for photoinhibition. We compared the action spectrum with absorbance spectra of model compounds of the OEC complex and other potential photoreceptors of photoinhibition. The comparison suggests that both manganese and Chl function as photoreceptors in photoinhibition. In accordance with the function of two types of photoreceptors in photoinhibition, NPQ was found to offer only partial protection against photoinhibition at visible wavelengths. The low protective efficiency of NPQ supports the conclusion that the Chl antenna of PSII is not the only photoreceptor of photoinhibition. Comparison of the action spectrum of photoinhibition with the emission spectrum of sunlight shows that the UV part of sunlight is responsible for the major part of photoinhibition under natural conditions. PMID:16415063

  19. Leaf biomechanical properties in Arabidopsis thaliana polysaccharide mutants affect drought survival.

    PubMed

    Balsamo, Ronald; Boak, Merewyn; Nagle, Kayla; Peethambaran, Bela; Layton, Bradley

    2015-11-26

    Individual sugars are the building blocks of cell wall polysaccharides, which in turn comprise a plant׳s overall architectural structure. But which sugars play the most prominent role in maintaining a plant׳s mechanical stability during large cellular deformations induced by drought? We investigated the individual contributions of several genes that are involved in the synthesis of monosaccharides which are important for cell wall structure. We then measured drought tolerance and mechanical integrity during simulated drought in Arabidopsis thaliana. To assess mechanical properties, we designed a small-scale tensile tester for measuring failure strain, ultimate tensile stress, work to failure, toughness, and elastic modulus of 6-week-old leaves in both hydrated and drought-simulated states. Col-0 mutants used in this study include those deficient in lignin, cellulose, components of hemicellulose such as xylose and fucose, the pectic components arabinose and rhamnose, as well as mutants with enhanced arabinose and total pectin content. We found that drought tolerance is correlated to the mechanical and architectural stability of leaves as they experience dehydration. Of the mutants, S096418 with mutations for reduced xylose and galactose was the least drought tolerant, while the arabinose-altered CS8578 mutants were the least affected by water loss. There were also notable correlations between drought tolerance and mechanical properties in the diminished rhamnose mutant, CS8575 and the dehydrogenase-disrupted S120106. Our findings suggest that components of hemicellulose and pectins affect leaf biomechanical properties and may play an important role in the ability of this model system to survive drought. PMID:26520913

  20. Cytonuclear interactions affect adaptive traits of the annual plant Arabidopsis thaliana in the field.

    PubMed

    Roux, Fabrice; Mary-Huard, Tristan; Barillot, Elise; Wenes, Estelle; Botran, Lucy; Durand, Stéphanie; Villoutreix, Romain; Martin-Magniette, Marie-Laure; Camilleri, Christine; Budar, Françoise

    2016-03-29

    Although the contribution of cytonuclear interactions to plant fitness variation is relatively well documented at the interspecific level, the prevalence of cytonuclear interactions at the intraspecific level remains poorly investigated. In this study, we set up a field experiment to explore the range of effects that cytonuclear interactions have on fitness-related traits inArabidopsis thaliana To do so, we created a unique series of 56 cytolines resulting from cytoplasmic substitutions among eight natural accessions reflecting within-species genetic diversity. An assessment of these cytolines and their parental lines scored for 28 adaptive whole-organism phenotypes showed that a large proportion of phenotypic traits (23 of 28) were affected by cytonuclear interactions. The effects of these interactions varied from slight but frequent across cytolines to strong in some specific parental pairs. Two parental pairs accounted for half of the significant pairwise interactions. In one parental pair, Ct-1/Sha, we observed symmetrical phenotypic responses between the two nuclear backgrounds when combined with specific cytoplasms, suggesting nuclear differentiation at loci involved in cytonuclear epistasis. In contrast, asymmetrical phenotypic responses were observed in another parental pair, Cvi-0/Sha. In the Cvi-0 nuclear background, fecundity and phenology-related traits were strongly affected by the Sha cytoplasm, leading to a modified reproductive strategy without penalizing total seed production. These results indicate that natural variation in cytoplasmic and nuclear genomes interact to shape integrative traits that contribute to adaptation, thereby suggesting that cytonuclear interactions can play a major role in the evolutionary dynamics ofA. thaliana. PMID:26979961

  1. Cytonuclear interactions affect adaptive traits of the annual plant Arabidopsis thaliana in the field

    PubMed Central

    Roux, Fabrice; Mary-Huard, Tristan; Barillot, Elise; Wenes, Estelle; Botran, Lucy; Durand, Stéphanie; Villoutreix, Romain; Martin-Magniette, Marie-Laure; Camilleri, Christine; Budar, Françoise

    2016-01-01

    Although the contribution of cytonuclear interactions to plant fitness variation is relatively well documented at the interspecific level, the prevalence of cytonuclear interactions at the intraspecific level remains poorly investigated. In this study, we set up a field experiment to explore the range of effects that cytonuclear interactions have on fitness-related traits in Arabidopsis thaliana. To do so, we created a unique series of 56 cytolines resulting from cytoplasmic substitutions among eight natural accessions reflecting within-species genetic diversity. An assessment of these cytolines and their parental lines scored for 28 adaptive whole-organism phenotypes showed that a large proportion of phenotypic traits (23 of 28) were affected by cytonuclear interactions. The effects of these interactions varied from slight but frequent across cytolines to strong in some specific parental pairs. Two parental pairs accounted for half of the significant pairwise interactions. In one parental pair, Ct-1/Sha, we observed symmetrical phenotypic responses between the two nuclear backgrounds when combined with specific cytoplasms, suggesting nuclear differentiation at loci involved in cytonuclear epistasis. In contrast, asymmetrical phenotypic responses were observed in another parental pair, Cvi-0/Sha. In the Cvi-0 nuclear background, fecundity and phenology-related traits were strongly affected by the Sha cytoplasm, leading to a modified reproductive strategy without penalizing total seed production. These results indicate that natural variation in cytoplasmic and nuclear genomes interact to shape integrative traits that contribute to adaptation, thereby suggesting that cytonuclear interactions can play a major role in the evolutionary dynamics of A. thaliana. PMID:26979961

  2. Preschool-Aged Children with Iron Deficiency Anemia Show Altered Affect and Behavior1,2

    PubMed Central

    Lozoff, Betsy; Corapci, Feyza; Burden, Matthew J.; Kaciroti, Niko; Angulo-Barroso, Rosa; Sazawal, Sunil; Black, Maureen

    2012-01-01

    This study compared social looking and response to novelty in preschool-aged children (47–68 mo) with or without iron deficiency anemia (IDA). Iron status of the participants from a low-income community in New Delhi, India, was based on venous hemoglobin, mean corpuscular volume, and red cell distribution width. Children’s social looking toward adults, affect, and wary or hesitant behavior in response to novelty were assessed in a semistructured paradigm during an in-home play observation. Affect and behavior were compared as a function of iron status: IDA (n = 74) vs. nonanemic (n = 164). Compared with nonanemic preschoolers, preschoolers with IDA displayed less social looking toward their mothers, moved close to their mothers more quickly, and were slower to display positive affect and touch novel toys for the first time. These results indicate that IDA in the preschool period has affective and behavioral effects similar to those reported for IDA in infancy. PMID:17311960

  3. Increasing Phosphatidylinositol (4,5)-Bisphosphate Biosynthesis Affects Basal Signaling and Chloroplast Metabolism in Arabidopsis thaliana

    PubMed Central

    Im, Yang Ju; Smith, Caroline M.; Phillippy, Brian Q.; Strand, Deserah; Kramer, David M.; Grunden, Amy M.; Boss, Wendy F.

    2014-01-01

    One challenge in studying the second messenger inositol(1,4,5)-trisphosphate (InsP3) is that it is present in very low amounts and increases only transiently in response to stimuli. To identify events downstream of InsP3, we generated transgenic plants constitutively expressing the high specific activity, human phosphatidylinositol 4-phosphate 5-kinase Iα (HsPIPKIα). PIP5K is the enzyme that synthesizes phosphatidylinositol (4,5)-bisphosphate (PtdIns(4,5)P2); this reaction is flux limiting in InsP3 biosynthesis in plants. Plasma membranes from transgenic Arabidopsis expressing HsPIPKIα had 2–3 fold higher PIP5K specific activity, and basal InsP3 levels in seedlings and leaves were >2-fold higher than wild type. Although there was no significant difference in photosynthetic electron transport, HsPIPKIα plants had significantly higher starch (2–4 fold) and 20% higher anthocyanin compared to controls. Starch content was higher both during the day and at the end of dark period. In addition, transcripts of genes involved in starch metabolism such as SEX1 (glucan water dikinase) and SEX4 (phosphoglucan phosphatase), DBE (debranching enzyme), MEX1 (maltose transporter), APL3 (ADP-glucose pyrophosphorylase) and glucose-6-phosphate transporter (Glc6PT) were up-regulated in the HsPIPKIα plants. Our results reveal that increasing the phosphoinositide (PI) pathway affects chloroplast carbon metabolism and suggest that InsP3 is one component of an inter-organelle signaling network regulating chloroplast metabolism. PMID:27135490

  4. Arabidopsis flower specific defense gene expression patterns affect resistance to pathogens.

    PubMed

    Ederli, Luisa; Dawe, Adam; Pasqualini, Stefania; Quaglia, Mara; Xiong, Liming; Gehring, Chris

    2015-01-01

    We investigated whether the Arabidopsis flower evolved protective measures to increase reproductive success. Firstly, analyses of available transcriptome data show that the most highly expressed transcripts in the closed sepal (stage 12) are enriched in genes with roles in responses to chemical stimuli and cellular metabolic processes. At stage 15, there is enrichment in transcripts with a role in responses to biotic stimuli. Comparative analyses between the sepal and petal in the open flower mark an over-representation of transcripts with a role in responses to stress and catalytic activity. Secondly, the content of the biotic defense-associated phytohormone salicylic acid (SA) in sepals and petals is significantly higher than in leaves. To understand whether the high levels of stress responsive transcripts and the higher SA content affect defense, wild-type plants (Col-0) and transgenic plants defective in SA accumulation (nahG) were challenged with the biotrophic fungus Golovinomyces cichoracearum, the causal agent of powdery mildew, and the necrotrophic fungus Botrytis cinerea. NahG leaves were more sensitive than those of Col-0, suggesting that in leaves SA has a role in the defense against biotrophs. In contrast, sepals and petals of both genotypes were resistant to G. cichoracearum, indicating that in the flower, resistance to the biotrophic pathogen is not critically dependent on SA, but likely dependent on the up-regulation of stress-responsive genes. Since sepals and petals of both genotypes are equally susceptible to B. cinerea, we conclude that neither stress-response genes nor increased SA accumulation offers protection against the necrotrophic pathogen. These results are interpreted in the light of the distinctive role of the flower and we propose that in the early stages, the sepal may act as a chemical defense barrier of the developing reproductive structures against biotrophic pathogens. PMID:25750645

  5. Arabidopsis flower specific defense gene expression patterns affect resistance to pathogens

    PubMed Central

    Ederli, Luisa; Dawe, Adam; Pasqualini, Stefania; Quaglia, Mara; Xiong, Liming; Gehring, Chris

    2015-01-01

    We investigated whether the Arabidopsis flower evolved protective measures to increase reproductive success. Firstly, analyses of available transcriptome data show that the most highly expressed transcripts in the closed sepal (stage 12) are enriched in genes with roles in responses to chemical stimuli and cellular metabolic processes. At stage 15, there is enrichment in transcripts with a role in responses to biotic stimuli. Comparative analyses between the sepal and petal in the open flower mark an over-representation of transcripts with a role in responses to stress and catalytic activity. Secondly, the content of the biotic defense-associated phytohormone salicylic acid (SA) in sepals and petals is significantly higher than in leaves. To understand whether the high levels of stress responsive transcripts and the higher SA content affect defense, wild-type plants (Col-0) and transgenic plants defective in SA accumulation (nahG) were challenged with the biotrophic fungus Golovinomyces cichoracearum, the causal agent of powdery mildew, and the necrotrophic fungus Botrytis cinerea. NahG leaves were more sensitive than those of Col-0, suggesting that in leaves SA has a role in the defense against biotrophs. In contrast, sepals and petals of both genotypes were resistant to G. cichoracearum, indicating that in the flower, resistance to the biotrophic pathogen is not critically dependent on SA, but likely dependent on the up-regulation of stress-responsive genes. Since sepals and petals of both genotypes are equally susceptible to B. cinerea, we conclude that neither stress-response genes nor increased SA accumulation offers protection against the necrotrophic pathogen. These results are interpreted in the light of the distinctive role of the flower and we propose that in the early stages, the sepal may act as a chemical defense barrier of the developing reproductive structures against biotrophic pathogens. PMID:25750645

  6. A flowering integrator, SOC1, affects stomatal opening in Arabidopsis thaliana.

    PubMed

    Kimura, Yuriko; Aoki, Saya; Ando, Eigo; Kitatsuji, Ayaka; Watanabe, Aiko; Ohnishi, Masato; Takahashi, Koji; Inoue, Shin-ichiro; Nakamichi, Norihito; Tamada, Yosuke; Kinoshita, Toshinori

    2015-04-01

    Stomatal movements are regulated by multiple environmental signals. Recent investigations indicate that photoperiodic flowering components, such as CRY, GI, CO, FT and TSF, are expressed in guard cells and positively affect stomatal opening in Arabidopsis thaliana. Here we show that SOC1, which encodes a MADS box transcription factor and integrates multiple flowering signals, also exerts a positive effect on stomatal opening. FLC encodes a potent repressor of FT and SOC1, and FRI acts as an activator of FLC. Thus, we examined stomatal phenotypes in FRI-Col, which contains an active FRI allele of accession Sf-2 by introgression. We found higher expression of FLC and lower expression of FT, SOC1 and TSF in guard cells from FRI-Col than in those from Col. Light-induced stomatal opening was significantly suppressed in FRI-Col. Interestingly, vernalization of FRI-Col partially restored light-induced stomatal opening, concomitant with a decrease of FLC and increase of FT, SOC1 and TSF. Furthermore, we observed the constitutive open-stomata phenotype in transgenic plants overexpressing SOC1-GFP (green fluorescent protein) in guard cells (SOC1-GFP overexpressor), and found that light-induced stomatal opening was significantly suppressed in a soc1 knockout mutant. RNA sequencing using epidermis from the SOC1-GFP overexpressor revealed that the expression levels of several genes involved in stomatal opening, such as BLUS1 and the plasma membrane H(+)-ATPases, were higher than those in background plants. From these results, we conclude that SOC1 is involved in the regulation of stomatal opening via transcriptional regulation in guard cells. PMID:25588388

  7. Constitutive Expression of OsIAA9 Affects Starch Granules Accumulation and Root Gravitropic Response in Arabidopsis

    PubMed Central

    Luo, Sha; Li, Qianqian; Liu, Shanda; Pinas, Nicholaas M.; Tian, Hainan; Wang, Shucai

    2015-01-01

    Auxin/Indole-3-Acetic Acid (Aux/IAA) genes are early auxin response genes ecoding short-lived transcriptional repressors, which regulate auxin signaling in plants by interplay with Auxin Response Factors (ARFs). Most of the Aux/IAA proteins contain four different domains, namely Domain I, Domain II, Domain III, and Domain IV. So far all Aux/IAA mutants with auxin-related phenotypes identified in both Arabidopsis and rice (Oryza sativa) are dominant gain-of-function mutants with mutations in Domain II of the corresponding Aux/IAA proteins, suggest that Aux/IAA proteins in both Arabidopsis and rice are largely functional redundantly, and they may have conserved functions. We report here the functional characterization of a rice Aux/IAA gene, OsIAA9. RT-PCR results showed that expression of OsIAA9 was induced by exogenously applied auxin, suggesting that OsIAA9 is an auxin response gene. Bioinformatic analysis showed that OsIAA9 has a repressor motif in Domain I, a degron in Domain II, and the conserved amino acid signatures for protein-protein interactions in Domain III and Domain IV. By generating transgenic plants expressing GFP-OsIAA9 and examining florescence in the transgenic plants, we found that OsIAA9 is localized in the nucleus. When transfected into protoplasts isolated from rosette leaves of Arabidopsis, OsIAA9 repressed reporter gene expression, and the repression was partially released by exogenously IAA. These results suggest that OsIAA9 is a canonical Aux/IAA protein. Protoplast transfection assays showed that OsIAA9 interacted ARF5, but not ARF6, 7, 8 and 19. Transgenic Arabidopsis plants expressing OsIAA9 have increased number of lateral roots, and reduced gravitropic response. Further analysis showed that OsIAA9 transgenic Arabidopsis plants accumulated fewer granules in their root tips and the distribution of granules was also affected. Taken together, our study showed that OsIAA9 is a transcriptional repressor, and it regulates gravitropic

  8. An eukaryotic translation initiation factor, AteIF5A-2, affects cadmium accumulation and sensitivity in Arabidopsis.

    PubMed

    Xu, Xiao-Yan; Ding, Zhong-Jie; Chen, Lei; Yan, Jin-Ying; Li, Gui-Xin; Zheng, Shao-Jian

    2015-10-01

    Cadmium (Cd) is one of the most toxic elements and can be accumulated in plants easily; meanwhile, eIF5A is a highly conserved protein in all eukaryotic organisms. The present work tried to investigate whether eIF5A is involved in Cd accumulation and sensitivity in Arabidopsis (Arabidopsis thaliana L.) by comparing the wild-type Columbia-0 (Col-0) with a knockdown mutant of AteIF5A-2, fbr12-3 under Cd stress conditions. The results showed that the mutant fbr12-3 accumulated more Cd in roots and shoots and had significantly lower chlorophyll content, shorter root length, and smaller biomass, suggesting that downregulation of AteIF5A-2 makes the mutant more Cd sensitive. Real-time polymerase chain reaction revealed that the expressions of metal transporters involved in Cd uptake and translocation including IRT1, ZIP1, AtNramp3, and AtHMA4 were significantly increased but the expressions of PCS1 and PCS2 related to Cd detoxification were decreased notably in fbr12-3 compared with Col-0. As a result, an increase in MDA and H2 O2 content but decrease in root trolox, glutathione and proline content under Cd stress was observed, indicating that a severer oxidative stress occurs in the mutant. All these results demonstrated for the first time that AteIF5A influences Cd sensitivity by affecting Cd uptake, accumulation, and detoxification in Arabidopsis. PMID:25559189

  9. Cryopreservation affects ROS-induced oxidative stress and antioxidant response in Arabidopsis seedlings

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plant recovery status after cryopreservation by vitrification had a negative relationship to the oxidative stress induced by reactive oxygen species (ROS). Arabidopsis thaliana seedlings germinated for 48-h or 72-h with different cryopreservation survival tolerances were examined at five steps of a ...

  10. Arabidopsis Nucleolin Affects Plant Development and Patterning1[W][OA

    PubMed Central

    Petricka, Jalean Joyanne; Nelson, Timothy Mark

    2007-01-01

    Nucleolin is a major nucleolar protein implicated in many aspects of ribosomal biogenesis, including early events such as processing of the large 35S preribosomal RNA. We found that the Arabidopsis (Arabidopsis thaliana) parallel1 (parl1) mutant, originally identified by its aberrant leaf venation, corresponds to the Arabidopsis nucleolin gene. parl1 mutants display parallel leaf venation, aberrant localization of the provascular marker Athb8:β-glucuronidase, the auxin-sensitive reporter DR5:β-glucuronidase, and auxin-dependent growth defects. PARL1 is highly similar to the yeast (Saccharomyces cerevisiae) nucleolin NUCLEAR SIGNAL RECOGNITION 1 (NSR1) multifunctional protein; the Arabidopsis PARL1 gene can rescue growth defects of yeast nsr1 null mutants. This suggests that PARL1 protein may have roles similar to those of the yeast nucleolin in nuclear signal recognition, ribosomal processing, and ribosomal subunit accumulation. Based on the range of auxin-related defects in parl1 mutants, we propose that auxin-dependent organ growth and patterning is highly sensitive to the efficiency of nucleolin-dependent ribosomal processing. PMID:17369435

  11. Overlapping and antagonistic activities of basic Pentacysteine genes affect a range of developmental processes in Arabidopsis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Technical Abstract: The BASIC PENTACYSTEINE (BPC) proteins are a plant-specific transcription factor family that is present throughout land plants. The Arabidopsis BPC proteins have been categorized into three classes based on sequence similarity, and we demonstrate that there is functional overlap...

  12. Glycerol Affects Root Development through Regulation of Multiple Pathways in Arabidopsis

    PubMed Central

    Hu, Jun; Zhang, Yonghong; Wang, Jinfang; Zhou, Yongming

    2014-01-01

    Glycerol metabolism has been well studied biochemically. However, the means by which glycerol functions in plant development is not well understood. This study aimed to investigate the mechanism underlying the effects of glycerol on root development in Arabidopsis thaliana. Exogenous glycerol inhibited primary root growth and altered lateral root development in wild-type plants. These phenotypes appeared concurrently with increased endogenous glycerol-3-phosphate (G3P) and H2O2 contents in seedlings, and decreased phosphate levels in roots. Upon glycerol treatment, G3P level and root development did not change in glycerol kinase mutant gli1, but G3P level increased in gpdhc1 and fad-gpdh mutants, which resulted in more severely impaired root development. Overexpression of the FAD-GPDH gene attenuated the alterations in G3P, phosphate and H2O2 levels, leading to increased tolerance to exogenous glycerol, which suggested that FAD-GPDH plays an important role in modulating this response. Free indole-3-acetic acid (IAA) content increased by 46%, and DR5pro::GUS staining increased in the stele cells of the root meristem under glycerol treatment, suggesting that glycerol likely alters normal auxin distribution. Decreases in PIN1 and PIN7 expression, β-glucuronidase (GUS) staining in plants expressing PIN7pro::GUS and green fluorescent protein (GFP) fluorescence in plants expressing PIN7pro::PIN7-GFP were observed, indicating that polar auxin transport in the root was downregulated under glycerol treatment. Analyses with auxin-related mutants showed that TIR1 and ARF7 were involved in regulating root growth under glycerol treatment. Glycerol-treated plants showed significant reductions in root meristem size and cell number as revealed by CYCB1;1pro::GUS staining. Furthermore, the expression of CDKA and CYCB1 decreased significantly in treated plants compared with control plants, implying possible alterations in cell cycle progression. Our data demonstrated that glycerol

  13. Changes in gravity affect gene expression, protein modulation and metabolite pools of arabidopsis

    NASA Astrophysics Data System (ADS)

    Hampp, R.; Martzivanou, M.; Maier, R. M.; Magel, E.

    Callus cultures of Arabidopsis thaliana (cv. Columbia) in Petri dishes / suspension cultures were exposed to altered g-forces by centrifugation (1 to 10 g), klinorotation, and μ g (sounding rocket flights). Using semi-quantitative RT-PCR, transcripts of genes coding for metabolic key enzymes (ADP-glucose pyrophosphorylase, ADPG-PP; ß-amylase, fructose-1,6-bisphosphatase, FBPase; glyceraldehyde-P dehydrogenase, GAPDH; hydroxymethylglutaryl-CoA reductase, HMG; phenylalanine-ammonium-lyase, PAL; PEP carboxylase, PEPC) were used to monitor threshold conditions for g-number (all) and time of exposure (ß-amylase) which led to altered amounts of the gene product. Exposure to approx. 5 g and higher for 1h resulted in altered transcript levels: transcripts of ß-amylase, PAL, and PEPC were increased, those of ADPG-PP decreased, while those of FBPase, GAPDH, and HMG were not affected. This probably indicates a shift from starch synthesis to starch degradation and increased rates of anaplerosis (PEPC: supply of ketoacids for amino acid synthesis). In order to get more information about g-related effects on gene expression, we used a 1h-exposure to 7 g for a microarray analysis. Transcripts of more than 200 genes were significantly increased in amount (ratio 7g / 1g control; 21.6 and larger). They fall into several categories. Transcripts coding for enzymes of major pathways form the largest group (25%), followed by gene products involved in cellular organisation and cell wall formation / rearrangement (17%), signalling, phosphorylation/dephosphorylation (12%), proteolysis and transport (10% each), hormone synthesis plus related events (8%), defense (4%), stress-response (2%), and gravisensing (2%). Many of the alterations are part of a general stress response, but some changes related to the synthesis / rearrangement of cell wall components could be more hyper-g-specific. Using macroarrays with selected genes according to our hypergravity study (metabolism / signalling

  14. Glycerol affects root development through regulation of multiple pathways in Arabidopsis.

    PubMed

    Hu, Jun; Zhang, Yonghong; Wang, Jinfang; Zhou, Yongming

    2014-01-01

    Glycerol metabolism has been well studied biochemically. However, the means by which glycerol functions in plant development is not well understood. This study aimed to investigate the mechanism underlying the effects of glycerol on root development in Arabidopsis thaliana. Exogenous glycerol inhibited primary root growth and altered lateral root development in wild-type plants. These phenotypes appeared concurrently with increased endogenous glycerol-3-phosphate (G3P) and H2O2 contents in seedlings, and decreased phosphate levels in roots. Upon glycerol treatment, G3P level and root development did not change in glycerol kinase mutant gli1, but G3P level increased in gpdhc1 and fad-gpdh mutants, which resulted in more severely impaired root development. Overexpression of the FAD-GPDH gene attenuated the alterations in G3P, phosphate and H2O2 levels, leading to increased tolerance to exogenous glycerol, which suggested that FAD-GPDH plays an important role in modulating this response. Free indole-3-acetic acid (IAA) content increased by 46%, and DR5pro::GUS staining increased in the stele cells of the root meristem under glycerol treatment, suggesting that glycerol likely alters normal auxin distribution. Decreases in PIN1 and PIN7 expression, β-glucuronidase (GUS) staining in plants expressing PIN7pro::GUS and green fluorescent protein (GFP) fluorescence in plants expressing PIN7pro::PIN7-GFP were observed, indicating that polar auxin transport in the root was downregulated under glycerol treatment. Analyses with auxin-related mutants showed that TIR1 and ARF7 were involved in regulating root growth under glycerol treatment. Glycerol-treated plants showed significant reductions in root meristem size and cell number as revealed by CYCB1;1pro::GUS staining. Furthermore, the expression of CDKA and CYCB1 decreased significantly in treated plants compared with control plants, implying possible alterations in cell cycle progression. Our data demonstrated that glycerol

  15. Phospholipase D affects translocation of NPR1 to the nucleus in Arabidopsis thaliana

    PubMed Central

    Janda, Martin; Šašek, Vladimír; Chmelařová, Hana; Andrejch, Jan; Nováková, Miroslava; Hajšlová, Jana; Burketová, Lenka; Valentová, Olga

    2015-01-01

    Phytohormone salicylic acid (SA) is a crucial component of plant-induced defense against biotrophic pathogens. Although the key players of the SA pathway are known, there are still gaps in the understanding of the molecular mechanism and the regulation of particular steps. In our previous research, we showed in Arabidopsis suspension cells that n-butanol, which specifically modulates phospholipase D activity, significantly suppresses the transcription of the pathogenesis related (PR-1) gene, which is generally accepted as the SA pathway marker. In the presented study, we have investigated the site of n-butanol action in the SA pathway. We were able to show in Arabidopsis plants treated with SA that n-butanol inhibits the transcription of defense genes (PR-1, WRKY38). Fluorescence microscopy of Arabidopsis thaliana mutants expressing 35S::NPR1-GFP (nonexpressor pathogenesis related 1) revealed significantly decreased nuclear localization of NPR1 in the presence of n-butanol. On the other hand, n-butanol did not decrease the nuclear localization of NPR1 in 35S::npr1C82A-GFP and 35S::npr1C216A-GFP mutants constitutively expressing NPR1 monomers. Mass spectrometric analysis of plant extracts showed that n-butanol significantly changes the metabolic fingerprinting while t-butanol had no effect. We found groups of the plant metabolites, influenced differently by SA and n-butanol treatment. Thus, we proposed several metabolites as markers for n-butanol action. PMID:25741350

  16. Phospholipase D affects translocation of NPR1 to the nucleus in Arabidopsis thaliana.

    PubMed

    Janda, Martin; Šašek, Vladimír; Chmelařová, Hana; Andrejch, Jan; Nováková, Miroslava; Hajšlová, Jana; Burketová, Lenka; Valentová, Olga

    2015-01-01

    Phytohormone salicylic acid (SA) is a crucial component of plant-induced defense against biotrophic pathogens. Although the key players of the SA pathway are known, there are still gaps in the understanding of the molecular mechanism and the regulation of particular steps. In our previous research, we showed in Arabidopsis suspension cells that n-butanol, which specifically modulates phospholipase D activity, significantly suppresses the transcription of the pathogenesis related (PR-1) gene, which is generally accepted as the SA pathway marker. In the presented study, we have investigated the site of n-butanol action in the SA pathway. We were able to show in Arabidopsis plants treated with SA that n-butanol inhibits the transcription of defense genes (PR-1, WRKY38). Fluorescence microscopy of Arabidopsis thaliana mutants expressing 35S::NPR1-GFP (nonexpressor pathogenesis related 1) revealed significantly decreased nuclear localization of NPR1 in the presence of n-butanol. On the other hand, n-butanol did not decrease the nuclear localization of NPR1 in 35S::npr1C82A-GFP and 35S::npr1C216A-GFP mutants constitutively expressing NPR1 monomers. Mass spectrometric analysis of plant extracts showed that n-butanol significantly changes the metabolic fingerprinting while t-butanol had no effect. We found groups of the plant metabolites, influenced differently by SA and n-butanol treatment. Thus, we proposed several metabolites as markers for n-butanol action. PMID:25741350

  17. Titanium dioxide nanoparticles (100-1000 mg/l) can affect vitamin E response in Arabidopsis thaliana.

    PubMed

    Szymańska, Renata; Kołodziej, Karolina; Ślesak, Ireneusz; Zimak-Piekarczyk, Paulina; Orzechowska, Aleksandra; Gabruk, Michał; Żądło, Andrzej; Habina, Iwona; Knap, Wiesław; Burda, Květoslava; Kruk, Jerzy

    2016-06-01

    In the present study we analyze the effect of seed treatment by a range of nano-TiO2 concentrations on the growth of Arabidopsis thaliana plants, on the vitamin E content and the expression of its biosynthetic genes, as well as activity of antioxidant enzymes and lipid peroxidation. To conduct the mechanistic analysis of nano-TiO2 on plants growth and antioxidant status we applied nanoparticles concentrations that are much higher than those reported in the environment. We find that as the concentration of nano-TiO2 increases, the biomass, and chlorophyll content in 5-week-old Arabidopsis thaliana plants decrease in a concentration dependent manner. In opposite, higher nano-TiO2 concentration enhanced root growth. Our results indicate that a high concentration of nano-TiO2 induces symptoms of toxicity and elevates the antioxidant level. We also find that the expression levels of tocopherol biosynthetic genes were either down- or upregulated in response to nano-TiO2. Thermoluminescence analysis shows that higher nano-TiO2 concentrations cause lipid peroxidation. To the best of our knowledge, this is the first report concerning the effect of nano-TiO2 on vitamin E status in plants. We conclude that nano-TiO2 affects the antioxidant response in Arabidopsis thaliana plants. This could be an effect of a changes in vitamin E gene expression that is diminished under lower tested nano-TiO2 concentrations and elevated under 1000 μg/ml. PMID:27060280

  18. Stability of small ubiquitin-like modifier (SUMO) proteases OVERLY TOLERANT TO SALT1 and -2 modulates salicylic acid signalling and SUMO1/2 conjugation in Arabidopsis thaliana.

    PubMed

    Bailey, Mark; Srivastava, Anjil; Conti, Lucio; Nelis, Stuart; Zhang, Cunjin; Florance, Hannah; Love, Andrew; Milner, Joel; Napier, Richard; Grant, Murray; Sadanandom, Ari

    2016-01-01

    Small ubiquitin-like modifier proteases 1 and 2 (SUMO1/2) have been linked to the regulation of salicylic acid (SA)-mediated defence signalling in Arabidopsis thaliana. In order to define the role of the SUMO proteases OVERLY TOLERANT TO SALT1 and -2 (OTS1/2) in defence and to provide insight into SUMO1/2-mediated regulation of SA signalling, we examined the status of SA-mediated defences in ots1/2 mutants. The ots1 ots2 double mutant displayed enhanced resistance to virulent Pseudomonas syringae and higher levels of SA compared with wild-type (WT) plants. Furthermore, ots1 ots2 mutants exhibited upregulated expression of the SA biosynthesis gene ICS1 in addition to enhanced SA-responsive ICS1 expression beyond that of WT. SA stimulated OTS1/2 degradation and promoted accumulation of SUMO1/2 conjugates. These results indicate that OTS1 and -2 act in a feedback loop in SA signalling and that de novo OTS1/2 synthesis works antagonistically to SA-promoted degradation, adjusting the abundance of OTS1/2 to moderate SA signalling. Accumulation of SUMO1/2 conjugates coincides with SA-promoted OTS degradation and may play a positive role in SA-mediated signalling in addition to its repressive roles reported elsewhere. PMID:26494731

  19. Stability of small ubiquitin-like modifier (SUMO) proteases OVERLY TOLERANT TO SALT1 and -2 modulates salicylic acid signalling and SUMO1/2 conjugation in Arabidopsis thaliana

    PubMed Central

    Bailey, Mark; Srivastava, Anjil; Conti, Lucio; Nelis, Stuart; Zhang, Cunjin; Florance, Hannah; Love, Andrew; Milner, Joel; Napier, Richard; Grant, Murray; Sadanandom, Ari

    2016-01-01

    Small ubiquitin-like modifier proteases 1 and 2 (SUMO1/2) have been linked to the regulation of salicylic acid (SA)-mediated defence signalling in Arabidopsis thaliana. In order to define the role of the SUMO proteases OVERLY TOLERANT TO SALT1 and -2 (OTS1/2) in defence and to provide insight into SUMO1/2-mediated regulation of SA signalling, we examined the status of SA-mediated defences in ots1/2 mutants. The ots1 ots2 double mutant displayed enhanced resistance to virulent Pseudomonas syringae and higher levels of SA compared with wild-type (WT) plants. Furthermore, ots1 ots2 mutants exhibited upregulated expression of the SA biosynthesis gene ICS1 in addition to enhanced SA-responsive ICS1 expression beyond that of WT. SA stimulated OTS1/2 degradation and promoted accumulation of SUMO1/2 conjugates. These results indicate that OTS1 and -2 act in a feedback loop in SA signalling and that de novo OTS1/2 synthesis works antagonistically to SA-promoted degradation, adjusting the abundance of OTS1/2 to moderate SA signalling. Accumulation of SUMO1/2 conjugates coincides with SA-promoted OTS degradation and may play a positive role in SA-mediated signalling in addition to its repressive roles reported elsewhere. PMID:26494731

  20. Loss-of-Function Mutants and Overexpression Lines of the Arabidopsis Cyclin CYCA1;2/TARDY ASYNCHRONOUS MEIOSIS Exhibit Different Defects in Prophase-I Meiocytes but Produce the Same Meiotic Products

    PubMed Central

    Wang, Yixing; Yang, Ming

    2014-01-01

    In Arabidopsis, loss-of-function mutations in the A-type cyclin CYCA1;2/TARDY ASYNCHRONOUS MEIOSIS (TAM) gene lead to the production of abnormal meiotic products including triads and dyads. Here we report that overexpression of TAM by the ASK1:TAM transgene also led to the production of triads and dyads in meiosis, as well as shriveled seeds, in a dominant fashion. However, the partial loss-of-function mutant tam-1, an ASK1:TAM line, and the wild type differed in dynamic changes in chromosome thread thickness from zygotene to diplotene. We also found that the pericentromeric heterochromatin regions in male meiocytes in tam-1 and tam-2 (a null allele) frequently formed a tight cluster at the pachytene and diplotene stages, in contrast to the infrequent occurrences of such clusters in the wild type and the ASK1:TAM line. Immunolocalization studies of the chromosome axial component ASY1 revealed that ASY1 was highly expressed at the appropriate male meiotic stages but not localized to the chromosomes in tam-2. The level of ASY1, however, was greatly reduced in another ASK1:TAM line with much overexpressed TAM. Our results indicate that the reduction and increase in the activity of TAM differentially affect chromosomal morphology and the action of ASY1 in prophase I. Based on these results, we propose that either the different meiotic defects or a common defect such as missing ASY1 on the chromosomal axes triggers a hitherto uncharacterized cell cycle checkpoint in the male meiocytes in the tam mutants and ASK1:TAM lines, leading to the production of the same abnormal meiotic products. PMID:25402453

  1. Overexpression of Arabidopsis Ceramide Synthases Differentially Affects Growth, Sphingolipid Metabolism, Programmed Cell Death, and Mycotoxin Resistance.

    PubMed

    Luttgeharm, Kyle D; Chen, Ming; Mehra, Amit; Cahoon, Rebecca E; Markham, Jonathan E; Cahoon, Edgar B

    2015-10-01

    Ceramide synthases catalyze an N-acyltransferase reaction using fatty acyl-coenzyme A (CoA) and long-chain base (LCB) substrates to form the sphingolipid ceramide backbone and are targets for inhibition by the mycotoxin fumonisin B1 (FB1). Arabidopsis (Arabidopsis thaliana) contains three genes encoding ceramide synthases with distinct substrate specificities: LONGEVITY ASSURANCE GENE ONE HOMOLOG1 (LOH1; At3g25540)- and LOH3 (At1g19260)-encoded ceramide synthases use very-long-chain fatty acyl-CoA and trihydroxy LCB substrates, and LOH2 (At3g19260)-encoded ceramide synthase uses palmitoyl-CoA and dihydroxy LCB substrates. In this study, complementary DNAs for each gene were overexpressed to determine the role of individual isoforms in physiology and sphingolipid metabolism. Differences were observed in growth resulting from LOH1 and LOH3 overexpression compared with LOH2 overexpression. LOH1- and LOH3-overexpressing plants had enhanced biomass relative to wild-type plants, due in part to increased cell division, suggesting that enhanced synthesis of very-long-chain fatty acid/trihydroxy LCB ceramides promotes cell division and growth. Conversely, LOH2 overexpression resulted in dwarfing. LOH2 overexpression also resulted in the accumulation of sphingolipids with C16 fatty acid/dihydroxy LCB ceramides, constitutive induction of programmed cell death, and accumulation of salicylic acid, closely mimicking phenotypes observed previously in LCB C-4 hydroxylase mutants defective in trihydroxy LCB synthesis. In addition, LOH2- and LOH3-overexpressing plants acquired increased resistance to FB1, whereas LOH1-overexpressing plants showed no increase in FB1 resistance, compared with wild-type plants, indicating that LOH1 ceramide synthase is most strongly inhibited by FB1. Overall, the findings described here demonstrate that overexpression of Arabidopsis ceramide synthases results in strongly divergent physiological and metabolic phenotypes, some of which have significance

  2. AtNPF5.5, a nitrate transporter affecting nitrogen accumulation in Arabidopsis embryo

    PubMed Central

    Léran, Sophie; Garg, Bharti; Boursiac, Yann; Corratgé-Faillie, Claire; Brachet, Chantal; Tillard, Pascal; Gojon, Alain; Lacombe, Benoît

    2015-01-01

    Dipeptide (Leu-Leu) and nitrate transport activities of 26 Arabidopsis NPF (NRT1/PTR Family) proteins were screened in Saccharomyces cerevisiae and Xenopus laevis oocytes, respectively. Dipeptide transport activity has been confirmed for 2 already known dipeptide transporters (AtNPF8.1 and AtNPF8.3) but none of the other tested NPFs displays dipeptide transport. The nitrate transport screen resulted in the identification of two new nitrate transporters, AtNPF5.5 and AtNPF5.10. The localization of the mRNA coding for NPF5.5 demonstrates that it is the first NPF transporter reported to be expressed in Arabidopsis embryo. Two independent homozygous npf5.5 KO lines display reduced total nitrogen content in the embryo as compared to WT plants, demonstrating an effect of NPF5.5 function on the embryo nitrogen content. Finally, NPF5.5 gene produces two different transcripts (AtNPF5.5a and AtNPF5.5b) encoding proteins with different N-terminal ends. Both proteins are able to transport nitrate in xenopus oocytes. PMID:25608465

  3. A mutation in protein phosphatase 2A regulatory subunit A affects auxin transport in Arabidopsis.

    PubMed Central

    Garbers, C; DeLong, A; Deruére, J; Bernasconi, P; Söll, D

    1996-01-01

    The phytohormone auxin controls processes such as cell elongation, root hair development and root branching. Tropisms, growth curvatures triggered by gravity, light and touch, are also auxin-mediated responses. Auxin is synthesized in the shoot apex and transported through the stem, but the molecular mechanism of auxin transport is not well understood. Naphthylphthalamic acid (NPA) and other inhibitors of auxin transport block tropic curvature responses and inhibit root and shoot elongation. We have isolated a novel Arabidopsis thaliana mutant designated roots curl in NPA (rcn1). Mutant seedlings exhibit altered responses to NPA in root curling and hypocotyl elongation. Auxin efflux in mutant seedlings displays increased sensitivity to NPA. The rcn1 mutation was transferred-DNA (T-DNA) tagged and sequences flanking the T-DNA insert were cloned. Analysis of the RCN1 cDNA reveals that the T-DNA insertion disrupts a gene for the regulatory A subunit of protein phosphatase 2A (PP2A-A). The RCN1 gene rescues the rcn1 mutant phenotype and also complements the temperature-sensitive phenotype of the Saccharomyces cerevisiae PP2A-A mutation, tpd3-1. These data implicate protein phosphatase 2A in the regulation of auxin transport in Arabidopsis. Images PMID:8641277

  4. Overexpression of the Arabidopsis thaliana signalling peptide TAXIMIN1 affects lateral organ development

    PubMed Central

    Colling, Janine; Tohge, Takayuki; De Clercq, Rebecca; Brunoud, Geraldine; Vernoux, Teva; Fernie, Alisdair R.; Makunga, Nokwanda P.; Goossens, Alain; Pauwels, Laurens

    2015-01-01

    Lateral organ boundary formation is highly regulated by transcription factors and hormones such as auxins and brassinosteroids. However, in contrast to many other developmental processes in plants, no role for signalling peptides in the regulation of this process has been reported yet. The first characterization of the secreted cysteine-rich TAXIMIN (TAX) signalling peptides in Arabidopsis is presented here. TAX1 overexpression resulted in minor alterations in the primary shoot and root metabolome, abnormal fruit morphology, and fusion of the base of cauline leaves to stems forming a decurrent leaf attachment. The phenotypes at the paraclade junction match TAX1 promoter activity in this region and are similar to loss of LATERAL ORGAN FUSION (LOF) transcription factor function. Nevertheless, TAX1 expression was unchanged in lof1lof2 paraclade junctions and, conversely, LOF gene expression was unchanged in TAX1 overexpressing plants, suggesting TAX1 may act independently. This study identifies TAX1 as the first plant signalling peptide influencing lateral organ separation and implicates the existence of a peptide signal cascade regulating this process in Arabidopsis. PMID:26071531

  5. Overexpression of AtTTP Affects ARF17 Expression and Leads to Male Sterility in Arabidopsis

    PubMed Central

    Shi, Zhi-Hao; Zhang, Cheng; Xu, Xiao-Feng; Zhu, Jun; Zhou, Que; Ma, Li-Juan; Niu, Jin; Yang, Zhong-Nan

    2015-01-01

    Callose synthesis is critical for the formation of the pollen wall pattern. CalS5 is thought to be the major synthethase for the callose wall. In the Arabidopsis anther, ARF17 regulates the expression of CalS5 and is the target of miR160. Plants expressing miR160-resistant ARF17 (35S:5mARF17 lines) with increased ARF17 mRNA levels display male sterility. Here we report a zinc finger family gene, AtTTP, which is involved in miR160 maturation and callose synthesis in Arabidopsis. AtTTP is expressed in microsporocytes, tetrads and tapetal cells in the anther. Over-expression lines of AtTTP (AtTTP-OE line) exhibited reduced male fertility. CalS5 expression was tremendously reduced and the tetrad callose wall became much thinner in the AtTTP-OE line. Northern blotting hybridization and quantitative RT-PCR analysis revealed that miR160 was decreased, while the expression of ARF17 was increased in the AtTTP-OE line. Based on these results, we propose that AtTTP associates with miR160 in order to regulate the ARF17 expression needed for callose synthesis and pollen wall formation. PMID:25822980

  6. Seed Production Affects Maternal Growth and Senescence in Arabidopsis1[OPEN

    PubMed Central

    Philipp, Matthias Anton; Guthörl, Daniela

    2016-01-01

    Correlative control (influence of one organ over another organ) of seeds over maternal growth is one of the most obvious phenotypic expressions of the trade-off between growth and reproduction. However, the underlying molecular mechanisms are largely unknown. Here, we characterize the physiological and molecular effects of correlative inhibition by seeds on Arabidopsis (Arabidopsis thaliana) inflorescences, i.e. global proliferative arrest (GPA) during which all maternal growth ceases upon the production of a given number of seeds. We observed transcriptional responses to growth- and branching-inhibitory hormones, and low mitotic activity in meristems upon GPA, but found that meristems retain their identity and proliferative potential. In shoot tissues, we detected the induction of stress- and senescence-related gene expression upon fruit production and GPA, and a drop in chlorophyll levels, suggestive of altered source-sink relationships between vegetative shoot and reproductive tissues. Levels of shoot reactive oxygen species, however, strongly decreased upon GPA, a phenomenon that is associated with bud dormancy in some perennials. Indeed, gene expression changes in arrested apical inflorescences after fruit removal resembled changes observed in axillary buds following release from apical dominance. This suggests that GPA represents a form of bud dormancy, and that dominance is gradually transferred from growing inflorescences to maturing seeds, allowing offspring control over maternal resources, simultaneously restricting offspring number. This would provide a mechanistic explanation for the constraint between offspring quality and quantity. PMID:27009281

  7. A mutation in protein phosphatase 2A regulatory subunit A affects auxin transport in Arabidopsis

    NASA Technical Reports Server (NTRS)

    Garbers, C.; DeLong, A.; Deruere, J.; Bernasconi, P.; Soll, D.; Evans, M. L. (Principal Investigator)

    1996-01-01

    The phytohormone auxin controls processes such as cell elongation, root hair development and root branching. Tropisms, growth curvatures triggered by gravity, light and touch, are also auxin-mediated responses. Auxin is synthesized in the shoot apex and transported through the stem, but the molecular mechanism of auxin transport is not well understood. Naphthylphthalamic acid (NPA) and other inhibitors of auxin transport block tropic curvature responses and inhibit root and shoot elongation. We have isolated a novel Arabidopsis thaliana mutant designated roots curl in NPA (rcn1). Mutant seedlings exhibit altered responses to NPA in root curling and hypocotyl elongation. Auxin efflux in mutant seedlings displays increased sensitivity to NPA. The rcn1 mutation was transferred-DNA (T-DNA) tagged and sequences flanking the T-DNA insert were cloned. Analysis of the RCN1 cDNA reveals that the T-DNA insertion disrupts a gene for the regulatory A subunit of protein phosphatase 2A (PP2A-A). The RCN1 gene rescues the rcn1 mutant phenotype and also complements the temperature-sensitive phenotype of the Saccharomyces cerevisiae PP2A-A mutation, tpd3-1. These data implicate protein phosphatase 2A in the regulation of auxin transport in Arabidopsis.

  8. Overexpression of the Arabidopsis thaliana signalling peptide TAXIMIN1 affects lateral organ development.

    PubMed

    Colling, Janine; Tohge, Takayuki; De Clercq, Rebecca; Brunoud, Geraldine; Vernoux, Teva; Fernie, Alisdair R; Makunga, Nokwanda P; Goossens, Alain; Pauwels, Laurens

    2015-08-01

    Lateral organ boundary formation is highly regulated by transcription factors and hormones such as auxins and brassinosteroids. However, in contrast to many other developmental processes in plants, no role for signalling peptides in the regulation of this process has been reported yet. The first characterization of the secreted cysteine-rich TAXIMIN (TAX) signalling peptides in Arabidopsis is presented here. TAX1 overexpression resulted in minor alterations in the primary shoot and root metabolome, abnormal fruit morphology, and fusion of the base of cauline leaves to stems forming a decurrent leaf attachment. The phenotypes at the paraclade junction match TAX1 promoter activity in this region and are similar to loss of LATERAL ORGAN FUSION (LOF) transcription factor function. Nevertheless, TAX1 expression was unchanged in lof1lof2 paraclade junctions and, conversely, LOF gene expression was unchanged in TAX1 overexpressing plants, suggesting TAX1 may act independently. This study identifies TAX1 as the first plant signalling peptide influencing lateral organ separation and implicates the existence of a peptide signal cascade regulating this process in Arabidopsis. PMID:26071531

  9. Surface Chemical Gradient Affects the Differentiation of Human Adipose-Derived Stem Cells via ERK1/2 Signaling Pathway.

    PubMed

    Liu, Xujie; Shi, Shengjun; Feng, Qingling; Bachhuka, Akash; He, Wei; Huang, Qianli; Zhang, Ranran; Yang, Xing; Vasilev, Krasimir

    2015-08-26

    To understand the role of surface chemistry on cell behavior and the associated molecular mechanisms, we developed and utilized a surface chemical gradient of amine functional groups by carefully adjusting the gas composition of 1,7-octadiene (OD) and allylamine (AA) of the plasma phase above a moving substrate. The chemical gradient surface used in the present work shows an increasing N/C ratio and wettability from the OD side toward the AA side with no change in surface topography. Under standard culture conditions (with serum), human adipose-derived stem cells (hASCs) adhesion and spreading area increased toward the AA side of the gradient. However, there were no differences in cell behavior in the absence of serum. These results, supported by the trends in proteins adsorption on the gradient surface, demonstrated that surface chemistry affects the response of hASCs through cell-adhesive serum proteins, rather than interacting directly with the cells. The expression of p-ERK and the osteogenic differentiation increased toward the AA side of the gradient, while adipogenic differentiation decreased in the same direction; however, when the activation of ERK1/2 was blocked by PD98059, the levels of osteogenic or adipogenic differentiation on different regions of the chemical gradient were the same. This indicates that ERK1/2 may be an important downstream signaling pathway of surface chemistry directed stem cell fate. PMID:26237746

  10. A Novel Role for Arabidopsis CBL1 in Affecting Plant Responses to Glucose and Gibberellin during Germination and Seedling Development

    PubMed Central

    Li, Zhi-Yong; Xu, Zhao-Shi; Chen, Yang; He, Guang-Yuan; Yang, Guang-Xiao; Chen, Ming; Li, Lian-Cheng; Ma, You-Zhi

    2013-01-01

    Glucose and phytohormones such as abscisic acid (ABA), ethylene, and gibberellin (GA) coordinately regulate germination and seedling development. However, there is still inadequate evidence to link their molecular roles in affecting plant responses. Calcium acts as a second messenger in a diverse range of signal transduction pathways. As calcium sensors unique to plants, calcineurin B-like (CBL) proteins are well known to modulate abiotic stress responses. In this study, it was found that CBL1 was induced by glucose in Arabidopsis. Loss-of-function mutant cbl1 exhibited hypersensitivity to glucose and paclobutrazol, a GA biosynthetic inhibitor. Several sugar-responsive and GA biosynthetic gene expressions were altered in the cbl1 mutant. CBL1 protein physically interacted with AKINβ1, the regulatory β subunit of the SnRK1 complex which has a central role in sugar signaling. Our results indicate a novel role for CBL1 in modulating responses to glucose and GA signals. PMID:23437128

  11. ANTHOCYANINLESS2, a homeobox gene affecting anthocyanin distribution and root development in Arabidopsis.

    PubMed Central

    Kubo, H; Peeters, A J; Aarts, M G; Pereira, A; Koornneef, M

    1999-01-01

    The ANTHOCYANINLESS2 (ANL2) gene was isolated from Arabidopsis by using the maize Enhancer-Inhibitor transposon tagging system. Sequencing of the ANL2 gene showed that it encodes a homeodomain protein belonging to the HD-GLABRA2 group. As we report here, this homeobox gene is involved in the accumulation of anthocyanin and in root development. Histological observations of the anl2 mutant revealed that the accumulation of anthocyanin was greatly suppressed in subepidermal cells but only slightly reduced in epidermal cells. Furthermore, the primary roots of the anl2 mutant showed an aberrant cellular organization. We discuss a possible role of ANL2 in the accumulation of anthocyanin and cellular organization of the primary root. PMID:10402424

  12. Non-Photochemical Quenching Capacity in Arabidopsis thaliana Affects Herbivore Behaviour

    PubMed Central

    Johansson Jänkänpää, Hanna; Frenkel, Martin; Zulfugarov, Ismayil; Reichelt, Michael; Krieger-Liszkay, Anja; Mishra, Yogesh; Gershenzon, Jonathan; Moen, Jon; Lee, Choon-Hwan; Jansson, Stefan

    2013-01-01

    Under natural conditions, plants have to cope with numerous stresses, including light-stress and herbivory. This raises intriguing questions regarding possible trade-offs between stress defences and growth. As part of a program designed to address these questions we have compared herbivory defences and damage in wild type Arabidopsis thaliana and two “photoprotection genotypes”, npq4 and oePsbS, which respectively lack and overexpress PsbS (a protein that plays a key role in qE-type non-photochemical quenching). In dual-choice feeding experiments both a specialist (Plutella xylostella) and a generalist (Spodoptera littoralis) insect herbivore preferred plants that expressed PsbS most strongly. In contrast, although both herbivores survived equally well on each of the genotypes, for oviposition female P. xylostella adults preferred plants that expressed PsbS least strongly. However, there were no significant differences between the genotypes in levels of the 10 most prominent glucosinolates; key substances in the Arabidopsis anti-herbivore chemical defence arsenal. After transfer from a growth chamber to the field we detected significant differences in the genotypes’ metabolomic profiles at all tested time points, using GC-MS, but no consistent “metabolic signature” for the lack of PsbS. These findings suggest that the observed differences in herbivore preferences were due to differences in the primary metabolism of the plants rather than their contents of typical “defence compounds”. A potentially significant factor is that superoxide accumulated most rapidly and to the highest levels under high light conditions in npq4 mutants. This could trigger changes in planta that are sensed by herbivores either directly or indirectly, following its dismutation to H2O2. PMID:23301046

  13. ahg12 is a dominant proteasome mutant that affects multiple regulatory systems for germination of Arabidopsis.

    PubMed

    Hayashi, Shimpei; Hirayama, Takashi

    2016-01-01

    The ubiquitin-proteasome system is fundamentally involved in myriad biological phenomena of eukaryotes. In plants, this regulated protein degradation system has a pivotal role in the cellular response mechanisms for both internal and external stimuli, such as plant hormones and environmental stresses. Information about substrate selection by the ubiquitination machinery has accumulated, but there is very little information about selectivity for substrates at the proteasome. Here, we report characterization of a novel abscisic acid (ABA)-hypersensitive mutant named ABA hypersensitive germination12 (ahg12) in Arabidopsis. The ahg12 mutant showed a unique pleiotropic phenotype, including hypersensitivity to ABA and ethylene, and hyposensitivity to light. Map-based cloning identified the ahg12 mutation to cause an amino acid conversion in the L23 loop of RPT5a, which is predicted to form the pore structure of the 19S RP complex of the proteasome. Transient expression assays demonstrated that some plant-specific signaling components accumulated at higher levels in the ahg12 mutant. These results suggest that the ahg12 mutation led to changes in the substrate preference of the 26S proteasome. The discovery of the ahg12 mutation thus will contribute to elucidate the characteristics of the regulated protein degradation system. PMID:27139926

  14. Transgene expression patterns indicate that spaceflight affects stress signal perception and transduction in arabidopsis

    NASA Technical Reports Server (NTRS)

    Paul, A. L.; Daugherty, C. J.; Bihn, E. A.; Chapman, D. K.; Norwood, K. L.; Ferl, R. J.

    2001-01-01

    The use of plants as integral components of life support systems remains a cornerstone of strategies for long-term human habitation of space and extraterrestrial colonization. Spaceflight experiments over the past few decades have refined the hardware required to grow plants in low-earth orbit and have illuminated fundamental issues regarding spaceflight effects on plant growth and development. Potential incipient hypoxia, resulting from the lack of convection-driven gas movement, has emerged as a possible major impact of microgravity. We developed transgenic Arabidopsis containing the alcohol dehydrogenase (Adh) gene promoter linked to the beta-glucuronidase (GUS) reporter gene to address specifically the possibility that spaceflight induces the plant hypoxia response and to assess whether any spaceflight response was similar to control terrestrial hypoxia-induced gene expression patterns. The staining patterns resulting from a 5-d mission on the orbiter Columbia during mission STS-93 indicate that the Adh/GUS reporter gene was activated in roots during the flight. However, the patterns of expression were not identical to terrestrial control inductions. Moreover, although terrestrial hypoxia induces Adh/GUS expression in the shoot apex, no apex staining was observed in the spaceflight plants. This indicates that either the normal hypoxia response signaling is impaired in spaceflight or that spaceflight inappropriately induces Adh/GUS activity for reasons other than hypoxia.

  15. ahg12 is a dominant proteasome mutant that affects multiple regulatory systems for germination of Arabidopsis

    PubMed Central

    Hayashi, Shimpei; Hirayama, Takashi

    2016-01-01

    The ubiquitin-proteasome system is fundamentally involved in myriad biological phenomena of eukaryotes. In plants, this regulated protein degradation system has a pivotal role in the cellular response mechanisms for both internal and external stimuli, such as plant hormones and environmental stresses. Information about substrate selection by the ubiquitination machinery has accumulated, but there is very little information about selectivity for substrates at the proteasome. Here, we report characterization of a novel abscisic acid (ABA)-hypersensitive mutant named ABA hypersensitive germination12 (ahg12) in Arabidopsis. The ahg12 mutant showed a unique pleiotropic phenotype, including hypersensitivity to ABA and ethylene, and hyposensitivity to light. Map-based cloning identified the ahg12 mutation to cause an amino acid conversion in the L23 loop of RPT5a, which is predicted to form the pore structure of the 19S RP complex of the proteasome. Transient expression assays demonstrated that some plant-specific signaling components accumulated at higher levels in the ahg12 mutant. These results suggest that the ahg12 mutation led to changes in the substrate preference of the 26S proteasome. The discovery of the ahg12 mutation thus will contribute to elucidate the characteristics of the regulated protein degradation system. PMID:27139926

  16. Cryopreservation affects ROS-induced oxidative stress and antioxidant response in Arabidopsis seedlings.

    PubMed

    Chen, Guan-Qun; Ren, Li; Zhang, Jie; Reed, Barbara M; Zhang, Di; Shen, Xiao-Hui

    2015-02-01

    Plant recovery status after cryopreservation by vitrification had a negative relationship to the oxidative stress induced by reactive oxygen species (ROS). Arabidopsis thaliana seedlings germinated for 48 h or 72 h with different survival tolerances were examined at five steps of cryopreservation, to determine the role of ROS (O2(-), H2O2 and OH) and antioxidant systems (SOD, POD, CAT, AsA and GSH) in cryo-injury. In addition, the effects of the steps on membrane lipid peroxidation were studied using malondialdehyde (MDA) as an indicator. The results indicated that H2O2-induced oxidative stress at the steps of dehydration and rapid warming was the main cause of cryo-injury of 48-h seedlings (high survival rate) and 72-h seedlings (no survival). The H2O2 was mainly generated in cotyledons, shoot tips and roots of seedlings as indicated by Amplex Red staining. Low survival of 72-h seedlings was associated with severe membrane lipid peroxidation, which was caused by increased OH generation activity and decreased SOD activity. The antioxidant-related gene expression by qRT-PCR and physiological assays suggested that the antioxidant system of 48-h seedlings were activated by ROS, and they mounted a defense against oxidative stress. A high level of ROS led to the weakening of the antioxidant system of 72-h seedlings. Correlation analysis indicated that enhanced antioxidant enzymes activities contributed to the high survival rate of 48-h seedlings, which could reflect by cryopreservation of antioxidant mutant seedlings. This model system indicated that elevated CAT activity and AsA content were determinants of cryogenic stress tolerance, whose manipulation could improve the recovery of seedlings after cryopreservation. PMID:25489814

  17. Mutations of Arabidopsis TBL32 and TBL33 Affect Xylan Acetylation and Secondary Wall Deposition

    PubMed Central

    Yuan, Youxi; Teng, Quincy; Zhong, Ruiqin; Haghighat, Marziyeh; Richardson, Elizabeth A.; Ye, Zheng-Hua

    2016-01-01

    Xylan is a major acetylated polymer in plant lignocellulosic biomass and it can be mono- and di-acetylated at O-2 and O-3 as well as mono-acetylated at O-3 of xylosyl residues that is substituted with glucuronic acid (GlcA) at O-2. Based on the finding that ESK1, an Arabidopsis thaliana DUF231 protein, specifically mediates xylan 2-O- and 3-O-monoacetylation, we previously proposed that different acetyltransferase activities are required for regiospecific acetyl substitutions of xylan. Here, we demonstrate the functional roles of TBL32 and TBL33, two ESK1 close homologs, in acetyl substitutions of xylan. Simultaneous mutations of TBL32 and TBL33 resulted in a significant reduction in xylan acetyl content and endoxylanase digestion of the mutant xylan released GlcA-substituted xylooligomers without acetyl groups. Structural analysis of xylan revealed that the tbl32 tbl33 mutant had a nearly complete loss of 3-O-acetylated, 2-O-GlcA-substituted xylosyl residues. A reduction in 3-O-monoacetylated and 2,3-di-O-acetylated xylosyl residues was also observed. Simultaneous mutations of TBL32, TBL33 and ESK1 resulted in a severe reduction in xylan acetyl level down to 15% of that of the wild type, and concomitantly, severely collapsed vessels and stunted plant growth. In particular, the S2 layer of secondary walls in xylem vessels of tbl33 esk1 and tbl32 tbl33 esk1 exhibited an altered structure, indicating abnormal assembly of secondary wall polymers. These results demonstrate that TBL32 and TBL33 play an important role in xylan acetylation and normal deposition of secondary walls. PMID:26745802

  18. Verticillium longisporum infection affects the leaf apoplastic proteome, metabolome, and cell wall properties in Arabidopsis thaliana.

    PubMed

    Floerl, Saskia; Majcherczyk, Andrzej; Possienke, Mareike; Feussner, Kirstin; Tappe, Hella; Gatz, Christiane; Feussner, Ivo; Kües, Ursula; Polle, Andrea

    2012-01-01

    Verticillium longisporum (VL) is one of the most devastating diseases in important oil crops from the family of Brassicaceae. The fungus resides for much time of its life cycle in the extracellular fluid of the vascular system, where it cannot be controlled by conventional fungicides. To obtain insights into the biology of VL-plant interaction in the apoplast, the secretome consisting of the extracellular proteome and metabolome as well as cell wall properties were studied in the model Brassicaceae, Arabidopsis thaliana. VL infection resulted in increased production of cell wall material with an altered composition of carbohydrate polymers and increased lignification. The abundance of several hundred soluble metabolites changed in the apoplast of VL-infected plants including signalling and defence compounds such as glycosides of salicylic acid, lignans and dihydroxybenzoic acid as well as oxylipins. The extracellular proteome of healthy leaves was enriched in antifungal proteins. VL caused specific increases in six apoplast proteins (three peroxidases PRX52, PRX34, P37, serine carboxypeptidase SCPL20, α-galactosidase AGAL2 and a germin-like protein GLP3), which have functions in defence and cell wall modification. The abundance of a lectin-like, chitin-inducible protein (CILLP) was reduced. Since the transcript levels of most of the induced proteins were not elevated until late infection time points (>20 dpi), whereas those of CILLP and GLP3 were reduced at earlier time points, our results may suggest that VL enhances its virulence by rapid down-regulation and delay of induction of plant defence genes. PMID:22363647

  19. Mutations of Arabidopsis TBL32 and TBL33 affect xylan acetylation and secondary wall deposition

    DOE PAGESBeta

    Yuan, Youxi; Teng, Quincy; Zhong, Ruiqin; Haghighat, Marziyeh; Richardson, Elizabeth A.; Ye, Zheng -Hua; Zhang, Jin -Song

    2016-01-08

    Xylan is a major acetylated polymer in plant lignocellulosic biomass and it can be monoand di-acetylated at O-2 and O-3 as well as mono-acetylated at O-3 of xylosyl residues that is substituted with glucuronic acid (GlcA) at O-2. Based on the finding that ESK1, an Arabidopsis thaliana DUF231 protein, specifically mediates xylan 2-O- and 3-O-monoacetylation, we previously proposed that different acetyltransferase activities are required for regiospecific acetyl substitutions of xylan. Here, we demonstrate the functional roles of TBL32 and TBL33, two ESK1 close homologs, in acetyl substitutions of xylan. Simultaneous mutations of TBL32 and TBL33 resulted in a significant reductionmore » in xylan acetyl content and endoxylanase digestion of the mutant xylan released GlcA-substituted xylooligomers without acetyl groups. Structural analysis of xylan revealed that the tbl32 tbl33 mutant had a nearly complete loss of 3-O-acetylated, 2-O-GlcA-substituted xylosyl residues. A reduction in 3-Omonoacetylated and 2,3-di-O-acetylated xylosyl residues was also observed. Simultaneous mutations of TBL32, TBL33 and ESK1 resulted in a severe reduction in xylan acetyl level down to 15% of that of the wild type, and concomitantly, severely collapsed vessels and stunted plant growth. In particular, the S2 layer of secondary walls in xylem vessels of tbl33 esk1 and tbl32 tbl33 esk1 exhibited an altered structure, indicating abnormal assembly of secondary wall polymers. Furthermore, these results demonstrate that TBL32 and TBL33 play an important role in xylan acetylation and normal deposition of secondary walls.« less

  20. Mutations in HISTONE ACETYLTRANSFERASE1 affect sugar response and gene expression in Arabidopsis

    PubMed Central

    Heisel, Timothy J.; Li, Chun Yao; Grey, Katia M.; Gibson, Susan I.

    2013-01-01

    Nutrient response networks are likely to have been among the first response networks to evolve, as the ability to sense and respond to the levels of available nutrients is critical for all organisms. Although several forward genetic screens have been successful in identifying components of plant sugar-response networks, many components remain to be identified. Toward this end, a reverse genetic screen was conducted in Arabidopsis thaliana to identify additional components of sugar-response networks. This screen was based on the rationale that some of the genes involved in sugar-response networks are likely to be themselves sugar regulated at the steady-state mRNA level and to encode proteins with activities commonly associated with response networks. This rationale was validated by the identification of hac1 mutants that are defective in sugar response. HAC1 encodes a histone acetyltransferase. Histone acetyltransferases increase transcription of specific genes by acetylating histones associated with those genes. Mutations in HAC1 also cause reduced fertility, a moderate degree of resistance to paclobutrazol and altered transcript levels of specific genes. Previous research has shown that hac1 mutants exhibit delayed flowering. The sugar-response and fertility defects of hac1 mutants may be partially explained by decreased expression of AtPV42a and AtPV42b, which are putative components of plant SnRK1 complexes. SnRK1 complexes have been shown to function as central regulators of plant nutrient and energy status. Involvement of a histone acetyltransferase in sugar response provides a possible mechanism whereby nutritional status could exert long-term effects on plant development and metabolism. PMID:23882272

  1. Verticillium longisporum Infection Affects the Leaf Apoplastic Proteome, Metabolome, and Cell Wall Properties in Arabidopsis thaliana

    PubMed Central

    Floerl, Saskia; Majcherczyk, Andrzej; Possienke, Mareike; Feussner, Kirstin; Tappe, Hella; Gatz, Christiane; Feussner, Ivo; Kües, Ursula; Polle, Andrea

    2012-01-01

    Verticillium longisporum (VL) is one of the most devastating diseases in important oil crops from the family of Brassicaceae. The fungus resides for much time of its life cycle in the extracellular fluid of the vascular system, where it cannot be controlled by conventional fungicides. To obtain insights into the biology of VL-plant interaction in the apoplast, the secretome consisting of the extracellular proteome and metabolome as well as cell wall properties were studied in the model Brassicaceae, Arabidopsis thaliana. VL infection resulted in increased production of cell wall material with an altered composition of carbohydrate polymers and increased lignification. The abundance of several hundred soluble metabolites changed in the apoplast of VL-infected plants including signalling and defence compounds such as glycosides of salicylic acid, lignans and dihydroxybenzoic acid as well as oxylipins. The extracellular proteome of healthy leaves was enriched in antifungal proteins. VL caused specific increases in six apoplast proteins (three peroxidases PRX52, PRX34, P37, serine carboxypeptidase SCPL20, α-galactosidase AGAL2 and a germin-like protein GLP3), which have functions in defence and cell wall modification. The abundance of a lectin-like, chitin-inducible protein (CILLP) was reduced. Since the transcript levels of most of the induced proteins were not elevated until late infection time points (>20 dpi), whereas those of CILLP and GLP3 were reduced at earlier time points, our results may suggest that VL enhances its virulence by rapid down-regulation and delay of induction of plant defence genes. PMID:22363647

  2. Suppression of PCD-related genes affects salt tolerance in Arabidopsis.

    PubMed

    Bahieldin, Ahmed; Alqarni, Dhafer A M; Atef, Ahmed; Gadalla, Nour O; Al-Matary, Mohammed; Edris, Sherif; Al-Kordy, Magdy A; Makki, Rania M; Al-Doss, Abdullah A; Sabir, Jamal S M; Mutwakil, Mohammed H Z; El-Domyati, Fotouh M

    2016-01-01

    This work aims at examining a natural exciting phenomenon suggesting that suppression of genes inducing programmed cell death (PCD) might confer tolerance against abiotic stresses in plants. PCD-related genes were induced in tobacco under oxalic acid (OA) treatment (20mM), and plant cells were characterized to confirm the incidence of PCD. The results indicated that PCD was triggered 24h after the exposure to OA. Then, RNAs were extracted from tobacco cells 0, 2, 6, 12 and 24h after treatment for deep sequencing. RNA-Seq analyses were done with a special emphasis to clusters whose PCD-related genes were upregulated after 2h of OA exposure. Accordingly, 23 tobacco PCD-related genes were knocked down via virus-induced gene silencing (VIGS), whereas our results indicated the influence of five of them on inducing or suppressing PCD. Knockout T-DNA insertion mutants of these five genes in Arabidopsis were tested under salt stress (0, 100, 150, and 200mM NaCl), and the results indicated that a mutant of an antiapoptotic gene, namely Bax Inhibitor-1 (BI-1), whose VIGS induced PCD in tobacco, was salt sensitive, while a mutant of an apoptotic gene, namely mildew resistance locus O (Mlo), whose VIGS suppressed PCD, was salt tolerant as compared to the WT (Col) control. These data support our hypothesis that retarding PCD-inducing genes can result in higher levels of salt tolerance, while retarding PCD-suppressing genes can result in lower levels of salt tolerance in plants. PMID:27052474

  3. Regulation of Arabidopsis Flowering by the Histone Mark Readers MRG1/2 via Interaction with CONSTANS to Modulate FT Expression

    PubMed Central

    Liu, Yanchao; Jiang, Wen; Huang, Ying; Dong, Ai-Wu

    2014-01-01

    Day-length is important for regulating the transition to reproductive development (flowering) in plants. In the model plant Arabidopsis thaliana, the transcription factor CONSTANS (CO) promotes expression of the florigen FLOWERING LOCUS T (FT), constituting a key flowering pathway under long-day photoperiods. Recent studies have revealed that FT expression is regulated by changes of histone modification marks of the FT chromatin, but the epigenetic regulators that directly interact with the CO protein have not been identified. Here, we show that the Arabidopsis Morf Related Gene (MRG) group proteins MRG1 and MRG2 act as H3K4me3/H3K36me3 readers and physically interact with CO to activate FT expression. In vitro binding analyses indicated that the chromodomains of MRG1 and MRG2 preferentially bind H3K4me3/H3K36me3 peptides. The mrg1 mrg2 double mutant exhibits reduced mRNA levels of FT, but not of CO, and shows a late-flowering phenotype under the long-day but not short-day photoperiod growth conditions. MRG2 associates with the chromatin of FT promoter in a way dependent of both CO and H3K4me3/H3K36me3. Vice versa, loss of MRG1 and MRG2 also impairs CO binding at the FT promoter. Crystal structure analyses of MRG2 bound with H3K4me3/H3K36me3 peptides together with mutagenesis analysis in planta further demonstrated that MRG2 function relies on its H3K4me3/H3K36me3-binding activity. Collectively, our results unravel a novel chromatin regulatory mechanism, linking functions of MRG1 and MRG2 proteins, H3K4/H3K36 methylations, and CO in FT activation in the photoperiodic regulation of flowering time in plants. PMID:25211338

  4. Arabidopsis thaliana DOF6 negatively affects germination in non-after-ripened seeds and interacts with TCP14

    PubMed Central

    Rueda-Romero, Paloma; Barrero-Sicilia, Cristina; Gómez-Cadenas, Aurelio; Carbonero, Pilar; Oñate-Sánchez, Luis

    2012-01-01

    Seed dormancy prevents seeds from germinating under environmental conditions unfavourable for plant growth and development and constitutes an evolutionary advantage. Dry storage, also known as after-ripening, gradually decreases seed dormancy by mechanisms not well understood. An Arabidopsis thaliana DOF transcription factor gene (DOF6) affecting seed germination has been characterized. The transcript levels of this gene accumulate in dry seeds and decay gradually during after-ripening and also upon seed imbibition. While constitutive over-expression of DOF6 produced aberrant growth and sterility in the plant, its over-expression induced upon seed imbibition triggered delayed germination, abscisic acid (ABA)-hypersensitive phenotypes and increased expression of the ABA biosynthetic gene ABA1 and ABA-related stress genes. Wild-type germination and gene expression were gradually restored during seed after-ripening, despite of DOF6-induced over-expression. DOF6 was found to interact in a yeast two-hybrid system and in planta with TCP14, a previously described positive regulator of seed germination. The expression of ABA1 and ABA-related stress genes was also enhanced in tcp14 knock-out mutants. Taken together, these results indicate that DOF6 negatively affects seed germination and opposes TCP14 function in the regulation of a specific set of ABA-related genes. PMID:22155632

  5. Canopy light cues affect emission of constitutive and methyl jasmonate-induced volatile organic compounds in Arabidopsis thaliana.

    PubMed

    Kegge, Wouter; Weldegergis, Berhane T; Soler, Roxina; Vergeer-Van Eijk, Marleen; Dicke, Marcel; Voesenek, Laurentius A C J; Pierik, Ronald

    2013-11-01

    The effects of plant competition for light on the emission of plant volatile organic compounds (VOCs) were studied by investigating how different light qualities that occur in dense vegetation affect the emission of constitutive and methyl-jasmonate-induced VOCs. Arabidopsis thaliana Columbia (Col-0) plants and Pieris brassicae caterpillars were used as a biological system to study the effects of light quality manipulations on VOC emissions and attraction of herbivores. VOCs were analysed using gas chromatography-mass spectrometry and the effects of light quality, notably the red : far red light ratio (R : FR), on expression of genes associated with VOC production were studied using reverse transcriptase-quantitative PCR. The emissions of both constitutive and methyl-jasmonate-induced green leaf volatiles and terpenoids were partially suppressed under low R : FR and severe shading conditions. Accordingly, the VOC-based preference of neonates of the specialist lepidopteran herbivore P. brassicae was significantly affected by the R : FR ratio. We conclude that VOC-mediated interactions among plants and between plants and organisms at higher trophic levels probably depend on light alterations caused by nearby vegetation. Studies on plant-plant and plant-insect interactions through VOCs should take into account the light quality within dense stands when extrapolating to natural and agricultural field conditions. PMID:23845065

  6. Rhizosphere microbial community composition affects cadmium and zinc uptake by the metal-hyperaccumulating plant Arabidopsis halleri.

    PubMed

    Muehe, E Marie; Weigold, Pascal; Adaktylou, Irini J; Planer-Friedrich, Britta; Kraemer, Ute; Kappler, Andreas; Behrens, Sebastian

    2015-03-01

    The remediation of metal-contaminated soils by phytoextraction depends on plant growth and plant metal accessibility. Soil microorganisms can affect the accumulation of metals by plants either by directly or indirectly stimulating plant growth and activity or by (im)mobilizing and/or complexing metals. Understanding the intricate interplay of metal-accumulating plants with their rhizosphere microbiome is an important step toward the application and optimization of phytoremediation. We compared the effects of a "native" and a strongly disturbed (gamma-irradiated) soil microbial communities on cadmium and zinc accumulation by the plant Arabidopsis halleri in soil microcosm experiments. A. halleri accumulated 100% more cadmium and 15% more zinc when grown on the untreated than on the gamma-irradiated soil. Gamma irradiation affected neither plant growth nor the 1 M HCl-extractable metal content of the soil. However, it strongly altered the soil microbial community composition and overall cell numbers. Pyrosequencing of 16S rRNA gene amplicons of DNA extracted from rhizosphere samples of A. halleri identified microbial taxa (Lysobacter, Streptomyces, Agromyces, Nitrospira, "Candidatus Chloracidobacterium") of higher relative sequence abundance in the rhizospheres of A. halleri plants grown on untreated than on gamma-irradiated soil, leading to hypotheses on their potential effect on plant metal uptake. However, further experimental evidence is required, and wherefore we discuss different mechanisms of interaction of A. halleri with its rhizosphere microbiome that might have directly or indirectly affected plant metal accumulation. Deciphering the complex interactions between A. halleri and individual microbial taxa will help to further develop soil metal phytoextraction as an efficient and sustainable remediation strategy. PMID:25595759

  7. Rhizosphere Microbial Community Composition Affects Cadmium and Zinc Uptake by the Metal-Hyperaccumulating Plant Arabidopsis halleri

    PubMed Central

    Muehe, E. Marie; Weigold, Pascal; Adaktylou, Irini J.; Planer-Friedrich, Britta; Kraemer, Ute; Kappler, Andreas

    2015-01-01

    The remediation of metal-contaminated soils by phytoextraction depends on plant growth and plant metal accessibility. Soil microorganisms can affect the accumulation of metals by plants either by directly or indirectly stimulating plant growth and activity or by (im)mobilizing and/or complexing metals. Understanding the intricate interplay of metal-accumulating plants with their rhizosphere microbiome is an important step toward the application and optimization of phytoremediation. We compared the effects of a “native” and a strongly disturbed (gamma-irradiated) soil microbial communities on cadmium and zinc accumulation by the plant Arabidopsis halleri in soil microcosm experiments. A. halleri accumulated 100% more cadmium and 15% more zinc when grown on the untreated than on the gamma-irradiated soil. Gamma irradiation affected neither plant growth nor the 1 M HCl-extractable metal content of the soil. However, it strongly altered the soil microbial community composition and overall cell numbers. Pyrosequencing of 16S rRNA gene amplicons of DNA extracted from rhizosphere samples of A. halleri identified microbial taxa (Lysobacter, Streptomyces, Agromyces, Nitrospira, “Candidatus Chloracidobacterium”) of higher relative sequence abundance in the rhizospheres of A. halleri plants grown on untreated than on gamma-irradiated soil, leading to hypotheses on their potential effect on plant metal uptake. However, further experimental evidence is required, and wherefore we discuss different mechanisms of interaction of A. halleri with its rhizosphere microbiome that might have directly or indirectly affected plant metal accumulation. Deciphering the complex interactions between A. halleri and individual microbial taxa will help to further develop soil metal phytoextraction as an efficient and sustainable remediation strategy. PMID:25595759

  8. The DnaJ-Like Zinc Finger Domain Protein PSA2 Affects Light Acclimation and Chloroplast Development in Arabidopsis thaliana.

    PubMed

    Wang, Yan-Wen; Chen, Si-Ming; Wang, Wei-Jie; Huang, Xing-Qi; Zhou, Chang-Fang; Zhuang, Zhong; Lu, Shan

    2016-01-01

    The biosynthesis of chlorophylls and carotenoids and the assembly of thylakoid membranes are critical for the photoautotrophic growth of plants. Different factors are involved in these two processes. In recent years, members of the DnaJ-like zinc finger domain proteins have been found to take part in the biogenesis and/or the maintenance of plastids. One member of this family of proteins, PSA2, was recently found to localize to the thylakoid lumen and regulate the accumulation of photosystem I. In this study, we report that the silencing of PSA2 in Arabidopsis thaliana resulted in variegated leaves and retarded growth. Although both chlorophylls and total carotenoids decreased in the psa2 mutant, violaxanthin, and zeaxanthin accumulated in the mutant seedlings grown under growth condition. Lower levels of non-photochemical quenching and electron transport rate were also found in the psa2 mutant seedlings under growth condition compared with those of the wild-type plants, indicating an impaired capability to acclimate to normal light irradiance when PSA2 was silenced. Moreover, we also observed an abnormal assembly of grana thylakoids and poorly developed stroma thylakoids in psa2 chloroplasts. Taken together, our results demonstrate that PSA2 is a member of the DnaJ-like zinc finger domain protein family that affects light acclimation and chloroplast development. PMID:27047527

  9. The Evolutionarily Conserved Protein PHOTOSYNTHESIS AFFECTED MUTANT71 Is Required for Efficient Manganese Uptake at the Thylakoid Membrane in Arabidopsis.

    PubMed

    Schneider, Anja; Steinberger, Iris; Herdean, Andrei; Gandini, Chiara; Eisenhut, Marion; Kurz, Samantha; Morper, Anna; Hoecker, Natalie; Rühle, Thilo; Labs, Mathias; Flügge, Ulf-Ingo; Geimer, Stefan; Schmidt, Sidsel Birkelund; Husted, Søren; Weber, Andreas P M; Spetea, Cornelia; Leister, Dario

    2016-04-01

    In plants, algae, and cyanobacteria, photosystem II (PSII) catalyzes the light-driven oxidation of water. The oxygen-evolving complex of PSII is a Mn4CaO5 cluster embedded in a well-defined protein environment in the thylakoid membrane. However, transport of manganese and calcium into the thylakoid lumen remains poorly understood. Here, we show that Arabidopsis thaliana PHOTOSYNTHESIS AFFECTED MUTANT71 (PAM71) is an integral thylakoid membrane protein involved in Mn(2+) and Ca(2+) homeostasis in chloroplasts. This protein is required for normal operation of the oxygen-evolving complex (as evidenced by oxygen evolution rates) and for manganese incorporation. Manganese binding to PSII was severely reduced in pam71 thylakoids, particularly in PSII supercomplexes. In cation partitioning assays with intact chloroplasts, Mn(2+) and Ca(2+) ions were differently sequestered in pam71, with Ca(2+) enriched in pam71 thylakoids relative to the wild type. The changes in Ca(2+) homeostasis were accompanied by an increased contribution of the transmembrane electrical potential to the proton motive force across the thylakoid membrane. PSII activity in pam71 plants and the corresponding Chlamydomonas reinhardtii mutant cgld1 was restored by supplementation with Mn(2+), but not Ca(2+) Furthermore, PAM71 suppressed the Mn(2+)-sensitive phenotype of the yeast mutant Δpmr1 Therefore, PAM71 presumably functions in Mn(2+) uptake into thylakoids to ensure optimal PSII performance. PMID:27020959

  10. The DnaJ-Like Zinc Finger Domain Protein PSA2 Affects Light Acclimation and Chloroplast Development in Arabidopsis thaliana

    PubMed Central

    Wang, Yan-Wen; Chen, Si-Ming; Wang, Wei-Jie; Huang, Xing-Qi; Zhou, Chang-Fang; Zhuang, Zhong; Lu, Shan

    2016-01-01

    The biosynthesis of chlorophylls and carotenoids and the assembly of thylakoid membranes are critical for the photoautotrophic growth of plants. Different factors are involved in these two processes. In recent years, members of the DnaJ-like zinc finger domain proteins have been found to take part in the biogenesis and/or the maintenance of plastids. One member of this family of proteins, PSA2, was recently found to localize to the thylakoid lumen and regulate the accumulation of photosystem I. In this study, we report that the silencing of PSA2 in Arabidopsis thaliana resulted in variegated leaves and retarded growth. Although both chlorophylls and total carotenoids decreased in the psa2 mutant, violaxanthin, and zeaxanthin accumulated in the mutant seedlings grown under growth condition. Lower levels of non-photochemical quenching and electron transport rate were also found in the psa2 mutant seedlings under growth condition compared with those of the wild-type plants, indicating an impaired capability to acclimate to normal light irradiance when PSA2 was silenced. Moreover, we also observed an abnormal assembly of grana thylakoids and poorly developed stroma thylakoids in psa2 chloroplasts. Taken together, our results demonstrate that PSA2 is a member of the DnaJ-like zinc finger domain protein family that affects light acclimation and chloroplast development. PMID:27047527

  11. Potato tuber expression of Arabidopsis WRINKLED1 increase triacylglycerol and membrane lipids while affecting central carbohydrate metabolism.

    PubMed

    Hofvander, Per; Ischebeck, Till; Turesson, Helle; Kushwaha, Sandeep K; Feussner, Ivo; Carlsson, Anders S; Andersson, Mariette

    2016-09-01

    Tuber and root crops virtually exclusively accumulate storage products in the form of carbohydrates. An exception is yellow nutsedge (Cyperus esculentus) in which tubers have the capacity to store starch and triacylglycerols (TAG) in roughly equal amounts. This suggests that a tuber crop can efficiently handle accumulation of energy dense oil. From a nutritional as well as economic aspect, it would be of interest to utilize the high yield capacity of tuber or root crops for oil accumulation similar to yellow nutsedge. The transcription factor WRINKLED1 from Arabidopsis thaliana, which in seed embryos induce fatty acid synthesis, has been shown to be a major factor for oil accumulation. WRINKLED1 was expressed in potato (Solanum tuberosum) tubers to explore whether this factor could impact tuber metabolism. This study shows that a WRINKLED1 transcription factor could induce triacylglycerol accumulation in tubers of transformed potato plants grown in field (up to 12 nmol TAG/mg dry weight, 1% of dry weight) together with a large increase in polar membrane lipids. The changes in metabolism further affected starch accumulation and composition concomitant with massive increases in sugar content. PMID:26914183

  12. Plasma membrane lipid–protein interactions affect signaling processes in sterol-biosynthesis mutants in Arabidopsis thaliana

    PubMed Central

    Zauber, Henrik; Burgos, Asdrubal; Garapati, Prashanth; Schulze, Waltraud X.

    2014-01-01

    The plasma membrane is an important organelle providing structure, signaling and transport as major biological functions. Being composed of lipids and proteins with different physicochemical properties, the biological functions of membranes depend on specific protein–protein and protein–lipid interactions. Interactions of proteins with their specific sterol and lipid environment were shown to be important factors for protein recruitment into sub-compartmental structures of the plasma membrane. System-wide implications of altered endogenous sterol levels for membrane functions in living cells were not studied in higher plant cells. In particular, little is known how alterations in membrane sterol composition affect protein and lipid organization and interaction within membranes. Here, we conducted a comparative analysis of the plasma membrane protein and lipid composition in Arabidopsis sterol-biosynthesis mutants smt1 and ugt80A2;B1. smt1 shows general alterations in sterol composition while ugt80A2;B1 is significantly impaired in sterol glycosylation. By systematically analyzing different cellular fractions and combining proteomic with lipidomic data we were able to reveal contrasting alterations in lipid–protein interactions in both mutants, with resulting differential changes in plasma membrane signaling status. PMID:24672530

  13. Synergistic action of histone acetyltransferase GCN5 and receptor CLAVATA1 negatively affects ethylene responses in Arabidopsis thaliana.

    PubMed

    Poulios, Stylianos; Vlachonasios, Konstantinos E

    2016-02-01

    GENERAL CONTROL NON-REPRESSIBLE 5 (GCN5) is a histone acetyltransferase (HAT) and the catalytic subunit of several multicomponent HAT complexes that acetylate lysine residues of histone H3. Mutants in AtGCN5 display pleiotropic developmental defects including aberrant meristem function. Shoot apical meristem (SAM) maintenance is regulated by CLAVATA1 (CLV1), a receptor kinase that controls the size of the shoot and floral meristems. Upon activation through CLV3 binding, CLV1 signals to the transcription factor WUSCHEL (WUS), restricting WUS expression and thus the meristem size. We hypothesized that GCN5 and CLV1 act together to affect SAM function. Using genetic and molecular approaches, we generated and characterized clv gcn5 mutants. Surprisingly, the clv1-1 gcn5-1 double mutant exhibited constitutive ethylene responses, suggesting that GCN5 and CLV signaling act synergistically to inhibit ethylene responses in Arabidopsis. This genetic and molecular interaction was mediated by ETHYLENE INSENSITIVE 3/ EIN3-LIKE1 (EIN3/EIL1) transcription factors. Our data suggest that signals from the CLV transduction pathway reach the GCN5-containing complexes in the nucleus and alter the histone acetylation status of ethylene-responsive genes, thus translating the CLV information to transcriptional activity and uncovering a link between histone acetylation and SAM maintenance in the complex mode of ethylene signaling. PMID:26596766

  14. Novel Genes Affecting the Interaction between the Cabbage Whitefly and Arabidopsis Uncovered by Genome-Wide Association Mapping

    PubMed Central

    Broekgaarden, Colette; Bucher, Johan; Bac-Molenaar, Johanna; Keurentjes, Joost J. B.; Kruijer, Willem; Voorrips, Roeland E.; Vosman, Ben

    2015-01-01

    Plants have evolved a variety of ways to defend themselves against biotic attackers. This has resulted in the presence of substantial variation in defense mechanisms among plants, even within a species. Genome-wide association (GWA) mapping is a useful tool to study the genetic architecture of traits, but has so far only had limited exploitation in studies of plant defense. Here, we study the genetic architecture of defense against the phloem-feeding insect cabbage whitefly (Aleyrodes proletella) in Arabidopsis thaliana. We determined whitefly performance, i.e. the survival and reproduction of whitefly females, on 360 worldwide selected natural accessions and subsequently performed GWA mapping using 214,051 SNPs. Substantial variation for whitefly adult survival and oviposition rate (number of eggs laid per female per day) was observed between the accessions. We identified 39 candidate SNPs for either whitefly adult survival or oviposition rate, all with relatively small effects, underpinning the complex architecture of defense traits. Among the corresponding candidate genes, i.e. genes in linkage disequilibrium (LD) with candidate SNPs, none have previously been identified as a gene playing a role in the interaction between plants and phloem-feeding insects. Whitefly performance on knock-out mutants of a number of candidate genes was significantly affected, validating the potential of GWA mapping for novel gene discovery in plant-insect interactions. Our results show that GWA analysis is a very useful tool to gain insight into the genetic architecture of plant defense against herbivorous insects, i.e. we identified and validated several genes affecting whitefly performance that have not previously been related to plant defense against herbivorous insects. PMID:26699853

  15. Project Ice Storm: Prenatal Maternal Stress Affects Cognitive and Linguistic Functioning in 5 1/2-Year-Old Children

    ERIC Educational Resources Information Center

    Laplante, David P.; Brunet, Alain; Schmitz, Norbert; Ciampi, Antonio; King, Suzanne

    2008-01-01

    The study used data from Project Ice Storm to determine the extent to which exposure to prenatal maternal stress due to a natural disaster can explain variance in the intellectual and language performance of offspring at age 5 1/2.

  16. Disruption of AtOCT1, an organic cation transporter gene, affects root development and carnitine-related responses in Arabidopsis.

    PubMed

    Lelandais-Brière, Christine; Jovanovic, Mariana; Torres, Gisèle A M; Perrin, Yolande; Lemoine, Rémi; Corre-Menguy, Fabienne; Hartmann, Caroline

    2007-07-01

    In animals, organic cation/carnitine transporters (OCTs) are involved in homeostasis and distribution of various small endogenous amines (e.g. carnitine, choline) and detoxification of xenobiotics such as nicotine. Here, we describe the characterization of AtOCT1, an Arabidopsis protein that shares most of the conserved features of mammalian plasma membrane OCTs. Transient expression of an AtOCT1::GFP fusion protein in onion epidermal cells and Arabidopsis protoplasts supported localization in the plasmalemma. AtOCT1 functionally complemented the Deltacit2/Deltaagp2p yeast strain that is defective in plasma membrane carnitine transport. Disruption of AtOCT1 in an Arabidopsis oct1-1 knockout mutant affected both the expression of carnitine-related genes and the developmental defects induced by exogenous carnitine. RT-PCR and promoter-uidA fusion analysis showed that AtOCT1 was expressed in vascular tissues of various organs and at sites of lateral root formation. Correlating with this expression pattern, oct1-1 seedlings grown in vitro exhibited a higher degree of root branching than the wild-type, showing that the disruption of AtOCT1 affected root development under certain conditions. PMID:17521409

  17. The GI-CDF module of Arabidopsis affects freezing tolerance and growth as well as flowering.

    PubMed

    Fornara, Fabio; de Montaigu, Amaury; Sánchez-Villarreal, Alfredo; Takahashi, Yasuyuki; Ver Loren van Themaat, Emiel; Huettel, Bruno; Davis, Seth J; Coupland, George

    2015-03-01

    Plants monitor and integrate temperature, photoperiod and light quality signals to respond to continuous changes in their environment. The GIGANTEA (GI) protein is central in diverse signaling pathways, including photoperiodic, sugar and light signaling pathways, stress responses and circadian clock regulation. Previously, GI was shown to activate expression of the key floral regulators CONSTANS (CO) and FLOWERING LOCUS T (FT) by facilitating degradation of a family of CYCLING DOF FACTOR (CDF) transcriptional repressors. However, whether CDFs are implicated in other processes affected by GI remains unclear. We investigated the contribution of the GI-CDF module to traits that depend on GI. Transcriptome profiling indicated that mutations in GI and the CDF genes have antagonistic effects on expression of a wider set of genes than CO and FT, whilst other genes are regulated by GI independently of the CDFs. Detailed expression studies followed by phenotypic assays showed that the CDFs function downstream of GI, influencing responses to freezing temperatures and growth, but are not necessary for proper clock function. Thus GI-mediated regulation of CDFs contributes to several processes in addition to flowering, but is not implicated in all of the traits influenced by GI. PMID:25600594

  18. Contrasting Roles of the Apoplastic Aspartyl Protease APOPLASTIC, ENHANCED DISEASE SUSCEPTIBILITY1-DEPENDENT1 and LEGUME LECTIN-LIKE PROTEIN1 in Arabidopsis Systemic Acquired Resistance1,2[W

    PubMed Central

    Breitenbach, Heiko H.; Wenig, Marion; Wittek, Finni; Jordá, Lucia; Maldonado-Alconada, Ana M.; Sarioglu, Hakan; Colby, Thomas; Knappe, Claudia; Bichlmeier, Marlies; Pabst, Elisabeth; Mackey, David; Parker, Jane E.; Vlot, A. Corina

    2014-01-01

    Systemic acquired resistance (SAR) is an inducible immune response that depends on ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1). Here, we show that Arabidopsis (Arabidopsis thaliana) EDS1 is required for both SAR signal generation in primary infected leaves and SAR signal perception in systemic uninfected tissues. In contrast to SAR signal generation, local resistance remains intact in eds1 mutant plants in response to Pseudomonas syringae delivering the effector protein AvrRpm1. We utilized the SAR-specific phenotype of the eds1 mutant to identify new SAR regulatory proteins in plants conditionally expressing AvrRpm1. Comparative proteomic analysis of apoplast-enriched extracts from AvrRpm1-expressing wild-type and eds1 mutant plants led to the identification of 12 APOPLASTIC, EDS1-DEPENDENT (AED) proteins. The genes encoding AED1, a predicted aspartyl protease, and another AED, LEGUME LECTIN-LIKE PROTEIN1 (LLP1), were induced locally and systemically during SAR signaling and locally by salicylic acid (SA) or its functional analog, benzo 1,2,3-thiadiazole-7-carbothioic acid S-methyl ester. Because conditional overaccumulation of AED1-hemagglutinin inhibited SA-induced resistance and SAR but not local resistance, the data suggest that AED1 is part of a homeostatic feedback mechanism regulating systemic immunity. In llp1 mutant plants, SAR was compromised, whereas the local resistance that is normally associated with EDS1 and SA as well as responses to exogenous SA appeared largely unaffected. Together, these data indicate that LLP1 promotes systemic rather than local immunity, possibly in parallel with SA. Our analysis reveals new positive and negative components of SAR and reinforces the notion that SAR represents a distinct phase of plant immunity beyond local resistance. PMID:24755512

  19. TRICHOME BIREFRINGENCE-LIKE27 affects aluminum sensitivity by modulating the O-acetylation of xyloglucan and aluminum-binding capacity in Arabidopsis.

    PubMed

    Zhu, Xiao Fang; Sun, Ying; Zhang, Bao Cai; Mansoori, Nasim; Wan, Jiang Xue; Liu, Yu; Wang, Zhi Wei; Shi, Yuan Zhi; Zhou, Yi Hua; Zheng, Shao Jian

    2014-09-01

    Xyloglucan (XyG) has been reported to contribute to the aluminum (Al)-binding capacity of the cell wall in Arabidopsis (Arabidopsis thaliana). However, the influence of O-acetylation of XyG, accomplished by the putative O-acetyltransferase TRICHOME BIREFRINGENCE-LIKE27 (TBL27 [AXY4]), on its Al-binding capacity is not known. In this study, we found that the two corresponding TBL27 mutants, axy4-1 and axy4-3, were more Al sensitive than wild-type Columbia-0 plants. TBL27 was expressed in roots as well as in leaves, stems, flowers, and siliques. Upon Al treatment, even within 30 min, TBL27 transcript accumulation was strongly down-regulated. The mutants axy4-1 and axy4-3 accumulated significantly more Al in the root and wall, which could not be correlated with pectin content or pectin methylesterase activity, as no difference in the mutants was observed compared with the wild type when exposed to Al stress. The increased Al accumulation in the wall of the mutants was found to be in the hemicellulose fraction. While the total sugar content of the hemicellulose fraction did not change, the O-acetylation level of XyG was reduced by Al treatment. Taken together, we conclude that modulation of the O-acetylation level of XyG influences the Al sensitivity in Arabidopsis by affecting the Al-binding capacity in the hemicellulose. PMID:25006026

  20. Xyloglucan Endotransglucosylase-Hydrolase17 Interacts with Xyloglucan Endotransglucosylase-Hydrolase31 to Confer Xyloglucan Endotransglucosylase Action and Affect Aluminum Sensitivity in Arabidopsis.

    PubMed

    Zhu, Xiao Fang; Wan, Jiang Xue; Sun, Ying; Shi, Yuan Zhi; Braam, Janet; Li, Gui Xin; Zheng, Shao Jian

    2014-06-19

    Previously, we reported that although the Arabidopsis (Arabidopsis thaliana) Xyloglucan Endotransglucosylase-Hydrolase31 (XTH31) has predominately xyloglucan endohydrolase activity in vitro, loss of XTH31 results in remarkably reduced in vivo xyloglucan endotransglucosylase (XET) action and enhanced Al resistance. Here, we report that XTH17, predicted to have XET activity, binds XTH31 in yeast (Saccharomyces cerevisiae) two-hybrid and coimmunoprecipitations assays and that this interaction may be required for XTH17 XET activity in planta. XTH17 and XTH31 may be colocalized in plant cells because tagged XTH17 fusion proteins, like XTH31 fusion proteins, appear to target to the plasma membrane. XTH17 expression, like that of XTH31, was substantially reduced in the presence of aluminum (Al), even at concentrations as low as 10 µm for 24 h or 25 µm for just 30 min. Agrobacterium tumefaciens-mediated transfer DNA insertion mutant of XTH17, xth17, showed low XET action and had moderately shorter roots than the wild type but was more Al resistant than the wild type. Similar to xth31, xth17 had low hemicellulose content and retained less Al in the cell wall. These data suggest a model whereby XTH17 and XTH31 may exist as a dimer at the plasma membrane to confer in vivo XET action, which modulates cell wall Al-binding capacity and thereby affects Al sensitivity in Arabidopsis. PMID:24948835

  1. A New Mutation, hap1-2, Reveals a C Terminal Domain Function in AtMago Protein and Its Biological Effects in Male Gametophyte Development in Arabidopsis thaliana.

    PubMed

    Cilano, Kevin; Mazanek, Zachary; Khan, Mahmuda; Metcalfe, Sarah; Zhang, Xiao-Ning

    2016-01-01

    The exon-exon junction complex (EJC) is a conserved eukaryotic multiprotein complex that examines the quality of and determines the availability of messenger RNAs (mRNAs) posttranscriptionally. Four proteins, MAGO, Y14, eIF4AIII and BTZ, function as core components of the EJC. The mechanisms of their interactions and the biological indications of these interactions are still poorly understood in plants. A new mutation, hap1-2. leads to premature pollen death and a reduced seed production in Arabidopsis. This mutation introduces a viable truncated transcript AtMagoΔC. This truncation abolishes the interaction between AtMago and AtY14 in vitro, but not the interaction between AtMago and AteIF4AIII. In addition to a strong nuclear presence of AtMago, both AtMago and AtMagoΔC exhibit processing-body (P-body) localization. This indicates that AtMagoΔC may replace AtMago in the EJC when aberrant transcripts are to be degraded. When introducing an NMD mutation, upf3-1, into the existing HAP1/hap1-2 mutant, plants showed a severely reduced fertility. However, the change of splicing pattern of a subset of SR protein transcripts is mostly correlated with the sr45-1 and upf3-1 mutations, not the hap1-2 mutation. These results imply that the C terminal domain (CTD) of AtMago is required for the AtMago-AtY14 heterodimerization during EJC assembly, UPF3-mediated NMD pathway and the AtMago-AtY14 heterodimerization work synergistically to regulate male gametophyte development in plants. PMID:26867216

  2. A New Mutation, hap1-2, Reveals a C Terminal Domain Function in AtMago Protein and Its Biological Effects in Male Gametophyte Development in Arabidopsis thaliana

    PubMed Central

    Cilano, Kevin; Mazanek, Zachary; Khan, Mahmuda; Metcalfe, Sarah; Zhang, Xiao-Ning

    2016-01-01

    The exon-exon junction complex (EJC) is a conserved eukaryotic multiprotein complex that examines the quality of and determines the availability of messenger RNAs (mRNAs) posttranscriptionally. Four proteins, MAGO, Y14, eIF4AIII and BTZ, function as core components of the EJC. The mechanisms of their interactions and the biological indications of these interactions are still poorly understood in plants. A new mutation, hap1-2. leads to premature pollen death and a reduced seed production in Arabidopsis. This mutation introduces a viable truncated transcript AtMagoΔC. This truncation abolishes the interaction between AtMago and AtY14 in vitro, but not the interaction between AtMago and AteIF4AIII. In addition to a strong nuclear presence of AtMago, both AtMago and AtMagoΔC exhibit processing-body (P-body) localization. This indicates that AtMagoΔC may replace AtMago in the EJC when aberrant transcripts are to be degraded. When introducing an NMD mutation, upf3-1, into the existing HAP1/hap1-2 mutant, plants showed a severely reduced fertility. However, the change of splicing pattern of a subset of SR protein transcripts is mostly correlated with the sr45-1 and upf3-1 mutations, not the hap1-2 mutation. These results imply that the C terminal domain (CTD) of AtMago is required for the AtMago-AtY14 heterodimerization during EJC assembly, UPF3-mediated NMD pathway and the AtMago-AtY14 heterodimerization work synergistically to regulate male gametophyte development in plants. PMID:26867216

  3. Mutation of either G box or I box sequences profoundly affects expression from the Arabidopsis rbcS-1A promoter.

    PubMed Central

    Donald, R G; Cashmore, A R

    1990-01-01

    A deletion analysis of the Arabidopsis thaliana rbcS-1A promoter defined a 196 bp region (-320 to -125) sufficient to confer light-regulated expression on a heterologous Arabidopsis alcohol dehydrogenase (Adh) reporter gene in transgenic Nicotiana tabacum (tobacco) leaves. This region, which contains DNA sequences I, G and GT boxes, with homology to other ribulose-1,5-bisphosphate carboxylase small subunit (RBCS) gene promoter sequences, directed expression independent of orientation and relative position in the Adh promoter. Site-specific mutagenesis of these conserved sequences and subsequent expression analysis in transgenic tobacco showed that both G box and I box mutations in the context of the full (-1700 to +21) rbcS-1A promoter substantially reduced the expression of Adh and beta-glucuronidase (GUS) reporter genes. The G box has previously been shown to specifically bind in vitro a factor isolated from nuclear extracts of tomato and Arabidopsis. This factor (GBF) is distinct from the factor GT-1 which binds to adjacent GT boxes in the pea rbcS-3A promoter. Multiple mutations in putative Arabidopsis rbcS-1A promoter GT boxes had no pronounced affect on expression, possibly due to a redundancy of these sites. Experiments in which rbcS-1A promoter fragments were fused to truncated 35S CaMV (cauliflower mosaic virus) promoter--GUS reporter constructs showed that cis-acting CaMV promoter elements could partially restore expression to G-box-mutated rbcS-1A sequences. Images Fig. 1. Fig. 2. Fig. 4. Fig. 5. Fig. 6. PMID:2347304

  4. The 73 kD Subunit of the Cleavage and Polyadenylation Specificity Factor (CPSF) Complex Affects Reproductive Development in Arabidopsis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cleavage and polyadenylation specificity factor (CPSF) is an important multi-subunit component of the mRNA 3’-end processing apparatus in eukaryotes. We have identified the Arabidopsis CPSF complex that involves five protein subunits named AtCPSF160, AtCPSF100, AtCPSF73-I, AtCPSF73-II and AtCPSF30....

  5. Deficiency in phylloquinone (vitamin K1) methylation affects prenyl quinone distribution, photosystem I abundance, and anthocyanin accumulation in the Arabidopsis AtmenG mutant.

    PubMed

    Lohmann, Antje; Schöttler, Mark Aurel; Bréhélin, Claire; Kessler, Felix; Bock, Ralph; Cahoon, Edgar B; Dörmann, Peter

    2006-12-29

    Phylloquinone (vitamin K(1)) is synthesized in cyanobacteria and in chloroplasts of plants, where it serves as electron carrier of photosystem I. The last step of phylloquinone synthesis in cyanobacteria is the methylation of 2-phytyl-1,4-naphthoquinone by the menG gene product. Here, we report that the uncharacterized Arabidopsis gene At1g23360, which shows sequence similarity to menG, functionally complements the Synechocystis menG mutant. An Arabidopsis mutant, AtmenG, carrying a T-DNA insertion in the gene At1g23360 is devoid of phylloquinone, but contains an increased amount of 2-phytyl-1,4-naphthoquinone. Phylloquinone and 2-phytyl-1,4-naphthoquinone in thylakoid membranes of wild type and AtmenG, respectively, predominantly localize to photosystem I, whereas excess amounts of prenyl quinones are stored in plastoglobules. Photosystem I reaction centers are decreased in AtmenG plants under high light, as revealed by immunoblot and spectroscopic measurements. Anthocyanin accumulation and chalcone synthase (CHS1) transcription are affected during high light exposure, indicating that alterations in photosynthesis in AtmenG affect gene expression in the nucleus. Photosystem II quantum yield is decreased under high light. Therefore, the loss of phylloquinone methylation affects photosystem I stability or turnover, and the limitation in functional photosystem I complexes results in overreduction of photosystem II under high light. PMID:17082184

  6. Region-Specific Disruption of Adenylate Cyclase Type 1 Gene Differentially Affects Somatosensorimotor Behaviors in Mice1,2,3

    PubMed Central

    Arakawa, Hiroyuki; Akkentli, Fatih

    2014-01-01

    Abstract Cover Figure Region-specific adenylyl cyclase 1 (AC1) loss of function differentially affects both patterning and sensorimotor behaviors in mice. AC1 is expressed at all levels of the somatosensory pathway and plays a major role in refinement and patterning of topographic sensory maps. Cortex-specific AC1 loss of function (CxAC1KO mice) does not affect barrel patterning and activation of specific barrels corresponding to stimulated whiskers and does not impair sensorimotor behaviors. While global (AC1KO) and thalamus-specific (ThAC1KO) AC1 loss of function leads to absence of barrel patterns, selective whisker stimulation activates topographically aligned cortical loci. Despite functional topography of the whisker-barrel cortex, sensorimotor and social behaviors are impaired, indicating the importance of patterning of topographical sensory maps in the neocortex. Adenylate cyclase type I (AC1) is primarily, and, abundantly, expressed in the brain. Intracellular calcium/calmodulin increases regulate AC1 in an activity-dependent manner. Upon stimulation, AC1 produces cAMP and it is involved in the patterning and the refinement of neural circuits. In mice, spontaneous mutations or targeted deletion of the Adcy1 gene, which encodes AC1, resulted in neuronal pattern formation defects. Neural modules in the primary somatosensory (SI) cortex, the barrels, which represent the topographic distribution of the whiskers on the snout, failed to form (Welker et al., 1996; Abdel-Majid et al., 1998). Cortex- or thalamus-specific Adcy1 deletions led to different cortical pattern phenotypes, with thalamus-specific disruption phenotype being more severe (Iwasato et al., 2008; Suzuki et al., 2013). Despite the absence of barrels in the “barrelless”/Adcy1 null mice, thalamocortical terminal bouton density and activation of cortical zones following whisker stimulation were roughly topographic (Abdel-Majid et al., 1998; Gheorghita et al., 2006). To what extent does patterning

  7. Region-Specific Disruption of Adenylate Cyclase Type 1 Gene Differentially Affects Somatosensorimotor Behaviors in Mice(1,2,3).

    PubMed

    Arakawa, Hiroyuki; Akkentli, Fatih; Erzurumlu, Reha S

    2014-01-01

    Cover FigureRegion-specific adenylyl cyclase 1 (AC1) loss of function differentially affects both patterning and sensorimotor behaviors in mice. AC1 is expressed at all levels of the somatosensory pathway and plays a major role in refinement and patterning of topographic sensory maps. Cortex-specific AC1 loss of function (CxAC1KO mice) does not affect barrel patterning and activation of specific barrels corresponding to stimulated whiskers and does not impair sensorimotor behaviors. While global (AC1KO) and thalamus-specific (ThAC1KO) AC1 loss of function leads to absence of barrel patterns, selective whisker stimulation activates topographically aligned cortical loci. Despite functional topography of the whisker-barrel cortex, sensorimotor and social behaviors are impaired, indicating the importance of patterning of topographical sensory maps in the neocortex. Adenylate cyclase type I (AC1) is primarily, and, abundantly, expressed in the brain. Intracellular calcium/calmodulin increases regulate AC1 in an activity-dependent manner. Upon stimulation, AC1 produces cAMP and it is involved in the patterning and the refinement of neural circuits. In mice, spontaneous mutations or targeted deletion of the Adcy1 gene, which encodes AC1, resulted in neuronal pattern formation defects. Neural modules in the primary somatosensory (SI) cortex, the barrels, which represent the topographic distribution of the whiskers on the snout, failed to form (Welker et al., 1996; Abdel-Majid et al., 1998). Cortex- or thalamus-specific Adcy1 deletions led to different cortical pattern phenotypes, with thalamus-specific disruption phenotype being more severe (Iwasato et al., 2008; Suzuki et al., 2013). Despite the absence of barrels in the "barrelless"/Adcy1 null mice, thalamocortical terminal bouton density and activation of cortical zones following whisker stimulation were roughly topographic (Abdel-Majid et al., 1998; Gheorghita et al., 2006). To what extent does patterning of the

  8. The Arabidopsis mitogen-activated protein kinase phosphatase PP2C5 affects seed germination, stomatal aperture, and abscisic acid-inducible gene expression.

    PubMed

    Brock, Anita K; Willmann, Roland; Kolb, Dagmar; Grefen, Laure; Lajunen, Heini M; Bethke, Gerit; Lee, Justin; Nürnberger, Thorsten; Gust, Andrea A

    2010-07-01

    Abscisic acid (ABA) is an important phytohormone regulating various cellular processes in plants, including stomatal opening and seed germination. Although protein phosphorylation via mitogen-activated protein kinases (MAPKs) has been suggested to be important in ABA signaling, the corresponding phosphatases are largely unknown. Here, we show that a member of the Protein Phosphatase 2C (PP2C) family in Arabidopsis (Arabidopsis thaliana), PP2C5, is acting as a MAPK phosphatase. The PP2C5 protein colocalizes and directly interacts with stress-induced MPK3, MPK4, and MPK6, predominantly in the nucleus. Importantly, altered PP2C5 levels affect MAPK activation. Whereas Arabidopsis plants depleted of PP2C5 show an enhanced ABA-induced activation of MPK3 and MPK6, ectopic expression of PP2C5 in tobacco (Nicotiana benthamiana) resulted in the opposite effect, with the two MAPKs salicylic acid-induced protein kinase and wound-induced protein kinase not being activated any longer after ABA treatment. Moreover, depletion of PP2C5, whose gene expression itself is affected by ABA treatment, resulted in altered ABA responses. Loss-of-function mutation in PP2C5 or AP2C1, a close PP2C5 homolog, resulted in an increased stomatal aperture under normal growth conditions and a partial ABA-insensitive phenotype in seed germination that was most prominent in the pp2c5 ap2c1 double mutant line. In addition, the response of ABA-inducible genes such as ABI1, ABI2, RD29A, and Erd10 was reduced in the mutant plants. Thus, we suggest that PP2C5 acts as a MAPK phosphatase that positively regulates seed germination, stomatal closure, and ABA-inducible gene expression. PMID:20488890

  9. The DUF579 domain containing proteins IRX15 and IRX15-L affect xylan synthesis in Arabidopsis.

    PubMed

    Jensen, Jacob K; Kim, Hoon; Cocuron, Jean-Christophe; Orler, Robert; Ralph, John; Wilkerson, Curtis G

    2011-05-01

    Xylan is the principal hemicellulose in the secondary cell walls of eudicots and in the primary and secondary cell walls of grasses and cereals. The biosynthesis of this important cell wall component has yet to be fully determined although a number of proteins have been shown to be required for xylan synthesis. To discover new genes involved in xylan biosynthesis we explored the psyllium (Plantago ovata Forsk) seed mucilaginous layer through EST profiling. This tissue synthesizes large amounts of a complex heteroxylan over a short period of time. By comparing abundant transcripts in this tissue with abundant transcripts specifically present during secondary cell wall formation in Arabidopsis thaliana, where glucuronoxylan biosynthesis is pronounced, we identified two Arabidopsis genes likely involved in xylan biosynthesis. These genes encode proteins containing a Domain of Unknown Function (DUF) 579 and were designated IRREGULAR XYLEM (IRX) 15 and IRX15-LIKE (IRX15-L). We obtained Arabidopsis T-DNA knockout lines for the two genes and analyzed their lower stems for changes in neutral monosaccharide composition. No changes were observed in each of these mutants, although the irx15 irx15-L double mutant displayed a moderate reduction in stem xylose. Further characterization of the irx15 irx15-L mutant revealed irregular secondary cell wall margins in fiber cells and a lower xylan degree of polymerization. Through these studies we conclude that IRX15 and IRX15-L function in a redundant manner and are involved in xylan biosynthesis. PMID:21288268

  10. Alternative Splicing-Mediated Targeting of the Arabidopsis GLUTAMATE RECEPTOR3.5 to Mitochondria Affects Organelle Morphology1

    PubMed Central

    Teardo, Enrico; Carraretto, Luca; De Bortoli, Sara; Costa, Alex; Behera, Smrutisanjita; Wagner, Richard; Lo Schiavo, Fiorella; Szabo, Ildiko

    2015-01-01

    Since the discovery of 20 genes encoding for putative ionotropic glutamate receptors in the Arabidopsis (Arabidopsis thaliana) genome, there has been considerable interest in uncovering their physiological functions. For many of these receptors, neither their channel formation and/or physiological roles nor their localization within the plant cells is known. Here, we provide, to our knowledge, new information about in vivo protein localization and give insight into the biological roles of the so-far uncharacterized Arabidopsis GLUTAMATE RECEPTOR3.5 (AtGLR3.5), a member of subfamily 3 of plant glutamate receptors. Using the pGREAT vector designed for the expression of fusion proteins in plants, we show that a splicing variant of AtGLR3.5 targets the inner mitochondrial membrane, while the other variant localizes to chloroplasts. Mitochondria of knockout or silenced plants showed a strikingly altered ultrastructure, lack of cristae, and swelling. Furthermore, using a genetically encoded mitochondria-targeted calcium probe, we measured a slightly reduced mitochondrial calcium uptake capacity in the knockout mutant. These observations indicate a functional expression of AtGLR3.5 in this organelle. Furthermore, AtGLR3.5-less mutant plants undergo anticipated senescence. Our data thus represent, to our knowledge, the first evidence of splicing-regulated organellar targeting of a plant ion channel and identify the first cation channel in plant mitochondria from a molecular point of view. PMID:25367859

  11. Arabidopsis NMD3 Is Required for Nuclear Export of 60S Ribosomal Subunits and Affects Secondary Cell Wall Thickening

    PubMed Central

    Chen, Mei-Qin; Zhang, Ai-Hong; Zhang, Quan; Zhang, Bao-Cai; Nan, Jie; Li, Xia; Liu, Na; Qu, Hong; Lu, Cong-Ming; Sudmorgen; Zhou, Yi-Hua; Xu, Zhi-Hong; Bai, Shu-Nong

    2012-01-01

    NMD3 is required for nuclear export of the 60S ribosomal subunit in yeast and vertebrate cells, but no corresponding function of NMD3 has been reported in plants. Here we report that Arabidopsis thaliana NMD3 (AtNMD3) showed a similar function in the nuclear export of the 60S ribosomal subunit. Interference with AtNMD3 function by overexpressing a truncated dominant negative form of the protein lacking the nuclear export signal sequence caused retainment of the 60S ribosomal subunits in the nuclei. More interestingly, the transgenic Arabidopsis with dominant negative interference of AtNMD3 function showed a striking failure of secondary cell wall thickening, consistent with the altered expression of related genes and composition of cell wall components. Observation of a significant decrease of rough endoplasmic reticulum (RER) in the differentiating interfascicular fiber cells of the transgenic plant stems suggested a link between the defective nuclear export of 60S ribosomal subunits and the abnormal formation of the secondary cell wall. These findings not only clarified the evolutionary conservation of NMD3 functions in the nuclear export of 60S ribosomal subunits in yeast, animals and plants, but also revealed a new facet of the regulatory mechanism underlying secondary cell wall thickening in Arabidopsis. This new facet is that the nuclear export of 60S ribosomal subunits and the formation of RER may play regulatory roles in coordinating protein synthesis in cytoplasm and transcription in nuclei. PMID:22558264

  12. MicroRNA844-Guided Downregulation of Cytidinephosphate Diacylglycerol Synthase3 (CDS3) mRNA Affects the Response of Arabidopsis thaliana to Bacteria and Fungi.

    PubMed

    Lee, Hwa Jung; Park, Young Ju; Kwak, Kyung Jin; Kim, Donghyun; Park, June Hyun; Lim, Jae Yun; Shin, Chanseok; Yang, Kwang-Yeol; Kang, Hunseung

    2015-08-01

    Despite the fact that a large number of miRNA sequences have been determined in diverse plant species, reports demonstrating the functional roles of miRNAs in the plant response to pathogens are severely limited. Here, Arabidopsis thaliana miRNA844 (miR844) was investigated for its functional role in the defense response to diverse pathogens. Transgenic Arabidopsis plants overexpressing miR844 (35S::miR844) displayed much more severe disease symptoms than the wild-type plants when challenged with the bacterium Pseudomonas syringae pv. tomato DC3000 or the fungus Botrytis cinerea. By contrast, a loss-of-function mir844 mutant showed an enhanced resistance against the pathogens. Although no cleavage was observed at the predicted cleavage site of the putative target mRNA, cytidinephosphate diacylglycerol synthase3 (CDS3), cleavage was observed at 6, 12, 21, or 52 bases upstream of the predicted cleavage site of CDS3 mRNA, and the level of CDS3 mRNA was downregulated by the overexpression of miR844, implying that miR844 influences CDS3 transcript level. To further confirm that the miR844-mediated defense response was due to the decrease in CDS3 mRNA level, the disease response of a CDS3 loss-of-function mutant was analyzed upon pathogen challenge. Increased susceptibility of both cds3 mutant and 35S::miR844 plants to pathogens confirmed that miR844 affected the defense response by downregulating CDS3 mRNA. The expression of miR844 was decreased, and the CDS3 transcript level increased upon pathogen challenge. Taken together, these results provide evidence that downregulation of miR844 and a concomitant increase in CDS3 expression is a defensive response of Arabidopsis to bacteria and fungi. PMID:25775269

  13. The Transcript and Metabolite Networks Affected by the Two Clades of Arabidopsis Glucosinolate Biosynthesis Regulators1[W

    PubMed Central

    Malitsky, Sergey; Blum, Eyal; Less, Hadar; Venger, Ilya; Elbaz, Moshe; Morin, Shai; Eshed, Yuval; Aharoni, Asaph

    2008-01-01

    In this study, transcriptomics and metabolomics data were integrated in order to examine the regulation of glucosinolate (GS) biosynthesis in Arabidopsis (Arabidopsis thaliana) and its interface with pathways of primary metabolism. Our genetic material for analyses were transgenic plants overexpressing members of two clades of genes (ALTERED TRYPTOPHAN REGULATION1 [ATR1]-like and MYB28-like) that regulate the aliphatic and indole GS biosynthetic pathways (AGs and IGs, respectively). We show that activity of these regulators is not restricted to the metabolic space surrounding GS biosynthesis but is tightly linked to more distal metabolic networks of primary metabolism. This suggests that with similarity to the regulators we have investigated here, other factors controlling pathways of secondary metabolism might also control core pathways of central metabolism. The relatively broad view of transcripts and metabolites altered in transgenic plants overexpressing the different factors underlined novel links of GS metabolism to additional metabolic pathways, including those of jasmonic acid, folate, benzoic acid, and various phenylpropanoids. It also revealed transcriptional and metabolic hubs in the “distal” network of metabolic pathways supplying precursors to GS biosynthesis and that overexpression of the ATR1-like clade genes has a much broader effect on the metabolism of indolic compounds than described previously. While the reciprocal, negative cross talk between the methionine and tryptophan pathways that generate GSs in Arabidopsis has been suggested previously, we now show that it is not restricted to AGs and IGs but includes additional metabolites, such as the phytoalexin camalexin. Combining the profiling data of transgenic lines with gene expression correlation analysis allowed us to propose a model of how the balance in the metabolic network is maintained by the GS biosynthesis regulators. It appears that ATR1/MYB34 is an important mediator between the

  14. A null mutation in the first enzyme of flavonoid biosynthesis does not affect male fertility in Arabidopsis.

    PubMed Central

    Burbulis, I E; Iacobucci, M; Shirley, B W

    1996-01-01

    Flavonoids are a major class of secondary metabolites that serves a multitude of functions in higher plants, including a recently discovered role in male fertility. Surprisingly, Arabidopsis plants deficient in flavonoid biosynthesis appear to be fully fertile. Using RNA gel blot analysis and polymerase chain reaction-based assays, we have shown that a mutation at the 3' splice acceptor site in the Arabidopsis chalcone synthase gene completely disrupts synthesis of the active form of the enzyme. We also confirmed that this enzyme, which catalyzes the first step of flavonoid biosynthesis, is encoded by a single-copy gene. HPLC analysis of whole flowers and stamens was used to show that plants homozygous for the splice site mutation are completely devoid of flavonoids. This work provides compelling evidence that despite the high levels of these compounds in the pollen of most plant species, flavonoids are not universally required for fertility. The role of flavonoids in plant reproduction may therefore offer an example of convergent functional evolution in secondary metabolism. PMID:8672888

  15. A Genetic Screen for Mutations Affecting Cell Division in the Arabidopsis thaliana Embryo Identifies Seven Loci Required for Cytokinesis

    PubMed Central

    Gillmor, C. Stewart; Roeder, Adrienne H. K.; Sieber, Patrick; Somerville, Chris; Lukowitz, Wolfgang

    2016-01-01

    Cytokinesis in plants involves the formation of unique cellular structures such as the phragmoplast and the cell plate, both of which are required to divide the cell after nuclear division. In order to isolate genes that are involved in de novo cell wall formation, we performed a large-scale, microscope-based screen for Arabidopsis mutants that severely impair cytokinesis in the embryo. We recovered 35 mutations that form abnormally enlarged cells with multiple, often polyploid nuclei and incomplete cell walls. These mutants represent seven genes, four of which have previously been implicated in phragmoplast or cell plate function. Mutations in two loci show strongly reduced transmission through the haploid gametophytic generation. Molecular cloning of both corresponding genes reveals that one is represented by hypomorphic alleles of the kinesin-5 gene RADIALLY SWOLLEN 7 (homologous to tobacco kinesin-related protein TKRP125), and that the other gene corresponds to the Arabidopsis FUSED ortholog TWO-IN-ONE (originally identified based on its function in pollen development). No mutations that completely abolish the formation of cross walls in diploid cells were found. Our results support the idea that cytokinesis in the diploid and haploid generations involve similar mechanisms. PMID:26745275

  16. MES Buffer Affects Arabidopsis Root Apex Zonation and Root Growth by Suppressing Superoxide Generation in Root Apex

    PubMed Central

    Kagenishi, Tomoko; Yokawa, Ken; Baluška, František

    2016-01-01

    In plants, growth of roots and root hairs is regulated by the fine cellular control of pH and reactive oxygen species (ROS). MES, 2-(N-morpholino)ethanesulfonic acid as one of the Good’s buffers has broadly been used for buffering medium, and it is thought to suit for plant growth with the concentration at 0.1% (w/v) because the buffer capacity of MES ranging pH 5.5–7.0 (for Arabidopsis, pH 5.8). However, many reports have shown that, in nature, roots require different pH values on the surface of specific root apex zones, namely meristem, transition zone, and elongation zone. Despite the fact that roots always grow on a media containing buffer molecule, little is known about impact of MES on root growth. Here, we have checked the effects of different concentrations of MES buffer using growing roots of Arabidopsis thaliana. Our results show that 1% of MES significantly inhibited root growth, the number of root hairs and length of meristem, whereas 0.1% promoted root growth and root apex area (region spanning from the root tip up to the transition zone). Furthermore, superoxide generation in root apex disappeared at 1% of MES. These results suggest that MES disturbs normal root morphogenesis by changing the ROS homeostasis in root apex. PMID:26925066

  17. Genome Sequencing of Arabidopsis abp1-5 Reveals Second-Site Mutations That May Affect Phenotypes.

    PubMed

    Enders, Tara A; Oh, Sookyung; Yang, Zhenbiao; Montgomery, Beronda L; Strader, Lucia C

    2015-07-01

    Auxin regulates numerous aspects of plant growth and development. For many years, investigating roles for AUXIN BINDING PROTEIN1 (ABP1) in auxin response was impeded by the reported embryo lethality of mutants defective in ABP1. However, identification of a viable Arabidopsis thaliana TILLING mutant defective in the ABP1 auxin binding pocket (abp1-5) allowed inroads into understanding ABP1 function. During our own studies with abp1-5, we observed growth phenotypes segregating independently of the ABP1 lesion, leading us to sequence the genome of the abp1-5 line described previously. We found that the abp1-5 line we sequenced contains over 8000 single nucleotide polymorphisms in addition to the ABP1 mutation and that at least some of these mutations may originate from the Arabidopsis Wassilewskija accession. Furthermore, a phyB null allele in the abp1-5 background is likely causative for the long hypocotyl phenotype previously attributed to disrupted ABP1 function. Our findings complicate the interpretation of abp1-5 phenotypes for which no complementation test was conducted. Our findings on abp1-5 also provide a cautionary tale illustrating the need to use multiple alleles or complementation lines when attributing roles to a gene product. PMID:26106149

  18. The Arabidopsis immutans Mutation Affects Plastid Differentiation and the Morphogenesis of White and Green Sectors in Variegated Plants1

    PubMed Central

    Aluru, Maneesha R.; Bae, Hanhong; Wu, Dongying; Rodermel, Steven R.

    2001-01-01

    The immutans (im) variegation mutant of Arabidopsis has green and white leaf sectors due to the action of a nuclear recessive gene, IMMUTANS (IM). This gene encodes the IM protein, which is a chloroplast homolog of the mitochondrial alternative oxidase. Because the white sectors of im accumulate the noncolored carotenoid, phytoene, IM likely serves as a redox component in phytoene desaturation. In this paper, we show that IM has a global impact on plant growth and development and is required for the differentiation of multiple plastid types, including chloroplasts, amyloplasts, and etioplasts. IM promoter activity and IM mRNAs are also expressed ubiquitously in Arabidopsis. IM transcript levels correlate with carotenoid accumulation in some, but not all, tissues. This suggests that IM function is not limited to carotenogenesis. Leaf anatomy is radically altered in the green and white sectors of im: Mesophyll cell sizes are dramatically enlarged in the green sectors and palisade cells fail to expand in the white sectors. The green im sectors also have significantly higher than normal rates of O2 evolution and elevated chlorophyll a/b ratios, typical of those found in “sun” leaves. We conclude that the changes in structure and photosynthetic function of the green leaf sectors are part of an adaptive mechanism that attempts to compensate for a lack of photosynthesis in the white leaf sectors, while maximizing the ability of the plant to avoid photodamage. PMID:11553735

  19. MES Buffer Affects Arabidopsis Root Apex Zonation and Root Growth by Suppressing Superoxide Generation in Root Apex.

    PubMed

    Kagenishi, Tomoko; Yokawa, Ken; Baluška, František

    2016-01-01

    In plants, growth of roots and root hairs is regulated by the fine cellular control of pH and reactive oxygen species (ROS). MES, 2-(N-morpholino)ethanesulfonic acid as one of the Good's buffers has broadly been used for buffering medium, and it is thought to suit for plant growth with the concentration at 0.1% (w/v) because the buffer capacity of MES ranging pH 5.5-7.0 (for Arabidopsis, pH 5.8). However, many reports have shown that, in nature, roots require different pH values on the surface of specific root apex zones, namely meristem, transition zone, and elongation zone. Despite the fact that roots always grow on a media containing buffer molecule, little is known about impact of MES on root growth. Here, we have checked the effects of different concentrations of MES buffer using growing roots of Arabidopsis thaliana. Our results show that 1% of MES significantly inhibited root growth, the number of root hairs and length of meristem, whereas 0.1% promoted root growth and root apex area (region spanning from the root tip up to the transition zone). Furthermore, superoxide generation in root apex disappeared at 1% of MES. These results suggest that MES disturbs normal root morphogenesis by changing the ROS homeostasis in root apex. PMID:26925066

  20. Overexpression of AtPTPA in Arabidopsis increases protein phosphatase 2A activity by promoting holoenzyme formation and ABA negatively affects holoenzyme formation

    PubMed Central

    Chen, Jian; Zhu, Xunlu; Shen, Guoxin; Zhang, Hong

    2015-01-01

    AtPTPA is a critical regulator for the holoenzyme assembling of protein phosphatase 2A (PP2A) in Arabidopsis. Characterization of AtPTPA improves our understanding of the function and regulation of PP2A in eukaryotes. Further analysis of AtPTPA-overexpressing plants indicates that AtPTPA increases PP2A activity by promoting PP2A's AC dimer formation, thereby holoenzyme assembling. Plant hormone abscisic acid (ABA) reduces PP2A enzyme activity by negatively affects PP2A's AC dimer formation. Therefore, AtPTPA is a positive factor that promotes PP2A holoenzyme assembly, and ABA is a negative factor that prevents PP2A holoenzyme assembly. PMID:26633567

  1. Neutron Radiation Affects the Expression of Genes Involved in the Response to Auxin, Senescence and Oxidative Stress in Arabidopsis

    NASA Astrophysics Data System (ADS)

    Fortunati, A.; Tassone, P.; Migliaccio, F.

    2008-06-01

    Researches were conducted on the effect of neutron radiation on the expression of genes auxin activated or connected with the process of senescence in Arabidopsis plants. The research was done by applying the real-time polymerase chain reaction (PCR) technique. The results indicated that the auxin response factors (ARFs) genes are clearly downregulated, whereas the indolacetic acid-induced (Aux/IAAs) genes in some cases were upregulated. By contrast in the mutants for auxin transport aux1 and eir1 the ARFs genes were upregulated. In addition, both in the wildtype and mutants, some already known genes activated by stress and senescence were significantly upregulated. On the basis of these researches we conclude that the process of senescence induced by irradiation is, at least in part, controlled by the physiology of the hormone auxin.

  2. Chlorophyll Synthase under Epigenetic Surveillance Is Critical for Vitamin E Synthesis, and Altered Expression Affects Tocopherol Levels in Arabidopsis.

    PubMed

    Zhang, Chunyu; Zhang, Wei; Ren, Guodong; Li, Delin; Cahoon, Rebecca E; Chen, Ming; Zhou, Yongming; Yu, Bin; Cahoon, Edgar B

    2015-08-01

    Chlorophyll synthase catalyzes the final step in chlorophyll biosynthesis: the esterification of chlorophyllide with either geranylgeranyl diphosphate or phytyl diphosphate (PDP). Recent studies have pointed to the involvement of chlorophyll-linked reduction of geranylgeranyl by geranylgeranyl reductase as a major pathway for the synthesis of the PDP precursor of tocopherols. This indirect pathway of PDP synthesis suggests a key role of chlorophyll synthase in tocopherol production to generate the geranylgeranyl-chlorophyll substrate for geranylgeranyl reductase. In this study, contributions of chlorophyll synthase to tocopherol formation in Arabidopsis (Arabidopsis thaliana) were explored by disrupting and altering expression of the corresponding gene CHLOROPHYLL SYNTHASE (CHLSYN; At3g51820). Leaves from the homozygous chlysyn1-1 null mutant were nearly devoid of tocopherols, whereas seeds contained only approximately 25% of wild-type tocopherol levels. Leaves of RNA interference lines with partial suppression of CHLSYN displayed marked reductions in chlorophyll but up to a 2-fold increase in tocopherol concentrations. Cauliflower mosaic virus35S-mediated overexpression of CHLSYN unexpectedly caused a cosuppression phenotype at high frequencies accompanied by strongly reduced chlorophyll content and increased tocopherol levels. This phenotype and the associated detection of CHLSYN-derived small interfering RNAs were reversed with CHLSYN overexpression in rna-directed rna polymerase6 (rdr6), which is defective in RNA-dependent RNA polymerase6, a key enzyme in sense transgene-induced small interfering RNA production. CHLSYN overexpression in rdr6 had little effect on chlorophyll content but resulted in up to a 30% reduction in tocopherol levels in leaves. These findings show that altered CHLSYN expression impacts tocopherol levels and also, show a strong epigenetic surveillance of CHLSYN to control chlorophyll and tocopherol synthesis. PMID:26048882

  3. Modifications of Sphingolipid Content Affect Tolerance to Hemibiotrophic and Necrotrophic Pathogens by Modulating Plant Defense Responses in Arabidopsis.

    PubMed

    Magnin-Robert, Maryline; Le Bourse, Doriane; Markham, Jonathan; Dorey, Stéphan; Clément, Christophe; Baillieul, Fabienne; Dhondt-Cordelier, Sandrine

    2015-11-01

    Sphingolipids are emerging as second messengers in programmed cell death and plant defense mechanisms. However, their role in plant defense is far from being understood, especially against necrotrophic pathogens. Sphingolipidomics and plant defense responses during pathogenic infection were evaluated in the mutant of long-chain base phosphate (LCB-P) lyase, encoded by the dihydrosphingosine-1-phosphate lyase1 (AtDPL1) gene and regulating long-chain base/LCB-P homeostasis. Atdpl1 mutants exhibit tolerance to the necrotrophic fungus Botrytis cinerea but susceptibility to the hemibiotrophic bacterium Pseudomonas syringae pv tomato (Pst). Here, a direct comparison of sphingolipid profiles in Arabidopsis (Arabidopsis thaliana) during infection with pathogens differing in lifestyles is described. In contrast to long-chain bases (dihydrosphingosine [d18:0] and 4,8-sphingadienine [d18:2]), hydroxyceramide and LCB-P (phytosphingosine-1-phosphate [t18:0-P] and 4-hydroxy-8-sphingenine-1-phosphate [t18:1-P]) levels are higher in Atdpl1-1 than in wild-type plants in response to B. cinerea. Following Pst infection, t18:0-P accumulates more strongly in Atdpl1-1 than in wild-type plants. Moreover, d18:0 and t18:0-P appear as key players in Pst- and B. cinerea-induced cell death and reactive oxygen species accumulation. Salicylic acid levels are similar in both types of plants, independent of the pathogen. In addition, salicylic acid-dependent gene expression is similar in both types of B. cinerea-infected plants but is repressed in Atdpl1-1 after treatment with Pst. Infection with both pathogens triggers higher jasmonic acid, jasmonoyl-isoleucine accumulation, and jasmonic acid-dependent gene expression in Atdpl1-1 mutants. Our results demonstrate that sphingolipids play an important role in plant defense, especially toward necrotrophic pathogens, and highlight a novel connection between the jasmonate signaling pathway, cell death, and sphingolipids. PMID:26378098

  4. Modifications of Sphingolipid Content Affect Tolerance to Hemibiotrophic and Necrotrophic Pathogens by Modulating Plant Defense Responses in Arabidopsis1[OPEN

    PubMed Central

    Magnin-Robert, Maryline; Le Bourse, Doriane; Markham, Jonathan; Dorey, Stéphan; Clément, Christophe; Baillieul, Fabienne; Dhondt-Cordelier, Sandrine

    2015-01-01

    Sphingolipids are emerging as second messengers in programmed cell death and plant defense mechanisms. However, their role in plant defense is far from being understood, especially against necrotrophic pathogens. Sphingolipidomics and plant defense responses during pathogenic infection were evaluated in the mutant of long-chain base phosphate (LCB-P) lyase, encoded by the dihydrosphingosine-1-phosphate lyase1 (AtDPL1) gene and regulating long-chain base/LCB-P homeostasis. Atdpl1 mutants exhibit tolerance to the necrotrophic fungus Botrytis cinerea but susceptibility to the hemibiotrophic bacterium Pseudomonas syringae pv tomato (Pst). Here, a direct comparison of sphingolipid profiles in Arabidopsis (Arabidopsis thaliana) during infection with pathogens differing in lifestyles is described. In contrast to long-chain bases (dihydrosphingosine [d18:0] and 4,8-sphingadienine [d18:2]), hydroxyceramide and LCB-P (phytosphingosine-1-phosphate [t18:0-P] and 4-hydroxy-8-sphingenine-1-phosphate [t18:1-P]) levels are higher in Atdpl1-1 than in wild-type plants in response to B. cinerea. Following Pst infection, t18:0-P accumulates more strongly in Atdpl1-1 than in wild-type plants. Moreover, d18:0 and t18:0-P appear as key players in Pst- and B. cinerea-induced cell death and reactive oxygen species accumulation. Salicylic acid levels are similar in both types of plants, independent of the pathogen. In addition, salicylic acid-dependent gene expression is similar in both types of B. cinerea-infected plants but is repressed in Atdpl1-1 after treatment with Pst. Infection with both pathogens triggers higher jasmonic acid, jasmonoyl-isoleucine accumulation, and jasmonic acid-dependent gene expression in Atdpl1-1 mutants. Our results demonstrate that sphingolipids play an important role in plant defense, especially toward necrotrophic pathogens, and highlight a novel connection between the jasmonate signaling pathway, cell death, and sphingolipids. PMID:26378098

  5. Lack of cytochrome c in Arabidopsis decreases stability of Complex IV and modifies redox metabolism without affecting Complexes I and III.

    PubMed

    Welchen, Elina; Hildebrandt, Tatjana M; Lewejohann, Dagmar; Gonzalez, Daniel H; Braun, Hans-Peter

    2012-07-01

    We studied the role of cytochrome c (CYTc), which mediates electron transfer between Complexes III and IV, in cellular events related with mitochondrial respiration, plant development and redox homeostasis. We analyzed single and double homozygous mutants in both CYTc-encoding genes from Arabidopsis: CYTC-1 and CYTC-2. While individual mutants were similar to wild-type, knock-out of both genes produced an arrest of embryo development, showing that CYTc function is essential at early stages of plant development. Mutants in which CYTc levels were extremely reduced respective to wild-type had smaller rosettes with a pronounced decrease in parenchymatic cell size and an overall delay in development. Mitochondria from these mutants had lower respiration rates and a relative increase in alternative respiration. Furthermore, the decrease in CYTc severely affected the activity and the amount of Complex IV, without affecting Complexes I and III. Reactive oxygen species levels were reduced in these mutants, which showed induction of genes encoding antioxidant enzymes. Ascorbic acid levels were not affected, suggesting that a small amount of CYTc is enough to support its normal synthesis. We postulate that, in addition to its role as an electron carrier between Complexes III and IV, CYTc influences Complex IV levels in plants, probably reflecting a role of this protein in Complex IV stability. This double function of CYTc most likely explains why it is essential for plant survival. PMID:22551905

  6. Disruption of cellulose synthesis by 2,6-dichlorobenzonitrile affects the structure of the cytoskeleton and cell wall construction in Arabidopsis.

    PubMed

    Peng, L; Zhang, L; Cheng, X; Fan, L-S; Hao, H-Q

    2013-03-01

    Cellulose is the major component of plant cell walls and is an important source of industrial raw material. Although cellulose biosynthesis is one of the most important biochemical processes in plant biology, the regulatory mechanisms of cellulose synthesis are still unclear. Here, we report that 2,6-dichlorobenzonitrile (DCB), an inhibitor of cellulose synthesis, inhibits Arabidopsis root development in a dose- and time-dependent manner. When treated with DCB, the plant cell wall showed altered cellulose distribution and intensity, as shown by calcofluor white and S4B staining. Moreover, pectin deposition was reduced in the presence of DCB when immunostained with the monoclonal antibody JIM5, which was raised against pectin epitopes. This result was confirmed using Fourier transform infrared (FTIR) analysis. Confocal microscopy revealed that the organisation of the microtubule cytoskeleton was significantly disrupted in the presence of low concentrations of DCB, whereas the actin cytoskeleton only showed changes with the application of high DCB concentrations. In addition, the subcellular dynamics of Golgi bodies labelled with N-ST-YFP and TGN labelled with VHA-a1-GFP were both partially blocked by DCB. Transmission electron microscopy indicated that the cell wall structure was affected by DCB, as were the Golgi bodies. Scanning electron microscopy showed changes in the organisation of cellulose microfibrils. These results suggest that the inhibition of cellulose synthesis by DCB not only induced changes in the chemical composition of the root cell wall and cytoskeleton structure, but also changed the distribution of cellulose microfibrils, implying that cellulose plays an important role in root development in Arabidopsis. PMID:22759307

  7. Antiphase Light and Temperature Cycles Affect PHYTOCHROME B-Controlled Ethylene Sensitivity and Biosynthesis, Limiting Leaf Movement and Growth of Arabidopsis1[C][W

    PubMed Central

    Bours, Ralph; van Zanten, Martijn; Pierik, Ronald; Bouwmeester, Harro; van der Krol, Alexander

    2013-01-01

    In the natural environment, days are generally warmer than the night, resulting in a positive day/night temperature difference (+DIF). Plants have adapted to these conditions, and when exposed to antiphase light and temperature cycles (cold photoperiod/warm night [−DIF]), most species exhibit reduced elongation growth. To study the physiological mechanism of how light and temperature cycles affect plant growth, we used infrared imaging to dissect growth dynamics under +DIF and −DIF in the model plant Arabidopsis (Arabidopsis thaliana). We found that −DIF altered leaf growth patterns, decreasing the amplitude and delaying the phase of leaf movement. Ethylene application restored leaf growth in −DIF conditions, and constitutive ethylene signaling mutants maintain robust leaf movement amplitudes under −DIF, indicating that ethylene signaling becomes limiting under these conditions. In response to −DIF, the phase of ethylene emission advanced 2 h, but total ethylene emission was not reduced. However, expression analysis on members of the 1-aminocyclopropane-1-carboxylic acid (ACC) synthase ethylene biosynthesis gene family showed that ACS2 activity is specifically suppressed in the petiole region under −DIF conditions. Indeed, petioles of plants under −DIF had reduced ACC content, and application of ACC to the petiole restored leaf growth patterns. Moreover, acs2 mutants displayed reduced leaf movement under +DIF, similar to wild-type plants under −DIF. In addition, we demonstrate that the photoreceptor PHYTOCHROME B restricts ethylene biosynthesis and constrains the −DIF-induced phase shift in rhythmic growth. Our findings provide a mechanistic insight into how fluctuating temperature cycles regulate plant growth. PMID:23979970

  8. Functional characterization of mutants affected in the carbonic anhydrase domain of the respiratory complex I in Arabidopsis thaliana.

    PubMed

    Soto, Débora; Córdoba, Juan Pablo; Villarreal, Fernando; Bartoli, Carlos; Schmitz, Jessica; Maurino, Veronica G; Braun, Hans Peter; Pagnussat, Gabriela C; Zabaleta, Eduardo

    2015-09-01

    The NADH-ubiquinone oxidoreductase complex (complex I) (EC 1.6.5.3) is the main entrance site of electrons into the respiratory chain. In a variety of eukaryotic organisms, except animals and fungi (Opisthokonta), it contains an extra domain comprising trimers of putative γ-carbonic anhydrases, named the CA domain, which has been proposed to be essential for assembly of complex I. However, its physiological role in plants is not fully understood. Here, we report that Arabidopsis mutants defective in two CA subunits show an altered photorespiratory phenotype. Mutants grown in ambient air show growth retardation compared to wild-type plants, a feature that is reversed by cultivating plants in a high-CO2 atmosphere. Moreover, under photorespiratory conditions, carbon assimilation is diminished and glycine accumulates, suggesting an imbalance with respect to photorespiration. Additionally, transcript levels of specific CA subunits are reduced in plants grown under non-photorespiratory conditions. Taken together, these results suggest that the CA domain of plant complex I contributes to sustaining efficient photosynthesis under ambient (photorespiratory) conditions. PMID:26148112

  9. Mutations in Arabidopsis thaliana genes involved in the tryptophan biosynthesis pathway affect root waving on tilted agar surfaces

    NASA Technical Reports Server (NTRS)

    Rutherford, R.; Gallois, P.; Masson, P. H.

    1998-01-01

    Arabidopsis thaliana roots grow in a wavy pattern upon a slanted surface. A novel mutation in the anthranilate synthase alpha 1 (ASA1) gene, named trp5-2wvc1, and mutations in the tryptophan synthase alpha and beta 1 genes (trp3-1 and trp2-1, respectively) confer a compressed root wave phenotype on tilted agar surfaces. When trp5-2wvc1 seedlings are grown on media supplemented with anthranilate metabolites, their roots wave like wild type. Genetic and pharmacological experiments argue that the compressed root wave phenotypes of trp5-2wvc1, trp2-1 and trp3-1 seedlings are not due to reduced IAA biosynthetic potential, but rather to a deficiency in L-tryptophan (L-Trp), or in a L-Trp derivative. Although the roots of 7-day-old seedlings possess higher concentrations of free L-Trp than the shoot as a whole, trp5-2wvc1 mutants show no detectable alteration in L-Trp levels in either tissue type, suggesting that a very localized shortage of L-Trp, or of a L-Trp-derived compound, is responsible for the observed phenotype.

  10. The irregular xylem 2 mutant is an allele of korrigan that affects the secondary cell wall of Arabidopsis thaliana.

    PubMed

    Szyjanowicz, Pio M J; McKinnon, Iain; Taylor, Neil G; Gardiner, John; Jarvis, Mike C; Turner, Simon R

    2004-03-01

    The irregular xylem 2 (irx2) mutant of Arabidopsis thaliana exhibits a cellulose deficiency in the secondary cell wall, which is brought about by a point mutation in the KORRIGAN (KOR) beta,1-4 endoglucanase (beta,1-4 EGase) gene. Measurement of the total crystalline cellulose in the inflorescence stem indicates that the irx2 mutant contains approximately 30% of the level present in the wild type (WT). Fourier-Transform Infra Red (FTIR) analysis, however, indicates that there is no decrease in cellulose in primary cell walls of the cortical and epidermal cells of the stem. KOR expression is correlated with cellulose synthesis and is highly expressed in cells synthesising a secondary cell wall. Co-precipitation experiments, using either an epitope-tagged form of KOR or IRX3 (AtCesA7), suggest that KOR is not an integral part of the cellulose synthase complex. These data are supported by immunolocalisation of KOR that suggests that KOR does not localise to sites of secondary cell wall deposition in the developing xylem. The defect in irx2 plant is consistent with a role for KOR in the later stages of secondary cell wall formation, suggesting a role in processing of the growing microfibrils or release of the cellulose synthase complex. PMID:14871312

  11. Alteration of seed fatty acid composition by an ethyl methanesulfonate-induced mutation in Arabidopsis thaliana affecting diacylglycerol acyltransferase activity.

    PubMed Central

    Katavic, V; Reed, D W; Taylor, D C; Giblin, E M; Barton, D L; Zou, J; Mackenzie, S L; Covello, P S; Kunst, L

    1995-01-01

    In characterizing the enzymes involved in the formation of very long-chain fatty acids (VLCFAs) in the Brassicaceae, we have generated a series of mutants of Arabidopsis thaliana that have reduced VLCFA content. Here we report the characterization of a seed lipid mutant, AS11, which, in comparison to wild type (WT), has reduced levels of 20:1 and 18:1 and accumulates 18:3 as the major fatty acid in triacylglycerols. Proportions of 18:2 remain similar to WT. Genetic analyses indicate that the fatty acid phenotype is caused by a semidominant mutation in a single nuclear gene, designated TAG1, located on chromosome 2. Biochemical analyses have shown that the AS11 phenotype is not due to a deficiency in the capacity to elongate 18:1 or to an increase in the relative delta 15 or delta 12 desaturase activities. Indeed, the ratio of desaturase/elongase activities measured in vitro is virtually identical in developing WT and AS11 seed homogenates. Rather, the fatty acid phenotype of AS11 is the result of reduced diacylglycerol acyltransferase activity throughout development, such that triacylglycerol biosynthesis is reduced. This leads to a reduction in 20:1 biosynthesis during seed development, leaving more 18:1 available for desaturation. Thus, we have demonstrated that changes to triacylglycerol biosynthesis can result in dramatic changes in fatty acid composition and, in particular, in the accumulation of VLCFAs in seed storage lipids. PMID:7784510

  12. TR-DB: an open-access database of compounds affecting the ethylene-induced triple response in Arabidopsis.

    PubMed

    Hu, Yuming; Callebert, Pieter; Vandemoortel, Ilse; Nguyen, Long; Audenaert, Dominique; Verschraegen, Luc; Vandenbussche, Filip; Van Der Straeten, Dominique

    2014-02-01

    Small molecules which act as hormone agonists or antagonists represent useful tools in fundamental research and are widely applied in agriculture to control hormone effects. High-throughput screening of large chemical compound libraries has yielded new findings in plant biology, with possible future applications in agriculture and horticulture. To further understand ethylene biosynthesis/signaling and its crosstalk with other hormones, we screened a 12,000 compound chemical library based on an ethylene-related bioassay of dark-grown Arabidopsis thaliana (L.) Heynh. seedlings. From the initial screening, 1313 (∼11%) biologically active small molecules altering the phenotype triggered by the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), were identified. Selection and sorting in classes were based on the angle of curvature of the apical hook, the length and width of the hypocotyl and the root. A MySQL-database was constructed (https://chaos.ugent.be/WE15/) including basic chemical information on the compounds, images illustrating the phenotypes, phenotype descriptions and classification. The research perspectives for different classes of hit compounds will be evaluated, and some general screening tips for customized high-throughput screening and pitfalls will be discussed. PMID:24441765

  13. Nitrogen Source and External Medium pH Interaction Differentially Affects Root and Shoot Metabolism in Arabidopsis

    PubMed Central

    Sarasketa, Asier; González-Moro, M. Begoña; González-Murua, Carmen; Marino, Daniel

    2016-01-01

    Ammonium nutrition often represents an important growth-limiting stress in plants. Some of the symptoms that plants present under ammonium nutrition have been associated with pH deregulation, in fact external medium pH control is known to improve plants ammonium tolerance. However, the way plant cell metabolism adjusts to these changes is not completely understood. Thus, in this work we focused on how Arabidopsis thaliana shoot and root respond to different nutritional regimes by varying the nitrogen source (NO3- and NH4+), concentration (2 and 10 mM) and pH of the external medium (5.7 and 6.7) to gain a deeper understanding of cell metabolic adaptation upon altering these environmental factors. The results obtained evidence changes in the response of ammonium assimilation machinery and of the anaplerotic enzymes associated to Tricarboxylic Acids (TCA) cycle in function of the plant organ, the nitrogen source and the degree of ammonium stress. A greater stress severity at pH 5.7 was related to NH4+ accumulation; this could not be circumvented in spite of the stimulation of glutamine synthetase, glutamate dehydrogenase, and TCA cycle anaplerotic enzymes. Moreover, this study suggests specific functions for different gln and gdh isoforms based on the nutritional regime. Overall, NH4+ accumulation triggering ammonium stress appears to bear no relation to nitrogen assimilation impairment. PMID:26870054

  14. Peri-pubertal administration of 3-nitro-1,2,4-triazol-5-one (NTO) affects reproductive organ development in male but not female Sprague Dawley rats.

    PubMed

    Lent, Emily May; Crouse, Lee C B; Wallace, Shannon M; Carroll, Erica E

    2015-11-01

    Nitrotriazolone (3-nitro-1,2,4-triazol-5-one; NTO) is an insensitive munition that has demonstrated effects on reproductive organs in adult male rats. NTO was administered to male (0, 250, and 500milligrams per kilogram per day (mg/kg-day)) and female (0, 500, and 1000mg/kg-day) Sprague-Dawley rats (15/sex/group) via oral gavage from weaning through post-natal day 53/54 and 42/43, respectively. Age and body mass at vaginal opening (VO) and preputial separation (PPS), as well as all measures of estrous cyclicity were not affected by treatment with NTO. Males treated with NTO exhibited reductions in testis mass associated with tubular degeneration/atrophy. Less pronounced reductions in accessory sex organ masses were also observed in the 500mg/kg-day group. Treatment with NTO did not affect thyroid hormone or testosterone levels. These findings suggest that NTO is not acting as an estrogen or thyroid active compound, but may indicate effects on steroidogenesis and/or direct testicular toxicity. PMID:25962730

  15. Magnitude and Timing of Leaf Damage Affect Seed Production in a Natural Population of Arabidopsis thaliana (Brassicaceae)

    PubMed Central

    Akiyama, Reiko; Ågren, Jon

    2012-01-01

    Background The effect of herbivory on plant fitness varies widely. Understanding the causes of this variation is of considerable interest because of its implications for plant population dynamics and trait evolution. We experimentally defoliated the annual herb Arabidopsis thaliana in a natural population in Sweden to test the hypotheses that (a) plant fitness decreases with increasing damage, (b) tolerance to defoliation is lower before flowering than during flowering, and (c) defoliation before flowering reduces number of seeds more strongly than defoliation during flowering, but the opposite is true for effects on seed size. Methodology/Principal Findings In a first experiment, between 0 and 75% of the leaf area was removed in May from plants that flowered or were about to start flowering. In a second experiment, 0, 25%, or 50% of the leaf area was removed from plants on one of two occasions, in mid April when plants were either in the vegetative rosette or bolting stage, or in mid May when plants were flowering. In the first experiment, seed production was negatively related to leaf area removed, and at the highest damage level, also mean seed size was reduced. In the second experiment, removal of 50% of the leaf area reduced seed production by 60% among plants defoliated early in the season at the vegetative rosettes, and by 22% among plants defoliated early in the season at the bolting stage, but did not reduce seed output of plants defoliated one month later. No seasonal shift in the effect of defoliation on seed size was detected. Conclusions/Significance The results show that leaf damage may reduce the fitness of A. thaliana, and suggest that in this population leaf herbivores feeding on plants before flowering should exert stronger selection on defence traits than those feeding on plants during flowering, given similar damage levels. PMID:22276140

  16. Conserved phosphorylation sites in the activation loop of the Arabidopsis phytosulfokine receptor PSKR1 differentially affect kinase and receptor activity

    PubMed Central

    Hartmann, Jens; Linke, Dennis; Bönniger, Christine; Tholey, Andreas; Sauter, Margret

    2015-01-01

    PSK (phytosulfokine) is a plant peptide hormone perceived by a leucine-rich repeat receptor kinase. Phosphosite mapping of epitope-tagged PSKR1 (phytosulfokine receptor 1) from Arabidopsis thaliana plants identified Ser696 and Ser698 in the JM (juxtamembrane) region and probably Ser886 and/or Ser893 in the AL (activation loop) as in planta phosphorylation sites. In vitro-expressed kinase was autophosphorylated at Ser717 in the JM, and at Ser733, Thr752, Ser783, Ser864, Ser911, Ser958 and Thr998 in the kinase domain. The LC–ESI–MS/MS spectra provided support that up to three sites (Thr890, Ser893 and Thr894) in the AL were likely to be phosphorylated in vitro. These sites are evolutionarily highly conserved in PSK receptors, indicative of a conserved function. Site-directed mutagenesis of the four conserved residues in the activation segment, Thr890, Ser893, Thr894 and Thr899, differentially altered kinase activity in vitro and growth-promoting activity in planta. The T899A and the quadruple-mutated TSTT-A (T890A/S893A/T894A/T899A) mutants were both kinase-inactive, but PSKR1(T899A) retained growth-promoting activity. The T890A and S893A/T894A substitutions diminished kinase activity and growth promotion. We hypothesize that phosphorylation within the AL activates kinase activity and receptor function in a gradual and distinctive manner that may be a means to modulate the PSK response. PMID:26472115

  17. Conserved phosphorylation sites in the activation loop of the Arabidopsis phytosulfokine receptor PSKR1 differentially affect kinase and receptor activity.

    PubMed

    Hartmann, Jens; Linke, Dennis; Bönniger, Christine; Tholey, Andreas; Sauter, Margret

    2015-12-15

    PSK (phytosulfokine) is a plant peptide hormone perceived by a leucine-rich repeat receptor kinase. Phosphosite mapping of epitope-tagged PSKR1 (phytosulfokine receptor 1) from Arabidopsis thaliana plants identified Ser(696) and Ser(698) in the JM (juxtamembrane) region and probably Ser(886) and/or Ser(893) in the AL (activation loop) as in planta phosphorylation sites. In vitro-expressed kinase was autophosphorylated at Ser(717) in the JM, and at Ser(733), Thr(752), Ser(783), Ser(864), Ser(911), Ser(958) and Thr(998) in the kinase domain. The LC-ESI-MS/MS spectra provided support that up to three sites (Thr(890), Ser(893) and Thr(894)) in the AL were likely to be phosphorylated in vitro. These sites are evolutionarily highly conserved in PSK receptors, indicative of a conserved function. Site-directed mutagenesis of the four conserved residues in the activation segment, Thr(890), Ser(893), Thr(894) and Thr(899), differentially altered kinase activity in vitro and growth-promoting activity in planta. The T899A and the quadruple-mutated TSTT-A (T890A/S893A/T894A/T899A) mutants were both kinase-inactive, but PSKR1(T899A) retained growth-promoting activity. The T890A and S893A/T894A substitutions diminished kinase activity and growth promotion. We hypothesize that phosphorylation within the AL activates kinase activity and receptor function in a gradual and distinctive manner that may be a means to modulate the PSK response. PMID:26472115

  18. Overexpression of an Arabidopsis heterogeneous nuclear ribonucleoprotein gene, AtRNP1, affects plant growth and reduces plant tolerance to drought and salt stresses.

    PubMed

    Wang, Zhenyu; Zhao, Xiuyang; Wang, Bing; Liu, Erlong; Chen, Ni; Zhang, Wei; Liu, Heng

    2016-04-01

    Heterogeneous nuclear ribonucleoproteins (hnRNPs) participate in diverse regulations of plant growth and environmental stress responses. In this work, an Arabidopsis hnRNP of unknown function, AtRNP1, was investigated. We found that AtRNP1 gene is highly expressed in rosette and cauline leaves, and slightly induced under drought, salt, osmotic and ABA stresses. AtRNP1 protein is localized to both the nucleus and cytoplasm. We performed homologous overexpression of AtRNP1 and found that the transgenic plants showed shortened root length and plant height, and accelerated flowering. In addition, the transgenic plants also showed reduced tolerance to drought, salt, osmotic and ABA stresses. Further studies revealed that under both normal and stress conditions, the proline contents in the transgenic plants are markedly decreased, associated with reduced expression levels of a proline synthase gene and several stress-responsive genes. These results suggested that the overexpression of AtRNP1 negatively affects plant growth and abiotic stress tolerance. PMID:26923071

  19. A R2R3-MYB transcription factor that is specifically expressed in cotton (Gossypium hirsutum) fibers affects secondary cell wall biosynthesis and deposition in transgenic Arabidopsis.

    PubMed

    Sun, Xiang; Gong, Si-Ying; Nie, Xiao-Ying; Li, Yang; Li, Wen; Huang, Geng-Qing; Li, Xue-Bao

    2015-07-01

    Secondary cell wall (SCW) is an important industrial raw material for pulping, papermaking, construction, lumbering, textiles and potentially for biofuel production. The process of SCW thickening of cotton fibers lays down the cellulose that will constitute the bulk (up to 96%) of the fiber at maturity. In this study, a gene encoding a MYB-domain protein was identified in cotton (Gossypium hirsutum) and designated as GhMYBL1. Quantitative real-time polymerase chain reaction (RT-PCR) analysis revealed that GhMYBL1 was specifically expressed in cotton fibers at the stage of secondary wall deposition. Further analysis indicated that this protein is a R2R3-MYB transcription factor, and is targeted to the cell nucleus. Overexpression of GhMYBL1 in Arabidopsis affected the formation of SCW in the stem xylem of the transgenic plants. The enhanced SCW thickening also occurred in the interfascicular fibers, xylary fibers and vessels of the GhMYBL1-overexpression transgenic plants. The expression of secondary wall-associated genes, such as CesA4, CesA7, CesA8, PAL1, F5H and 4CL1, were upregulated, and consequently, cellulose and lignin biosynthesis were enhanced in the GhMYBL1 transgenic plants. These data suggested that GhMYBL1 may participate in modulating the process of secondary wall biosynthesis and deposition of cotton fibers. PMID:25534543

  20. ABA Is an Essential Signal for Plant Resistance to Pathogens Affecting JA Biosynthesis and the Activation of Defenses in Arabidopsis[W

    PubMed Central

    Adie, Bruce A.T.; Pérez-Pérez, Julián; Pérez-Pérez, Manuel M.; Godoy, Marta; Sánchez-Serrano, José-J.; Schmelz, Eric A.; Solano, Roberto

    2007-01-01

    Analyses of Arabidopsis thaliana defense response to the damping-off oomycete pathogen Pythium irregulare show that resistance to P. irregulare requires a multicomponent defense strategy. Penetration represents a first layer, as indicated by the susceptibility of pen2 mutants, followed by recognition, likely mediated by ERECTA receptor-like kinases. Subsequent signaling of inducible defenses is predominantly mediated by jasmonic acid (JA), with insensitive coi1 mutants showing extreme susceptibility. In contrast with the generally accepted roles of ethylene and salicylic acid cooperating with or antagonizing, respectively, JA in the activation of defenses against necrotrophs, both are required to prevent disease progression, although much less so than JA. Meta-analysis of transcriptome profiles confirmed the predominant role of JA in activation of P. irregulare–induced defenses and uncovered abscisic acid (ABA) as an important regulator of defense gene expression. Analysis of cis-regulatory sequences also revealed an unexpected overrepresentation of ABA response elements in promoters of P. irregulare–responsive genes. Subsequent infections of ABA-related and callose-deficient mutants confirmed the importance of ABA in defense, acting partly through an undescribed mechanism. The results support a model for ABA affecting JA biosynthesis in the activation of defenses against this oomycete. PMID:17513501

  1. Altered xylem-phloem transfer of amino acids affects metabolism and leads to increased seed yield and oil content in Arabidopsis.

    PubMed

    Zhang, Lizhi; Tan, Qiumin; Lee, Raymond; Trethewy, Alexander; Lee, Yong-Hwa; Tegeder, Mechthild

    2010-11-01

    Seed development and nitrogen (N) storage depend on delivery of amino acids to seed sinks. For efficient translocation to seeds, amino acids are loaded into the phloem in source leaves and along the long distance transport pathway through xylem-phloem transfer. We demonstrate that Arabidopsis thaliana AMINO ACID PERMEASE2 (AAP2) localizes to the phloem throughout the plant. AAP2 T-DNA insertion lines showed changes in source-sink translocation of amino acids and a decrease in the amount of seed total N and storage proteins, supporting AAP2 function in phloem loading and amino acid distribution to the embryo. Interestingly, in aap2 seeds, total carbon (C) levels were unchanged, while fatty acid levels were elevated. Moreover, branch and silique numbers per plant and seed yield were strongly increased. This suggests changes in N and C delivery to sinks and subsequent modulations of sink development and seed metabolism. This is supported by tracer experiments, expression studies of genes of N/C transport and metabolism in source and sink, and by phenotypic and metabolite analyses of aap2 plants. Thus, AAP2 is key for xylem to phloem transfer and sink N and C supply; moreover, modifications of N allocation can positively affect C assimilation and source-sink transport and benefit sink development and oil yield. PMID:21075769

  2. Minor Antenna Proteins CP24 and CP26 Affect the Interactions between Photosystem II Subunits and the Electron Transport Rate in Grana Membranes of Arabidopsis[W

    PubMed Central

    de Bianchi, Silvia; Dall'Osto, Luca; Tognon, Giuseppe; Morosinotto, Tomas; Bassi, Roberto

    2008-01-01

    We investigated the function of chlorophyll a/b binding antenna proteins Chlorophyll Protein 26 (CP26) and CP24 in light harvesting and regulation of photosynthesis by isolating Arabidopsis thaliana knockout lines that completely lacked one or both of these proteins. All three mutant lines had a decreased efficiency of energy transfer from trimeric light-harvesting complex II (LHCII) to the reaction center of photosystem II (PSII) due to the physical disconnection of LHCII from PSII and formation of PSII reaction center depleted domains in grana partitions. Photosynthesis was affected in plants lacking CP24 but not in plants lacking CP26: the former mutant had decreased electron transport rates, a lower ΔpH gradient across the grana membranes, reduced capacity for nonphotochemical quenching, and limited growth. Furthermore, the PSII particles of these plants were organized in unusual two-dimensional arrays in the grana membranes. Surprisingly, overall electron transport, nonphotochemical quenching, and growth of the double mutant were restored to wild type. Fluorescence induction kinetics and electron transport measurements at selected steps of the photosynthetic chain suggested that limitation in electron transport was due to restricted electron transport between QA and QB, which retards plastoquinone diffusion. We conclude that CP24 absence alters PSII organization and consequently limits plastoquinone diffusion. PMID:18381925

  3. Minor antenna proteins CP24 and CP26 affect the interactions between photosystem II subunits and the electron transport rate in grana membranes of Arabidopsis.

    PubMed

    de Bianchi, Silvia; Dall'Osto, Luca; Tognon, Giuseppe; Morosinotto, Tomas; Bassi, Roberto

    2008-04-01

    We investigated the function of chlorophyll a/b binding antenna proteins Chlorophyll Protein 26 (CP26) and CP24 in light harvesting and regulation of photosynthesis by isolating Arabidopsis thaliana knockout lines that completely lacked one or both of these proteins. All three mutant lines had a decreased efficiency of energy transfer from trimeric light-harvesting complex II (LHCII) to the reaction center of photosystem II (PSII) due to the physical disconnection of LHCII from PSII and formation of PSII reaction center depleted domains in grana partitions. Photosynthesis was affected in plants lacking CP24 but not in plants lacking CP26: the former mutant had decreased electron transport rates, a lower DeltapH gradient across the grana membranes, reduced capacity for nonphotochemical quenching, and limited growth. Furthermore, the PSII particles of these plants were organized in unusual two-dimensional arrays in the grana membranes. Surprisingly, overall electron transport, nonphotochemical quenching, and growth of the double mutant were restored to wild type. Fluorescence induction kinetics and electron transport measurements at selected steps of the photosynthetic chain suggested that limitation in electron transport was due to restricted electron transport between Q(A) and Q(B), which retards plastoquinone diffusion. We conclude that CP24 absence alters PSII organization and consequently limits plastoquinone diffusion. PMID:18381925

  4. Depletion of the "gamma-type carbonic anhydrase-like" subunits of complex I affects central mitochondrial metabolism in Arabidopsis thaliana.

    PubMed

    Fromm, Steffanie; Göing, Jennifer; Lorenz, Christin; Peterhänsel, Christoph; Braun, Hans-Peter

    2016-01-01

    "Gamma-type carbonic anhydrase-like" (CAL) proteins form part of complex I in plants. Together with "gamma carbonic anhydrase" (CA) proteins they form an extra domain which is attached to the membrane arm of complex I on its matrix exposed side. In Arabidopsis two CAL and three CA proteins are present, termed CAL1, CAL2, CA1, CA2 and CA3. It has been proposed that the carbonic anhydrase domain of complex I is involved in a process mediating efficient recycling of mitochondrial CO2 for photosynthetic carbon fixation which is especially important during growth conditions causing increased photorespiration. Depletion of CAL proteins has been shown to significantly affect plant development and photomorphogenesis. To better understand CAL function in plants we here investigated effects of CAL depletion on the mitochondrial compartment. In mutant lines and cell cultures complex I amount was reduced by 90-95% but levels of complexes III and V were unchanged. At the same time, some of the CA transcripts were less abundant. Proteome analysis of CAL depleted cells revealed significant reduction of complex I subunits as well as proteins associated with photorespiration, but increased amounts of proteins participating in amino acid catabolism and stress response reactions. Developmental delay of the mutants was slightly alleviated if plants were cultivated at high CO2. Profiling of selected metabolites revealed defined changes in intermediates of the citric acid cycle and amino acid catabolism. It is concluded that CAL proteins are essential for complex I assembly and that CAL depletion specifically affects central mitochondrial metabolism. PMID:26482706

  5. COBRA-LIKE2, a Member of the Glycosylphosphatidylinositol-Anchored COBRA-LIKE Family, Plays a Role in Cellulose Deposition in Arabidopsis Seed Coat Mucilage Secretory Cells1,2[OPEN

    PubMed Central

    Ben-Tov, Daniela; Abraham, Yael; Stav, Shira; Thompson, Kevin; Loraine, Ann; Elbaum, Rivka; de Souza, Amancio; Pauly, Markus; Kieber, Joseph J.; Harpaz-Saad, Smadar

    2015-01-01

    Differentiation of the maternally derived seed coat epidermal cells into mucilage secretory cells is a common adaptation in angiosperms. Recent studies identified cellulose as an important component of seed mucilage in various species. Cellulose is deposited as a set of rays that radiate from the seed upon mucilage extrusion, serving to anchor the pectic component of seed mucilage to the seed surface. Using transcriptome data encompassing the course of seed development, we identified COBRA-LIKE2 (COBL2), a member of the glycosylphosphatidylinositol-anchored COBRA-LIKE gene family in Arabidopsis (Arabidopsis thaliana), as coexpressed with other genes involved in cellulose deposition in mucilage secretory cells. Disruption of the COBL2 gene results in substantial reduction in the rays of cellulose present in seed mucilage, along with an increased solubility of the pectic component of the mucilage. Light birefringence demonstrates a substantial decrease in crystalline cellulose deposition into the cellulosic rays of the cobl2 mutants. Moreover, crystalline cellulose deposition into the radial cell walls and the columella appears substantially compromised, as demonstrated by scanning electron microscopy and in situ quantification of light birefringence. Overall, the cobl2 mutants display about 40% reduction in whole-seed crystalline cellulose content compared with the wild type. These data establish that COBL2 plays a role in the deposition of crystalline cellulose into various secondary cell wall structures during seed coat epidermal cell differentiation. PMID:25583925

  6. Light intensity affects chlorophyll synthesis during greening process by metabolite signal from mitochondrial alternative oxidase in Arabidopsis.

    PubMed

    Zhang, Da-Wei; Yuan, Shu; Xu, Fei; Zhu, Feng; Yuan, Ming; Ye, Hua-Xun; Guo, Hong-Qing; Lv, Xin; Yin, Yanhai; Lin, Hong-Hui

    2016-01-01

    Although mitochondrial alternative oxidase (AOX) has been proposed to play essential roles in high light stress tolerance, the effects of AOX on chlorophyll synthesis are unclear. Previous studies indicated that during greening, chlorophyll accumulation was largely delayed in plants whose mitochondrial cyanide-resistant respiration was inhibited by knocking out nuclear encoded AOX gene. Here, we showed that this delay of chlorophyll accumulation was more significant under high light condition. Inhibition of cyanide-resistant respiration was also accompanied by the increase of plastid NADPH/NADP(+) ratio, especially under high light treatment which subsequently blocked the import of multiple plastidial proteins, such as some components of the photosynthetic electron transport chain, the Calvin-Benson cycle enzymes and malate/oxaloacetate shuttle components. Overexpression of AOX1a rescued the aox1a mutant phenotype, including the chlorophyll accumulation during greening and plastidial protein import. It thus suggests that light intensity affects chlorophyll synthesis during greening process by a metabolic signal, the AOX-derived plastidial NADPH/NADP(+) ratio change. Further, our results thus revealed a molecular mechanism of chloroplast-mitochondria interactions. PMID:25158995

  7. Mg-chelatase I subunit 1 and Mg-protoporphyrin IX methyltransferase affect the stomatal aperture in Arabidopsis thaliana.

    PubMed

    Tomiyama, Masakazu; Inoue, Shin-Ichiro; Tsuzuki, Tomo; Soda, Midori; Morimoto, Sayuri; Okigaki, Yukiko; Ohishi, Takaya; Mochizuki, Nobuyoshi; Takahashi, Koji; Kinoshita, Toshinori

    2014-07-01

    To elucidate the molecular mechanisms of stomatal opening and closure, we performed a genetic screen using infrared thermography to isolate stomatal aperture mutants. We identified a mutant designated low temperature with open-stomata 1 (lost1), which exhibited reduced leaf temperature, wider stomatal aperture, and a pale green phenotype. Map-based analysis of the LOST1 locus revealed that the lost1 mutant resulted from a missense mutation in the Mg-chelatase I subunit 1 (CHLI1) gene, which encodes a subunit of the Mg-chelatase complex involved in chlorophyll synthesis. Transformation of the wild-type CHLI1 gene into lost1 complemented all lost1 phenotypes. Stomata in lost1 exhibited a partial ABA-insensitive phenotype similar to that of rtl1, a Mg-chelatase H subunit missense mutant. The Mg-protoporphyrin IX methyltransferase (CHLM) gene encodes a subsequent enzyme in the chlorophyll synthesis pathway. We examined stomatal movement in a CHLM knockdown mutant, chlm, and found that it also exhibited an ABA-insensitive phenotype. However, lost1 and chlm seedlings all showed normal expression of ABA-induced genes, such as RAB18 and RD29B, in response to ABA. These results suggest that the chlorophyll synthesis enzymes, Mg-chelatase complex and CHLM, specifically affect ABA signaling in the control of stomatal aperture and have no effect on ABA-induced gene expression. PMID:24840863

  8. Genome Wide Association Mapping for the Tolerance to the Polyamine Oxidase Inhibitor Guazatine in Arabidopsis thaliana.

    PubMed

    Atanasov, Kostadin E; Barboza-Barquero, Luis; Tiburcio, Antonio F; Alcázar, Rubén

    2016-01-01

    Guazatine is a potent inhibitor of polyamine oxidase (PAO) activity. In agriculture, guazatine is used as non-systemic contact fungicide efficient in the protection of cereals and citrus fruits against disease. The composition of guazatine is complex, mainly constituted by a mixture of synthetic guanidated polyamines (polyaminoguanidines). Here, we have studied the effects from exposure to guazatine in the weed Arabidopsis thaliana. We report that micromolar concentrations of guazatine are sufficient to inhibit growth of Arabidopsis seedlings and induce chlorosis, whereas germination is barely affected. We observed the occurrence of quantitative variation in the response to guazatine between 107 randomly chosen Arabidopsis accessions. This enabled us to undertake genome-wide association (GWA) mapping that identified a locus on chromosome one associated with guazatine tolerance. CHLOROPHYLLASE 1 (CLH1) within this locus was studied as candidate gene, together with its paralog (CLH2). The analysis of independent clh1-2, clh1-3, clh2-3, clh2-2, and double clh1-2 clh2-3 mutant alleles indicated that CLH1 and/or CLH2 loss-of-function or expression down-regulation promote guazatine tolerance in Arabidopsis. We report a natural mechanism by which Arabidopsis populations can overcome toxicity by the fungicide guazatine. PMID:27092150

  9. Genome Wide Association Mapping for the Tolerance to the Polyamine Oxidase Inhibitor Guazatine in Arabidopsis thaliana

    PubMed Central

    Atanasov, Kostadin E.; Barboza-Barquero, Luis; Tiburcio, Antonio F.; Alcázar, Rubén

    2016-01-01

    Guazatine is a potent inhibitor of polyamine oxidase (PAO) activity. In agriculture, guazatine is used as non-systemic contact fungicide efficient in the protection of cereals and citrus fruits against disease. The composition of guazatine is complex, mainly constituted by a mixture of synthetic guanidated polyamines (polyaminoguanidines). Here, we have studied the effects from exposure to guazatine in the weed Arabidopsis thaliana. We report that micromolar concentrations of guazatine are sufficient to inhibit growth of Arabidopsis seedlings and induce chlorosis, whereas germination is barely affected. We observed the occurrence of quantitative variation in the response to guazatine between 107 randomly chosen Arabidopsis accessions. This enabled us to undertake genome-wide association (GWA) mapping that identified a locus on chromosome one associated with guazatine tolerance. CHLOROPHYLLASE 1 (CLH1) within this locus was studied as candidate gene, together with its paralog (CLH2). The analysis of independent clh1-2, clh1-3, clh2-3, clh2-2, and double clh1-2 clh2-3 mutant alleles indicated that CLH1 and/or CLH2 loss-of-function or expression down-regulation promote guazatine tolerance in Arabidopsis. We report a natural mechanism by which Arabidopsis populations can overcome toxicity by the fungicide guazatine. PMID:27092150

  10. AMS-dependent and independent regulation of anther transcriptome and comparison with those affected by other Arabidopsis anther genes

    PubMed Central

    2012-01-01

    Background In flowering plants, the development of male reproductive organs is controlled precisely to achieve successful fertilization and reproduction. Despite the increasing knowledge of genes that contribute to anther development, the regulatory mechanisms controlling this process are still unclear. Results In this study, we analyzed the transcriptome profiles of early anthers of sterile mutants aborted microspores (ams) and found that 1,368 genes were differentially expressed in ams compared to wild type anthers, affecting metabolism, transportation, ubiquitination and stress response. Moreover, the lack of significant enrichment of potential AMS binding sites (E-box) in the promoters of differentially expressed genes suggests both direct and indirect regulation for AMS-dependent regulation of anther transcriptome involving other transcription factors. Combining ams transcriptome profiles with those of two other sterile mutants, spl/nzz and ems1/exs, expression of 3,058 genes were altered in at least one mutant. Our investigation of expression patterns of major transcription factor families, such as bHLH, MYB and MADS, suggested that some closely related homologs of known anther developmental genes might also have similar functions. Additionally, comparison of expression levels of genes in different organs suggested that anther-preferential genes could play important roles in anther development. Conclusion Analysis of ams anther transcriptome and its comparison with those of spl/nzz and ems1/exs anthers uncovered overlapping and distinct sets of regulated genes, including those encoding transcription factors and other proteins. These results support an expanded regulatory network for early anther development, providing a series of hypotheses for future experimentation. PMID:22336428

  11. A JUMONJI Protein with E3 Ligase and Histone H3 Binding Activities Affects Transposon Silencing in Arabidopsis.

    PubMed

    Kabelitz, Tina; Brzezinka, Krzysztof; Friedrich, Thomas; Górka, Michał; Graf, Alexander; Kappel, Christian; Bäurle, Isabel

    2016-05-01

    Transposable elements (TEs) make up a large proportion of eukaryotic genomes. As their mobilization creates genetic variation that threatens genome integrity, TEs are epigenetically silenced through several pathways, and this may spread to neighboring sequences. JUMONJI (JMJ) proteins can function as antisilencing factors and prevent silencing of genes next to TEs Whether TE silencing is counterbalanced by the activity of antisilencing factors is still unclear. Here, we characterize JMJ24 as a regulator of TE silencing. We show that loss of JMJ24 results in increased silencing of the DNA transposon AtMu1c, while overexpression of JMJ24 reduces silencing. JMJ24 has a JumonjiC (JmjC) domain and two RING domains. JMJ24 autoubiquitinates in vitro, demonstrating E3 ligase activity of the RING domain(s). JMJ24-JmjC binds the N-terminal tail of histone H3, and full-length JMJ24 binds histone H3 in vivo. JMJ24 activity is anticorrelated with histone H3 Lys 9 dimethylation (H3K9me2) levels at AtMu1c Double mutant analyses with epigenetic silencing mutants suggest that JMJ24 antagonizes histone H3K9me2 and requires H3K9 methyltransferases for its activity on AtMu1c Genome-wide transcriptome analysis indicates that JMJ24 affects silencing at additional TEs Our results suggest that the JmjC domain of JMJ24 has lost demethylase activity but has been retained as a binding domain for histone H3. This is in line with phylogenetic analyses indicating that JMJ24 (with the mutated JmjC domain) is widely conserved in angiosperms. Taken together, this study assigns a role in TE silencing to a conserved JmjC-domain protein with E3 ligase activity, but no demethylase activity. PMID:26979329

  12. ABA is an essential signal for plant resistance to pathogens affecting JA biosynthesis and the activation of plant defenses in Arabidopsis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plant defense responses have been studied through a limited number of models that may have constrained our view of plant-pathogen interactions. Discovery of new defense mechanisms should be favored by broadening the range of pathogens under study. With this aim, Arabidopsis defense response to the ‘...

  13. Composition and Physiological Function of the Wax Layers Coating Arabidopsis Leaves: β-Amyrin Negatively Affects the Intracuticular Water Barrier1[W][OA

    PubMed Central

    Buschhaus, Christopher; Jetter, Reinhard

    2012-01-01

    Plants prevent dehydration by coating their aerial, primary organs with waxes. Wax compositions frequently differ between species, organs, and developmental stages, probably to balance limiting nonstomatal water loss with various other ecophysiological roles of surface waxes. To establish structure-function relationships, we quantified the composition and transpiration barrier properties of the gl1 mutant leaf waxes of Arabidopsis (Arabidopsis thaliana) to the necessary spatial resolution. The waxes coating the upper and lower leaf surfaces had distinct compositions. Moreover, within the adaxial wax, the epicuticular layer contained more wax and a higher relative quantity of alkanes, whereas the intracuticular wax had a higher percentage of alcohols. The wax formed a barrier against nonstomatal water loss, where the outer layer contributed twice as much resistance as the inner layer. Based on this detailed description of Arabidopsis leaf waxes, structure-function relationships can now be established by manipulating one cuticle component and assessing the effect on cuticle functions. Next, we ectopically expressed the triterpenoid synthase gene AtLUP4 (for lupeol synthase4 or β-amyrin synthase) to compare water loss with and without added cuticular triterpenoids in Arabidopsis leaf waxes. β-Amyrin accumulated solely in the intracuticular wax, constituting up to 4% of this wax layer, without other concomitant changes of wax composition. This triterpenoid accumulation caused a significant reduction in the water barrier effectiveness of the intracuticular wax. PMID:22885935

  14. Ectopic expression of R3 MYB transcription factor gene OsTCL1 in Arabidopsis, but not rice, affects trichome and root hair formation.

    PubMed

    Zheng, Kaijie; Tian, Hainan; Hu, Qingnan; Guo, Hongyan; Yang, Li; Cai, Ling; Wang, Xutong; Liu, Bao; Wang, Shucai

    2016-01-01

    In Arabidopsis, a MYB-bHLH-WD40 (MBW) transcriptional activator complex activates the homeodomain protein gene GLABRA2 (GL2), leading to the promotion of trichome formation and inhibition of root hair formation. The same MBW complex also activates single-repeat R3 MYB genes. R3 MYBs in turn, play a negative feedback role by competing with R2R3 MYB proteins for binding bHLH proteins, thus blocking the formation of the MBW complex. By BLASTing the rice (Oryza sativa) protein database using the entire amino acid sequence of Arabidopsis R3 MYB transcription factor TRICHOMELESS1 (TCL1), we found that there are two genes in rice genome encoding R3 MYB transcription factors, namely Oryza sativa TRICHOMELESS1 (OsTCL1) and OsTCL2. Expressing OsTCL1 in Arabidopsis inhibited trichome formation and promoted root hair formation, and OsTCL1 interacted with GL3 when tested in Arabidopsis protoplasts. Consistent with these observations, expression levels of GL2, R2R3 MYB transcription factor gene GLABRA1 (GL1) and several R3 MYB genes were greatly reduced, indicating that OsTCL1 is functional R3 MYB. However, trichome and root hair formation in transgenic rice plants overexpressing OsTCL1 remained largely unchanged, and elevated expression of OsGL2 was observed in the transgenic rice plants, indicating that rice may use different mechanisms to regulate trichome formation. PMID:26758286

  15. Ectopic expression of R3 MYB transcription factor gene OsTCL1 in Arabidopsis, but not rice, affects trichome and root hair formation

    PubMed Central

    Zheng, Kaijie; Tian, Hainan; Hu, Qingnan; Guo, Hongyan; Yang, Li; Cai, Ling; Wang, Xutong; Liu, Bao; Wang, Shucai

    2016-01-01

    In Arabidopsis, a MYB-bHLH-WD40 (MBW) transcriptional activator complex activates the homeodomain protein gene GLABRA2 (GL2), leading to the promotion of trichome formation and inhibition of root hair formation. The same MBW complex also activates single-repeat R3 MYB genes. R3 MYBs in turn, play a negative feedback role by competing with R2R3 MYB proteins for binding bHLH proteins, thus blocking the formation of the MBW complex. By BLASTing the rice (Oryza sativa) protein database using the entire amino acid sequence of Arabidopsis R3 MYB transcription factor TRICHOMELESS1 (TCL1), we found that there are two genes in rice genome encoding R3 MYB transcription factors, namely Oryza sativa TRICHOMELESS1 (OsTCL1) and OsTCL2. Expressing OsTCL1 in Arabidopsis inhibited trichome formation and promoted root hair formation, and OsTCL1 interacted with GL3 when tested in Arabidopsis protoplasts. Consistent with these observations, expression levels of GL2, R2R3 MYB transcription factor gene GLABRA1 (GL1) and several R3 MYB genes were greatly reduced, indicating that OsTCL1 is functional R3 MYB. However, trichome and root hair formation in transgenic rice plants overexpressing OsTCL1 remained largely unchanged, and elevated expression of OsGL2 was observed in the transgenic rice plants, indicating that rice may use different mechanisms to regulate trichome formation. PMID:26758286

  16. CTBT (7-chlorotetrazolo[5,1-c]benzo[1,2,4]triazine) producing ROS affects growth and viability of filamentous fungi.

    PubMed

    Culakova, Hana; Dzugasova, Vladimira; Gbelska, Yvetta; Subik, Julius

    2012-03-01

    CTBT (7-chlorotetrazolo[5,1-c]benzo[1,2,4]triazine) causes intracellular superoxide production and oxidative stress and enhances the susceptibility of Saccharomyces cerevisiae, Candida albicans, and C. glabrata cells to cycloheximide, 5-fluorocytosine, and azole antimycotic drugs. Here, we demonstrate the antifungal activity of CTBT against 14 tested filamentous fungi. CTBT prevented spore germination and mycelial proliferation of Aspergillus niger and the pathogenic Aspergillus fumigatus. The action of CTBT is fungicidal. CTBT increased the formation of reactive oxygen species in fungal mycelium as detected by 2',7'-dichlorodihydrofluorescein diacetate and reduced the radial growth of colonies in a dose-dependent manner. Co-application of CTBT and itraconazole led to complete inhibition of fungal growth at dosages lower than the chemicals alone. Antifungal and chemosensitizing activities of CTBT in filamentous fungi may be useful in combination treatments of infections caused by drug-resistant fungal pathogens. PMID:22212016

  17. The Arabidopsis thaliana Immunophilin ROF1 Directly Interacts with PI(3)P and PI(3,5)P2 and Affects Germination under Osmotic Stress

    PubMed Central

    Karali, Debora; Oxley, David; Runions, John; Ktistakis, Nicholas; Farmaki, Theodora

    2012-01-01

    A direct interaction of the Arabidopsis thaliana immunophilin ROF1 with phosphatidylinositol-3-phosphate and phosphatidylinositol-3,5-bisphosphate was identified using a phosphatidylinositol-phosphate affinity chromatography of cell suspension extracts, combined with a mass spectrometry (nano LC ESI-MS/MS) analysis. The first FK506 binding domain was shown sufficient to bind to both phosphatidylinositol-phosphate stereoisomers. GFP-tagged ROF1 under the control of a 35S promoter was localised in the cytoplasm and the cell periphery of Nicotiana tabacum leaf explants. Immunofluorescence microscopy of Arabidopsis thaliana root tips verified its cytoplasmic localization and membrane association and showed ROF1 localization in the elongation zone which was expanded to the meristematic zone in plants grown on high salt media. Endogenous ROF1 was shown to accumulate in response to high salt treatment in Arabidopsis thaliana young leaves as well as in seedlings germinated on high salt media (0.15 and 0.2 M NaCl) at both an mRNA and protein level. Plants over-expressing ROF1, (WSROF1OE), exhibited enhanced germination under salinity stress which was significantly reduced in the rof1− knock out mutants and abolished in the double mutants of ROF1 and of its interacting homologue ROF2 (WSrof1−/2−). Our results show that ROF1 plays an important role in the osmotic/salt stress responses of germinating Arabidopsis thaliana seedlings and suggest its involvement in salinity stress responses through a phosphatidylinositol-phosphate related protein quality control pathway. PMID:23133621

  18. The Arabidopsis-related halophyte Thellungiella halophila: boron tolerance via boron complexation with metabolites?

    PubMed

    Lamdan, Netta Li; Attia, Ziv; Moran, Nava; Moshelion, Menachem

    2012-04-01

    Tolerance to boron (B) is still not completely understood. We tested here the hypothesis that Thellungiella halophila, an Arabidopsis thaliana-related 'extremophile' plant, with abundance of B in its natural environment, is tolerant to B, and examined the potential mechanisms of this tolerance. With 1-10 mm B applied ([B](ext)) to Thellungiella and Arabidopsis grown in hydroponics, the steady-state accumulated B concentration ([B](int)) in the root was below [B](ext), and was similar in both, suggesting both extrude B actively. Whether grown in soil or hydroponically, the shoot [B](int) was higher in Arabidopsis than in Thellungiella, suggesting more effective net B exclusion by Thellungiella root. Arabidopsis exhibited toxicity symptoms including reduced shoot fresh weight (FW), but Thellungiella was not affected, even at similar levels of shoot-accumulated [B](int) (about 10 to 40 mm B in 'shoot water'), suggesting additional B tolerance mechanism in Thellungiella shoot. At [B](ext) = 5 mm, the summed shoot concentration of the potentially B-binding polyhydroxyl metabolites (malic acid, fructose, glucose, sucrose and citric acid) in Arabidopsis was below [B](int) , but in Thellungiella it was over twofold higher than [B](int) , and therefore likely to allow appreciable 1:2 boron-metabolite complexation in the shoot. This, we suggest, is an important component of Thellungiella B tolerance mechanism. PMID:21999349

  19. Plastidial Glyceraldehyde-3-Phosphate Dehydrogenase Deficiency Leads to Altered Root Development and Affects the Sugar and Amino Acid Balance in Arabidopsis1[W

    PubMed Central

    Muñoz-Bertomeu, Jesús; Cascales-Miñana, Borja; Mulet, Jose Miguel; Baroja-Fernández, Edurne; Pozueta-Romero, Javier; Kuhn, Josef M.; Segura, Juan; Ros, Roc

    2009-01-01

    Glycolysis is a central metabolic pathway that, in plants, occurs in both the cytosol and the plastids. The glycolytic glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate with concomitant reduction of NAD+ to NADH. Both cytosolic (GAPCs) and plastidial (GAPCps) GAPDH activities have been described. However, the in vivo functions of the plastidial isoforms remain unresolved. In this work, we have identified two Arabidopsis (Arabidopsis thaliana) chloroplast/plastid-localized GAPDH isoforms (GAPCp1 and GAPCp2). gapcp double mutants display a drastic phenotype of arrested root development, dwarfism, and sterility. In spite of their low gene expression level as compared with other GAPDHs, GAPCp down-regulation leads to altered gene expression and to drastic changes in the sugar and amino acid balance of the plant. We demonstrate that GAPCps are important for the synthesis of serine in roots. Serine supplementation to the growth medium rescues root developmental arrest and restores normal levels of carbohydrates and sugar biosynthetic activities in gapcp double mutants. We provide evidence that the phosphorylated pathway of Ser biosynthesis plays an important role in supplying serine to roots. Overall, these studies provide insights into the in vivo functions of the GAPCps in plants. Our results emphasize the importance of the plastidial glycolytic pathway, and specifically of GAPCps, in plant primary metabolism. PMID:19675149

  20. Inactivation of the Phloem-Specific Dof Zinc Finger Gene DAG1 Affects Response to Light and Integrity of the Testa of Arabidopsis Seeds1

    PubMed Central

    Papi, Maura; Sabatini, Sabrina; Altamura, Maria Maddalena; Hennig, Lars; Schäfer, Eberhard; Costantino, Paolo; Vittorioso, Paola

    2002-01-01

    We show here that seeds from the knockout mutant of the Arabidopsis DAG1 gene encoding a Dof zinc finger transcription factor have an altered response to red and far-red light. Mutant dag1 seeds are induced to germinate by much lower red light fluence rates, and germination reaches more quickly a point where it is independent of phytochrome signaling. Moreover, although microscopic analysis reveals no obvious structural alterations in the seed coat (testa) of dag1 seeds, staining assays with different dyes point to an abnormal fragility of the testa. By extensive in situ mRNA hybridization analysis we show here that the gene, which is not expressed in the embryo, is specifically expressed in the phloem of all organs of the mother plant. PMID:11842145

  1. Analysis of the Metabolic Pathways Affected by Poly(γ-glutamic Acid) in Arabidopsis thaliana Based on GeneChip Microarray.

    PubMed

    Xu, Zongqi; Lei, Peng; Feng, Xiaohai; Li, Sha; Xu, Hong

    2016-08-17

    Plant growth is promoted by poly(γ-glutamic acid) (γ-PGA). However, the molecular mechanism underlying such promotion is not yet well understood. Therefore, we used GeneChip microarrays to explore the effects of γ-PGA on gene transcription in Arabidopsis thaliana. Our results revealed 299 genes significantly regulated by γ-PGA. These differently expressed genes participate mainly in metabolic and cellular processes and in stimuli responses. The metabolic pathways linked to these differently expressed genes were also investigated. A total of 64 of the 299 differently expressed genes were shown to be directly involved in 24 pathways such as brassinosteroid biosynthesis, α-linolenic acid metabolism, phenylpropanoid biosynthesis, and nitrogen metabolism, all of which were influenced by γ-PGA. The analysis demonstrated that γ-PGA promoted nitrogen assimilation and biosynthesis of brassinosteroids, jasmonic acid, and lignins, providing a better explanation for why γ-PGA promotes growth and enhances stress tolerance in plants. PMID:27465513

  2. Loss of Calmodulin Binding to Bax Inhibitor-1 Affects Pseudomonas-mediated Hypersensitive Response-associated Cell Death in Arabidopsis thaliana*

    PubMed Central

    Kawai-Yamada, Maki; Hori, Zenta; Ogawa, Taro; Ihara-Ohori, Yuri; Tamura, Katsunori; Nagano, Minoru; Ishikawa, Toshiki; Uchimiya, Hirofumi

    2009-01-01

    Bax inhibitor-1 (BI-1) is a cell death suppressor protein conserved across a variety of organisms. The Arabidopsis atbi1-1 plant is a mutant in which the C-terminal 6 amino acids of the expressed BI-1 protein have been replaced by T-DNA insertion. This mutant BI-1 protein (AtBI-CM) produced in Escherichia coli can no longer bind to calmodulin. A promoter-reporter assay demonstrated compartmentalized expression of BI-1 during hypersensitive response, introduced by the inoculation of Pseudomonas syringae possessing the avrRTP2 gene, Pst(avrRPT2). In addition, both BI-1 knockdown plants and atbi1-1 showed increased sensitivity to Pst(avrRPT2)-induced cell death. The results indicated that the loss of calmodulin binding reduces the cell death suppressor activity of BI-1 in planta. PMID:19674971

  3. Acute morphine affects the rat circadian clock via rhythms of phosphorylated ERK1/2 and GSK3β kinases and Per1 expression in the rat suprachiasmatic nucleus

    PubMed Central

    Pačesová, Dominika; Volfová, Barbora; Červená, Kateřina; Hejnová, Lucie; Novotný, Jiří; Bendová, Zdeňka

    2015-01-01

    Background and Purpose Opioids affect the circadian clock and may change the timing of many physiological processes. This study was undertaken to investigate the daily changes in sensitivity of the circadian pacemaker to an analgesic dose of morphine, and to uncover a possible interplay between circadian and opioid signalling. Experimental Approach A time-dependent effect of morphine (1 mg·kg−1, i.p.) applied either during the day or during the early night was followed, and the levels of phosphorylated ERK1/2, GSK3β, c-Fos and Per genes were assessed by immunohistochemistry and in situ hybridization. The effect of morphine pretreatment on light-induced pERK and c-Fos was examined, and day/night difference in activity of opioid receptors was evaluated by [35S]-GTPγS binding assay. Key Results Morphine stimulated a rise in pERK1/2 and pGSK3β levels in the suprachiasmatic nucleus (SCN) when applied during the day but significantly reduced both kinases when applied during the night. Morphine at night transiently induced Period1 but not Period2 in the SCN and did not attenuate the light-induced level of pERK1/2 and c-Fos in the SCN. The activity of all three principal opioid receptors was high during the day but decreased significantly at night, except for the δ receptor. Finally, we demonstrated daily profiles of pERK1/2 and pGSK3β levels in the rat ventrolateral and dorsomedial SCN. Conclusions and Implications Our data suggest that the phase-shifting effect of opioids may be mediated via post-translational modification of clock proteins by means of activated ERK1/2 and GSK3β. PMID:25828914

  4. Chlorophyll Synthase under Epigenetic Surveillance Is Critical for Vitamin E Synthesis, and Altered Expression Affects Tocopherol Levels in Arabidopsis1[OPEN

    PubMed Central

    Zhang, Chunyu; Zhang, Wei; Ren, Guodong; Li, Delin; Cahoon, Rebecca E.; Chen, Ming; Zhou, Yongming; Yu, Bin; Cahoon, Edgar B.

    2015-01-01

    Chlorophyll synthase catalyzes the final step in chlorophyll biosynthesis: the esterification of chlorophyllide with either geranylgeranyl diphosphate or phytyl diphosphate (PDP). Recent studies have pointed to the involvement of chlorophyll-linked reduction of geranylgeranyl by geranylgeranyl reductase as a major pathway for the synthesis of the PDP precursor of tocopherols. This indirect pathway of PDP synthesis suggests a key role of chlorophyll synthase in tocopherol production to generate the geranylgeranyl-chlorophyll substrate for geranylgeranyl reductase. In this study, contributions of chlorophyll synthase to tocopherol formation in Arabidopsis (Arabidopsis thaliana) were explored by disrupting and altering expression of the corresponding gene CHLOROPHYLL SYNTHASE (CHLSYN; At3g51820). Leaves from the homozygous chlysyn1-1 null mutant were nearly devoid of tocopherols, whereas seeds contained only approximately 25% of wild-type tocopherol levels. Leaves of RNA interference lines with partial suppression of CHLSYN displayed marked reductions in chlorophyll but up to a 2-fold increase in tocopherol concentrations. Cauliflower mosaic virus35S-mediated overexpression of CHLSYN unexpectedly caused a cosuppression phenotype at high frequencies accompanied by strongly reduced chlorophyll content and increased tocopherol levels. This phenotype and the associated detection of CHLSYN-derived small interfering RNAs were reversed with CHLSYN overexpression in rna-directed rna polymerase6 (rdr6), which is defective in RNA-dependent RNA polymerase6, a key enzyme in sense transgene-induced small interfering RNA production. CHLSYN overexpression in rdr6 had little effect on chlorophyll content but resulted in up to a 30% reduction in tocopherol levels in leaves. These findings show that altered CHLSYN expression impacts tocopherol levels and also, show a strong epigenetic surveillance of CHLSYN to control chlorophyll and tocopherol synthesis. PMID:26048882

  5. Targeted enhancement of glutamate-to-γ-aminobutyrate conversion in Arabidopsis seeds affects carbon-nitrogen balance and storage reserves in a development-dependent manner.

    PubMed

    Fait, Aaron; Nesi, Adriano Nunes; Angelovici, Ruthie; Lehmann, Martin; Pham, Phuong Anh; Song, Luhua; Haslam, Richard P; Napier, Johnathan A; Galili, Gad; Fernie, Alisdair R

    2011-11-01

    In seeds, glutamate decarboxylase (GAD) operates at the metabolic nexus between carbon and nitrogen metabolism by catalyzing the unidirectional decarboxylation of glutamate to form γ-aminobutyric acid (GABA). To elucidate the regulatory role of GAD in seed development, we generated Arabidopsis (Arabidopsis thaliana) transgenic plants expressing a truncated GAD from Petunia hybrida missing the carboxyl-terminal regulatory Ca(2+)-calmodulin-binding domain under the transcriptional regulation of the seed maturation-specific phaseolin promoter. Dry seeds of the transgenic plants accumulated considerable amounts of GABA, and during desiccation the content of several amino acids increased, although not glutamate or proline. Dry transgenic seeds had higher protein content than wild-type seeds but lower amounts of the intermediates of glycolysis, glycerol and malate. The total fatty acid content of the transgenic seeds was 50% lower than in the wild type, while acyl-coenzyme A accumulated in the transgenic seeds. Labeling experiments revealed altered levels of respiration in the transgenic seeds, and fractionation studies indicated reduced incorporation of label in the sugar and lipid fractions extracted from transgenic seeds. Comparative transcript profiling of the dry seeds supported the metabolic data. Cellular processes up-regulated at the transcript level included the tricarboxylic acid cycle, fatty acid elongation, the shikimate pathway, tryptophan metabolism, nitrogen-carbon remobilization, and programmed cell death. Genes involved in the regulation of germination were similarly up-regulated. Taken together, these results indicate that the GAD-mediated conversion of glutamate to GABA during seed development plays an important role in balancing carbon and nitrogen metabolism and in storage reserve accumulation. PMID:21921115

  6. Changes in the effective gravitational field strength affect the state of phosphorylation of stress-related proteins in callus cultures of Arabidopsis thaliana

    PubMed Central

    Barjaktarović, Žarko; Schütz, Wolfgang; Madlung, Johannes; Fladerer, Claudia; Nordheim, Alfred; Hampp, Rüdiger

    2009-01-01

    In a recent study it was shown that callus cell cultures of Arabidopsis thaliana respond to changes in gravitational field strengths by changes in protein expression. Using ESI-MS/MS for proteins with differential abundance after separation by 2D-PAGE, 28 spots which changed reproducibly and significantly in amount (P <0.05) after 2 h of hypergravity (18 up-regulated, 10 down-regulated) could be identified. The corresponding proteins were largely involved in stress responses, including the detoxification of reactive oxygen species (ROS). In the present study, these investigations are extended to phosphorylated proteins. For this purpose, callus cell cultures of Arabidopsis thaliana were exposed to hypergravity (8 g) and simulated weightlessness (random positioning; RP) for up to 30 min, a period of time which yielded the most reliable data. The first changes, however, were visible as early as 10 min after the start of treatment. In comparison to 1 g controls, exposure to hypergravity resulted in 18 protein spots, and random positioning in 25, respectively, with increased/decreased signal intensity by at least 2-fold (P <0.05). Only one spot (alanine aminotransferase) responded the same way under both treatments. After 30 min of RP, four spots appeared, which could not be detected in control samples. Among the protein spots altered in phosphorylation, it was possible to identify 24 from those responding to random positioning and 12 which responded to 8 g. These 12 proteins (8 g) are partly (5 out of 12) the same as those changed in expression after exposure to 2 h of hypergravity. The respective proteins are involved in scavenging and detoxification of ROS (32%), primary metabolism (20.5%), general signalling (14.7%), protein translation and proteolysis (14.7%), and ion homeostasis (8.8%). Together with our recent data on protein expression, it is assumed that changes in gravitational fields induce the production of ROS. Our data further indicate that responses

  7. Elevated CO2-induced production of nitric oxide (NO) by NO synthase differentially affects nitrate reductase activity in Arabidopsis plants under different nitrate supplies.

    PubMed

    Du, Shaoting; Zhang, Ranran; Zhang, Peng; Liu, Huijun; Yan, Minggang; Chen, Ni; Xie, Huaqiang; Ke, Shouwei

    2016-02-01

    CO2 elevation often alters the plant's nitrate reductase (NR) activity, the first enzyme acting in the nitrate assimilation pathway. However, the mechanism underlying this process remains unknown. The association between elevated CO2-induced alterations of NR activity and nitric oxide (NO) was examined in Col-0 Arabidopsis fed with 0.2-10 mM nitrate, using NO donors, NO scavenger, and NO synthase (NOS) inhibitor. The noa1 mutant, in which most NOS activity was lost, and the NR activity-null mutant nia1 nia2 were also used to examine the above association. In response to CO2 elevation, NR activity increased in low-nitrate Col-0 plants but was inhibited in high-nitrate Col-0 plants. NO scavenger and NOS inhibitor could eliminate these two responses, whereas the application of NO donors mimicked these distinct responses in ambient CO2-grown Col-0 plants. Furthermore, in both low- and high-nitrate conditions, elevated CO2 increased NOS activity and NO levels in Col-0 and nia1 nia2 plants but had little effect on NO level and NR activity in noa1 plants. Considering all of these findings, this study concluded that, in response to CO2 elevation, either the NR activity induction in low-nitrate plants or the NR activity inhibition in high-nitrate plants is regulated by NOS-generated NO. PMID:26608644

  8. Circadian Stress Regimes Affect the Circadian Clock and Cause Jasmonic Acid-Dependent Cell Death in Cytokinin-Deficient Arabidopsis Plants.

    PubMed

    Nitschke, Silvia; Cortleven, Anne; Iven, Tim; Feussner, Ivo; Havaux, Michel; Riefler, Michael; Schmülling, Thomas

    2016-07-01

    The circadian clock helps plants measure daylength and adapt to changes in the day-night rhythm. We found that changes in the light-dark regime triggered stress responses, eventually leading to cell death, in leaves of Arabidopsis thaliana plants with reduced cytokinin levels or defective cytokinin signaling. Prolonged light treatment followed by a dark period induced stress and cell death marker genes while reducing photosynthetic efficiency. This response, called circadian stress, is also characterized by altered expression of clock and clock output genes. In particular, this treatment strongly reduced the expression of CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY). Intriguingly, similar changes in gene expression and cell death were observed in clock mutants lacking proper CCA1 and LHY function. Circadian stress caused strong changes in reactive oxygen species- and jasmonic acid (JA)-related gene expression. The activation of the JA pathway, involving the accumulation of JA metabolites, was crucial for the induction of cell death, since the cell death phenotype was strongly reduced in the jasmonate resistant1 mutant background. We propose that adaptation to circadian stress regimes requires a normal cytokinin status which, acting primarily through the AHK3 receptor, supports circadian clock function to guard against the detrimental effects of circadian stress. PMID:27354555

  9. A Naturally Occurring Mutation in an Arabidopsis Accession Affects a β-d-Galactosidase That Increases the Hydrophilic Potential of Rhamnogalacturonan I in Seed Mucilage[W

    PubMed Central

    Macquet, Audrey; Ralet, Marie-Christine; Loudet, Olivier; Kronenberger, Jocelyne; Mouille, Gregory; Marion-Poll, Annie; North, Helen M.

    2007-01-01

    The Arabidopsis thaliana accession Shahdara was identified as a rare naturally occurring mutant that does not liberate seed mucilage on imbibition. The defective locus was found to be allelic to the mum2-1 and mum2-2 mutants. Map-based cloning showed that MUCILAGE-MODIFIED2 (MUM2) encodes the putative β-d-galactosidase BGAL6. Activity assays demonstrated that one of four major β-d-galactosidase activities present in developing siliques is absent in mum2 mutants. No difference was observed in seed coat epidermal cell structure between wild-type and mutant seed; however, weakening of the outer tangential cell wall by chemical treatment resulted in the release of mucilage from mum2 seed coat epidermal cells, and the mum2 mucilage only increased slightly in volume, relative to the wild type. Consistent with the absence of β-d-galactosidase activity in the mutant, the inner layer of mucilage contained more Gal. The allocation of polysaccharides between the inner and outer mucilage layers was also modified in mum2. Mass spectrometry showed that rhamnogalacturonan I in mutant mucilage had more branching between rhamnose and hexose residues relative to the wild type. We conclude that the MUM2/BGAL6 β-d-galactosidase is required for maturation of rhamnogalacturonan I in seed mucilage by the removal of galactose/galactan branches, resulting in increased swelling and extrusion of the mucilage on seed hydration. PMID:18165330

  10. The phospholipid-deficient pho1 mutant of Arabidopsis thaliana is affected in the organization, but not in the light acclimation, of the thylakoid membrane.

    PubMed

    Härtel, H; Essigmann, B; Lokstein, H; Hoffmann-Benning, S; Peters-Kottig, M; Benning, C

    1998-12-01

    The pho1 mutant of Arabidopsis has been shown to respond to the phosphate deficiency in the leaves by decreasing the amount of phosphatidylglycerol (PG). PG is thought to be of crucial importance for the organization and function of the thylakoid membrane. This prompted us to ask what the consequences of the PG deficiency may be in the pho1 mutant when grown under low or high light. While in the wild-type, the lipid pattern was almost insensitive to changes in the growth light, PG was reduced to 45% under low light in the mutant, and it decreased further to 35% under high light. Concomitantly, sulfoquinovosyl diacylglycerol (SQDG) and to a lesser extent digalactosyl diacylglycerol (DGDG) increased. The SQDG increase correlated with increased amounts of the SQD1 protein, an indicator for an actively mediated process. Despite of alterations in the ultrastructure, mutant thylakoids showed virtually no effects on photosynthetic electron transfer, O2 evolution and excitation energy allocation to the reaction centers. Our results support the idea that PG deficiency can at least partially be compensated for by the anionic lipid SQDG and the not charged lipid DGDG. This seems to be an important strategy to maintain an optimal thylakoid lipid milieu for vital processes, such as photosynthesis, under a restricted phosphate availability. PMID:9858733

  11. A mutation in the Arabidopsis HYL1 gene encoding a dsRNA binding protein affects responses to abscisic acid, auxin, and cytokinin

    NASA Technical Reports Server (NTRS)

    Lu, C.; Fedoroff, N.

    2000-01-01

    Both physiological and genetic evidence indicate interconnections among plant responses to different hormones. We describe a pleiotropic recessive Arabidopsis transposon insertion mutation, designated hyponastic leaves (hyl1), that alters the plant's responses to several hormones. The mutant is characterized by shorter stature, delayed flowering, leaf hyponasty, reduced fertility, decreased rate of root growth, and an altered root gravitropic response. It also exhibits less sensitivity to auxin and cytokinin and hypersensitivity to abscisic acid (ABA). The auxin transport inhibitor 2,3,5-triiodobenzoic acid normalizes the mutant phenotype somewhat, whereas another auxin transport inhibitor, N-(1-naph-thyl)phthalamic acid, exacerbates the phenotype. The gene, designated HYL1, encodes a 419-amino acid protein that contains two double-stranded RNA (dsRNA) binding motifs, a nuclear localization motif, and a C-terminal repeat structure suggestive of a protein-protein interaction domain. We present evidence that the HYL1 gene is ABA-regulated and encodes a nuclear dsRNA binding protein. We hypothesize that the HYL1 protein is a regulatory protein functioning at the transcriptional or post-transcriptional level.

  12. Barley Hv CIRCADIAN CLOCK ASSOCIATED 1 and Hv PHOTOPERIOD H1 Are Circadian Regulators That Can Affect Circadian Rhythms in Arabidopsis

    PubMed Central

    Martí, María C.; Laurie, David A.; Greenland, Andy J.; Hall, Anthony; Webb, Alex A. R.

    2015-01-01

    Circadian clocks regulate many aspects of plant physiology and development that contribute to essential agronomic traits. Circadian clocks contain transcriptional feedback loops that are thought to generate circadian timing. There is considerable similarity in the genes that comprise the transcriptional and translational feedback loops of the circadian clock in the plant Kingdom. Functional characterisation of circadian clock genes has been restricted to a few model species. Here we provide a functional characterisation of the Hordeum vulgare (barley) circadian clock genes Hv CIRCADIAN CLOCK ASSOCIATED 1 (HvCCA1) and Hv PHOTOPERIODH1, which are respectively most similar to Arabidopsis thaliana CIRCADIAN CLOCK ASSOCIATED 1 (AtCCA1) and PSEUDO RESPONSE REGULATOR 7 (AtPRR7). This provides insight into the circadian regulation of one of the major crop species of Northern Europe. Through a combination of physiological assays of circadian rhythms in barley and heterologous expression in wild type and mutant strains of A. thaliana we demonstrate that HvCCA1 has a conserved function to AtCCA1. We find that Hv PHOTOPERIOD H1 has AtPRR7-like functionality in A. thaliana and that the effects of the Hv photoperiod h1 mutation on photoperiodism and circadian rhythms are genetically separable. PMID:26076005

  13. Time-Series Transcriptomics Reveals That AGAMOUS-LIKE22 Affects Primary Metabolism and Developmental Processes in Drought-Stressed Arabidopsis[OPEN

    PubMed Central

    Penfold, Christopher A.; Jenkins, Dafyd J.; Legaie, Roxane; Lawson, Tracy; Vialet-Chabrand, Silvere R.M.; Subramaniam, Sunitha; Hickman, Richard; Feil, Regina; Bowden, Laura; Hill, Claire; Lunn, John E.; Finkenstädt, Bärbel; Buchanan-Wollaston, Vicky; Beynon, Jim; Wild, David L.; Ott, Sascha

    2016-01-01

    In Arabidopsis thaliana, changes in metabolism and gene expression drive increased drought tolerance and initiate diverse drought avoidance and escape responses. To address regulatory processes that link these responses, we set out to identify genes that govern early responses to drought. To do this, a high-resolution time series transcriptomics data set was produced, coupled with detailed physiological and metabolic analyses of plants subjected to a slow transition from well-watered to drought conditions. A total of 1815 drought-responsive differentially expressed genes were identified. The early changes in gene expression coincided with a drop in carbon assimilation, and only in the late stages with an increase in foliar abscisic acid content. To identify gene regulatory networks (GRNs) mediating the transition between the early and late stages of drought, we used Bayesian network modeling of differentially expressed transcription factor (TF) genes. This approach identified AGAMOUS-LIKE22 (AGL22), as key hub gene in a TF GRN. It has previously been shown that AGL22 is involved in the transition from vegetative state to flowering but here we show that AGL22 expression influences steady state photosynthetic rates and lifetime water use. This suggests that AGL22 uniquely regulates a transcriptional network during drought stress, linking changes in primary metabolism and the initiation of stress responses. PMID:26842464

  14. Time-Series Transcriptomics Reveals That AGAMOUS-LIKE22 Affects Primary Metabolism and Developmental Processes in Drought-Stressed Arabidopsis.

    PubMed

    Bechtold, Ulrike; Penfold, Christopher A; Jenkins, Dafyd J; Legaie, Roxane; Moore, Jonathan D; Lawson, Tracy; Matthews, Jack S A; Vialet-Chabrand, Silvere R M; Baxter, Laura; Subramaniam, Sunitha; Hickman, Richard; Florance, Hannah; Sambles, Christine; Salmon, Deborah L; Feil, Regina; Bowden, Laura; Hill, Claire; Baker, Neil R; Lunn, John E; Finkenstädt, Bärbel; Mead, Andrew; Buchanan-Wollaston, Vicky; Beynon, Jim; Rand, David A; Wild, David L; Denby, Katherine J; Ott, Sascha; Smirnoff, Nicholas; Mullineaux, Philip M

    2016-02-01

    In Arabidopsis thaliana, changes in metabolism and gene expression drive increased drought tolerance and initiate diverse drought avoidance and escape responses. To address regulatory processes that link these responses, we set out to identify genes that govern early responses to drought. To do this, a high-resolution time series transcriptomics data set was produced, coupled with detailed physiological and metabolic analyses of plants subjected to a slow transition from well-watered to drought conditions. A total of 1815 drought-responsive differentially expressed genes were identified. The early changes in gene expression coincided with a drop in carbon assimilation, and only in the late stages with an increase in foliar abscisic acid content. To identify gene regulatory networks (GRNs) mediating the transition between the early and late stages of drought, we used Bayesian network modeling of differentially expressed transcription factor (TF) genes. This approach identified AGAMOUS-LIKE22 (AGL22), as key hub gene in a TF GRN. It has previously been shown that AGL22 is involved in the transition from vegetative state to flowering but here we show that AGL22 expression influences steady state photosynthetic rates and lifetime water use. This suggests that AGL22 uniquely regulates a transcriptional network during drought stress, linking changes in primary metabolism and the initiation of stress responses. PMID:26842464

  15. Circadian Stress Regimes Affect the Circadian Clock and Cause Jasmonic Acid-Dependent Cell Death in Cytokinin-Deficient Arabidopsis Plants[OPEN

    PubMed Central

    Nitschke, Silvia; Cortleven, Anne; Iven, Tim; Havaux, Michel; Schmülling, Thomas

    2016-01-01

    The circadian clock helps plants measure daylength and adapt to changes in the day-night rhythm. We found that changes in the light-dark regime triggered stress responses, eventually leading to cell death, in leaves of Arabidopsis thaliana plants with reduced cytokinin levels or defective cytokinin signaling. Prolonged light treatment followed by a dark period induced stress and cell death marker genes while reducing photosynthetic efficiency. This response, called circadian stress, is also characterized by altered expression of clock and clock output genes. In particular, this treatment strongly reduced the expression of CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY). Intriguingly, similar changes in gene expression and cell death were observed in clock mutants lacking proper CCA1 and LHY function. Circadian stress caused strong changes in reactive oxygen species- and jasmonic acid (JA)-related gene expression. The activation of the JA pathway, involving the accumulation of JA metabolites, was crucial for the induction of cell death, since the cell death phenotype was strongly reduced in the jasmonate resistant1 mutant background. We propose that adaptation to circadian stress regimes requires a normal cytokinin status which, acting primarily through the AHK3 receptor, supports circadian clock function to guard against the detrimental effects of circadian stress. PMID:27354555

  16. ZmXTH1, a new xyloglucan endotransglucosylase/hydrolase in maize, affects cell wall structure and composition in Arabidopsis thaliana.

    PubMed

    Genovesi, Valeria; Fornalé, Silvia; Fry, Stephen C; Ruel, Katia; Ferrer, Pau; Encina, Antonio; Sonbol, Fathi-Mohamed; Bosch, Josep; Puigdomènech, Pere; Rigau, Joan; Caparrós-Ruiz, David

    2008-01-01

    Xyloglucan endotransglucosylase/hydrolases (XTHs; EC 2.4.1.207 and/or EC 3.2.1.151) are enzymes involved in the modification of cell wall structure by cleaving and, often, also re-joining xyloglucan molecules in primary plant cell walls. Using a pool of antibodies raised against an enriched cell wall protein fraction, a new XTH cDNA in maize, ZmXTH1, has been isolated from a cDNA expression library obtained from the elongation zone of the maize root. The predicted protein has a putative N-terminal signal peptide and possesses the typical domains of this enzyme family, such as a catalytic domain that is homologous to that of Bacillus macerans beta-glucanase, a putative N-glycosylation motif, and four cysteine residues in the central and C terminal regions of the ZmXTH1 protein. Phylogenetic analysis of ZmXTH1 reveals that it belongs to subgroup 4, so far only reported from Poaceae monocot species. ZmXTH1 has been expressed in Pichia pastoris (a methylotrophic yeast) and the recombinant enzyme showed xyloglucan endotransglucosylase but not xyloglucan endohydrolase activity, representing the first enzyme belonging to subgroup 4 characterized in maize so far. Expression data indicate that ZmXTH1 is expressed in elongating tissues, modulated by culture conditions, and induced by gibberellins. Transient expression assays in onion cells reveal that ZmXTH1 is directed to the cell wall, although weakly bound. Finally, Arabidopsis thaliana plants expressing ZmXTH1 show slightly increased xyloglucan endohydrolase activity and alterations in the cell wall structure and composition. PMID:18316315

  17. Variation in MPK12 affects water use efficiency in Arabidopsis and reveals a pleiotropic link between guard cell size and ABA response

    PubMed Central

    Des Marais, David L.; Auchincloss, Lisa C.; Sukamtoh, Emeline; McKay, John K.; Logan, Tierney; Richards, James H.; Juenger, Thomas E.

    2014-01-01

    Plant water relations are critical for determining the distribution, persistence, and fitness of plant species. Studying the genetic basis of ecologically relevant traits, however, can be complicated by their complex genetic, physiological, and developmental basis and their interaction with the environment. Water use efficiency (WUE), the ratio of photosynthetic carbon assimilation to stomatal conductance to water, is a dynamic trait with tremendous ecological and agricultural importance whose genetic control is poorly understood. In the present study, we use a quantitative trait locus-mapping approach to locate, fine-map, clone, confirm, and characterize an allelic substitution that drives differences in WUE among natural accessions of Arabidopsis thaliana. We show that a single amino acid substitution in an abscisic acid-responsive kinase, AtMPK12, causes reduction in WUE, and we confirm its functional role using transgenics. We further demonstrate that natural alleles at AtMPK12 differ in their response to cellular and environmental cues, with the allele from the Cape Verde Islands (CVI) being less responsive to hormonal inhibition of stomatal opening and more responsive to short-term changes in vapor pressure deficit. We also show that the CVI allele results in constitutively larger stomata. Together, these differences cause higher stomatal conductance and lower WUE compared with the common allele. These physiological changes resulted in reduced whole-plant transpiration efficiency and reduced fitness under water-limited compared with well-watered conditions. Our work demonstrates how detailed analysis of naturally segregating functional variation can uncover the molecular and physiological basis of a key trait associated with plant performance in ecological and agricultural settings. PMID:24550314

  18. Knocking Out ACR2 Does Not Affect Arsenic Redox Status in Arabidopsis thaliana: Implications for As Detoxification and Accumulation in Plants

    PubMed Central

    Liu, Wenju; Schat, Henk; Bliek, Mathijs; Chen, Yi; McGrath, Steve P.; George, Graham; Salt, David E.; Zhao, Fang-Jie

    2012-01-01

    Many plant species are able to reduce arsenate to arsenite efficiently, which is an important step allowing detoxification of As through either efflux of arsenite or complexation with thiol compounds. It has been suggested that this reduction is catalyzed by ACR2, a plant homologue of the yeast arsenate reductase ScACR2. Silencing of AtACR2 was reported to result in As hyperaccumulation in the shoots of Arabidopsis thaliana. However, no information of the in vivo As speciation has been reported. Here, we investigated the effect of AtACR2 knockout or overexpression on As speciation, arsenite efflux from roots and As accumulation in shoots. T-DNA insertion lines, overexpression lines and wild-type (WT) plants were exposed to different concentrations of arsenate for different periods, and As speciation in plants and arsenite efflux were determined using HPLC-ICP-MS. There were no significant differences in As speciation between different lines, with arsenite accounting for >90% of the total extractable As in both roots and shoots. Arsenite efflux to the external medium represented on average 77% of the arsenate taken up during 6 h exposure, but there were no significant differences between WT and mutants or overexpression lines. Accumulation of As in the shoots was also unaffected by AtACR2 knockout or overexpression. Additionally, after exposure to arsenate, the yeast (Saccharomyces cerevisiae) strain with ScACR2 deleted showed similar As speciation as the WT with arsenite-thiol complexes being the predominant species. Our results suggest the existence of multiple pathways of arsenate reduction in plants and yeast. PMID:22879969

  19. Arabidopsis phosphatidylinositol monophosphate 5-kinase 2 is involved in root gravitropism through regulation of polar auxin transport by affecting the cycling of PIN proteins.

    PubMed

    Mei, Yu; Jia, Wen-Jing; Chu, Yu-Jia; Xue, Hong-Wei

    2012-03-01

    Phosphatidylinositol monophosphate 5-kinase (PIP5K) catalyzes the synthesis of PI-4,5-bisphosphate (PtdIns(4,5)P(2)) by phosphorylation of PI-4-phosphate at the 5 position of the inositol ring, and is involved in regulating multiple developmental processes and stress responses. We here report on the functional characterization of Arabidopsis PIP5K2, which is expressed during lateral root initiation and elongation, and whose expression is enhanced by exogenous auxin. The knockout mutant pip5k2 shows reduced lateral root formation, which could be recovered with exogenous auxin, and interestingly, delayed root gravity response that could not be recovered with exogenous auxin. Crossing with the DR5-GUS marker line and measurement of free IAA content confirmed the reduced auxin accumulation in pip5k2. In addition, analysis using the membrane-selective dye FM4-64 revealed the decelerated vesicle trafficking caused by PtdIns(4,5)P(2) reduction, which hence results in suppressed cycling of PIN proteins (PIN2 and 3), and delayed redistribution of PIN2 and auxin under gravistimulation in pip5k2 roots. On the contrary, PtdIns(4,5)P(2) significantly enhanced the vesicle trafficking and cycling of PIN proteins. These results demonstrate that PIP5K2 is involved in regulating lateral root formation and root gravity response, and reveal a critical role of PIP5K2/PtdIns(4,5)P(2) in root development through regulation of PIN proteins, providing direct evidence of crosstalk between the phosphatidylinositol signaling pathway and auxin response, and new insights into the control of polar auxin transport. PMID:21894193

  20. Variation in MPK12 affects water use efficiency in Arabidopsis and reveals a pleiotropic link between guard cell size and ABA response.

    PubMed

    Des Marais, David L; Auchincloss, Lisa C; Sukamtoh, Emeline; McKay, John K; Logan, Tierney; Richards, James H; Juenger, Thomas E

    2014-02-18

    Plant water relations are critical for determining the distribution, persistence, and fitness of plant species. Studying the genetic basis of ecologically relevant traits, however, can be complicated by their complex genetic, physiological, and developmental basis and their interaction with the environment. Water use efficiency (WUE), the ratio of photosynthetic carbon assimilation to stomatal conductance to water, is a dynamic trait with tremendous ecological and agricultural importance whose genetic control is poorly understood. In the present study, we use a quantitative trait locus-mapping approach to locate, fine-map, clone, confirm, and characterize an allelic substitution that drives differences in WUE among natural accessions of Arabidopsis thaliana. We show that a single amino acid substitution in an abscisic acid-responsive kinase, AtMPK12, causes reduction in WUE, and we confirm its functional role using transgenics. We further demonstrate that natural alleles at AtMPK12 differ in their response to cellular and environmental cues, with the allele from the Cape Verde Islands (CVI) being less responsive to hormonal inhibition of stomatal opening and more responsive to short-term changes in vapor pressure deficit. We also show that the CVI allele results in constitutively larger stomata. Together, these differences cause higher stomatal conductance and lower WUE compared with the common allele. These physiological changes resulted in reduced whole-plant transpiration efficiency and reduced fitness under water-limited compared with well-watered conditions. Our work demonstrates how detailed analysis of naturally segregating functional variation can uncover the molecular and physiological basis of a key trait associated with plant performance in ecological and agricultural settings. PMID:24550314

  1. Arabidopsis PTB1 and PTB2 proteins negatively regulate splicing of a mini-exon splicing reporter and affect alternative splicing of endogenous genes differentially.

    PubMed

    Simpson, Craig G; Lewandowska, Dominika; Liney, Michele; Davidson, Diane; Chapman, Sean; Fuller, John; McNicol, Jim; Shaw, Paul; Brown, John W S

    2014-07-01

    This paper examines the function of Arabidopsis thaliana AtPTB1 and AtPTB2 as plant splicing factors. The effect on splicing of overexpression of AtPTB1 and AtPTB2 was analysed in an in vivo protoplast transient expression system with a novel mini-exon splicing reporter. A range of mutations in pyrimidine-rich sequences were compared with and without AtPTB and NpU2AF65 overexpression. Splicing analyses of constructs in protoplasts and RNA from overexpression lines used high-resolution reverse transcription polymerase chain reaction (RT-PCR). AtPTB1 and AtPTB2 reduced inclusion/splicing of the potato invertase mini-exon splicing reporter, indicating that these proteins can repress plant intron splicing. Mutation of the polypyrimidine tract and closely associated Cytosine and Uracil-rich (CU-rich) sequences, upstream of the mini-exon, altered repression by AtPTB1 and AtPTB2. Coexpression of a plant orthologue of U2AF65 alleviated the splicing repression of AtPTB1. Mutation of a second CU-rich upstream of the mini-exon 3' splice site led to a decline in mini-exon splicing, indicating the presence of a splicing enhancer sequence. Finally, RT-PCR of AtPTB overexpression lines with c. 90 known alternative splicing (AS) events showed that AtPTBs significantly altered AS of over half the events. AtPTB1 and AtPTB2 are splicing factors that influence alternative splicing. This occurs in the potato invertase mini-exon via the polypyrimidine tract and associated pyrimidine-rich sequence. PMID:24749484

  2. An investigation into factors affecting the stability of carbons and carbon supported platinum and platinum/cobalt alloy catalysts during 1.2 V potentiostatic hold regimes at a range of temperatures

    NASA Astrophysics Data System (ADS)

    Ball, S. C.; Hudson, S. L.; Thompsett, D.; Theobald, B.

    To meet automotive targets for fuel cell operation and allow higher temperature operation an understanding of the factors affecting carbon and platinum stability is critical. The stability of both carbons and carbon supported platinum and platinum/cobalt alloy catalysts was studied during 1.2 V versus RHE potentiostatic hold tests using carbon and catalyst coated electrodes in a three-chamber wet electrolyte cell at a range of temperatures. At 80 °C the wt% of carbon corroded increases with increasing BET area. Surface oxidation was followed electrochemically using the quinone/hydroquinone redox couple. Increasing temperature, time at 1.2 V and wt% platinum on the carbon increases surface oxidation. Although increasing temperature was shown to increase the extent of carbon corrosion, catalysing the carbon did not significantly change how much carbon was corroded. Platinum stability was investigated by electrochemical metal area loss (ECA). Platinum catalysts on commercial carbons lost more ECA with increasing temperature. A platinum/cobalt alloy on a low surface area carbon was demonstrated to be more stable to both carbon corrosion and metal area loss at temperatures up to 80 °C than platinum catalysts on commercial carbons, making this material an excellent candidate for higher temperature automotive operation.

  3. A Brassica napus PHT1 phosphate transporter, BnPht1;4, promotes phosphate uptake and affects roots architecture of transgenic Arabidopsis.

    PubMed

    Ren, Feng; Zhao, Cai-Zhi; Liu, Chun-Sen; Huang, Ke-Lin; Guo, Qian-Qian; Chang, Li-Li; Xiong, Huan; Li, Xue-Bao

    2014-12-01

    Phosphorus (P) is one of the essential nutrient elements for plant development. In this work, BnPht1;4 gene, encoding a phosphate transporter of PHT1 family, was isolated from Brassica napus. BnPht1;4 possesses the major characteristic of PHT1 high-affinity Pi transporters in plants, such as plasma-membrane localization and 12 transmembrane-spanning domains. Quantitative reverse-transcription PCR analysis and promoter activity assay showed BnPht1;4 was inert in plants under Pi sufficient conditions. However, expression of this gene was remarkably enhanced in roots under Pi deficient conditions. Interestingly, under low Pi conditions, its promoter activity is impaired in tips of elongated roots, suggesting that the high-affinity Pi transporter may be not involved in low Pi response at root tip area. The experimental results also indicated that BnPht1;4 induction by Pi deficiency is dependent on the existence of sugar. In 35S:BnPht1;4 transgenic Arabidopsis, the increase of Pi availability resulted in the change of root architecture under Pi deficient conditions, showing longer primary roots and lower lateral root density than that of wild type. By cis-element analysis, two P1BS and two W-box elements were found in BnPht1;4 promoter. Yeast one-hybrid assay indicated that PHR1 could bind to the BnPht1;4 promoter. P1BS elements in BnPht1;4 promoter are essential for BnPht1;4 induction in Pi starvation response. Furthermore, WRKY75 could bind to the BnPht1;4 promoter, in which W-box elements are important for this binding. These results indicated BnPht1;4 may be dually controlled by two family regulators under low Pi responses. Thus, our data on the regulative mechanism of high-affinity Pi transporter in Pi starvation response will be valuable for B. napus molecular agriculture. PMID:25194430

  4. Arabidopsis hybrid speciation processes

    PubMed Central

    Schmickl, Roswitha; Koch, Marcus A.

    2011-01-01

    The genus Arabidopsis provides a unique opportunity to study fundamental biological questions in plant sciences using the diploid model species Arabidopsis thaliana and Arabidopsis lyrata. However, only a few studies have focused on introgression and hybrid speciation in Arabidopsis, although polyploidy is a common phenomenon within this genus. More recently, there is growing evidence of significant gene flow between the various Arabidopsis species. So far, we know Arabidopsis suecica and Arabidopsis kamchatica as fully stabilized allopolyploid species. Both species evolved during Pleistocene glaciation and deglaciation cycles in Fennoscandinavia and the amphi-Beringian region, respectively. These hybrid studies were conducted either on a phylogeographic scale or reconstructed experimentally in the laboratory. In our study we focus at a regional and population level. Our research area is located in the foothills of the eastern Austrian Alps, where two Arabidopsis species, Arabidopsis arenosa and A. lyrata ssp. petraea, are sympatrically distributed. Our hypothesis of genetic introgression, migration, and adaptation to the changing environment during the Pleistocene has been confirmed: We observed significant, mainly unidirectional gene flow between the two species, which has given rise to the tetraploid A. lyrata. This cytotype was able to escape from the narrow ecological niche occupied by diploid A. lyrata ssp. petraea on limestone outcrops by migrating northward into siliceous areas, leaving behind a trail of genetic differentiation. PMID:21825128

  5. Molecular Physiological Analysis of the Two Plastidic ATP/ADP Transporters from Arabidopsis12

    PubMed Central

    Reiser, Jens; Linka, Nicole; Lemke, Lilia; Jeblick, Wolfgang; Neuhaus, H. Ekkehard

    2004-01-01

    Arabidopsis (Arabidopsis thaliana) possesses two isoforms of plastidic ATP/ADP transporters (AtNTT1 and AtNTT2) exhibiting similar biochemical properties. To analyze the function of both isoforms on the molecular level, we examined the expression pattern of both genes by northern-blot analysis and promoter-β-glucuronidase fusions. AtNTT1 represents a sugar-induced gene mainly expressed in stem and roots, whereas AtNTT2 is expressed in several Arabidopsis tissues with highest accumulation in developing roots and young cotyledons. Developing lipid-storing seeds hardly contained AtNTT1 or -2 transcripts. The absence of a functional AtNTT1 gene affected plant development only slightly, whereas AtNTT2∷T-DNA, AtNTT1-2∷T-DNA, and RNA interference (RNAi) plants showed retarded plant development, mainly characterized by a reduced ability to generate primary roots and a delayed chlorophyll accumulation in seedlings. Electron microscopic examination of chloroplast substructure also revealed an impaired formation of thylakoids in RNAi seedlings. Moreover, RNAi- and AtNTT1-2∷T-DNA plants showed reduced accumulation of the nuclear-encoded protein CP24 during deetiolation. Under short-day conditions reduced plastidic ATP import capacity correlates with a substantially reduced plant growth rate. This effect is absent under long-day conditions, strikingly indicating that nocturnal ATP import into chloroplasts is important. Plastidic ATP/ADP transport activity exerts significant control on lipid synthesis in developing Arabidopsis seeds. In total we made the surprising observation that plastidic ATP/ADP transport activity is not required to pass through the complete plant life cycle. However, plastidic ATP/ADP-transporter activity is required for both an undisturbed development of young tissues and a controlled cellular metabolism in mature leaves. PMID:15516503

  6. The Arabidopsis Circadian System

    PubMed Central

    McClung, C. Robertson; Salomé, Patrice A.; Michael, Todd P.

    2002-01-01

    Rhythms with periods of approximately 24 hr are widespread in nature. Those that persist in constant conditions are termed circadian rhythms and reflect the activity of an endogenous biological clock. Plants, including Arabidopsis, are richly rhythmic. Expression analysis, most recently on a genomic scale, indicates that the Arabidopsis circadian clock regulates a number of key metabolic pathways and stress responses. A number of sensitive and high-throughput assays have been developed to monitor the Arabidopsis clock. These assays have facilitated the identification of components of plant circadian systems through genetic and molecular biological studies. Although much remains to be learned, the framework of the Arabidopsis circadian system is coming into focus. Dedication This review is dedicated to the memory of DeLill Nasser, a wonderful mentor and an unwavering advocate of both Arabidopsis and circadian rhythms research. PMID:22303209

  7. The jiaoyao1 Mutant Is an Allele of korrigan1 That Abolishes Endoglucanase Activity and Affects the Organization of Both Cellulose Microfibrils and Microtubules in Arabidopsis[C][W

    PubMed Central

    Lei, Lei; Zhang, Tian; Strasser, Richard; Lee, Christopher M.; Gonneau, Martine; Mach, Lukas; Vernhettes, Samantha; Kim, Seong H.; J. Cosgrove, Daniel; Li, Shundai; Gu, Ying

    2014-01-01

    In higher plants, cellulose is synthesized by plasma membrane–localized cellulose synthase complexes (CSCs). Arabidopsis thaliana GH9A1/KORRIGAN1 is a membrane-bound, family 9 glycosyl hydrolase that is important for cellulose synthesis in both primary and secondary cell walls. Most previously identified korrigan1 mutants show severe phenotypes such as embryo lethality; therefore, the role of GH9A1 in cellulose synthesis remains unclear. Here, we report a novel A577V missense mutation, designated jiaoyao1 (jia1), in the second of the glycosyl hydrolase family 9 active site signature motifs in GH9A1. jia1 is defective in cell expansion in dark-grown hypocotyls, roots, and adult plants. Consistent with its defect in cell expansion, this mutation in GH9A1 resulted in reduced cellulose content and reduced CSC velocity at the plasma membrane. Green fluorescent protein–GH9A1 is associated with CSCs at multiple locations, including the plasma membrane, Golgi, trans-Golgi network, and small CESA-containing compartments or microtubule-associated cellulose synthase compartments, indicating a tight association between GH9A1 and CSCs. GH9A1A577V abolishes the endoglucanase activity of GH9A1 in vitro but does not affect its interaction with CESAs in vitro, suggesting that endoglucanase activity is important for cellulose synthesis. Interestingly, jia1 results in both cellulose microfibril and microtubule disorganization. Our study establishes the important role of endoglucanase in cellulose synthesis and cellulose microfibril organization in plants. PMID:24963054

  8. Arabidopsis BPM Proteins Function as Substrate Adaptors to a CULLIN3-Based E3 Ligase to Affect Fatty Acid Metabolism in Plants[W

    PubMed Central

    Chen, Liyuan; Lee, Joo Hyun; Weber, Henriette; Tohge, Takayuki; Witt, Sandra; Roje, Sanja; Fernie, Alisdair R.; Hellmann, Hanjo

    2013-01-01

    Regulation of transcriptional processes is a critical mechanism that enables efficient coordination of the synthesis of required proteins in response to environmental and cellular changes. Transcription factors require accurate activity regulation because they play a critical role as key mediators assuring specific expression of target genes. In this work, we show that CULLIN3-based E3 ligases have the potential to interact with a broad range of ETHYLENE RESPONSE FACTOR (ERF)/APETALA2 (AP2) transcription factors, mediated by MATH-BTB/POZ (for Meprin and TRAF [tumor necrosis factor receptor associated factor] homolog)-Broad complex, Tramtrack, Bric-a-brac/Pox virus and Zinc finger) proteins. The assembly with an E3 ligase causes degradation of their substrates via the 26S proteasome, as demonstrated for the WRINKLED1 ERF/AP2 protein. Furthermore, loss of MATH-BTB/POZ proteins widely affects plant development and causes altered fatty acid contents in mutant seeds. Overall, this work demonstrates a link between fatty acid metabolism and E3 ligase activities in plants and establishes CUL3-based E3 ligases as key regulators in transcriptional processes that involve ERF/AP2 family members. PMID:23792371

  9. 1,2-Dichloropropane

    Integrated Risk Information System (IRIS)

    1,2 - Dichloropropane ; CASRN 78 - 87 - 5 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinoge

  10. 1,2-Dichloroethane

    Integrated Risk Information System (IRIS)

    1,2 - Dichloroethane ; CASRN 107 - 06 - 2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinoge

  11. 1,2-Diphenylhydrazine

    Integrated Risk Information System (IRIS)

    1,2 - Diphenylhydrazine ; CASRN 122 - 66 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcin

  12. 1,2-Dichlorobenzene

    Integrated Risk Information System (IRIS)

    1,2 - Dichlorobenzene ; CASRN 95 - 50 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinoge

  13. 1,2-Dibromoethane

    Integrated Risk Information System (IRIS)

    1,2 - Dibromoethane ; CASRN 106 - 93 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogen

  14. The transcript elongation factor SPT4/SPT5 is involved in auxin-related gene expression in Arabidopsis

    PubMed Central

    Dürr, Julius; Lolas, Ihab B.; Sørensen, Brian B.; Schubert, Veit; Houben, Andreas; Melzer, Michael; Deutzmann, Rainer; Grasser, Marion; Grasser, Klaus D.

    2014-01-01

    The heterodimeric complex SPT4/SPT5 is a transcript elongation factor (TEF) that directly interacts with RNA polymerase II (RNAPII) to regulate messenger RNA synthesis in the chromatin context. We provide biochemical evidence that in Arabidopsis, SPT4 occurs in a complex with SPT5, demonstrating that the SPT4/SPT5 complex is conserved in plants. Each subunit is encoded by two genes SPT4-1/2 and SPT5-1/2. A mutant affected in the tissue-specifically expressed SPT5-1 is viable, whereas inactivation of the generally expressed SPT5-2 is homozygous lethal. RNAi-mediated downregulation of SPT4 decreases cell proliferation and causes growth reduction and developmental defects. These plants display especially auxin signalling phenotypes. Consistently, auxin-related genes, most strikingly AUX/IAA genes, are downregulated in SPT4–RNAi plants that exhibit an enhanced auxin response. In Arabidopsis nuclei, SPT5 clearly localizes to the transcriptionally active euchromatin, and essentially co-localizes with transcribing RNAPII. Typical for TEFs, SPT5 is found over the entire transcription unit of RNAPII-transcribed genes. In SPT4–RNAi plants, elevated levels of RNAPII and SPT5 are detected within transcribed regions (including those of downregulated genes), indicating transcript elongation defects in these plants. Therefore, SPT4/SPT5 acts as a TEF in Arabidopsis, regulating transcription during the elongation stage with particular impact on the expression of certain auxin-related genes. PMID:24497194

  15. Brief Report: Macrophage Activation in HIV-2-Infected Patients Is Less Affected by Antiretroviral Treatment-sCD163 in HIV-1, HIV-2, and HIV-1/2 Dually Infected Patients.

    PubMed

    Hønge, Bo L; Andersen, Morten N; Jespersen, Sanne; Medina, Candida; Correira, Faustino G; Jakobsen, Martin R; Laursen, Alex; Erikstrup, Christian; Møller, Holger J; Wejse, Christian

    2016-07-01

    The course of disease among HIV-2, HIV-1, and HIV-1/2 dually infected patients is different. We investigated the macrophage activation marker soluble CD163 (sCD163) dynamics in 212 HIV-1, HIV-2, and HIV-1/2 dually infected patients. There were no differences in sCD163 levels at baseline or during follow-up without antiretroviral therapy (ART). At follow-up on ART, median sCD163 levels were decreased for HIV-1-infected patients (P < 0.001), but not among HIV-2 (P = 0.093) or HIV-1/2 dually infected patients (P = 0.145). The larger decrease in sCD163 levels among HIV-1-infected patients during ART may indicate an HIV type-dependent differential effect of ART on macrophage activation during HIV infection. PMID:26825178

  16. Rice Blast Fungus (Magnaporthe oryzae) Infects Arabidopsis via a Mechanism Distinct from That Required for the Infection of Rice1[W][OA

    PubMed Central

    Park, Ju-Young; Jin, Jianming; Lee, Yin-Won; Kang, Seogchan; Lee, Yong-Hwan

    2009-01-01

    Magnaporthe oryzae is a hemibiotrophic fungal pathogen that causes rice (Oryza sativa) blast. Although M. oryzae as a whole infects a wide variety of monocotyledonous hosts, no dicotyledonous plant has been reported as a host. We found that two rice pathogenic strains of M. oryzae, KJ201 and 70-15, interacted differentially with 16 ecotypes of Arabidopsis (Arabidopsis thaliana). Strain KJ201 infected all ecotypes with varying degrees of virulence, whereas strain 70-15 caused no symptoms in certain ecotypes. In highly susceptible ecotypes, small chlorotic lesions appeared on infected leaves within 3 d after inoculation and subsequently expanded across the affected leaves. The fungus produced spores in susceptible ecotypes but not in resistant ecotypes. Fungal cultures recovered from necrotic lesions caused the same symptoms in healthy plants, satisfying Koch's postulates. Histochemical analyses showed that infection by the fungus caused an accumulation of reactive oxygen species and eventual cell death. Similar to the infection process in rice, the fungus differentiated to form appressorium and directly penetrated the leaf surface in Arabidopsis. However, the pathogenic mechanism in Arabidopsis appears distinct from that in rice; three fungal genes essential for pathogenicity in rice played only limited roles in causing disease symptoms in Arabidopsis, and the fungus seems to colonize Arabidopsis as a necrotroph through the secretion of phytotoxic compounds, including 9,12-octadecadienoic acid. Expression of PR-1 and PDF1.2 was induced in response to infection by the fungus, suggesting the activation of salicylic acid- and jasmonic acid/ethylene-dependent signaling pathways. However, the roles of these signaling pathways in defense against M. oryzae remain unclear. In combination with the wealth of genetic and genomic resources available for M. oryzae, this newly established pathosystem allows comparison of the molecular and cellular mechanisms underlying

  17. Platelet-derived growth factor (PDGF)-induced activation of Erk5 MAP-kinase is dependent on Mekk2, Mek1/2, PKC and PI3-kinase, and affects BMP signaling.

    PubMed

    Tsioumpekou, Maria; Papadopoulos, Natalia; Burovic, Fatima; Heldin, Carl-Henrik; Lennartsson, Johan

    2016-09-01

    Platelet-derived growth factor-BB (PDGF-BB) binds to its tyrosine kinase receptors (PDGFRs) and stimulates mitogenicity and survival of cells of mesenchymal origin. Activation of PDGFRs initiates a number of downstream signaling pathways, including phosphatidyl 3'-inositol kinase (PI3-kinase), phospholipase Cγ and MAP kinase pathways. In this report, we show that Erk5 MAP kinase is activated in response to PDGF-BB in the smooth muscle cell line MOVAS in a manner dependent on Mekk2, Mek1/2, Mek5, PI3-kinase and protein kinase C (PKC). The co-operation of Mek1/2 and Mekk2 in the activation of Erk5, suggests a close co-regulation between the Erk1/2 and Erk5 MAP kinase pathways. Furthermore, we found that classical PKCs are important for Erk5 activation. In addition, we found that PKCζ interacts with Erk5 and may exert a negative feed-back effect. We observed no nuclear accumulation of Erk5 in response to PDGF-BB stimulation, however, we identified a mechanism by which cytoplasmic Erk5 influences gene expression; Erk5 was essential for PDGF-BB-mediated Smad1/5/8 signaling by stimulating release and/or activation of bone morphogenetic protein(s) (BMPs). Thus, PDGF-BB-induced Erk5 activation involves parallel stimulatory and inhibitory pathways and promotes Smad1/5/8 signaling. PMID:27339033

  18. Plastidial Glycolytic Glyceraldehyde-3-Phosphate Dehydrogenase Is an Important Determinant in the Carbon and Nitrogen Metabolism of Heterotrophic Cells in Arabidopsis.

    PubMed

    Anoman, Armand D; Muñoz-Bertomeu, Jesús; Rosa-Téllez, Sara; Flores-Tornero, María; Serrano, Ramón; Bueso, Eduardo; Fernie, Alisdair R; Segura, Juan; Ros, Roc

    2015-11-01

    This study functionally characterizes the Arabidopsis (Arabidopsis thaliana) plastidial glycolytic isoforms of glyceraldehyde-3-phosphate dehydrogenase (GAPCp) in photosynthetic and heterotrophic cells. We expressed the enzyme in gapcp double mutants (gapcp1gapcp2) under the control of photosynthetic (Rubisco small subunit RBCS2B [RBCS]) or heterotrophic (phosphate transporter PHT1.2 [PHT]) cell-specific promoters. Expression of GAPCp1 under the control of RBCS in gapcp1gapcp2 had no significant effect on the metabolite profile or growth in the aerial part (AP). GAPCp1 expression under the control of the PHT promoter clearly affected Arabidopsis development by increasing the number of lateral roots and having a major effect on AP growth and metabolite profile. Our results indicate that GAPCp1 is not functionally important in photosynthetic cells but plays a fundamental role in roots and in heterotrophic cells of the AP. Specifically, GAPCp activity may be required in root meristems and the root cap for normal primary root growth. Transcriptomic and metabolomic analyses indicate that the lack of GAPCp activity affects nitrogen and carbon metabolism as well as mineral nutrition and that glycerate and glutamine are the main metabolites responding to GAPCp activity. Thus, GAPCp could be an important metabolic connector of glycolysis with other pathways, such as the phosphorylated pathway of serine biosynthesis, the ammonium assimilation pathway, or the metabolism of γ-aminobutyrate, which in turn affect plant development. PMID:26134167

  19. Crystallization of DIR1, a LTP2-like resistance signalling protein from Arabidopsis thaliana

    SciTech Connect

    Lascombe, Marie-Bernard; Buhot, Nathalie; Bakan, Bénédicte; Marion, Didier; Blein, Jean Pierre; Lamb, Chris J.; Prangé, Thierry

    2006-07-01

    DIR1, a putative LTP2 protein from Arabidopsis thaliana implicated in systemic acquired resistance in planta, has been crystallized in space group P2{sub 1}2{sub 1}2{sub 1} with one molecule per asymmetric unit. DIR1, a putative LTP2 protein from Arabidopsis thaliana implicated in systemic acquired resistance in planta, has been crystallized in space group P2{sub 1}2{sub 1}2{sub 1} with one molecule per asymmetric unit. The crystals diffract to a resolution of 1.6 Å.

  20. Cysteine-Generated Sulfide in the Cytosol Negatively Regulates Autophagy and Modulates the Transcriptional Profile in Arabidopsis[W

    PubMed Central

    Álvarez, Consolación; García, Irene; Moreno, Inmaculada; Pérez-Pérez, María Esther; Crespo, José L.; Romero, Luis C.; Gotor, Cecilia

    2012-01-01

    In Arabidopsis thaliana, DES1 is the only identified l-Cysteine desulfhydrase located in the cytosol, and it is involved in the degradation of cysteine and the concomitant production of H2S in this cell compartment. Detailed characterization of the T-DNA insertion mutants des1-1 and des1-2 has provided insight into the role of sulfide metabolically generated in the cytosol as a signaling molecule. Mutations of L-CYS DESULFHYDRASE 1 (DES1) impede H2S generation in the Arabidopsis cytosol and strongly affect plant metabolism. Senescence-associated vacuoles are detected in mesophyll protoplasts of des1 mutants. Additionally, DES1 deficiency promotes the accumulation and lipidation of the ATG8 protein, which is associated with the process of autophagy. The transcriptional profile of the des1-1 mutant corresponds to its premature senescence and autophagy-induction phenotypes, and restoring H2S generation has been shown to eliminate the phenotypic defects of des1 mutants. Moreover, sulfide is able to reverse ATG8 accumulation and lipidation, even in wild-type plants when autophagy is induced by carbon starvation, suggesting a general effect of sulfide on autophagy regulation that is unrelated to sulfur or nitrogen limitation stress. Our results suggest that cysteine-generated sulfide in the cytosol negatively regulates autophagy and modulates the transcriptional profile of Arabidopsis. PMID:23144183

  1. Starch Metabolism in Arabidopsis

    PubMed Central

    Streb, Sebastian; Zeeman, Samuel C.

    2012-01-01

    Starch is the major non-structural carbohydrate in plants. It serves as an important store of carbon that fuels plant metabolism and growth when they are unable to photosynthesise. This storage can be in leaves and other green tissues, where it is degraded during the night, or in heterotrophic tissues such as roots, seeds and tubers, where it is stored over longer time periods. Arabidopsis accumulates starch in many of its tissues, but mostly in its leaves during the day. It has proven to be a powerful genetic system for discovering how starch is synthesised and degraded, and new proteins and processes have been discovered. Such work has major significance for our starch crops, whose yield and quality could be improved by the application of this knowledge. Research into Arabidopsis starch metabolism has begun to reveal how its daily turnover is integrated into the rest of metabolism and adapted to the environmental conditions. Furthermore, Arabidopsis mutant lines deficient in starch metabolism have been employed as tools to study other biological processes ranging from sugar sensing to gravitropism and flowering time control. This review gives a detailed account of the use of Arabidopsis to study starch metabolism. It describes the major discoveries made and presents an overview of our understanding today, together with some as-yet unresolved questions. PMID:23393426

  2. Overexpression of the lily p70(s6k) gene in Arabidopsis affects elongation of flower organs and indicates TOR-dependent regulation of AP3, PI and SUP translation.

    PubMed

    Tzeng, Tsai-Yu; Kong, Lih-Ren; Chen, Chun-Hung; Shaw, Chih-Chi; Yang, Chang-Hsien

    2009-09-01

    The p70 ribosomal S6 kinase (p70(s6k)) signaling pathway plays a key role in regulating the cell cycle via translational regulation of specific 5'TOP mRNAs. However, the function of this signaling pathway is still poorly understood in plants. Ectopic expression of the lily putative p70(s6k) gene, LS6K1, resulted in up-regulation of NAP (NAC-LIKE, ACTIVATED BY AP3/PI) and PISTILLATA (PI) expression, and significantly inhibited cell expansion for petals and stamens, resulting in the male sterility phenotype in transgenic Arabidopsis. Sequence analysis revealed that the genes involved in petal and stamen development, such as APETALA3 (AP3), PI and SUPERMAN (SUP), probably encode 5'TOP mRNAs. Green fluorescent protein (GFP), fused to oligopyrimidine tract sequences that were identified in the 5'-untranslated region (UTR) of AP3, PI and SUP, was translationally regulated in human cells in response to mitogen stimulation and inhibition by the macrolide antibiotic rapamycin. Furthermore, 35S::LS6K1 significantly up-regulated beta-glucuronidase (GUS) activity in the flower buds of transgenic plants carrying the GUS transgene fused to the AP3 promoter and the 5' UTR. These results have identified a novel role for the p70(s6k) gene in regulating cell division and the expansion of petals and stamens by translational regulation of the 5'TOP mRNAs once ectopically expressed in Arabidopsis. PMID:19651701

  3. Open-System Magma Reservoir Affects Gas Segregation, Vesiculation, Fragmentation and Lava/Pyroclast Dispersal During the 1.2 km-deep 2007-2010 Submarine Eruption at West Mata Volcano

    NASA Astrophysics Data System (ADS)

    Rubin, K. H.; Clague, D. A.; Embley, R. W.; Hellebrand, E.; Soule, S. A.; Resing, J.

    2014-12-01

    West Mata, a small, active rear-arc volcano in the NE Lau Basin, erupts crystal and gas rich boninite magma. Eruptions were observed at the summit (1.2 km water depth) during 5 ROV Jason dives in 2009 (the deepest erupting submarine volcano observed to date). Subsequent ROV and ship-based bathymetric mapping revealed that a pit crater formed and the summit eruption ceased in 2010, with roughly simultaneous eruptions along the SW rift zone. During the summit eruption, a combination of water depth, H2O-CO2-rich and high crystallinity magma, a split in the conduit to feed two vent sites, and waxing/waning magma supply led to a range of effusive/explosive eruption styles and volcanic deposit types. The 2-3 vent Hades cluster and the lone Prometheus vent had different eruption characteristics. Petrographic, petrologic and geochemical studies of erupted products indicate a change in magma composition in time and space over a period of 3.5 yrs, suggesting a small, open-system magma reservoir within the volcano. Prometheus (1174m depth) produced mostly pyroclastic material during our observations (e.g., highly vesicular glowing fluidal ejecta that cooled in the water column and rounded recycled dense clasts), but sampling and 210Po radiometric dating show that several months prior pillowed lava flows, subsequently covered with cm-sized pyroclasts, had flowed >50m from the vent. In contrast, vents at Hades (1200m depth) cycled between lava production and vigorous degassing, 10-20m high fire fountains and bursts of glowing lava-skinned bubbles, the products of which froze/broke in the water column, forming unstable cones of spatter and scoria near the vents. We hypothesize that bubbles collapse rather than form lava balloons because of skin brittleness (from high crystal content) and hydrostatic pressure. Clast settling times and patterns suggest >100m water column rise height for 10+ cm-sized fragments. Pillow flows were also observed to be issuing from the base of the

  4. Evaluation of processes affecting 1,2-dibromo-3-chloropropane (DBCP) concentrations in ground water in the eastern San Joaquin Valley, California : analysis of chemical data and ground-water flow and transport simulations

    USGS Publications Warehouse

    Burow, Karen R.; Panshin, Sandra Y.; Dubrovsky, Neil H.; Vanbrocklin, David; Fogg, Graham E.

    1999-01-01

    A conceptual two-dimensional numerical flow and transport modeling approach was used to test hypotheses addressing dispersion, transformation rate, and in a relative sense, the effects of ground- water pumping and reapplication of irrigation water on DBCP concentrations in the aquifer. The flow and transport simulations, which represent hypothetical steady-state flow conditions in the aquifer, were used to refine the conceptual understanding of the aquifer system rather than to predict future concentrations of DBCP. Results indicate that dispersion reduces peak concentrations, but this process alone does not account for the apparent decrease in DBCP concentrations in ground water in the eastern San Joaquin Valley. Ground-water pumping and reapplication of irrigation water may affect DBCP concentrations to the extent that this process can be simulated indirectly using first-order decay. Transport simulation results indicate that the in situ 'effective' half-life of DBCP caused by processes other than dispersion and transformation to BAA could be on the order of 6 years.

  5. Trichome morphogenesis in Arabidopsis.

    PubMed Central

    Schwab, B; Folkers, U; Ilgenfritz, H; Hülskamp, M

    2000-01-01

    Trichomes (plant hairs) in Arabidopsis thaliana are large non-secreting epidermal cells with a characteristic three-dimensional architecture. Because trichomes are easily accessible to a combination of genetic, cell biological and molecular methods they have become an ideal model system to study various aspects of plant cell morphogenesis. In this review we will summarize recent progress in the understanding of trichome morphogenesis. PMID:11128981

  6. Effect of cultural conditions on the seed-to-seed growth of Arabidopsis and Cardamine - A study of growth rates and reproductive development as affected by test tube seals

    NASA Technical Reports Server (NTRS)

    Hoshizaki, T.

    1982-01-01

    The effects of test tube seals on the growth, flowering, and seed pod formation of Arabidopsis thaliana (L.) Heynh., mouse ear cress, and Cardamine oligosperma Nutt, bitter cress, are studied in order to assess the conditions used in weightlessness experiments. Among other results, it is found that the growth (height) and flowering (date of bud appearance) were suppressed in mouse ear cress in tubes sealed with Saran. Seed pod formation which occurred by day 45 in open-to-air controls, was still lacking in the sealed plants even up to day 124. The growth and flowering of bitter cress were also suppressed by the Saran seal, although up to day 55 the Saran-sealed plants were taller. It is suggested that atmospheric composition was the cause of the suppression of growth, flowering, and seed pod development in these plants, since the mouse ear cress renewed their growth and then set seed pods after the Saran seal was ruptured.

  7. Sodium Influx and Accumulation in Arabidopsis1

    PubMed Central

    Essah, Pauline A.; Davenport, Romola; Tester, Mark

    2003-01-01

    Arabidopsis is frequently used as a genetic model in plant salt tolerance studies, however, its physiological responses to salinity remain poorly characterized. This study presents a characterization of initial Na+ entry and the effects of Ca2+ on plant growth and net Na+ accumulation in saline conditions. Unidirectional Na+ influx was measured carefully using very short influx times in roots of 12-d-old seedlings. Influx showed three components with distinct sensitivities to Ca2+, diethylpyrocarbonate, and osmotic pretreatment. Pharmacological agents and known mutants were used to test the contribution of different transport pathways to Na+ uptake. Influx was stimulated by 4-aminobutyric acid and glutamic acid; was inhibited by flufenamate, quinine, and cGMP; and was insensitive to modulators of K+ and Ca2+ channels. Influx did not differ from wild type in akt1 and hkt1 insertional mutants. These data suggested that influx was mediated by several different types of nonselective cation channels. Na+ accumulation in plants grown in 50 mm NaCl was strongly reduced by increasing Ca2+ activity (from 0.05-3.0 mm), and plant survival was improved. However, plant biomass was not affected by shoot Na+ concentration, suggesting that in Arabidopsis Na+ toxicity is not dependent on shoot Na+ accumulation. These data suggest that Arabidopsis is a good model for investigation of Na+ transport, but may be of limited utility as a model for the study of Na+ toxicity. PMID:12970496

  8. 14 CFR 1.2 - Abbreviations and symbols.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... affecting § 1.2, see the List of CFR Sections Affected, which appears in the Finding Aids section of the... above ground level. ALS means approach light system. APU means auxiliary power unit. ASR means...

  9. Arabidopsis ATAF1 enhances the tolerance to salt stress and ABA in transgenic rice.

    PubMed

    Liu, Yongchang; Sun, Jie; Wu, Yaorong

    2016-09-01

    NAC (NAM, ATAF1/2, CUC2) transcription factors are plant-specific and have diverse functions in many plant developmental processes and responses to stress. In our previous study, we found that the expression of ATAF1, an Arabidopsis NAC gene, was obviously induced by high-salinity and abscisic acid (ABA). The overexpression of ATAF1 in Arabidopsis increased plant sensitivity to ABA and salt. To investigate whether ATAF1 affects the sensitivity of monocotyledon plant to salt and ABA, ATAF1 transgenic rice were generated. Transgenic rice exhibited significantly improved salt tolerance and insensitivity to ABA. The results of real-time PCR showed that ATAF1 overexpression in rice elevated the transcription of OsLEA3, OsSalT1 and OsPM1, which are stress-associated genes. Our results indicate that ATAF1 plays an important role in response to salt stress and may be utilized to improve the salt tolerance of rice. PMID:27216423

  10. Tissue-specific clocks in Arabidopsis show asymmetric coupling

    PubMed Central

    Endo, Motomu; Shimizu, Hanako; Nohales, Maria A.; Araki, Takashi; Kay, Steve A.

    2014-01-01

    Many organisms rely on a circadian clock system to adapt to daily and seasonal environmental changes. The mammalian circadian clock consists of a central clock in the suprachiasmatic nucleus that is tightly coupled and synchronizes other clocks in peripheral tissues1, 2. Plants also have a circadian clock, but plant circadian clock function has long been assumed to be uncoupled3. Only a few studies have been able to show a weak, local coupling among cells4, 5, 6, 7. Here, by implementing two novel techniques, we have performed a comprehensive tissue-specific analysis of leaf tissues, and we have discovered that the vasculature and mesophyll clocks asymmetrically regulate each other in Arabidopsis. The circadian clock in the vasculature has characteristics distinct from other tissues, cycles robustly without environmental cues, and affects circadian clock regulation in other tissues. Furthermore, we found that vasculature-enriched genes that are rhythmic are preferentially expressed in the evening, whereas rhythmic mesophyll-enriched genes tend to be expressed in the morning. Our results set the stage for a deeper understanding of how the vasculature circadian clock in plants regulates key physiological responses such as flowering time. PMID:25363766

  11. Arabidopsis peroxisome proteomics

    PubMed Central

    Bussell, John D.; Behrens, Christof; Ecke, Wiebke; Eubel, Holger

    2013-01-01

    The analytical depth of investigation of the peroxisomal proteome of the model plant Arabidopsis thaliana has not yet reached that of other major cellular organelles such as chloroplasts or mitochondria. This is primarily due to the difficulties associated with isolating and obtaining purified samples of peroxisomes from Arabidopsis. So far only a handful of research groups have been successful in obtaining such fractions. To make things worse, enriched peroxisome fractions frequently suffer from significant organellar contamination, lowering confidence in localization assignment of the identified proteins. As with other cellular compartments, identification of peroxisomal proteins forms the basis for investigations of the dynamics of the peroxisomal proteome. It is therefore not surprising that, in terms of functional analyses by proteomic means, peroxisomes are lagging considerably behind chloroplasts or mitochondria. Alternative strategies are needed to overcome the obstacle of hard-to-obtain organellar fractions. This will help to close the knowledge gap between peroxisomes and other organelles and provide a full picture of the physiological pathways shared between organelles. In this review, we briefly summarize the status quo and discuss some of the methodological alternatives to classic organelle proteomic approaches. PMID:23630535

  12. Arabidopsis mutants impaired in cosuppression.

    PubMed Central

    Elmayan, T; Balzergue, S; Béon, F; Bourdon, V; Daubremet, J; Guénet, Y; Mourrain, P; Palauqui, J C; Vernhettes, S; Vialle, T; Wostrikoff, K; Vaucheret, H

    1998-01-01

    Post-transcriptional gene silencing (cosuppression) results in the degradation of RNA after transcription. A transgenic Arabidopsis line showing post-transcriptional silencing of a 35S-uidA transgene and uidA-specific methylation was mutagenized using ethyl methanesulfonate. Six independent plants were isolated in which uidA mRNA accumulation and beta-glucuronidase activity were increased up to 3500-fold, whereas the transcription rate of the 35S-uidA transgene was increased only up to threefold. These plants each carried a recessive monogenic mutation that is responsible for the release of silencing. These mutations defined two genetic loci, called sgs1 and sgs2 (for suppressor of gene silencing). Transgene methylation was distinctly modified in sgs1 and sgs2 mutants. However, methylation of centromeric repeats was not affected, indicating that sgs mutants differ from ddm (for decrease in DNA methylation) and som (for somniferous) mutants. Indeed, unlike ddm and som mutations, sgs mutations were not able to release transcriptional silencing of a 35S-hpt transgene. Conversely, both sgs1 and sgs2 mutations were able to release cosuppression of host Nia genes and 35S-Nia2 transgenes. These results therefore indicate that sgs mutations act in trans to impede specifically transgene-induced post-transcriptional gene silencing. PMID:9761800

  13. Type-f thioredoxins have a role in the short-term activation of carbon metabolism and their loss affects growth under short-day conditions in Arabidopsis thaliana

    PubMed Central

    Naranjo, Belén; Diaz-Espejo, Antonio; Lindahl, Marika; Cejudo, Francisco Javier

    2016-01-01

    Redox regulation plays a central role in the adaptation of chloroplast metabolism to light. Extensive biochemical analyses in vitro have identified f-type thioredoxins (Trxs) as the most important catalysts for light-dependent reduction and activation of the enzymes of the Calvin–Benson cycle. However, the precise function of type f Trxs in vivo and their impact on plant growth are still poorly known. To address this issue we have generated an Arabidopsis thaliana double knock-out mutant, termed trxf1f2, devoid of both f1 and f2 Trxs. Despite the essential function previously proposed for f-type Trxs, the visible phenotype of the trxf1f2 double mutant was virtually indistinguishable from the wild type when grown under a long-day photoperiod. However, the Trx f-deficient plants showed growth inhibition under a short-day photoperiod which was not rescued at high light intensity. The absence of f-type Trxs led to significantly lower photosynthetic electron transport rates and higher levels of non-photochemical energy quenching. Notably, the Trx f null mutant suffered from a shortage of photosystem I electron acceptors and delayed activation of carbon dioxide fixation following a dark–light transition. Two redox-regulated Calvin–Benson cycle enzymes, fructose 1,6-bisphosphatase (FBPase) and Rubisco activase, showed retarded and incomplete reduction in the double mutant upon illumination, compared with wild-type plants. These results show that the function of f-type Trxs in the rapid activation of carbon metabolism in response to light is not entirely compensated for by additional plastid redox systems, and suggest that these Trxs have an important role in the light adjustment of photosynthetic metabolism. PMID:26842981

  14. Type-f thioredoxins have a role in the short-term activation of carbon metabolism and their loss affects growth under short-day conditions in Arabidopsis thaliana.

    PubMed

    Naranjo, Belén; Diaz-Espejo, Antonio; Lindahl, Marika; Cejudo, Francisco Javier

    2016-03-01

    Redox regulation plays a central role in the adaptation of chloroplast metabolism to light. Extensive biochemical analyses in vitro have identified f-type thioredoxins (Trxs) as the most important catalysts for light-dependent reduction and activation of the enzymes of the Calvin-Benson cycle. However, the precise function of type f Trxs in vivo and their impact on plant growth are still poorly known. To address this issue we have generated an Arabidopsis thaliana double knock-out mutant, termed trxf1f2, devoid of both f1 and f2 Trxs. Despite the essential function previously proposed for f-type Trxs, the visible phenotype of the trxf1f2 double mutant was virtually indistinguishable from the wild type when grown under a long-day photoperiod. However, the Trx f-deficient plants showed growth inhibition under a short-day photoperiod which was not rescued at high light intensity. The absence of f-type Trxs led to significantly lower photosynthetic electron transport rates and higher levels of non-photochemical energy quenching. Notably, the Trx f null mutant suffered from a shortage of photosystem I electron acceptors and delayed activation of carbon dioxide fixation following a dark-light transition. Two redox-regulated Calvin-Benson cycle enzymes, fructose 1,6-bisphosphatase (FBPase) and Rubisco activase, showed retarded and incomplete reduction in the double mutant upon illumination, compared with wild-type plants. These results show that the function of f-type Trxs in the rapid activation of carbon metabolism in response to light is not entirely compensated for by additional plastid redox systems, and suggest that these Trxs have an important role in the light adjustment of photosynthetic metabolism. PMID:26842981

  15. Transgenic Arabidopsis Gene Expression System

    NASA Technical Reports Server (NTRS)

    Ferl, Robert; Paul, Anna-Lisa

    2009-01-01

    The Transgenic Arabidopsis Gene Expression System (TAGES) investigation is one in a pair of investigations that use the Advanced Biological Research System (ABRS) facility. TAGES uses Arabidopsis thaliana, thale cress, with sensor promoter-reporter gene constructs that render the plants as biomonitors (an organism used to determine the quality of the surrounding environment) of their environment using real-time nondestructive Green Fluorescent Protein (GFP) imagery and traditional postflight analyses.

  16. Arabidopsis gene expression patterns are altered during spaceflight

    NASA Astrophysics Data System (ADS)

    Paul, Anna-Lisa; Popp, Michael P.; Gurley, William B.; Guy, Charles; Norwood, Kelly L.; Ferl, Robert J.

    The exposure of Arabidopsis thaliana (Arabidopsis) plants to spaceflight environments results in differential gene expression. A 5-day mission on orbiter Columbia in 1999 (STS-93) carried transgenic Arabidopsis plants engineered with a transgene composed of the alcohol dehydrogenase (Adh) gene promoter linked to the β-Glucuronidase (GUS) reporter gene. The plants were used to evaluate the effects of spaceflight on gene expression patterns initially by using the Adh/GUS transgene to address specifically the possibility that spaceflight induces a hypoxic stress response (Paul, A.L., Daugherty, C.J., Bihn, E.A., Chapman, D.K., Norwood, K.L., Ferl, R.J., 2001. Transgene expression patterns indicate that spaceflight affects stress signal perception and transduction in arabidopsis, Plant Physiol. 126, 613-621). As a follow-on to the reporter gene analysis, we report here the evaluation of genome-wide patterns of native gene expression within Arabidopsis shoots utilizing the Agilent DNA array of 21,000 Arabidopsis genes. As a control for the veracity of the array analyses, a selection of genes was further characterized with quantitative Real-Time RT PCR (ABI - Taqman®). Comparison of the patterns of expression for arrays probed with RNA isolated from plants exposed to spaceflight compared to RNA isolated from ground control plants revealed 182 genes that were differentially expressed in response to the spaceflight mission by more than 4-fold, and of those only 50 genes were expressed at levels chosen to support a conservative change call. None of the genes that are hallmarks of hypoxic stress were induced to this level. However, genes related to heat shock were dramatically induced - but in a pattern and under growth conditions that are not easily explained by elevated temperatures. These gene expression data are discussed in light of current models for plant responses to the spaceflight environment and with regard to potential future spaceflight experiment

  17. Expression of BvGLP-1 encoding a germin-like protein from sugar beet in Arabidopsis thaliana leads to resistance against phytopathogenic fungi.

    PubMed

    Knecht, Katrin; Seyffarth, Monique; Desel, Christine; Thurau, Tim; Sherameti, Irena; Lou, Binggan; Oelmüller, Ralf; Cai, Daguang

    2010-04-01

    Nematode (Heterodera schachtii) resistance in sugar beet (Beta vulgaris) is controlled by a single dominant resistance gene, Hs1(pro-1). BvGLP-1 was cloned from resistant sugar beet. The BvGLP-1 messenger (m)RNA is highly upregulated in the resistant plants after nematode infection, suggesting its role in the Hs1(pro-1) mediated resistance. BvGLP-1 exhibits sequence homology to a set of plant germin-like proteins (GLP), from which several have proved to be functional in plant basal or defense resistance against fungal pathogens. To test whether BvGLP-1 is also involved in the plant-fungus interaction, we transferred BvGLP-1 into Arabidopsis and challenged the transgenic plants with the pathogenic fungi Verticillium longisporum and Rhizoctonia solani as well as with the beneficial endophytic fungus Piriformospora indica. The expression of BvGLP-1 in Arabidopsis elevated the H(2)O(2) content and conferred significant resistance to V. longisporum and R. solani but did not affect the beneficial interaction with P. indica in seedlings. Microscopic observations revealed a dramatic reduction in the amount of hyphae of the pathogenic fungi on the root surface as well as of fungal mycelium developed inside the roots of transgenic Arabidopsis compared with wild-type plants. Molecular analysis demonstrated that the BvGLP-1 expression in Arabidopsis constitutively activates the expression of a subset of plant defense-related proteins such as PR-1 to PR-4 and PDF1.2 but not PDF2.1 and PDF2.3. In contrast, the PDF2.1 mRNA level was downregulated. These data suggest an important role of BvGLP-1 in establishment of plant defense responses, which follow specific signaling routes that diverge from those induced by the beneficial fungus. PMID:20192832

  18. An Arabidopsis callose synthase.

    PubMed

    Ostergaard, Lars; Petersen, Morten; Mattsson, Ole; Mundy, John

    2002-08-01

    Beta-1,3-glucan polymers are major structural components of fungal cell walls, while cellulosic beta-1,4-glucan is the predominant polysaccharide in plant cell walls. Plant beta-1,3-glucan, called callose, is produced in pollen and in response to pathogen attack and wounding, but it has been unclear whether callose synthases can also produce cellulose and whether plant cellulose synthases may also produce beta-1,3-glucans. We describe here an Arabidopsis gene, AtGsl5, encoding a plasma membrane-localized protein homologous to yeast beta-1,3-glucan synthase whose expression partially complements a yeast beta-1,3-glucan synthase mutant. AtGsl5 is developmentally expressed at highest levels in flowers, consistent with flowers having high beta-1,3-glucan synthase activities for deposition of callose in pollen. A role for AtGsl5 in callose synthesis is also indicated by AtGsl5 expression in the Arabidopsis mpk4 mutant which exhibits systemic acquired resistance (SAR), elevated beta-1,3-glucan synthase activity, and increased callose levels. In addition, AtGsl5 is a likely target of salicylic acid (SA)-dependent SAR, since AtGsl5 mRNA accumulation is induced by SA in wild-type plants, while expression of the nahG salicylate hydroxylase reduces AtGsl5 mRNA levels in the mpk4 mutant. These results indicate that AtGsl5 is likely involved in callose synthesis in flowering tissues and in the mpk4 mutant. PMID:12081364

  19. Auxin polar transport in arabidopsis under simulated microgravity conditions - relevance to growth and development

    NASA Astrophysics Data System (ADS)

    Miyamoto, K.; Oka, M.; Yamamoto, R.; Masuda, Y.; Hoson, T.; Kamisaka, S.; Ueda, J.

    1999-01-01

    Activity of auxin polar transport in inflorescence axes of Arabidopsis thaliana grown under simulated microgravity conditions was studied in relation to the growth and development. Seeds were germinated and allowed to grow on an agar medium in test tubes on a horizontal clinostat. Horizontal clinostat rotation substantially reduced the growth of inflorescence axes and the productivity of seeds of Arabidopsis thaliana (ecotypes Landsberg erecta and Columbia), although it little affected seed germination, development of rosette leaves and flowering. The activity of auxin polar transport in inflorescence axes decreased when Arabidopsis plants were grown on a horizontal clinostat from germination stage, being ca. 60% of 1 g control. On the other hand, the auxin polar transport in inflorescence axes of Arabidopsis grown in 1 g conditions was not affected when the segments were exposed to various gravistimuli, including 3-dimensional clinorotation, during transport experiments. Pin-formed mutant of Arabidopsis, having a unique structure of the inflorescence axis with no flower and extremely low levels of the activity of auxin polar transport in inflorescence axes and endogenous auxin, did not continue its vegetative growth under clinostat rotation. These facts suggest that the development of the system of auxin polar transport in Arabidopsis is affected by microgravity, resulting in the inhibition of growth and development, especially during reproductive growth.

  20. Abscisic acid deficiency increases defence responses against Myzus persicae in Arabidopsis.

    PubMed

    Hillwig, Melissa S; Chiozza, Mariana; Casteel, Clare L; Lau, Siau Ting; Hohenstein, Jessica; Hernández, Enrique; Jander, Georg; MacIntosh, Gustavo C

    2016-02-01

    Comparison of Arabidopsis thaliana (Arabidopsis) gene expression induced by Myzus persicae (green peach aphid) feeding, aphid saliva infiltration and abscisic acid (ABA) treatment showed a significant positive correlation. In particular, ABA-regulated genes are over-represented among genes that are induced by M. persicae saliva infiltration into Arabidopsis leaves. This suggests that the induction of ABA-related gene expression could be an important component of the Arabidopsis-aphid interaction. Consistent with this hypothesis, M. persicae populations induced ABA production in wild-type plants. Furthermore, aphid populations were smaller on Arabidopsis aba1-1 mutants, which cannot synthesize ABA, and showed a significant preference for wild-type plants compared with the mutant. Total free amino acids, which play an important role in aphid nutrition, were not altered in the aba1-1 mutant line, but the levels of isoleucine (Ile) and tryptophan (Trp) were differentially affected by aphids in wild-type and mutant plants. Recently, indole glucosinolates have been shown to promote aphid resistance in Arabidopsis. In this study, 4-methoxyindol-3-ylmethylglucosinolate was more abundant in the aba1-1 mutant than in wild-type Arabidopsis, suggesting that the induction of ABA signals that decrease the accumulation of defence compounds may be beneficial for aphids. PMID:25943308

  1. 1,2,4-Tribromobenzene

    Integrated Risk Information System (IRIS)

    1,2,4 - Tribromobenzene ; CASRN 615 - 54 - 3 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcin

  2. 1,2,3-Trichloropropane

    Integrated Risk Information System (IRIS)

    1,2,3 - Trichloropropane ; CASRN 96 - 18 - 4 Human health assessment information on a chemical substance is included in IRIS only after a comprehensive review of toxicity data by U.S . EPA health scientists from several program offices , regional offices , and the Office of Research and Development

  3. trans-1,2-Dichloroethylene

    Integrated Risk Information System (IRIS)

    trans - 1,2 - Dichloroethylene ; CASRN 156 - 60 - 5 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for No

  4. 1,1,2-Trichloropropane

    Integrated Risk Information System (IRIS)

    1,1,2 - Trichloropropane ; CASRN 598 - 77 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarci

  5. 1,1,2-Trichloroethane

    Integrated Risk Information System (IRIS)

    1,1,2 - Trichloroethane ; CASRN 79 - 00 - 5 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcino

  6. 1,2,4-Trichlorobenzene

    Integrated Risk Information System (IRIS)

    1,2,4 - Trichlorobenzene ; CASRN 120 - 82 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarci

  7. cis-1,2-Dichloroethylene

    Integrated Risk Information System (IRIS)

    cis - 1,2 - Dichloroethylene ; CASRN 156 - 59 - 2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Nonc

  8. 1,2-Epoxybutane (EBU)

    Integrated Risk Information System (IRIS)

    1,2 - Epoxybutane ( EBU ) ; CASRN 106 - 88 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarc

  9. A Homolog of Blade-On-Petiole 1 and 2 (BOP1/2) Controls Internode Length and Homeotic Changes of the Barley Inflorescence.

    PubMed

    Jost, Matthias; Taketa, Shin; Mascher, Martin; Himmelbach, Axel; Yuo, Takahisa; Shahinnia, Fahimeh; Rutten, Twan; Druka, Arnis; Schmutzer, Thomas; Steuernagel, Burkhard; Beier, Sebastian; Taudien, Stefan; Scholz, Uwe; Morgante, Michele; Waugh, Robbie; Stein, Nils

    2016-06-01

    Inflorescence architecture in small-grain cereals has a direct effect on yield and is an important selection target in breeding for yield improvement. We analyzed the recessive mutation laxatum-a (lax-a) in barley (Hordeum vulgare), which causes pleiotropic changes in spike development, resulting in (1) extended rachis internodes conferring a more relaxed inflorescence, (2) broadened base of the lemma awns, (3) thinner grains that are largely exposed due to reduced marginal growth of the palea and lemma, and (4) and homeotic conversion of lodicules into two stamenoid structures. Map-based cloning enforced by mapping-by-sequencing of the mutant lax-a locus enabled the identification of a homolog of BLADE-ON-PETIOLE1 (BOP1) and BOP2 as the causal gene. Interestingly, the recently identified barley uniculme4 gene also is a BOP1/2 homolog and has been shown to regulate tillering and leaf sheath development. While the Arabidopsis (Arabidopsis thaliana) BOP1 and BOP2 genes act redundantly, the barley genes contribute independent effects in specifying the developmental growth of vegetative and reproductive organs, respectively. Analysis of natural genetic diversity revealed strikingly different haplotype diversity for the two paralogous barley genes, likely affected by the respective genomic environments, since no indication for an active selection process was detected. PMID:27208226

  10. A Homolog of Blade-On-Petiole 1 and 2 (BOP1/2) Controls Internode Length and Homeotic Changes of the Barley Inflorescence1[OPEN

    PubMed Central

    Taketa, Shin; Mascher, Martin; Yuo, Takahisa; Beier, Sebastian; Taudien, Stefan; Morgante, Michele

    2016-01-01

    Inflorescence architecture in small-grain cereals has a direct effect on yield and is an important selection target in breeding for yield improvement. We analyzed the recessive mutation laxatum-a (lax-a) in barley (Hordeum vulgare), which causes pleiotropic changes in spike development, resulting in (1) extended rachis internodes conferring a more relaxed inflorescence, (2) broadened base of the lemma awns, (3) thinner grains that are largely exposed due to reduced marginal growth of the palea and lemma, and (4) and homeotic conversion of lodicules into two stamenoid structures. Map-based cloning enforced by mapping-by-sequencing of the mutant lax-a locus enabled the identification of a homolog of BLADE-ON-PETIOLE1 (BOP1) and BOP2 as the causal gene. Interestingly, the recently identified barley uniculme4 gene also is a BOP1/2 homolog and has been shown to regulate tillering and leaf sheath development. While the Arabidopsis (Arabidopsis thaliana) BOP1 and BOP2 genes act redundantly, the barley genes contribute independent effects in specifying the developmental growth of vegetative and reproductive organs, respectively. Analysis of natural genetic diversity revealed strikingly different haplotype diversity for the two paralogous barley genes, likely affected by the respective genomic environments, since no indication for an active selection process was detected. PMID:27208226

  11. Photoperiodic flowering regulation in Arabidopsis thaliana

    PubMed Central

    Golembeski, Greg S.; Kinmonth-Schultz, Hannah A.; Song, Young Hun; Imaizumi, Takato

    2015-01-01

    Photoperiod, or the duration of light in a given day, is a critical cue that flowering plants utilize to effectively assess seasonal information and coordinate their reproductive development in synchrony with the external environment. The use of the model plant, Arabidopsis thaliana, has greatly improved our understanding of the molecular mechanisms that determine how plants process and utilize photoperiodic information to coordinate a flowering response. This mechanism is typified by the transcriptional activation of FLOWERING LOCUS T (FT) gene by the transcription factor CONSTANS (CO) under inductive long-day conditions in Arabidopsis. FT protein then moves from the leaves to the shoot apex, where floral meristem development can be initiated. As a point of integration from a variety of environmental factors in the context of a larger system of regulatory pathways that affect flowering, the importance of photoreceptors and the circadian clock in CO regulation throughout the day has been a key feature of the photoperiodic flowering pathway. In addition to these established mechanisms, the recent discovery of a photosynthate derivative trehalose-6-phosphate as an activator of FT in leaves has interesting implications for the involvement of photosynthesis in the photoperiodic flowering response that were suggested from previous physiological experiments in flowering induction. PMID:25684830

  12. A Molecular Portrait of Arabidopsis Meiosis

    PubMed Central

    Ma, Hong

    2006-01-01

    Meiosis is essential for eukaryotic sexual reproduction and important for genetic diversity among individuals. Efforts during the last decade in Arabidopsis have greatly expanded our understanding of the molecular basis of plant meiosis, which has traditionally provided much information about the cytological description of meiosis. Through both forward genetic analysis of mutants with reduced fertility and reverse genetic studies of homologs of known meiotic genes, we now have a basic knowledge about genes important for meiotic recombination and its relationship to pairing and synapsis, critical processes that ensure proper homolog segregation. In addition, several genes affecting meiotic progression, spindle assembly, chromosome separation, and meiotic cytokinesis have also been uncovered and characterized. It is worth noting that Arabidopsis molecular genetic studies are also revealing secrets of meiosis that have not yet been recognized elsewhere among eukaryotes, including gene functions that might be unique to plants and those that are potentially shared with animals and fungi. As we enter the post-genomics era of plant biology, there is no doubt that the next ten years will see an even greater number of discoveries in this important area of plant development and cell biology. Abbreviations: DAPI, 4′,6-diamidino-2-phenylindole; DSB, double strand break; DSBR, double strand break repair; SC, synaptonemal complex; TEM, transmission electron microscopy PMID:22303228

  13. Epigenetic Natural Variation in Arabidopsis thaliana

    PubMed Central

    Jiang, Hongmei; Carrasquillo, Robert; Rabinowicz, Pablo D; Dedhia, Neilay; McCombie, W. Richard; Agier, Nicolas; Bulski, Agnès; Colot, Vincent; Doerge, R.W; Martienssen, Robert A

    2007-01-01

    Cytosine methylation of repetitive sequences is widespread in plant genomes, occurring in both symmetric (CpG and CpNpG) as well as asymmetric sequence contexts. We used the methylation-dependent restriction enzyme McrBC to profile methylated DNA using tiling microarrays of Arabidopsis Chromosome 4 in two distinct ecotypes, Columbia and Landsberg erecta. We also used comparative genome hybridization to profile copy number polymorphisms. Repeated sequences and transposable elements (TEs), especially long terminal repeat retrotransposons, are densely methylated, but one third of genes also have low but detectable methylation in their transcribed regions. While TEs are almost always methylated, genic methylation is highly polymorphic, with half of all methylated genes being methylated in only one of the two ecotypes. A survey of loci in 96 Arabidopsis accessions revealed a similar degree of methylation polymorphism. Within-gene methylation is heritable, but is lost at a high frequency in segregating F2 families. Promoter methylation is rare, and gene expression is not generally affected by differences in DNA methylation. Small interfering RNA are preferentially associated with methylated TEs, but not with methylated genes, indicating that most genic methylation is not guided by small interfering RNA. This may account for the instability of gene methylation, if occasional failure of maintenance methylation cannot be restored by other means. PMID:17579518

  14. MTHFD1 controls DNA methylation in Arabidopsis

    PubMed Central

    Groth, Martin; Moissiard, Guillaume; Wirtz, Markus; Wang, Haifeng; Garcia-Salinas, Carolina; Ramos-Parra, Perla A.; Bischof, Sylvain; Feng, Suhua; Cokus, Shawn J.; John, Amala; Smith, Danielle C.; Zhai, Jixian; Hale, Christopher J.; Long, Jeff A.; Hell, Ruediger; Díaz de la Garza, Rocío I.; Jacobsen, Steven E.

    2016-01-01

    DNA methylation is an epigenetic mechanism that has important functions in transcriptional silencing and is associated with repressive histone methylation (H3K9me). To further investigate silencing mechanisms, we screened a mutagenized Arabidopsis thaliana population for expression of SDCpro-GFP, redundantly controlled by DNA methyltransferases DRM2 and CMT3. Here, we identify the hypomorphic mutant mthfd1-1, carrying a mutation (R175Q) in the cytoplasmic bifunctional methylenetetrahydrofolate dehydrogenase/methenyltetrahydrofolate cyclohydrolase (MTHFD1). Decreased levels of oxidized tetrahydrofolates in mthfd1-1 and lethality of loss-of-function demonstrate the essential enzymatic role of MTHFD1 in Arabidopsis. Accumulation of homocysteine and S-adenosylhomocysteine, genome-wide DNA hypomethylation, loss of H3K9me and transposon derepression indicate that S-adenosylmethionine-dependent transmethylation is inhibited in mthfd1-1. Comparative analysis of DNA methylation revealed that the CMT3 and CMT2 pathways involving positive feedback with H3K9me are mostly affected. Our work highlights the sensitivity of epigenetic networks to one-carbon metabolism due to their common S-adenosylmethionine-dependent transmethylation and has implications for human MTHFD1-associated diseases. PMID:27291711

  15. MTHFD1 controls DNA methylation in Arabidopsis.

    PubMed

    Groth, Martin; Moissiard, Guillaume; Wirtz, Markus; Wang, Haifeng; Garcia-Salinas, Carolina; Ramos-Parra, Perla A; Bischof, Sylvain; Feng, Suhua; Cokus, Shawn J; John, Amala; Smith, Danielle C; Zhai, Jixian; Hale, Christopher J; Long, Jeff A; Hell, Ruediger; Díaz de la Garza, Rocío I; Jacobsen, Steven E

    2016-01-01

    DNA methylation is an epigenetic mechanism that has important functions in transcriptional silencing and is associated with repressive histone methylation (H3K9me). To further investigate silencing mechanisms, we screened a mutagenized Arabidopsis thaliana population for expression of SDCpro-GFP, redundantly controlled by DNA methyltransferases DRM2 and CMT3. Here, we identify the hypomorphic mutant mthfd1-1, carrying a mutation (R175Q) in the cytoplasmic bifunctional methylenetetrahydrofolate dehydrogenase/methenyltetrahydrofolate cyclohydrolase (MTHFD1). Decreased levels of oxidized tetrahydrofolates in mthfd1-1 and lethality of loss-of-function demonstrate the essential enzymatic role of MTHFD1 in Arabidopsis. Accumulation of homocysteine and S-adenosylhomocysteine, genome-wide DNA hypomethylation, loss of H3K9me and transposon derepression indicate that S-adenosylmethionine-dependent transmethylation is inhibited in mthfd1-1. Comparative analysis of DNA methylation revealed that the CMT3 and CMT2 pathways involving positive feedback with H3K9me are mostly affected. Our work highlights the sensitivity of epigenetic networks to one-carbon metabolism due to their common S-adenosylmethionine-dependent transmethylation and has implications for human MTHFD1-associated diseases. PMID:27291711

  16. Local Evolution of Seed Flotation in Arabidopsis

    PubMed Central

    Saez-Aguayo, Susana; Rondeau-Mouro, Corinne; Macquet, Audrey; Kronholm, Ilkka; Ralet, Marie-Christine; Berger, Adeline; Sallé, Christine; Poulain, Damien; Granier, Fabienne; Botran, Lucy; Loudet, Olivier; de Meaux, Juliette; Marion-Poll, Annie; North, Helen M.

    2014-01-01

    Arabidopsis seeds rapidly release hydrophilic polysaccharides from the seed coat on imbibition. These form a heavy mucilage layer around the seed that makes it sink in water. Fourteen natural Arabidopsis variants from central Asia and Scandinavia were identified with seeds that have modified mucilage release and float. Four of these have a novel mucilage phenotype with almost none of the released mucilage adhering to the seed and the absence of cellulose microfibrils. Mucilage release was modified in the variants by ten independent causal mutations in four different loci. Seven distinct mutations affected one locus, coding the MUM2 β-D-galactosidase, and represent a striking example of allelic heterogeneity. The modification of mucilage release has thus evolved a number of times independently in two restricted geographical zones. All the natural mutants identified still accumulated mucilage polysaccharides in seed coat epidermal cells. Using nuclear magnetic resonance (NMR) relaxometry their production and retention was shown to reduce water mobility into internal seed tissues during imbibition, which would help to maintain seed buoyancy. Surprisingly, despite released mucilage being an excellent hydrogel it did not increase the rate of water uptake by internal seed tissues and is more likely to play a role in retaining water around the seed. PMID:24625826

  17. Stomatal Development in Arabidopsis

    PubMed Central

    Pillitteri, Lynn Jo; Dong, Juan

    2013-01-01

    Stomata consist of two guard cells that function as turgor-operated valves that regulate gas exchange in plants. In Arabidopsis, a dedicated cell lineage is initiated and undergoes a series of cell divisions and cell-state transitions to produce a stoma. A set of basic helix-loop-helix (bHLH) transcription factors regulates the transition and differentiation events through the lineage, while the placement of stomata relative to each other is controlled by intercellular signaling via peptide ligands, transmembrane receptors, and mitogen-activated protein kinase (MAPK) modules. Some genes involved in regulating stomatal differentiation or density are also involved in hormonal and environmental stress responses, which may provide a link between modulation of stomatal development or function in response to changes in the environment. Premitotic polarlylocalized proteins provide an added layer of regulation, which can be addressed more thoroughly with the identification of additional proteins in this pathway. Linking the networks that control stomatal development promises to bring advances to our understanding of signal transduction, cell polarity, and cell-fate specification in plants. PMID:23864836

  18. Arabidopsis thaliana—Aphid Interaction

    PubMed Central

    Louis, Joe; Singh, Vijay; Shah, Jyoti

    2012-01-01

    Aphids are important pests of plants that use their stylets to tap into the sieve elements to consume phloem sap. Besides the removal of photosynthates, aphid infestation also alters source-sink patterns. Most aphids also vector viral diseases. In this chapter, we will summarize on recent significant findings in plant-aphid interaction, and how studies involving Arabidopsis thaliana and Myzus persicae (Sülzer), more commonly known as the green peach aphid (GPA), are beginning to provide important insights into the molecular basis of plant defense and susceptibility to aphids. The recent demonstration that expression of dsRNA in Arabidopsis can be used to silence expression of genes in GPA has further expanded the utility of Arabidopsis for evaluating the contribution of the aphid genome-encoded proteins to this interaction. PMID:22666177

  19. GOLDEN 2-LIKE transcription factors for chloroplast development affect ozone tolerance through the regulation of stomatal movement.

    PubMed

    Nagatoshi, Yukari; Mitsuda, Nobutaka; Hayashi, Maki; Inoue, Shin-Ichiro; Okuma, Eiji; Kubo, Akihiro; Murata, Yoshiyuki; Seo, Mitsunori; Saji, Hikaru; Kinoshita, Toshinori; Ohme-Takagi, Masaru

    2016-04-12

    Stomatal movements regulate gas exchange, thus directly affecting the efficiency of photosynthesis and the sensitivity of plants to air pollutants such as ozone. The GARP family transcription factors GOLDEN 2-LIKE1 (GLK1) and GLK2 have known functions in chloroplast development. Here, we show that Arabidopsis thaliana (A. thaliana) plants expressing the chimeric repressors for GLK1 and -2 (GLK1/2-SRDX) exhibited a closed-stomata phenotype and strong tolerance to ozone. By contrast, plants that overexpress GLK1/2 exhibited an open-stomata phenotype and higher sensitivity to ozone. The plants expressing GLK1-SRDX had reduced expression of the genes for inwardly rectifying K(+) (K(+) in) channels and reduced K(+) in channel activity. Abscisic acid treatment did not affect the stomatal phenotype of 35S:GLK1/2-SRDX plants or the transcriptional activity for K(+) in channel gene, indicating that GLK1/2 act independently of abscisic acid signaling. Our results indicate that GLK1/2 positively regulate the expression of genes for K(+) in channels and promote stomatal opening. Because the chimeric GLK1-SRDX repressor driven by a guard cell-specific promoter induced a closed-stomata phenotype without affecting chloroplast development in mesophyll cells, modulating GLK1/2 activity may provide an effective tool to control stomatal movements and thus to confer resistance to air pollutants. PMID:27035938

  20. Arabidopsis cpSRP54 regulates carotenoid accumulation in Arabidopsis and Brassica napus

    PubMed Central

    Gruber, Margaret Y.; Hannoufa, Abdelali

    2012-01-01

    An Arabidopsis thaliana mutant, cbd (carotenoid biosynthesis deficient), was recovered from a mutant population based on its yellow cotyledons, yellow-first true leaves, and stunted growth. Seven-day-old seedlings and mature seeds of this mutant had lower chlorophyll and total carotenoids than the wild type (WT). Genetic and molecular characterization revealed that cbd was a recessive mutant caused by a T-DNA insertion in the gene cpSRP54 encoding the 54kDa subunit of the chloroplast signal recognition particle. Transcript levels of most of the main carotenoid biosynthetic genes in cbd were unchanged relative to WT, but expression increased in carotenoid and abscisic acid catabolic genes. The chloroplasts of cbd also had developmental defects that contributed to decreased carotenoid and chlorophyll contents. Transcription of AtGLK1 (Golden 2-like 1), AtGLK2, and GUN4 appeared to be disrupted in the cbd mutant suggesting that the plastid-to-nucleus retrograde signal may be affected, regulating the changes in chloroplast functional and developmental states and carotenoid content flux. Transformation of A. thaliana and Brassica napus with a gDNA encoding the Arabidopsis cpSRP54 showed the utility of this gene in enhancing levels of seed carotenoids without affecting growth or seed yield. PMID:22791829

  1. Lipid transport mediated by Arabidopsis TGD proteins is unidirectional from the endoplasmic reticulum to the plastid

    SciTech Connect

    Xu, C.; Moellering, E. R., Muthan, B.; Fan, J.; Benning, C.

    2010-06-01

    The transfer of lipids between the endoplasmic reticulum (ER) and the plastid in Arabidopsis involves the TRIGALACTOSYLDIACYLGLYCEROL (TGD) proteins. Lipid exchange is thought to be bidirectional based on the presence of specific lipid molecular species in Arabidopsis mutants impaired in the desaturation of fatty acids of membrane lipids in the ER and plastid. However, it was unclear whether TGD proteins were required for lipid trafficking in both directions. This question was addressed through the analysis of double mutants of tgd1-1 or tgd4-3 in genetic mutant backgrounds leading to a defect in lipid fatty acid desaturation either in the ER (fad2) or the plastid (fad6). The fad6 tgd1-1 and fad6 tgd4-3 double mutants showed drastic reductions in the relative levels of polyunsaturated fatty acids and of galactolipids. The growth of these plants and the development of photosynthetic membrane systems were severely compromised, suggesting a disruption in the import of polyunsaturated fatty acid-containing lipid species from the ER. Furthermore, a forward-genetic screen in the tgd1-2 dgd1 mutant background led to the isolation of a new fad6-2 allele with a marked reduction in the amount of digalactosyldiacylglycerol. In contrast, the introduction of fad2, affecting fatty acid desaturation of lipids in the ER, into the two tgd mutant backgrounds did not further decrease the level of fatty acid desaturation in lipids of extraplastidic membranes. These results suggest that the role of TGD proteins is limited to plastid lipid import, but does not extend to lipid export from the plastid to extraplastidic membranes.

  2. Defects in Peroxisomal 6-Phosphogluconate Dehydrogenase Isoform PGD2 Prevent Gametophytic Interaction in Arabidopsis thaliana.

    PubMed

    Hölscher, Christian; Lutterbey, Marie-Christin; Lansing, Hannes; Meyer, Tanja; Fischer, Kerstin; von Schaewen, Antje

    2016-05-01

    We studied the localization of 6-phosphogluconate dehydrogenase (PGD) isoforms of Arabidopsis (Arabidopsis thaliana). Similar polypeptide lengths of PGD1, PGD2, and PGD3 obscured which isoform may represent the cytosolic and/or plastidic enzyme plus whether PGD2 with a peroxisomal targeting motif also might target plastids. Reporter-fusion analyses in protoplasts revealed that, with a free N terminus, PGD1 and PGD3 accumulate in the cytosol and chloroplasts, whereas PGD2 remains in the cytosol. Mutagenesis of a conserved second ATG enhanced the plastidic localization of PGD1 and PGD3 but not PGD2. Amino-terminal deletions of PGD2 fusions with a free C terminus resulted in peroxisomal import after dimerization, and PGD2 could be immunodetected in purified peroxisomes. Repeated selfing of pgd2 transfer (T-)DNA alleles yielded no homozygous mutants, although siliques and seeds of heterozygous plants developed normally. Detailed analyses of the C-terminally truncated PGD2-1 protein showed that peroxisomal import and catalytic activity are abolished. Reciprocal backcrosses of pgd2-1 suggested that missing PGD activity in peroxisomes primarily affects the male gametophyte. Tetrad analyses in the quartet1-2 background revealed that pgd2-1 pollen is vital and in vitro germination normal, but pollen tube growth inside stylar tissues appeared less directed. Mutual gametophytic sterility was overcome by complementation with a genomic construct but not with a version lacking the first ATG. These analyses showed that peroxisomal PGD2 activity is required for guided growth of the male gametophytes and pollen tube-ovule interaction. Our report finally demonstrates an essential role of oxidative pentose-phosphate pathway reactions in peroxisomes, likely needed to sustain critical levels of nitric oxide and/or jasmonic acid, whose biosynthesis both depend on NADPH provision. PMID:26941195

  3. The Arabidopsis Transcription Factor NAC016 Promotes Drought Stress Responses by Repressing AREB1 Transcription through a Trifurcate Feed-Forward Regulatory Loop Involving NAP[OPEN

    PubMed Central

    Sakuraba, Yasuhito; Kim, Ye-Sol; Han, Su-Hyun; Lee, Byoung-Doo; Paek, Nam-Chon

    2015-01-01

    Drought and other abiotic stresses negatively affect plant growth and development and thus reduce productivity. The plant-specific NAM/ATAF1/2/CUC2 (NAC) transcription factors have important roles in abiotic stress-responsive signaling. Here, we show that Arabidopsis thaliana NAC016 is involved in drought stress responses; nac016 mutants have high drought tolerance, and NAC016-overexpressing (NAC016-OX) plants have low drought tolerance. Using genome-wide gene expression microarray analysis and MEME motif searches, we identified the NAC016-specific binding motif (NAC16BM), GATTGGAT[AT]CA, in the promoters of genes downregulated in nac016-1 mutants. The NAC16BM sequence does not contain the core NAC binding motif CACG (or its reverse complement CGTG). NAC016 directly binds to the NAC16BM in the promoter of ABSCISIC ACID-RESPONSIVE ELEMENT BINDING PROTEIN1 (AREB1), which encodes a central transcription factor in the stress-responsive abscisic acid signaling pathway and represses AREB1 transcription. We found that knockout mutants of the NAC016 target gene NAC-LIKE, ACTIVATED BY AP3/PI (NAP) also exhibited strong drought tolerance; moreover, NAP binds to the AREB1 promoter and suppresses AREB1 transcription. Taking these results together, we propose that a trifurcate feed-forward pathway involving NAC016, NAP, and AREB1 functions in the drought stress response, in addition to affecting leaf senescence in Arabidopsis. PMID:26059204

  4. Unidirectional Movement of Cellulose Synthase Complexes in Arabidopsis Seed Coat Epidermal Cells Deposit Cellulose Involved in Mucilage Extrusion, Adherence, and Ray Formation1[OPEN

    PubMed Central

    Lam, Patricia; Young, Robin; DeBolt, Seth

    2015-01-01

    CELLULOSE SYNTHASE5 (CESA5) synthesizes cellulose necessary for seed mucilage adherence to seed coat epidermal cells of Arabidopsis (Arabidopsis thaliana). The involvement of additional CESA proteins in this process and details concerning the manner in which cellulose is deposited in the mucilage pocket are unknown. Here, we show that both CESA3 and CESA10 are highly expressed in this cell type at the time of mucilage synthesis and localize to the plasma membrane adjacent to the mucilage pocket. The isoxaben resistant1-1 and isoxaben resistant1-2 mutants affecting CESA3 show defects consistent with altered mucilage cellulose biosynthesis. CESA3 can interact with CESA5 in vitro, and green fluorescent protein-tagged CESA5, CESA3, and CESA10 proteins move in a linear, unidirectional fashion around the cytoplasmic column of the cell, parallel with the surface of the seed, in a pattern similar to that of cortical microtubules. Consistent with this movement, cytological evidence suggests that the mucilage is coiled around the columella and unwinds during mucilage extrusion to form a linear ray. Mutations in CESA5 and CESA3 affect the speed of mucilage extrusion and mucilage adherence. These findings imply that cellulose fibrils are synthesized in an ordered helical array around the columella, providing a distinct structure to the mucilage that is important for both mucilage extrusion and adherence. PMID:25926481

  5. 14 CFR 1.2 - Abbreviations and symbols.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Federal Register citations affecting § 1.2, see the List of CFR Sections Affected, which appears in the... flight training device. GS means glide slope. HIRL means high-intensity runway light system. IAS means... FCmeans maximum speed for stability characteristics. V FEmeans maximum flap extended speed. V...

  6. 14 CFR 1.2 - Abbreviations and symbols.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Federal Register citations affecting § 1.2, see the List of CFR Sections Affected, which appears in the...) means nondirectional beacon (automatic direction finder). NM means nautical mile. NOPAC means North... Tracking and Reporting System. RAIL means runway alignment indicator light system. RBN means radio...

  7. 14 CFR 1.2 - Abbreviations and symbols.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Federal Register citations affecting § 1.2, see the List of CFR Sections Affected, which appears in the...) means nondirectional beacon (automatic direction finder). NM means nautical mile. NOPAC means North... Tracking and Reporting System. RAIL means runway alignment indicator light system. RBN means radio...

  8. 14 CFR 1.2 - Abbreviations and symbols.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Federal Register citations affecting § 1.2, see the List of CFR Sections Affected, which appears in the...) means nondirectional beacon (automatic direction finder). NM means nautical mile. NOPAC means North... Tracking and Reporting System. RAIL means runway alignment indicator light system. RBN means radio...

  9. Araport: the Arabidopsis information portal.

    PubMed

    Krishnakumar, Vivek; Hanlon, Matthew R; Contrino, Sergio; Ferlanti, Erik S; Karamycheva, Svetlana; Kim, Maria; Rosen, Benjamin D; Cheng, Chia-Yi; Moreira, Walter; Mock, Stephen A; Stubbs, Joseph; Sullivan, Julie M; Krampis, Konstantinos; Miller, Jason R; Micklem, Gos; Vaughn, Matthew; Town, Christopher D

    2015-01-01

    The Arabidopsis Information Portal (https://www.araport.org) is a new online resource for plant biology research. It houses the Arabidopsis thaliana genome sequence and associated annotation. It was conceived as a framework that allows the research community to develop and release 'modules' that integrate, analyze and visualize Arabidopsis data that may reside at remote sites. The current implementation provides an indexed database of core genomic information. These data are made available through feature-rich web applications that provide search, data mining, and genome browser functionality, and also by bulk download and web services. Araport uses software from the InterMine and JBrowse projects to expose curated data from TAIR, GO, BAR, EBI, UniProt, PubMed and EPIC CoGe. The site also hosts 'science apps,' developed as prototypes for community modules that use dynamic web pages to present data obtained on-demand from third-party servers via RESTful web services. Designed for sustainability, the Arabidopsis Information Portal strategy exploits existing scientific computing infrastructure, adopts a practical mixture of data integration technologies and encourages collaborative enhancement of the resource by its user community. PMID:25414324

  10. The Phenylpropanoid Pathway in Arabidopsis

    PubMed Central

    Fraser, Christopher M.; Chapple, Clint

    2011-01-01

    The phenylpropanoid pathway serves as a rich source of metabolites in plants, being required for the biosynthesis of lignin, and serving as a starting point for the production of many other important compounds, such as the flavonoids, coumarins, and lignans. In spite of the fact that the phenylpropanoids and their derivatives are sometimes classified as secondary metabolites, their relevance to plant survival has been made clear via the study of Arabidopsis and other plant species. As a model system, Arabidopsis has helped to elucidate many details of the phenylpropanoid pathway, its enzymes and intermediates, and the interconnectedness of the pathway with plant metabolism as a whole. These advances in our understanding have been made possible in large part by the relative ease with which mutations can be generated, identified, and studied in Arabidopsis. Herein, we provide an overview of the research progress that has been made in recent years, emphasizing both the genes (and gene families) associated with the phenylpropanoid pathway in Arabidopsis, and the end products that have contributed to the identification of many mutants deficient in the phenylpropanoid metabolism: the sinapate esters. PMID:22303276

  11. Araport: the Arabidopsis Information Portal

    PubMed Central

    Krishnakumar, Vivek; Hanlon, Matthew R.; Contrino, Sergio; Ferlanti, Erik S.; Karamycheva, Svetlana; Kim, Maria; Rosen, Benjamin D.; Cheng, Chia-Yi; Moreira, Walter; Mock, Stephen A.; Stubbs, Joseph; Sullivan, Julie M.; Krampis, Konstantinos; Miller, Jason R.; Micklem, Gos; Vaughn, Matthew; Town, Christopher D.

    2015-01-01

    The Arabidopsis Information Portal (https://www.araport.org) is a new online resource for plant biology research. It houses the Arabidopsis thaliana genome sequence and associated annotation. It was conceived as a framework that allows the research community to develop and release ‘modules’ that integrate, analyze and visualize Arabidopsis data that may reside at remote sites. The current implementation provides an indexed database of core genomic information. These data are made available through feature-rich web applications that provide search, data mining, and genome browser functionality, and also by bulk download and web services. Araport uses software from the InterMine and JBrowse projects to expose curated data from TAIR, GO, BAR, EBI, UniProt, PubMed and EPIC CoGe. The site also hosts ‘science apps,’ developed as prototypes for community modules that use dynamic web pages to present data obtained on-demand from third-party servers via RESTful web services. Designed for sustainability, the Arabidopsis Information Portal strategy exploits existing scientific computing infrastructure, adopts a practical mixture of data integration technologies and encourages collaborative enhancement of the resource by its user community. PMID:25414324

  12. A hydroxycinnamoyltransferase responsible for synthesizing suberin aromatics in Arabidopsis

    SciTech Connect

    Gou, J.Y.; Liu, C.; Yu, X.-H.

    2009-11-03

    Suberin, a polyester polymer in the cell wall of terrestrial plants, controls the transport of water and nutrients and protects plant from pathogenic infections and environmental stresses. Structurally, suberin consists of aliphatic and aromatic domains; p-hydroxycinnamates, such as ferulate, p-coumarate, and/or sinapate, are the major phenolic constituents of the latter. By analyzing the 'wall-bound' phenolics of mutant lines of Arabidopsis deficient in a family of acyl-CoA dependent acyltransferase (BAHD) genes, we discovered that the formation of aromatic suberin in Arabidopsis, primarily in seed and root tissues, depends on a member of the BAHD superfamily of enzymes encoded by At5g41040. This enzyme exhibits an {omega}-hydroxyacid hydroxycinnamoyltransferase activity with an in vitro kinetic preference for feruloyl-CoA and 16-hydroxypalmitic acid. Knocking down or knocking out the At5g41040 gene in Arabidopsis reduces specifically the quantity of ferulate in suberin, but does not affect the accumulation of p-coumarate or sinapate. The loss of the suberin phenolic differentially affects the aliphatic monomer loads and alters the permeability and sensitivity of seeds and roots to salt stress. This highlights the importance of suberin aromatics in the polymer's function.

  13. Integration of flowering signals in winter-annual Arabidopsis.

    PubMed

    Michaels, Scott D; Himelblau, Edward; Kim, Sang Yeol; Schomburg, Fritz M; Amasino, Richard M

    2005-01-01

    Photoperiod is the primary environmental factor affecting flowering time in rapid-cycling accessions of Arabidopsis (Arabidopsis thaliana). Winter-annual Arabidopsis, in contrast, have both a photoperiod and a vernalization requirement for rapid flowering. In winter annuals, high levels of the floral inhibitor FLC (FLOWERING LOCUS C) suppress flowering prior to vernalization. FLC acts to delay flowering, in part, by suppressing expression of the floral promoter SOC1 (SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1). Vernalization leads to a permanent epigenetic suppression of FLC. To investigate how winter-annual accessions integrate signals from the photoperiod and vernalization pathways, we have examined activation-tagged alleles of FT and the FT homolog, TSF (TWIN SISTER OF FT), in a winter-annual background. Activation of FT or TSF strongly suppresses the FLC-mediated late-flowering phenotype of winter annuals; however, FT and TSF overexpression does not affect FLC mRNA levels. Rather, FT and TSF bypass the block to flowering created by FLC by activating SOC1 expression. We have also found that FLC acts as a dosage-dependent inhibitor of FT expression. Thus, the integration of flowering signals from the photoperiod and vernalization pathways occurs, at least in part, through the regulation of FT, TSF, and SOC1. PMID:15618421

  14. The Arabidopsis transposable element Tag1 is widely distributed among Arabidopsis ecotypes.

    PubMed

    Frank, M J; Preuss, D; Mack, A; Kuhlmann, T C; Crawford, N M

    1998-02-01

    Tag1 is an autonomous transposable element (3.3 kb in length) first identified as an insertion in the CHL1 (NRT1) gene of Arabidopsis thaliana. Tag1 has been found in the Landsberg erecta ecotype of A. thaliana but not in Columbia or WS. In this paper, 41 additional ecotypes were examined for the presence of Tag1. Using an internal Tag1 fragment as probe, we found that DNA form 19 of the 41 ecotypes strongly hybridized to Tag1. Almost all of the Tag1-containing ecotypes had only one or two copies of Tag1 per haploid genome, as determined by Southern blot analysis. The only exception, Bf-1 from Bretagny-sur-Orge, France, had four copies. Two ecotypes, Di-G and S96, gave identical Southern blot patterns to that of Landsberg erecta and were subsequently shown to contain Tag1 at the same two positions found in Landsberg erecta (loci designated as Tag1-2 and Tag1-3). Two other ecotypes, Ag-0 and Lo-1, had a Tag1 element located at Tag1-2 but not at Tag1-3. The distance between these two loci was determined to be 0.37 cM. Analysis of DNA from two related species, A. griffithiana and A. pumila, showed that both species contain sequences that hybridize to Tag1 and that could be amplified with an oligonucleotide specific to the terminal inverted repeats of Tag1. These results show that Tag1 and related elements are present, and may be useful for insertional mutagenesis, in many A. thaliana ecotypes and several Arabidopsis species. PMID:9529529

  15. Bacterial cyclic beta-(1,2)-glucan acts in systemic suppression of plant immune responses.

    PubMed

    Rigano, Luciano Ariel; Payette, Caroline; Brouillard, Geneviève; Marano, Maria Rosa; Abramowicz, Laura; Torres, Pablo Sebastián; Yun, Maximina; Castagnaro, Atilio Pedro; Oirdi, Mohamed El; Dufour, Vanessa; Malamud, Florencia; Dow, John Maxwell; Bouarab, Kamal; Vojnov, Adrian Alberto

    2007-06-01

    Although cyclic glucans have been shown to be important for a number of symbiotic and pathogenic bacterium-plant interactions, their precise roles are unclear. Here, we examined the role of cyclic beta-(1,2)-glucan in the virulence of the black rot pathogen Xanthomonas campestris pv campestris (Xcc). Disruption of the Xcc nodule development B (ndvB) gene, which encodes a glycosyltransferase required for cyclic glucan synthesis, generated a mutant that failed to synthesize extracellular cyclic beta-(1,2)-glucan and was compromised in virulence in the model plants Arabidopsis thaliana and Nicotiana benthamiana. Infection of the mutant bacterium in N. benthamiana was associated with enhanced callose deposition and earlier expression of the PATHOGENESIS-RELATED1 (PR-1) gene. Application of purified cyclic beta-(1,2)-glucan prior to inoculation of the ndvB mutant suppressed the accumulation of callose deposition and the expression of PR-1 in N. benthamiana and restored virulence in both N. benthamiana and Arabidopsis plants. These effects were seen when cyclic glucan and bacteria were applied either to the same or to different leaves. Cyclic beta-(1,2)-glucan-induced systemic suppression was associated with the transport of the molecule throughout the plant. Systemic suppression is a novel counterdefensive strategy that may facilitate pathogen spread in plants and may have important implications for the understanding of plant-pathogen coevolution and for the development of phytoprotection measures. PMID:17601826

  16. Powerful Partners: Arabidopsis and Chemical Genomics

    PubMed Central

    Robert, Stéphanie; Raikhel, Natasha V.; Hicks, Glenn R.

    2009-01-01

    Chemical genomics (i.e. genomics scale chemical genetics) approaches capitalize on the ability of low molecular mass molecules to modify biological processes. Such molecules are used to modify the activity of a protein or a pathway in a manner that it is tunable and reversible. Bioactive chemicals resulting from forward or reverse chemical screens can be useful in understanding and dissecting complex biological processes due to the essentially limitless variation in structure and activities inherent in chemical space. A major advantage of this approach as a powerful addition to conventional plant genetics is the fact that chemical genomics can address loss-of-function lethality and redundancy. Furthermore, the ability of chemicals to be added at will and to act quickly can permit the study of processes that are highly dynamic such as endomembrane trafficking. An important aspect of utilizing small molecules effectively is to characterize bioactive chemicals in detail including an understanding of structure-activity relationships and the identification of active and inactive analogs. Bioactive chemicals can be useful as reagents to probe biological pathways directly. However, the identification of cognate targets and their pathways is also informative and can be achieved by screens for genetic resistance or hypersensitivity in Arabidopsis thaliana or other organisms from which the results can be translated to plants. In addition, there are approaches utilizing “tagged” chemical libraries that possess reactive moieties permitting the immobilization of active compounds. This opens the possibility for biochemical purification of putative cognate targets. We will review approaches to screen for bioactive chemicals that affect biological processes in Arabidopsis and provide several examples of the power and challenges inherent in this new approach in plant biology. PMID:22303245

  17. Dataset of Arabidopsis plants that overexpress FT driven by a meristem-specific KNAT1 promoter.

    PubMed

    Duplat-Bermúdez, L; Ruiz-Medrano, R; Landsman, D; Mariño-Ramírez, L; Xoconostle-Cázares, B

    2016-09-01

    In this dataset we integrated figures comparing leaf number and rosette diameter in three Arabidopsis FT overexpressor lines (AtFTOE) driven by KNAT1 promoter, "A member of the KNOTTED class of homeodomain proteins encoded by the STM gene of Arabidopsis" [5], vs Wild Type (WT) Arabidopsis plats. Also, presented in the tables are some transcriptomic data obtained by RNA-seq Illumina HiSeq from rosette leaves of Arabidopsis plants of AtFTOE 2.1 line vs WT with accession numbers SRR2094583 and SRR2094587 for AtFTOE replicates 1-3 and AtWT for control replicates 1-2 respectively. Raw data of paired-end sequences are located in the public repository of the National Center for Biotechnology Information of the National Library of Medicine, National Institutes of Health, United States of America, Bethesda, MD, USA as Sequence Read Archive (SRA). Performed analyses of differential expression genes are visualized by Mapman and presented in figures. "Transcriptomic analysis of Arabidopsis overexpressing flowering locus T driven by a meristem-specific promoter that induces early flowering" [2], described the interpretation and discussion of the obtained data. PMID:27366785

  18. Asparagine Metabolic Pathways in Arabidopsis.

    PubMed

    Gaufichon, Laure; Rothstein, Steven J; Suzuki, Akira

    2016-04-01

    Inorganic nitrogen in the form of ammonium is assimilated into asparagine via multiple steps involving glutamine synthetase (GS), glutamate synthase (GOGAT), aspartate aminotransferase (AspAT) and asparagine synthetase (AS) in Arabidopsis. The asparagine amide group is liberated by the reaction catalyzed by asparaginase (ASPG) and also the amino group of asparagine is released by asparagine aminotransferase (AsnAT) for use in the biosynthesis of amino acids. Asparagine plays a primary role in nitrogen recycling, storage and transport in developing and germinating seeds, as well as in vegetative and senescence organs. A small multigene family encodes isoenzymes of each step of asparagine metabolism in Arabidopsis, except for asparagine aminotransferase encoded by a single gene. The aim of this study is to highlight the structure of the genes and encoded enzyme proteins involved in asparagine metabolic pathways; the regulation and role of different isogenes; and kinetic and physiological properties of encoded enzymes in different tissues and developmental stages. PMID:26628609

  19. Rubidium (Potassium) Uptake by Arabidopsis

    PubMed Central

    Polley, L. David; Hopkins, Johns W.

    1979-01-01

    Experiments are reported in which the uptake of 86Rb+, used as an analog of K+, into cultured cells of Arabidopsis thaliana is investigated. A single transport system is found with Km = 0.34 millimolar and Vmax = 14 nmoles per milligram of protein per hour. This system is blocked by the metabolic inhibitor carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and by cold. At high concentrations of external K+ (above 1 millimolar), a significant fraction of total uptake is energy-independent. No evidence is found for more than one energy-dependent uptake system or for concentration-dependent modifications of a carrier as postulated in multiphasic transport models. Rb+ uptake was also examined in cultured cells derived from an “osmotic mutant” of Arabidopsis. The system closely resembles that found in wild type cells with the exception that the Michaelis-Menten constants are higher: Km = 1 millimolar and Vmax = 32 nanomoles per milligram of protein per hour. The possibility that these results are artifacts associated with use of cultured cells was checked by examining 86Rb+ uptake by roots of intact seedlings of wild type Arabidopsis. A single energy-dependent transport system is found with Km = 0.42 millimolar which is not significantly different from the Km of cultured cells. There is also energy-independent uptake at high external ion concentration. PMID:16660969

  20. Side Elevation, End Elevation, Cross Section, 1/2 Roof Plan, 1/2 ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Side Elevation, End Elevation, Cross Section, 1/2 Roof Plan, 1/2 Reflected Plan, 1/2 Floor Plan, 1/2 Reflected Plan - Jack's Mill Covered Bridge, Spanning Henderson Creek, Oquawka, Henderson County, IL

  1. Arabidopsis AtERF014 acts as a dual regulator that differentially modulates immunity against Pseudomonas syringae pv. tomato and Botrytis cinerea.

    PubMed

    Zhang, Huijuan; Hong, Yongbo; Huang, Lei; Li, Dayong; Song, Fengming

    2016-01-01

    ERF transcription factors play critical roles in plant immune responses. Here, we report the function of AtERF014, a nucleus-localized transcriptional activator, in Arabidopsis immunity. Expression of AtERF014 was induced by Pseudomonas syringae pv. tomato (Pst) and Botrytis cinerea (Bc). AtERF014-overexpressing (OE) plants displayed increased Pst resistance but decreased Bc resistance, whereas AtERF014-RNAi plants exhibited decreased Pst resistance but increased Bc resistance. After Pst infection, expression of salicylic acid (SA)-responsive genes AtPR1 and AtPR5 in AtERF014-OE plants and of a jasmonic acid/ethylene-responsive gene AtPDF1.2 in AtERF014-RNAi plants was intensified but expression of AtPDF1.2 in AtERF014-OE plants and of AtPR1 and AtPR5 in AtERF014-RNAi plants was weakened. After Bc infection, expression of AtPR1 and AtPR5 in AtERF014-OE plants was attenuated but expression of AtPR1, AtPR5 and AtPDF1.2 in AtERF014-RNAi plants was strengthened. Pathogen- and flg22-induced ROS burst, expression of PTI genes and SA-induced defense were partially suppressed in AtERF014-RNAi plants, whereas pathogen-induced ROS and flg22-induced immune response were strengthened in AtER014-OE plants. Altered expression of AtERR014 affected expression of pectin biosynthetic genes and pectin content in AtERF014-RNAi plants was decreased. These data demonstrate that AtERF014 acts as a dual regulator that differentially modulates immunity against Pst and Bc in Arabidopsis. PMID:27445230

  2. Arabidopsis AtERF014 acts as a dual regulator that differentially modulates immunity against Pseudomonas syringae pv. tomato and Botrytis cinerea

    PubMed Central

    Zhang, Huijuan; Hong, Yongbo; Huang, Lei; Li, Dayong; Song, Fengming

    2016-01-01

    ERF transcription factors play critical roles in plant immune responses. Here, we report the function of AtERF014, a nucleus-localized transcriptional activator, in Arabidopsis immunity. Expression of AtERF014 was induced by Pseudomonas syringae pv. tomato (Pst) and Botrytis cinerea (Bc). AtERF014-overexpressing (OE) plants displayed increased Pst resistance but decreased Bc resistance, whereas AtERF014-RNAi plants exhibited decreased Pst resistance but increased Bc resistance. After Pst infection, expression of salicylic acid (SA)-responsive genes AtPR1 and AtPR5 in AtERF014-OE plants and of a jasmonic acid/ethylene-responsive gene AtPDF1.2 in AtERF014-RNAi plants was intensified but expression of AtPDF1.2 in AtERF014-OE plants and of AtPR1 and AtPR5 in AtERF014-RNAi plants was weakened. After Bc infection, expression of AtPR1 and AtPR5 in AtERF014-OE plants was attenuated but expression of AtPR1, AtPR5 and AtPDF1.2 in AtERF014-RNAi plants was strengthened. Pathogen- and flg22-induced ROS burst, expression of PTI genes and SA-induced defense were partially suppressed in AtERF014-RNAi plants, whereas pathogen-induced ROS and flg22-induced immune response were strengthened in AtER014-OE plants. Altered expression of AtERR014 affected expression of pectin biosynthetic genes and pectin content in AtERF014-RNAi plants was decreased. These data demonstrate that AtERF014 acts as a dual regulator that differentially modulates immunity against Pst and Bc in Arabidopsis. PMID:27445230

  3. Gravity-regulated gene expression in Arabidopsis thaliana

    NASA Astrophysics Data System (ADS)

    Sederoff, Heike; Brown, Christopher S.; Heber, Steffen; Kajla, Jyoti D.; Kumar, Sandeep; Lomax, Terri L.; Wheeler, Benjamin; Yalamanchili, Roopa

    Plant growth and development is regulated by changes in environmental signals. Plants sense environmental changes and respond to them by modifying gene expression programs to ad-just cell growth, differentiation, and metabolism. Functional expression of genes comprises many different processes including transcription, translation, post-transcriptional and post-translational modifications, as well as the degradation of RNA and proteins. Recently, it was discovered that small RNAs (sRNA, 18-24 nucleotides long), which are heritable and systemic, are key elements in regulating gene expression in response to biotic and abiotic changes. Sev-eral different classes of sRNAs have been identified that are part of a non-cell autonomous and phloem-mobile network of regulators affecting transcript stability, translational kinetics, and DNA methylation patterns responsible for heritable transcriptional silencing (epigenetics). Our research has focused on gene expression changes in response to gravistimulation of Arabidopsis roots. Using high-throughput technologies including microarrays and 454 sequencing, we iden-tified rapid changes in transcript abundance of genes as well as differential expression of small RNA in Arabidopsis root apices after minutes of reorientation. Some of the differentially regu-lated transcripts are encoded by genes that are important for the bending response. Functional mutants of those genes respond faster to reorientation than the respective wild type plants, indicating that these proteins are repressors of differential cell elongation. We compared the gravity responsive sRNAs to the changes in transcript abundances of their putative targets and identified several potential miRNA: target pairs. Currently, we are using mutant and transgenic Arabidopsis plants to characterize the function of those miRNAs and their putative targets in gravitropic and phototropic responses in Arabidopsis.

  4. An International Bioinformatics Infrastructure to Underpin the Arabidopsis Community

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The future bioinformatics needs of the Arabidopsis community as well as those of other scientific communities that depend on Arabidopsis resources were discussed at a pair of recent meetings held by the Multinational Arabidopsis Steering Committee (MASC) and the North American Arabidopsis Steering C...

  5. Using "Arabidopsis" Genetic Sequences to Teach Bioinformatics

    ERIC Educational Resources Information Center

    Zhang, Xiaorong

    2009-01-01

    This article describes a new approach to teaching bioinformatics using "Arabidopsis" genetic sequences. Several open-ended and inquiry-based laboratory exercises have been designed to help students grasp key concepts and gain practical skills in bioinformatics, using "Arabidopsis" leucine-rich repeat receptor-like kinase (LRR RLK) genetic…

  6. Arabidopsis mutants with a reduced seed dormancy.

    PubMed Central

    Léon-Kloosterziel, K M; van de Bunt, G A; Zeevaart, J A; Koornneef, M

    1996-01-01

    The development of seed dormancy is an aspect of seed maturation, the last stage of seed development. To isolate mutants of Arabidopsis thaliana that are affected in this process, we selected directly for the absence of dormancy among freshly harvested M2 seeds. The screen yielded two mutants exhibiting a reduced dormancy, rdo1 and rdo2, that are specifically affected in dormancy determined by the embryo. The rdo1 and rdo2 mutants show normal levels of abscisic acid and the same sensitivity to abscisic acid, ethylene, auxin, and cytokinin as the wild type. The rdo2 mutant but not the rdo1 mutant has a reduced sensitivity to the gibberellin biosynthesis inhibitor tetcyclacis. Double-mutant analysis suggested that the RDO1 and RDO2 genes are involved in separate pathways leading to the development of dormancy. We assume that the RDO2 gene controls a step in the induction of dormancy that is most likely induced by abscisic acid and is expressed as an increase of the gibberellin requirement for germination. PMID:8587986

  7. Intragenic recombination in the CSR1 locus of Arabidopsis.

    PubMed

    Mourad, G; Haughn, G; King, J

    1994-04-01

    Four classes of herbicides are known to inhibit plant acetolactate synthase (ALS). In Arabidopsis, ALS is encoded by a single gene, CSR1. The dominant csr1-1 allele encodes an ALS resistant to chlorsulfuron and triazolopyrimidine sulfonamide while the dominant csr1-2 allele encodes an ALS resistant to imazapyr and pyrimidyl-oxy-benzoate. The molecular distance between the point mutations in csr1-1 and csr1-2 is 1369 bp. Here we used multiherbicide resistance as a stringent selection to measure the intragenic recombination frequency between these two point mutations. We found this frequency to be 0.008 +/- 0.0028. The recombinant multiherbicide-resistant allele, csr1-4, provides an ideal marker for plant genetic transformation. PMID:8177214

  8. Architectural phenotypes in the transparent testa mutants of Arabidopsis thaliana

    PubMed Central

    Buer, Charles S.; Djordjevic, Michael A.

    2009-01-01

    Flavonoids are low molecular weight secondary plant metabolites with a myriad of functions. As flavonoids affect auxin transport (an important growth-controlling hormone) and are biologically active in eukaryotes, flavonoid mutants were expected to have undescribed architectural phenotypes. The Arabidopsis thaliana transparent testa (tt) mutants are compromised in the enzymatic steps or transcriptional regulators affecting flavonoid synthesis. tt mutant seedlings were grown on hard-slanted agar (a stress condition), under varying light conditions, and in soil to examine the resulting growth patterns. These tt mutants revealed a wide variety of architectural phenotypes in root and aerial tissues. Mutants with increased inflorescences, siliques, and lateral root density or reduced stature are traits that could affect plant yield or performance under certain environmental conditions. The regulatory genes affected in architectural traits may provide useful molecular targets for examination in other plants. PMID:19129166

  9. An Arabidopsis neutral ceramidase mutant ncer1 accumulates hydroxyceramides and is sensitive to oxidative stress

    PubMed Central

    Li, Jian; Bi, Fang-Cheng; Yin, Jian; Wu, Jian-Xin; Rong, Chan; Wu, Jia-Li; Yao, Nan

    2015-01-01

    Ceramidases hydrolyze ceramide into sphingosine and fatty acids and, although ceramidases function as key regulators of sphingolipid homeostasis in mammals, their roles in plants remain largely unknown. Here, we characterized the Arabidopsis thaliana ceramidase AtNCER1, a homolog of human neutral ceramidase. AtNCER1 localizes predominantly on the endoplasmic reticulum. The ncer1 T-DNA insertion mutants had no visible phenotype, but accumulated hydroxyceramides, and showed increased sensitivity to oxidative stress induced by methyl viologen. Plants over-expressing AtNCER1 showed increased tolerance to oxidative stress. These data indicate that the Arabidopsis neutral ceramidase affects sphingolipid homeostasis and oxidative stress responses. PMID:26150824

  10. The cytokinin response factors modulate root and shoot growth and promote leaf senescence in Arabidopsis.

    PubMed

    Raines, Tracy; Shanks, Carly; Cheng, Chia-Yi; McPherson, Duncan; Argueso, Cristiana T; Kim, Hyo J; Franco-Zorrilla, José M; López-Vidriero, Irene; Solano, Roberto; Vaňková, Radomíra; Schaller, G Eric; Kieber, Joseph J

    2016-01-01

    The cytokinin response factors (CRFs) are a group of related AP2/ERF transcription factors that are transcriptionally induced by cytokinin. Here we explore the role of the CRFs in Arabidopsis thaliana growth and development by analyzing lines with decreased and increased CRF function. While single crf mutations have no appreciable phenotypes, disruption of multiple CRFs results in larger rosettes, delayed leaf senescence, a smaller root apical meristem (RAM), reduced primary and lateral root growth, and, in etiolated seedlings, shorter hypocotyls. In contrast, overexpression of CRFs generally results in the opposite phenotypes. The crf1,2,5,6 quadruple mutant is embryo lethal, indicating that CRF function is essential for embryo development. Disruption of the CRFs results in partially insensitivity to cytokinin in a root elongation assay and affects the basal expression of a significant number of cytokinin-regulated genes, including the type-A ARRs, although it does not impair the cytokinin induction of the type-A ARRs. Genes encoding homeobox transcription factors are mis-expressed in the crf1,3,5,6 mutant, including STIMPY/WOX9 that is required for root and shoot apical meristem maintenance roots and which has previously been linked to cytokinin. These results indicate that the CRF transcription factors play important roles in multiple aspects of plant growth and development, in part through a complex interaction with cytokinin signaling. PMID:26662515

  11. 43 CFR 2812.1-2 - Contents.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Contents. 2812.1-2 Section 2812.1-2 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT... Bay Revested Lands § 2812.1-2 Contents. (a) An individual applicant and each member of...

  12. 43 CFR 2812.1-2 - Contents.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Contents. 2812.1-2 Section 2812.1-2 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT... Bay Revested Lands § 2812.1-2 Contents. (a) An individual applicant and each member of...

  13. 43 CFR 2812.1-2 - Contents.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Contents. 2812.1-2 Section 2812.1-2 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT... Bay Revested Lands § 2812.1-2 Contents. (a) An individual applicant and each member of...

  14. 43 CFR 2812.1-2 - Contents.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Contents. 2812.1-2 Section 2812.1-2 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT... Bay Revested Lands § 2812.1-2 Contents. (a) An individual applicant and each member of...

  15. 16 CFR 1.2 - Procedure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 1 2012-01-01 2012-01-01 false Procedure. 1.2 Section 1.2 Commercial Practices FEDERAL TRADE COMMISSION ORGANIZATION, PROCEDURES AND RULES OF PRACTICE GENERAL PROCEDURES Industry Guidance Advisory Opinions § 1.2 Procedure. (a) Application. The request for advice...

  16. 7 CFR 1.2 - Policy.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 1 2011-01-01 2011-01-01 false Policy. 1.2 Section 1.2 Agriculture Office of the Secretary of Agriculture ADMINISTRATIVE REGULATIONS Official Records § 1.2 Policy. (a) Agencies of USDA shall comply with the time limits set forth in the FOIA and in this subpart for responding to...

  17. 7 CFR 1.2 - Policy.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 1 2014-01-01 2014-01-01 false Policy. 1.2 Section 1.2 Agriculture Office of the Secretary of Agriculture ADMINISTRATIVE REGULATIONS Official Records § 1.2 Policy. (a) Agencies of USDA shall comply with the time limits set forth in the FOIA and in this subpart for responding to...

  18. 7 CFR 1.2 - Policy.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 1 2012-01-01 2012-01-01 false Policy. 1.2 Section 1.2 Agriculture Office of the Secretary of Agriculture ADMINISTRATIVE REGULATIONS Official Records § 1.2 Policy. (a) Agencies of USDA shall comply with the time limits set forth in the FOIA and in this subpart for responding to...

  19. 11 CFR 1.2 - Definitions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 11 Federal Elections 1 2010-01-01 2010-01-01 false Definitions. 1.2 Section 1.2 Federal Elections FEDERAL ELECTION COMMISSION PRIVACY ACT § 1.2 Definitions. As defined in the Privacy Act of 1974 and for the purposes of this part, unless otherwise required by the context, the following terms shall have these meanings: Act means the...

  20. 43 CFR 2812.1-2 - Contents.

    Code of Federal Regulations, 2011 CFR

    2008-10-01

    ... 43 Public Lands: Interior 2 2008-10-01 2008-10-01 false Contents. 2812.1-2 Section 2812.1-2 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT.... and Coos Bay Revested Lands § 2812.1-2 Contents. (a) An individual applicant and each member of...

  1. 43 CFR 2812.1-2 - Contents.

    Code of Federal Regulations, 2011 CFR

    1996-10-01

    ... 43 Public Lands: Interior 2 1996-10-01 1996-10-01 false Contents. 2812.1-2 Section 2812.1-2 LAND RESOURCE MANAGEMENT (2000) TRAMROADS AND LOGGING ROADS Over O. and C. and Coos Bay Revested Lands § 2812.1-2 Contents. (a) An individual applicant and each member of any unincorporated association which...

  2. 43 CFR 2812.1-2 - Contents.

    Code of Federal Regulations, 2010 CFR

    2000-10-01

    ... 43 Public Lands: Interior 2 2000-10-01 2000-10-01 false Contents. 2812.1-2 Section 2812.1-2 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT,DEPARTMENT OF... Revested Lands § 2812.1-2 Contents. (a) An individual applicant and each member of any...

  3. 43 CFR 2812.1-2 - Contents.

    Code of Federal Regulations, 2011 CFR

    2002-10-01

    ... 43 Public Lands: Interior 2 2002-10-01 2002-10-01 false Contents. 2812.1-2 Section 2812.1-2 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT... Bay Revested Lands § 2812.1-2 Contents. (a) An individual applicant and each member of...

  4. 43 CFR 2812.1-2 - Contents.

    Code of Federal Regulations, 2013 CFR

    2006-10-01

    ... 43 Public Lands: Interior 2 2006-10-01 2006-10-01 false Contents. 2812.1-2 Section 2812.1-2 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT... Bay Revested Lands § 2812.1-2 Contents. (a) An individual applicant and each member of...

  5. 43 CFR 2812.1-2 - Contents.

    Code of Federal Regulations, 2012 CFR

    1997-10-01

    ... 43 Public Lands: Interior 2 1997-10-01 1997-10-01 false Contents. 2812.1-2 Section 2812.1-2 LAND RESOURCE MANAGEMENT (2000) TRAMROADS AND LOGGING ROADS Over O. and C. and Coos Bay Revested Lands § 2812.1-2 Contents. (a) An individual applicant and each member of any unincorporated association which...

  6. 7 CFR 1.2 - Policy.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 1 2010-01-01 2010-01-01 false Policy. 1.2 Section 1.2 Agriculture Office of the Secretary of Agriculture ADMINISTRATIVE REGULATIONS Official Records § 1.2 Policy. (a) Agencies of USDA shall comply with the time limits set forth in the FOIA and in this subpart for responding to...

  7. 7 CFR 1.2 - Policy.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 1 2013-01-01 2013-01-01 false Policy. 1.2 Section 1.2 Agriculture Office of the Secretary of Agriculture ADMINISTRATIVE REGULATIONS Official Records § 1.2 Policy. (a) Agencies of USDA shall comply with the time limits set forth in the FOIA and in this subpart for responding to...

  8. 16 CFR 1.2 - Procedure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 1 2013-01-01 2013-01-01 false Procedure. 1.2 Section 1.2 Commercial Practices FEDERAL TRADE COMMISSION ORGANIZATION, PROCEDURES AND RULES OF PRACTICE GENERAL PROCEDURES Industry Guidance Advisory Opinions § 1.2 Procedure. (a) Application. The request for advice...

  9. 45 CFR 1210.1-2 - Scope.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 45 Public Welfare 4 2013-10-01 2013-10-01 false Scope. 1210.1-2 Section 1210.1-2 Public Welfare Regulations Relating to Public Welfare (Continued) CORPORATION FOR NATIONAL AND COMMUNITY SERVICE VISTA TRAINEE DESELECTION AND VOLUNTEER EARLY TERMINATION PROCEDURES General § 1210.1-2 Scope. (a) This part applies to all Trainees and...

  10. 45 CFR 1211.1-2 - Applicability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 45 Public Welfare 4 2013-10-01 2013-10-01 false Applicability. 1211.1-2 Section 1211.1-2 Public Welfare Regulations Relating to Public Welfare (Continued) CORPORATION FOR NATIONAL AND COMMUNITY SERVICE VOLUNTEER GRIEVANCE PROCEDURES § 1211.1-2 Applicability. This part applies to all volunteers enrolled under part A of title I of the...

  11. 16 CFR 1.2 - Procedure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 1 2011-01-01 2011-01-01 false Procedure. 1.2 Section 1.2 Commercial Practices FEDERAL TRADE COMMISSION ORGANIZATION, PROCEDURES AND RULES OF PRACTICE GENERAL PROCEDURES Industry Guidance Advisory Opinions § 1.2 Procedure. (a) Application. The request for advice...

  12. 16 CFR 1.2 - Procedure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Procedure. 1.2 Section 1.2 Commercial Practices FEDERAL TRADE COMMISSION ORGANIZATION, PROCEDURES AND RULES OF PRACTICE GENERAL PROCEDURES Industry Guidance Advisory Opinions § 1.2 Procedure. (a) Application. The request for advice...

  13. 16 CFR 1.2 - Procedure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 1 2014-01-01 2014-01-01 false Procedure. 1.2 Section 1.2 Commercial Practices FEDERAL TRADE COMMISSION ORGANIZATION, PROCEDURES AND RULES OF PRACTICE GENERAL PROCEDURES Industry Guidance Advisory Opinions § 1.2 Procedure. (a) Application. The request for advice...

  14. Molecular genetics of root gravitropism and waving in Arabidopsis thaliana

    NASA Technical Reports Server (NTRS)

    Sedbrook, J.; Boonsirichai, K.; Chen, R.; Hilson, P.; Pearlman, R.; Rosen, E.; Rutherford, R.; Batiza, A.; Carroll, K.; Schulz, T.; Masson, P. H.

    1998-01-01

    When Arabidopsis thaliana seedlings grow embedded in an agar-based medium, their roots grow vertically downward. This reflects their ability to sense the gravity vector and to position their tip parallel to it (gravitropism). We have isolated a number of mutations affecting root gravitropism in Arabidopsis thaliana. One of these mutations, named arg1, affects root and hypocotyl gravitropism without promoting defects in starch content or in the ability of seedlings' organs to respond to plant hormones. The ARG1 gene was cloned and shown to code for a protein with a J domain at its amino terminus and a second sequence motif found in several cytoskeleton binding proteins. Mutations in the AGR1 locus promote a strong defect in root gravitropism. Some alleles also confer an increased root resistance to exogenous ethylene and an increased sensitivity to auxin. AGR1 was cloned and found to encode a putative transmembrane protein which might be involved in polar auxin transport, or in regulating the differential growth response to gravistimulation. When Arabidopsis seedlings grow on the surface of agar-based media tilted backward, their roots wave. That wavy pattern of root growth derives from a combined response to gravity, touch and other surface-derived stimuli. It is accompanied by a reversible rotation of the root tip about its axis. A number of mutations affect the presence or the shape of root waves on tilted agar-based surfaces. One of them, wvc1, promotes the formation of compressed root waves under these conditions. The physiological and molecular analyses of this mutant suggest that a tryptophan-derived molecule other than IAA might be an important regulator of the curvature responsible for root waving.

  15. Functional and Genetic Analysis Identify a Role for Arabidopsis ARGONAUTE5 in Antiviral RNA Silencing

    PubMed Central

    Brosseau, Chantal; Moffett, Peter

    2015-01-01

    RNA silencing functions as an antiviral defense through the action of DICER-like (DCL) and ARGONAUTE (AGO) proteins. In turn, plant viruses have evolved strategies to counteract this defense mechanism, including the expression of suppressors of RNA silencing. Potato virus X (PVX) does not systemically infect Arabidopsis thaliana Columbia-0, but is able to do so effectively in mutants lacking at least two of the four Arabidopsis DCL proteins. PVX can also infect Arabidopsis ago2 mutants, albeit less effectively than double DCL mutants, suggesting that additional AGO proteins may mediate anti-viral defenses. Here we show, using functional assays, that all Arabidopsis AGO proteins have the potential to target PVX lacking its viral suppressor of RNA silencing (VSR), P25, but that only AGO2 and AGO5 are able to target wild-type PVX. However, P25 directly affects only a small subset of AGO proteins, and we present evidence indicating that its protective effect is mediated by precluding AGO proteins from accessing viral RNA, as well as by directly inhibiting the RNA silencing machinery. In agreement with functional assays, we show that Potexvirus infection induces AGO5 expression and that both AGO2 and AGO5 are required for full restriction of PVX infection in systemic tissues of Arabidopsis. PMID:26023161

  16. Azospirillum brasilense ameliorates the response of Arabidopsis thaliana to drought mainly via enhancement of ABA levels.

    PubMed

    Cohen, Ana C; Bottini, Rubén; Pontin, Mariela; Berli, Federico J; Moreno, Daniela; Boccanlandro, Hernán; Travaglia, Claudia N; Piccoli, Patricia N

    2015-01-01

    Production of phytohormones is one of the main mechanisms to explain the beneficial effects of plant growth-promoting rhizobacteria (PGPR) such as Azospirillum sp. The PGPRs induce plant growth and development, and reduce stress susceptibility. However, little is known regarding the stress-related phytohormone abscisic acid (ABA) produced by bacteria. We investigated the effects of Azospirillum brasilense Sp 245 strain on Arabidopsis thaliana Col-0 and aba2-1 mutant plants, evaluating the morphophysiological and biochemical responses when watered and in drought. We used an in vitro-grown system to study changes in the root volume and architecture after inoculation with Azospirillum in Arabidopsis wild-type Col-0 and on the mutant aba2-1, during early growth. To examine Arabidopsis development and reproductive success as affected by the bacteria, ABA and drought, a pot experiment using Arabidopsis Col-0 plants was also carried out. Azospirillum brasilense augmented plant biomass, altered root architecture by increasing lateral roots number, stimulated photosynthetic and photoprotective pigments and retarded water loss in correlation with incremented ABA levels. As well, inoculation improved plants seed yield, plants survival, proline levels and relative leaf water content; it also decreased stomatal conductance, malondialdehyde and relative soil water content in plants submitted to drought. Arabidopsis inoculation with A. brasilense improved plants performance, especially in drought. PMID:24796562

  17. Functional and Genetic Analysis Identify a Role for Arabidopsis ARGONAUTE5 in Antiviral RNA Silencing.

    PubMed

    Brosseau, Chantal; Moffett, Peter

    2015-06-01

    RNA silencing functions as an antiviral defense through the action of DICER-like (DCL) and ARGONAUTE (AGO) proteins. In turn, plant viruses have evolved strategies to counteract this defense mechanism, including the expression of suppressors of RNA silencing. Potato virus X (PVX) does not systemically infect Arabidopsis thaliana Columbia-0, but is able to do so effectively in mutants lacking at least two of the four Arabidopsis DCL proteins. PVX can also infect Arabidopsis ago2 mutants, albeit less effectively than double DCL mutants, suggesting that additional AGO proteins may mediate anti-viral defenses. Here we show, using functional assays, that all Arabidopsis AGO proteins have the potential to target PVX lacking its viral suppressor of RNA silencing (VSR), P25, but that only AGO2 and AGO5 are able to target wild-type PVX. However, P25 directly affects only a small subset of AGO proteins, and we present evidence indicating that its protective effect is mediated by precluding AGO proteins from accessing viral RNA, as well as by directly inhibiting the RNA silencing machinery. In agreement with functional assays, we show that Potexvirus infection induces AGO5 expression and that both AGO2 and AGO5 are required for full restriction of PVX infection in systemic tissues of Arabidopsis. PMID:26023161

  18. Arabidopsis COPPER MODIFIED RESISTANCE1/PATRONUS1 is essential for growth adaptation to stress and required for mitotic onset control.

    PubMed

    Juraniec, Michal; Heyman, Jefri; Schubert, Veit; Salis, Pietrino; De Veylder, Lieven; Verbruggen, Nathalie

    2016-01-01

    The mitotic checkpoint (MC) guards faithful sister chromatid segregation by monitoring the attachment of spindle microtubules to the kinetochores. When chromosome attachment errors are detected, MC delays the metaphase-to-anaphase transition through the inhibition of the anaphase-promoting complex/cyclosome (APC/C) ubiquitin ligase. In contrast to yeast and mammals, our knowledge on the proteins involved in MC in plants is scarce. Transient synchronization of root tips as well as promoter-reporter gene fusions were performed to analyze temporal and spatial expression of COPPER MODIFIED RESISTANCE1/PATRONUS1 (CMR1/PANS1) in developing Arabidopsis thaliana seedlings. Functional analysis of the gene was carried out, including CYCB1;2 stability in CMR1/PANS1 knockout and overexpressor background as well as metaphase-anaphase chromosome status. CMR1/PANS1 is transcriptionally active during M phase. Its deficiency provokes premature cell cycle exit and in consequence a rapid consumption of the number of meristematic cells in particular under stress conditions that are known to affect spindle microtubules. Root growth impairment is correlated with a failure to delay the onset of anaphase, resulting in anaphase bridges and chromosome missegregation. CMR1/PANS1 overexpression stabilizes the mitotic CYCB1;2 protein. Likely, CMR1/PANS1 coordinates mitotic cell cycle progression by acting as an APC/C inhibitor and plays a key role in growth adaptation to stress. PMID:26261921

  19. A Chemical Genetic Screening Procedure for Arabidopsis thaliana Seedlings

    PubMed Central

    Bjornson, Marta; Song, Xingshun; Dandekar, Abhaya; Franz, Annaliese; Drakakaki, Georgia; Dehesh, Katayoon

    2016-01-01

    Unbiased screening approaches are powerful tools enabling identification of novel players in biological processes. Chemical genetic screening refers to the technique of using a reporter response, such as expression of luciferase driven by a promoter of interest, to discover small molecules that affect a given process when applied to plants. These chemicals then act as tools for identification of regulatory components that could not otherwise be detected by forward genetic screens due to gene family redundancy or mutant lethality. This protocol describes a chemical genetic screen using Arabidopsis thaliana seedlings, which has led to recognition of novel players in the plant general stress response.

  20. A new cyanogenic metabolite in Arabidopsis required for inducible pathogen defense

    PubMed Central

    Rajniak, Jakub; Barco, Brenden; Clay, Nicole K.; Sattely, Elizabeth S.

    2015-01-01

    SUMMARY Thousands of putative biosynthetic genes in Arabidopsis thaliana have no known function, suggesting that there are numerous molecules contributing to plant fitness that have not yet been discovered1,2. Prime among these uncharacterized genes are cytochromes P450 upregulated in response to pathogens3,4. Starting with a single pathogen-induced P4505, CYP82C2, we used a combination of untargeted metabolomics and co-expression analysis to uncover the complete biosynthetic pathway to a previously unknown Arabidopsis metabolite, 4-hydroxyindole-3-carbonyl nitrile (4-OH-ICN), which harbors cyanogenic functionality that is unprecedented in plants and exceedingly rare in nature6,7. The aryl cyanohydrin intermediate in the 4-OH-ICN pathway reveals a latent capacity for cyanogenic glucoside biosynthesis8,9 in Arabidopsis. By expressing 4-OH-ICN biosynthetic enzymes in Saccharomyces cerevisiae and Nicotiana benthamiana, we reconstitute the complete pathway in vitro and in vivo and validate the functions of its enzymes. 4-OH-ICN pathway mutants show increased susceptibility to the bacterial pathogen Pseudomonas syringae, consistent with a role in inducible pathogen defense. Arabidopsis has been the preeminent model system10,11 for studying the role of small molecules in plant innate immunity12; our results uncover a new branch of indole metabolism distinct from the canonical camalexin pathway, and support a role for this pathway in the Arabidopsis defense response.13 These results establish a more complete framework for understanding how the model plant Arabidopsis uses small molecules in pathogen defense. PMID:26352477

  1. Defects in Peroxisomal 6-Phosphogluconate Dehydrogenase Isoform PGD2 Prevent Gametophytic Interaction in Arabidopsis thaliana1[OPEN

    PubMed Central

    Hölscher, Christian; Meyer, Tanja; Fischer, Kerstin

    2016-01-01

    We studied the localization of 6-phosphogluconate dehydrogenase (PGD) isoforms of Arabidopsis (Arabidopsis thaliana). Similar polypeptide lengths of PGD1, PGD2, and PGD3 obscured which isoform may represent the cytosolic and/or plastidic enzyme plus whether PGD2 with a peroxisomal targeting motif also might target plastids. Reporter-fusion analyses in protoplasts revealed that, with a free N terminus, PGD1 and PGD3 accumulate in the cytosol and chloroplasts, whereas PGD2 remains in the cytosol. Mutagenesis of a conserved second ATG enhanced the plastidic localization of PGD1 and PGD3 but not PGD2. Amino-terminal deletions of PGD2 fusions with a free C terminus resulted in peroxisomal import after dimerization, and PGD2 could be immunodetected in purified peroxisomes. Repeated selfing of pgd2 transfer (T-)DNA alleles yielded no homozygous mutants, although siliques and seeds of heterozygous plants developed normally. Detailed analyses of the C-terminally truncated PGD2-1 protein showed that peroxisomal import and catalytic activity are abolished. Reciprocal backcrosses of pgd2-1 suggested that missing PGD activity in peroxisomes primarily affects the male gametophyte. Tetrad analyses in the quartet1-2 background revealed that pgd2-1 pollen is vital and in vitro germination normal, but pollen tube growth inside stylar tissues appeared less directed. Mutual gametophytic sterility was overcome by complementation with a genomic construct but not with a version lacking the first ATG. These analyses showed that peroxisomal PGD2 activity is required for guided growth of the male gametophytes and pollen tube-ovule interaction. Our report finally demonstrates an essential role of oxidative pentose-phosphate pathway reactions in peroxisomes, likely needed to sustain critical levels of nitric oxide and/or jasmonic acid, whose biosynthesis both depend on NADPH provision. PMID:26941195

  2. Taxonomy and Phylogeny of Arabidopsis (Brassicaceae)

    PubMed Central

    Al-Shehbaz, Ihsan A.; O'Kane, Steve L.

    2002-01-01

    Detailed taxonomic, cytological, and phylogenetic accounts of Arabidopsis are presented. As currently delimited, the genus consists of nine species all of which are indigenous to Europe, with the ranges of two species extending into northern and eastern Asia and North American into central United States. A survey of chromosome numbers in the genus is presented, and the country of origin for each count is given. Detailed descriptions of all species and subspecies and keys to all taxa are provided. Generic assignments are updated for the 50 species previously included in Arabidopsis. A cladogram of the species of Arabidopsis based on molecular phylogenetic studies by the authors is given. PMID:22303187

  3. Sulfenome mining in Arabidopsis thaliana.

    PubMed

    Waszczak, Cezary; Akter, Salma; Eeckhout, Dominique; Persiau, Geert; Wahni, Khadija; Bodra, Nandita; Van Molle, Inge; De Smet, Barbara; Vertommen, Didier; Gevaert, Kris; De Jaeger, Geert; Van Montagu, Marc; Messens, Joris; Van Breusegem, Frank

    2014-08-01

    Reactive oxygen species (ROS) have been shown to be potent signaling molecules. Today, oxidation of cysteine residues is a well-recognized posttranslational protein modification, but the signaling processes steered by such oxidations are poorly understood. To gain insight into the cysteine thiol-dependent ROS signaling in Arabidopsis thaliana, we identified the hydrogen peroxide (H2O2)-dependent sulfenome: that is, proteins with at least one cysteine thiol oxidized to a sulfenic acid. By means of a genetic construct consisting of a fusion between the C-terminal domain of the yeast (Saccharomyces cerevisiae) AP-1-like (YAP1) transcription factor and a tandem affinity purification tag, we detected ∼ 100 sulfenylated proteins in Arabidopsis cell suspensions exposed to H2O2 stress. The in vivo YAP1-based trapping of sulfenylated proteins was validated by a targeted in vitro analysis of dehydroascorbate reductase2 (DHAR2). In DHAR2, the active site nucleophilic cysteine is regulated through a sulfenic acid-dependent switch, leading to S-glutathionylation, a protein modification that protects the protein against oxidative damage. PMID:25049418

  4. Genes directing flower development in Arabidopsis.

    PubMed Central

    Bowman, J L; Smyth, D R; Meyerowitz, E M

    1989-01-01

    We describe the effects of four recessive homeotic mutations that specifically disrupt the development of flowers in Arabidopsis thaliana. Each of the recessive mutations affects the outcome of organ development, but not the location of organ primordia. Homeotic transformations observed are as follows. In agamous-1, stamens to petals; in apetala2-1, sepals to leaves and petals to staminoid petals; in apetala3-1, petals to sepals and stamens to carpels; in pistillata-1, petals to sepals. In addition, two of these mutations (ap2-1 and pi-1) result in loss of organs, and ag-1 causes the cells that would ordinarily form the gynoecium to differentiate as a flower. Two of the mutations are temperature-sensitive. Temperature shift experiments indicate that the wild-type AP2 gene product acts at the time of primordium initiation; the AP3 product is active later. It seems that the wild-type alleles of these four genes allow cells to determine their place in the developing flower and thus to differentiate appropriately. We propose that these genes may be involved in setting up or responding to concentric, overlapping fields within the flower primordium. PMID:2535466

  5. The Receptor Kinase IMPAIRED OOMYCETE SUSCEPTIBILITY1 Attenuates Abscisic Acid Responses in Arabidopsis1[C][W

    PubMed Central

    Hok, Sophie; Allasia, Valérie; Andrio, Emilie; Naessens, Elodie; Ribes, Elsa; Panabières, Franck; Attard, Agnès; Ris, Nicolas; Clément, Mathilde; Barlet, Xavier; Marco, Yves; Grill, Erwin; Eichmann, Ruth; Weis, Corina; Hückelhoven, Ralph; Ammon, Alexandra; Ludwig-Müller, Jutta; Voll, Lars M.; Keller, Harald

    2014-01-01

    In plants, membrane-bound receptor kinases are essential for developmental processes, immune responses to pathogens and the establishment of symbiosis. We previously identified the Arabidopsis (Arabidopsis thaliana) receptor kinase IMPAIRED OOMYCETE SUSCEPTIBILITY1 (IOS1) as required for successful infection with the downy mildew pathogen Hyaloperonospora arabidopsidis. We report here that IOS1 is also required for full susceptibility of Arabidopsis to unrelated (hemi)biotrophic filamentous oomycete and fungal pathogens. Impaired susceptibility in the absence of IOS1 appeared to be independent of plant defense mechanism. Instead, we found that ios1-1 plants were hypersensitive to the plant hormone abscisic acid (ABA), displaying enhanced ABA-mediated inhibition of seed germination, root elongation, and stomatal opening. These findings suggest that IOS1 negatively regulates ABA signaling in Arabidopsis. The expression of ABA-sensitive COLD REGULATED and RESISTANCE TO DESICCATION genes was diminished in Arabidopsis during infection. This effect on ABA signaling was alleviated in the ios1-1 mutant background. Accordingly, ABA-insensitive and ABA-hypersensitive mutants were more susceptible and resistant to oomycete infection, respectively, showing that the intensity of ABA signaling affects the outcome of downy mildew disease. Taken together, our findings suggest that filamentous (hemi)biotrophs attenuate ABA signaling in Arabidopsis during the infection process and that IOS1 participates in this pathogen-mediated reprogramming of the host. PMID:25274985

  6. Metabolomic Characterization of Knockout Mutants in Arabidopsis: Development of a Metabolite Profiling Database for Knockout Mutants in Arabidopsis1[W][OPEN

    PubMed Central

    Fukushima, Atsushi; Kusano, Miyako; Mejia, Ramon Francisco; Iwasa, Mami; Kobayashi, Makoto; Hayashi, Naomi; Watanabe-Takahashi, Akiko; Narisawa, Tomoko; Tohge, Takayuki; Hur, Manhoi; Wurtele, Eve Syrkin; Nikolau, Basil J.; Saito, Kazuki

    2014-01-01

    Despite recent intensive research efforts in functional genomics, the functions of only a limited number of Arabidopsis (Arabidopsis thaliana) genes have been determined experimentally, and improving gene annotation remains a major challenge in plant science. As metabolite profiling can characterize the metabolomic phenotype of a genetic perturbation in the plant metabolism, it provides clues to the function(s) of genes of interest. We chose 50 Arabidopsis mutants, including a set of characterized and uncharacterized mutants, that resemble wild-type plants. We performed metabolite profiling of the plants using gas chromatography-mass spectrometry. To make the data set available as an efficient public functional genomics tool for hypothesis generation, we developed the Metabolite Profiling Database for Knock-Out Mutants in Arabidopsis (MeKO). It allows the evaluation of whether a mutation affects metabolism during normal plant growth and contains images of mutants, data on differences in metabolite accumulation, and interactive analysis tools. Nonprocessed data, including chromatograms, mass spectra, and experimental metadata, follow the guidelines set by the Metabolomics Standards Initiative and are freely downloadable. Proof-of-concept analysis suggests that MeKO is highly useful for the generation of hypotheses for genes of interest and for improving gene annotation. MeKO is publicly available at http://prime.psc.riken.jp/meko/. PMID:24828308

  7. The fifth international conference on Arabidopsis research

    SciTech Connect

    Hangarter, R.; Scholl, R.; Davis, K.; Feldmann, K.

    1993-12-31

    This volume contains abstracts of oral and poster presentations made in conjunction with the Fifth International Conference on Arabidopsis Research held August 19--22, 1993 at the Ohio State University, Columbus, Ohio.

  8. Cytokinins can act as suppressors of nitric oxide in Arabidopsis

    PubMed Central

    Liu, Wei-Zhong; Kong, Dong-Dong; Gu, Xue-Xin; Gao, Hong-Bo; Wang, Jin-Zheng; Xia, Min; Gao, Qian; Tian, Li-Li; Xu, Zhang-Hong; Bao, Fang; Hu, Yong; Ye, Neng-Sheng; Pei, Zhen-Ming; He, Yi-Kun

    2013-01-01

    Maintaining nitric oxide (NO) homeostasis is essential for normal plant physiological processes. However, very little is known about the mechanisms of NO modulation in plants. Here, we report a unique mechanism for the catabolism of NO based on the reaction with the plant hormone cytokinin. We screened for NO-insensitive mutants in Arabidopsis and isolated two allelic lines, cnu1-1 and 1–2 (continuous NO-unstressed 1), that were identified as the previously reported altered meristem program 1 (amp1) and as having elevated levels of cytokinins. A double mutant of cnu1-2 and nitric oxide overexpression 1 (nox1) reduced the severity of the phenotypes ascribed to excess NO levels as did treating the nox1 line with trans-zeatin, the predominant form of cytokinin in Arabidopsis. We further showed that peroxinitrite, an active NO derivative, can react with zeatin in vitro, which together with the results in vivo suggests that cytokinins suppress the action of NO most likely through direct interaction between them, leading to the reduction of endogenous NO levels. These results provide insights into NO signaling and regulation of its bioactivity in plants. PMID:23319631

  9. BODYGUARD is required for the biosynthesis of cutin in Arabidopsis.

    PubMed

    Jakobson, Liina; Lindgren, Leif Ove; Verdier, Gaëtan; Laanemets, Kristiina; Brosché, Mikael; Beisson, Fred; Kollist, Hannes

    2016-07-01

    The cuticle plays a critical role in plant survival during extreme drought conditions. There are, however, surprisingly, many gaps in our understanding of cuticle biosynthesis. An Arabidopsis thaliana T-DNA mutant library was screened for mutants with enhanced transpiration using a simple condensation spot method. Five mutants, named cool breath (cb), were isolated. The cb5 mutant was found to be allelic to bodyguard (bdg), which is affected in an α/β-hydrolase fold protein important for cuticle structure. The analysis of cuticle components in cb5 (renamed as bdg-6) and another T-DNA mutant allele (bdg-7) revealed no impairment in wax synthesis, but a strong decrease in total cutin monomer load in young leaves and flowers. Root suberin content was also reduced. Overexpression of BDG increased total leaf cutin monomer content nearly four times by affecting preferentially C18 polyunsaturated ω-OH fatty acids and dicarboxylic acids. Whole-plant gas exchange analysis showed that bdg-6 had higher cuticular conductance and rate of transpiration; however, plant lines overexpressing BDG resembled the wild-type with regard to these characteristics. This study identifies BDG as an important component of the cutin biosynthesis machinery in Arabidopsis. We also show that, using BDG, cutin can be greatly modified without altering the cuticular water barrier properties and transpiration. PMID:26990896

  10. 44 CFR 1.2 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ..., appliances, services, or allowances therefor or to valuations, costs or accounting, or practices relating to... 44 Emergency Management and Assistance 1 2011-10-01 2011-10-01 false Definitions. 1.2 Section 1.2 Emergency Management and Assistance FEDERAL EMERGENCY MANAGEMENT AGENCY, DEPARTMENT OF HOMELAND...

  11. 24 CFR 1.2 - Definitions.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... participates in carrying out such program or activity (such as a redeveloper in the Urban Renewal Program... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false Definitions. 1.2 Section 1.2 Housing and Urban Development Office of the Secretary, Department of Housing and Urban...

  12. 24 CFR 1.2 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... participates in carrying out such program or activity (such as a redeveloper in the Urban Renewal Program... 24 Housing and Urban Development 1 2013-04-01 2013-04-01 false Definitions. 1.2 Section 1.2 Housing and Urban Development Office of the Secretary, Department of Housing and Urban...

  13. 24 CFR 1.2 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... participates in carrying out such program or activity (such as a redeveloper in the Urban Renewal Program... 24 Housing and Urban Development 1 2014-04-01 2014-04-01 false Definitions. 1.2 Section 1.2 Housing and Urban Development Office of the Secretary, Department of Housing and Urban...

  14. 24 CFR 1.2 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... participates in carrying out such program or activity (such as a redeveloper in the Urban Renewal Program... 24 Housing and Urban Development 1 2012-04-01 2012-04-01 false Definitions. 1.2 Section 1.2 Housing and Urban Development Office of the Secretary, Department of Housing and Urban...

  15. 24 CFR 1.2 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... participates in carrying out such program or activity (such as a redeveloper in the Urban Renewal Program... 24 Housing and Urban Development 1 2011-04-01 2011-04-01 false Definitions. 1.2 Section 1.2 Housing and Urban Development Office of the Secretary, Department of Housing and Urban...

  16. 44 CFR 1.2 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 44 Emergency Management and Assistance 1 2014-10-01 2014-10-01 false Definitions. 1.2 Section 1.2 Emergency Management and Assistance FEDERAL EMERGENCY MANAGEMENT AGENCY, DEPARTMENT OF HOMELAND SECURITY... Emergency Management Agency. (e) Major rule means any regulation that is likely to result in: (1) An...

  17. 44 CFR 1.2 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 44 Emergency Management and Assistance 1 2012-10-01 2011-10-01 true Definitions. 1.2 Section 1.2 Emergency Management and Assistance FEDERAL EMERGENCY MANAGEMENT AGENCY, DEPARTMENT OF HOMELAND SECURITY... Emergency Management Agency. (e) Major rule means any regulation that is likely to result in: (1) An...

  18. 44 CFR 1.2 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 44 Emergency Management and Assistance 1 2013-10-01 2013-10-01 false Definitions. 1.2 Section 1.2 Emergency Management and Assistance FEDERAL EMERGENCY MANAGEMENT AGENCY, DEPARTMENT OF HOMELAND SECURITY... Emergency Management Agency. (e) Major rule means any regulation that is likely to result in: (1) An...

  19. A Lipid Transfer Protein Increases the Glutathione Content and Enhances Arabidopsis Resistance to a Trichothecene Mycotoxin.

    PubMed

    McLaughlin, John E; Bin-Umer, Mohamed Anwar; Widiez, Thomas; Finn, Daniel; McCormick, Susan; Tumer, Nilgun E

    2015-01-01

    Fusarium head blight (FHB) or scab is one of the most important plant diseases worldwide, affecting wheat, barley and other small grains. Trichothecene mycotoxins such as deoxynivalenol (DON) accumulate in the grain, presenting a food safety risk and health hazard to humans and animals. Despite considerable breeding efforts, highly resistant wheat or barley cultivars are not available. We screened an activation tagged Arabidopsis thaliana population for resistance to trichothecin (Tcin), a type B trichothecene in the same class as DON. Here we show that one of the resistant lines identified, trichothecene resistant 1 (trr1) contains a T-DNA insertion upstream of two nonspecific lipid transfer protein (nsLTP) genes, AtLTP4.4 and AtLTP4.5. Expression of both nsLTP genes was induced in trr1 over 10-fold relative to wild type. Overexpression of AtLTP4.4 provided greater resistance to Tcin than AtLTP4.5 in Arabidopsis thaliana and in Saccharomyces cerevisiae relative to wild type or vector transformed lines, suggesting a conserved protection mechanism. Tcin treatment increased reactive oxygen species (ROS) production in Arabidopsis and ROS stain was associated with the chloroplast, the cell wall and the apoplast. ROS levels were attenuated in Arabidopsis and in yeast overexpressing AtLTP4.4 relative to the controls. Exogenous addition of glutathione and other antioxidants enhanced resistance of Arabidopsis to Tcin while the addition of buthionine sulfoximine, an inhibitor of glutathione synthesis, increased sensitivity, suggesting that resistance was mediated by glutathione. Total glutathione content was significantly higher in Arabidopsis and in yeast overexpressing AtLTP4.4 relative to the controls, highlighting the importance of AtLTP4.4 in maintaining the redox state. These results demonstrate that trichothecenes cause ROS accumulation and overexpression of AtLTP4.4 protects against trichothecene-induced oxidative stress by increasing the glutathione

  20. A Lipid Transfer Protein Increases the Glutathione Content and Enhances Arabidopsis Resistance to a Trichothecene Mycotoxin

    PubMed Central

    McLaughlin, John E.; Bin-Umer, Mohamed Anwar; Widiez, Thomas; Finn, Daniel; McCormick, Susan; Tumer, Nilgun E.

    2015-01-01

    Fusarium head blight (FHB) or scab is one of the most important plant diseases worldwide, affecting wheat, barley and other small grains. Trichothecene mycotoxins such as deoxynivalenol (DON) accumulate in the grain, presenting a food safety risk and health hazard to humans and animals. Despite considerable breeding efforts, highly resistant wheat or barley cultivars are not available. We screened an activation tagged Arabidopsis thaliana population for resistance to trichothecin (Tcin), a type B trichothecene in the same class as DON. Here we show that one of the resistant lines identified, trichothecene resistant 1 (trr1) contains a T-DNA insertion upstream of two nonspecific lipid transfer protein (nsLTP) genes, AtLTP4.4 and AtLTP4.5. Expression of both nsLTP genes was induced in trr1 over 10-fold relative to wild type. Overexpression of AtLTP4.4 provided greater resistance to Tcin than AtLTP4.5 in Arabidopsis thaliana and in Saccharomyces cerevisiae relative to wild type or vector transformed lines, suggesting a conserved protection mechanism. Tcin treatment increased reactive oxygen species (ROS) production in Arabidopsis and ROS stain was associated with the chloroplast, the cell wall and the apoplast. ROS levels were attenuated in Arabidopsis and in yeast overexpressing AtLTP4.4 relative to the controls. Exogenous addition of glutathione and other antioxidants enhanced resistance of Arabidopsis to Tcin while the addition of buthionine sulfoximine, an inhibitor of glutathione synthesis, increased sensitivity, suggesting that resistance was mediated by glutathione. Total glutathione content was significantly higher in Arabidopsis and in yeast overexpressing AtLTP4.4 relative to the controls, highlighting the importance of AtLTP4.4 in maintaining the redox state. These results demonstrate that trichothecenes cause ROS accumulation and overexpression of AtLTP4.4 protects against trichothecene-induced oxidative stress by increasing the glutathione

  1. Requirement of Functional Ethylene-Insensitive 2 Gene for Efficient Resistance of Arabidopsis to Infection by Botrytis cinerea1

    PubMed Central

    Thomma, Bart P.H.J.; Eggermont, Kristel; Tierens, Koenraad F.M.-J.; Broekaert, Willem F.

    1999-01-01

    Inoculation of wild-type Arabidopsis plants with the fungus Alternaria brassicicola results in systemic induction of genes encoding a plant defensin (PDF1.2), a basic chitinase (PR-3), and an acidic hevein-like protein (PR-4). Pathogen-induced induction of these three genes is almost completely abolished in the ethylene-insensitive Arabidopsis mutant ein2-1. This indicates that a functional ethylene signal transduction component (EIN2) is required in this response. The ein2-1 mutants were found to be markedly more susceptible than wild-type plants to infection by two different strains of the gray mold fungus Botrytis cinerea. In contrast, no increased fungal colonization of ein2-1 mutants was observed after challenge with avirulent strains of either Peronospora parasitica or A. brassicicola. Our data support the conclusion that ethylene-controlled responses play a role in resistance of Arabidopsis to some but not all types of pathogens. PMID:10594097

  2. Cell Cycle Modulation in the Response of the Primary Root of Arabidopsis to Salt Stress1

    PubMed Central

    West, Gerrit; Inzé, Dirk; Beemster, Gerrit T.S.

    2004-01-01

    Salt stress inhibits plant growth and development. We investigated the importance of cell cycle regulation in mediating the primary root growth response of Arabidopsis to salt stress. When seedlings were transferred to media with increasing concentrations of NaCl, root growth rate was progressively reduced. At day 3 after transfer of seedlings to growth medium containing 0.5% NaCl the primary roots grew at a constant rate well below that prior to the transfer, whereas those transferred to control medium kept accelerating. Kinematic analysis revealed that the growth reduction of the stressed roots was due to a decrease in cell production and a smaller mature cell length. Surprisingly, average cell cycle duration was not affected. Hence, the reduced cell production was due to a smaller number of dividing cells, i.e. a meristem size reduction. To analyze the mechanism of meristem size adaptation prior to day 3, we investigated the short-term cell cycle events following transfer to saline medium. Directly after transfer cyclin-dependent kinase (CDK) activity and CYCB1;2 promoter activity were transiently reduced. Because protein levels of both CDKA;1 and CDKB1;1 were not affected, the temporary inhibition of mitotic activity that allows adaptation to the stress condition is most likely mediated by posttranslational control of CDK activity. Thus, the adaptation to salt stress involves two phases: first, a rapid transient inhibition of the cell cycle that results in fewer cells remaining in the meristem. When the meristem reaches the appropriate size for the given conditions, cell cycle duration returns to its default. PMID:15181207

  3. EDS1 contributes to nonhost resistance of Arabidopsis thaliana against Erwinia amylovora.

    PubMed

    Moreau, Manon; Degrave, Alexandre; Vedel, Régine; Bitton, Frédérique; Patrit, Oriane; Renou, Jean-Pierre; Barny, Marie-Anne; Fagard, Mathilde

    2012-03-01

    Erwinia amylovora causes fire blight in rosaceous plants. In nonhost Arabidopsis thaliana, E. amylovora triggers necrotic symptoms associated with transient bacterial multiplication, suggesting either that A. thaliana lacks a susceptibility factor or that it actively restricts E. amylovora growth. Inhibiting plant protein synthesis at the time of infection led to an increase in necrosis and bacterial multiplication and reduced callose deposition, indicating that A. thaliana requires active protein synthesis to restrict E. amylovora growth. Analysis of the callose synthase-deficient pmr4-1 mutant indicated that lack of callose deposition alone did not lead to increased sensitivity to E. amylovora. Transcriptome analysis revealed that approximately 20% of the genes induced following E. amylovora infection are related to defense and signaling. Analysis of mutants affected in NDR1 and EDS1, two main components of the defense-gene activation observed, revealed that E. amylovora multiplied ten times more in the eds1-2 mutant than in the wild type but not in the ndr1-1 mutant. Analysis of mutants affected in three WRKY transcription factors showing EDS1-dependent activation identified WRKY46 and WRKY54 as positive regulators and WRKY70 as a negative regulator of defense against E. amylovora. Altogether, we show that EDS1 is a positive regulator of nonhost resistance against E. amylovora in A. thaliana and hypothesize that it controls the production of several effective defenses against E. amylovora through the action of WRKY46 and WRKY54, while WRKY70 acts as a negative regulator. PMID:22316300

  4. Tetrapyrrole Metabolism in Arabidopsis thaliana

    PubMed Central

    Tanaka, Ryouichi; Kobayashi, Koichi; Masuda, Tatsuru

    2011-01-01

    Higher plants produce four classes of tetrapyrroles, namely, chlorophyll (Chl), heme, siroheme, and phytochromobilin. In plants, tetrapyrroles play essential roles in a wide range of biological activities including photosynthesis, respiration and the assimilation of nitrogen/sulfur. All four classes of tetrapyrroles are derived from a common biosynthetic pathway that resides in the plastid. In this article, we present an overview of tetrapyrrole metabolism in Arabidopsis and other higher plants, and we describe all identified enzymatic steps involved in this metabolism. We also summarize recent findings on Chl biosynthesis and Chl breakdown. Recent advances in this field, in particular those on the genetic and biochemical analyses of novel enzymes, prompted us to redraw the tetrapyrrole metabolic pathways. In addition, we also summarize our current understanding on the regulatory mechanisms governing tetrapyrrole metabolism. The interactions of tetrapyrrole biosynthesis and other cellular processes including the plastid-to-nucleus signal transduction are discussed. PMID:22303270

  5. Apoplastic Diffusion Barriers in Arabidopsis

    PubMed Central

    Schreiber, Lukas; Franke, Rochus Benni; Geldner, Niko; Reina-Pinto, José J.; Kunst, Ljerka

    2013-01-01

    During the development of Arabidopsis and other land plants, diffusion barriers are formed in the apoplast of specialized tissues within a variety of plant organs. While the cuticle of the epidermis is the primary diffusion barrier in the shoot, the Casparian strips and suberin lamellae of the endodermis and the periderm represent the diffusion barriers in the root. Different classes of molecules contribute to the formation of extracellular diffusion barriers in an organ- and tissue-specific manner. Cutin and wax are the major components of the cuticle, lignin forms the early Casparian strip, and suberin is deposited in the stage II endodermis and the periderm. The current status of our understanding of the relationships between the chemical structure, ultrastructure and physiological functions of plant diffusion barriers is discussed. Specific aspects of the synthesis of diffusion barrier components and protocols that can be used for the assessment of barrier function and important barrier properties are also presented. PMID:24465172

  6. Control of Arabidopsis Root Development

    PubMed Central

    Petricka, Jalean J.; Winter, Cara M.; Benfey, Philip N.

    2013-01-01

    The Arabidopsis root has been the subject of intense research over the past decades. This research has led to significantly improved understanding of the molecular mechanisms underlying root development. Key insights into the specification of individual cell types, cell patterning, growth and differentiation, branching of the primary root, and responses of the root to the environment have been achieved. Transcription factors and plant hormones play key regulatory roles. Recently, mechanisms involving protein movement and the oscillation of gene expression have also been uncovered. Root gene regulatory networks controlling root development have been reconstructed from genome-wide profiling experiments, revealing novel molecular connections and models. Future refinement of these models will lead to a more complete description of the complex molecular interactions that give rise to a simple growing root. PMID:22404466

  7. Isolation of Arabidopsis mutants with altered seed fatty acid composition

    SciTech Connect

    Lemieux, B.; Browse, J.; Somerville, C. Washington State Univ., Pullman )

    1989-04-01

    By direct screening of Arabidopsis seed fatty acid methyl esters, we have isolated mutants which are deficient in the elongation of 18:1 to 20:1 and the desaturation of 18:2 to 18:3. Both the elongation and the desaturation mutants, designated MB14 and BL1 respectively, have only 10% of the wild-type levels of 20:1 and 18:3 in their seeds. The intermediate levels of 20:1 and 18:3 in F1 seeds of crosses to the wild type indicate that the level of enzyme is regulating the amount of 20:1 and 18:3 in seeds. Consistent with this observation, the mutations were found to segregate 1:2:1 in F2 seeds. We have found that the 18:2 desaturase mutation is clearly expressed in root phosphatidylcholine.

  8. Nitrate-Regulated Glutaredoxins Control Arabidopsis Primary Root Growth.

    PubMed

    Patterson, Kurt; Walters, Laura A; Cooper, Andrew M; Olvera, Jocelyn G; Rosas, Miguel A; Rasmusson, Allan G; Escobar, Matthew A

    2016-02-01

    Nitrogen is an essential soil nutrient for plants, and lack of nitrogen commonly limits plant growth. Soil nitrogen is typically available to plants in two inorganic forms: nitrate and ammonium. To better understand how nitrate and ammonium differentially affect plant metabolism and development, we performed transcriptional profiling of the shoots of ammonium-supplied and nitrate-supplied Arabidopsis (Arabidopsis thaliana) plants. Seven genes encoding class III glutaredoxins were found to be strongly and specifically induced by nitrate. RNA silencing of four of these glutaredoxin genes (AtGRXS3/4/5/8) resulted in plants with increased primary root length (approximately 25% longer than the wild type) and decreased sensitivity to nitrate-mediated inhibition of primary root growth. Increased primary root growth is also a well-characterized phenotype of many cytokinin-deficient plant lines. We determined that nitrate induction of glutaredoxin gene expression was dependent upon cytokinin signaling and that cytokinins could activate glutaredoxin gene expression independent of plant nitrate status. In addition, crosses between "long-root" cytokinin-deficient plants and "long-root" glutaredoxin-silenced plants generated hybrids that displayed no further increase in primary root length (i.e. epistasis). Collectively, these findings suggest that AtGRXS3/4/5/8 operate downstream of cytokinins in a signal transduction pathway that negatively regulates plant primary root growth in response to nitrate. This pathway could allow Arabidopsis to actively discriminate between different nitrogen sources in the soil, with the preferred nitrogen source, nitrate, acting to suppress primary root growth (vertical dimension) in concert with its well-characterized stimulatory effect on lateral root growth (horizontal dimension). PMID:26662603

  9. Overexpression of GmHsp90s, a heat shock protein 90 (Hsp90) gene family cloning from soybean, decrease damage of abiotic stresses in Arabidopsis thaliana.

    PubMed

    Xu, Jinyan; Xue, Chenchen; Xue, Dong; Zhao, Jinming; Gai, Junyi; Guo, Na; Xing, Han

    2013-01-01

    Hsp90 is one of the most conserved and abundant molecular chaperones and is an essential component of the protective stress response; however, its roles in abiotic stress responses in soybean (Glycine max) remain obscure. Here, 12 GmHsp90 genes from soybean were identified and found to be expressed and to function differentially under abiotic stresses. The 12 GmHsp90 genes were isolated and named GmHsp90A1-GmHsp90A6, GmHsp90B1, GmHsp90B2, GmHsp90C1.1, GmHsp90C1.2, GmHsp90C2.1 and GmHsp90C2.2 based on their characteristics and high homology to other Hsp90s according to a new nomenclature system. Quantitative real-time PCR expression data revealed that all the genes exhibited higher transcript levels in leaves and could be strongly induced under heat, osmotic and salt stress but not cold stress. Overexpression of five typical genes (GmHsp90A2, GmHsp90A4, GmHsp90B1, GmHsp90C1.1 and GmHsp90C2.1) in Arabidopsis thaliana provided useful evidences that GmHsp90 genes can decrease damage of abiotic stresses. In addition, an abnormal accumulation of proline was detected in some transgenic Arabidopsis plants suggested overexpressing GmHsp90s may affect the synthesis and response system of proline. Our work represents a systematic determination of soybean genes encoding Hsp90s, and provides useful evidence that GmHsp90 genes function differently in response to abiotic stresses and may affect the synthesis and response system of proline. PMID:23936107

  10. Cytosolic Glutamine Synthetase Gln1;2 Is the Main Isozyme Contributing to GS1 Activity and Can Be Up-Regulated to Relieve Ammonium Toxicity1[OPEN

    PubMed Central

    Pedersen, Carsten

    2016-01-01

    Cytosolic GS1 (Gln synthetase) is central for ammonium assimilation in plants. High ammonium treatment enhanced the expression of the GS1 isogene Gln-1;2 encoding a low-affinity high-capacity GS1 protein in Arabidopsis (Arabidopsis thaliana) shoots. Under the same conditions, the expression of the high-affinity low-capacity isoform Gln-1;1 was reduced. The expression of Gln-1;3 did not respond to ammonium treatment while Gln-1;4 and Gln-1;5 isogenes in all cases were expressed at a very low level. Gln-2 was highly expressed in shoots but only at a very low level in roots. To investigate the specific functions of the two isogenes Gln-1;1 and Gln-1;2 in shoots for ammonium detoxification, single and double knock-out mutants were grown under standard N supply or with high ammonium provision. Phenotypes of the single mutant gln1;1 were similar to the wild type, while growth of the gln1;2 single mutant and the gln1;1:gln1;2 double mutant was significantly impaired irrespective of N regime. GS1 activity was significantly reduced in both gln1;2 and gln1;1:gln1;2. Along with this, the ammonium content increased while that of Gln decreased, showing that Gln-1;2 was essential for ammonium assimilation and amino acid synthesis. We conclude that Gln-1;2 is the main isozyme contributing to shoot GS1 activity in vegetative growth stages and can be up-regulated to relieve ammonium toxicity. This reveals, to our knowledge, a novel shoot function of Gln-1;2 in Arabidopsis shoots. PMID:27231101

  11. Cytosolic Glutamine Synthetase Gln1;2 Is the Main Isozyme Contributing to GS1 Activity and Can Be Up-Regulated to Relieve Ammonium Toxicity.

    PubMed

    Guan, Miao; de Bang, Thomas C; Pedersen, Carsten; Schjoerring, Jan K

    2016-07-01

    Cytosolic GS1 (Gln synthetase) is central for ammonium assimilation in plants. High ammonium treatment enhanced the expression of the GS1 isogene Gln-1;2 encoding a low-affinity high-capacity GS1 protein in Arabidopsis (Arabidopsis thaliana) shoots. Under the same conditions, the expression of the high-affinity low-capacity isoform Gln-1;1 was reduced. The expression of Gln-1;3 did not respond to ammonium treatment while Gln-1;4 and Gln-1;5 isogenes in all cases were expressed at a very low level. Gln-2 was highly expressed in shoots but only at a very low level in roots. To investigate the specific functions of the two isogenes Gln-1;1 and Gln-1;2 in shoots for ammonium detoxification, single and double knock-out mutants were grown under standard N supply or with high ammonium provision. Phenotypes of the single mutant gln1;1 were similar to the wild type, while growth of the gln1;2 single mutant and the gln1;1:gln1;2 double mutant was significantly impaired irrespective of N regime. GS1 activity was significantly reduced in both gln1;2 and gln1;1:gln1;2 Along with this, the ammonium content increased while that of Gln decreased, showing that Gln-1;2 was essential for ammonium assimilation and amino acid synthesis. We conclude that Gln-1;2 is the main isozyme contributing to shoot GS1 activity in vegetative growth stages and can be up-regulated to relieve ammonium toxicity. This reveals, to our knowledge, a novel shoot function of Gln-1;2 in Arabidopsis shoots. PMID:27231101

  12. AC conductivity and relaxation mechanism in (Nd1/2Li1/2)(Fe1/2V1/2)O3 ceramics

    NASA Astrophysics Data System (ADS)

    Nath, Susmita; Barik, Subrat Kumar; Choudhary, R. N. P.

    2016-05-01

    In the present study we have synthesized polycrystalline sample of (Nd1/2Li1/2)(Fe1/2V1/2)O3 ceramic by a standard high-temperature solid-state reaction technique. Studies of dielectric and electrical properties of the compound have been carried out in a wide range of temperature (RT - 400 °C) and frequency (1kHz - 1MHz) using complex impedance spectroscopic technique. The imaginary vs. real component of the complex impedance plot (Nyquist plot) of the prepared sample exhibits the existence of grain, grain boundary contributions in the complex electrical parameters and negative temperature coefficient of resistance (NTCR) type behavior like semiconductor. Details study of ac conductivity plot reveals that the material obeys universal Jonscher's power law.

  13. Cisplatin inhibits MEK1/2

    PubMed Central

    Yamamoto, Tetsu; Tsigelny, Igor F.; Götz, Andreas W.; Howell, Stephen B.

    2015-01-01

    Cisplatin (cDDP) is known to bind to the CXXC motif of proteins containing a ferrodoxin-like fold but little is known about its ability to interact with other Cu-binding proteins. MEK1/2 has recently been identified as a Cu-dependent enzyme that does not contain a CXXC motif. We found that cDDP bound to and inhibited the activity of recombinant MEK1 with an IC50 of 0.28 μM and MEK1/2 in whole cells with an IC50 of 37.4 μM. The inhibition of MEK1/2 was relieved by both Cu+1 and Cu+2 in a concentration-dependent manner. cDDP did not inhibit the upstream pathways responsible for activating MEK1/2, and did not cause an acute depletion of cellular Cu that could account for the reduction in MEK1/2 activity. cDDP was found to bind MEK1/2 in whole cells and the extent of binding was augmented by supplementary Cu and reduced by Cu chelation. Molecular modeling predicts 3 Cu and cDDP binding sites and quantum chemistry calculations indicate that cDDP would be expected to displace Cu from each of these sites. We conclude that, at clinically relevant concentrations, cDDP binds to and inhibits MEK1/2 and that both the binding and inhibitory activity are related to its interaction with Cu bound to MEK1/2. This may provide the basis for useful interactions of cDDP with other drugs that inhibit MAPK pathway signaling. PMID:26155939

  14. Bacterial Cyclic β-(1,2)-Glucan Acts in Systemic Suppression of Plant Immune Responses[W

    PubMed Central

    Rigano, Luciano Ariel; Payette, Caroline; Brouillard, Geneviève; Marano, Maria Rosa; Abramowicz, Laura; Torres, Pablo Sebastián; Yun, Maximina; Castagnaro, Atilio Pedro; Oirdi, Mohamed El; Dufour, Vanessa; Malamud, Florencia; Dow, John Maxwell; Bouarab, Kamal; Vojnov, Adrian Alberto

    2007-01-01

    Although cyclic glucans have been shown to be important for a number of symbiotic and pathogenic bacterium–plant interactions, their precise roles are unclear. Here, we examined the role of cyclic β-(1,2)-glucan in the virulence of the black rot pathogen Xanthomonas campestris pv campestris (Xcc). Disruption of the Xcc nodule development B (ndvB) gene, which encodes a glycosyltransferase required for cyclic glucan synthesis, generated a mutant that failed to synthesize extracellular cyclic β-(1,2)-glucan and was compromised in virulence in the model plants Arabidopsis thaliana and Nicotiana benthamiana. Infection of the mutant bacterium in N. benthamiana was associated with enhanced callose deposition and earlier expression of the PATHOGENESIS-RELATED1 (PR-1) gene. Application of purified cyclic β-(1,2)-glucan prior to inoculation of the ndvB mutant suppressed the accumulation of callose deposition and the expression of PR-1 in N. benthamiana and restored virulence in both N. benthamiana and Arabidopsis plants. These effects were seen when cyclic glucan and bacteria were applied either to the same or to different leaves. Cyclic β-(1,2)-glucan–induced systemic suppression was associated with the transport of the molecule throughout the plant. Systemic suppression is a novel counterdefensive strategy that may facilitate pathogen spread in plants and may have important implications for the understanding of plant–pathogen coevolution and for the development of phytoprotection measures. PMID:17601826

  15. Molecular Genetics of Root Thigmoresponsiveness in Arabidopsis thaliana

    NASA Technical Reports Server (NTRS)

    Masson, Patrick H.

    2002-01-01

    The molecular mechanisms that allow plant roots to use gravity and touch as growth guides are investigated. We are using a molecular genetic strategy in Arabidopsis thaliana to study these processes. When Arabidopsis thaliana seedlings grow on tilted hard-agar surfaces, their roots develop a wavy pattern of growth which appears to derive from a succession of left-handed and right-handed circumnutation-like processes triggered by gravity and touch stimulation (Okada and Shimura, 1990; Rutherford et al., 1998; Rutherford and Masson, 1996). Interestingly, mutations that affect root waving on tilted hard-agar surfaces can be identified and characterized. Some of these mutations affect root gravitropism, while others appear to be responsible for the production of abnormal waves (no waves, compressed or square waves, coils) without affecting gravitropism. The specific objectives of this project were to functionally characterize two genes (WVD2 and WVD6) which are required for root waving on tilted agar surfaces, but not for root gravitropism. Specific objectives included a physiological and cytological analysis of the mutants, and molecular cloning and characterization of the corresponding genes. As summarized in this paper, we have reached these objectives. We have also identified and partially characterized other mutations that affect root skewing on hard-agar surfaces (sku5-1 and ago1), and have completed our work on the root-wave phenotype associated with mutations in genes of the tryptophan biosynthesis pathway (Lynn et al., 1999; Rutherford et al., 1998; Sedbrook et al., 2000, 2002). We briefly describe our progress on the cloning and characterization of WVD6, WVD2 and SKU5, and provide a list of papers (published, or in preparation) that derived from this grant. We also discuss the biological implications of our findings, with special emphasis on the analysis of WVD2.

  16. Characterization of nitrite uptake in Arabidopsis thaliana: evidence for a nitrite-specific transporter.

    PubMed

    Kotur, Zorica; Siddiqi, Yaeesh M; Glass, Anthony D M

    2013-10-01

    Nitrite-specific plasma membrane transporters have been described in bacteria, algae and fungi, but there is no evidence of a nitrite-specific plasma membrane transporter in higher plants. We have used 13NO2(-) to characterize nitrite influx into roots of Arabidopsis thaliana. Hydroponically grown Arabidopsis mutants, defective in high-affinity nitrate transport, were used to distinguish between nitrate and nitrite uptake by means of the short-lived tracers 13NO2(-) and 13NO3(-). This approach allowed us to characterize a nitrite-specific transporter. The Atnar2.1-2 mutant, lacking a functional high-affinity nitrate transport system, is capable of nitrite influx that is constitutive and thermodynamically active. The corresponding fluxes conform to a rectangular hyperbola, exhibiting saturation at concentrations above 200 μM (Km = 185 μM and Vmax = 1.89 μmol g(-1) FW h(-1)). Nitrite influx via the putative nitrite transporter is not subject to competitive inhibition by nitrate but is downregulated after 6 h exposure to ammonium. These results signify the existence of a nitrite-specific transporter in Arabidopsis. This transporter enables Atnar2.1-2 mutants, which are incapable of sustained growth on low nitrate, to maintain significant growth on low nitrite. In wild-type plants, this nitrite flux may increase nitrogen acquisition and also participate in the induction of genes specifically induced by nitrite. PMID:23763619

  17. Terpene Specialized Metabolism in Arabidopsis thaliana

    PubMed Central

    Tholl, Dorothea; Lee, Sungbeom

    2011-01-01

    Terpenes constitute the largest class of plant secondary (or specialized) metabolites, which are compounds of ecological function in plant defense or the attraction of beneficial organisms. Using biochemical and genetic approaches, nearly all Arabidopsis thaliana (Arabidopsis) enzymes of the core biosynthetic pathways producing the 5-carbon building blocks of terpenes have been characterized and closer insight has been gained into the transcriptional and posttranscriptional/translational mechanisms regulating these pathways. The biochemical function of most prenyltransferases, the downstream enzymes that condense the C5-precursors into central 10-, 15-, and 20-carbon prenyldiphosphate intermediates, has been described, although the function of several isoforms of C20-prenyltranferases is not well understood. Prenyl diphosphates are converted to a variety of C10-, C15-, and C20-terpene products by enzymes of the terpene synthase (TPS) family. Genomic organization of the 32 Arabidopsis TPS genes indicates a species-specific divergence of terpene synthases with tissue- and cell-type specific expression profiles that may have emerged under selection pressures by different organisms. Pseudogenization, differential expression, and subcellular segregation of TPS genes and enzymes contribute to the natural variation of terpene biosynthesis among Arabidopsis accessions (ecotypes) and species. Arabidopsis will remain an important model to investigate the metabolic organization and molecular regulatory networks of terpene specialized metabolism in relation to the biological activities of terpenes. PMID:22303268

  18. Basipetal auxin transport is required for gravitropism in roots of Arabidopsis

    NASA Technical Reports Server (NTRS)

    Rashotte, A. M.; Brady, S. R.; Reed, R. C.; Ante, S. J.; Muday, G. K.; Davies, E. (Principal Investigator)

    2000-01-01

    Auxin transport has been reported to occur in two distinct polarities, acropetally and basipetally, in two different root tissues. The goals of this study were to determine whether both polarities of indole-3-acetic acid (IAA) transport occur in roots of Arabidopsis and to determine which polarity controls the gravity response. Global application of the auxin transport inhibitor naphthylphthalamic acid (NPA) to roots blocked the gravity response, root waving, and root elongation. Immediately after the application of NPA, the root gravity response was completely blocked, as measured by an automated video digitizer. Basipetal [(3)H]IAA transport in Arabidopsis roots was inhibited by NPA, whereas the movement of [(14)C]benzoic acid was not affected. Inhibition of basipetal IAA transport by local application of NPA blocked the gravity response. Inhibition of acropetal IAA transport by application of NPA at the root-shoot junction only partially reduced the gravity response at high NPA concentrations. Excised root tips, which do not receive auxin from the shoot, exhibited a normal response to gravity. The Arabidopsis mutant eir1, which has agravitropic roots, exhibited reduced basipetal IAA transport but wild-type levels of acropetal IAA transport. These results support the hypothesis that basipetally transported IAA controls root gravitropism in Arabidopsis.

  19. Capturing Arabidopsis root architecture dynamics with ROOT-FIT reveals diversity in responses to salinity.

    PubMed

    Julkowska, Magdalena M; Hoefsloot, Huub C J; Mol, Selena; Feron, Richard; de Boer, Gert-Jan; Haring, Michel A; Testerink, Christa

    2014-11-01

    The plant root is the first organ to encounter salinity stress, but the effect of salinity on root system architecture (RSA) remains elusive. Both the reduction in main root (MR) elongation and the redistribution of the root mass between MRs and lateral roots (LRs) are likely to play crucial roles in water extraction efficiency and ion exclusion. To establish which RSA parameters are responsive to salt stress, we performed a detailed time course experiment in which Arabidopsis (Arabidopsis thaliana) seedlings were grown on agar plates under different salt stress conditions. We captured RSA dynamics with quadratic growth functions (root-fit) and summarized the salt-induced differences in RSA dynamics in three growth parameters: MR elongation, average LR elongation, and increase in number of LRs. In the ecotype Columbia-0 accession of Arabidopsis, salt stress affected MR elongation more severely than LR elongation and an increase in LRs, leading to a significantly altered RSA. By quantifying RSA dynamics of 31 different Arabidopsis accessions in control and mild salt stress conditions, different strategies for regulation of MR and LR meristems and root branching were revealed. Different RSA strategies partially correlated with natural variation in abscisic acid sensitivity and different Na(+)/K(+) ratios in shoots of seedlings grown under mild salt stress. Applying root-fit to describe the dynamics of RSA allowed us to uncover the natural diversity in root morphology and cluster it into four response types that otherwise would have been overlooked. PMID:25271266

  20. Mutations in a new Arabidopsis cyclophilin disrupt its interaction with protein phosphatase 2A

    NASA Technical Reports Server (NTRS)

    Jackson, K.; Soll, D.; Evans, M. L. (Principal Investigator)

    1999-01-01

    The heterotrimeric protein phosphatase 2A (PP2A) is a component of multiple signaling pathways in eukaryotes. Disruption of PP2A activity in Arabidopsis is known to alter auxin transport and growth response pathways. We demonstrated that the regulatory subunit A of an Arabidopsis PP2A interacts with a novel cyclophilin, ROC7. The gene for this cyclophilin encodes a protein that contains a unique 30-amino acid extension at the N-terminus, which distinguishes the gene product from all previously identified Arabidopsis cyclophilins. Altered forms of ROC7 cyclophilin with mutations in the conserved DENFKL domain did not bind to PP2A. Unlike protein phosphatase 2B, PP2A activity in Arabidopsis extracts was not affected by the presence of the cyclophilin-binding molecule cyclosporin. The ROC7 transcript was expressed to high levels in all tissues tested. Expression of an ROC7 antisense transcript gave rise to increased root growth. These results indicate that cyclophilin may have a role in regulating PP2A activity, by a mechanism that differs from that employed for cyclophilin regulation of PP2B.

  1. Transcription Factor Arabidopsis Activating Factor1 Integrates Carbon Starvation Responses with Trehalose Metabolism1[OPEN

    PubMed Central

    Garapati, Prashanth; Feil, Regina; Lunn, John Edward; Van Dijck, Patrick; Balazadeh, Salma; Mueller-Roeber, Bernd

    2015-01-01

    Plants respond to low carbon supply by massive reprogramming of the transcriptome and metabolome. We show here that the carbon starvation-induced NAC (for NO APICAL MERISTEM/ARABIDOPSIS TRANSCRIPTION ACTIVATION FACTOR/CUP-SHAPED COTYLEDON) transcription factor Arabidopsis (Arabidopsis thaliana) Transcription Activation Factor1 (ATAF1) plays an important role in this physiological process. We identified TREHALASE1, the only trehalase-encoding gene in Arabidopsis, as a direct downstream target of ATAF1. Overexpression of ATAF1 activates TREHALASE1 expression and leads to reduced trehalose-6-phosphate levels and a sugar starvation metabolome. In accordance with changes in expression of starch biosynthesis- and breakdown-related genes, starch levels are generally reduced in ATAF1 overexpressors but elevated in ataf1 knockout plants. At the global transcriptome level, genes affected by ATAF1 are broadly associated with energy and carbon starvation responses. Furthermore, transcriptional responses triggered by ATAF1 largely overlap with expression patterns observed in plants starved for carbon or energy supply. Collectively, our data highlight the existence of a positively acting feedforward loop between ATAF1 expression, which is induced by carbon starvation, and the depletion of cellular carbon/energy pools that is triggered by the transcriptional regulation of downstream gene regulatory networks by ATAF1. PMID:26149570

  2. Identification of quantitative trait loci controlling fibre length and lignin content in Arabidopsis thaliana stems

    PubMed Central

    Berleth, Thomas

    2013-01-01

    Fibre properties and the biochemical composition of cell walls are important traits in many applications. For example, the lengths of fibres define the strength and quality of paper, and lignin content is a critical parameter for the use of biomass in biofuel production. Identifying genes controlling these traits is comparatively difficult in woody species, because of long generation times and limited amenability to high-resolution genetic mapping. To address this problem, this study mapped quantitative trait loci (QTLs) defining fibre length and lignin content in the Arabidopsis recombinant inbred line population Col-4×Ler-0. Adapting high-throughput phenotyping techniques for both traits for measurements in Arabidopsis inflorescence stems identified significant QTLs for fibre length on chromosomes 2 and 5, as well as one significant QTL affecting lignin content on chromosome 2. For fibre length, total variation within the population was 208% higher than between parental lines and the identified QTLs explained 50.58% of the observed variation. For lignin content, the values were 261 and 26.51%, respectively. Bioinformatics analysis of the associated intervals identified a number of candidate genes for fibre length and lignin content. This study demonstrates that molecular mapping of QTLs pertaining to wood and fibre properties is possible in Arabidopsis, which substantially broadens the use of Arabidopsis as a model species for the functional characterization of plant genes. PMID:23136168

  3. Biochemical and Structural Properties of Cyanases from Arabidopsis thaliana and Oryza sativa

    PubMed Central

    Qian, Dan; Jiang, Lin; Lu, Lu; Wei, Chunhong; Li, Yi

    2011-01-01

    Cyanate is toxic to all organisms. Cyanase converts cyanate to CO2 and NH3 in a bicarbonate-dependent reaction. The biophysical functions and biochemical characteristics of plant cyanases are poorly studied, although it has been investigated in a variety of proteobacteria, cyanobacteria and fungi. In this study, we characterised plant cyanases from Arabidopsis thaliana and Oryza sativa (AtCYN and OsCYN). Prokaryotic-expressed AtCYN and OsCYN both showed cyanase activity in vitro. Temperature had a similar influence on the activity of both cyanases, but pH had a differential impact on AtCYN and OsCYN activity. Homology modelling provided models of monomers of AtCYN and OsCYN, and a coimmunoprecipitation assay and gel filtration indicated that AtCYN and OsCYN formed homodecamers. The analysis of single-residue mutants of AtCYN indicated that the conserved catalytic residues also contributed to the stability of the homodecamer. KCNO treatment inhibited Arabidopsis germination and early seedling growth. Plants containing AtCYN or OsCYN exhibited resistance to KCNO stress, which demonstrated that one role of cyanases in plants is detoxification. Transcription level of AtCYN was higher in the flower than in other organs of Arabidopsis. AtCYN transcription was not significantly affected by KCNO treatment in Arabidopsis, but was induced by salt stress. This research broadens our knowledge on plant detoxification of cyanate via cyanase. PMID:21494323

  4. Arabidopsis MYC2 Interacts with DELLA Proteins in Regulating Sesquiterpene Synthase Gene Expression[W][OA

    PubMed Central

    Hong, Gao-Jie; Xue, Xue-Yi; Mao, Ying-Bo; Wang, Ling-Jian; Chen, Xiao-Ya

    2012-01-01

    Arabidopsis thaliana flowers emit volatile terpenes, which may function in plant–insect interactions. Here, we report that Arabidopsis MYC2, a basic helix-loop-helix transcription factor, directly binds to promoters of the sesquiterpene synthase genes TPS21 and TPS11 and activates their expression. Expression of TPS21 and TPS11 can be induced by the phytohormones gibberellin (GA) and jasmonate (JA), and both inductions require MYC2. The induction of TPS21 and TPS11 results in increased emission of sesquiterpene, especially (E)-β-caryophyllene. DELLAs, the GA signaling repressors, negatively affect sesquiterpene biosynthesis, as the sesquiterpene synthase genes were repressed in plants overaccumulating REPRESSOR OF GA1-3 (RGA), one of the Arabidopsis DELLAs, and upregulated in a penta DELLA-deficient mutant. Yeast two-hybrid and coimmunoprecipitation assays demonstrated that DELLAs, represented by RGA, directly interact with MYC2. In yeast cells, the N terminus of MYC2 was responsible for binding to RGA. MYC2 has been proposed as a major mediator of JA signaling and crosstalk with abscisic acid, ethylene, and light signaling pathways. Our results demonstrate that MYC2 is also connected to GA signaling in regulating a subset of genes. In Arabidopsis inflorescences, it integrates both GA and JA signals into transcriptional regulation of sesquiterpene synthase genes and promotes sesquiterpene production. PMID:22669881

  5. Comparative analyses of distributions and functions of Z-DNA in Arabidopsis and rice.

    PubMed

    Zhou, Chan; Zhou, Fengfeng; Xu, Ying

    2009-04-01

    Left-handed Z-DNA is an energetically unfavorable DNA structure that could form mostly under certain physiological conditions and was known to be involved in a number of cellular activities such as transcription regulation. We have compared the distributions and functions of Z-DNA in the genomes of Arabidopsis and rice, and observed that Z-DNA occurs in rice at least 9 times more often than in Arabidopsis; similar observations hold for other monocots and dicots. In addition, Z-DNA is significantly enriched in the coding regions of Arabidopsis, and in the high-GC-content regions of rice. Based on our analyses, we speculate that Z-DNA may play a role in regulating the expression of transcription factors, inhibitors, translation repressors, succinate dehydrogenases and glutathione-disulfide reductases in Arabidopsis, and it may affect the expression of vesicle and nucleosome genes and genes involved in alcohol transporter activity, stem cell maintenance, meristem development and reproductive structure development in rice. PMID:19103278

  6. Transcription Factor Arabidopsis Activating Factor1 Integrates Carbon Starvation Responses with Trehalose Metabolism.

    PubMed

    Garapati, Prashanth; Feil, Regina; Lunn, John Edward; Van Dijck, Patrick; Balazadeh, Salma; Mueller-Roeber, Bernd

    2015-09-01

    Plants respond to low carbon supply by massive reprogramming of the transcriptome and metabolome. We show here that the carbon starvation-induced NAC (for NO APICAL MERISTEM/ARABIDOPSIS TRANSCRIPTION ACTIVATION FACTOR/CUP-SHAPED COTYLEDON) transcription factor Arabidopsis (Arabidopsis thaliana) Transcription Activation Factor1 (ATAF1) plays an important role in this physiological process. We identified TREHALASE1, the only trehalase-encoding gene in Arabidopsis, as a direct downstream target of ATAF1. Overexpression of ATAF1 activates TREHALASE1 expression and leads to reduced trehalose-6-phosphate levels and a sugar starvation metabolome. In accordance with changes in expression of starch biosynthesis- and breakdown-related genes, starch levels are generally reduced in ATAF1 overexpressors but elevated in ataf1 knockout plants. At the global transcriptome level, genes affected by ATAF1 are broadly associated with energy and carbon starvation responses. Furthermore, transcriptional responses triggered by ATAF1 largely overlap with expression patterns observed in plants starved for carbon or energy supply. Collectively, our data highlight the existence of a positively acting feedforward loop between ATAF1 expression, which is induced by carbon starvation, and the depletion of cellular carbon/energy pools that is triggered by the transcriptional regulation of downstream gene regulatory networks by ATAF1. PMID:26149570

  7. Phenotypic and chemotypic studies using Arabidopsis and yeast reveal that GHB converts to SSA and induce toxicity.

    PubMed

    Mekonnen, Dereje Worku; Ludewig, Frank

    2016-07-01

    γ-Hydroxybutyric acid (GHB) is a naturally occurring compound. It is detected in organisms such as yeasts, plants and mammals. GHB is produced from the reduction of succinic semialdehyde (SSA) by the activity of GHB dehydrogenase. Arabidopsis genome contains two GHB dehydrogenase encoding genes. The accumulation of GHB in ssadh mutants led to the speculation that GHB is the cause of aberrant phenotypes. Conversely, the accumulation of GHB in Arabidopsis plants subjected to abiotic stresses was described as a way of avoiding SSA induced damage. To resolve these contrasting views on GHB, we examined the effect of exogenous GHB and SSA on the growth of yeast and Arabidopsis plants. GHB concentrations up to 1.5 mM didn't affect shoots of Arabidopsis plants; however, root growth was inhibited. In contrast, 0.3 mM SSA has severely affected the growth of plants. Treatment of yeast wild-type strain with 10 mM SSA and 10 mM GHB didn't affect the growth. However, the growth of yeast uga2 mutant was greatly inhibited by the same concentration of SSA, but not GHB. Metabolic analysis and enzyme activity assay on native gel showed that Arabidopsis, but not yeast, possesses a GHB dehydrogenase activity that converts GHB back to SSA. The enzymatic assay has also indicated the existence of an additional GHB dehydrogenase encoding gene(s) in Arabidopsis genome. Taken together, we conclude that GHB is less toxic than SSA. Its accumulation in ssadh mutants and during abiotic stresses is a response to avoid the SSA induced damage. PMID:27037708

  8. The protein kinase TOUSLED facilitates RNAi in Arabidopsis

    PubMed Central

    Uddin, Mohammad Nazim; Dunoyer, Patrice; Schott, Gregory; Akhter, Salina; Shi, Chunlin; Lucas, William J.; Voinnet, Olivier; Kim, Jae-Yean

    2014-01-01

    RNA silencing is an evolutionarily conserved mechanism triggered by double-stranded RNA that is processed into 21- to 24-nt small interfering (si)RNA or micro (mi)RNA by RNaseIII-like enzymes called Dicers. Gene regulations by RNA silencing have fundamental implications in a large number of biological processes that include antiviral defense, maintenance of genome integrity and the orchestration of cell fates. Although most generic or core components of the various plant small RNA pathways have been likely identified over the past 15 years, factors involved in RNAi regulation through post-translational modifications are just starting to emerge, mostly through forward genetic studies. A genetic screen designed to identify factors required for RNAi in Arabidopsis identified the serine/threonine protein kinase, TOUSLED (TSL). Mutations in TSL affect exogenous and virus-derived siRNA activity in a manner dependent upon its kinase activity. By contrast, despite their pleiotropic developmental phenotype, tsl mutants show no defect in biogenesis or activity of miRNA or endogenous trans-acting siRNA. These data suggest a possible role for TSL phosphorylation in the specific regulation of exogenous and antiviral RNA silencing in Arabidopsis and identify TSL as an intrinsic regulator of RNA interference. PMID:24920830

  9. Nucleosome structure incorporated histone acetylation site prediction in arabidopsis thaliana

    PubMed Central

    2010-01-01

    Abstract Background Acetylation is a crucial post-translational modification for histones, and plays a key role in gene expression regulation. Due to limited data and lack of a clear acetylation consensus sequence, a few researches have focused on prediction of lysine acetylation sites. Several systematic prediction studies have been conducted for human and yeast, but less for Arabidopsis thaliana. Results Concerning the insufficient observation on acetylation site, we analyzed contributions of the peptide-alignment-based distance definition and 3D structure factors in acetylation prediction. We found that traditional structure contributes little to acetylation site prediction. Identified acetylation sites of histones in Arabidopsis thaliana are conserved and cross predictable with that of human by peptide based methods. However, the predicted specificity is overestimated, because of the existence of non-observed acetylable site. Here, by performing a complete exploration on the factors that affect the acetylability of lysines in histones, we focused on the relative position of lysine at nucleosome level, and defined a new structure feature to promote the performance in predicting the acetylability of all the histone lysines in A. thaliana. Conclusion We found a new spacial correlated acetylation factor, and defined a ε-N spacial location based feature, which contains five core spacial ellipsoid wired areas. By incorporating the new feature, the performance of predicting the acetylability of all the histone lysines in A. Thaliana was promoted, in which the previous mispredicted acetylable lysines were corrected by comparing to the peptide-based prediction. PMID:21047388

  10. Piriformospora indica Stimulates Root Metabolism of Arabidopsis thaliana

    PubMed Central

    Strehmel, Nadine; Mönchgesang, Susann; Herklotz, Siska; Krüger, Sylvia; Ziegler, Jörg; Scheel, Dierk

    2016-01-01

    Piriformospora indica is a root-colonizing fungus, which interacts with a variety of plants including Arabidopsis thaliana. This interaction has been considered as mutualistic leading to growth promotion of the host. So far, only indolic glucosinolates and phytohormones have been identified as key players. In a comprehensive non-targeted metabolite profiling study, we analyzed Arabidopsis thaliana’s roots, root exudates, and leaves of inoculated and non-inoculated plants by ultra performance liquid chromatography/electrospray ionization quadrupole-time-of-flight mass spectrometry (UPLC/(ESI)-QTOFMS) and gas chromatography/electron ionization quadrupole mass spectrometry (GC/EI-QMS), and identified further biomarkers. Among them, the concentration of nucleosides, dipeptides, oligolignols, and glucosinolate degradation products was affected in the exudates. In the root profiles, nearly all metabolite levels increased upon co-cultivation, like carbohydrates, organic acids, amino acids, glucosinolates, oligolignols, and flavonoids. In the leaf profiles, we detected by far less significant changes. We only observed an increased concentration of organic acids, carbohydrates, ascorbate, glucosinolates and hydroxycinnamic acids, and a decreased concentration of nitrogen-rich amino acids in inoculated plants. These findings contribute to the understanding of symbiotic interactions between plant roots and fungi of the order of Sebacinales and are a valid source for follow-up mechanistic studies, because these symbioses are particular and clearly different from interactions of roots with mycorrhizal fungi or dark septate endophytes PMID:27399695

  11. Piriformospora indica Stimulates Root Metabolism of Arabidopsis thaliana.

    PubMed

    Strehmel, Nadine; Mönchgesang, Susann; Herklotz, Siska; Krüger, Sylvia; Ziegler, Jörg; Scheel, Dierk

    2016-01-01

    Piriformospora indica is a root-colonizing fungus, which interacts with a variety of plants including Arabidopsis thaliana. This interaction has been considered as mutualistic leading to growth promotion of the host. So far, only indolic glucosinolates and phytohormones have been identified as key players. In a comprehensive non-targeted metabolite profiling study, we analyzed Arabidopsis thaliana's roots, root exudates, and leaves of inoculated and non-inoculated plants by ultra performance liquid chromatography/electrospray ionization quadrupole-time-of-flight mass spectrometry (UPLC/(ESI)-QTOFMS) and gas chromatography/electron ionization quadrupole mass spectrometry (GC/EI-QMS), and identified further biomarkers. Among them, the concentration of nucleosides, dipeptides, oligolignols, and glucosinolate degradation products was affected in the exudates. In the root profiles, nearly all metabolite levels increased upon co-cultivation, like carbohydrates, organic acids, amino acids, glucosinolates, oligolignols, and flavonoids. In the leaf profiles, we detected by far less significant changes. We only observed an increased concentration of organic acids, carbohydrates, ascorbate, glucosinolates and hydroxycinnamic acids, and a decreased concentration of nitrogen-rich amino acids in inoculated plants. These findings contribute to the understanding of symbiotic interactions between plant roots and fungi of the order of Sebacinales and are a valid source for follow-up mechanistic studies, because these symbioses are particular and clearly different from interactions of roots with mycorrhizal fungi or dark septate endophytes. PMID:27399695

  12. Posttranslational modifications of FERREDOXIN-NADP+ OXIDOREDUCTASE in Arabidopsis chloroplasts.

    PubMed

    Lehtimäki, Nina; Koskela, Minna M; Dahlström, Käthe M; Pakula, Eveliina; Lintala, Minna; Scholz, Martin; Hippler, Michael; Hanke, Guy T; Rokka, Anne; Battchikova, Natalia; Salminen, Tiina A; Mulo, Paula

    2014-12-01

    Rapid responses of chloroplast metabolism and adjustments to photosynthetic machinery are of utmost importance for plants' survival in a fluctuating environment. These changes may be achieved through posttranslational modifications of proteins, which are known to affect the activity, interactions, and localization of proteins. Recent studies have accumulated evidence about the crucial role of a multitude of modifications, including acetylation, methylation, and glycosylation, in the regulation of chloroplast proteins. Both of the Arabidopsis (Arabidopsis thaliana) leaf-type FERREDOXIN-NADP(+) OXIDOREDUCTASE (FNR) isoforms, the key enzymes linking the light reactions of photosynthesis to carbon assimilation, exist as two distinct forms with different isoelectric points. We show that both AtFNR isoforms contain multiple alternative amino termini and undergo light-responsive addition of an acetyl group to the α-amino group of the amino-terminal amino acid of proteins, which causes the change in isoelectric point. Both isoforms were also found to contain acetylation of a conserved lysine residue near the active site, while no evidence for in vivo phosphorylation or glycosylation was detected. The dynamic, multilayer regulation of AtFNR exemplifies the complex regulatory network systems controlling chloroplast proteins by a range of posttranslational modifications, which continues to emerge as a novel area within photosynthesis research. PMID:25301888

  13. ABORTED GAMETOPHYTE 1 is required for gametogenesis in Arabidopsis.

    PubMed

    Cui, Hong-Hui; Liao, Hong-Ze; Tang, Yu; Du, Xin-Yu; Chen, Li-Qun; Ye, De; Zhang, Xue-Qin

    2015-12-01

    In flowering plants, the male and female gametogenesis is a crucial step of sexual reproduction. Although many genes have been identified as being involved in the gametogenesis process, the genetic mechanisms underlying gametogenesis remains poorly understood. We reported here characterization of the gene, ABORTED GAMETOPHYTE 1 (AOG1) that is newly identified as essential for gametogenesis in Arabidopsis thaliana. AOG1 is expressed predominantly in reproductive tissues including the developing pollen grains and ovules. The AOG1 protein shares no significant amino acid sequence similarity with other documented proteins and is located mainly in nuclei of the cells. Mutation in AOG1 caused degeneration of pollen at the uninucleate microspore stage and severe defect in embryo sacs, leading to a significant reduction in male and female fertility. Furthermore, the molecular analyses showed that the aog1 mutant significantly affected the expression of several genes, which are required for gametogenesis. Our results suggest that AOG1 plays important roles in gametogenesis at the stage prior to pollen mitosis I (PMI) in Arabidopsis, possibly through collaboration with other genes. PMID:25693728

  14. Applicability of Phytoextraction with Arabidopsis halleri ssp. gemmifera to Remediate Cd-contaminated Andisols

    NASA Astrophysics Data System (ADS)

    Kameyama, Koji; Tani, Shigeru; Sugawara, Reiko; Ishikawa, Yuichi

    The objective of this study was to investigate the applicability of phytoextraction with a Cd-hyperaccumulator plant (Arabidopsis halleri ssp. gemmifera) to remediate Cd-contaminated Andisols. Cd absorption potentials of this plant for Andisols were examined in pot experiments. Sequentially, phytoextraction durations for remediation of Cd-contaminated Andisols were calculated from the experimental data. The results were as follows: (1) Cd concentrations in the plant shoots ranged from 170-750 mgṡkg-1. (2) Cd absorption of the plant for Andisols with ALC (Autoclaved Lightweight aerated Concrete) was less than for Andisols without ALC. However, the plants absorbed the same amount of soil Cd extracted by 0.01 M HCl with or without ALC. (3) Calculations suggest that the applicability of phytoextraction with this plant is high for slightly contaminated Andisols. Therefore, phytoextraction with Arabidopsis halleri ssp. gemmifera may be a viable option for the remediation of Cd-contaminated Andisols.

  15. Expression of an Arabidopsis sodium/proton antiporter gene (AtNHX1)in peanut to improve salt tolerance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Salinity is a major environmental stress that affects agricultural productivity worldwide. One approach to improving salt tolerance in crops is through high expression of the Arabidopsis gene AtNHX1, which encodes a vacuolar sodium/proton antiporter that sequesters excess sodium ion into the large i...

  16. Comparative pathobiology of Heterobasidion annosum during challenge on Pinus sylvestris and Arabidopsis roots: an analysis of defensin gene expression in two pathosystems.

    PubMed

    Jaber, Emad; Xiao, Chaowen; Asiegbu, Fred O

    2014-03-01

    Heterobasidion annosum is widely known as a major root and butt rot pathogen of conifer trees, but little information is available on its interaction with the roots of herbaceous angiosperm plants. We investigated the infection biology of H. annosum during challenge with the angiosperm model Arabidopsis and monitored the host response after exposure to different hormone elicitors, chemicals (chitin, glucan and chitosan) and fungal species that represent diverse basidiomycete life strategies [e.g., pathogen (H. annosum), saprotroph (Stereum sanguinolentum) and mutualist (Lactarius rufus)]. The results revealed that the tree pathogen (H. annosum) and the saprotroph (S. sanguinolentum) could infect the Col-8 (Columbia) ecotype of Arabidopsis in laboratory inoculation experiments. Germinated H. annosum spores had appressorium-like penetration structures attached to the surface of the Arabidopsis roots. Subsequent invasive fungal growth led to the disintegration of the vascular region of the root tissues. Progression of root rot symptoms in Arabidopsis was similar to the infection development that was previously documented in Scots pine seedlings. Scots pine PsDef1 and Arabidopsis DEFLs (AT5G44973.1) and PDF1.2 were induced at the initial stage of the infection. However, differences in the expression patterns of the defensin gene homologs from the two plant groups were observed under various conditions, suggesting functional differences in their regulation. The potential use of the H. annosum-Arabidopsis pathosystem as a model for studying forest tree diseases is discussed. PMID:24366684

  17. Genome size variation and evolution in allotetraploid Arabidopsis kamchatica and its parents, Arabidopsis lyrata and Arabidopsis halleri

    PubMed Central

    Wolf, Diana E.; Steets, Janette A.; Houliston, Gary J.; Takebayashi, Naoki

    2014-01-01

    Polyploidization and subsequent changes in genome size are fundamental processes in evolution and diversification. Little is currently known about the extent of genome size variation within taxa and the evolutionary forces acting on this variation. Arabidopsis kamchatica has been reported to contain both diploid and tetraploid individuals. The aim of this study was to determine the genome size of A. kamchatica, whether there is variation in ploidy and/or genome size in A. kamchatica and to study how genome size has evolved. We used propidium iodide flow cytometry to measure 2C DNA content of 73 plants from 25 geographically diverse populations of the putative allotetraploid A. kamchatica and its parents, Arabidopsis lyrata and Arabidopsis halleri. All A. kamchatica plants appear to be tetraploids. The mean 2C DNA content of A. kamchatica was 1.034 pg (1011 Mbp), which is slightly smaller than the sum of its diploid parents (A. lyrata: 0.502 pg; A. halleri: 0.571 pg). Arabidopsis kamchatica appears to have lost ∼37.594 Mbp (3.6 %) of DNA from its 2C genome. Tetraploid A. lyrata from Germany and Austria appears to have lost ∼70.366 Mbp (7.2 %) of DNA from the 2C genome, possibly due to hybridization with A. arenosa, which has a smaller genome than A. lyrata. We did find genome size differences among A. kamchatica populations, which varied up to 7 %. Arabidopsis kamchatica ssp. kawasakiana from Japan appears to have a slightly larger genome than A. kamchatica ssp. kamchatica from North America, perhaps due to multiple allopolyploid origins or hybridization with A. halleri. However, the among-population coefficient of variation in 2C DNA content is lower in A. kamchatica than in other Arabidopsis taxa. Due to its close relationship to A. thaliana, A. kamchatica has the potential to be very useful in the study of polyploidy and genome evolution. PMID:24887004

  18. An Arabidopsis flavonoid transporter is required for anther dehiscence and pollen development

    PubMed Central

    Thompson, Elinor P.; Wilkins, Christopher; Demidchik, Vadim; Davies, Julia M.; Glover, Beverley J.

    2010-01-01

    FLOWER FLAVONOID TRANSPORTER (FFT) encodes a multidrug and toxin efflux family transporter in Arabidopsis thaliana. FFT (AtDTX35) is highly transcribed in floral tissues, the transcript being localized to epidermal guard cells, including those of the anthers, stigma, siliques and nectaries. Mutant analysis demonstrates that the absence of FFT transcript affects flavonoid levels in the plant and that the altered flavonoid metabolism has wide-ranging consequences. Root growth, seed development and germination, and pollen development, release and viability are all affected. Spectrometry of mutant versus wild-type flowers shows altered levels of a glycosylated flavonol whereas anthocyanin seems unlikely to be the substrate as previously speculated. Thus, as well as adding FFT to the incompletely described flavonoid transport network, it is found that correct reproductive development in Arabidopsis is perturbed when this particular transporter is missing. PMID:19995827

  19. Genetic Analysis of Gravity Signal Transduction in Arabidopsis thaliana Seedlings

    NASA Astrophysics Data System (ADS)

    Boonsirichai, K.; Harrison, B.; Stanga, J.; Young, L.-S.; Neal, C.; Sabat, G.; Murthy, N.; Harms, A.; Sedbrook, J.; Masson, P.

    The primary roots of Arabidopsis thaliana seedlings respond to gravity stimulation by developing a tip curvature that results from differential cellular elongation on opposite flanks of the elongation zone. This curvature appears modulated by a lateral gradient of auxin that originates in the gravity-perceiving cells (statocytes) of the root cap through an apparent lateral repositioning of a component the auxin efflux carrier complex within these cells (Friml et al, 2002, Nature 415: 806-809). Unfortunately, little is known about the molecular mechanisms that govern early phases of gravity perception and signal transduction within the root-cap statocytes. We have used a molecular genetic approach to uncover some of these mechanisms. Mutations in the Arabidopsis ARG1 and ARL2 genes, which encode J-domain proteins, resulted in specific alterations in root and hypocotyl gravitropism, without pleiotropic phenotypes. Interestingly, ARG1 and ARL2 appear to function in the same genetic pathway. A combination of molecular genetic, biochemical and cell-biological approaches were used to demonstrate that ARG1 functions in early phases of gravity signal transduction within the root and hypocotyl statocytes, and is needed for efficient lateral auxin transport within the cap. The ARG1 protein is associated with components of the secretory and/or endosomal pathways, suggesting its role in the recycling of components of the auxin efflux carrier complex between plasma membrane and endosome (Boonsirichai et al, 2003, Plant Cell 15:2612-2625). Genetic modifiers of arg1-2 were isolated and shown to enhance the gravitropic defect of arg1-2, while resulting in little or no gravitropic defects in a wild type ARG1 background. A slight tendency for arg1-2;mar1-1 and arg1-2;mar2-1 double-mutant organs to display an opposite gravitropic response compared to wild type suggests that all three genes contribute to the interpretation of the gravity-vector information by seedling organs. The

  20. Early flower development in Arabidopsis.

    PubMed Central

    Smyth, D R; Bowman, J L; Meyerowitz, E M

    1990-01-01

    The early development of the flower of Arabidopsis thaliana is described from initiation until the opening of the bud. The morphogenesis, growth rate, and surface structure of floral organs were recorded in detail using scanning electron microscopy. Flower development has been divided into 12 stages using a series of landmark events. Stage 1 begins with the initiation of a floral buttress on the flank of the apical meristem. Stage 2 commences when the flower primordium becomes separate from the meristem. Sepal primordia then arise (stage 3) and grow to overlie the primordium (stage 4). Petal and stamen primordia appear next (stage 5) and are soon enclosed by the sepals (stage 6). During stage 6, petal primordia grow slowly, whereas stamen primordia enlarge more rapidly. Stage 7 begins when the medial stamens become stalked. These soon develop locules (stage 8). A long stage 9 then commences with the petal primordia becoming stalked. During this stage all organs lengthen rapidly. This includes the gynoecium, which commences growth as an open-ended tube during stage 6. When the petals reach the length of the lateral stamens, stage 10 begins. Stigmatic papillae appear soon after (stage 11), and the petals rapidly reach the height of the medial stamens (stage 12). This final stage ends when the 1-millimeter-long bud opens. Under our growing conditions 1.9 buds were initiated per day on average, and they took 13.25 days to progress through the 12 stages from initiation until opening. PMID:2152125

  1. 1,2-Dibromo-3-chloropropane (DBCP)

    Integrated Risk Information System (IRIS)

    1,2 - Dibromo - 3 - chloropropane ( DBCP ) ; CASRN 96 - 12 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessm

  2. 1,1,2,2-Tetrachloroethane

    Integrated Risk Information System (IRIS)

    1,1,2,2 - Tetrachloroethane ; CASRN 79 - 34 - 5 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncar

  3. 1,2,4,5-Tetrachlorobenzene

    Integrated Risk Information System (IRIS)

    1,2,4,5 - Tetrachlorobenzene ; CASRN 95 - 94 - 3 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Nonca

  4. 1,1,1,2-Tetrachloroethane

    Integrated Risk Information System (IRIS)

    1,1,1,2 - Tetrachloroethane ; CASRN 630 - 20 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Nonca

  5. 1,1,1,2-Tetrafluoroethane

    Integrated Risk Information System (IRIS)

    1,1,1,2 - Tetrafluoroethane ; CASRN 811 - 97 - 2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Nonca

  6. 1,2,3-triazolium ionic liquids

    SciTech Connect

    Luebke, David; Nulwala, Hunaid; Tang, Chau

    2014-12-09

    The present invention relates to compositions of matter that are ionic liquids, the compositions comprising substituted 1,2,3-triazolium cations combined with any anion. Compositions of the invention should be useful in the separation of gases and, perhaps, as catalysts for many reactions.

  7. Arabidopsis INCURVATA2 Regulates Salicylic Acid and Abscisic Acid Signaling, and Oxidative Stress Responses.

    PubMed

    Micol-Ponce, Rosa; Sánchez-García, Ana Belén; Xu, Qian; Barrero, José María; Micol, José Luis; Ponce, María Rosa

    2015-11-01

    Epigenetic regulatory states can persist through mitosis and meiosis, but the connection between chromatin structure and DNA replication remains unclear. Arabidopsis INCURVATA2 (ICU2) encodes the catalytic subunit of DNA polymerase α, and null alleles of ICU2 have an embryo-lethal phenotype. Analysis of icu2-1, a hypomorphic allele of ICU2, demonstrated that ICU2 functions in chromatin-mediated cellular memory; icu2-1 strongly impairs ICU2 function in the maintenance of repressive epigenetic marks but does not seem to affect ICU2 polymerase activity. To better understand the global function of ICU2 in epigenetic regulation, here we performed a microarray analysis of icu2-1 mutant plants. We found that the genes up-regulated in the icu2-1 mutant included genes encoding transcription factors and targets of the Polycomb Repressive Complexes. The down-regulated genes included many known players in salicylic acid (SA) biosynthesis and accumulation, ABA signaling and ABA-mediated responses. In addition, we found that icu2-1 plants had reduced SA levels in normal conditions; infection by Fusarium oxysporum induced SA accumulation in the En-2 wild type but not in the icu2-1 mutant. The icu2-1 plants were also hypersensitive to salt stress and exogenous ABA in seedling establishment, post-germination growth and stomatal closure, and accumulated more ABA than the wild type in response to salt stress. The icu2-1 mutant also showed high tolerance to the oxidative stress produced by 3-amino-1,2,4-triazole (3-AT). Our results uncover a role for ICU2 in the regulation of genes involved in ABA signaling as well as in SA biosynthesis and accumulation. PMID:26423959

  8. Allocation of Heme Is Differentially Regulated by Ferrochelatase Isoforms in Arabidopsis Cells

    PubMed Central

    Espinas, Nino A.; Kobayashi, Koichi; Sato, Yasushi; Mochizuki, Nobuyoshi; Takahashi, Kaori; Tanaka, Ryouichi; Masuda, Tatsuru

    2016-01-01

    Heme is involved in various biological processes as a cofactor of hemoproteins located in various organelles. In plant cells, heme is synthesized by two isoforms of plastid-localized ferrochelatase, FC1 and FC2. In this study, by characterizing Arabidopsis T-DNA insertional mutants, we showed that the allocation of heme is differentially regulated by ferrochelatase isoforms in plant cells. Analyses of weak (fc1-1) and null (fc1-2) mutants suggest that FC1-producing heme is required for initial growth of seedling development. In contrast, weak (fc2-1) and null (fc2-2) mutants of FC2 showed pale green leaves and retarded growth, indicating that FC2-producing heme is necessary for chloroplast development. During the initial growth stage, FC2 deficiency caused reduction of plastid cytochromes. In addition, although FC2 deficiency marginally affected the assembly of photosynthetic reaction center complexes, it caused relatively larger but insufficient light-harvesting antenna to reaction centers, resulting in lower efficiency of photosynthesis. In the later vegetative growth, however, fc2-2 recovered photosynthetic growth, showing that FC1-producing heme may complement the FC2 deficiency. On the other hand, reduced level of cytochromes in microsomal fraction was discovered in fc1-1, suggesting that FC1-producing heme is mainly allocated to extraplastidic organelles. Furthermore, the expression of FC1 is induced by the treatment of an elicitor flg22 while that of FC2 was reduced, and fc1-1 abolished the flg22-dependent induction of FC1 expression and peroxidase activity. Consequently, our results clarified that FC2 produces heme for the photosynthetic machinery in the chloroplast, while FC1 is the housekeeping enzyme providing heme cofactor to the entire cell. In addition, FC1 can partly complement FC2 deficiency and is also involved in defense against stressful conditions.

  9. DELLA proteins modulate Arabidopsis defences induced in response to caterpillar herbivory

    PubMed Central

    Bede, Jacqueline C.

    2014-01-01

    Upon insect herbivory, many plant species change the direction of metabolic flux from growth into defence. Two key pathways modulating these processes are the gibberellin (GA)/DELLA pathway and the jasmonate pathway. In this study, the effect of caterpillar herbivory on plant-induced responses was compared between wild-type Arabidopsis thaliana (L.) Heynh. and quad-della mutants that have constitutively elevated GA responses. The labial saliva (LS) of caterpillars of the beet armyworm, Spodoptera exigua, is known to influence induced plant defence responses. To determine the role of this herbivore cue in determining metabolic shifts, plants were subject to herbivory by caterpillars with intact or impaired LS secretions. In both wild-type and quad-della plants, a jasmonate burst is an early response to caterpillar herbivory. Negative growth regulator DELLA proteins are required for the LS-mediated suppression of hormone levels. Jasmonate-dependent marker genes are induced in response to herbivory independently of LS, with the exception of AtPDF1.2 that showed LS-dependent expression in the quad-della mutant. Early expression of the salicylic acid (SA)-marker gene, AtPR1, was not affected by herbivory which also reflected SA hormone levels; however, this gene showed LS-dependent expression in the quad-della mutant. DELLA proteins may positively regulate glucosinolate levels and suppress laccase-like multicopper oxidase activity in response to herbivory. The present results show a link between DELLA proteins and early, induced plant defences in response to insect herbivory; in particular, these proteins are necessary for caterpillar LS-associated attenuation of defence hormones. PMID:24399173

  10. Gibberellins control fruit patterning in Arabidopsis thaliana

    PubMed Central

    Arnaud, Nicolas; Girin, Thomas; Sorefan, Karim; Fuentes, Sara; Wood, Thomas A.; Lawrenson, Tom; Sablowski, Robert; Østergaard, Lars

    2010-01-01

    The Arabidopsis basic helix–loop–helix (bHLH) proteins INDEHISCENT (IND) and ALCATRAZ (ALC) specify tissues required for fruit opening that have major roles in seed dispersal and plant domestication. Here, we show that synthesis of the phytohormone gibberellin is a direct and necessary target of IND, and that ALC interacts directly with DELLA repressors, which antagonize ALC function but are destabilized by gibberellin. Thus, the gibberellin/DELLA pathway has a key role in patterning the Arabidopsis fruit, and the interaction between DELLA and bHLH proteins, previously shown to connect gibberellin and light responses, is a versatile regulatory module also used in tissue patterning. PMID:20889713

  11. Gibberellins control fruit patterning in Arabidopsis thaliana.

    PubMed

    Arnaud, Nicolas; Girin, Thomas; Sorefan, Karim; Fuentes, Sara; Wood, Thomas A; Lawrenson, Tom; Sablowski, Robert; Østergaard, Lars

    2010-10-01

    The Arabidopsis basic helix-loop-helix (bHLH) proteins INDEHISCENT (IND) and ALCATRAZ (ALC) specify tissues required for fruit opening that have major roles in seed dispersal and plant domestication. Here, we show that synthesis of the phytohormone gibberellin is a direct and necessary target of IND, and that ALC interacts directly with DELLA repressors, which antagonize ALC function but are destabilized by gibberellin. Thus, the gibberellin/DELLA pathway has a key role in patterning the Arabidopsis fruit, and the interaction between DELLA and bHLH proteins, previously shown to connect gibberellin and light responses, is a versatile regulatory module also used in tissue patterning. PMID:20889713

  12. The QQS orphan gene of Arabidopsis modulates carbon and nitrogen allocation in soybean

    PubMed Central

    Li, Ling; Wurtele, Eve Syrkin

    2015-01-01

    The genome of each species contains as high as 8% of genes that are uniquely present in that species. Little is known about the functional significance of these so-called species specific or orphan genes. The Arabidopsis thaliana gene Qua-Quine Starch (QQS) is species specific. Here, we show that altering QQS expression in Arabidopsis affects carbon partitioning to both starch and protein. We hypothesized QQS may be conserved in a feature other than primary sequence, and as such could function to impact composition in another species. To test the potential of QQS in affecting composition in an ectopic species, we introduced QQS into soybean. Soybean T1 lines expressing QQS have up to 80% decreased leaf starch and up to 60% increased leaf protein; T4 generation seeds from field-grown plants contain up to 13% less oil, while protein is increased by up to 18%. These data broaden the concept of QQS as a modulator of carbon and nitrogen allocation, and demonstrate that this species-specific gene can affect the seed composition of an agronomic species thought to have diverged from Arabidopsis 100 million years ago. PMID:25146936

  13. The QQS orphan gene of Arabidopsis modulates carbon and nitrogen allocation in soybean.

    PubMed

    Li, Ling; Wurtele, Eve Syrkin

    2015-02-01

    The genome of each species contains as high as 8% of genes that are uniquely present in that species. Little is known about the functional significance of these so-called species specific or orphan genes. The Arabidopsis thaliana gene Qua-Quine Starch (QQS) is species specific. Here, we show that altering QQS expression in Arabidopsis affects carbon partitioning to both starch and protein. We hypothesized QQS may be conserved in a feature other than primary sequence, and as such could function to impact composition in another species. To test the potential of QQS in affecting composition in an ectopic species, we introduced QQS into soybean. Soybean T1 lines expressing QQS have up to 80% decreased leaf starch and up to 60% increased leaf protein; T4 generation seeds from field-grown plants contain up to 13% less oil, while protein is increased by up to 18%. These data broaden the concept of QQS as a modulator of carbon and nitrogen allocation, and demonstrate that this species-specific gene can affect the seed composition of an agronomic species thought to have diverged from Arabidopsis 100 million years ago. PMID:25146936

  14. Internal rotation for predicting conformational population of 1,2-difluorethane and 1,2-dichloroethane

    NASA Astrophysics Data System (ADS)

    Venâncio, Mateus F.; Dos Santos, Hélio F.; De Almeida, Wagner B.

    2016-06-01

    The contribution of internal rotation to the thermal correction of Gibbs free energy (ΔG) is estimated using the quantum pendulum model (QPM) to solve the characteristic Schrödinger equation. The procedure is applied to theoretical prediction of conformational population of 1,2-difluorethane (1,2-DFE) and 1,2-dichloroethane (1,2-DCE) molecules. The predicted population for the anti form was 37% and 75%, for 1,2-DFE and 1,2-DCE respectively, in excellent agreement with experimental gas phase data available, 37 ± 5% and 78 ± 5%. These results provide great support to the use of the QPM model to account for the low vibrational frequency modes effect on the calculation of thermodynamic properties.

  15. Natural variations in expression of regulatory and detoxification related genes under limiting phosphate and arsenate stress in Arabidopsis thaliana

    PubMed Central

    Shukla, Tapsi; Kumar, Smita; Khare, Ria; Tripathi, Rudra D.; Trivedi, Prabodh K.

    2015-01-01

    Abiotic stress including nutrient deficiency and heavy metal toxicity severely affects plant growth, development, and productivity. Genetic variations within and in between species are one of the important factors in establishing interactions and responses of plants with the environment. In the recent past, natural variations in Arabidopsis thaliana have been used to understand plant development and response toward different stresses at genetic level. Phosphorus deficiency negatively affects plant growth and metabolism and modulates expression of the genes involved in Pi homeostasis. Arsenate, As(V), a chemical analog of Pi, is taken up by the plants via phosphate transport system. Studies suggest that during Pi deficiency, enhanced As(V) uptake leads to increased toxicity in plants. Here, the natural variations in Arabidopsis have been utilized to study the As(V) stress response under limiting Pi condition. The primary root length was compared to identify differential response of three Arabidopsis accessions (Col-0, Sij-1, and Slavi-1) under limiting Pi and As(V) stress. To study the molecular mechanisms responsible for the differential response, comprehensive expression profiling of the genes involved in uptake, detoxification, and regulatory mechanisms was carried out. Analysis suggests genetic variation-dependent regulatory mechanisms may affect differential response of Arabidopsis natural variants toward As(V) stress under limiting Pi condition. Therefore, it is hypothesized that detailed analysis of the natural variations under multiple stress conditions might help in the better understanding of the biological processes involved in stress tolerance and adaptation. PMID:26557133

  16. Kinetics of 1,2-Dichloroethane and 1,2-Dibromoethane Biodegradation in Anaerobic Enrichment Cultures

    PubMed Central

    Yu, Rong; Peethambaram, Hari S.; Falta, Ronald W.; Verce, Matthew F.; Henderson, James K.; Bagwell, Christopher E.; Brigmon, Robin L.

    2013-01-01

    1,2-Dichloroethane (1,2-DCA) and 1,2-dibromoethane (ethylene dibromide [EDB]) contaminate groundwater at many hazardous waste sites. The objectives of this study were to measure yields, maximum specific growth rates (μ̂), and half-saturation coefficients (KS) in enrichment cultures that use 1,2-DCA and EDB as terminal electron acceptors and lactate as the electron donor and to evaluate if the presence of EDB has an effect on the kinetics of 1,2-DCA dehalogenation and vice versa. Biodegradation was evaluated at the high concentrations found at some industrial sites (>10 mg/liter) and at lower concentrations found at former leaded-gasoline sites (1.9 to 3.7 mg/liter). At higher concentrations, the Dehalococcoides yield was 1 order of magnitude higher when bacteria were grown with 1,2-DCA than when they were grown with EDB, while μ̂'s were similar for the two compounds, ranging from 0.19 to 0.52 day−1 with 1,2-DCA to 0.28 to 0.36 day−1 for EDB. KS was larger for 1,2-DCA (15 to 25 mg/liter) than for EDB (1.8 to 3.7 mg/liter). In treatments that received both compounds, EDB was always consumed first and adversely impacted the kinetics of 1,2-DCA utilization. Furthermore, 1,2-DCA dechlorination was interrupted by the addition of EDB at a concentration 100 times lower than that of the remaining 1,2-DCA; use of 1,2-DCA did not resume until the EDB level decreased close to its maximum contaminant level (MCL). In lower-concentration experiments, the preferential consumption of EDB over 1,2-DCA was confirmed; both compounds were eventually dehalogenated to their respective MCLs (5 μg/liter for 1,2-DCA, 0.05 μg/liter for EDB). The enrichment culture grown with 1,2-DCA has the advantage of a more rapid transition to 1,2-DCA after EDB is consumed. PMID:23263950

  17. Gibberellins accumulate in the elongating endodermal cells of Arabidopsis root

    PubMed Central

    Shani, Eilon; Weinstain, Roy; Zhang, Yi; Castillejo, Cristina; Kaiserli, Eirini; Chory, Joanne; Tsien, Roger Y.; Estelle, Mark

    2013-01-01

    Plant hormones are small-molecule signaling compounds that are collectively involved in all aspects of plant growth and development. Unlike animals, plants actively regulate the spatial distribution of several of their hormones. For example, auxin transport results in the formation of auxin maxima that have a key role in developmental patterning. However, the spatial distribution of the other plant hormones, including gibberellic acid (GA), is largely unknown. To address this, we generated two bioactive fluorescent GA compounds and studied their distribution in Arabidopsis thaliana roots. The labeled GAs specifically accumulated in the endodermal cells of the root elongation zone. Pharmacological studies, along with examination of mutants affected in endodermal specification, indicate that GA accumulation is an active and highly regulated process. Our results strongly suggest the presence of an active GA transport mechanism that would represent an additional level of GA regulation. PMID:23382232

  18. A phospholipid uptake system in the model plant Arabidopsis thaliana.

    PubMed

    Poulsen, Lisbeth R; López-Marqués, Rosa L; Pedas, Pai R; McDowell, Stephen C; Brown, Elizabeth; Kunze, Reinhard; Harper, Jeffrey F; Pomorski, Thomas G; Palmgren, Michael

    2015-01-01

    Plants use solar energy to produce lipids directly from inorganic elements and are not thought to require molecular systems for lipid uptake from the environment. Here we show that Arabidopsis thaliana Aminophospholipid ATPase10 (ALA10) is a P4-type ATPase flippase that internalizes exogenous phospholipids across the plasma membrane, after which they are rapidly metabolized. ALA10 expression and phospholipid uptake are high in the epidermal cells of the root tip and in guard cells, the latter of which regulate the size of stomatal apertures to modulate gas exchange. ALA10-knockout mutants exhibit reduced phospholipid uptake at the root tips and guard cells and are affected in growth and transpiration. The presence of a phospholipid uptake system in plants is surprising. Our results suggest that one possible physiological role of this system is to internalize lysophosphatidylcholine, a signalling lipid involved in root development and stomatal control. PMID:26212235

  19. Demographic History of European Populations of Arabidopsis thaliana

    PubMed Central

    François, Olivier; Blum, Michael G. B.; Jakobsson, Mattias; Rosenberg, Noah A.

    2008-01-01

    The model plant species Arabidopsis thaliana is successful at colonizing land that has recently undergone human-mediated disturbance. To investigate the prehistoric spread of A. thaliana, we applied approximate Bayesian computation and explicit spatial modeling to 76 European accessions sequenced at 876 nuclear loci. We find evidence that a major migration wave occurred from east to west, affecting most of the sampled individuals. The longitudinal gradient appears to result from the plant having spread in Europe from the east ∼10,000 years ago, with a rate of westward spread of ∼0.9 km/year. This wave-of-advance model is consistent with a natural colonization from an eastern glacial refugium that overwhelmed ancient western lineages. However, the speed and time frame of the model also suggest that the migration of A. thaliana into Europe may have accompanied the spread of agriculture during the Neolithic transition. PMID:18483550

  20. Exogenous isoprene modulates gene expression in unstressed Arabidopsis thaliana plants.

    PubMed

    Harvey, Christopher M; Sharkey, Thomas D

    2016-06-01

    Isoprene is a well-studied volatile hemiterpene that protects plants from abiotic stress through mechanisms that are not fully understood. The antioxidant and membrane stabilizing potential of isoprene are the two most commonly invoked mechanisms. However, isoprene also affects phenylpropanoid metabolism, suggesting an additional role as a signalling molecule. In this study, microarray-based gene expression profiling reveals transcriptional reprogramming of Arabidopsis thaliana plants fumigated for 24 h with a physiologically relevant concentration of isoprene. Functional enrichment analysis of fumigated plants revealed enhanced heat- and light-stress-responsive processes in response to isoprene. Isoprene induced a network enriched in ERF and WRKY transcription factors, which may play a role in stress tolerance. The isoprene-induced up-regulation of phenylpropanoid biosynthetic genes was specifically confirmed using quantitative reverse transcription polymerase chain reaction. These results support a role for isoprene as a signalling molecule, in addition to its possible roles as an antioxidant and membrane thermoprotectant. PMID:26477606

  1. Chinese wild-growing Vitis amurensis ICE1 and ICE2 encode MYC-type bHLH transcription activators that regulate cold tolerance in Arabidopsis.

    PubMed

    Xu, Weirong; Jiao, Yuntong; Li, Ruimin; Zhang, Ningbo; Xiao, Dongming; Ding, Xiaoling; Wang, Zhenping

    2014-01-01

    Winter hardiness is an important trait for grapevine breeders and producers, so identification of the regulatory mechanisms involved in cold acclimation is of great potential value. The work presented here involves the identification of two grapevine ICE gene homologs, VaICE1 and VaICE2, from an extremely cold-tolerant accession of Chinese wild-growing Vitis amurnensis, which are phylogenetically related to other plant ICE1 genes. These two structurally different ICE proteins contain previously reported ICE-specific amino acid motifs, the bHLH-ZIP domain and the S-rich motif. Expression analysis revealed that VaICE1 is constitutively expressed but affected by cold stress, unlike VaICE2 that shows not such changed expression as a consequence of cold treatment. Both genes serve as transcription factors, potentiating the transactivation activities in yeasts and the corresponding proteins localized to the nucleus following transient expression in onion epidermal cells. Overexpression of either VaICE1 or VaICE2 in Arabidopsis increase freezing tolerance in nonacclimated plants. Moreover, we show that they result in multiple biochemical changes that were associated with cold acclimation: VaICE1/2-overexpressing plants had evaluated levels of proline, reduced contents of malondialdehyde (MDA) and decreased levels of electrolyte leakage. The expression of downstream cold responsive genes of CBF1, COR15A, and COR47 were significantly induced in Arabidopsis transgenically overexpressing VaICE1 or VaICE2 upon cold stress. VaICE2, but not VaICE1 overexpression induced KIN1 expression under cold-acclimation conditions. Our results suggest that VaICE1 and VaICE2 act as key regulators at an early step in the transcriptional cascade controlling freezing tolerance, and modulate the expression levels of various low-temperature associated genes involved in the C-repeat binding factor (CBF) pathway. PMID:25019620

  2. Chinese Wild-Growing Vitis amurensis ICE1 and ICE2 Encode MYC-Type bHLH Transcription Activators that Regulate Cold Tolerance in Arabidopsis

    PubMed Central

    Xu, Weirong; Jiao, Yuntong; Li, Ruimin; Zhang, Ningbo; Xiao, Dongming; Ding, Xiaoling; Wang, Zhenping

    2014-01-01

    Winter hardiness is an important trait for grapevine breeders and producers, so identification of the regulatory mechanisms involved in cold acclimation is of great potential value. The work presented here involves the identification of two grapevine ICE gene homologs, VaICE1 and VaICE2, from an extremely cold-tolerant accession of Chinese wild-growing Vitis amurnensis, which are phylogenetically related to other plant ICE1 genes. These two structurally different ICE proteins contain previously reported ICE-specific amino acid motifs, the bHLH-ZIP domain and the S-rich motif. Expression analysis revealed that VaICE1 is constitutively expressed but affected by cold stress, unlike VaICE2 that shows not such changed expression as a consequence of cold treatment. Both genes serve as transcription factors, potentiating the transactivation activities in yeasts and the corresponding proteins localized to the nucleus following transient expression in onion epidermal cells. Overexpression of either VaICE1 or VaICE2 in Arabidopsis increase freezing tolerance in nonacclimated plants. Moreover, we show that they result in multiple biochemical changes that were associated with cold acclimation: VaICE1/2-overexpressing plants had evaluated levels of proline, reduced contents of malondialdehyde (MDA) and decreased levels of electrolyte leakage. The expression of downstream cold responsive genes of CBF1, COR15A, and COR47 were significantly induced in Arabidopsis transgenically overexpressing VaICE1 or VaICE2 upon cold stress. VaICE2, but not VaICE1 overexpression induced KIN1 expression under cold-acclimation conditions. Our results suggest that VaICE1 and VaICE2 act as key regulators at an early step in the transcriptional cascade controlling freezing tolerance, and modulate the expression levels of various low-temperature associated genes involved in the C-repeat binding factor (CBF) pathway. PMID:25019620

  3. Antagonistic Interaction of BLADE-ON-PETIOLE1 and 2 with BREVIPEDICELLUS and PENNYWISE Regulates Arabidopsis Inflorescence Architecture1[C][W][OA

    PubMed Central

    Khan, Madiha; Xu, Mingli; Murmu, Jhadeswar; Tabb, Paul; Liu, Yuanyuan; Storey, Kathryn; McKim, Sarah M.; Douglas, Carl J.; Hepworth, Shelley R.

    2012-01-01

    The transition to flowering in many plant species, including Arabidopsis (Arabidopsis thaliana), is marked by the elongation of internodes to make an inflorescence upon which lateral branches and flowers are arranged in a characteristic pattern. Inflorescence patterning relies in part on the activities of two three-amino-acid loop-extension homeodomain transcription factors: BREVIPEDICELLUS (BP) and PENNYWISE (PNY) whose interacting products also promote meristem function. We examine here the genetic interactions between BP-PNY whose expression is up-regulated in stems at the floral transition, and the lateral organ boundary genes BLADE-ON-PETIOLE1 (BOP1) and BOP2, whose expression is restricted to pedicel axils. Our data show that bp and pny inflorescence defects are caused by BOP1/2 gain of function in stems and pedicels. Compatible with this, inactivation of BOP1/2 rescues these defects. BOP expression domains are differentially enlarged in bp and pny mutants, corresponding to the distinctive patterns of growth restriction in these mutants leading to compacted internodes and clustered or downward-oriented fruits. Our data indicate that BOP1/2 are positive regulators of KNOTTED1-LIKE FROM ARABIDOPSIS THALIANA6 expression and that growth restriction in BOP1/2 gain-of-function plants requires KNOTTED1-LIKE FROM ARABIDOPSIS THALIANA6. Antagonism between BOP1/2 and BP is explained in part by their reciprocal regulation of gene expression, as evidenced by the identification of lignin biosynthetic genes that are repressed by BP and activated by BOP1/2 in stems. These data reveal BOP1/2 gain of function as the basis of bp and pny inflorescence defects and reveal how antagonism between BOP1/2 and BP-PNY contributes to inflorescence patterning in a model plant species. PMID:22114095

  4. RootScape: a landmark-based system for rapid screening of root architecture in Arabidopsis.

    PubMed

    Ristova, Daniela; Rosas, Ulises; Krouk, Gabriel; Ruffel, Sandrine; Birnbaum, Kenneth D; Coruzzi, Gloria M

    2013-03-01

    The architecture of plant roots affects essential functions including nutrient and water uptake, soil anchorage, and symbiotic interactions. Root architecture comprises many features that arise from the growth of the primary and lateral roots. These root features are dictated by the genetic background but are also highly responsive to the environment. Thus, root system architecture (RSA) represents an important and complex trait that is highly variable, affected by genotype × environment interactions, and relevant to survival/performance. Quantification of RSA in Arabidopsis (Arabidopsis thaliana) using plate-based tissue culture is a very common and relatively rapid assay, but quantifying RSA represents an experimental bottleneck when it comes to medium- or high-throughput approaches used in mutant or genotype screens. Here, we present RootScape, a landmark-based allometric method for rapid phenotyping of RSA using Arabidopsis as a case study. Using the software AAMToolbox, we created a 20-point landmark model that captures RSA as one integrated trait and used this model to quantify changes in the RSA of Arabidopsis (Columbia) wild-type plants grown under different hormone treatments. Principal component analysis was used to compare RootScape with conventional methods designed to measure root architecture. This analysis showed that RootScape efficiently captured nearly all the variation in root architecture detected by measuring individual root traits and is 5 to 10 times faster than conventional scoring. We validated RootScape by quantifying the plasticity of RSA in several mutant lines affected in hormone signaling. The RootScape analysis recapitulated previous results that described complex phenotypes in the mutants and identified novel gene × environment interactions. PMID:23335624

  5. Nitrone Cycloadditions of 1,2-Cyclohexadiene

    PubMed Central

    Barber, Joyann S.; Styduhar, Evan D.; Pham, Hung V.; McMahon, Travis C.; Houk, K. N.; Garg, Neil K.

    2016-01-01

    We report the first 1,3-dipolar cycloadditions of 1,2-cyclohexadiene, a rarely exploited strained allene. 1,2-Cyclohexadiene is generated in situ under mild conditions and trapped with nitrones to give isoxazolidine products in synthetically useful yields. The reactions occur regioselectively and exhibit a notable endo preference, thus resulting in the controlled formation of two new bonds and two stereogenic centers. DFT calculations of stepwise and concerted reaction pathways are used to rationalize the observed selectivities. Moreover, the strategic manipulation of nitrone cycloadducts demonstrates the utility of this methodology for the assembly of compounds bearing multiple heterocyclic units. These studies showcase the exploitation of a traditionally avoided reactive intermediate in chemical synthesis. PMID:26854652

  6. The Thellungiella salsuginea tonoplast aquaporin TsTIP1;2 functions in protection against multiple abiotic stresses.

    PubMed

    Wang, Li-Li; Chen, An-Ping; Zhong, Nai-Qin; Liu, Ning; Wu, Xiao-Min; Wang, Fang; Yang, Chun-Lin; Romero, Michael F; Xia, Gui-Xian

    2014-01-01

    Examination of aquaporin (AQP) membrane channels in extremophile plants may increase our understanding of plant tolerance to high salt, drought or other conditions. Here, we cloned a tonoplast AQP gene (TsTIP1;2) from the halophyte Thellungiella salsuginea and characterized its biological functions. TsTIP1;2 transcripts accumulate to high levels in several organs, increasing in response to multiple external stimuli. Ectopic overexpression of TsTIP1;2 in Arabidopsis significantly increased plant tolerance to drought, salt and oxidative stresses. TsTIP1;2 had water channel activity when expressed in Xenopus oocytes. TsTIP1;2 was also able to conduct H₂O₂ molecules into yeast cells in response to oxidative stress. TsTIP1;2 was not permeable to Na(+) in Xenopus oocytes, but it could facilitate the entry of Na(+) ions into plant cell vacuoles by an indirect process under high-salinity conditions. Collectively, these data showed that TsTIP1;2 could mediate the conduction of both H₂O and H₂O₂ across membranes, and may act as a multifunctional contributor to survival of T. salsuginea in highly stressful habitats. PMID:24214268

  7. Arabidopsis gene expression patterns during spaceflight

    NASA Astrophysics Data System (ADS)

    Paul, A.-L.; Ferl, R. J.

    The exposure of Arabidopsis thaliana (Arabidopsis) plants to spaceflight environments resulted in the differential expression of hundreds of genes. A 5 day mission on orbiter Columbia in 1999 (STS-93) carried transgenic Arabidopsis plants engineered with a transgene composed of the alcohol dehydrogenase (Adh) gene promoter linked to the β -Glucuronidase (GUS) reporter gene. The plants were used to evaluate the effects of spaceflight on two fronts. First, expression patterns visualized with the Adh/GUS transgene were used to address specifically the possibility that spaceflight induces a hypoxic stress response, and to assess whether any spaceflight response was similar to control terrestrial hypoxia-induced gene expression patterns. (Paul et al., Plant Physiol. 2001, 126:613). Second, genome-wide patterns of native gene expression were evaluated utilizing the Affymetrix ATH1 GeneChip? array of 8,000 Arabidopsis genes. As a control for the veracity of the array analyses, a selection of genes identified with the arrays was further characterized with quantitative Real-Time RT PCR (ABI - TaqmanTM). Comparison of the patterns of expression for arrays of hybridized with RNA isolated from plants exposed to spaceflight compared to the control arrays revealed hundreds of genes that were differentially expressed in response to spaceflight, yet most genes that are hallmarks of hypoxic stress were unaffected. These results will be discussed in light of current models for plant responses to the spaceflight environment, and with regard to potential future flight opportunities.

  8. HYDROPONIC METHOD FOR CULTURING POPULATIONS OF ARABIDOPSIS

    EPA Science Inventory

    A plant life-cycle bioassay using Arabidopsis thaliana (L.) Heynh. was developed to detect potential chemical phytotoxicity. The bioassay requires large numbers of plants to maximize the probability of detecting deleterious effect and to avoid any bias that could occur if only a ...

  9. Arabidopsis thaliana glucuronosyltransferase in family GT14.

    PubMed

    Dilokpimol, Adiphol; Geshi, Naomi

    2014-01-01

    Arabinogalactan proteins are abundant cell-surface proteoglycans in plants and are involved in many cellular processes including somatic embryogenesis, cell-cell interactions, and cell elongation. We reported a glucuronosyltransferase encoded by Arabidopsis AtGlcAT14A, which catalyzes an addition of glucuronic acid residues to β-1,3- and β-1,6-linked galactans of arabinogalactan (Knoch et al. 2013). The knockout mutant of this gene resulted in the enhanced growth rate of hypocotyls and roots of seedlings, suggesting an involvement of AtGlcAT14A in cell elongation. AtGlcAt14A belongs to the family GT14 in the Carbohydrate Active Enzyme database (CAZy; www.cazy.org), in which a total of 11 proteins, including AtGLCAT14A, are classified from Arabidopsis thaliana. In this paper, we report the enzyme activities for the rest of the Arabidopsis GT14 isoforms, analyzed in the same way as for AtGlcAT14A. Evidently, two other Arabidopsis GT14 isoforms, At5g15050 and At2g37585, also possess the glucuronosyltransferase activity adding glucuronic acid residues to β-1,3- and β-1,6-linked galactans. Therefore, we named At5g15050 and At2g37585 as AtGlcAT14B and AtGlcAT14C, respectively. PMID:24739253

  10. Shotgun Proteomic Analysis of Arabidopsis thaliana Leaves

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two shotgun tandem mass spectrometry proteomics approaches, Multidimensional Protein Identification Technology (MudPIT) and 1D-Gel-LC-MS/MS, were used to identify Arabidopsis thaliana leaf proteins. These methods utilize different protein/peptide separation strategies. Detergents not compatible wit...

  11. Imaging lipid droplets in Arabidopsis mutants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Confocal fluorescence microscopy was adapted for the imaging of neutral lipids in plant leaves with defects in normal lipid metabolism using two different fluorescent dyes. Disruptions in a gene locus, At4g24160, yielded Arabidopsis thaliana plants with a preponderance of oil bodies in their leaves ...

  12. Engineering calcium oxalate crystal formation in Arabidopsis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many plants accumulate crystals of calcium oxalate. Just how these crystals form remains unknown. To gain insight into the mechanisms regulating calcium oxalate crystal formation, a crystal engineering approach was initiated utilizing the non-crystal accumulating plant, Arabidopsis. The success of t...

  13. Equilibria of 1,1,2,-trichloro-1,2,2-trifluoroethane on activated carbons

    SciTech Connect

    Cho, S.Y.; Lee, Y.Y.

    1995-07-01

    ChloroFluoroCarbons (CFCs) are now considered to be the prime contribution to stratospheric ozone depletion. As a result, the use of activated carbons to adsorb specific CFCs has received great attention. In this paper, the equilibrium adsorption characteristics of 1,1,2-trichloro-1,2,2-trifluoroethane vapor on different-shaped carbons were studied. Adsorption isotherms of 1,2,2-trichloro-1,2,2-trifluoroethane on an activated carbon pellet and an activated carbon felt were measured. The equilibria of 1,1,2-trichloro-1,2,2-trifluoroethane on the activated carbon pellet having a dual pore structure were expressed by the Redlich-Peterson equation, and equilibrium constants were expressed as functions of temperature from 298 to 393 K. On the other hand, the equilibria of 1,1,2-trichloro-1,2,2-trifluoroethane on the activated carbon felt having a relatively uniform pore structure were interpreted by the Dubinin-Radushkevich correlation based on the micropore volume filling theory. The affinity coefficient was correlated by the molar polarization.

  14. 1,1,2-Trichloro-1,2,2-trifluoroethane (CFC-113)

    Integrated Risk Information System (IRIS)

    1,1,2 - Trichloro - 1,2,2 - trifluoroethane ( CFC - 113 ) ; CASRN 76 - 13 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health

  15. Differential selection of sodium and potassium ions by TsHKT1;2.

    PubMed

    Ali, Akhtar; Yun, Dae-Jin

    2016-08-01

    Among abiotic stresses, soil salinity is a major threat to agriculture. To address and control the effects of high salinity on plants, it is important to understand their responses to salt stress that disturbs the homeostatic equilibrium at cellular and molecular levels. To deal and control effects of high salinity on plants, it is important to understand their responses to salt stress that disturbs the homeostatic equilibrium at cellular and molecular levels. In this regard, halophytes (salt tolerant plants) can provide superior models for the study of salt stress defense parameters compared to glycophytes (salt sensitive species). TsHKT1;2 one of the 3 copies of HKT1 in the Arabidopsis relative halophyte, Thellungiella salsuginea acts as a potassium transporter, even under salt stress. TsHKT1;2 includes a conserved Asp (D) residue in the 2(nd) pore-loop domain. Most other HKT1 sequences, including AtHKT1, contain Asn (N) in this position. We found that athkt1-1 plants complemented by TsHKT1;2 under native AtHKT1 promoter were more tolerant to salt stress, while substitution of Asp (D207) by Asn (N) significantly reduced resistance to salinity. We suggest that the presence of Asn or Asp is the essential feature that defines and establishes cation selectivity in dicot HKT1-type transporters. PMID:27380309

  16. Dominant and recessive mutations in the Raf-like kinase HT1 gene completely disrupt stomatal responses to CO2 in Arabidopsis

    PubMed Central

    Hashimoto-Sugimoto, Mimi; Negi, Juntaro; Monda, Keina; Higaki, Takumi; Isogai, Yasuhiro; Nakano, Toshiaki; Hasezawa, Seiichiro; Iba, Koh

    2016-01-01

    HT1 (HIGH LEAF TEMPERATURE 1) is the first component associated with changes in stomatal aperture in response to CO2 to be isolated by forward genetic screening. The HT1 gene encodes a protein kinase expressed mainly in guard cells. The loss-of-function ht1-1 and ht1-2 mutants in Arabidopsis thaliana have CO2-hypersensitive stomatal closure with concomitant reductions in their kinase activities in vitro. In addition to these mutants, in this study we isolate or obtaine five new ht1 alleles (ht1-3, ht1-4, ht1-5, ht1-6, and ht1-7). Among the mutants, only ht1-3 has a dominant mutant phenotype and has widely opened stomata due to CO2 insensitivity. The ht1-3 mutant has a missense mutation affecting a non-conserved residue (R102K), whereas the other six recessive mutants have mutations in highly conserved residues in the catalytic domains required for kinase activity. We found that the dominant mutation does not affect the expression of HT1 or the ability to phosphorylate casein, a universal kinase substrate, but it does affect autophosphorylation activity in vitro. A 3D structural model of HT1 also shows that the R102 residue protrudes from the surface of the kinase, implying a role for the formation of oligomers and/or interaction with its targets. We demonstrate that both the loss-of-function and gain-of-function ht1 mutants have completely disrupted CO2 responses, although they have normal responses to ABA. Furthermore, light-induced stomatal opening is smaller in ht1-3 and much smaller in ht1-2. Taken together, these results indicate that HT1 is a critical regulator for CO2 signaling and is partially involved in the light-induced stomatal opening pathway. PMID:27034327

  17. Dominant and recessive mutations in the Raf-like kinase HT1 gene completely disrupt stomatal responses to CO2 in Arabidopsis.

    PubMed

    Hashimoto-Sugimoto, Mimi; Negi, Juntaro; Monda, Keina; Higaki, Takumi; Isogai, Yasuhiro; Nakano, Toshiaki; Hasezawa, Seiichiro; Iba, Koh

    2016-05-01

    HT1 (HIGH LEAF TEMPERATURE 1) is the first component associated with changes in stomatal aperture in response to CO2 to be isolated by forward genetic screening. The HT1 gene encodes a protein kinase expressed mainly in guard cells. The loss-of-function ht1-1 and ht1-2 mutants in Arabidopsis thaliana have CO2-hypersensitive stomatal closure with concomitant reductions in their kinase activities in vitro In addition to these mutants, in this study we isolate or obtaine five new ht1 alleles (ht1-3, ht1-4, ht1-5, ht1-6, and ht1-7). Among the mutants, only ht1-3 has a dominant mutant phenotype and has widely opened stomata due to CO2 insensitivity. The ht1-3 mutant has a missense mutation affecting a non-conserved residue (R102K), whereas the other six recessive mutants have mutations in highly conserved residues in the catalytic domains required for kinase activity. We found that the dominant mutation does not affect the expression of HT1 or the ability to phosphorylate casein, a universal kinase substrate, but it does affect autophosphorylation activity in vitro A 3D structural model of HT1 also shows that the R102 residue protrudes from the surface of the kinase, implying a role for the formation of oligomers and/or interaction with its targets. We demonstrate that both the loss-of-function and gain-of-function ht1 mutants have completely disrupted CO2 responses, although they have normal responses to ABA. Furthermore, light-induced stomatal opening is smaller in ht1-3 and much smaller in ht1-2 Taken together, these results indicate that HT1 is a critical regulator for CO2 signaling and is partially involved in the light-induced stomatal opening pathway. PMID:27034327

  18. Regulatory function of Arabidopsis lipid transfer protein 1 (LTP1) in ethylene response and signaling.

    PubMed

    Wang, Honglin; Sun, Yue; Chang, Jianhong; Zheng, Fangfang; Pei, Haixia; Yi, Yanjun; Chang, Caren; Dong, Chun-Hai

    2016-07-01

    Ethylene as a gaseous plant hormone is directly involved in various processes during plant growth and development. Much is known regarding the ethylene receptors and regulatory factors in the ethylene signal transduction pathway. In Arabidopsis thaliana, REVERSION-TO-ETHYLENE SENSITIVITY1 (RTE1) can interact with and positively regulates the ethylene receptor ETHYLENE RESPONSE1 (ETR1). In this study we report the identification and characterization of an RTE1-interacting protein, a putative Arabidopsis lipid transfer protein 1 (LTP1) of unknown function. Through bimolecular fluorescence complementation, a direct molecular interaction between LTP1 and RTE1 was verified in planta. Analysis of an LTP1-GFP fusion in transgenic plants and plasmolysis experiments revealed that LTP1 is localized to the cytoplasm. Analysis of ethylene responses showed that the ltp1 knockout is hypersensitive to 1-aminocyclopropanecarboxylic acid (ACC), while LTP1 overexpression confers insensitivity. Analysis of double mutants etr1-2 ltp1 and rte1-3 ltp1 demonstrates a regulatory function of LTP1 in ethylene receptor signaling through the molecular association with RTE1. This study uncovers a novel function of Arabidopsis LTP1 in the regulation of ethylene response and signaling. PMID:27097903

  19. Arabidopsis non-specific phospholipase C1: characterization and its involvement in response to heat stress

    PubMed Central

    Krčková, Zuzana; Brouzdová, Jitka; Daněk, Michal; Kocourková, Daniela; Rainteau, Dominique; Ruelland, Eric; Valentová, Olga; Pejchar, Přemysl; Martinec, Jan

    2015-01-01

    The Arabidopsis non-specific phospholipase C1 (NPC) protein family is encoded by the genes NPC1 – NPC6. It has been shown that NPC4 and NPC5 possess phospholipase C activity; NPC3 has lysophosphatidic acid phosphatase activity. NPC3, 4 and 5 play roles in the responses to hormones and abiotic stresses. NPC1, 2 and 6 has not been studied functionally yet. We found that Arabidopsis NPC1 expressed in Escherichia coli possesses phospholipase C activity in vitro. This protein was able to hydrolyse phosphatidylcholine to diacylglycerol. NPC1-green fluorescent protein was localized to secretory pathway compartments in Arabidopsis roots. In the knock out T-DNA insertion line NPC1 (npc1) basal thermotolerance was impaired compared with wild-type (WT); npc1 exhibited significant decreases in survival rate and chlorophyll content at the seventh day after heat stress (HS). Conversely, plants overexpressing NPC1 (NPC1-OE) were more resistant to HS compared with WT. These findings suggest that NPC1 is involved in the plant response to heat. PMID:26581502

  20. VIP1 is very important/interesting protein 1 regulating touch responses of Arabidopsis

    PubMed Central

    Tsugama, Daisuke; Liu, Shenkui; Takano, Tetsuo

    2016-01-01

    ABSTRACT VIP1 (VIRE2-INTERACTING PROTEIN 1) is a bZIP transcription factor in Arabidopsis thaliana. VIP1 and its close homologs (i.e., Arabidopsis group I bZIP proteins) are present in the cytoplasm under steady conditions, but are transiently localized to the nucleus when cells are exposed to hypo-osmotic conditions, which mimic mechanical stimuli such as touch. Recently we have reported that overexpression of a repression domain-fused form of VIP1 represses the expression of some touch-responsive genes, changes structures and/or local auxin responses of the root cap cells, and enhances the touch-induced root waving. This raises the possibility that VIP1 suppresses touch-induced responses. VIP1 should be useful to further characterize touch responses of plants. Here we discuss 2 seemingly interesting perspectives about VIP1: (1) What factors are involved in regulating the nuclear localization of VIP1?; (2) What can be done to further characterize the physiological functions of VIP1 and other Arabidopsis group I bZIP proteins? PMID:27171129

  1. Arabidopsis non-specific phospholipase C1: characterization and its involvement in response to heat stress.

    PubMed

    Krčková, Zuzana; Brouzdová, Jitka; Daněk, Michal; Kocourková, Daniela; Rainteau, Dominique; Ruelland, Eric; Valentová, Olga; Pejchar, Přemysl; Martinec, Jan

    2015-01-01

    The Arabidopsis non-specific phospholipase C (NPC) protein family is encoded by the genes NPC1 - NPC6. It has been shown that NPC4 and NPC5 possess phospholipase C activity; NPC3 has lysophosphatidic acid phosphatase activity. NPC3, 4 and 5 play roles in the responses to hormones and abiotic stresses. NPC1, 2 and 6 has not been studied functionally yet. We found that Arabidopsis NPC1 expressed in Escherichia coli possesses phospholipase C activity in vitro. This protein was able to hydrolyse phosphatidylcholine to diacylglycerol. NPC1-green fluorescent protein was localized to secretory pathway compartments in Arabidopsis roots. In the knock out T-DNA insertion line NPC1 (npc1) basal thermotolerance was impaired compared with wild-type (WT); npc1 exhibited significant decreases in survival rate and chlorophyll content at the seventh day after heat stress (HS). Conversely, plants overexpressing NPC1 (NPC1-OE) were more resistant to HS compared with WT. These findings suggest that NPC1 is involved in the plant response to heat. PMID:26581502

  2. The LIKE SEX FOUR2 regulates root development by modulating reactive oxygen species homeostasis in Arabidopsis

    PubMed Central

    Zhao, Pingzhi; Sokolov, Lubomir N.; Ye, Jian; Tang, Cheng-Yi; Shi, Jisen; Zhen, Yan; Lan, Wenzhi; Hong, Zhi; Qi, Jinliang; Lu, Gui-Hua; Pandey, Girdhar K.; Yang, Yong-Hua

    2016-01-01

    Maintaining reactive oxygen species (ROS) homeostasis plays a central role in plants, and is also critical for plant root development. Threshold levels of ROS act as signals for elongation and differentiation of root cells. The protein phosphatase LIKE SEX FOUR2 (LSF2) has been reported to regulate starch metabolism in Arabidopsis, but little is known about the mechanism how LSF2 affect ROS homeostasis. Here, we identified that LSF2 function as a component modulating ROS homeostasis in response to oxidative stress and, thus regulate root development. Compared with wild type Arabidopsis, lsf2-1 mutant exhibited reduced rates of superoxide generation and higher levels of hydrogen peroxide upon oxidative stress treatments. The activities of several antioxidant enzymes, including superoxide dismutase, catalase, and ascorbate peroxidase, were also affected in lsf2-1 mutant under these oxidative stress conditions. Consequently, lsf2-1 mutant exhibited the reduced root growth but less inhibition of root hair formation compared to wild type Arabidopsis plants. Importantly, protein phosphatase LSF2 interacted with mitogen-activated protein kinase 8 (MPK8), a known component of ROS homeostasis pathways in the cytoplasm. These findings indicated the novel function of LSF2 that controls ROS homeostasis to regulate root development. PMID:27349915

  3. The LIKE SEX FOUR2 regulates root development by modulating reactive oxygen species homeostasis in Arabidopsis.

    PubMed

    Zhao, Pingzhi; Sokolov, Lubomir N; Ye, Jian; Tang, Cheng-Yi; Shi, Jisen; Zhen, Yan; Lan, Wenzhi; Hong, Zhi; Qi, Jinliang; Lu, Gui-Hua; Pandey, Girdhar K; Yang, Yong-Hua

    2016-01-01

    Maintaining reactive oxygen species (ROS) homeostasis plays a central role in plants, and is also critical for plant root development. Threshold levels of ROS act as signals for elongation and differentiation of root cells. The protein phosphatase LIKE SEX FOUR2 (LSF2) has been reported to regulate starch metabolism in Arabidopsis, but little is known about the mechanism how LSF2 affect ROS homeostasis. Here, we identified that LSF2 function as a component modulating ROS homeostasis in response to oxidative stress and, thus regulate root development. Compared with wild type Arabidopsis, lsf2-1 mutant exhibited reduced rates of superoxide generation and higher levels of hydrogen peroxide upon oxidative stress treatments. The activities of several antioxidant enzymes, including superoxide dismutase, catalase, and ascorbate peroxidase, were also affected in lsf2-1 mutant under these oxidative stress conditions. Consequently, lsf2-1 mutant exhibited the reduced root growth but less inhibition of root hair formation compared to wild type Arabidopsis plants. Importantly, protein phosphatase LSF2 interacted with mitogen-activated protein kinase 8 (MPK8), a known component of ROS homeostasis pathways in the cytoplasm. These findings indicated the novel function of LSF2 that controls ROS homeostasis to regulate root development. PMID:27349915

  4. TANG1, Encoding a Symplekin_C Domain-Contained Protein, Influences Sugar Responses in Arabidopsis.

    PubMed

    Zheng, Leiying; Shang, Li; Chen, Xing; Zhang, Limin; Xia, Yan; Smith, Caroline; Bevan, Michael W; Li, Yunhai; Jing, Hai-Chun

    2015-07-01

    Sugars not only serve as energy and cellular carbon skeleton but also function as signaling molecules regulating growth and development in plants. Understanding the molecular mechanisms in sugar signaling pathways will provide more information for improving plant growth and development. Here, we describe a sugar-hypersensitive recessive mutant, tang1. Light-grown tang1 mutants have short roots and increased starch and anthocyanin contents when grown on high-sugar concentration medium. Dark-grown tang1 plants exhibit sugar-hypersensitive hypocotyl elongation and enhanced dark development. The tang1 mutants also show an enhanced response to abscisic acid but reduced response to ethylene. Thus, tang1 displays a range of alterations in sugar signaling-related responses. The TANG1 gene was isolated by a map-based cloning approach and encodes a previously uncharacterized unique protein with a predicted Symplekin tight-junction protein C terminus. Expression analysis indicates that TANG1 is ubiquitously expressed at moderate levels in different organs and throughout the Arabidopsis (Arabidopsis thaliana) life cycle; however, its expression is not affected by high-sugar treatment. Genetic analysis shows that PRL1 and TANG1 have additive effects on sugar-related responses. Furthermore, the mutation of TANG1 does not affect the expression of genes involved in known sugar signaling pathways. Taken together, these results suggest that TANG1, a unique gene, plays an important role in sugar responses in Arabidopsis. PMID:26002908

  5. Arabidopsis genes essential for seedling viability: isolation of insertional mutants and molecular cloning.

    PubMed Central

    Budziszewski, G J; Lewis, S P; Glover, L W; Reineke, J; Jones, G; Ziemnik, L S; Lonowski, J; Nyfeler, B; Aux, G; Zhou, Q; McElver, J; Patton, D A; Martienssen, R; Grossniklaus, U; Ma, H; Law, M; Levin, J Z

    2001-01-01

    We have undertaken a large-scale genetic screen to identify genes with a seedling-lethal mutant phenotype. From screening approximately 38,000 insertional mutant lines, we identified >500 seedling-lethal mutants, completed cosegregation analysis of the insertion and the lethal phenotype for >200 mutants, molecularly characterized 54 mutants, and provided a detailed description for 22 of them. Most of the seedling-lethal mutants seem to affect chloroplast function because they display altered pigmentation and affect genes encoding proteins predicted to have chloroplast localization. Although a high level of functional redundancy in Arabidopsis might be expected because 65% of genes are members of gene families, we found that 41% of the essential genes found in this study are members of Arabidopsis gene families. In addition, we isolated several interesting classes of mutants and genes. We found three mutants in the recently discovered nonmevalonate isoprenoid biosynthetic pathway and mutants disrupting genes similar to Tic40 and tatC, which are likely to be involved in chloroplast protein translocation. Finally, we directly compared T-DNA and Ac/Ds transposon mutagenesis methods in Arabidopsis on a genome scale. In each population, we found only about one-third of the insertion mutations cosegregated with a mutant phenotype. PMID:11779813

  6. Dysfunctional mitochondria regulate the size of root apical meristem and leaf development in Arabidopsis

    PubMed Central

    Hsieh, Wei-Yu; Liao, Jo-Chien; Hsieh, Ming-Hsiun

    2015-01-01

    Mitochondria play an important role in maintaining metabolic and energy homeostasis in the plant cell. Thus, perturbation of mitochondrial structure and function will affect plant growth and development. Arabidopsis slow growth3 (slo3) is defective in At3g61360 that encodes a pentatricopeptide repeat (PPR) protein. Analysis of slo3 mitochondrial RNA metabolism revealed that the splicing of nad7 intron 2 is impaired, which leads to a dramatic reduction in complex I activity. So the SLO3 PPR protein is a splicing factor that is required for the removal of nad7 intron 2 in Arabidopsis. The slo3 mutant plants have obvious phenotypes with severe growth retardation and delayed development. The size of root apical meristem (RAM) is reduced and the production of meristem cells is decreased in slo3. Furthermore, the rosette leaves of slo3 are curled or crinkled, which may be derived from uneven growth of the leaf surface. The underlying mechanisms by which dysfunctional mitochondria affect these growth and developmental phenotypes have yet to be established. Nonetheless, plant hormone auxin is known to play an important role in orchestrating the development of RAM and leaf shape. It is possible that dysfunctional mitochondria may interact with auxin signaling pathways to regulate the boundary of RAM and the cell division arrest front during leaf growth in Arabidopsis. PMID:26237004

  7. Stereodynamics of small 1,2-dialkyldiaziridines.

    PubMed

    Kamuf, Matthias; Trapp, Oliver

    2013-04-01

    Diaziridines are very interesting representatives of organic compounds containing stereogenic nitrogen atoms. In particular, 1,2-dialkyldiaziridines show extraordinarily high stereointegrity. The lone electron pairs of the nitrogen atoms are in trans configuration, avoiding a four-electron repulsive interaction. Furthermore, the trans configuration of the substituents at the nitrogen atoms is energetically favored because of reduced steric interactions. Therefore only two stereoisomers (enantiomers) are observed. At elevated temperatures the enantiomers are interconverting because of the limited stereointegrity of the chirotopic nitrogen atoms. The enantiomerization rate constants and the activation parameters of interconversion are of great interest. Here, we investigated the stereodynamics of a set of small 1,2-dialkyldiaziridines bearing short substituents (Me, Et, iPr, tBu), using enantioselective dynamic gas chromatography (DGC). Separation of enantiomers of all compounds, including the highly volatile 1,2-dimethyldiaziridine, was achieved using heptakis(2,3-di-O-ethyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin in 50% PS086 (w/w) as chiral stationary phase in fused silica capillaries with a length of up to 50 m. Measurements at variable temperatures were performed and reaction rate constants were determined using the unified equation of chromatography implemented in the software DCXplorer. The activation barriers at room temperature for 1-(tert-butyl)-2-ethyldiaziridine, ΔG(╪)(298K) = 123.8 kJ mol(-1) (ΔH(╪) = 115.5±2.9 kJ mol(-1), ΔS(╪) = -28±1 J mol(-1) K(-1)), and 1-ethyl-2-isopropyldiaziridine, ΔG(╪)(298K) = 124.2 kJ mol(-1) (ΔH(╪) = 113.1±2.4 kJ mol(-1), ΔS(╪) = -37±2 J mol(-1) K(-1)), were determined, representing some of the highest values observed for nitrogen inversion in diaziridines. PMID:23401088

  8. (1+2)-dimensional strongly nonlocal solitons

    SciTech Connect

    Ouyang Shigen; Guo Qi

    2007-11-15

    Approximate solutions of (1+2)-dimensional strongly nonlocal solitons (SNSs) are presented. It is shown that the power of a SNS in a nematic liquid crystal is in direct proportion to the second power of the degree of nonlocality, the power of a SNS in a nonlocal medium with a logarithmic nonlocal response is in inverse proportion to the second power of its beamwidth, and the power of a SNS in a nonlocal medium with an sth-power decay nonlocal response is in direct proportion to the (s+2)th power of the degree of nonlocality.

  9. Spin-1/2 Optical Lattice Clock

    SciTech Connect

    Lemke, N. D.; Ludlow, A. D.; Barber, Z. W.; Fortier, T. M.; Diddams, S. A.; Jiang, Y.; Jefferts, S. R.; Heavner, T. P.; Parker, T. E.; Oates, C. W.

    2009-08-07

    We experimentally investigate an optical clock based on {sup 171}Yb (I=1/2) atoms confined in an optical lattice. We have evaluated all known frequency shifts to the clock transition, including a density-dependent collision shift, with a fractional uncertainty of 3.4x10{sup -16}, limited principally by uncertainty in the blackbody radiation Stark shift. We measured the absolute clock transition frequency relative to the NIST-F1 Cs fountain clock and find the frequency to be 518 295 836 590 865.2(0.7) Hz.

  10. The Arabidopsis lyrata genome sequence and the basis of rapid genome size change

    SciTech Connect

    Hu, Tina T.; Pattyn, Pedro; Bakker, Erica G.; Cao, Jun; Cheng, Jan-Fang; Clark, Richard M.; Fahlgren, Noah; Fawcett, Jeffrey A.; Grimwood, Jane; Gundlach, Heidrun; Haberer, Georg; Hollister, Jesse D.; Ossowski, Stephan; Ottilar, Robert P.; Salamov, Asaf A.; Schneeberger, Korbinian; Spannagl, Manuel; Wang, Xi; Yang, Liang; Nasrallah, Mikhail E.; Bergelson, Joy; Carrington, James C.; Gaut, Brandon S.; Schmutz, Jeremy; Mayer, Klaus F. X.; Van de Peer, Yves; Grigoriev, Igor V.; Nordborg, Magnus; Weigel, Detlef; Guo, Ya-Long

    2011-04-29

    In our manuscript, we present a high-quality genome sequence of the Arabidopsis thaliana relative, Arabidopsis lyrata, produced by dideoxy sequencing. We have performed the usual types of genome analysis (gene annotation, dN/dS studies etc. etc.), but this is relegated to the Supporting Information. Instead, we focus on what was a major motivation for sequencing this genome, namely to understand how A. thaliana lost half its genome in a few million years and lived to tell the tale. The rather surprising conclusion is that there is not a single genomic feature that accounts for the reduced genome, but that every aspect centromeres, intergenic regions, transposable elements, gene family number is affected through hundreds of thousands of cuts. This strongly suggests that overall genome size in itself is what has been under selection, a suggestion that is strongly supported by our demonstration (using population genetics data from A. thaliana) that new deletions seem to be driven to fixation.

  11. Components of the Arabidopsis nuclear pore complex play multiple diverse roles in control of plant growth

    PubMed Central

    Parry, Geraint

    2014-01-01

    The nuclear pore complex (NPC) is a multisubunit protein conglomerate that facilitates movement of RNA and protein between the nucleus and cytoplasm. Relatively little is known regarding the influence of the Arabidopsis NPC on growth and development. Seedling development, flowering time, nuclear morphology, mRNA accumulation, and gene expression changes in Arabidopsis nucleoporin mutants were investigated. Nuclear export of mRNA is differentially affected in plants with defects in nucleoporins that lie in different NPC subcomplexes. This study reveals differences in the manner by which nucleoporins alter molecular and plant growth phenotypes, suggesting that nuclear pore subcomplexes play distinct roles in nuclear transport and reveal a possible feedback relationship between the expression of genes involved in nuclear transport. PMID:25165147

  12. Light-independent developmental regulation of cab gene expression in Arabidopsis thaliana seedlings.

    PubMed Central

    Brusslan, J A; Tobin, E M

    1992-01-01

    We found a transient increase in the amount of mRNA for four nuclear genes encoding chloroplast proteins during early development of Arabidopsis thaliana. This increase began soon after germination as cotyledons emerged from the seed coat; it occurred in total darkness and was not affected by external factors, such as gibberellins or light treatments used to stimulate germination. Three members of the cab gene family and the rbcS-1A gene exhibited this expression pattern. Because timing of the increase coincided with cotyledon emergence and because it occurred independently of external stimuli, we suggest that this increase represents developmental regulation of these genes. Further, 1.34 kilobases of the cab1 promoter was sufficient to confer this expression pattern on a reporter gene in transgenic Arabidopsis seedlings. The ability of the cab genes to respond to phytochrome preceded this developmental increase, showing that these two types of regulation are independent. Images PMID:1380166

  13. The phenotype of Arabidopsis thaliana det1 mutants suggest a role for cytokinins in greening

    SciTech Connect

    Chory, J.; Aguilar, N.; Peto, C.A.

    1990-01-01

    When grown in the absence of light, the det1 mutants of Arabidopsis thaliana develop characteristics of light-grown plants by morphological, cellular, and molecular criteria. Further, in light-grown plants, mutations in the DET1 gene affect cell-type-specific expression of light-regulated genes and the chloroplast developmental program. Here we show that the addition of exogenously added cytokinins (either 2-isopentenyl adenine, kinetin, or benzyladenine) to the growth medium of dark-germinated wild-type seedlings results in seedlings that resemble det1 mutants, instead of having the normal etiolated morphology. Like det1 mutants, these dark-grown seedlings now contain chloroplasts and have high levels of expression of genes that are normally light''-regulated. These results suggest an important role for cytokinins during greening of Arabidopsis, and may implicate cytokinin levels or an increased sensitivity to cytokinins as explanations for some of the observed phenotypes of det1 mutants.

  14. Analysis of mRNA translation states in Arabidopsis over the diurnal cycle by polysome microarray.

    PubMed

    Missra, Anamika; von Arnim, Albrecht G

    2014-01-01

    Gene regulation at the level of translation occurs in response to environmental perturbation and is increasingly recognized as a factor affecting plant development. Despite extensive knowledge of transcriptional control, very little is known about translational regulation of genes in response to the daily light/dark cycles. Here we describe the experimental layout designed to address how the translation states of genes change at various times during a diurnal cycle in Arabidopsis thaliana seedlings. We have adopted a strategy combining sucrose-gradient profiling of ribosomes and high-throughput microarray analysis of the ribosome-associated mRNA to investigate the translational landscape of the Arabidopsis genome. This is a powerful technique that can be easily extended to study translation regulation in different genetic backgrounds and under various environmental conditions. PMID:24792050

  15. Isolation of LUMINIDEPENDENS: a gene involved in the control of flowering time in Arabidopsis.

    PubMed Central

    Lee, I; Aukerman, M J; Gore, S L; Lohman, K N; Michaels, S D; Weaver, L M; John, M C; Feldmann, K A; Amasino, R M

    1994-01-01

    Plants have evolved the ability to regulate flowering in response to environmental signals such as temperature and photoperiod. The physiology and genetics of floral induction have been studied extensively, but the molecular mechanisms that underlie this process are poorly understood. To study this process, we isolated a gene, LUMINIDEPENDENS (LD), that is involved in the timing of flowering in Arabidopsis. Mutations in this gene render Arabidopsis late flowering and appear to affect light perception. The late-flowering phenotype of the ld mutation was partially suppressed by vernalization. Genomic and cDNA clones of the LD gene were characterized. The predicted amino acid sequence of the LD protein contains 953 residues and includes two putative bipartite nuclear localization signals and a glutamine-rich region. PMID:7907507

  16. FRIENDLY Regulates Mitochondrial Distribution, Fusion, and Quality Control in Arabidopsis1[W][OPEN

    PubMed Central

    El Zawily, Amr M.; Schwarzländer, Markus; Finkemeier, Iris; Johnston, Iain G.; Benamar, Abdelilah; Cao, Yongguo; Gissot, Clémence; Meyer, Andreas J.; Wilson, Ken; Datla, Raju; Macherel, David; Jones, Nick S.; Logan, David C.

    2014-01-01

    Mitochondria are defining components of most eukaryotes. However, higher plant mitochondria differ biochemically, morphologically, and dynamically from those in other eukaryotes. FRIENDLY, a member of the CLUSTERED MITOCHONDRIA superfamily, is conserved among eukaryotes and is required for correct distribution of mitochondria within the cell. We sought to understand how disruption of FRIENDLY function in Arabidopsis (Arabidopsis thaliana) leads to mitochondrial clustering and the effects of this aberrant chondriome on cell and whole-plant physiology. We present evidence for a role of FRIENDLY in mediating intermitochondrial association, which is a necessary prelude to mitochondrial fusion. We demonstrate that disruption of mitochondrial association, motility, and chondriome structure in friendly affects mitochondrial quality control and leads to mitochondrial stress, cell death, and strong growth phenotypes. PMID:25165398

  17. The Arabidopsis ABHD11 Mutant Accumulates Polar Lipids in Leaves as a Consequence of Absent Acylhydrolase Activity1[OPEN

    PubMed Central

    Vijayakumar, Anitha; Vijayaraj, Panneerselvam; Vijayakumar, Arun Kumar; Rajasekharan, Ram

    2016-01-01

    Alpha/beta hydrolase domain (ABHD)-containing proteins are structurally related with diverse catalytic activities. In various species, some ABHD proteins have been characterized and shown to play roles in lipid homeostasis. However, little is known about ABHD proteins in plants. Here, we characterized AT4G10030 (AtABHD11), an Arabidopsis (Arabidopsis thaliana) homolog of a human ABHD11 gene. In silico analyses of AtABHD11 revealed homology with other plant species with a conserved GXSXG lipid motif. Interestingly, Arabidopsis abhd11 mutant plants exhibited an enhanced growth rate compared with wild-type plants. Quantitative analyses of the total lipids showed that the mutant abhd11 has a high amount of phospholipid and galactolipid in Arabidopsis leaves. The overexpression of AtABHD11 in Escherichia coli led to a reduction in phospholipid levels. The bacterially expressed recombinant AtABHD11 hydrolyzed lyso(phospho)lipid and monoacylglycerol. Furthermore, using whole-genome microarray and real-time PCR analyses of abhd11 and wild-type plants, we noted the up-regulation of MGD1, -2, and -3 and DGD1. Together, these findings suggested that AtABHD11 is a lyso(phospho)lipase. The disruption of AtABHD11 caused the accumulation of the polar lipids in leaves, which in turn promoted a higher growth rate compared with wild-type plants. PMID:26589672

  18. Genetic and genomic analysis of Rhizoctonia solani interactions with Arabidopsis; evidence of resistance mediated through NADPH oxidases.

    PubMed

    Foley, Rhonda C; Gleason, Cynthia A; Anderson, Jonathan P; Hamann, Thorsten; Singh, Karam B

    2013-01-01

    Rhizoctonia solani is an important soil-borne necrotrophic fungal pathogen, with a broad host range and little effective resistance in crop plants. Arabidopsis is resistant to R. solani AG8 but susceptible to R. solani AG2-1. A screen of 36 Arabidopsis ecotypes and mutants affected in the auxin, camalexin, salicylic acid, abscisic acid and ethylene/jasmonic acid pathways did not reveal any variation in response to R. solani and demonstrated that resistance to AG8 was independent of these defense pathways. The Arabidopsis Affymetrix ATH1 Genome array was used to assess global gene expression changes in plants infected with AG8 and AG2-1 at seven days post-infection. While there was considerable overlap in the response, some gene families were differentially affected by AG8 or AG2-1 and included those involved in oxidative stress, cell wall associated proteins, transcription factors and heat shock protein genes. Since a substantial proportion of the gene expression changes were associated with oxidative stress responses, we analysed the role of NADPH oxidases in resistance. While single NADPH oxidase mutants had no effect, a NADPH oxidase double mutant atrbohf atrbohd resulted in an almost complete loss of resistance to AG8, suggesting that reactive oxidative species play an important role in Arabidopsis's resistance to R. solani. PMID:23451091

  19. Disruption of abscisic acid signaling constitutively activates Arabidopsis resistance to the necrotrophic fungus Plectosphaerella cucumerina.

    PubMed

    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

    2012-12-01

    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

  20. 17th International Conference on Arabidopsis Research

    SciTech Connect

    Judith Bender

    2006-07-01

    The 17th International Conference on Arabidopsis Research was held at the University of Madison, Wisconsin from June 27- July 2, 2006. ICAR-2006 included approximately 625 scientists from across the world. The scientific program was of excellent quality featuring 73 talks, including 30 from invited speakers. There were also 6 community-organized workshops (facilitated by conference staff) featuring additional talks on topics including ‘Submitting data to long-term repositories,’ ‘TAIR introductory workshop,’ ‘Web services and demonstration,’ ‘Public engagement: broadening the impact of your research,’ ‘Systems biology approaches to analysis of metabolic and regulatory networks of Arabidopsis,’ and ‘Mechanotransduction in Arabidopsis.’ Approximately 440 posters were presented in general topic areas including, among others, Development, Modeling/Other Systems, Energy, Environment, and Genetic/Epigenetic mechanisms. Graduate students, postdoctoral researchers, junior faculty, and underrepresented minorities made up a significant portion of the oral presentations thereby promoting the training of young scientists and facilitating important career development opportunities for speakers. Several poster sessions provided an opportunity for younger participants to freely meet with more established scientists. The North American Arabidopsis Steering Committee (NAASC) continued its outreach effort and again sponsored two special luncheons to encourage personal and professional development of young scientists and also underrepresented minorities. The ‘Emerging Scientists Luncheon’ featured 10 graduate students selected on the basis of scientific excellence of their submitted research abstracts. The ‘Minority Funding Luncheon,’ featured 8 awardees selected by the NAASC through a widely-publicized application process. This luncheon was established specifically to provide an opportunity for underrepresented minorities, and/or scientists from

  1. Cardiovascular risk of BRCA1/2 mutation carriers: A review.

    PubMed

    van Westerop, L L M; Arts-de Jong, M; Hoogerbrugge, N; de Hullu, J A; Maas, A H E M

    2016-09-01

    BRCA1/2 mutation carriers are at high risk of breast and ovarian cancer. The number of studies on non-cancer endpoints in BRCA1/2 mutation carriers is still limited. BRCA1/2 mutation carriers may be at higher cardiovascular risk due to early menopause after risk-reducing salpingo-oophorectomy and/or due to the potential cardiotoxic effects of breast cancer treatment (radiotherapy and chemotherapy). Moreover, BRCA genes have a role as a gatekeeper in cardiac function and structure, which may affect susceptibility to cardiac damage. Our goal is to review current knowledge of cardiovascular risk among BRCA1/2 mutation carriers. PMID:27451331

  2. Gene Expression in Plant Lipid Metabolism in Arabidopsis Seedlings

    PubMed Central

    Hsiao, An-Shan; Haslam, Richard P.; Michaelson, Louise V.; Liao, Pan; Napier, Johnathan A.; Chye, Mee-Len

    2014-01-01

    Events in plant lipid metabolism are important during seedling establishment. As it has not been experimentally verified whether lipid metabolism in 2- and 5-day-old Arabidopsis thaliana seedlings is diurnally-controlled, quantitative real-time PCR analysis was used to investigate the expression of target genes in acyl-lipid transfer, β-oxidation and triacylglycerol (TAG) synthesis and hydrolysis in wild-type Arabidopsis WS and Col-0. In both WS and Col-0, ACYL-COA-BINDING PROTEIN3 (ACBP3), DIACYLGLYCEROL ACYLTRANSFERASE1 (DGAT1) and DGAT3 showed diurnal control in 2- and 5-day-old seedlings. Also, COMATOSE (CTS) was diurnally regulated in 2-day-old seedlings and LONG-CHAIN ACYL-COA SYNTHETASE6 (LACS6) in 5-day-old seedlings in both WS and Col-0. Subsequently, the effect of CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) from the core clock system was examined using the cca1lhy mutant and CCA1-overexpressing (CCA1-OX) lines versus wild-type WS and Col-0, respectively. Results revealed differential gene expression in lipid metabolism between 2- and 5-day-old mutant and wild-type WS seedlings, as well as between CCA1-OX and wild-type Col-0. Of the ACBPs, ACBP3 displayed the most significant changes between cca1lhy and WS and between CCA1-OX and Col-0, consistent with previous reports that ACBP3 is greatly affected by light/dark cycling. Evidence of oil body retention in 4- and 5-day-old seedlings of the cca1lhy mutant in comparison to WS indicated the effect of cca1lhy on storage lipid reserve mobilization. Lipid profiling revealed differences in primary lipid metabolism, namely in TAG, fatty acid methyl ester and acyl-CoA contents amongst cca1lhy, CCA1-OX, and wild-type seedlings. Taken together, this study demonstrates that lipid metabolism is subject to diurnal regulation in the early stages of seedling development in Arabidopsis. PMID:25264899

  3. Arabidopsis: An Adequate Model for Dicot Root Systems?

    PubMed

    Zobel, Richard W

    2016-01-01

    The Arabidopsis root system is frequently considered to have only three classes of root: primary, lateral, and adventitious. Research with other plant species has suggested up to eight different developmental/functional classes of root for a given plant root system. If Arabidopsis has only three classes of root, it may not be an adequate model for eudicot plant root systems. Recent research, however, can be interpreted to suggest that pre-flowering Arabidopsis does have at least five (5) of these classes of root. This then suggests that Arabidopsis root research can be considered an adequate model for dicot plant root systems. PMID:26904040

  4. Distinct Phyllosphere Bacterial Communities on Arabidopsis Wax Mutant Leaves

    PubMed Central

    Reisberg, Eva E.; Hildebrandt, Ulrich; Riederer, Markus; Hentschel, Ute

    2013-01-01

    The phyllosphere of plants is inhabited by diverse microorganisms, however, the factors shaping their community composition are not fully elucidated. The plant cuticle represents the initial contact surface between microorganisms and the plant. We thus aimed to investigate whether mutations in the cuticular wax biosynthesis would affect the diversity of the phyllosphere microbiota. A set of four Arabidopsis thaliana eceriferum mutants (cer1, cer6, cer9, cer16) and their respective wild type (Landsberg erecta) were subjected to an outdoor growth period and analysed towards this purpose. The chemical distinctness of the mutant wax phenotypes was confirmed by gas chromatographic measurements. Next generation amplicon pyrosequencing of the bacterial communities showed distinct community patterns. This observation was supported by denaturing gradient gel electrophoresis experiments. Microbial community analyses revealed bacterial phylotypes that were ubiquitously present on all plant lines (termed “core” community) while others were positively or negatively affected by the wax mutant phenotype (termed “plant line-specific“ community). We conclude from this study that plant cuticular wax composition can affect the community composition of phyllosphere bacteria. PMID:24223831

  5. Interactions among Genes Regulating Ovule Development in Arabidopsis Thaliana

    PubMed Central

    Baker, S. C.; Robinson-Beers, K.; Villanueva, J. M.; Gaiser, J. C.; Gasser, C. S.

    1997-01-01

    The INNER NO OUTER (INO) and AINTEGUMENTA (ANT) genes are essential for ovule integument development in Arabidopsis thaliana. Ovules of ino mutants initiate two integument primordia, but the outer integument primordium forms on the opposite side of the ovule from the normal location and undergoes no further development. The inner integument appears to develop normally, resulting in erect, unitegmic ovules that resemble those of gymnosperms. ino plants are partially fertile and produce seeds with altered surface topography, demonstrating a lineage dependence in development of the testa. ant mutations affect initiation of both integuments. The strongest of five new ant alleles we have isolated produces ovules that lack integuments and fail to complete megasporogenesis. ant mutations also affect flower development, resulting in narrow petals and the absence of one or both lateral stamens. Characterization of double mutants between ant, ino and other mutations affecting ovule development has enabled the construction of a model for genetic control of ovule development. This model proposes parallel independent regulatory pathways for a number of aspects of this process, a dependence on the presence of an inner integument for development of the embryo sac, and the existence of additional genes regulating ovule development. PMID:9093862

  6. Arabidopsis PIZZA Has the Capacity to Acylate Brassinosteroids

    PubMed Central

    Schneider, Katja; Breuer, Christian; Kawamura, Ayako; Jikumaru, Yusuke; Hanada, Atsushi; Fujioka, Shozo; Ichikawa, Takanari; Kondou, Youichi; Matsui, Minami; Kamiya, Yuji; Yamaguchi, Shinjiro; Sugimoto, Keiko

    2012-01-01

    Brassinosteroids (BRs) affect a wide range of developmental processes in plants and compromised production or signalling of BRs causes severe growth defects. To identify new regulators of plant organ growth, we searched the Arabidopsis FOX (Full-length cDNA Over-eXpressor gene) collection for mutants with altered organ size and isolated two overexpression lines that display typical BR deficient dwarf phenotypes. The phenotype of these lines, caused by an overexpression of a putative acyltransferase gene PIZZA (PIZ), was partly rescued by supplying exogenous brassinolide (BL) and castasterone (CS), indicating that endogenous BR levels are rate-limiting for the growth of PIZ overexpression lines. Our transcript analysis further showed that PIZ overexpression leads to an elevated expression of genes involved in BR biosynthesis and a reduced expression of BR inactivating hydroxylases, a transcriptional response typical to low BR levels. Taking the advantage of relatively high endogenous BR accumulation in a mild bri1-301 background, we found that overexpression of PIZ results in moderately reduced levels of BL and CS and a strong reduction of typhasterol (TY) and 6-deoxocastasterone (6-deoxoCS), suggesting a role of PIZ in BR metabolism. We tested a set of potential substrates in vitro for heterologously expressed PIZ and confirmed its acyltransferase activity with BL, CS and TY. The PIZ gene is expressed in various tissues but as reported for other genes involved in BR metabolism, the loss-of-function mutants did not display obvious growth phenotypes under standard growth conditions. Together, our data suggest that PIZ can modify BRs by acylation and that these properties might help modulating endogenous BR levels in Arabidopsis. PMID:23071642

  7. Stress physiology functions of the Arabidopsis histidine kinase cytokinin receptors.

    PubMed

    Kumar, M Nagaraj; Verslues, Paul E

    2015-07-01

    Cytokinin signaling has complex effects on abiotic stress responses that remain to be fully elucidated. The Arabidopsis histidine kinases (AHKs), AHK2, AHK3 and CRE1 (cytokinin response1/AHK4) are the principle cytokinin receptors of Arabidopsis. Using a set of ahk mutants, we found dramatic differences in response to low water potential and salt stress among the AHKs. ahk3-3 mutants had increased root elongation after transfer to low water potential media. Conversely ahk2-2 was hypersensitive to salt stress in terms of root growth and fresh weight and accumulated higher than wild-type levels of proline specifically under salt stress. Strongly reduced proline accumulation in ahk double mutants after low water potential treatment indicated a more general role of cytokinin signaling in proline metabolism. Reduced P5CS1 (Δ(1) -pyrroline-5-carboxylate synthetase1) gene expression may have contributed to this reduced proline accumulation. Low water potential phenotypes of ahk mutants were not caused by altered abscisic acid (ABA) accumulation as all ahk mutants had wild-type ABA levels, despite the observation that ahk double mutants had reduced NCED3 (9-cis-epoxycartenoid dioxygenase3) expression when exposed to low water potential. No difference in osmoregulatory solute accumulation was detected in any of the ahk mutants indicating that they do not affect drought responsive osmotic adjustment. Overall, our examination of ahk mutants found specific phenotypes associated with AHK2 and AHK3 as well as a general function of cytokinin signaling in proline accumulation and low water potential induction of P5CS1 and NCED3 expression. These results show the stress physiology function of AHKs at a new level of detail. PMID:25263537

  8. In vitro activities of four xyloglucan endotransglycosylases from Arabidopsis

    NASA Technical Reports Server (NTRS)

    Campbell, P.; Braam, J.; McIntire, L. V. (Principal Investigator)

    1999-01-01

    Xyloglucan endotransglycosylases (XETs) are encoded by a gene family in Arabidopsis thaliana. These enzymes modify a major structural component of the plant cell wall, xyloglucan, and therefore may influence plant growth and development. We have produced four Arabidopsis XETs (TCH4, Meri-5, EXGT and XTR9) using the baculovirus/insect cell system and compared their biochemical activities. TCH4, as previously demonstrated, and the other three proteins are capable of carrying out transglycosylation of xyloglucans. The K(m) for XLLGol acceptor oligosaccharide is in the range of 20-40 microM for all the XETs except XTR9, which has a Km of 5 microM and is significantly inhibited by high levels of XLLGol. All four enzymes are most active between pH 6.0 and 6.5. TCH4 and XTR9 have temperature optima of 18 degrees C, whereas Meri-5 and EXGT are most active at 28 and 37 degrees C, respectively. Although the activity levels of three of the XETs are not influenced by the presence of fucose on the xyloglucan polymer, XTR9 has a clear preference for non-fucosylated xyloglucan polymer. The four XETs show a marked preference for XLLGol over either XXFGol or XXXGol as acceptor oligosaccharide. All four XETs are glycosylated; however, only the activities of TCH4 and Meri-5 are affected by the removal of the N-glycan with PNGase F. These four enzymes most likely function solely as transglycosylases because xyloglucan endoglucanase activity was not apparent. Subtle differences in biochemical activities may influence the physiological functions of the distinct XETs in vivo.

  9. DYn-2 Based Identification of Arabidopsis Sulfenomes.

    PubMed

    Akter, Salma; Huang, Jingjing; Bodra, Nandita; De Smet, Barbara; Wahni, Khadija; Rombaut, Debbie; Pauwels, Jarne; Gevaert, Kris; Carroll, Kate; Van Breusegem, Frank; Messens, Joris

    2015-05-01

    Identifying the sulfenylation state of stressed cells is emerging as a strategic approach for the detection of key reactive oxygen species signaling proteins. Here, we optimized an in vivo trapping method for cysteine sulfenic acids in hydrogen peroxide (H2O2) stressed plant cells using a dimedone based DYn-2 probe. We demonstrated that DYn-2 specifically detects sulfenylation events in an H2O2 dose- and time-dependent way. With mass spectrometry, we identified 226 sulfenylated proteins after H2O2 treatment of Arabidopsis cells, residing in the cytoplasm (123); plastid (68); mitochondria (14); nucleus (10); endoplasmic reticulum, Golgi and plasma membrane (7) and peroxisomes (4). Of these, 123 sulfenylated proteins have never been reported before to undergo cysteine oxidative post-translational modifications in plants. All in all, with this DYn-2 approach, we have identified new sulfenylated proteins, and gave a first glance on the locations of the sulfenomes of Arabidopsis thaliana. PMID:25693797

  10. DYn-2 Based Identification of Arabidopsis Sulfenomes*

    PubMed Central

    Akter, Salma; Huang, Jingjing; Bodra, Nandita; De Smet, Barbara; Wahni, Khadija; Rombaut, Debbie; Pauwels, Jarne; Gevaert, Kris; Carroll, Kate; Van Breusegem, Frank; Messens, Joris

    2015-01-01

    Identifying the sulfenylation state of stressed cells is emerging as a strategic approach for the detection of key reactive oxygen species signaling proteins. Here, we optimized an in vivo trapping method for cysteine sulfenic acids in hydrogen peroxide (H2O2) stressed plant cells using a dimedone based DYn-2 probe. We demonstrated that DYn-2 specifically detects sulfenylation events in an H2O2 dose- and time-dependent way. With mass spectrometry, we identified 226 sulfenylated proteins after H2O2 treatment of Arabidopsis cells, residing in the cytoplasm (123); plastid (68); mitochondria (14); nucleus (10); endoplasmic reticulum, Golgi and plasma membrane (7) and peroxisomes (4). Of these, 123 sulfenylated proteins have never been reported before to undergo cysteine oxidative post-translational modifications in plants. All in all, with this DYn-2 approach, we have identified new sulfenylated proteins, and gave a first glance on the locations of the sulfenomes of Arabidopsis thaliana. PMID:25693797

  11. Root gravitropism in maize and Arabidopsis

    NASA Technical Reports Server (NTRS)

    Evans, Michael L.

    1993-01-01

    Research during the period 1 March 1992 to 30 November 1993 focused on improvements in a video digitizer system designed to automate the recording of surface extension in plants responding to gravistimulation. The improvements included modification of software to allow detailed analysis of localized extension patterns in roots of Arabidopsis. We used the system to analyze the role of the postmitotic isodiametric growth zone (a region between the meristem and the elongation zone) in the response of maize roots to auxin, calcium, touch and gravity. We also used the system to analyze short-term auxin and gravitropic responses in mutants of Arabidopsis with reduced auxin sensitivity. In a related project, we studied the relationship between growth rate and surface electrical currents in roots by examining the effects of gravity and thigmostimulation on surface potentials in maize roots.

  12. From genome to function: the Arabidopsis aquaporins

    PubMed Central

    Quigley, Francoise; Rosenberg, Joshua M; Shachar-Hill, Yair; Bohnert, Hans J

    2002-01-01

    Background In the post-genomic era newly sequenced genomes can be used to deduce organismal functions from our knowledge of other systems. Here we apply this approach to analyzing the aquaporin gene family in Arabidopsis thaliana. The aquaporins are intrinsic membrane proteins that have been characterized as facilitators of water flux. Originally termed major intrinsic proteins (MIPs), they are now also known as water channels, glycerol facilitators and aqua-glyceroporins, yet recent data suggest that they facilitate the movement of other low-molecular-weight metabolites as well. Results The Arabidopsis genome contains 38 sequences with homology to aquaporin in four subfamilies, termed PIP, TIP, NIP and SIP. We have analyzed aquaporin family structure and expression using the A. thaliana genome sequence, and introduce a new NMR approach for the purpose of analyzing water movement in plant roots in vivo. Conclusions Our preliminary data indicate a strongly transcellular component for the flux of water in roots. PMID:11806824

  13. The Arabidopsis Stress Responsive Gene Database

    PubMed Central

    Borkotoky, Subhomoi; Saravanan, Vijayakumar; Jaiswal, Amit; Das, Bipul; Selvaraj, Suresh; Murali, Ayaluru; Lakshmi, P. T. V.

    2013-01-01

    Plants in nature may face a wide range of favorable or unfavorable biotic and abiotic factors during their life cycle. Any of these factors may cause stress in plants; therefore, they have to be more adaptable to stressful environments and must acquire greater response to different stresses. The objective of this study is to retrieve and arrange data from the literature in a standardized electronic format for the development of information resources on potential stress responsive genes in Arabidopsis thaliana. This provides a powerful mean for manipulation, comparison, search, and retrieval of records describing the nature of various stress responsive genes in Arabidopsis thaliana. The database is based exclusively on published stress tolerance genes associated with plants. PMID:23573074

  14. Flavonoid-specific staining of Arabidopsis thaliana.

    PubMed

    Sheahan, J J; Rechnitz, G A

    1992-12-01

    Crop yields may be threatened by increases in UV-B radiation resulting from depletion of the ozone layer. In higher plants, the presence of flavonols provides a protective mechanism, and we report a novel staining procedure for the visualization of such protectants in plant tissue. It is shown that the proposed technique provides sensitive and specific fluorescence of flavonoids in chlorophyll-bleached tissue of Arabidopsis thaliana. PMID:1282347

  15. Analyzing Synthetic Promoters Using Arabidopsis Protoplasts.

    PubMed

    Stracke, Ralf; Thiedig, Katharina; Kuhlmann, Melanie; Weisshaar, Bernd

    2016-01-01

    This chapter describes a transient protoplast co-transfection method that can be used to quantitatively study in vivo the activity and function of promoters and promoter elements (reporters), and their induction or repression by transcription factors (effectors), stresses, hormones, or metabolites. A detailed protocol for carrying out transient co-transfection assays with Arabidopsis At7 protoplasts and calculating the promoter activity is provided. PMID:27557761

  16. Fluorescence-Activated Nucleolus Sorting in Arabidopsis.

    PubMed

    Pontvianne, Frédéric; Boyer-Clavel, Myriam; Sáez-Vásquez, Julio

    2016-01-01

    Nucleolar isolation allows exhaustive characterization of the nucleolar content. Centrifugation-based protocols are not adapted to isolation of nucleoli directly from a plant tissue because of copurification of cellular debris. We describe here a method that allows the purification of nucleoli using fluorescent-activated cell sorting from Arabidopsis thaliana leaves. This approach requires the expression of a specific nucleolar protein such as fibrillarin fused to green fluorescent protein in planta. PMID:27576720

  17. Dehalogenimonas spp. can Reductively Dehalogenate High Concentrations of 1,2-Dichloroethane, 1,2-Dichloropropane, and 1,1,2-Trichloroethane

    PubMed Central

    2012-01-01

    The contaminant concentrations over which type strains of the species Dehalogenimonas alkenigignens and Dehalogenimonas lykanthroporepellens were able to reductively dechlorinate 1,2-dichloroethane (1,2-DCA), 1,2-dichloropropane (1,2-DCP), and 1,1,2-trichloroethane (1,1,2-TCA) were evaluated. Although initially isolated from an environment with much lower halogenated solvent concentrations, D. alkenigignens IP3-3T was found to reductively dehalogenate chlorinated alkanes at concentrations comparable to D. lykanthroporepellens BL-DC-9T. Both species dechlorinated 1,2-DCA, 1,2-DCP, and 1,1,2-TCA present at initial concentrations at least as high as 8.7, 4.0, and 3.5 mM, respectively. The ability of Dehalogenimonas spp. to carry out anaerobic reductive dechlorination even in the presence of high concentrations of chlorinated aliphatic alkanes has important implications for remediation of contaminated soil and groundwater. PMID:23046725

  18. Dehalogenimonas spp. can Reductively Dehalogenate High Concentrations of 1,2-Dichloroethane, 1,2-Dichloropropane, and 1,1,2-Trichloroethane.

    PubMed

    Maness, Andrew D; Bowman, Kimberly S; Yan, Jun; Rainey, Fred A; Moe, William M

    2012-01-01

    The contaminant concentrations over which type strains of the species Dehalogenimonas alkenigignens and Dehalogenimonas lykanthroporepellens were able to reductively dechlorinate 1,2-dichloroethane (1,2-DCA), 1,2-dichloropropane (1,2-DCP), and 1,1,2-trichloroethane (1,1,2-TCA) were evaluated. Although initially isolated from an environment with much lower halogenated solvent concentrations, D. alkenigignens IP3-3T was found to reductively dehalogenate chlorinated alkanes at concentrations comparable to D. lykanthroporepellens BL-DC-9T. Both species dechlorinated 1,2-DCA, 1,2-DCP, and 1,1,2-TCA present at initial concentrations at least as high as 8.7, 4.0, and 3.5 mM, respectively. The ability of Dehalogenimonas spp. to carry out anaerobic reductive dechlorination even in the presence of high concentrations of chlorinated aliphatic alkanes has important implications for remediation of contaminated soil and groundwater. PMID:23046725

  19. Regulatory Proteolysis in Arabidopsis-Pathogen Interactions

    PubMed Central

    Pogány, Miklós; Dankó, Tamás; Kámán-Tóth, Evelin; Schwarczinger, Ildikó; Bozsó, Zoltán

    2015-01-01

    Approximately two and a half percent of protein coding genes in Arabidopsis encode enzymes with known or putative proteolytic activity. Proteases possess not only common housekeeping functions by recycling nonfunctional proteins. By irreversibly cleaving other proteins, they regulate crucial developmental processes and control responses to environmental changes. Regulatory proteolysis is also indispensable in interactions between plants and their microbial pathogens. Proteolytic cleavage is simultaneously used both by plant cells, to recognize and inactivate invading pathogens, and by microbes, to overcome the immune system of the plant and successfully colonize host cells. In this review, we present available results on the group of proteases in the model plant Arabidopsis thaliana whose functions in microbial pathogenesis were confirmed. Pathogen-derived proteolytic factors are also discussed when they are involved in the cleavage of host metabolites. Considering the wealth of review papers available in the field of the ubiquitin-26S proteasome system results on the ubiquitin cascade are not presented. Arabidopsis and its pathogens are conferred with abundant sets of proteases. This review compiles a list of those that are apparently involved in an interaction between the plant and its pathogens, also presenting their molecular partners when available. PMID:26404238

  20. Phosphorylation of plastoglobular proteins in Arabidopsis thaliana.

    PubMed

    Lohscheider, Jens N; Friso, Giulia; van Wijk, Klaas J

    2016-06-01

    Plastoglobules (PGs) are plastid lipid-protein particles with a small specialized proteome and metabolome. Among the 30 core PG proteins are six proteins of the ancient ABC1 atypical kinase (ABC1K) family and their locations in an Arabidopsis mRNA-based co-expression network suggested central regulatory roles. To identify candidate ABC1K targets and a possible ABC1K hierarchical phosphorylation network within the chloroplast PG proteome, we searched Arabidopsis phosphoproteomics data from publicly available sources. Evaluation of underlying spectra and/or associated information was challenging for a variety of reasons, but supported pSer sites and a few pThr sites in nine PG proteins, including five FIBRILLINS. PG phosphorylation motifs are discussed in the context of possible responsible kinases. The challenges of collection and evaluation of published Arabidopsis phosphorylation data are discussed, illustrating the importance of deposition of all mass spectrometry data in well-organized repositories such as PRIDE and ProteomeXchange. This study provides a starting point for experimental testing of phosho-sites in PG proteins and also suggests that phosphoproteomics studies specifically designed toward the PG proteome and its ABC1K are needed to understand phosphorylation networks in these specialized particles. PMID:26962209

  1. Phosphorylation of plastoglobular proteins in Arabidopsis thaliana

    PubMed Central

    Lohscheider, Jens N.; Friso, Giulia; van Wijk, Klaas J.

    2016-01-01

    Plastoglobules (PGs) are plastid lipid–protein particles with a small specialized proteome and metabolome. Among the 30 core PG proteins are six proteins of the ancient ABC1 atypical kinase (ABC1K) family and their locations in an Arabidopsis mRNA-based co-expression network suggested central regulatory roles. To identify candidate ABC1K targets and a possible ABC1K hierarchical phosphorylation network within the chloroplast PG proteome, we searched Arabidopsis phosphoproteomics data from publicly available sources. Evaluation of underlying spectra and/or associated information was challenging for a variety of reasons, but supported pSer sites and a few pThr sites in nine PG proteins, including five FIBRILLINS. PG phosphorylation motifs are discussed in the context of possible responsible kinases. The challenges of collection and evaluation of published Arabidopsis phosphorylation data are discussed, illustrating the importance of deposition of all mass spectrometry data in well-organized repositories such as PRIDE and ProteomeXchange. This study provides a starting point for experimental testing of phosho-sites in PG proteins and also suggests that phosphoproteomics studies specifically designed toward the PG proteome and its ABC1K are needed to understand phosphorylation networks in these specialized particles. PMID:26962209

  2. Computational identification of 69 retroposons in Arabidopsis.

    PubMed

    Zhang, Yujun; Wu, Yongrui; Liu, Yilei; Han, Bin

    2005-06-01

    Retroposition is a shot-gun strategy of the genome to achieve evolutionary diversities by mixing and matching coding sequences with novel regulatory elements. We have identified 69 retroposons in the Arabidopsis (Arabidopsis thaliana) genome by a computational approach. Most of them were derivatives of mature mRNAs, and 20 genes contained relics of the reverse transcription process, such as truncations, deletions, and extra sequence additions. Of them, 22 are processed pseudogenes, and 52 genes are likely to be actively transcribed, especially in tissues from apical meristems (roots and flowers). Functional compositions of these retroposon parental genes imply that not the mRNA itself but its expression in gamete cells defines a suitable template for retroposition. The presence/absence patterns of retroposons can be used as cladistic markers for biogeographic research. Effects of human and the Mediterranean Pleistocene refugia in Arabidopsis biogeographic distributions were revealed based on two recent retroposons (At1g61410 and At5g52090). An evolutionary rate of new gene creation by retroposition was calculated as 0.6 genes per million years. Retroposons can also be used as molecular fossils of the parental gene expressions in ancient time. Extensions of 3' untranslated regions for those expressed parental genes are revealed as a possible trend of plant transcriptome evolution. In addition, we reported the first plant functional chimeric gene that adapts to intercompartmental transport by capturing two additional exons after retroposition. PMID:15923328

  3. Analysis of the Arabidopsis Mitochondrial Proteome1

    PubMed Central

    Millar, A. Harvey; Sweetlove, Lee J.; Giegé, Philippe; Leaver, Christopher J.

    2001-01-01

    The complete set of nuclear genes that encode proteins targeted to mitochondria in plants is currently undefined and thus the full range of mitochondrial functions in plants is unknown. Analysis of two-dimensional gel separations of Arabidopsis cell culture mitochondrial protein revealed approximately 100 abundant proteins and 250 low-abundance proteins. Comparison of subfractions of mitochondrial protein on two-dimensional gels provided information on the soluble, membrane, or integral membrane locations of this protein set. A total of 170 protein spots were excised, trypsin-digested, and matrix-assisted laser desorption ionization/time of flight mass spectrometry spectra obtained. Using this dataset, 91 of the proteins were identified by searching translated Arabidopsis genomic databases. Of this set, 81 have defined functions based on sequence comparison. These functions include respiratory electron transport, tricarboxylic acid cycle metabolism, amino acid metabolism, protein import, processing, and assembly, transcription, membrane transport, and antioxidant defense. A total of 10 spectra were matched to Arabidopsis putative open reading frames for which no specific function has been determined. A total of 64 spectra did not match to an identified open reading frame. Analysis of full-length putative protein sequences using bioinformatic tools to predict subcellular targeting (TargetP, Psort, and MitoProt) revealed significant variation in predictions, and also a lack of mitochondrial targeting prediction for several characterized mitochondrial proteins. PMID:11743115

  4. Multiscale digital Arabidopsis predicts individual organ and whole-organism growth

    PubMed Central

    Chew, Yin Hoon; Wenden, Bénédicte; Flis, Anna; Mengin, Virginie; Taylor, Jasper; Davey, Christopher L.; Tindal, Christopher; Thomas, Howard; Ougham, Helen J.; de Reffye, Philippe; Stitt, Mark; Williams, Mathew; Muetzelfeldt, Robert; Halliday, Karen J.; Millar, Andrew J.

    2014-01-01

    Understanding how dynamic molecular networks affect whole-organism physiology, analogous to mapping genotype to phenotype, remains a key challenge in biology. Quantitative models that represent processes at multiple scales and link understanding from several research domains can help to tackle this problem. Such integrated models are more common in crop science and ecophysiology than in the research communities that elucidate molecular networks. Several laboratories have modeled particular aspects of growth in Arabidopsis thaliana, but it was unclear whether these existing models could productively be combined. We test this approach by constructing a multiscale model of Arabidopsis rosette growth. Four existing models were integrated with minimal parameter modification (leaf water content and one flowering parameter used measured data). The resulting framework model links genetic regulation and biochemical dynamics to events at the organ and whole-plant levels, helping to understand the combined effects of endogenous and environmental regulators on Arabidopsis growth. The framework model was validated and tested with metabolic, physiological, and biomass data from two laboratories, for five photoperiods, three accessions, and a transgenic line, highlighting the plasticity of plant growth strategies. The model was extended to include stochastic development. Model simulations gave insight into the developmental control of leaf production and provided a quantitative explanation for the pleiotropic developmental phenotype caused by overexpression of miR156, which was an open question. Modular, multiscale models, assembling knowledge from systems biology to ecophysiology, will help to understand and to engineer plant behavior from the genome to the field. PMID:25197087

  5. Impact of natural genetic variation on the transcriptome of autotetraploid Arabidopsis thaliana

    PubMed Central

    Yu, Zheng; Haberer, Georg; Matthes, Michaela; Rattei, Thomas; Mayer, Klaus F. X.; Gierl, Alfons; Torres-Ruiz, Ramon A.

    2010-01-01

    Polyploidy, the presence of more than two complete sets of chromosomes in an organism, has significantly shaped the genomes of angiosperms during evolution. Two forms of polyploidy are often considered: allopolyploidy, which originates from interspecies hybrids, and autopolyploidy, which originates from intraspecies genome duplication events. Besides affecting genome organization, polyploidy generates other genetic effects. Synthetic allopolyploid plants exhibit considerable transcriptome alterations, part of which are likely caused by the reunion of previously diverged regulatory hierarchies. In contrast, autopolyploids have relatively uniform genomes, suggesting lower alteration of gene expression. To evaluate the impact of intraspecies genome duplication on the transcriptome, we generated a series of unique Arabidopsis thaliana autotetraploids by using different ecotypes. A. thaliana autotetraploids show transcriptome alterations that strongly depend on their parental genome composition and include changed expression of both new genes and gene groups previously described from allopolyploid Arabidopsis. Alterations in gene expression are stable, nonstochastic, developmentally specific, and associated with changes in DNA methylation. We propose that Arabidopsis possesses an inherent and heritable ability to sense and respond to elevated, yet balanced chromosome numbers. The impact of natural variation on alteration of autotetraploid gene expression stresses its potential importance in the evolution and breeding of plants. PMID:20876110

  6. Functional Analysis of the Arabidopsis TETRASPANIN Gene Family in Plant Growth and Development1[OPEN

    PubMed Central

    Wang, Feng; Muto, Antonella; Van de Velde, Jan; Neyt, Pia; Himanen, Kristiina; Vandepoele, Klaas; Van Lijsebettens, Mieke

    2015-01-01

    TETRASPANIN (TET) genes encode conserved integral membrane proteins that are known in animals to function in cellular communication during gamete fusion, immunity reaction, and pathogen recognition. In plants, functional information is limited to one of the 17 members of the Arabidopsis (Arabidopsis thaliana) TET gene family and to expression data in reproductive stages. Here, the promoter activity of all 17 Arabidopsis TET genes was investigated by pAtTET::NUCLEAR LOCALIZATION SIGNAL-GREEN FLUORESCENT PROTEIN/β-GLUCURONIDASE reporter lines throughout the life cycle, which predicted functional divergence in the paralogous genes per clade. However, partial overlap was observed for many TET genes across the clades, correlating with few phenotypes in single mutants and, therefore, requiring double mutant combinations for functional investigation. Mutational analysis showed a role for TET13 in primary root growth and lateral root development and redundant roles for TET5 and TET6 in leaf and root growth through negative regulation of cell proliferation. Strikingly, a number of TET genes were expressed in embryonic and seedling progenitor cells and remained expressed until the differentiation state in the mature plant, suggesting a dynamic function over developmental stages. The cis-regulatory elements together with transcription factor-binding data provided molecular insight into the sites, conditions, and perturbations that affect TET gene expression and positioned the TET genes in different molecular pathways; the data represent a hypothesis-generating resource for further functional analyses. PMID:26417009

  7. An improved method for the visualization of conductive vessels in Arabidopsis thaliana inflorescence stems

    PubMed Central

    Jupa, Radek; Didi, Vojtěch; Hejátko, Jan; Gloser, Vít

    2015-01-01

    Dye perfusion is commonly used for the identification of conductive elements important for the study of xylem development as well as precise hydraulic estimations. The tiny size of inflorescence stems, the small amount of vessels in close arrangement, and high hydraulic resistivity delimit the use of the method for quantification of the water conductivity of Arabidopsis thaliana, one of the recently most extensively used plant models. Here, we present an extensive adjustment to the method in order to reliably identify individual functional (conductive) vessels. Segments of inflorescence stems were sealed in silicone tubes to prevent damage and perfused with a dye solution. Our results showed that dyes often used for staining functional xylem elements (safranin, fuchsine, toluidine blue) failed with Arabidopsis. In contrast, Fluorescent Brightener 28 dye solution perfused through segments stained secondary cell walls of functional vessels, which were clearly distinguishable in native cross sections. When compared to identification based on the degree of development of secondary cell walls, identification with the help of dye perfusion revealed a significantly lower number of functional vessels and values of theoretical hydraulic conductivity. We found that lignified but not yet functional vessels form a substantial portion of the xylem in apical and basal segments of Arabidopsis and, thus, significantly affect the analyzed functional parameters of xylem. The presented methodology enables reliable identification of individual functional vessels, allowing thus estimations of hydraulic conductivities to be improved, size distributions and vessel diameters to be refined, and data variability generally to be reduced. PMID:25914701

  8. An improved method for the visualization of conductive vessels in Arabidopsis thaliana inflorescence stems.

    PubMed

    Jupa, Radek; Didi, Vojtěch; Hejátko, Jan; Gloser, Vít

    2015-01-01

    Dye perfusion is commonly used for the identification of conductive elements important for the study of xylem development as well as precise hydraulic estimations. The tiny size of inflorescence stems, the small amount of vessels in close arrangement, and high hydraulic resistivity delimit the use of the method for quantification of the water conductivity of Arabidopsis thaliana, one of the recently most extensively used plant models. Here, we present an extensive adjustment to the method in order to reliably identify individual functional (conductive) vessels. Segments of inflorescence stems were sealed in silicone tubes to prevent damage and perfused with a dye solution. Our results showed that dyes often used for staining functional xylem elements (safranin, fuchsine, toluidine blue) failed with Arabidopsis. In contrast, Fluorescent Brightener 28 dye solution perfused through segments stained secondary cell walls of functional vessels, which were clearly distinguishable in native cross sections. When compared to identification based on the degree of development of secondary cell walls, identification with the help of dye perfusion revealed a significantly lower number of functional vessels and values of theoretical hydraulic conductivity. We found that lignified but not yet functional vessels form a substantial portion of the xylem in apical and basal segments of Arabidopsis and, thus, significantly affect the analyzed functional parameters of xylem. The presented methodology enables reliable identification of individual functional vessels, allowing thus estimations of hydraulic conductivities to be improved, size distributions and vessel diameters to be refined, and data variability generally to be reduced. PMID:25914701

  9. Functional Analysis of Sporophytic Transcripts Repressed by the Female Gametophyte in the Ovule of Arabidopsis thaliana

    PubMed Central

    Armenta-Medina, Alma; Huanca-Mamani, Wilson; Sanchez-León, Nidia; Rodríguez-Arévalo, Isaac; Vielle-Calzada, Jean-Philippe

    2013-01-01

    To investigate the genetic and molecular regulation that the female gametophyte could exert over neighboring sporophytic regions of the ovule, we performed a quantitative comparison of global expression in wild-type and nozzle/sporocyteless (spl) ovules of Arabidopsis thaliana (Arabidopsis), using Massively Parallel Signature Sequencing (MPSS). This comparison resulted in 1517 genes showing at least 3-fold increased expression in ovules lacking a female gametophyte, including those encoding 89 transcription factors, 50 kinases, 25 proteins containing a RNA-recognition motif (RRM), and 20 WD40 repeat proteins. We confirmed that eleven of these genes are either preferentially expressed or exclusive of spl ovules lacking a female gametophyte as compared to wild-type, and showed that six are also upregulated in determinant infertile1 (dif1), a meiotic mutant affected in a REC8-like cohesin that is also devoided of female gametophytes. The sporophytic misexpression of IOREMPTE, a WD40/transducin repeat gene that is preferentially expressed in the L1 layer of spl ovules, caused the arrest of female gametogenesis after differentiation of a functional megaspore. Our results show that in Arabidopsis, the sporophytic-gametophytic cross talk includes a negative regulation of the female gametophyte over specific genes that are detrimental for its growth and development, demonstrating its potential to exert a repressive control over neighboring regions in the ovule. PMID:24194852

  10. Functional Analysis of the Arabidopsis TETRASPANIN Gene Family in Plant Growth and Development.

    PubMed

    Wang, Feng; Muto, Antonella; Van de Velde, Jan; Neyt, Pia; Himanen, Kristiina; Vandepoele, Klaas; Van Lijsebettens, Mieke

    2015-11-01

    TETRASPANIN (TET) genes encode conserved integral membrane proteins that are known in animals to function in cellular communication during gamete fusion, immunity reaction, and pathogen recognition. In plants, functional information is limited to one of the 17 members of the Arabidopsis (Arabidopsis thaliana) TET gene family and to expression data in reproductive stages. Here, the promoter activity of all 17 Arabidopsis TET genes was investigated by pAtTET::NUCLEAR LOCALIZATION SIGNAL-GREEN FLUORESCENT PROTEIN/β-GLUCURONIDASE reporter lines throughout the life cycle, which predicted functional divergence in the paralogous genes per clade. However, partial overlap was observed for many TET genes across the clades, correlating with few phenotypes in single mutants and, therefore, requiring double mutant combinations for functional investigation. Mutational analysis showed a role for TET13 in primary root growth and lateral root development and redundant roles for TET5 and TET6 in leaf and root growth through negative regulation of cell proliferation. Strikingly, a number of TET genes were expressed in embryonic and seedling progenitor cells and remained expressed until the differentiation state in the mature plant, suggesting a dynamic function over developmental stages. The cis-regulatory elements together with transcription factor-binding data provided molecular insight into the sites, conditions, and perturbations that affect TET gene expression and positioned the TET genes in different molecular pathways; the data represent a hypothesis-generating resource for further functional analyses. PMID:26417009

  11. Functional analysis of sporophytic transcripts repressed by the female gametophyte in the ovule of Arabidopsis thaliana.

    PubMed

    Armenta-Medina, Alma; Huanca-Mamani, Wilson; Sanchez-León, Nidia; Rodríguez-Arévalo, Isaac; Vielle-Calzada, Jean-Philippe

    2013-01-01

    To investigate the genetic and molecular regulation that the female gametophyte could exert over neighboring sporophytic regions of the ovule, we performed a quantitative comparison of global expression in wild-type and nozzle/sporocyteless (spl) ovules of Arabidopsis thaliana (Arabidopsis), using Massively Parallel Signature Sequencing (MPSS). This comparison resulted in 1517 genes showing at least 3-fold increased expression in ovules lacking a female gametophyte, including those encoding 89 transcription factors, 50 kinases, 25 proteins containing a RNA-recognition motif (RRM), and 20 WD40 repeat proteins. We confirmed that eleven of these genes are either preferentially expressed or exclusive of spl ovules lacking a female gametophyte as compared to wild-type, and showed that six are also upregulated in determinant infertile1 (dif1), a meiotic mutant affected in a REC8-like cohesin that is also devoided of female gametophytes. The sporophytic misexpression of IOREMPTE, a WD40/transducin repeat gene that is preferentially expressed in the L1 layer of spl ovules, caused the arrest of female gametogenesis after differentiation of a functional megaspore. Our results show that in Arabidopsis, the sporophytic-gametophytic cross talk includes a negative regulation of the female gametophyte over specific genes that are detrimental for its growth and development, demonstrating its potential to exert a repressive control over neighboring regions in the ovule. PMID:24194852

  12. Strigolactone acts downstream of auxin to regulate bud outgrowth in pea and Arabidopsis.

    PubMed

    Brewer, Philip B; Dun, Elizabeth A; Ferguson, Brett J; Rameau, Catherine; Beveridge, Christine A

    2009-05-01

    During the last century, two key hypotheses have been proposed to explain apical dominance in plants: auxin promotes the production of a second messenger that moves up into buds to repress their outgrowth, and auxin saturation in the stem inhibits auxin transport from buds, thereby inhibiting bud outgrowth. The recent discovery of strigolactone as the novel shoot-branching inhibitor allowed us to test its mode of action in relation to these hypotheses. We found that exogenously applied strigolactone inhibited bud outgrowth in pea (Pisum sativum) even when auxin was depleted after decapitation. We also found that strigolactone application reduced branching in Arabidopsis (Arabidopsis thaliana) auxin response mutants, suggesting that auxin may act through strigolactones to facilitate apical dominance. Moreover, strigolactone application to tiny buds of mutant or decapitated pea plants rapidly stopped outgrowth, in contrast to applying N-1-naphthylphthalamic acid (NPA), an auxin transport inhibitor, which significantly slowed growth only after several days. Whereas strigolactone or NPA applied to growing buds reduced bud length, only NPA blocked auxin transport in the bud. Wild-type and strigolactone biosynthesis mutant pea and Arabidopsis shoots were capable of instantly transporting additional amounts of auxin in excess of endogenous levels, contrary to predictions of auxin transport models. These data suggest that strigolactone does not act primarily by affecting auxin transport from buds. Rather, the primary repressor of bud outgrowth appears to be the auxin-dependent production of strigolactones. PMID:19321710

  13. Multiscale digital Arabidopsis predicts individual organ and whole-organism growth.

    PubMed

    Chew, Yin Hoon; Wenden, Bénédicte; Flis, Anna; Mengin, Virginie; Taylor, Jasper; Davey, Christopher L; Tindal, Christopher; Thomas, Howard; Ougham, Helen J; de Reffye, Philippe; Stitt, Mark; Williams, Mathew; Muetzelfeldt, Robert; Halliday, Karen J; Millar, Andrew J

    2014-09-30

    Understanding how dynamic molecular networks affect whole-organism physiology, analogous to mapping genotype to phenotype, remains a key challenge in biology. Quantitative models that represent processes at multiple scales and link understanding from several research domains can help to tackle this problem. Such integrated models are more common in crop science and ecophysiology than in the research communities that elucidate molecular networks. Several laboratories have modeled particular aspects of growth in Arabidopsis thaliana, but it was unclear whether these existing models could productively be combined. We test this approach by constructing a multiscale model of Arabidopsis rosette growth. Four existing models were integrated with minimal parameter modification (leaf water content and one flowering parameter used measured data). The resulting framework model links genetic regulation and biochemical dynamics to events at the organ and whole-plant levels, helping to understand the combined effects of endogenous and environmental regulators on Arabidopsis growth. The framework model was validated and tested with metabolic, physiological, and biomass data from two laboratories, for five photoperiods, three accessions, and a transgenic line, highlighting the plasticity of plant growth strategies. The model was extended to include stochastic development. Model simulations gave insight into the developmental control of leaf production and provided a quantitative explanation for the pleiotropic developmental phenotype caused by overexpression of miR156, which was an open question. Modular, multiscale models, assembling knowledge from systems biology to ecophysiology, will help to understand and to engineer plant behavior from the genome to the field. PMID:25197087

  14. Changes in biosynthesis and metabolism of glutathione upon ochratoxin A stress in Arabidopsis thaliana.

    PubMed

    Wang, Yan; Zhao, Weiwei; Hao, Junran; Xu, Wentao; Luo, Yunbo; Wu, Weihong; Yang, Zhuojun; Liang, Zhihong; Huang, Kunlun

    2014-06-01

    Ochratoxin A (OTA) is one of the most toxic mycotoxins, which is toxic to plants and simulates oxidative stress. Glutathione is an important antioxidant in plants and is closely associated with detoxification in cells. We have previously shown that OTA exposure induces obvious expression differences in genes associated with glutathione metabolism. To characterize glutathione metabolism and understand its role in OTA phytotoxicity, we observed the accumulation of GSH in the detached leaves of Arabidopsis thaliana under OTA treatment. OTA stimulated a defense response through enhancing glutathione-S-transferase, glutathione peroxidase, glutathione reductase activities, and the transcript levels of these enzymes were increased to maintain the total glutathione content. Moreover, the level of oxidized glutathione (GSSG) was increased and the ascorbate-glutathione cycle fluctuated in response to OTA. The depletion of glutathione using buthionine sulfoximine (BSO, inhibitor of glutamate-cysteine ligase) had no profound effect on OTA toxicity, as glutathione was regenerated through the ascorbate-glutathione cycle to maintain the total glutathione content. The ROS, MDA and GSH accumulation was significantly affected in the mutant gsh1, gr1 and gpx2 after treatment with OTA, which indicated that glutathione metabolism is directly involved in the oxidative stress response of Arabidopsis thaliana subjected to OTA. In conclusion, date demonstrate that glutathione-associated metabolism is closely related with OTA stress and glutathione play a role in resistance of Arabidopsis subjected to OTA. PMID:24662377

  15. Genetic analysis of the gravitropic set-point angle in lateral roots of Arabidopsis

    NASA Technical Reports Server (NTRS)

    Mullen, J. L.; Hangarter, R. P.; Kiss, J. Z. (Principal Investigator)

    2003-01-01

    Research on gravity responses in plants has mostly focused on primary roots and shoots, which typically orient to a vertical orientation. However, the distribution of lateral organs and their characteristically non-vertical growth orientation are critical for the determination of plant form. For example, in Arabidopsis, when lateral roots emerge from the primary root, they grow at a nearly horizontal orientation. As they elongate, the roots slowly curve until they eventually reach a vertical orientation. The regulation of this lateral root orientation is an important component affecting overall root system architecture. We found that this change in orientation is not simply due to the onset of gravitropic competence, as non-vertical lateral roots are capable of both positive and negative gravitropism. Thus, the horizontal growth of new lateral roots appears to be determined by what is called the gravitropic set-point angle (GSA). This developmental control of the GSA of lateral roots in Arabidopsis provides a useful system for investigating the components involved in regulating gravitropic responses. Using this system, we have identified several Arabidopsis mutants that have altered lateral root orientations but maintain normal primary root orientation. c2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

  16. The Calcium Ion Is a Second Messenger in the Nitrate Signaling Pathway of Arabidopsis.

    PubMed

    Riveras, Eleodoro; Alvarez, José M; Vidal, Elena A; Oses, Carolina; Vega, Andrea; Gutiérrez, Rodrigo A

    2015-10-01

    Understanding how plants sense and respond to changes in nitrogen availability is the first step toward developing strategies for biotechnological applications, such as improvement of nitrogen use efficiency. However, components involved in nitrogen signaling pathways remain poorly characterized. Calcium is a second messenger in signal transduction pathways in plants, and it has been indirectly implicated in nitrate responses. Using aequorin reporter plants, we show that nitrate treatments transiently increase cytoplasmic Ca(2+) concentration. We found that nitrate also induces cytoplasmic concentration of inositol 1,4,5-trisphosphate. Increases in inositol 1,4,5-trisphosphate and cytoplasmic Ca(2+) levels in response to nitrate treatments were blocked by U73122, a pharmacological inhibitor of phospholipase C, but not by the nonfunctional phospholipase C inhibitor analog U73343. In addition, increase in cytoplasmic Ca(2+) levels in response to nitrate treatments was abolished in mutants of the nitrate transceptor NITRATE TRANSPORTER1.1/Arabidopsis (Arabidopsis thaliana) NITRATE TRANSPORTER1 PEPTIDE TRANSPORTER FAMILY6.3. Gene expression of nitrate-responsive genes was severely affected by pretreatments with Ca(2+) channel blockers or phospholipase C inhibitors. These results indicate that Ca(2+) acts as a second messenger in the nitrate signaling pathway of Arabidopsis. Our results suggest a model where NRT1.1/AtNPF6.3 and a phospholipase C activity mediate the increase of Ca(2+) in response to nitrate required for changes in expression of prototypical nitrate-responsive genes. PMID:26304850

  17. FACTORS AFFECTING PHYTOPLANKTON DISTRIBUTION IN A DOUBLE-CELL SEWAGE LAGOON (1) (2).

    PubMed

    DeNoyelles, F

    1967-12-01

    The distribution of phyioplankton in a double-cell sewage lagoon at Hallam, Nebraska, was studied in relation to physical, chemical, and biological factors during the summer and fall of 1965. Sixteen species of algae were recorded in the first and more organically rich of the two physically similar ponds, with 28 species recorded in the second pond. Population sizes were always greater in the first pond due to reduced grazing during the summer and large quantities of ammonia-nitrogen during the fall. The dominant algal species in both ponds on nearly all sampling dates was Ankistrodesmus falcatus v. acicularis. Declines in this population occurred with high organic pollution and heavy grazing. Both ponds had severe reductions in algal numbers during late October due to heavy grazing by the rotifer Brachionus. The distribution of phytoplankton in the Hallam ponds is compared to that of other sewage ponds in the United States, and the general pattern which emerged is discussed. PMID:27065027

  18. The Arabidopsis TAC Position Viewer: a high-resolution map of transformation-competent artificial chromosome (TAC) clones aligned with the Arabidopsis thaliana Columbia-0 genome.

    PubMed

    Hirose, Yoshitsugu; Suda, Kunihiro; Liu, Yao-Guang; Sato, Shusei; Nakamura, Yukino; Yokoyama, Koji; Yamamoto, Naoki; Hanano, Shigeru; Takita, Eiji; Sakurai, Nozomu; Suzuki, Hideyuki; Nakamura, Yasukazu; Kaneko, Takakazu; Yano, Kentaro; Tabata, Satoshi; Shibata, Daisuke

    2015-09-01

    We present a high-resolution map of genomic transformation-competent artificial chromosome (TAC) clones extending over all Arabidopsis thaliana (Arabidopsis) chromosomes. The Arabidopsis genomic TAC clones have been valuable genetic tools. Previously, we constructed an Arabidopsis genomic TAC library consisting of more than 10,000 TAC clones harboring large genomic DNA fragments extending over the whole Arabidopsis genome. Here, we determined 13,577 end sequences from 6987 Arabidopsis TAC clones and mapped 5937 TAC clones to precise locations, covering approximately 90% of the Arabidopsis chromosomes. We present the large-scale data set of TAC clones with high-resolution mapping information as a Java application tool, the Arabidopsis TAC Position Viewer, which provides ready-to-go transformable genomic DNA clones corresponding to certain loci on Arabidopsis chromosomes. The TAC clone resources will accelerate genomic DNA cloning, positional walking, complementation of mutants and DNA transformation for heterologous gene expression. PMID:26227242

  19. Substrate interactions in dehalogenation of 1,2-dichloroethane, 1,2-dichloropropane, and 1,1,2-trichloroethane mixtures by Dehalogenimonas spp.

    PubMed

    Dillehay, Jacob L; Bowman, Kimberly S; Yan, Jun; Rainey, Fred A; Moe, William M

    2014-04-01

    When chlorinated alkanes are present as soil or groundwater pollutants, they often occur in mixtures. This study evaluated substrate interactions during the anaerobic reductive dehalogenation of chlorinated alkanes by the type strains of two Dehalogenimonas species, D. lykanthroporepellens and D. alkenigignens. Four contaminant mixtures comprised of combinations of the chlorinated solvents 1,2-dichloroethane (1,2-DCA), 1,2-dichloropropane (1,2-DCP), and 1,1,2-trichloroethane (1,1,2-TCA) were assessed for each species. Chlorinated solvent depletion and daughter product formation determined as a function of time following inoculation into anaerobic media revealed preferential dechlorination of 1,1,2-TCA over both 1,2-DCA and 1,2-DCP for both species. 1,2-DCA in particular was not dechlorinated until 1,1,2-TCA reached low concentrations. In contrast, both species concurrently dechlorinated 1,2-DCA and 1,2-DCP over a comparably large concentration range. This is the first report of substrate interactions during chlorinated alkane dehalogenation by pure cultures, and the results provide insights into the chlorinated alkane transformation processes that may be expected for contaminant mixtures in environments where Dehalogenimonas spp. are present. PMID:23990262

  20. GCN2-dependent phosphorylation of eukaryotic translation initiation factor-2α in Arabidopsis

    PubMed Central

    Zhang, Yuhua; Wang, Yifei; Kanyuka, Kostya; Parry, Martin A. J.; Powers, Stephen J.; Halford, Nigel G.

    2008-01-01

    The yeast regulatory protein kinase, general control non-derepressible-2 (GCN2) plays a key role in general amino acid control. GCN2 phosphorylates the α subunit of the trimeric eukaryotic translation initiation factor-2 (eIF2), bringing about a decrease in the general rate of protein synthesis but an increase in the synthesis of GCN4, a transcription factor that promotes the expression of genes encoding enzymes for amino acid biosynthesis. The present study concerned the phosphorylation of Arabidopsis eIF2α (AteIF2α) by the Arabidopsis homologue of GCN2, AtGCN2, and the role of AtGCN2 in regulating genes encoding enzymes of amino acid biosynthesis and responding to virus infection. A null mutant for AtGCN2 called GT8359 was obtained and western analysis confirmed that it lacked AtGCN2 protein. GT8359 was more sensitive than wild-type Arabidopsis to herbicides that affect amino acid biosynthesis. Phosphorylation of AteIF2α occurred in response to herbicide treatment but only in wild-type Arabidopsis, not GT8359, showing it to be AtGCN2-dependent. Expression analysis of genes encoding key enzymes for amino acid biosynthesis and nitrate assimilation revealed little effect of loss of AtGCN2 function in GT8359 except that expression of a nitrate reductase gene, NIA1, was decreased. Analysis of wild-type and GT8359 plants infected with Turnip yellow mosaic virus or Turnip crinkle virus showed that AteIF2α was not phosphorylated. PMID:18603615

  1. Quantitative Genetic Analysis of Thermal Dissipation in Arabidopsis1[W][OA

    PubMed Central

    Jung, Hou-Sung; Niyogi, Krishna K.

    2009-01-01

    Feedback deexcitation is a photosynthetic regulatory mechanism that can protect plants from high light stress by harmlessly dissipating excess absorbed light energy as heat. To understand the genetic basis for intraspecies differences in thermal dissipation capacity, we investigated natural variation in Arabidopsis (Arabidopsis thaliana). We determined the variation in the amount of thermal dissipation by measuring nonphotochemical quenching (NPQ) of chlorophyll fluorescence in Arabidopsis accessions of diverse origins. Ll-1 and Sf-2 were selected as high NPQ Arabidopsis accessions, and Columbia-0 (Col-0) and Wassilewskija-2 were selected as relatively low NPQ accessions. In spite of significant differences in NPQ, previously identified NPQ factors were indistinguishable between the high and the low NPQ accessions. Intermediate levels of NPQ in Ll-1 × Col-0 F1 and Sf-2 × Col-0 F1 compared to NPQ levels in their parental lines and continuous distribution of NPQ in F2 indicated that the variation in NPQ is under the control of multiple nuclear factors. To identify genetic factors responsible for the NPQ variation, we developed a polymorphic molecular marker set for Sf-2 × Col-0 at approximately 10-centimorgan intervals. From quantitative trait locus (QTL) mapping with undistorted genotype data and NPQ measurements in an F2 mapping population, we identified two high NPQ QTLs, HQE1 (high qE 1, for high energy-dependent quenching 1) and HQE2, on chromosomes 1 and 2, and the phenotype of HQE2 was validated by analysis of near isogenic lines. Neither QTL maps to a gene that had been identified previously in extensive forward genetics screens using induced mutants, suggesting that quantitative genetics can be used to find new genes affecting thermal dissipation. PMID:19339502

  2. Gravity response mechanisms of lateral organs and the control of plant architecture in Arabidopsis

    NASA Astrophysics Data System (ADS)

    Mullen, J.; Hangarter, R.

    Most research on gravity responses in plants has focused on primary roots and shoots, which typically grow in a vertical orientation. However, the patterns of lateral organ formation and their growth orientation, which typically are not vertical, govern plant architecture. For example, in Arabidopsis, when lateral roots emerge from the primary root, they grow at a nearly horizontal orientation. As they elongate, the roots slowly curve until they eventually reach a vertical orientation. The regulation of this lateral root orientation is an important component affecting the overall root system architecture. We have found that this change in orientation is not simply due to the onset of gravitropic competence, as non-vertical lateral roots are capable of both positive and negative gravitropism. Thus, the horizontal growth of the new lateral roots is determined by what is called the gravitropic set-point angle (GSA). In Arabidopsis shoots, rosette leaves and inflorescence branches also display GSA-dependent developmental changes in their orientation. The developmental control of the GSA of lateral organs in Arabidopsis provides us with a useful system for investigating the components involved in regulating directionality of tropistic responses. We have identified several Arabidopsis mutants that have either altered lateral root orientations, altered orientation of lateral organs in the shoot, or both, but maintain normal primary organ orientation. The mgsa ({m}odified {g}ravitropic {s}et-point {a}ngle) mutants with both altered lateral root and shoot orientation show that there are common components in the regulation of growth orientation in the different organs. Rosette leaves and lateral roots also have in common a regulation of positioning by red light. Further molecular and physiological analyses of the GSA mutants will provide insight into the basis of GSA regulation and, thus, a better understanding of how gravity controls plant architecture. [This work was

  3. In Vitro Morphogenesis of Arabidopsis to Search for Novel Endophytic Fungi Modulating Plant Growth.

    PubMed

    Dovana, Francesco; Mucciarelli, Marco; Mascarello, Maurizio; Fusconi, Anna

    2015-01-01

    Fungal endophytes have shown to affect plant growth and to confer stress tolerance to the host; however, effects of endophytes isolated from water plants have been poorly investigated. In this study, fungi isolated from stems (stem-E) and roots (root-E) of Mentha aquatica L. (water mint) were identified, and their morphogenetic properties analysed on in vitro cultured Arabidopsis (L.) Heynh., 14 and 21 days after inoculation (DAI). Nineteen fungi were analysed and, based on ITS analysis, 17 isolates showed to be genetically distinct. The overall effect of water mint endophytes on Arabidopsis fresh (FW) and dry weight (DW) was neutral and positive, respectively, and the increased DW, mainly occurring 14 DAI, was possibly related to plant defence mechanism. Only three fungi increased both FW and DW of Arabidopsis at 14 and 21 DAI, thus behaving as plant growth promoting (PGP) fungi. E-treatment caused a reduction of root depth and primary root length in most cases and inhibition-to-promotion of root area and lateral root length, from 14 DAI. Only Phoma macrostoma, among the water mint PGP fungi, increased both root area and depth, 21 DAI. Root depth and area 14 DAI were shown to influence DWs, indicating that the extension of the root system, and thus nutrient uptake, was an important determinant of plant dry biomass. Reduction of Arabidopsis root depth occurred to a great extent when plants where treated with stem-E while root area decreased or increased under the effects of stem-E and root-E, respectively, pointing to an influence of the endophyte origin on root extension. M. aquatica and many other perennial hydrophytes have growing worldwide application in water pollution remediation. The present study provided a model for directed screening of endophytes able to modulate plant growth in the perspective of future field applications of these fungi. PMID:26641657

  4. In Vitro Morphogenesis of Arabidopsis to Search for Novel Endophytic Fungi Modulating Plant Growth

    PubMed Central

    Mascarello, Maurizio

    2015-01-01

    Fungal endophytes have shown to affect plant growth and to confer stress tolerance to the host; however, effects of endophytes isolated from water plants have been poorly investigated. In this study, fungi isolated from stems (stem-E) and roots (root-E) of Mentha aquatica L. (water mint) were identified, and their morphogenetic properties analysed on in vitro cultured Arabidopsis (L.) Heynh., 14 and 21 days after inoculation (DAI). Nineteen fungi were analysed and, based on ITS analysis, 17 isolates showed to be genetically distinct. The overall effect of water mint endophytes on Arabidopsis fresh (FW) and dry weight (DW) was neutral and positive, respectively, and the increased DW, mainly occurring 14 DAI, was possibly related to plant defence mechanism. Only three fungi increased both FW and DW of Arabidopsis at 14 and 21 DAI, thus behaving as plant growth promoting (PGP) fungi. E-treatment caused a reduction of root depth and primary root length in most cases and inhibition-to-promotion of root area and lateral root length, from 14 DAI. Only Phoma macrostoma, among the water mint PGP fungi, increased both root area and depth, 21 DAI. Root depth and area 14 DAI were shown to influence DWs, indicating that the extension of the root system, and thus nutrient uptake, was an important determinant of plant dry biomass. Reduction of Arabidopsis root depth occurred to a great extent when plants where treated with stem-E while root area decreased or increased under the effects of stem-E and root-E, respectively, pointing to an influence of the endophyte origin on root extension. M. aquatica and many other perennial hydrophytes have growing worldwide application in water pollution remediation. The present study provided a model for directed screening of endophytes able to modulate plant growth in the perspective of future field applications of these fungi. PMID:26641657

  5. Putative sugarcane FT/TFL1 genes delay flowering time and alter reproductive architecture in Arabidopsis

    PubMed Central

    Coelho, Carla P.; Minow, Mark A. A.; Chalfun-Júnior, Antonio; Colasanti, Joseph

    2014-01-01

    Agriculturally important grasses such as rice, maize, and sugarcane are evolutionarily distant from Arabidopsis, yet some components of the floral induction process are highly conserved. Flowering in sugarcane is an important factor that negatively affects cane yield and reduces sugar/ethanol production from this important perennial bioenergy crop. Comparative studies have facilitated the identification and characterization of putative orthologs of key flowering time genes in sugarcane, a complex polyploid plant whose genome has yet to be sequenced completely. Using this approach we identified phosphatidylethanolamine-binding protein (PEBP) gene family members in sugarcane that are similar to the archetypical FT and TFL1 genes of Arabidopsis that play an essential role in controlling the transition from vegetative to reproductive growth. Expression analysis of ScTFL1, which falls into the TFL1-clade of floral repressors, showed transcripts in developing leaves surrounding the shoot apex but not at the apex itself. ScFT1 was detected in immature leaves and apical regions of vegetatively growing plants and, after the floral transition, expression also occurred in mature leaves. Ectopic over-expression of ScTFL1 in Arabidopsis caused delayed flowering in Arabidopsis, as might be expected for a gene related to TFL1. In addition, lines with the latest flowering phenotype exhibited aerial rosette formation. Unexpectedly, over-expression of ScFT1, which has greatest similarity to the florigen-encoding FT, also caused a delay in flowering. This preliminary analysis of divergent sugarcane FT and TFL1 gene family members from Saccharum spp. suggests that their expression patterns and roles in the floral transition has diverged from the predicted role of similar PEBP family members. PMID:24904616

  6. A Single Amino Acid Substitution in an ORANGE Protein Promotes Carotenoid Overaccumulation in Arabidopsis1[OPEN

    PubMed Central

    Yuan, Hui; Owsiany, Katherine; Sheeja, T.E.; Zhou, Xiangjun; Rodriguez, Caroline; Li, Yongxi; Welsch, Ralf; Chayut, Noam; Yang, Yong; Thannhauser, Theodore W.; Parthasarathy, Mandayam V.; Xu, Qiang; Deng, Xiuxin; Fei, Zhangjun; Schaffer, Ari; Katzir, Nurit; Burger, Joseph; Tadmor, Yaakov; Li, Li

    2015-01-01

    Carotenoids are crucial for plant growth and human health. The finding of ORANGE (OR) protein as a pivotal regulator of carotenogenesis offers a unique opportunity to comprehensively understand the regulatory mechanisms of carotenoid accumulation and develop crops with enhanced nutritional quality. Here, we demonstrated that alteration of a single amino acid in a wild-type OR greatly enhanced its ability to promote carotenoid accumulation. Whereas overexpression of OR from Arabidopsis (Arabidopsis thaliana; AtOR) or from the agronomically important crop sorghum (Sorghum bicolor; SbOR) increased carotenoid levels up to 2-fold, expression of AtORHis (R90H) or SbORHis (R104H) variants dramatically enhanced carotenoid accumulation by up to 7-fold in the Arabidopsis calli. Moreover, we found that AtORAla (R90A) functioned similarly to AtORHis to promote carotenoid overproduction. Neither AtOR nor AtORHis greatly affected carotenogenic gene expression. AtORHis exhibited similar interactions with phytoene synthase (PSY) as AtOR in posttranscriptionally regulating PSY protein abundance. AtORHis triggered biogenesis of membranous chromoplasts in the Arabidopsis calli, which shared structures similar to chromoplasts found in the curd of the orange cauliflower (Brassica oleracea) mutant. By contrast, AtOR did not cause plastid-type changes in comparison with the controls, but produced plastids containing larger and electron-dense plastoglobuli. The unique ability of AtORHis in mediating chromoplast biogenesis is responsible for its induced carotenoid overproduction. Our study demonstrates ORHis/Ala as powerful tools for carotenoid enrichment in plants, and provides insights into the mechanisms underlying ORHis-regulated carotenoid accumulation. PMID:26224804

  7. The Arabidopsis COX11 Homolog is Essential for Cytochrome c Oxidase Activity

    PubMed Central

    Radin, Ivan; Mansilla, Natanael; Rödel, Gerhard; Steinebrunner, Iris

    2015-01-01

    Members of the ubiquitous COX11 (cytochrome c oxidase 11) protein family are involved in copper delivery to the COX complex. In this work, we characterize the Arabidopsis thaliana COX11 homolog (encoded by locus At1g02410). Western blot analyses and confocal microscopy identified Arabidopsis COX11 as an integral mitochondrial protein. Despite sharing high sequence and structural similarities, the Arabidopsis COX11 is not able to functionally replace the Saccharomyces cerevisiae COX11 homolog. Nevertheless, further analysis confirmed the hypothesis that Arabidopsis COX11 is essential for COX activity. Disturbance of COX11 expression through knockdown (KD) or overexpression (OE) affected COX activity. In KD lines, the activity was reduced by ~50%, resulting in root growth inhibition, smaller rosettes and leaf curling. In OE lines, the reduction was less pronounced (~80% of the wild type), still resulting in root growth inhibition. Additionally, pollen germination was impaired in COX11 KD and OE plants. This effect on pollen germination can only partially be attributed to COX deficiency and may indicate a possible auxiliary role of COX11 in ROS metabolism. In agreement with its role in energy production, the COX11 promoter is highly active in cells and tissues with high-energy demand for example shoot and root meristems, or vascular tissues of source and sink organs. In COX11 KD lines, the expression of the plasma-membrane copper transporter COPT2 and of several copper chaperones was altered, indicative of a retrograde signaling pathway pertinent to copper homeostasis. Based on our data, we postulate that COX11 is a mitochondrial chaperone, which plays an important role for plant growth and pollen germination as an essential COX complex assembly factor. PMID:26734017

  8. The Arabidopsis Epithiospecifier Protein Promotes the Hydrolysis of Glucosinolates to Nitriles and Influences Trichoplusia ni Herbivory

    PubMed Central

    Lambrix, Virginia; Reichelt, Michael; Mitchell-Olds, Thomas; Kliebenstein, Daniel J.; Gershenzon, Jonathan

    2001-01-01

    Glucosinolates are anionic thioglucosides that have become one of the most frequently studied groups of defensive metabolites in plants. When tissue damage occurs, the thioglucoside linkage is hydrolyzed by enzymes known as myrosinases, resulting in the formation of a variety of products that are active against herbivores and pathogens. In an effort to learn more about the molecular genetic and biochemical regulation of glucosinolate hydrolysis product formation, we analyzed leaf samples of 122 Arabidopsis ecotypes. A distinct polymorphism was observed with all ecotypes producing primarily isothiocyanates or primarily nitriles. The ecotypes Columbia (Col) and Landsberg erecta (Ler) differed in their hydrolysis products; therefore, the Col × Ler recombinant inbred lines were used for mapping the genes controlling this polymorphism. The major quantitative trait locus (QTL) affecting nitrile versus isothiocyanate formation was found very close to a gene encoding a homolog of a Brassica napus epithiospecifier protein (ESP), which causes the formation of epithionitriles instead of isothiocyanates during glucosinolate hydrolysis in the seeds of certain Brassicaceae. The heterologously expressed Arabidopsis ESP was able to convert glucosinolates both to epithionitriles and to simple nitriles in the presence of myrosinase, and thus it was more versatile than previously described ESPs. The role of ESP in plant defense is uncertain, because the generalist herbivore Trichoplusia ni (the cabbage looper) was found to feed more readily on nitrile-producing than on isothiocyanate-producing Arabidopsis. However, isothiocyanates are frequently used as recognition cues by specialist herbivores, and so the formation of nitriles instead of isothiocyanates may allow Arabidopsis to be less apparent to specialists. PMID:11752388

  9. The Arabidopsis COX11 Homolog is Essential for Cytochrome c Oxidase Activity.

    PubMed

    Radin, Ivan; Mansilla, Natanael; Rödel, Gerhard; Steinebrunner, Iris

    2015-01-01

    Members of the ubiquitous COX11 (cytochrome c oxidase 11) protein family are involved in copper delivery to the COX complex. In this work, we characterize the Arabidopsis thaliana COX11 homolog (encoded by locus At1g02410). Western blot analyses and confocal microscopy identified Arabidopsis COX11 as an integral mitochondrial protein. Despite sharing high sequence and structural similarities, the Arabidopsis COX11 is not able to functionally replace the Saccharomyces cerevisiae COX11 homolog. Nevertheless, further analysis confirmed the hypothesis that Arabidopsis COX11 is essential for COX activity. Disturbance of COX11 expression through knockdown (KD) or overexpression (OE) affected COX activity. In KD lines, the activity was reduced by ~50%, resulting in root growth inhibition, smaller rosettes and leaf curling. In OE lines, the reduction was less pronounced (~80% of the wild type), still resulting in root growth inhibition. Additionally, pollen germination was impaired in COX11 KD and OE plants. This effect on pollen germination can only partially be attributed to COX deficiency and may indicate a possible auxiliary role of COX11 in ROS metabolism. In agreement with its role in energy production, the COX11 promoter is highly active in cells and tissues with high-energy demand for example shoot and root meristems, or vascular tissues of source and sink organs. In COX11 KD lines, the expression of the plasma-membrane copper transporter COPT2 and of several copper chaperones was altered, indicative of a retrograde signaling pathway pertinent to copper homeostasis. Based on our data, we postulate that COX11 is a mitochondrial chaperone, which plays an important role for plant growth and pollen germination as an essential COX complex assembly factor. PMID:26734017

  10. Repression of Lateral Organ Boundary Genes by PENNYWISE and POUND-FOOLISH Is Essential for Meristem Maintenance and Flowering in Arabidopsis1[OPEN

    PubMed Central

    Khan, Madiha; Ragni, Laura; Tabb, Paul; Salasini, Brenda C.; Chatfield, Steven; Datla, Raju; Lock, John; Kuai, Xiahezi; Després, Charles; Proveniers, Marcel; Yongguo, Cao; Xiang, Daoquan; Morin, Halima; Rullière, Jean-Pierre; Citerne, Sylvie; Hepworth, Shelley R.; Pautot, Véronique

    2015-01-01

    In the model plant Arabidopsis (Arabidopsis thaliana), endogenous and environmental signals acting on the shoot apical meristem cause acquisition of inflorescence meristem fate. This results in changed patterns of aerial development seen as the transition from making leaves to the production of flowers separated by elongated internodes. Two related BEL1-like homeobox genes, PENNYWISE (PNY) and POUND-FOOLISH (PNF), fulfill this transition. Loss of function of these genes impairs stem cell maintenance and blocks internode elongation and flowering. We show here that pny pnf apices misexpress lateral organ boundary genes BLADE-ON-PETIOLE1/2 (BOP1/2) and KNOTTED-LIKE FROM ARABIDOPSIS THALIANA6 (KNAT6) together with ARABIDOPSIS THALIANA HOMEOBOX GENE1 (ATH1). Inactivation of genes in this module fully rescues pny pnf defects. We further show that BOP1 directly activates ATH1, whereas activation of KNAT6 is indirect. The pny pnf restoration correlates with renewed accumulation of transcripts conferring floral meristem identity, including FD, SQUAMOSA PROMOTER-BINDING PROTEIN LIKE genes, LEAFY, and APETALA1. To gain insight into how this module blocks flowering, we analyzed the transcriptome of BOP1-overexpressing plants. Our data suggest a central role for the microRNA156-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE-microRNA172 module in integrating stress signals conferred in part by promotion of jasmonic acid biosynthesis. These data reveal a potential mechanism by which repression of lateral organ boundary genes by PNY-PNF is essential for flowering. PMID:26417006

  11. Repression of Lateral Organ Boundary Genes by PENNYWISE and POUND-FOOLISH Is Essential for Meristem Maintenance and Flowering in Arabidopsis.

    PubMed

    Khan, Madiha; Ragni, Laura; Tabb, Paul; Salasini, Brenda C; Chatfield, Steven; Datla, Raju; Lock, John; Kuai, Xiahezi; Després, Charles; Proveniers, Marcel; Yongguo, Cao; Xiang, Daoquan; Morin, Halima; Rullière, Jean-Pierre; Citerne, Sylvie; Hepworth, Shelley R; Pautot, Véronique

    2015-11-01

    In the model plant Arabidopsis (Arabidopsis thaliana), endogenous and environmental signals acting on the shoot apical meristem cause acquisition of inflorescence meristem fate. This results in changed patterns of aerial development seen as the transition from making leaves to the production of flowers separated by elongated internodes. Two related BEL1-like homeobox genes, PENNYWISE (PNY) and POUND-FOOLISH (PNF), fulfill this transition. Loss of function of these genes impairs stem cell maintenance and blocks internode elongation and flowering. We show here that pny pnf apices misexpress lateral organ boundary genes BLADE-ON-PETIOLE1/2 (BOP1/2) and KNOTTED-LIKE FROM ARABIDOPSIS THALIANA6 (KNAT6) together with ARABIDOPSIS THALIANA HOMEOBOX GENE1 (ATH1). Inactivation of genes in this module fully rescues pny pnf defects. We further show that BOP1 directly activates ATH1, whereas activation of KNAT6 is indirect. The pny pnf restoration correlates with renewed accumulation of transcripts conferring floral meristem identity, including FD, SQUAMOSA PROMOTER-BINDING PROTEIN LIKE genes, LEAFY, and APETALA1. To gain insight into how this module blocks flowering, we analyzed the transcriptome of BOP1-overexpressing plants. Our data suggest a central role for the microRNA156-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE-microRNA172 module in integrating stress signals conferred in part by promotion of jasmonic acid biosynthesis. These data reveal a potential mechanism by which repression of lateral organ boundary genes by PNY-PNF is essential for flowering. PMID:26417006

  12. Proteomic profiling of tandem affinity purified 14-3-3 protein complexes in Arabidopsis thaliana

    PubMed Central

    Chang, Ing-Feng; Curran, Amy; Woolsey, Rebekah; Quilici, David; Cushman, John; Mittler, Ron; Harmon, Alice; Harper, Jeffrey

    2014-01-01

    In eukaryotes, 14-3-3 dimers regulate hundreds of functionally diverse proteins (clients), typically in phosphorylation-dependent interactions. To uncover new clients, a 14-3-3 omega (At1g78300) from Arabidopsis was engineered with a “tandem affinity purification” (TAP) tag and expressed in transgenic plants. Purified complexes were analyzed by tandem mass spectrometry. Results indicate that 14-3-3 omega can dimerize with at least 10 of the 12 14-3-3 isoforms expressed in Arabidopsis. The identification here of 121 putative clients provides support for in vivo 14-3-3 interactions with a diverse array of proteins, including those involved in: (1) Ion transport, such as a K+ channel (GORK), a Cl− channel (CLCg), Ca2+ channels belonging to the glutamate receptor family (GLRs 1.2, 2.1, 2.9, 3.4, 3.7); (2) hormone signaling, such as ACC synthase (isoforms ACS-6, 7 and 8 involved in ethylene synthesis) and the brassinolide receptors BRI1 and BAK1; (3) transcription, such as 7 WRKY family transcription factors; (4) metabolism, such as phosphoenol pyruvate (PEP) carboxylase; and (5) lipid signaling, such as phospholipase D (β, and γ). More than 80% (101) of these putative clients represent previously unidentified 14-3-3 interactors. These results raise the number of putative 14-3-3 clients identified in plants to over 300. PMID:19452453

  13. Arabidopsis nitrate reductase activity is stimulated by the E3 SUMO ligase AtSIZ1

    PubMed Central

    Park, Bong Soo; Song, Jong Tae; Seo, Hak Soo

    2011-01-01

    Small ubiquitin-related modifier (SUMO) is a small polypeptide that modulates protein activity and regulates hormone signalling, abiotic and biotic responses in plants. Here we show that AtSIZ regulates nitrogen assimilation in Arabidopsis through its E3 SUMO ligase function. Dwarf plants of siz1-2 flower early, show abnormal seed development and have high salicylic acid content and enhanced resistance to bacterial pathogens. These mutant phenotypes are reverted to wild-type phenotypes by exogenous ammonium but not by nitrate, phosphate or potassium. Decreased nitrate reductase activity in siz1-2 plants resulted in low nitrogen concentrations, low nitric oxide production and high nitrate content in comparison with wild-type plants. The nitrate reductases, NIA1 and NIA2, are sumoylated by AtSIZ1, which dramatically increases their activity. Both sumoylated and non-sumoylated NIA1 and NIA2 can form dimers. Our results indicate that AtSIZ1 positively controls nitrogen assimilation by promoting sumoylation of NRs in Arabidopsis. PMID:21772271

  14. Arabidopsis nitrate reductase activity is stimulated by the E3 SUMO ligase AtSIZ1.

    PubMed

    Park, Bong Soo; Song, Jong Tae; Seo, Hak Soo

    2011-01-01

    Small ubiquitin-related modifier (SUMO) is a small polypeptide that modulates protein activity and regulates hormone signalling, abiotic and biotic responses in plants. Here we show that AtSIZ regulates nitrogen assimilation in Arabidopsis through its E3 SUMO ligase function. Dwarf plants of siz1-2 flower early, show abnormal seed development and have high salicylic acid content and enhanced resistance to bacterial pathogens. These mutant phenotypes are reverted to wild-type phenotypes by exogenous ammonium but not by nitrate, phosphate or potassium. Decreased nitrate reductase activity in siz1-2 plants resulted in low nitrogen concentrations, low nitric oxide production and high nitrate content in comparison with wild-type plants. The nitrate reductases, NIA1 and NIA2, are sumoylated by AtSIZ1, which dramatically increases their activity. Both sumoylated and non-sumoylated NIA1 and NIA2 can form dimers. Our results indicate that AtSIZ1 positively controls nitrogen assimilation by promoting sumoylation of NRs in Arabidopsis. PMID:21772271

  15. Arabidopsis UDP-Sugar Pyrophosphorylase: Evidence for Two Isoforms

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arabidopsis UDP-sugar pyrophosphorylase (AtUSP, EC 2.7.7.64) is a broad substrate pyrophosphorylase that exhibits activity with GlcA-1-P, Gal-1-P, and Glc-1-P. AtUSP, a single gene in Arabidopsis, is widely expressed in tissues. Although USP exhibits activity with GlcA-1-P, it is not clear whether U...

  16. EnergyPlus 1.2.2

    Energy Science and Technology Software Center (ESTSC)

    2005-05-01

    EnergyPlus (E+) is a new whole-building energy analysis program that combines the best capabilities and features from BLAST and DOE-2 along with new capabilities. E+ modular implementation facilitates extending the program and adding links to other programs. The fluid loops and HVAC components support a "manager-interface" simulation protocol that allows for the independent simulation of subsystems, each possibly using a customized solution procedure. Thus, the E+ program structure allows the solution to a particular subsystemmore » to be computed without affecting the solution schemes used for the other subsystems. This fundamental requirement enables the integration of external models in the El+ building systems simulation.« less

  17. Expression and interaction analysis of Arabidopsis Skp1-related genes.

    PubMed

    Takahashi, Naoki; Kuroda, Hirofumi; Kuromori, Takashi; Hirayama, Takashi; Seki, Motoaki; Shinozaki, Kazuo; Shimada, Hiroaki; Matsui, Minami

    2004-01-01

    Specific protein degradation has been observed in several aspects of development and differentiation in many organisms. One example of such proteolysis is regulated by protein polyubiquitination that is promoted by the SCF complex consisting of Skp1, cullin, and an F-box protein. We examined the activities of the Arabidopsis Skp1-related proteins (ASKs). Among 19 annotated ASK genes, we isolated 16 of the corresponding cDNAs (ASK1, 2, 3, 4, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19), and examined their gene products for interactions with 24 representatives of F-box proteins carrying various classes of the C-terminal domains using the yeast two-hybrid system. As a result, we found diverse binding specificities: ASK1, ASK2, ASK11 and ASK12 interacted well with COI1, FKF1, UFO-like protein, LRR-containing F-box proteins, and other F-box proteins with unknown C-terminal motifs. We also observed specific interaction between F-box proteins and ASK3, ASK9, ASK13, ASK14, ASK16 and ASK18. In contrast, we detected no interaction between any of the 12 ASK proteins and F-box proteins containing CRFA, CRFB or CRFC domains. Both histochemical and RT-PCR analysis of eight ASK genes expression revealed unique expression patterns for the respective genes. PMID:14749489

  18. X-1-2 on ramp

    NASA Technical Reports Server (NTRS)

    1951-01-01

    The Bell Aircraft Corporation X-1-2 aircraft on the ramp at NACA High Speed Flight Research Station located on the South Base of Muroc Army Air Field in 1947. The X-1-2 flew until October 23, 1951, completing 74 glide and powered flights with nine different pilots. The aircraft has white paint and the NACA tail band. The black Xs are reference markings for tracking purposes. They were widely used on NACA aircraft in the early 1950s. There were five versions of the Bell X-1 rocket-powered research aircraft that flew at the NACA High-Speed Flight Research Station, Edwards, California. The bullet-shaped X-1 aircraft were built by Bell Aircraft Corporation, Buffalo, N.Y. for the U.S. Army Air Forces (after 1947, U.S. Air Force) and the National Advisory Committee for Aeronautics (NACA). The X-1 Program was originally designated the XS-1 for EXperimental Sonic. The X-1's mission was to investigate the transonic speed range (speeds from just below to just above the speed of sound) and, if possible, to break the 'sound barrier.' Three different X-1s were built and designated: X-1-1, X-1-2 (later modified to become the X-1E), and X-1-3. The basic X-1 aircraft were flown by a large number of different pilots from 1946 to 1951. The X-1 Program not only proved that humans could go beyond the speed of sound, it reinforced the understanding that technological barriers could be overcome. The X-1s pioneered many structural and aerodynamic advances including extremely thin, yet extremely strong wing sections; supersonic fuselage configurations; control system requirements; powerplant compatibility; and cockpit environments. The X-1 aircraft were the first transonic-capable aircraft to use an all-moving stabilizer. The flights of the X-1s opened up a new era in aviation. The first X-1 was air-launched unpowered from a Boeing B-29 Superfortress on Jan. 25, 1946. Powered flights began in December 1946. On Oct. 14, 1947, the X-1-1, piloted by Air Force Captain Charles 'Chuck' Yeager

  19. Generation and characterization of 1,2-diaryl-1,1,2,2-tetramethyldisilane cation radicals.

    PubMed

    Guirado, Gonzalo; Haze, Olesya; Dinnocenzo, Joseph P

    2010-05-21

    Nanosecond laser flash photolysis methods were used to generate and spectrally characterize the cation radicals of 1,2-diaryl-1,1,2,2,-tetramethyldisilanes (Ar = p-X-Ph, X = H, CH(3), OCH(3)) in hexafluoroisopropanol (HFIP) at room temperature. The disilane cation radicals rapidly reacted with methanol, with bimolecular rate constants ranging from 0.63 to 2.1 x 10(8) M(-1) s(-1). The cation radicals were found to react with tert-butanol 4-5 times more slowly than methanol, consistent with a small steric effect for nucleophile-assisted fragmentation of the Si-Si bond. The standard potentials for oxidation of the disilanes in HFIP were determined by two different methods: first, by measuring equilibrium constants for electron exchange between the disilanes and the cation radical of hexaethylbenzene and, second, by combining electrochemical data from cyclic voltammetry with the lifetimes of the disilane cation radicals measured by laser flash photolysis in the same media. Agreement between the two methods was excellent (1,2-di-p-methoxyphenyl-1,1,2,2,-tetramethyldisilane by slow scan cyclic voltammetry in acetonitrile was not found to be reversible, in contrast to prior literature reports. Possible explanations for the prior results are proposed. PMID:20405871

  20. Pathogen-induced systemic activation of a plant defensin gene in Arabidopsis follows a salicylic acid-independent pathway.

    PubMed Central

    Penninckx, I A; Eggermont, K; Terras, F R; Thomma, B P; De Samblanx, G W; Buchala, A; Métraux, J P; Manners, J M; Broekaert, W F

    1996-01-01

    A 5-kD plant defensin was purified from Arabidopsis leaves challenged with the fungus Alternaria brassicicola and shown to possess antifungal properties in vitro. The corresponding plant defensin gene was induced after treatment of leaves with methyl jasmonate or ethylene but not with salicylic acid or 2,6-dichloroisonicotinic acid. When challenged with A. brassicicola, the levels of the plant defensin protein and mRNA rose both in inoculated leaves and in nontreated leaves of inoculated plants (systemic leaves). These events coincided with an increase in the endogenous jasmonic acid content of both types of leaves. Systemic pathogen-induced expression of the plant defensin gene was unaffected in Arabidopsis transformants (nahG) or mutants (npr1 and cpr1) affected in the salicylic acid response but was strongly reduced in the Arabidopsis mutants eln2 and col1 that are blocked in their response to ethylene and methyl jasmonate, respectively. Our results indicate that systemic pathogen-induced expression of the plant defensin gene in Arabidopsis is independent of salicylic acid but requires components of the ethylene and jasmonic acid response. PMID:8989885

  1. Transcription Factor ATAF1 in Arabidopsis Promotes Senescence by Direct Regulation of Key Chloroplast Maintenance and Senescence Transcriptional Cascades.

    PubMed

    Garapati, Prashanth; Xue, Gang-Ping; Munné-Bosch, Sergi; Balazadeh, Salma

    2015-07-01

    Senescence represents a fundamental process of late leaf development. Transcription factors (TFs) play an important role for expression reprogramming during senescence; however, the gene regulatory networks through which they exert their functions, and their physiological integration, are still largely unknown. Here, we identify the Arabidopsis (Arabidopsis thaliana) abscisic acid (ABA)- and hydrogen peroxide-activated TF Arabidopsis thaliana activating factor1 (ATAF1) as a novel upstream regulator of senescence. ATAF1 executes its physiological role by affecting both key chloroplast maintenance and senescence-promoting TFs, namely GOLDEN2-LIKE1 (GLK1) and ORESARA1 (Arabidopsis NAC092), respectively. Notably, while ATAF1 activates ORESARA1, it represses GLK1 expression by directly binding to their promoters, thereby generating a transcriptional output that shifts the physiological balance toward the progression of senescence. We furthermore demonstrate a key role of ATAF1 for ABA- and hydrogen peroxide-induced senescence, in accordance with a direct regulatory effect on ABA homeostasis genes, including nine-CIS-epoxycarotenoid dioxygenase3 involved in ABA biosynthesis and ABC transporter G family member40, encoding an ABA transport protein. Thus, ATAF1 serves as a core transcriptional activator of senescence by coupling stress-related signaling with photosynthesis- and senescence-related transcriptional cascades. PMID:25953103

  2. Overexpression of ARGOS Genes Modifies Plant Sensitivity to Ethylene, Leading to Improved Drought Tolerance in Both Arabidopsis and Maize.

    PubMed

    Shi, Jinrui; Habben, Jeffrey E; Archibald, Rayeann L; Drummond, Bruce J; Chamberlin, Mark A; Williams, Robert W; Lafitte, H Renee; Weers, Ben P

    2015-09-01

    Lack of sufficient water is a major limiting factor to crop production worldwide, and the development of drought-tolerant germplasm is needed to improve crop productivity. The phytohormone ethylene modulates plant growth and development as well as plant response to abiotic stress. Recent research has shown that modifying ethylene biosynthesis and signaling can enhance plant drought tolerance. Here, we report novel negative regulators of ethylene signal transduction in Arabidopsis (Arabidopsis thaliana) and maize (Zea mays). These regulators are encoded by the ARGOS gene family. In Arabidopsis, overexpression of maize ARGOS1 (ZmARGOS1), ZmARGOS8, Arabidopsis ARGOS homolog ORGAN SIZE RELATED1 (AtOSR1), and AtOSR2 reduced plant sensitivity to ethylene, leading to enhanced drought tolerance. RNA profiling and genetic analysis suggested that the ZmARGOS1 transgene acts between an ethylene receptor and CONSTITUTIVE TRIPLE RESPONSE1 in the ethylene signaling pathway, affecting ethylene perception or the early stages of ethylene signaling. Overexpressed ZmARGOS1 is localized to the endoplasmic reticulum and Golgi membrane, where the ethylene receptors and the ethylene signaling protein ETHYLENE-INSENSITIVE2 and REVERSION-TO-ETHYLENE SENSITIVITY1 reside. In transgenic maize plants, overexpression of ARGOS genes also reduces ethylene sensitivity. Moreover, field testing showed that UBIQUITIN1:ZmARGOS8 maize events had a greater grain yield than nontransgenic controls under both drought stress and well-watered conditions. PMID:26220950

  3. Capturing Arabidopsis Root Architecture Dynamics with root-fit Reveals Diversity in Responses to Salinity1[W][OPEN

    PubMed Central

    Julkowska, Magdalena M.; Hoefsloot, Huub C.J.; Mol, Selena; Feron, Richard; de Boer, Gert-Jan; Haring, Michel A.; Testerink, Christa

    2014-01-01

    The plant root is the first organ to encounter salinity stress, but the effect of salinity on root system architecture (RSA) remains elusive. Both the reduction in main root (MR) elongation and the redistribution of the root mass between MRs and lateral roots (LRs) are likely to play crucial roles in water extraction efficiency and ion exclusion. To establish which RSA parameters are responsive to salt stress, we performed a detailed time course experiment in which Arabidopsis (Arabidopsis thaliana) seedlings were grown on agar plates under different salt stress conditions. We captured RSA dynamics with quadratic growth functions (root-fit) and summarized the salt-induced differences in RSA dynamics in three growth parameters: MR elongation, average LR elongation, and increase in number of LRs. In the ecotype Columbia-0 accession of Arabidopsis, salt stress affected MR elongation more severely than LR elongation and an increase in LRs, leading to a significantly altered RSA. By quantifying RSA dynamics of 31 different Arabidopsis accessions in control and mild salt stress conditions, different strategies for regulation of MR and LR meristems and root branching were revealed. Different RSA strategies partially correlated with natural variation in abscisic acid sensitivity and different Na+/K+ ratios in shoots of seedlings grown under mild salt stress. Applying root-fit to describe the dynamics of RSA allowed us to uncover the natural diversity in root morphology and cluster it into four response types that otherwise would have been overlooked. PMID:25271266

  4. Characterization of adaptation in phototropism of Arabidopsis thaliana

    NASA Technical Reports Server (NTRS)

    Poff, K. L.

    1991-01-01

    Phototropic curvature has been measured for etiolated Arabidopsis thaliana seedlings with and without a preirradiation. A bilateral preirradiation with 450-nm light at a fluence greater than about 0.1 micromole per square meter causes a rapid desensitization to a subsequent 450-nanometer unilateral irradiation at 0.5 micromole per square meter. Following a refractory period, the capacity to respond phototropically recovers to the predesensitization level, and the response is then enhanced. The length of the refractory period is between 10 and 20 minutes. Both the time needed for recovery and the extent of enhancement increase with increasing fluence of the bilateral preirradiation. Based on the relative spectral sensitivities of desensitization and enhancement, these responses can be separated. Desensitization is induced by blue light but not by red light. Enhancement, however, is induced by both blue and red light. Thus, enhancement can be induced without desensitization but not vice versa. Both desensitization and enhancement affect only the magnitude of the response and do not affect the fluence threshold.

  5. A DNA-damage-induced cell cycle checkpoint in Arabidopsis.

    PubMed Central

    Preuss, S B; Britt, A B

    2003-01-01

    Although it is well established that plant seeds treated with high doses of gamma radiation arrest development as seedlings, the cause of this arrest is unknown. The uvh1 mutant of Arabidopsis is defective in a homolog of the human repair endonuclease XPF, and uvh1 mutants are sensitive to both the toxic effects of UV and the cytostatic effects of gamma radiation. Here we find that gamma irradiation of uvh1 plants specifically triggers a G(2)-phase cell cycle arrest. Mutants, termed suppressor of gamma (sog), that suppress this radiation-induced arrest and proceed through the cell cycle unimpeded were recovered in the uvh1 background; the resulting irradiated plants are genetically unstable. The sog mutations fall into two complementation groups. They are second-site suppressors of the uvh1 mutant's sensitivity to gamma radiation but do not affect the susceptibility of the plant to UV radiation. In addition to rendering the plants resistant to the growth inhibitory effects of gamma radiation, the sog1 mutation affects the proper development of the pollen tetrad, suggesting that SOG1 might also play a role in the regulation of cell cycle progression during meiosis. PMID:12750343

  6. Photosynthetic lesions can trigger accelerated senescence in Arabidopsis thaliana

    PubMed Central

    Wang, Jing; Leister, Dario; Bolle, Cordelia

    2015-01-01

    Senescence is a highly regulated process characterized by the active breakdown of cells, which ultimately leads to the death of plant organs or whole plants. In annual plants such as Arabidopsis thaliana senescence can be observed in each individual leaf. Whether deficiencies in photosynthesis promote the induction of senescence was investigated by monitoring chlorophyll degradation, photosynthetic parameters, and reactive oxygen species accumulation in photosynthetic mutants. Several mutations affecting components of the photosynthetic apparatus, including psal-2, psan-2, and psbs, were found to lead to premature or faster senescence, as did simultaneous inactivation of the STN7 and STN8 kinases. Premature senescence is apparently not directly linked to an overall reduction in photosynthesis but to perturbations in specific aspects of the process. Dark-induced senescence is accelerated in mutants affected in linear electron flow, especially psad2-1, psan-2, and pete2-1, as well as in stn7 and stn8 mutants and STN7 and STN8 overexpressor lines. Interestingly, no direct link with ROS production could be observed. PMID:26272903

  7. Selection on Meiosis Genes in Diploid and Tetraploid Arabidopsis arenosa

    PubMed Central

    Wright, Kevin M.; Arnold, Brian; Xue, Katherine; Šurinová, Maria; O’Connell, Jeremy; Bomblies, Kirsten

    2015-01-01

    Meiotic chromosome segregation is critical for fertility across eukaryotes, and core meiotic processes are well conserved even between kingdoms. Nevertheless, recent work in animals has shown that at least some meiosis genes are highly diverse or strongly differentiated among populations. What drives this remains largely unknown. We previously showed that autotetraploid Arabidopsis arenosa evolved stable meiosis, likely through reduced crossover rates, and that associated with this there is strong evidence for selection in a subset of meiosis genes known to affect axis formation, synapsis, and crossover frequency. Here, we use genome-wide data to study the molecular evolution of 70 meiosis genes in a much wider sample of A. arenosa. We sample the polyploid lineage, a diploid lineage from the Carpathian Mountains, and a more distantly related diploid lineage from the adjacent, but biogeographically distinct Pannonian Basin. We find that not only did selection act on meiosis genes in the polyploid lineage but also independently on a smaller subset of meiosis genes in Pannonian diploids. Functionally related genes are targeted by selection in these distinct contexts, and in two cases, independent sweeps occurred in the same loci. The tetraploid lineage has sustained selection on more genes, has more amino acid changes in each, and these more often affect conserved or potentially functional sites. We hypothesize that Pannonian diploid and tetraploid A. arenosa experienced selection on structural proteins that mediate sister chromatid cohesion, the formation of meiotic chromosome axes, and synapsis, likely for different underlying reasons. PMID:25543117

  8. An alternating GluN1-2-1-2 subunit arrangement in mature NMDA receptors.

    PubMed

    Riou, Morgane; Stroebel, David; Edwardson, J Michael; Paoletti, Pierre

    2012-01-01

    NMDA receptors (NMDARs) form glutamate-gated ion channels that play a critical role in CNS physiology and pathology. Together with AMPA and kainate receptors, NMDARs are known to operate as tetrameric complexes with four membrane-embedded subunits associating to form a single central ion-conducting pore. While AMPA and some kainate receptors can function as homomers, NMDARs are obligatory heteromers composed of homologous but distinct subunits, most usually of the GluN1 and GluN2 types. A fundamental structural feature of NMDARs, that of the subunit arrangement around the ion pore, is still controversial. Thus, in a typical NMDAR associating two GluN1 and two GluN2 subunits, there is evidence for both alternating 1/2/1/2 and non-alternating 1/1/2/2 arrangements. Here, using a combination of electrophysiological and cross-linking experiments, we provide evidence that functional GluN1/GluN2A receptors adopt the 1/2/1/2 arrangement in which like subunits are diagonal to one another. Moreover, based on the recent crystal structure of an AMPA receptor, we show that in the agonist-binding and pore regions, the GluN1 subunits occupy a "proximal" position, closer to the central axis of the channel pore than that of GluN2 subunits. Finally, results obtained with reducing agents that differ in their membrane permeability indicate that immature (intracellular) and functional (plasma-membrane inserted) pools of NMDARs can adopt different subunit arrangements, thus stressing the importance of discriminating between the two receptor pools in assembly studies. Elucidating the quaternary arrangement of NMDARs helps to define the interface between the subunits and to understand the mechanism and pharmacology of these key signaling receptors. PMID:22493736

  9. The pore region of the Kv1.2alpha subunit is an important component of recombinant Kv1.2 channel oxygen sensitivity.

    PubMed

    Conforti, Laura; Takimoto, Koichi; Petrovic, Milan; Pongs, Olaf; Millhorn, David

    2003-06-27

    Oxygen-sensitive K(+) channels are important elements in the cellular response to hypoxia. Although much progress has been made in identifying their molecular composition, the structural components associated to their O(2)-sensitivity are not yet understood. Recombinant Kv1.2 currents expressed in Xenopus oocytes are inhibited by a decrease in O(2) availability. On the contrary, heterologous Kv2.1 channels are O(2)-insensitive. To elucidate the protein segment responsible for the O(2)-sensitivity of Kv1.2 channels, we analyzed the response to anoxia of Kv1.2/Kv2.1 chimeric channels. Expression of chimeric Kv2.1 channels each containing the S4, the S1-S3 or the S6-COOH segments of Kv1.2 polypeptide resulted in a K(+) current insensitive to anoxia. In contrast, transferring the S5-S6 segment of Kv1.2 into Kv2.1 produced an O(2)-sensitive K(+) current. Finally, mutating a redox-sensitive methionine residue (M380) of Kv1.2 polypeptide did not affect O(2)-sensitivity. Thus, the pore and its surrounding regions of Kv1.2 polypeptide confer its hypoxic inhibition. This response is independent on the redox modulation of methionine residues in this protein segment. PMID:12804584

  10. Olfactory mucosal necrosis in rats following acute intraperitoneal administration of 1,2-diethylbenzene, 1,2-diacetylbenzene and 2,5-hexanedione.

    PubMed

    Gagnaire, François; Boucard, Stéphane

    2014-03-01

    1,2-Diethylbenzene (1,2-DEB) is used in the manufacture of some plastics. Exposure to 1,2-DEB has been shown to induce peripheral neuropathy in rats. This neurotoxicity is thought to be caused by a metabolite, 1,2-diacetylbenzene (1,2-DAB), a γ-diketone-like compound. 1,2-DEB was previously shown to be extensively and rapidly taken up by the nasal mucosa in male rats. In the present study, the nasal mucosa in rats exposed to 1,2-DEB and 1,2-DAB were examined histologically. Results were compared to sections from rats exposed to two other DEB isomers - 1,3-diethylbenzene (1,3-DEB) and 1,4-diethylbenzene (1,4-DEB) - and to two other neurotoxic compounds - n-hexane and its γ-diketone metabolite, 2,5-hexanedione (2,5-HD). A single intraperitoneal dose of 1,2-DEB (200mg/kg) induced time-dependent necrosis in the olfactory epithelium and Bowman's glands, with lesions appearing from the earliest observation time (4h) in the dorsomedial olfactory mucosa. Lesions spread through the lateral and ventral parts of the ethmoturbinates over the following days. The dorsal and medial zones of the nasal cavity started to regenerate from 72h after treatment, with the new epithelium showing metaplasia. One month after treatment, most of the olfactory epithelium had returned to normal. 1,2-DAB (40mg/kg) caused the same lesions as those observed after treatment with 1,2-DEB. Treatment with 2,5-HD (1g/kg) also caused lesions of the olfactory epithelium, mainly at level IV. However, these were comparatively less severe than those observed after exposure to 1,2-DEB. In contrast, intraperitoneal injection of 1,3-DEB (800mg/kg), 1,4-DEB (800mg/kg) and n-hexane (2g/kg) did not affect the nasal mucosa. Pretreatment of rats with 5-phenyl-1-pentyne, an inhibitor of CYP2F2 and CYP2E1 completely inhibited the olfactory toxicity caused by 1,2-DEB. These results suggest that metabolic activation of 1,2-DEB may be responsible for the toxicity observed. PMID:24373906

  11. The Arabidopsis Mediator Complex Subunit16 Is a Key Component of Basal Resistance against the Necrotrophic Fungal Pathogen Sclerotinia sclerotiorum1[OPEN

    PubMed Central

    Wang, Chenggang; Yao, Jin; Du, Xuezhu; Zhang, Yanping; Sun, Yijun; Rollins, Jeffrey A.; Mou, Zhonglin

    2015-01-01

    Although Sclerotinia sclerotiorum is a devastating necrotrophic fungal plant pathogen in agriculture, the virulence mechanisms utilized by S. sclerotiorum and the host defense mechanisms against this pathogen have not been fully understood. Here, we report that the Arabidopsis (Arabidopsis thaliana) Mediator complex subunit MED16 is a key component of basal resistance against S. sclerotiorum. Mutants of MED16 are markedly more susceptible to S. sclerotiorum than mutants of 13 other Mediator subunits, and med16 has a much stronger effect on S. sclerotiorum-induced transcriptome changes compared with med8, a mutation not altering susceptibility to S. sclerotiorum. Interestingly, med16 is also more susceptible to S. sclerotiorum than coronatine-insensitive1-1 (coi1-1), which is the most susceptible mutant reported so far. Although the jasmonic acid (JA)/ethylene (ET) defense pathway marker gene PLANT DEFENSIN1.2 (PDF1.2) cannot be induced in either med16 or coi1-1, basal transcript levels of PDF1.2 in med16 are significantly lower than in coi1-1. Furthermore, ET-induced suppression of JA-activated wound responses is compromised in med16, suggesting a role for MED16 in JA-ET cross talk. Additionally, MED16 is required for the recruitment of RNA polymerase II to PDF1.2 and OCTADECANOID-RESPONSIVE ARABIDOPSIS ETHYLENE/ETHYLENE-RESPONSIVE FACTOR59 (ORA59), two target genes of both JA/ET-mediated and the transcription factor WRKY33-activated defense pathways. Finally, MED16 is physically associated with WRKY33 in yeast and in planta, and WRKY33-activated transcription of PDF1.2 and ORA59 as well as resistance to S. sclerotiorum depends on MED16. Taken together, these results indicate that MED16 regulates resistance to S. sclerotiorum by governing both JA/ET-mediated and WRKY33-activated defense signaling in Arabidopsis. PMID:26143252

  12. Arabidopsis OST1 protein kinase mediates the regulation of stomatal aperture by abscisic acid and acts upstream of reactive oxygen species production.

    PubMed

    Mustilli, Anna-Chiara; Merlot, Sylvain; Vavasseur, Alain; Fenzi, Francesca; Giraudat, Jérôme

    2002-12-01

    During drought, the plant hormone abscisic acid (ABA) triggers stomatal closure, thus reducing water loss. Using infrared thermography, we isolated two allelic Arabidopsis mutants (ost1-1 and ost1-2) impaired in the ability to limit their transpiration upon drought. These recessive ost1 mutations disrupted ABA induction of stomatal closure as well as ABA inhibition of light-induced stomatal opening. By contrast, the ost1 mutations did not affect stomatal regulation by light or CO(2), suggesting that OST1 is involved specifically in ABA signaling. The OST1 gene was isolated by positional cloning and was found to be expressed in stomatal guard cells and vascular tissue. In-gel assays indicated that OST1 is an ABA-activated protein kinase related to the Vicia faba ABA-activated protein kinase (AAPK). Reactive oxygen species (ROS) were shown recently to be an essential intermediate in guard cell ABA signaling. ABA-induced ROS production was disrupted in ost1 guard cells, whereas applied H(2)O(2) or calcium elicited the same degree of stomatal closure in ost1 as in the wild type. These results suggest that OST1 acts in the interval between ABA perception and ROS production. The relative positions of ost1 and the other ABA-insensitive mutations in the ABA signaling network (abi1-1, abi2-1, and gca2) are discussed. PMID:12468729

  13. Characterization of Sugar Insensitive (sis) Mutants of Arabidopsis

    SciTech Connect

    Gibson, Susan I.

    2009-06-08

    Despite the fact that soluble sugar levels have been postulated to play an important role in the control of a wide variety of plant metabolic and developmental pathways, the mechanisms by which plants respond to soluble sugar levels remain poorly understood. Plant responses to soluble sugar levels are also important in bioenergy production, as plant sugar responses are believed to help regulate both carbon fixation and carbon partitioning. For example, accumulation of soluble sugars, such as sucrose and glucose, in source tissues leads to feedback inhibition of photosynthesis, thereby decreasing rates of carbon fixation. Soluble sugar levels can also affect sink strengths, affecting the rates of accumulation of carbon-based compounds into both particular molecular forms (e.g. carbohydrates versus lipids versus proteins) and particular plant organs and tissues. Mutants of Arabidopsis that are defective in the ability to respond to soluble sugar levels were isolated and used as tools to identify some of the factors involved in plant sugar response. These sugar insensitive (sis) mutants were isolated by screening mutagenized seeds for those that were able to germinate and develop relatively normal shoot systems on media containing 0.3 M glucose or 0.3 M sucrose. At these sugar concentrations, wild-type Arabidopsis germinate and produce substantial root systems, but show little to no shoot development. Twenty-eight sis mutants were isolated during the course of four independent mutant screens. Based on a preliminary characterization of all of these mutants, sis3 and sis6 were chosen for further study. Both of these mutations appear to lie in previously uncharacterized loci. Unlike many other sugar-response mutants, sis3 mutants exhibit a wild-type or near wild-type response in all phytohormone-response assays conducted to date. The sis6-1 mutation is unusual in that it appears to be due to overexpression of a gene, rather than representing a loss of function mutation

  14. Progress towards measuring the 2S1 / 2 to 2P1 / 2 interval in hydrogen

    NASA Astrophysics Data System (ADS)

    Vutha, A. C.; Bezginov, N.; Ferchichi, I.; Hessels, E. A.

    2015-05-01

    There is a large discrepancy between the CODATA value for the proton charge radius, and its determinations from muonic hydrogen measurements. This discrepancy is referred to as the proton radius puzzle. Improved measurements on atomic hydrogen can elucidate the origins of this discrepancy. We have constructed an experiment to measure the Lamb shift (n = 2 ,S1 / 2 -->P1 / 2) in a fast beam of atomic hydrogen. Using a novel separated-oscillatory-fields method and high signal-to-noise ratio detection, we can measure the center of this transition with a statistical uncertainty approaching 10-5 of its natural linewidth. We report on our studies of systematic effects, and on our progress towards a new measurement of the proton charge radius. We acknowledge funding from NSERC, CFI, CRC, ORF, and NIST.

  15. Electrical properties of Ba(Dy1/2Nb1/2)O3 ceramic

    NASA Astrophysics Data System (ADS)

    Nath, K. Amar; Chandra, K. P.; Dubey, K.; Prasad, K.

    2016-05-01

    Polycrystalline Ba(Dy1/2Nb1/2)O3 was prepared using a high-temperature solid-state reaction method. X-ray diffraction analysis indicated the formation of a single-phase cubic structure having space group Pm3m. AC impedance plots as a function of frequency at different temperatures were used to analyse the electrical behaviour of the sample, which indicated the negative temperature coefficient of resistance character. Complex impedance analysis targeted non-Debye type dielectric relaxation. Frequency dependent ac conductivity data obeyed Jonscher's power law. The apparent activation energy was estimated to be 0.97 eV at 1 kHz.

  16. ERK1/2 can feedback-regulate cellular MEK1/2 levels.

    PubMed

    Hong, Seung-Keun; Wu, Pui-Kei; Karkhanis, Mansi; Park, Jong-In

    2015-10-01

    Signal transduction of the Raf/MEK/ERK pathway is regulated by various feedback mechanisms. Given the greater molar ratio between Raf-MEK than between MEK-ERK in cells, it may be possible that MEK1/2 levels are regulated to modulate Raf/MEK/ERK activity upon pathway stimulation. Nevertheless, it has not been reported whether MEK1/2 expression can be subject to a feedback regulation. Here, we report that the Raf/MEK/ERK pathway can feedback-regulate cellular MEK1 and MEK2 levels. In different cell types, ΔRaf-1:ER- or B-Raf(V600E)-mediated MEK/ERK activation increased MEK1 but decreased MEK2 levels. These regulations were abrogated by ERK1/2 knockdown mediated by RNA interference, suggesting the presence of a feedback mechanism that regulates MEK1/2 levels. Subsequently, analyses using qPCR and luciferase reporters of the DNA promoter and 3' untranslated region revealed that the feedback MEK1 upregulation was in part attributed to increased transcription. However, the feedback MEK2 downregulation was only observed at protein levels, which was blocked by the proteasome inhibitors, MG132 and bortezomib, suggesting that the MEK2 regulation is mediated at a post-translational level. These results suggest that the Raf/MEK/ERK pathway can feedback-regulate cellular levels of MEK1 and MEK2, wherein MEK1 levels are upregulated at transcriptional level whereas MEK2 levels are downregulated at posttranslational level. PMID:26163823

  17. Nuclear activity of ROXY1, a glutaredoxin interacting with TGA factors, is required for petal development in Arabidopsis thaliana.

    PubMed

    Li, Shutian; Lauri, Andrea; Ziemann, Mark; Busch, Andrea; Bhave, Mrinal; Zachgo, Sabine

    2009-02-01

    Glutaredoxins (GRXs) have thus far been associated mainly with redox-regulated processes participating in stress responses. However, ROXY1, encoding a GRX, has recently been shown to regulate petal primorida initiation and further petal morphogenesis in Arabidopsis thaliana. ROXY1 belongs to a land plant-specific class of GRXs that has a CC-type active site motif, which deviates from ubiquitously occurring CPYC and CGFS GRXs. Expression studies of yellow fluorescent protein-ROXY1 fusion genes driven by the cauliflower mosaic virus 35S promoter reveal a nucleocytoplasmic distribution of ROXY1. We demonstrate that nuclear localization of ROXY1 is indispensable and thus crucial for its activity in flower development. Yeast two-hybrid screens identified TGA transcription factors as interacting proteins, which was confirmed by bimolecular fluorescence complementation experiments showing their nuclear interaction in planta. Overlapping expression patterns of ROXY1 and TGA genes during flower development demonstrate that ROXY1/TGA protein interactions can occur in vivo and support their biological relevance in petal development. Deletion analysis of ROXY1 demonstrates the importance of the C terminus for its functionality and for mediating ROXY1/TGA protein interactions. Phenotypic analysis of the roxy1-2 pan double mutant and an engineered chimeric repressor mutant from PERIANTHIA (PAN), a floral TGA gene, supports a dual role of ROXY1 in petal development. Together, our results show that the ROXY1 protein functions in the nucleus, likely by modifying PAN posttranslationally and thereby regulating its activity in petal primordia initiation. Additionally, ROXY1 affects later petal morphogenesis, probably by modulating other TGA factors that might act redundantly during differentiation of second whorl organs. PMID:19218396