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Sample records for acid aba inhibits

  1. Chemical inhibition of potato ABA-8'-hydroxylase activity alters in vitro and in vivo ABA metabolism and endogenous ABA levels but does not affect potato microtuber dormancy duration.

    PubMed

    Suttle, Jeffrey C; Abrams, Suzanne R; De Stefano-Beltrán, Luis; Huckle, Linda L

    2012-09-01

    The effects of azole-type P450 inhibitors and two metabolism-resistant abscisic acid (ABA) analogues on in vitro ABA-8'-hydroxylase activity, in planta ABA metabolism, endogenous ABA content, and tuber meristem dormancy duration were examined in potato (Solanum tuberosum L. cv. Russet Burbank). When functionally expressed in yeast, three potato CYP707A genes were demonstrated to encode enzymatically active ABA-8'-hydroxylases with micromolar affinities for (+)-ABA. The in vitro activity of the three enzymes was inhibited by the P450 azole-type inhibitors ancymidol, paclobutrazol, diniconazole, and tetcyclasis, and by the 8'-acetylene- and 8'-methylene-ABA analogues, with diniconazole and tetcyclasis being the most potent inhibitors. The in planta metabolism of [(3)H](±)-ABA to phaseic acid and dihydrophaseic acid in tuber meristems was inhibited by diniconazole, tetcyclasis, and to a lesser extent by 8'-acetylene- and 8'-methylene-ABA. Continuous exposure of in vitro generated microtubers to diniconazole resulted in a 2-fold increase in endogenous ABA content and a decline in dihydrophaseic acid content after 9 weeks of development. Similar treatment with 8'-acetylene-ABA had no effects on the endogenous contents of ABA or phaseic acid but reduced the content of dihydrophaseic acid. Tuber meristem dormancy progression was determined ex vitro in control, diniconazole-, and 8'-acetylene-ABA-treated microtubers following harvest. Continuous exposure to diniconazole during microtuber development had no effects on subsequent sprouting at any time point. Continuous exposure to 8'-acetylene-ABA significantly increased the rate of microtuber sprouting. The results indicate that, although a decrease in ABA content is a hallmark of tuber dormancy progression, the decline in ABA levels is not a prerequisite for dormancy exit and the onset of tuber sprouting.

  2. Mutations in the Arabidopsis Lst8 and Raptor genes encoding partners of the TOR complex, or inhibition of TOR activity decrease abscisic acid (ABA) synthesis.

    PubMed

    Kravchenko, Alena; Citerne, Sylvie; Jéhanno, Isabelle; Bersimbaev, Rakhmetkazhi I; Veit, Bruce; Meyer, Christian; Leprince, Anne-Sophie

    2015-11-27

    The Target of Rapamycin (TOR) kinase regulates essential processes in plant growth and development by modulation of metabolism and translation in response to environmental signals. In this study, we show that abscisic acid (ABA) metabolism is also regulated by the TOR kinase. Indeed ABA hormone level strongly decreases in Lst8-1 and Raptor3g mutant lines as well as in wild-type (WT) Arabidopsis plants treated with AZD-8055, a TOR inhibitor. However the growth and germination of these lines are more sensitive to exogenous ABA. The diminished ABA hormone accumulation is correlated with lower transcript levels of ZEP, NCED3 and AAO3 biosynthetic enzymes, and higher transcript amount of the CYP707A2 gene encoding a key-enzyme in abscisic acid catabolism. These results suggest that the TOR signaling pathway is implicated in the regulation of ABA accumulation in Arabidopsis.

  3. Abscisic acid (ABA) regulates grape bud dormancy, and dormancy release stimuli may act through modification of ABA metabolism

    PubMed Central

    Zheng, Chuanlin; Halaly, Tamar; Acheampong, Atiako Kwame; Takebayashi, Yumiko; Jikumaru, Yusuke; Kamiya, Yuji; Or, Etti

    2015-01-01

    In warm-winter regions, induction of dormancy release by hydrogen cyanamide (HC) is mandatory for commercial table grape production. Induction of respiratory stress by HC leads to dormancy release via an uncharacterized biochemical cascade that could reveal the mechanism underlying this phenomenon. Previous studies proposed a central role for abscisic acid (ABA) in the repression of bud meristem activity, and suggested its removal as a critical step in the HC-induced cascade. In the current study, support for these assumptions was sought. The data show that ABA indeed inhibits dormancy release in grape (Vitis vinifera) buds and attenuates the advancing effect of HC. However, HC-dependent recovery was detected, and was affected by dormancy status. HC reduced VvXERICO and VvNCED transcript levels and induced levels of VvABA8’OH homologues. Regulation of these central players in ABA metabolism correlated with decreased ABA and increased ABA catabolite levels in HC-treated buds. Interestingly, an inhibitor of ethylene signalling attenuated these effects of HC on ABA metabolism. HC also modulated the expression of ABA signalling regulators, in a manner that supports a decreased ABA level and response. Taken together, the data support HC-induced removal of ABA-mediated repression via regulation of ABA metabolism and signalling. Expression profiling during the natural dormancy cycle revealed that at maximal dormancy, the HC-regulated VvNCED1 transcript level starts to drop. In parallel, levels of VvA8H-CYP707A4 transcript and ABA catabolites increase sharply. This may provide initial support for the involvement of ABA metabolism also in the execution of natural dormancy. PMID:25560179

  4. Abscisic acid (ABA) regulates grape bud dormancy, and dormancy release stimuli may act through modification of ABA metabolism.

    PubMed

    Zheng, Chuanlin; Halaly, Tamar; Acheampong, Atiako Kwame; Takebayashi, Yumiko; Jikumaru, Yusuke; Kamiya, Yuji; Or, Etti

    2015-03-01

    In warm-winter regions, induction of dormancy release by hydrogen cyanamide (HC) is mandatory for commercial table grape production. Induction of respiratory stress by HC leads to dormancy release via an uncharacterized biochemical cascade that could reveal the mechanism underlying this phenomenon. Previous studies proposed a central role for abscisic acid (ABA) in the repression of bud meristem activity, and suggested its removal as a critical step in the HC-induced cascade. In the current study, support for these assumptions was sought. The data show that ABA indeed inhibits dormancy release in grape (Vitis vinifera) buds and attenuates the advancing effect of HC. However, HC-dependent recovery was detected, and was affected by dormancy status. HC reduced VvXERICO and VvNCED transcript levels and induced levels of VvABA8'OH homologues. Regulation of these central players in ABA metabolism correlated with decreased ABA and increased ABA catabolite levels in HC-treated buds. Interestingly, an inhibitor of ethylene signalling attenuated these effects of HC on ABA metabolism. HC also modulated the expression of ABA signalling regulators, in a manner that supports a decreased ABA level and response. Taken together, the data support HC-induced removal of ABA-mediated repression via regulation of ABA metabolism and signalling. Expression profiling during the natural dormancy cycle revealed that at maximal dormancy, the HC-regulated VvNCED1 transcript level starts to drop. In parallel, levels of VvA8H-CYP707A4 transcript and ABA catabolites increase sharply. This may provide initial support for the involvement of ABA metabolism also in the execution of natural dormancy.

  5. Isolation of a wheat (Triticum aestivum L.) mutant in ABA 8'-hydroxylase gene: effect of reduced ABA catabolism on germination inhibition under field condition.

    PubMed

    Chono, Makiko; Matsunaka, Hitoshi; Seki, Masako; Fujita, Masaya; Kiribuchi-Otobe, Chikako; Oda, Shunsuke; Kojima, Hisayo; Kobayashi, Daisuke; Kawakami, Naoto

    2013-03-01

    Pre-harvest sprouting, the germination of mature seeds on the mother plant under moist condition, is a serious problem in cereals. To investigate the effect of reduced abscisic acid (ABA) catabolism on germination in hexaploid wheat (Triticum aestivum L.), we cloned the wheat ABA 8'-hydroxyase gene which was highly expressed during seed development (TaABA8'OH1) and screened for mutations that lead to reduced ABA catabolism. In a screen for natural variation, one insertion mutation in exon 5 of TaABA8'OH1 on the D genome (TaABA8'OH1-D) was identified in Japanese cultivars including 'Tamaizumi'. However, a single mutation in TaABA8'OH1-D had no clear effect on germination inhibition in double haploid lines. In a screen for a mutation, one deletion mutant lacking the entire TaABA8'OH1 on the A genome (TaABA8'OH1-A), TM1833, was identified from gamma-ray irradiation lines of 'Tamaizumi'. TM1833 (a double mutant in TaABA8'OH1-A and TaABA8'OH1-D) showed lower TaABA8'OH1 expression, higher ABA content in embryos during seed development under field condition and lower germination than those in 'Tamaizumi' (a single mutant in TaABA8'OH1-D). These results indicate that reduced ABA catabolism through mutations in TaABA8'OH1 may be effective in germination inhibition in field-grown wheat.

  6. Isolation of a wheat (Triticum aestivum L.) mutant in ABA 8′-hydroxylase gene: effect of reduced ABA catabolism on germination inhibition under field condition

    PubMed Central

    Chono, Makiko; Matsunaka, Hitoshi; Seki, Masako; Fujita, Masaya; Kiribuchi-Otobe, Chikako; Oda, Shunsuke; Kojima, Hisayo; Kobayashi, Daisuke; Kawakami, Naoto

    2013-01-01

    Pre-harvest sprouting, the germination of mature seeds on the mother plant under moist condition, is a serious problem in cereals. To investigate the effect of reduced abscisic acid (ABA) catabolism on germination in hexaploid wheat (Triticum aestivum L.), we cloned the wheat ABA 8′-hydroxyase gene which was highly expressed during seed development (TaABA8′OH1) and screened for mutations that lead to reduced ABA catabolism. In a screen for natural variation, one insertion mutation in exon 5 of TaABA8′OH1 on the D genome (TaABA8′OH1-D) was identified in Japanese cultivars including ‘Tamaizumi’. However, a single mutation in TaABA8′OH1-D had no clear effect on germination inhibition in double haploid lines. In a screen for a mutation, one deletion mutant lacking the entire TaABA8′OH1 on the A genome (TaABA8′OH1-A), TM1833, was identified from gamma-ray irradiation lines of ‘Tamaizumi’. TM1833 (a double mutant in TaABA8′OH1-A and TaABA8′OH1-D) showed lower TaABA8′OH1 expression, higher ABA content in embryos during seed development under field condition and lower germination than those in ‘Tamaizumi’ (a single mutant in TaABA8′OH1-D). These results indicate that reduced ABA catabolism through mutations in TaABA8′OH1 may be effective in germination inhibition in field-grown wheat. PMID:23641187

  7. [Role of NO signal in ABA-induced phenolic acids accumulation in Salvia miltiorrhiza hairy roots].

    PubMed

    Shen, Lihong; Ren, Jiahui; Jin, Wenfang; Wang, Ruijie; Ni, Chunhong; Tong, Mengjiao; Liang, Zongsuo; Yang, Dongfeng

    2016-02-01

    To investigate roles of nitric oxide (NO) signal in accumulations of phenolic acids in abscisic.acid (ABA)-induced Salvia miltiorrhiza hairy roots, S. miltiorrhiza hairy roots were treated with different concentrations of sodium nitroprusside (SNP)-an exogenous NO donor, for 6 days, and contents of phenolic acids in the hairy roots are determined. Then with treatment of ABA and NO scavenger (2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylimidazoline-1- oxyl-3-oxide, c-PTIO) or NO synthase inhibitor (NG-nitro-L-arginine methyl ester, L-NAME), contents of phenolic acids and expression levels of three key genes involved in phenolic acids biosynthesis were detected. Phenolic acids production in S. miltiorrhiza hairy roots was most significantly improved by 100 µmoL/L SNP. Contents of RA and salvianolic acid B increased by 3 and 4 folds. ABA significantly improved transcript levels of PAL (phenylalanine ammonia lyase), TAT (tyrosine aminotransferase) and RAS (rosmarinic acid synthase), and increased phenolic acids accumulations. However, with treatments of ABA+c-PTIO or ABA+L-NAME, accumulations of phenolic acids and expression levels of the three key genes were significantly inhibited. Both NO and ABA can increase accumulations of phenolic acids in S. miltiorrhiza hairy roots. NO signal probably mediates the ABA-induced phenolic acids production. PMID:27382772

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

    PubMed Central

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

    2016-01-01

    Drought inhibits plant growth and can also induce premature senescence. Here we identify a transcription factor, ABA INSENSITIVE GROWTH 1 (ABIG1) required for abscisic acid (ABA) mediated growth inhibition, but not for stomatal closure. ABIG1 mRNA levels are increased both in response to drought and in response to ABA treatment. When treated with ABA, abig1 mutants remain greener and produce more leaves than comparable wild-type plants. When challenged with drought, abig1 mutants have fewer yellow, senesced leaves than wild-type. Induction of ABIG1 transcription mimics ABA treatment and regulates a set of genes implicated in stress responses. We propose a model in which drought acts through ABA to increase ABIG1 transcription which in turn restricts new shoot growth and promotes leaf senescence. The results have implications for plant breeding: the existence of a mutant that is both ABA resistant and drought resistant points to new strategies for isolating drought resistant genetic varieties. DOI: http://dx.doi.org/10.7554/eLife.13768.001 PMID:27697148

  9. Abscisic acid (ABA) regulation of Arabidopsis SR protein gene expression.

    PubMed

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

    2014-01-01

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

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

    PubMed Central

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

    2014-01-01

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

  11. Rapid Phosphoproteomic Effects of Abscisic Acid (ABA) on Wild-Type and ABA Receptor-Deficient A. thaliana Mutants*

    PubMed Central

    Minkoff, Benjamin B.; Stecker, Kelly E.; Sussman, Michael R.

    2015-01-01

    Abscisic acid (ABA)1 is a plant hormone that controls many aspects of plant growth, including seed germination, stomatal aperture size, and cellular drought response. ABA interacts with a unique family of 14 receptor proteins. This interaction leads to the activation of a family of protein kinases, SnRK2s, which in turn phosphorylate substrates involved in many cellular processes. The family of receptors appears functionally redundant. To observe a measurable phenotype, four of the fourteen receptors have to be mutated to create a multilocus loss-of-function quadruple receptor (QR) mutant, which is much less sensitive to ABA than wild-type (WT) plants. Given these phenotypes, we asked whether or not a difference in ABA response between the WT and QR backgrounds would manifest on a phosphorylation level as well. We tested WT and QR mutant ABA response using isotope-assisted quantitative phosphoproteomics to determine what ABA-induced phosphorylation changes occur in WT plants within 5 min of ABA treatment and how that phosphorylation pattern is altered in the QR mutant. We found multiple ABA-induced phosphorylation changes that occur within 5 min of treatment, including three SnRK2 autophosphorylation events and phosphorylation on SnRK2 substrates. The majority of robust ABA-dependent phosphorylation changes observed were partially diminished in the QR mutant, whereas many smaller ABA-dependent phosphorylation changes observed in the WT were not responsive to ABA in the mutant. A single phosphorylation event was increased in response to ABA treatment in both the WT and QR mutant. A portion of the discovery data was validated using selected reaction monitoring-based targeted measurements on a triple quadrupole mass spectrometer. These data suggest that different subsets of phosphorylation events depend upon different subsets of the ABA receptor family to occur. Altogether, these data expand our understanding of the model by which the family of ABA receptors directs

  12. Rapid Phosphoproteomic Effects of Abscisic Acid (ABA) on Wild-Type and ABA Receptor-Deficient A. thaliana Mutants.

    PubMed

    Minkoff, Benjamin B; Stecker, Kelly E; Sussman, Michael R

    2015-05-01

    Abscisic acid (ABA)¹ is a plant hormone that controls many aspects of plant growth, including seed germination, stomatal aperture size, and cellular drought response. ABA interacts with a unique family of 14 receptor proteins. This interaction leads to the activation of a family of protein kinases, SnRK2s, which in turn phosphorylate substrates involved in many cellular processes. The family of receptors appears functionally redundant. To observe a measurable phenotype, four of the fourteen receptors have to be mutated to create a multilocus loss-of-function quadruple receptor (QR) mutant, which is much less sensitive to ABA than wild-type (WT) plants. Given these phenotypes, we asked whether or not a difference in ABA response between the WT and QR backgrounds would manifest on a phosphorylation level as well. We tested WT and QR mutant ABA response using isotope-assisted quantitative phosphoproteomics to determine what ABA-induced phosphorylation changes occur in WT plants within 5 min of ABA treatment and how that phosphorylation pattern is altered in the QR mutant. We found multiple ABA-induced phosphorylation changes that occur within 5 min of treatment, including three SnRK2 autophosphorylation events and phosphorylation on SnRK2 substrates. The majority of robust ABA-dependent phosphorylation changes observed were partially diminished in the QR mutant, whereas many smaller ABA-dependent phosphorylation changes observed in the WT were not responsive to ABA in the mutant. A single phosphorylation event was increased in response to ABA treatment in both the WT and QR mutant. A portion of the discovery data was validated using selected reaction monitoring-based targeted measurements on a triple quadrupole mass spectrometer. These data suggest that different subsets of phosphorylation events depend upon different subsets of the ABA receptor family to occur. Altogether, these data expand our understanding of the model by which the family of ABA receptors directs

  13. ABA-alcohol is an intermediate in abscisic acid biosynthesis

    SciTech Connect

    Rock, C.D.; Zeevaart, J.A.D. )

    1990-05-01

    It has been established that ABA-aldehyde is a precursor to ABA. The ABA-deficient flacca and sitiens mutants of tomato are blocked in the conversion of ABA-aldehyde to ABA, and accumulate trans-ABA-alcohol. {sup 18}O-Labeling studies of ABA in flacca and sitiens show that these mutants synthesize a large percentage of ({sup 18}O)ABA which contains two {sup 18}O atoms in the carboxyl group. Furthermore, the mutants synthesize much greater amounts of trans-ABA-glucose ester (t-ABA-GE) compared with the wild type, and this ({sup 18}O)t-ABA-GE is also double labeled in the carboxyl group. Our interpretation of these data is that the {sup 18}O in ABA-aldehyde is trapped in the side chain by reduction to ({sup 18}O)ABA-alcohol, followed by isomerization to ({sup 18}O)t-ABA-alcohol and oxidation with {sup 18}O{sub 2} to ({sup 18}O)t-ABA. The ({sup 18}O)t-ABA is then rapidly converted to ({sup 18}O)t-ABA-GE. Because ({sup 18}O)ABA doubly labeled in the carboxyl group has been observed in small amounts in labeling experiments with several species, and various species have been shown to convert ABA-aldehyde to ABA-alcohol and t-ABA-alcohol, we propose that ABA-alcohol is an ABA intermediate in a shunt pathway.

  14. ALA Inhibits ABA-induced Stomatal Closure via Reducing H2O2 and Ca(2+) Levels in Guard Cells.

    PubMed

    An, Yuyan; Liu, Longbo; Chen, Linghui; Wang, Liangju

    2016-01-01

    5-Aminolevulinic acid (ALA), a newly proved natural plant growth regulator, is well known to improve plant photosynthesis under both normal and stressful conditions. However, its underlying mechanism remains largely unknown. Stomatal closure is one of the major limiting factors for photosynthesis and abscisic acid (ABA) is the most important hormone in provoking stomatal closing. Here, we showed that ALA significantly inhibited ABA-induced stomatal closure using wild-type and ALA-overproducing transgenic Arabidopsis (YHem1). We found that ALA decreased ABA-induced H2O2 and cytosolic Ca(2+) accumulation in guard cells with stomatal bioassay, laser-scanning confocal microscopy and pharmacological methods. The inhibitory effect of ALA on ABA-induced stomatal closure was similar to that of AsA (an important reducing substrate for H2O2 removal), CAT (a H2O2-scavenging enzyme), DPI (an inhibitor of the H2O2-generating NADPH oxidase), EGTA (a Ca-chelating agent), and AlCl3 (an inhibitor of calcium channel). Furthermore, ALA inhibited exogenous H2O2- or Ca(2+)-induced stomatal closure. Taken together, we conclude that ALA inhibits ABA-induced stomatal closure via reducing H2O2, probably by scavenging, and Ca(2+) levels in guard cells. Moreover, the inhibitive effect of ALA on ABA-induced stomatal closure was further confirmed in the whole plant. Finally, we demonstrated that ALA inhibits stomatal closing, but significantly improves plant drought tolerance. Our results provide valuable information for the promotion of plant production and development of a sustainable low-carbon society.

  15. ALA Inhibits ABA-induced Stomatal Closure via Reducing H2O2 and Ca(2+) Levels in Guard Cells.

    PubMed

    An, Yuyan; Liu, Longbo; Chen, Linghui; Wang, Liangju

    2016-01-01

    5-Aminolevulinic acid (ALA), a newly proved natural plant growth regulator, is well known to improve plant photosynthesis under both normal and stressful conditions. However, its underlying mechanism remains largely unknown. Stomatal closure is one of the major limiting factors for photosynthesis and abscisic acid (ABA) is the most important hormone in provoking stomatal closing. Here, we showed that ALA significantly inhibited ABA-induced stomatal closure using wild-type and ALA-overproducing transgenic Arabidopsis (YHem1). We found that ALA decreased ABA-induced H2O2 and cytosolic Ca(2+) accumulation in guard cells with stomatal bioassay, laser-scanning confocal microscopy and pharmacological methods. The inhibitory effect of ALA on ABA-induced stomatal closure was similar to that of AsA (an important reducing substrate for H2O2 removal), CAT (a H2O2-scavenging enzyme), DPI (an inhibitor of the H2O2-generating NADPH oxidase), EGTA (a Ca-chelating agent), and AlCl3 (an inhibitor of calcium channel). Furthermore, ALA inhibited exogenous H2O2- or Ca(2+)-induced stomatal closure. Taken together, we conclude that ALA inhibits ABA-induced stomatal closure via reducing H2O2, probably by scavenging, and Ca(2+) levels in guard cells. Moreover, the inhibitive effect of ALA on ABA-induced stomatal closure was further confirmed in the whole plant. Finally, we demonstrated that ALA inhibits stomatal closing, but significantly improves plant drought tolerance. Our results provide valuable information for the promotion of plant production and development of a sustainable low-carbon society. PMID:27148309

  16. ALA Inhibits ABA-induced Stomatal Closure via Reducing H2O2 and Ca2+ Levels in Guard Cells

    PubMed Central

    An, Yuyan; Liu, Longbo; Chen, Linghui; Wang, Liangju

    2016-01-01

    5-Aminolevulinic acid (ALA), a newly proved natural plant growth regulator, is well known to improve plant photosynthesis under both normal and stressful conditions. However, its underlying mechanism remains largely unknown. Stomatal closure is one of the major limiting factors for photosynthesis and abscisic acid (ABA) is the most important hormone in provoking stomatal closing. Here, we showed that ALA significantly inhibited ABA-induced stomatal closure using wild-type and ALA-overproducing transgenic Arabidopsis (YHem1). We found that ALA decreased ABA-induced H2O2 and cytosolic Ca2+ accumulation in guard cells with stomatal bioassay, laser-scanning confocal microscopy and pharmacological methods. The inhibitory effect of ALA on ABA-induced stomatal closure was similar to that of AsA (an important reducing substrate for H2O2 removal), CAT (a H2O2-scavenging enzyme), DPI (an inhibitor of the H2O2-generating NADPH oxidase), EGTA (a Ca-chelating agent), and AlCl3 (an inhibitor of calcium channel). Furthermore, ALA inhibited exogenous H2O2- or Ca2+-induced stomatal closure. Taken together, we conclude that ALA inhibits ABA-induced stomatal closure via reducing H2O2, probably by scavenging, and Ca2+ levels in guard cells. Moreover, the inhibitive effect of ALA on ABA-induced stomatal closure was further confirmed in the whole plant. Finally, we demonstrated that ALA inhibits stomatal closing, but significantly improves plant drought tolerance. Our results provide valuable information for the promotion of plant production and development of a sustainable low-carbon society. PMID:27148309

  17. H2O2 inhibits ABA-signaling protein phosphatase HAB1.

    PubMed

    Sridharamurthy, Madhuri; Kovach, Amanda; Zhao, Yang; Zhu, Jian-Kang; Xu, H Eric; Swaminathan, Kunchithapadam; Melcher, Karsten

    2014-01-01

    Due to its ability to be rapidly generated and propagated over long distances, H2O2 is an important second messenger for biotic and abiotic stress signaling in plants. In response to low water potential and high salt concentrations sensed in the roots of plants, the stress hormone abscisic acid (ABA) activates NADPH oxidase to generate H2O2, which is propagated in guard cells in leaves to induce stomatal closure and prevent water loss from transpiration. Using a reconstituted system, we demonstrate that H2O2 reversibly prevents the protein phosphatase HAB1, a key component of the core ABA-signaling pathway, from inhibiting its main target in guard cells, SnRK2.6/OST1 kinase. We have identified HAB1 C186 and C274 as H2O2-sensitive thiols and demonstrate that their oxidation inhibits both HAB1 catalytic activity and its ability to physically associate with SnRK2.6 by formation of intermolecular dimers.

  18. H2O2 Inhibits ABA-Signaling Protein Phosphatase HAB1

    PubMed Central

    Sridharamurthy, Madhuri; Kovach, Amanda; Zhao, Yang; Zhu, Jian-Kang; Xu, H. Eric; Swaminathan, Kunchithapadam; Melcher, Karsten

    2014-01-01

    Due to its ability to be rapidly generated and propagated over long distances, H2O2 is an important second messenger for biotic and abiotic stress signaling in plants. In response to low water potential and high salt concentrations sensed in the roots of plants, the stress hormone abscisic acid (ABA) activates NADPH oxidase to generate H2O2, which is propagated in guard cells in leaves to induce stomatal closure and prevent water loss from transpiration. Using a reconstituted system, we demonstrate that H2O2 reversibly prevents the protein phosphatase HAB1, a key component of the core ABA-signaling pathway, from inhibiting its main target in guard cells, SnRK2.6/OST1 kinase. We have identified HAB1 C186 and C274 as H2O2-sensitive thiols and demonstrate that their oxidation inhibits both HAB1 catalytic activity and its ability to physically associate with SnRK2.6 by formation of intermolecular dimers. PMID:25460914

  19. The Arabidopsis F-box E3 ligase RIFP1 plays a negative role in abscisic acid signalling by facilitating ABA receptor RCAR3 degradation.

    PubMed

    Li, Ying; Zhang, Liang; Li, Dekuan; Liu, Zhibin; Wang, Jianmei; Li, Xufeng; Yang, Yi

    2016-03-01

    The phytohormone abscisic acid (ABA) plays a vital role in plant growth and development. The function of ABA is mediated by a group of newly discovered ABA receptors, named PYRABACTIN RESISTANCE 1/PYR-LIKE/REGULATORY COMPONENTS OF ABA RECEPTORs (PYR1/PYLs/RCARs). Here, we report that an Arabidopsis thaliana F-box protein RCAR3 INTERACTING F-BOX PROTEIN 1 (RIFP1) interacts with ABA receptor (RCAR3) and SCF E3 ligase complex subunits Arabidopsis SKP1-LIKE PROTEINs (ASKs) in vitro and in vivo. The rifp1 mutant plants displayed increased ABA-mediated inhibition of seed germination and water loss of detached leaves, while the overexpression of RIFP1 in Arabidopsis led to plants being insensitive to ABA. Meanwhile, the rifp1 mutant plants showed greater tolerance to water deficit. In addition, the RCAR3 protein level was more stable in the rifp1 mutant plants than in the wild-type plants, indicating that RIFP1 facilitates the proteasome degradation of RCAR3. Accordingly, the loss of RIFP1 increased the transcript levels of several ABA-responsive genes. Taken together, these data indicate that RIFP1 plays a negative role in the RCAR3-mediated ABA signalling pathway and likely functions as an adaptor subunit of the SCF ubiquitin ligase complex to regulate ABA receptor RCAR3 stability. PMID:26386272

  20. ABA-HYPERSENSITIVE BTB/POZ PROTEIN 1 functions as a negative regulator in ABA-mediated inhibition of germination in Arabidopsis.

    PubMed

    Kim, Hani; Kim, Soon-Hee; Seo, Dong Hye; Chung, Sunglan; Kim, Sang-Woo; Lee, Jeong-Soo; Kim, Woo Taek; Lee, Jae-Hoon

    2016-02-01

    To elucidate the contribution of CRL3-ABA-mediated responses, we attempted to find CRL3 substrate receptors involved in ABA signaling. One gene named ABA-HYPERSENSITIVE BTB/POZ PROTEIN 1 (AHT1) was upregulated more than 2.5 times by ABA, and its coding region possessed a BTB/POZ domain, which is the common feature of CRL3 substrate receptors. Loss of AHT1 led to retardation of the germination process, not inhibition of root growth. AHT1 transcripts also increased in response to mannitol, NaCl and drought treatments at the seedling stage and in dry seeds. High expression of AHT1 in dry seeds was inhibited by the defect of ABA signaling components such as ABI1, ABI3 and SRKs indicating that the expression of AHT1 is dependent on ABA signaling. Among bZIP transcription factors participating in ABA signaling, the losses of ABI5/DPBF1, AREB1/ABF2, EEL/DPBF4 and DPBF2/bZIP67 resulted in reduced AHT1 expression, showing that these transcription factors play a positive role in ABA-induced AHT1 expression. While loss of AHT1 did not affect the expression pattern of NCED3, ABI2, SRKs and AREB/ABF genes, it led to hyperinduction of ABI5/DPBF genes such as ABI5/DPBF1, EEL/DPBF4 and AREB3/DPBF3, which are mainly involved in seed development and germination, as well as ABA-inducible genes transactivated by ABI5. Overall, these findings indicate that AHT1 negatively regulates ABA-mediated inhibition of germination, possibly by repressing the expression of a subset of ABI5/DPBF subfamily genes, and that AHT1 may be regulated by a negative feedback process through its linkage with a part of ABI5/DPBF proteins. PMID:26667153

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

    PubMed Central

    Waadt, Rainer; Schroeder, Julian I.

    2016-01-01

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

  2. The Mg-Chelatase H Subunit of Arabidopsis Antagonizes a Group of WRKY Transcription Repressors to Relieve ABA-Responsive Genes of Inhibition[W][OA

    PubMed Central

    Shang, Yi; Yan, Lu; Liu, Zhi-Qiang; Cao, Zheng; Mei, Chao; Xin, Qi; Wu, Fu-Qing; Wang, Xiao-Fang; Du, Shu-Yuan; Jiang, Tao; Zhang, Xiao-Feng; Zhao, Rui; Sun, Hai-Li; Liu, Rui; Yu, Yong-Tao; Zhang, Da-Peng

    2010-01-01

    The phytohormone abscisic acid (ABA) plays a vital role in plant development and response to environmental challenges, but the complex networks of ABA signaling pathways are poorly understood. We previously reported that a chloroplast protein, the magnesium-protoporphyrin IX chelatase H subunit (CHLH/ABAR), functions as a receptor for ABA in Arabidopsis thaliana. Here, we report that ABAR spans the chloroplast envelope and that the cytosolic C terminus of ABAR interacts with a group of WRKY transcription factors (WRKY40, WRKY18, and WRKY60) that function as negative regulators of ABA signaling in seed germination and postgermination growth. WRKY40, a central negative regulator, inhibits expression of ABA-responsive genes, such as ABI5. In response to a high level of ABA signal that recruits WRKY40 from the nucleus to the cytosol and promotes ABAR–WRKY40 interaction, ABAR relieves the ABI5 gene of inhibition by repressing WRKY40 expression. These findings describe a unique ABA signaling pathway from the early signaling events to downstream gene expression. PMID:20543028

  3. Local root abscisic acid (ABA) accumulation depends on the spatial distribution of soil moisture in potato: implications for ABA signalling under heterogeneous soil drying.

    PubMed

    Puértolas, Jaime; Conesa, María R; Ballester, Carlos; Dodd, Ian C

    2015-04-01

    Patterns of root abscisic acid (ABA) accumulation ([ABA]root), root water potential (Ψroot), and root water uptake (RWU), and their impact on xylem sap ABA concentration ([X-ABA]) were measured under vertical partial root-zone drying (VPRD, upper compartment dry, lower compartment wet) and horizontal partial root-zone drying (HPRD, two lateral compartments: one dry, the other wet) of potato (Solanum tuberosum L.). When water was withheld from the dry compartment for 0-10 d, RWU and Ψroot were similarly lower in the dry compartment when soil volumetric water content dropped below 0.22cm(3) cm(-3) for both spatial distributions of soil moisture. However, [ABA]root increased in response to decreasing Ψroot in the dry compartment only for HPRD, resulting in much higher ABA accumulation than in VPRD. The position of the sampled roots (~4cm closer to the surface in the dry compartment of VPRD than in HPRD) might account for this difference, since older (upper) roots may accumulate less ABA in response to decreased Ψroot than younger (deeper) roots. This would explain differences in root ABA accumulation patterns under vertical and horizontal soil moisture gradients reported in the literature. In our experiment, these differences in root ABA accumulation did not influence [X-ABA], since the RWU fraction (and thus ABA export to shoots) from the dry compartment dramatically decreased simultaneously with any increase in [ABA]root. Thus, HPRD might better trigger a long-distance ABA signal than VPRD under conditions allowing simultaneous high [ABA]root and relatively high RWU fraction. PMID:25547916

  4. Local root abscisic acid (ABA) accumulation depends on the spatial distribution of soil moisture in potato: implications for ABA signalling under heterogeneous soil drying

    PubMed Central

    Puértolas, Jaime; Conesa, María R.; Ballester, Carlos; Dodd, Ian C.

    2015-01-01

    Patterns of root abscisic acid (ABA) accumulation ([ABA]root), root water potential (Ψroot), and root water uptake (RWU), and their impact on xylem sap ABA concentration ([X-ABA]) were measured under vertical partial root-zone drying (VPRD, upper compartment dry, lower compartment wet) and horizontal partial root-zone drying (HPRD, two lateral compartments: one dry, the other wet) of potato (Solanum tuberosum L.). When water was withheld from the dry compartment for 0–10 d, RWU and Ψroot were similarly lower in the dry compartment when soil volumetric water content dropped below 0.22cm3 cm–3 for both spatial distributions of soil moisture. However, [ABA]root increased in response to decreasing Ψroot in the dry compartment only for HPRD, resulting in much higher ABA accumulation than in VPRD. The position of the sampled roots (~4cm closer to the surface in the dry compartment of VPRD than in HPRD) might account for this difference, since older (upper) roots may accumulate less ABA in response to decreased Ψroot than younger (deeper) roots. This would explain differences in root ABA accumulation patterns under vertical and horizontal soil moisture gradients reported in the literature. In our experiment, these differences in root ABA accumulation did not influence [X-ABA], since the RWU fraction (and thus ABA export to shoots) from the dry compartment dramatically decreased simultaneously with any increase in [ABA]root. Thus, HPRD might better trigger a long-distance ABA signal than VPRD under conditions allowing simultaneous high [ABA]root and relatively high RWU fraction. PMID:25547916

  5. Local root abscisic acid (ABA) accumulation depends on the spatial distribution of soil moisture in potato: implications for ABA signalling under heterogeneous soil drying.

    PubMed

    Puértolas, Jaime; Conesa, María R; Ballester, Carlos; Dodd, Ian C

    2015-04-01

    Patterns of root abscisic acid (ABA) accumulation ([ABA]root), root water potential (Ψroot), and root water uptake (RWU), and their impact on xylem sap ABA concentration ([X-ABA]) were measured under vertical partial root-zone drying (VPRD, upper compartment dry, lower compartment wet) and horizontal partial root-zone drying (HPRD, two lateral compartments: one dry, the other wet) of potato (Solanum tuberosum L.). When water was withheld from the dry compartment for 0-10 d, RWU and Ψroot were similarly lower in the dry compartment when soil volumetric water content dropped below 0.22cm(3) cm(-3) for both spatial distributions of soil moisture. However, [ABA]root increased in response to decreasing Ψroot in the dry compartment only for HPRD, resulting in much higher ABA accumulation than in VPRD. The position of the sampled roots (~4cm closer to the surface in the dry compartment of VPRD than in HPRD) might account for this difference, since older (upper) roots may accumulate less ABA in response to decreased Ψroot than younger (deeper) roots. This would explain differences in root ABA accumulation patterns under vertical and horizontal soil moisture gradients reported in the literature. In our experiment, these differences in root ABA accumulation did not influence [X-ABA], since the RWU fraction (and thus ABA export to shoots) from the dry compartment dramatically decreased simultaneously with any increase in [ABA]root. Thus, HPRD might better trigger a long-distance ABA signal than VPRD under conditions allowing simultaneous high [ABA]root and relatively high RWU fraction.

  6. Abscisic acid (ABA) sensitivity regulates desiccation tolerance in germinated Arabidopsis seeds.

    PubMed

    Maia, Julio; Dekkers, Bas J W; Dolle, Miranda J; Ligterink, Wilco; Hilhorst, Henk W M

    2014-07-01

    During germination, orthodox seeds lose their desiccation tolerance (DT) and become sensitive to extreme drying. Yet, DT can be rescued, in a well-defined developmental window, by the application of a mild osmotic stress before dehydration. A role for abscisic acid (ABA) has been implicated in this stress response and in DT re-establishment. However, the path from the sensing of an osmotic cue and its signaling to DT re-establishment is still largely unknown. Analyses of DT, ABA sensitivity, ABA content and gene expression were performed in desiccation-sensitive (DS) and desiccation-tolerant Arabidopsis thaliana seeds. Furthermore, loss and re-establishment of DT in germinated Arabidopsis seeds was studied in ABA-deficient and ABA-insensitive mutants. We demonstrate that the developmental window in which DT can be re-established correlates strongly with the window in which ABA sensitivity is still present. Using ABA biosynthesis and signaling mutants, we show that this hormone plays a key role in DT re-establishment. Surprisingly, re-establishment of DT depends on the modulation of ABA sensitivity rather than enhanced ABA content. In addition, the evaluation of several ABA-insensitive mutants, which can still produce normal desiccation-tolerant seeds, but are impaired in the re-establishment of DT, shows that the acquisition of DT during seed development is genetically different from its re-establishment during germination.

  7. Role of abscisic acid (ABA) and Arabidopsis thaliana ABA-insensitive loci in low water potential-induced ABA and proline accumulation.

    PubMed

    Verslues, Paul E; Bray, Elizabeth A

    2006-01-01

    The mechanisms by which plants respond to reduced water availability (low water potential) include both ABA-dependent and ABA-independent processes. Pro accumulation and osmotic adjustment are two important traits for which the mechanisms of regulation by low water potential, and the involvement of ABA, is not well understood. The ABA-deficient mutant, aba2-1, was used to investigate the regulatory role of ABA in low water potential-induced Pro accumulation and osmotic adjustment in seedlings of Arabidopsis thaliana. Low water potential-induced Pro accumulation required wild-type levels of ABA, as well as a change in ABA sensitivity or ABA-independent events. Osmotic adjustment, in contrast, occurred independently of ABA accumulation in aba2-1. Quantification of low water potential-induced ABA and Pro accumulation in five ABA-insensitive mutants, abi1-1, abi2-1, abi3, abi4, and abi5, revealed that abi4 had increased Pro accumulation at low water potential, but a reduced response to exogenous ABA. Both of these responses were modified by sucrose treatment, indicating that ABI4 has a role in connecting ABA and sugar in regulating Pro accumulation. Of the other abi mutants, only abi1 had reduced Pro accumulation in response to low water potential and ABA application. It was also observed that abi1-1 and abi2-1 had increased ABA accumulation. The involvement of these loci in feedback regulation of ABA accumulation may occur through an effect on ABA catabolism or conjugation. These data provide new information on the function of ABA in seedlings exposed to low water potential and define new roles for three of the well-studied abi loci.

  8. The effects of abscisic acid (ABA) addition on cadmium accumulation of two ecotypes of Solanum photeinocarpum.

    PubMed

    Wang, Jin; Lin, Lijin; Luo, Li; Liao, Ming'an; Lv, Xiulan; Wang, Zhihui; Liang, Dong; Xia, Hui; Wang, Xun; Lai, Yunsong; Tang, Yi

    2016-03-01

    The study of the effects of exogenous abscisic acid (ABA) addition on cadmium (Cd) accumulation of two ecotypes (mining and farmland) of Solanum photeinocarpum was operated through a pot experiment. The results showed that the biomass and chlorophyll content of the two ecotypes of S. photeinocarpum increased with increasing ABA concentration. Applying exogenous ABA increased Cd content in the two ecotypes of S. photeinocarpum. The maximum Cd contents in shoots of the two ecotypes of S. photeinocarpum were obtained at 20 μmol/L ABA; shoot Cd contents respectively for the mining and farmland ecotypes were 33.92 and 24.71% higher than those for the control. Applying exogenous ABA also increased Cd extraction by the two ecotypes of S. photeinocarpum, and the highest Cd extraction was obtained at 20 μmol/L ABA with 569.42 μg/plant in shoots of the mining ecotype and 520.51 μg/plant in shoots of the farmland ecotype respectively. Therefore, exogenous ABA can be used for enhancing the Cd extraction ability of S. photeinocarpum, and 20 μmol/L ABA was the optimal dose. PMID:26899030

  9. The effects of abscisic acid (ABA) addition on cadmium accumulation of two ecotypes of Solanum photeinocarpum.

    PubMed

    Wang, Jin; Lin, Lijin; Luo, Li; Liao, Ming'an; Lv, Xiulan; Wang, Zhihui; Liang, Dong; Xia, Hui; Wang, Xun; Lai, Yunsong; Tang, Yi

    2016-03-01

    The study of the effects of exogenous abscisic acid (ABA) addition on cadmium (Cd) accumulation of two ecotypes (mining and farmland) of Solanum photeinocarpum was operated through a pot experiment. The results showed that the biomass and chlorophyll content of the two ecotypes of S. photeinocarpum increased with increasing ABA concentration. Applying exogenous ABA increased Cd content in the two ecotypes of S. photeinocarpum. The maximum Cd contents in shoots of the two ecotypes of S. photeinocarpum were obtained at 20 μmol/L ABA; shoot Cd contents respectively for the mining and farmland ecotypes were 33.92 and 24.71% higher than those for the control. Applying exogenous ABA also increased Cd extraction by the two ecotypes of S. photeinocarpum, and the highest Cd extraction was obtained at 20 μmol/L ABA with 569.42 μg/plant in shoots of the mining ecotype and 520.51 μg/plant in shoots of the farmland ecotype respectively. Therefore, exogenous ABA can be used for enhancing the Cd extraction ability of S. photeinocarpum, and 20 μmol/L ABA was the optimal dose.

  10. Structural basis for basal activity and autoactivation of abscisic acid (ABA) signaling SnRK2 kinases

    SciTech Connect

    Ng, Ley-Moy; Soon, Fen-Fen; Zhou, X. Edward; West, Graham M.; Kovach, Amanda; Suino-Powell, Kelly M.; Chalmers, Michael J.; Li, Jun; Yong, Eu-Leong; Zhu, Jian-Kang; Griffin, Patrick R.; Melcher, Karsten; Xu, H. Eric

    2014-10-02

    Abscisic acid (ABA) is an essential hormone that controls plant growth, development, and responses to abiotic stresses. Central for ABA signaling is the ABA-mediated autoactivation of three monomeric Snf1-related kinases (SnRK2.2, -2.3, and -2.6). In the absence of ABA, SnRK2s are kept in an inactive state by forming physical complexes with type 2C protein phosphatases (PP2Cs). Upon relief of this inhibition, SnRK2 kinases can autoactivate through unknown mechanisms. Here, we report the crystal structures of full-length Arabidopsis thaliana SnRK2.3 and SnRK2.6 at 1.9- and 2.3-{angstrom} resolution, respectively. The structures, in combination with biochemical studies, reveal a two-step mechanism of intramolecular kinase activation that resembles the intermolecular activation of cyclin-dependent kinases. First, release of inhibition by PP2C allows the SnRK2s to become partially active because of an intramolecular stabilization of the catalytic domain by a conserved helix in the kinase regulatory domain. This stabilization enables SnRK2s to gain full activity by activation loop autophosphorylation. Autophosphorylation is more efficient in SnRK2.6, which has higher stability than SnRK2.3 and has well-structured activation loop phosphate acceptor sites that are positioned next to the catalytic site. Together, these data provide a structural framework that links ABA-mediated release of PP2C inhibition to activation of SnRK2 kinases.

  11. Structural basis for basal activity and autoactivation of abscisic acid (ABA) signaling SnRK2 kinases

    PubMed Central

    Ng, Ley-Moy; Soon, Fen-Fen; Zhou, X. Edward; West, Graham M.; Kovach, Amanda; Suino-Powell, Kelly M.; Chalmers, Michael J.; Li, Jun; Yong, Eu-Leong; Zhu, Jian-Kang; Griffin, Patrick R.; Melcher, Karsten; Xu, H. Eric

    2011-01-01

    Abscisic acid (ABA) is an essential hormone that controls plant growth, development, and responses to abiotic stresses. Central for ABA signaling is the ABA-mediated autoactivation of three monomeric Snf1-related kinases (SnRK2.2, -2.3, and -2.6). In the absence of ABA, SnRK2s are kept in an inactive state by forming physical complexes with type 2C protein phosphatases (PP2Cs). Upon relief of this inhibition, SnRK2 kinases can autoactivate through unknown mechanisms. Here, we report the crystal structures of full-length Arabidopsis thaliana SnRK2.3 and SnRK2.6 at 1.9- and 2.3-Å resolution, respectively. The structures, in combination with biochemical studies, reveal a two-step mechanism of intramolecular kinase activation that resembles the intermolecular activation of cyclin-dependent kinases. First, release of inhibition by PP2C allows the SnRK2s to become partially active because of an intramolecular stabilization of the catalytic domain by a conserved helix in the kinase regulatory domain. This stabilization enables SnRK2s to gain full activity by activation loop autophosphorylation. Autophosphorylation is more efficient in SnRK2.6, which has higher stability than SnRK2.3 and has well-structured activation loop phosphate acceptor sites that are positioned next to the catalytic site. Together, these data provide a structural framework that links ABA-mediated release of PP2C inhibition to activation of SnRK2 kinases. PMID:22160701

  12. Differences in phosphatidic acid signalling and metabolism between ABA and GA treatments of barley aleurone cells.

    PubMed

    Villasuso, Ana Laura; Di Palma, Maria A; Aveldaño, Marta; Pasquaré, Susana J; Racagni, Graciela; Giusto, Norma M; Machado, Estela E

    2013-04-01

    Phosphatidic acid (PA) is the common lipid product in abscisic acid (ABA) and gibberellic acid (GA) response. In this work we investigated the lipid metabolism in response to both hormones. We could detect an in vivo phospholipase D activity (PLD, EC 3.1.4.4). This PLD produced [(32)P]PA (phosphatidic acid) rapidly (minutes) in the presence of ABA, confirming PA involvement in signal transduction, and transiently, indicating rapid PA removal after generation. The presence of PA removal by phosphatidate phosphatase 1 and 2 isoforms (E.C. 3.1.3.4) was verified in isolated aleurone membranes in vitro, the former but not the latter being specifically responsive to the presence of GA or ABA. The in vitro DGPP phosphatase activity was not modified by short time incubation with GA or ABA while the in vitro PA kinase - that allows the production of 18:2-DGPP from 18:2-PA - is stimulated by ABA. The long term effects (24 h) of ABA or GA on lipid and fatty acid composition of aleurone layer cells were then investigated. An increase in PC and, to a lesser extent, in PE levels is the consequence of both hormone treatments. ABA, in aleurone layer cells, specifically activates a PLD whose product, PA, could be the substrate of PAP1 and/or PAK activities. Neither PLD nor PAK activation can be monitored by GA treatment. The increase in PAP1 activity monitored after ABA or GA treatment might participate in the increase in PC level observed after 24 h hormone incubation.

  13. Abscisic acid inhibits root growth in Arabidopsis through ethylene biosynthesis.

    PubMed

    Luo, Xingju; Chen, Zhizhong; Gao, Junping; Gong, Zhizhong

    2014-07-01

    When first discovered in 1963, abscisic acid (ABA) was called abscisin II because it promotes abscission. Later, researchers found that ABA accelerates abscission via ethylene. In Arabidopsis, previous studies have shown that high concentrations of ABA inhibit root growth through ethylene signaling but not ethylene production. In the present study in Arabidopsis, we found that ABA inhibits root growth by promoting ethylene biosynthesis. The ethylene biosynthesis inhibitor L-α-(2-aminoethoxyvinyl)-glycine reduces ABA inhibition of root growth, and multiple mutants of ACS (1-aminocyclopropane-1-carboxylate synthase) are more resistant to ABA in terms of root growth than the wild-type is. Two ABA-activated calcium-dependent protein kinases, CPK4 and CPK11, phosphorylate the C-terminus of ACS6 and increase the stability of ACS6 in ethylene biosynthesis. Plants expressing an ACS6 mutant that mimics the phosphorylated form of ACS6 produce more ethylene than the wild-type. Our results reveal an important mechanism by which ABA promotes ethylene production. This mechanism may be highly conserved among higher plants.

  14. ABA-Mediated Inhibition of Germination Is Related to the Inhibition of Genes Encoding Cell-Wall Biosynthetic and Architecture: Modifying Enzymes and Structural Proteins in Medicago truncatula Embryo Axis

    PubMed Central

    Gimeno-Gilles, Christine; Lelièvre, Eric; Viau, Laure; Malik-Ghulam, Mustafa; Ricoult, Claudie; Niebel, Andreas; Leduc, Nathalie; Limami, Anis M.

    2009-01-01

    Radicle emergence and reserves mobilization are two distinct programmes that are thought to control germination. Both programs are influenced by abscissic acid (ABA) but how this hormone controls seed germination is still poorly known. Phenotypic and microscopic observations of the embryo axis of Medicago truncatula during germination in mitotic inhibition condition triggered by 10 μM oryzalin showed that cell division was not required to allow radicle emergence. A suppressive subtractive hybridization showed that more than 10% of up-regulated genes in the embryo axis encoded proteins related to cell-wall biosynthesis. The expression of α-expansins, pectin-esterase, xylogucan-endotransglycosidase, cellulose synthase, and extensins was monitored in the embryo axis of seeds germinated on water, constant and transitory ABA. These genes were overexpressed before completion of germination in the control and strongly inhibited by ABA. The expression was re-established in the ABA transitory-treatment after the seeds were transferred back on water and proceeded to germination. This proves these genes as contributors to the completion of germination and strengthen the idea that cell-wall loosening and remodeling in relation to cell expansion in the embryo axis is a determinant feature in germination. Our results also showed that ABA controls germination through the control of radicle emergence, namely by inhibiting cell-wall loosening and expansion. PMID:19529818

  15. Salicylic acid antagonizes abscisic acid inhibition of shoot growth and cell cycle progression in rice

    NASA Astrophysics Data System (ADS)

    Meguro, Ayano; Sato, Yutaka

    2014-04-01

    We analysed effects of abscisic acid (ABA, a negative regulatory hormone), alone and in combination with positive or neutral hormones, including salicylic acid (SA), on rice growth and expression of cell cycle-related genes. ABA significantly inhibited shoot growth and induced expression of OsKRP4, OsKRP5, and OsKRP6. A yeast two-hybrid assay showed that OsKRP4, OsKRP5, and OsKRP6 interacted with OsCDKA;1 and/or OsCDKA;2. When SA was simultaneously supplied with ABA, the antagonistic effect of SA completely blocked ABA inhibition. SA also blocked ABA inhibition of DNA replication and thymidine incorporation in the shoot apical meristem. These results suggest that ABA arrests cell cycle progression by inducing expression of OsKRP4, OsKRP5, and OsKRP6, which inhibit the G1/S transition, and that SA antagonizes ABA by blocking expression of OsKRP genes.

  16. Identification and mechanism of ABA receptor antagonism

    SciTech Connect

    Melcher, Karsten; Xu, Yong; Ng, Ley-Moy; Zhou, X. Edward; Soon, Fen-Fen; Chinnusamy, Viswanathan; Suino-Powell, Kelly M; Kovach, Amanda; Tham, Fook S.; Cutler, Sean R.; Li, Jun; Yong, Eu-Leong; Zhu, Jian-Kang; Xu, H. Eric

    2010-11-11

    The phytohormone abscisic acid (ABA) functions through a family of fourteen PYR/PYL receptors, which were identified by resistance to pyrabactin, a synthetic inhibitor of seed germination. ABA activates these receptors to inhibit type 2C protein phosphatases, such as ABI1, yet it remains unclear whether these receptors can be antagonized. Here we demonstrate that pyrabactin is an agonist of PYR1 and PYL1 but is unexpectedly an antagonist of PYL2. Crystal structures of the PYL2-pyrabactin and PYL1-pyrabactin-ABI1 complexes reveal the mechanism responsible for receptor-selective activation and inhibition, which enables us to design mutations that convert PYL1 to a pyrabactin-inhibited receptor and PYL2 to a pyrabactin-activated receptor and to identify new pyrabactin-based ABA receptor agonists. Together, our results establish a new concept of ABA receptor antagonism, illustrate its underlying mechanisms and provide a rational framework for discovering novel ABA receptor ligands.

  17. Difference in Abscisic Acid Perception Mechanisms between Closure Induction and Opening Inhibition of Stomata1[W][OPEN

    PubMed Central

    Yin, Ye; Adachi, Yuji; Ye, Wenxiu; Hayashi, Maki; Nakamura, Yoshimasa; Kinoshita, Toshinori; Mori, Izumi C.; Murata, Yoshiyuki

    2013-01-01

    Abscisic acid (ABA) induces stomatal closure and inhibits light-induced stomatal opening. The mechanisms in these two processes are not necessarily the same. It has been postulated that the ABA receptors involved in opening inhibition are different from those involved in closure induction. Here, we provide evidence that four recently identified ABA receptors (PYRABACTIN RESISTANCE1 [PYR1], PYRABACTIN RESISTANCE-LIKE1 [PYL1], PYL2, and PYL4) are not sufficient for opening inhibition in Arabidopsis (Arabidopsis thaliana). ABA-induced stomatal closure was impaired in the pyr1/pyl1/pyl2/pyl4 quadruple ABA receptor mutant. ABA inhibition of the opening of the mutant’s stomata remained intact. ABA did not induce either the production of reactive oxygen species and nitric oxide or the alkalization of the cytosol in the quadruple mutant, in accordance with the closure phenotype. Whole cell patch-clamp analysis of inward-rectifying K+ current in guard cells showed a partial inhibition by ABA, indicating that the ABA sensitivity of the mutant was not fully impaired. ABA substantially inhibited blue light-induced phosphorylation of H+-ATPase in guard cells in both the mutant and the wild type. On the other hand, in a knockout mutant of the SNF1-related protein kinase, srk2e, stomatal opening and closure, reactive oxygen species and nitric oxide production, cytosolic alkalization, inward-rectifying K+ current inactivation, and H+-ATPase phosphorylation were not sensitive to ABA. PMID:23946352

  18. Inhibition of Abscisic Acid Biosynthesis in Cercospora rosicola by Inhibitors of Gibberellin Biosynthesis and Plant Growth Retardants

    PubMed Central

    Norman, Shirley M.; Poling, Stephen M.; Maier, Vincent P.; Orme, Edward D.

    1983-01-01

    The fungus Cercospora rosicola produces abscisic acid (ABA) as a secondary metabolite. We developed a convenient system using this fungus to determine the effects of compounds on the biosynthesis of ABA. Inasmuch as ABA and the gibberellins (GAs) both arise via the isoprenoid pathway, it was of interest to determine if inhibitors of GA biosynthesis affect ABA biosynthesis. All five putative inhibitors of GA biosynthesis tested inhibited ABA biosynthesis. Several plant growth retardants with poorly understood actions in plants were also tested; of these, six inhibited ABA biosynthesis to varying degrees and two had no effect. Effects of plant growth retardants on various branches of the isoprenoid biosynthetic pathway may help to explain some of the diverse and unexpected results reported for these compounds. Knowledge that certain inhibitors of GA biosynthesis also have the ability to inhibit ABA biosynthesis in C. rosicola indicates the need for further studies in plants on the mode of action of these compounds. PMID:16662775

  19. Seed dormancy and ABA signaling

    PubMed Central

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

    2009-01-01

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

  20. Phosphatidic acid inhibits blue light-induced stomatal opening via inhibition of protein phosphatase 1 [corrected].

    PubMed

    Takemiya, Atsushi; Shimazaki, Ken-ichiro

    2010-08-01

    Stomata open in response to blue light under a background of red light. The plant hormone abscisic acid (ABA) inhibits blue light-dependent stomatal opening, an effect essential for promoting stomatal closure in the daytime to prevent water loss. However, the mechanisms and molecular targets of this inhibition in the blue light signaling pathway remain unknown. Here, we report that phosphatidic acid (PA), a phospholipid second messenger produced by ABA in guard cells, inhibits protein phosphatase 1 (PP1), a positive regulator of blue light signaling, and PA plays a role in stimulating stomatal closure in Vicia faba. Biochemical analysis revealed that PA directly inhibited the phosphatase activity of the catalytic subunit of V. faba PP1 (PP1c) in vitro. PA inhibited blue light-dependent stomatal opening but did not affect red light- or fusicoccin-induced stomatal opening. PA also inhibited blue light-dependent H(+) pumping and phosphorylation of the plasma membrane H(+)-ATPase. However, PA did not inhibit the autophosphorylation of phototropins, blue light receptors for stomatal opening. Furthermore, 1-butanol, a selective inhibitor of phospholipase D, which produces PA via hydrolysis of phospholipids, diminished the ABA-induced inhibition of blue light-dependent stomatal opening and H(+) pumping. We also show that hydrogen peroxide and nitric oxide, which are intermediates in ABA signaling, inhibited the blue light responses of stomata and that 1-butanol diminished these inhibitions. From these results, we conclude that PA inhibits blue light signaling in guard cells by PP1c inhibition, accelerating stomatal closure, and that PP1 is a cross talk point between blue light and ABA signaling pathways in guard cells.

  1. An ABA-increased interaction of the PYL6 ABA receptor with MYC2 Transcription Factor: A putative link of ABA and JA signaling

    PubMed Central

    Aleman, Fernando; Yazaki, Junshi; Lee, Melissa; Takahashi, Yohei; Kim, Alice Y.; Li, Zixing; Kinoshita, Toshinori; Ecker, Joseph R.; Schroeder, Julian I.

    2016-01-01

    Abscisic acid (ABA) is a plant hormone that mediates abiotic stress tolerance and regulates growth and development. ABA binds to members of the PYL/RCAR ABA receptor family that initiate signal transduction inhibiting type 2C protein phosphatases. Although crosstalk between ABA and the hormone Jasmonic Acid (JA) has been shown, the molecular entities that mediate this interaction have yet to be fully elucidated. We report a link between ABA and JA signaling through a direct interaction of the ABA receptor PYL6 (RCAR9) with the basic helix-loop-helix transcription factor MYC2. PYL6 and MYC2 interact in yeast two hybrid assays and the interaction is enhanced in the presence of ABA. PYL6 and MYC2 interact in planta based on bimolecular fluorescence complementation and co-immunoprecipitation of the proteins. Furthermore, PYL6 was able to modify transcription driven by MYC2 using JAZ6 and JAZ8 DNA promoter elements in yeast one hybrid assays. Finally, pyl6 T-DNA mutant plants show an increased sensitivity to the addition of JA along with ABA in cotyledon expansion experiments. Overall, the present study identifies a direct mechanism for transcriptional modulation mediated by an ABA receptor different from the core ABA signaling pathway, and a putative mechanistic link connecting ABA and JA signaling pathways. PMID:27357749

  2. An ABA-mimicking ligand that reduces water loss and promotes drought resistance in plants

    PubMed Central

    Cao, Minjie; Liu, Xue; Zhang, Yan; Xue, Xiaoqian; Zhou, X Edward; Melcher, Karsten; Gao, Pan; Wang, Fuxing; Zeng, Liang; Zhao, Yang; Zhao, Yang; Deng, Pan; Zhong, Dafang; Zhu, Jian-Kang; Xu, H Eric; Xu, Yong

    2013-01-01

    Abscisic acid (ABA) is the most important hormone for plants to resist drought and other abiotic stresses. ABA binds directly to the PYR/PYL family of ABA receptors, resulting in inhibition of type 2C phosphatases (PP2C) and activation of downstream ABA signaling. It is envisioned that intervention of ABA signaling by small molecules could help plants to overcome abiotic stresses such as drought, cold and soil salinity. However, chemical instability and rapid catabolism by plant enzymes limit the practical application of ABA itself. Here we report the identification of a small molecule ABA mimic (AM1) that acts as a potent activator of multiple members of the family of ABA receptors. In Arabidopsis, AM1 activates a gene network that is highly similar to that induced by ABA. Treatments with AM1 inhibit seed germination, prevent leaf water loss, and promote drought resistance. We solved the crystal structure of AM1 in complex with the PYL2 ABA receptor and the HAB1 PP2C, which revealed that AM1 mediates a gate-latch-lock interacting network, a structural feature that is conserved in the ABA-bound receptor/PP2C complex. Together, these results demonstrate that a single small molecule ABA mimic can activate multiple ABA receptors and protect plants from water loss and drought stress. Moreover, the AM1 complex crystal structure provides a structural basis for designing the next generation of ABA-mimicking small molecules. PMID:23835477

  3. ABA Inhibits Embryo Cell Expansion and Early Cell Division Events During Coffee (Coffea arabica ‘Rubi’) Seed Germination

    PubMed Central

    Da Silva, E. A. Amaral; Toorop, Peter E.; Van Lammeren, André A. M.; Hilhorst, Henk W. M.

    2008-01-01

    Background and Aims Coffee seed germination represents an interplay between the embryo and the surrounding endosperm. A sequence of events in both parts of the seed determines whether germination will be successful or not. Following previous studies, the aim here was to further characterize the morphology of endosperm degradation and embryo growth with respect to morphology and cell cycle, and the influence of abscisic acid on these processes. Methods Growth of cells in a fixed region of the axis was quantified from light micrographs. Cell cycle events were measured by flow cytometry and by immunocytochemistry, using antibodies against β-tubulin. Aspects of the endosperm were visualized by light and scanning electron microscopy. Key Results The embryonic axis cells grew initially by isodiametric expansion. This event coincided with reorientation and increase in abundance of microtubules and with accumulation of β-tubulin. Radicle protrusion was characterized by a shift from isodiametric expansion to elongation of radicle cells and further accumulation of β-tubulin. Early cell division events started prior to radicle protrusion. Abscisic acid decreased the abundance of microtubules and inhibited the growth of the embryo cells, the reorganization of the microtubules, DNA replication in the embryonic axis, the formation of a protuberance and the completion of germination. The endosperm cap cells had smaller and thinner cell walls than the rest of the endosperm. Cells in the endosperm cap displayed compression followed by loss of cell integrity and the appearance of a protuberance prior to radicle protrusion. Conclusions Coffee seed germination is the result of isodiametric growth of the embryo followed by elongation, at the expense of integrity of endosperm cap cells. The cell cycle, including cell division, is initiated prior to radicle protrusion. ABA inhibits expansion of the embryo, and hence subsequent events, including germination. PMID:18617534

  4. Fruit load induces changes in global gene expression and in abscisic acid (ABA) and indole acetic acid (IAA) homeostasis in citrus buds

    PubMed Central

    Shalom, Liron; Samuels, Sivan; Zur, Naftali; Shlizerman, Lyudmila; Doron-Faigenboim, Adi; Blumwald, Eduardo; Sadka, Avi

    2014-01-01

    Many fruit trees undergo cycles of heavy fruit load (ON-Crop) in one year, followed by low fruit load (OFF-Crop) the following year, a phenomenon known as alternate bearing (AB). The mechanism by which fruit load affects flowering induction during the following year (return bloom) is still unclear. Although not proven, it is commonly accepted that the fruit or an organ which senses fruit presence generates an inhibitory signal that moves into the bud and inhibits apical meristem transition. Indeed, fruit removal from ON-Crop trees (de-fruiting) induces return bloom. Identification of regulatory or metabolic processes modified in the bud in association with altered fruit load might shed light on the nature of the AB signalling process. The bud transcriptome of de-fruited citrus trees was compared with those of ON- and OFF-Crop trees. Fruit removal resulted in relatively rapid changes in global gene expression, including induction of photosynthetic genes and proteins. Altered regulatory mechanisms included abscisic acid (ABA) metabolism and auxin polar transport. Genes of ABA biosynthesis were induced; however, hormone analyses showed that the ABA level was reduced in OFF-Crop buds and in buds shortly following fruit removal. Additionally, genes associated with Ca2+-dependent auxin polar transport were remarkably induced in buds of OFF-Crop and de-fruited trees. Hormone analyses showed that auxin levels were reduced in these buds as compared with ON-Crop buds. In view of the auxin transport autoinhibition theory, the possibility that auxin distribution plays a role in determining bud fate is discussed. PMID:24706719

  5. Fruit load induces changes in global gene expression and in abscisic acid (ABA) and indole acetic acid (IAA) homeostasis in citrus buds.

    PubMed

    Shalom, Liron; Samuels, Sivan; Zur, Naftali; Shlizerman, Lyudmila; Doron-Faigenboim, Adi; Blumwald, Eduardo; Sadka, Avi

    2014-07-01

    Many fruit trees undergo cycles of heavy fruit load (ON-Crop) in one year, followed by low fruit load (OFF-Crop) the following year, a phenomenon known as alternate bearing (AB). The mechanism by which fruit load affects flowering induction during the following year (return bloom) is still unclear. Although not proven, it is commonly accepted that the fruit or an organ which senses fruit presence generates an inhibitory signal that moves into the bud and inhibits apical meristem transition. Indeed, fruit removal from ON-Crop trees (de-fruiting) induces return bloom. Identification of regulatory or metabolic processes modified in the bud in association with altered fruit load might shed light on the nature of the AB signalling process. The bud transcriptome of de-fruited citrus trees was compared with those of ON- and OFF-Crop trees. Fruit removal resulted in relatively rapid changes in global gene expression, including induction of photosynthetic genes and proteins. Altered regulatory mechanisms included abscisic acid (ABA) metabolism and auxin polar transport. Genes of ABA biosynthesis were induced; however, hormone analyses showed that the ABA level was reduced in OFF-Crop buds and in buds shortly following fruit removal. Additionally, genes associated with Ca(2+)-dependent auxin polar transport were remarkably induced in buds of OFF-Crop and de-fruited trees. Hormone analyses showed that auxin levels were reduced in these buds as compared with ON-Crop buds. In view of the auxin transport autoinhibition theory, the possibility that auxin distribution plays a role in determining bud fate is discussed.

  6. A novel role of PR2 in abscisic acid (ABA) mediated, pathogen-induced callose deposition in Arabidopsis thaliana.

    PubMed

    Oide, Shinichi; Bejai, Sarosh; Staal, Jens; Guan, Na; Kaliff, Maria; Dixelius, Christina

    2013-12-01

    Pathogenesis-related protein 2 (PR2) is known to play a major role in plant defense and general stress responses. Resistance against the fungal pathogen Leptosphaeria maculans in Arabidopsis requires abscisic acid (ABA), which promotes the deposition of callose, a β-1,3-glucan polymer. Here, we examined the role of PR2 in callose deposition in relation to ABA treatment and challenge with L. maculans and Pseudomonas syringae. Characterization of PR2-overexpressing plants and the knockout line indicated that PR2 negatively affects callose deposition. Recombinant PR2 purified from Pichia pastoris showed callose-degrading activity, and a considerable reduction in the callose-degrading activity was observed in the leaf extract of the PR2 knockout line compared with the wild-type. ABA pretreatment before challenge with L. maculans concomitantly repressed PR2 and enhanced callose accumulation. Likewise, overexpression of an ABA biosynthesis gene NCED3 resulted in reduced PR2 expression and increased callose deposition. We propose that ABA promotes callose deposition through the transcriptional repression of PR2 in Arabidopsis challenged by L. maculans and P. syringae. Callose by itself is likely to act antagonistically on salicylic acid (SA) defense signaling, suggesting that PR2 may function as a modulator of callose- and SA-dependent defense responses.

  7. Effects of molybdenum on expression of cold-responsive genes in abscisic acid (ABA)-dependent and ABA-independent pathways in winter wheat under low-temperature stress

    PubMed Central

    Sun, Xuecheng; Hu, Chengxiao; Tan, Qilin; Liu, Jinshan; Liu, Hongen

    2009-01-01

    Background and Aims Molybdenum (Mo) is an essential trace element for higher plants. It has been shown that application of Mo enhances the cold resistance of winter wheat. In order to improve our understanding of the molecular mechanisms of cold resistance arising from application of Mo in winter wheat, investigations were made regarding the transcription of cold-responsive (COR) genes in abscisic acid (ABA)-dependent and ABA-independent pathways in winter wheat regulated by Mo application under low-temperature stress. Methods Two cultivars of winter wheat (Triticum aestivum), Mo-efficient cultivar ‘97003’ and Mo-inefficient cultivar ‘97014’, were grown in control (−Mo) and Mo fertilizer (+Mo) treatments for 40 d at 15/12 °C (day/night), and the temperature was then reduced to 5/2 °C (day/night) to create low-temperature stress. Aldehyde oxidase (AO) activities, ABA contents, the transcripts of basic leucine zipper (bZIP)-type transcription factor (TF) genes, ABA-dependent COR genes, CBF/DREB transcription factor genes and ABA-independent COR genes were investigated at 0, 3, 6 and 48 h post cold stress. Key Results Mo application significantly increased AO activity, ABA levels, and expression of bZIP-type TF genes (Wlip19 and Wabi5) and ABA-dependent COR genes (Wrab15, Wrab17, Wrab18 and Wrab19). Mo application increased expression levels of CBF/DREB transcription factor genes (TaCBF and Wcbf2-1) and ABA-independent COR genes (Wcs120, Wcs19, Wcor14 and Wcor15) after 3 and 6 h exposure to low temperature. Conclusions Mo might regulate the expression of ABA-dependent COR genes through the pathway: Mo → AO → ABA → bZIP → ABA-dependent COR genes in winter wheat. The response of the ABA-dependent pathway to Mo was prior to that of the ABA-independent pathway. Similarities and differences between the Mo-efficient and Mo-inefficient wheat cultivars in response to Mo under cold stress are discussed. PMID:19491090

  8. Exogenous abscisic acid application decreases cadmium accumulation in Arabidopsis plants, which is associated with the inhibition of IRT1-mediated cadmium uptake

    PubMed Central

    Fan, Shi Kai; Fang, Xian Zhi; Guan, Mei Yan; Ye, Yi Quan; Lin, Xian Yong; Du, Shao Ting; Jin, Chong Wei

    2014-01-01

    Cadmium (Cd) contamination of agricultural soils is an increasingly serious problem. Measures need to be developed to minimize Cd entering the human food chain from contaminated soils. We report here that, under Cd exposure condition, application with low doses of (0.1–0.5 μM) abscisic acid (ABA) clearly inhibited Cd uptake by roots and decreased Cd level in Arabidopsis wild-type plants (Col-0). Expression of IRT1 in roots was also strongly inhibited by ABA treatment. Decrease in Cd uptake and the inhibition of IRT1 expression were clearly lesser pronounced in an ABA-insensitive double mutant snrk2.2/2.3 than in the Col-0 in response to ABA application. The ABA-decreased Cd uptake was found to correlate with the ABA-inhibited IRT1 expression in the roots of Col-0 plants fed two different levels of iron. Furthermore, the Cd uptake of irt1 mutants was barely affected by ABA application. These results indicated that inhibition of IRT1 expression is involved in the decrease of Cd uptake in response to exogenous ABA application. Interestingly, ABA application increased the iron level in both Col-0 plants and irt1 mutants, suggesting that ABA-increased Fe acquisition does not depend on the IRT1 function, but on the contrary, the ABA-mediated inhibition of IRT1 expression may be due to the elevation of iron level in plants. From our results, we concluded that ABA application might increase iron acquisition, followed by the decrease in Cd uptake by inhibition of IRT1 activity. Thus, for crop production in Cd contaminated soils, developing techniques based on ABA application potentially is a promising approach for reducing Cd accumulation in edible organs in plants. PMID:25566293

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2014-10-01

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

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

    PubMed Central

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

    2016-01-01

    Heterosis has been widely used in agriculture, but the underlying molecular principles are still largely unknown. During seed germination, we observed that maize (Zea mays) hybrid B73/Mo17 was less sensitive than its parental inbred lines to exogenous abscisic acid (ABA), and endogenous ABA content in hybrid embryos decreased more rapidly than in the parental inbred lines. ZmABA8ox1b, an ABA inactivation gene, was consistently more highly up-regulated in hybrid B73/Mo17 than in its parental inbred lines at early stages of seed germination. Moreover, ectopic expression of ZmABA8ox1b obviously promoted seed germination in Arabidopsis. Remarkably, microscopic observation revealed that cell expansion played a major role in the ABA-mediated maize seed germination heterosis, which could be attributed to the altered expression of cell wall-related genes. PMID:27034328

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

    PubMed

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

    2016-04-01

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

  13. A mechanism of growth inhibition by abscisic acid in germinating seeds of Arabidopsis thaliana based on inhibition of plasma membrane H+-ATPase and decreased cytosolic pH, K+, and anions

    PubMed Central

    Planes, María D.; Niñoles, Regina; Rubio, Lourdes; Bissoli, Gaetano; Bueso, Eduardo; García-Sánchez, María J.; Alejandro, Santiago; Gonzalez-Guzmán, Miguel; Hedrich, Rainer; Rodriguez, Pedro L.; Fernández, José A.; Serrano, Ramón

    2015-01-01

    The stress hormone abscisic acid (ABA) induces expression of defence genes in many organs, modulates ion homeostasis and metabolism in guard cells, and inhibits germination and seedling growth. Concerning the latter effect, several mutants of Arabidopsis thaliana with improved capability for H+ efflux (wat1-1D, overexpression of AKT1 and ost2-1D) are less sensitive to inhibition by ABA than the wild type. This suggested that ABA could inhibit H+ efflux (H+-ATPase) and induce cytosolic acidification as a mechanism of growth inhibition. Measurements to test this hypothesis could not be done in germinating seeds and we used roots as the most convenient system. ABA inhibited the root plasma-membrane H+-ATPase measured in vitro (ATP hydrolysis by isolated vesicles) and in vivo (H+ efflux from seedling roots). This inhibition involved the core ABA signalling elements: PYR/PYL/RCAR ABA receptors, ABA-inhibited protein phosphatases (HAB1), and ABA-activated protein kinases (SnRK2.2 and SnRK2.3). Electrophysiological measurements in root epidermal cells indicated that ABA, acting through the PYR/PYL/RCAR receptors, induced membrane hyperpolarization (due to K+ efflux through the GORK channel) and cytosolic acidification. This acidification was not observed in the wat1-1D mutant. The mechanism of inhibition of the H+-ATPase by ABA and its effects on cytosolic pH and membrane potential in roots were different from those in guard cells. ABA did not affect the in vivo phosphorylation level of the known activating site (penultimate threonine) of H+-ATPase in roots, and SnRK2.2 phosphorylated in vitro the C-terminal regulatory domain of H+-ATPase while the guard-cell kinase SnRK2.6/OST1 did not. PMID:25371509

  14. Light Inhibition of Shoot Regeneration Is Regulated by Endogenous Abscisic Acid Level in Calli Derived from Immature Barley Embryos

    PubMed Central

    Rikiishi, Kazuhide; Matsuura, Takakazu; Ikeda, Yoko; Maekawa, Masahiko

    2015-01-01

    Shoot regeneration in calli derived from immature barley embryos is regulated by light conditions during the callus-induction period. Barley cultivars Kanto Nijo-5 (KN5) and K-3 (K3) showed lower efficiency of shoot regeneration in a 16-h photoperiod during callus-induction than those in continuous darkness, whereas shoot regeneration was enhanced in cultures under a 16-h photoperiod in Golden Promise (GP) and Lenins (LN). These cultivars were classified as photo-inhibition type (KN5 and K3) or photo-induction type (GP and LN) according to their response to light. Contents of endogenous plant hormones were determined in calli cultured under a 16-h photoperiod and continuous darkness. In photo-inhibition type, higher accumulation of abscisic acid (ABA) was detected in calli cultured under a 16-h photoperiod, whereas calli showed lower levels of endogenous ABA in continuous darkness. However, cultivars of photo-induction type showed lower levels of ABA in calli cultured under both light conditions, similarly to photo-inhibition type in continuous darkness. Exogenous ABA inhibited the callus growth and shoot regeneration independent of light conditions in all cultivars. In photo-inhibition type, lower levels of endogenous ABA induced by ABA biosynthesis inhibitor, fluridone, reduced the photo-inhibition of shoot regeneration. Expression of ABA biosynthesis gene, HvNCED1, in calli was regulated by the light conditions. Higher expression was observed in calli cultured under a 16-h photoperiod. These results indicate that ABA biosynthesis could be activated through the higher expression of HvNCED1 in a 16-h photoperiod and that the higher accumulations of ABA inhibit shoot regeneration in the photo-inhibition type cultivars. PMID:26670930

  15. Light Inhibition of Shoot Regeneration Is Regulated by Endogenous Abscisic Acid Level in Calli Derived from Immature Barley Embryos.

    PubMed

    Rikiishi, Kazuhide; Matsuura, Takakazu; Ikeda, Yoko; Maekawa, Masahiko

    2015-01-01

    Shoot regeneration in calli derived from immature barley embryos is regulated by light conditions during the callus-induction period. Barley cultivars Kanto Nijo-5 (KN5) and K-3 (K3) showed lower efficiency of shoot regeneration in a 16-h photoperiod during callus-induction than those in continuous darkness, whereas shoot regeneration was enhanced in cultures under a 16-h photoperiod in Golden Promise (GP) and Lenins (LN). These cultivars were classified as photo-inhibition type (KN5 and K3) or photo-induction type (GP and LN) according to their response to light. Contents of endogenous plant hormones were determined in calli cultured under a 16-h photoperiod and continuous darkness. In photo-inhibition type, higher accumulation of abscisic acid (ABA) was detected in calli cultured under a 16-h photoperiod, whereas calli showed lower levels of endogenous ABA in continuous darkness. However, cultivars of photo-induction type showed lower levels of ABA in calli cultured under both light conditions, similarly to photo-inhibition type in continuous darkness. Exogenous ABA inhibited the callus growth and shoot regeneration independent of light conditions in all cultivars. In photo-inhibition type, lower levels of endogenous ABA induced by ABA biosynthesis inhibitor, fluridone, reduced the photo-inhibition of shoot regeneration. Expression of ABA biosynthesis gene, HvNCED1, in calli was regulated by the light conditions. Higher expression was observed in calli cultured under a 16-h photoperiod. These results indicate that ABA biosynthesis could be activated through the higher expression of HvNCED1 in a 16-h photoperiod and that the higher accumulations of ABA inhibit shoot regeneration in the photo-inhibition type cultivars. PMID:26670930

  16. Increased ABA sensitivity results in higher seed dormancy in soft white spring wheat cultivar 'Zak'.

    PubMed

    Schramm, Elizabeth C; Nelson, Sven K; Kidwell, Kimberlee K; Steber, Camille M

    2013-03-01

    As a strategy to increase the seed dormancy of soft white wheat, mutants with increased sensitivity to the plant hormone abscisic acid (ABA) were identified in mutagenized grain of soft white spring wheat "Zak". Lack of seed dormancy is correlated with increased susceptibility to preharvest sprouting in wheat, especially those cultivars with white kernels. ABA induces seed dormancy during embryo maturation and inhibits the germination of mature grain. Three mutant lines called Zak ERA8, Zak ERA19A, and Zak ERA19B (Zak ENHANCED RESPONSE to ABA) were recovered based on failure to germinate on 5 μM ABA. All three mutants resulted in increased ABA sensitivity over a wide range of concentrations such that a phenotype can be detected at very low ABA concentrations. Wheat loses sensitivity to ABA inhibition of germination with extended periods of dry after-ripening. All three mutants recovered required more time to after-ripen sufficiently to germinate in the absence of ABA and to lose sensitivity to 5 μM ABA. However, an increase in ABA sensitivity could be detected after as long as 3 years of after-ripening using high ABA concentrations. The Zak ERA8 line showed the strongest phenotype and segregated as a single semi-dominant mutation. This mutation resulted in no obvious decrease in yield and is a good candidate gene for breeding preharvest sprouting tolerance. PMID:23212773

  17. Genetic analysis of Physcomitrella patens identifies ABSCISIC ACID NON-RESPONSIVE, a regulator of ABA responses unique to basal land plants and required for desiccation tolerance

    DOE PAGES

    Stevenson, Sean Ross; Kamisugi, Yasuko; Trinh, Chi H.; Schmutz, Jeremy; Jenkins, Jerry W.; Grimwood, Jane; Muchero, Wellington; Tuskan, Gerald A.; Rensing, Stefan A.; Lang, Daniel; et al

    2016-05-18

    The anatomically simple plants that first colonized land must have acquired molecular and biochemical adaptations to drought stress. Abscisic acid (ABA) coordinates responses leading to desiccation tolerance in all land plants. We identified ABA nonresponsive mutants in the model bryophyte Physcomitrella patens and genotyped a segregating population to map and identify the ABA NON-RESPONSIVE (ANR) gene encoding a modular protein kinase comprising an N-terminal PAS domain, a central EDR domain, and a C-terminal MAPKKK-like domain. anr mutants fail to accumulate dehydration tolerance-associated gene products in response to drought, ABA, or osmotic stress and do not acquire ABA-dependent desiccation tolerance. Themore » crystal structure of the PAS domain, determined to 1.7-Å resolution, shows a conserved PAS-fold that dimerizes through a weak dimerization interface. Targeted mutagenesis of a conserved tryptophan residue within the PAS domain generates plants with ABA nonresponsive growth and strongly attenuated ABA-responsive gene expression, whereas deleting this domain retains a fully ABA-responsive phenotype. ANR orthologs are found in early-diverging land plant lineages and aquatic algae but are absent from more recently diverged vascular plants. Lastly, we propose that ANR genes represent an ancestral adaptation that enabled drought stress survival of the first terrestrial colonizers but were lost during land plant evolution.« less

  18. Genetic Analysis of Physcomitrella patens Identifies ABSCISIC ACID NON-RESPONSIVE, a Regulator of ABA Responses Unique to Basal Land Plants and Required for Desiccation Tolerance.

    PubMed

    Stevenson, Sean R; Kamisugi, Yasuko; Trinh, Chi H; Schmutz, Jeremy; Jenkins, Jerry W; Grimwood, Jane; Muchero, Wellington; Tuskan, Gerald A; Rensing, Stefan A; Lang, Daniel; Reski, Ralf; Melkonian, Michael; Rothfels, Carl J; Li, Fay-Wei; Larsson, Anders; Wong, Gane K-S; Edwards, Thomas A; Cuming, Andrew C

    2016-06-01

    The anatomically simple plants that first colonized land must have acquired molecular and biochemical adaptations to drought stress. Abscisic acid (ABA) coordinates responses leading to desiccation tolerance in all land plants. We identified ABA nonresponsive mutants in the model bryophyte Physcomitrella patens and genotyped a segregating population to map and identify the ABA NON-RESPONSIVE (ANR) gene encoding a modular protein kinase comprising an N-terminal PAS domain, a central EDR domain, and a C-terminal MAPKKK-like domain. anr mutants fail to accumulate dehydration tolerance-associated gene products in response to drought, ABA, or osmotic stress and do not acquire ABA-dependent desiccation tolerance. The crystal structure of the PAS domain, determined to 1.7-Å resolution, shows a conserved PAS-fold that dimerizes through a weak dimerization interface. Targeted mutagenesis of a conserved tryptophan residue within the PAS domain generates plants with ABA nonresponsive growth and strongly attenuated ABA-responsive gene expression, whereas deleting this domain retains a fully ABA-responsive phenotype. ANR orthologs are found in early-diverging land plant lineages and aquatic algae but are absent from more recently diverged vascular plants. We propose that ANR genes represent an ancestral adaptation that enabled drought stress survival of the first terrestrial colonizers but were lost during land plant evolution. PMID:27194706

  19. Genetic Analysis of Physcomitrella patens Identifies ABSCISIC ACID NON-RESPONSIVE, a Regulator of ABA Responses Unique to Basal Land Plants and Required for Desiccation Tolerance[OPEN

    PubMed Central

    Kamisugi, Yasuko; Trinh, Chi H.; Schmutz, Jeremy; Muchero, Wellington; Melkonian, Michael; Rothfels, Carl J.; Li, Fay-Wei; Larsson, Anders; Edwards, Thomas A.

    2016-01-01

    The anatomically simple plants that first colonized land must have acquired molecular and biochemical adaptations to drought stress. Abscisic acid (ABA) coordinates responses leading to desiccation tolerance in all land plants. We identified ABA nonresponsive mutants in the model bryophyte Physcomitrella patens and genotyped a segregating population to map and identify the ABA NON-RESPONSIVE (ANR) gene encoding a modular protein kinase comprising an N-terminal PAS domain, a central EDR domain, and a C-terminal MAPKKK-like domain. anr mutants fail to accumulate dehydration tolerance-associated gene products in response to drought, ABA, or osmotic stress and do not acquire ABA-dependent desiccation tolerance. The crystal structure of the PAS domain, determined to 1.7-Å resolution, shows a conserved PAS-fold that dimerizes through a weak dimerization interface. Targeted mutagenesis of a conserved tryptophan residue within the PAS domain generates plants with ABA nonresponsive growth and strongly attenuated ABA-responsive gene expression, whereas deleting this domain retains a fully ABA-responsive phenotype. ANR orthologs are found in early-diverging land plant lineages and aquatic algae but are absent from more recently diverged vascular plants. We propose that ANR genes represent an ancestral adaptation that enabled drought stress survival of the first terrestrial colonizers but were lost during land plant evolution. PMID:27194706

  20. Genetic Analysis of Physcomitrella patens Identifies ABSCISIC ACID NON-RESPONSIVE, a Regulator of ABA Responses Unique to Basal Land Plants and Required for Desiccation Tolerance.

    PubMed

    Stevenson, Sean R; Kamisugi, Yasuko; Trinh, Chi H; Schmutz, Jeremy; Jenkins, Jerry W; Grimwood, Jane; Muchero, Wellington; Tuskan, Gerald A; Rensing, Stefan A; Lang, Daniel; Reski, Ralf; Melkonian, Michael; Rothfels, Carl J; Li, Fay-Wei; Larsson, Anders; Wong, Gane K-S; Edwards, Thomas A; Cuming, Andrew C

    2016-06-01

    The anatomically simple plants that first colonized land must have acquired molecular and biochemical adaptations to drought stress. Abscisic acid (ABA) coordinates responses leading to desiccation tolerance in all land plants. We identified ABA nonresponsive mutants in the model bryophyte Physcomitrella patens and genotyped a segregating population to map and identify the ABA NON-RESPONSIVE (ANR) gene encoding a modular protein kinase comprising an N-terminal PAS domain, a central EDR domain, and a C-terminal MAPKKK-like domain. anr mutants fail to accumulate dehydration tolerance-associated gene products in response to drought, ABA, or osmotic stress and do not acquire ABA-dependent desiccation tolerance. The crystal structure of the PAS domain, determined to 1.7-Å resolution, shows a conserved PAS-fold that dimerizes through a weak dimerization interface. Targeted mutagenesis of a conserved tryptophan residue within the PAS domain generates plants with ABA nonresponsive growth and strongly attenuated ABA-responsive gene expression, whereas deleting this domain retains a fully ABA-responsive phenotype. ANR orthologs are found in early-diverging land plant lineages and aquatic algae but are absent from more recently diverged vascular plants. We propose that ANR genes represent an ancestral adaptation that enabled drought stress survival of the first terrestrial colonizers but were lost during land plant evolution.

  1. Type One Protein Phosphatase 1 and Its Regulatory Protein Inhibitor 2 Negatively Regulate ABA Signaling

    PubMed Central

    Zhao, Yang; Xie, Shaojun; Batelli, Giorgia; Wang, Bangshing; Duan, Cheng-Guo; Wang, Xingang; Xing, Lu; Lei, Mingguang; Yan, Jun; Zhu, Xiaohong; Zhu, Jian-Kang

    2016-01-01

    The phytohormone abscisic acid (ABA) regulates plant growth, development and responses to biotic and abiotic stresses. The core ABA signaling pathway consists of three major components: ABA receptor (PYR1/PYLs), type 2C Protein Phosphatase (PP2C) and SNF1-related protein kinase 2 (SnRK2). Nevertheless, the complexity of ABA signaling remains to be explored. To uncover new components of ABA signal transduction pathways, we performed a yeast two-hybrid screen for SnRK2-interacting proteins. We found that Type One Protein Phosphatase 1 (TOPP1) and its regulatory protein, At Inhibitor-2 (AtI-2), physically interact with SnRK2s and also with PYLs. TOPP1 inhibited the kinase activity of SnRK2.6, and this inhibition could be enhanced by AtI-2. Transactivation assays showed that TOPP1 and AtI-2 negatively regulated the SnRK2.2/3/6-mediated activation of the ABA responsive reporter gene RD29B, supporting a negative role of TOPP1 and AtI-2 in ABA signaling. Consistent with these findings, topp1 and ati-2 mutant plants displayed hypersensitivities to ABA and salt treatments, and transcriptome analysis of TOPP1 and AtI-2 knockout plants revealed an increased expression of multiple ABA-responsive genes in the mutants. Taken together, our results uncover TOPP1 and AtI-2 as negative regulators of ABA signaling. PMID:26943172

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

    PubMed

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

    2016-09-01

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

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

    PubMed Central

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

    2015-01-01

    The phytohormone abscisic acid (ABA) regulates plant development and is crucial for abiotic stress response. In this study, cold storage contributes to reducing endogenous ABA content, resulting in dormancy breaking of Gladiolus. The ABA inhibitor fluridone also promotes germination, suggesting that ABA is an important hormone that regulates corm dormancy. Here, we report the identification and functional characterization of the Gladiolus ABI5 homolog (GhABI5), which is a basic leucine zipper motif transcriptional factor (TF). GhABI5 is expressed in dormant vegetative organs (corm, cormel, and stolon) as well as in reproductive organs (stamen), and it is up-regulated by ABA or drought. Complementation analysis reveals that GhABI5 rescues the ABA insensitivity of abi5-3 during seed germination and induces the expression of downstream ABA response genes in Arabidopsis thaliana (EM1, EM6, and RD29B). Down-regulation of GhABI5 in dormant cormels via virus induced gene silence promotes sprouting and reduces the expression of downstream genes (GhLEA and GhRD29B). The results of this study reveal that GhABI5 regulates bud dormancy (vegetative organ) in Gladiolus in addition to its well-studied function in Arabidopsis seeds (reproductive organ). PMID:26579187

  4. Mechanisms independent of abscisic acid (ABA) or proline feedback have a predominant role in transcriptional regulation of proline metabolism during low water potential and stress recovery.

    PubMed

    Sharma, Sandeep; Verslues, Paul E

    2010-11-01

    Proline accumulation in response to abiotic stress is controlled partially by transcriptional regulation of key enzymes including Δ¹-pyrroline-carboxylate synthetase1 (P5CS1), proline dehydrogenase (ProDH), ornithine amino transferase (OAT) and Δ¹-pyrroline-carboxylate dehydrogenase (P5CDH). For these genes, the role of abscisic acid (ABA), role of feedback regulation by high proline and the mechanisms of gene regulation upon stress release remain unclear. An ABA-deficient (aba2-1) mutant, mutants deficient in proline accumulation (p5cs1), as well as double mutants deficient in both, were used to determine the importance of these factors in transcriptional regulation of proline metabolism. Upregulation of P5CS1 by low water potential was less dependent on ABA than that of stress-marker genes used for comparison. ProDH downregulation by low water potential and upregulation by stress release was not impaired in aba2-1, p5cs1 or p5cs1/aba2-1 compared with wild type despite differing ABA and proline levels in these mutants. Thus, ProDH is a model for characterization of novel regulatory mechanisms associated with low water potential and stress recovery. Both OAT and P5CDH were upregulated during low water potential. This contrasts with previous salt stress experiments and raises questions about the flux of metabolites through proline metabolism under low water potential when high levels of proline accumulate.

  5. NADPH oxidase AtrbohD and AtrbohF genes function in ROS-dependent ABA signaling in Arabidopsis.

    PubMed

    Kwak, June M; Mori, Izumi C; Pei, Zhen-Ming; Leonhardt, Nathalie; Torres, Miguel Angel; Dangl, Jeffery L; Bloom, Rachel E; Bodde, Sara; Jones, Jonathan D G; Schroeder, Julian I

    2003-06-01

    Reactive oxygen species (ROS) have been proposed to function as second messengers in abscisic acid (ABA) signaling in guard cells. However, the question whether ROS production is indeed required for ABA signal transduction in vivo has not yet been addressed, and the molecular mechanisms mediating ROS production during ABA signaling remain unknown. Here, we report identification of two partially redundant Arabidopsis guard cell-expressed NADPH oxidase catalytic subunit genes, AtrbohD and AtrbohF, in which gene disruption impairs ABA signaling. atrbohD/F double mutations impair ABA-induced stomatal closing, ABA promotion of ROS production, ABA-induced cytosolic Ca(2+) increases and ABA- activation of plasma membrane Ca(2+)-permeable channels in guard cells. Exogenous H(2)O(2) rescues both Ca(2+) channel activation and stomatal closing in atrbohD/F. ABA inhibition of seed germination and root elongation are impaired in atrbohD/F, suggesting more general roles for ROS and NADPH oxidases in ABA signaling. These data provide direct molecular genetic and cell biological evidence that ROS are rate-limiting second messengers in ABA signaling, and that the AtrbohD and AtrbohF NADPH oxidases function in guard cell ABA signal transduction.

  6. Increased ABA sensitivity results in higher seed dormancy in soft white spring wheat cultivar ‘Zak’

    PubMed Central

    Schramm, Elizabeth C.; Nelson, Sven K.; Kidwell, Kimberlee K.

    2014-01-01

    As a strategy to increase the seed dormancy of soft white wheat, mutants with increased sensitivity to the plant hormone abscisic acid (ABA) were identified in mutagenized grain of soft white spring wheat “Zak”. Lack of seed dormancy is correlated with increased susceptibility to preharvest sprouting in wheat, especially those cultivars with white kernels. ABA induces seed dormancy during embryo maturation and inhibits the germination of mature grain. Three mutant lines called Zak ERA8, Zak ERA19A, and Zak ERA19B (Zak ENHANCED RESPONSE to ABA) were recovered based on failure to germinate on 5 µM ABA. All three mutants resulted in increased ABA sensitivity over a wide range of concentrations such that a phenotype can be detected at very low ABA concentrations. Wheat loses sensitivity to ABA inhibition of germination with extended periods of dry after-ripening. All three mutants recovered required more time to after-ripen sufficiently to germinate in the absence of ABA and to lose sensitivity to 5 µM ABA. However, an increase in ABA sensitivity could be detected after as long as 3 years of after-ripening using high ABA concentrations. The Zak ERA8 line showed the strongest phenotype and segregated as a single semi-dominant mutation. This mutation resulted in no obvious decrease in yield and is a good candidate gene for breeding preharvest sprouting tolerance. PMID:23212773

  7. Arabidopsis DREB2C modulates ABA biosynthesis during germination.

    PubMed

    Je, Jihyun; Chen, Huan; Song, Chieun; Lim, Chae Oh

    2014-09-12

    Plant dehydration-responsive element binding factors (DREBs) are transcriptional regulators of the APETELA2/Ethylene Responsive element-binding Factor (AP2/ERF) family that control expression of abiotic stress-related genes. We show here that under conditions of mild heat stress, constitutive overexpression seeds of transgenic DREB2C overexpression Arabidopsis exhibit delayed germination and increased abscisic acid (ABA) content compared to untransformed wild-type (WT). Treatment with fluridone, an inhibitor of the ABA biosynthesis abrogated these effects. Expression of an ABA biosynthesis-related gene, 9-cis-epoxycarotenoid dioxygenase 9 (NCED9) was up-regulated in the DREB2C overexpression lines compared to WT. DREB2C was able to trans-activate expression of NCED9 in Arabidopsis leaf protoplasts in vitro. Direct and specific binding of DREB2C to a complete DRE on the NCED9 promoter was observed in electrophoretic mobility shift assays. Exogenous ABA treatment induced DREB2C expression in germinating seeds of WT. Vegetative growth of transgenic DREB2C overexpression lines was more strongly inhibited by exogenous ABA compared to WT. These results suggest that DREB2C is a stress- and ABA-inducible gene that acts as a positive regulator of ABA biosynthesis in germinating seeds through activating NCED9 expression.

  8. Salicylic acid mediates antioxidant defense system and ABA pathway related gene expression in Oryza sativa against quinclorac toxicity.

    PubMed

    Wang, Jian; Lv, Mengting; Islam, Faisal; Gill, Rafaqat A; Yang, Chong; Ali, Basharat; Yan, Guijun; Zhou, Weijun

    2016-11-01

    The auxin herbicide quinclorac is widely used for controlling weeds in transplanted and direct-seeded rice fields. However, its phytotoxic responses on rice are still unknown. Therefore, in the present investigation we studied the effects of different concentrations (0, 0.1 and 0.5g/L) of quinclorac herbicide on the physiological and biochemical changes of two rice cultivars (XS 134 and ZJ 88) and further analyzed the ameliorating role of salicylic acid (SA) on quinclorac toxicity in rice plants. The results revealed that exogenous application of SA significantly increased plant biomass and total chlorophyll contents in herbicide stressed plants. The lipid peroxidation and ROS (H2O2, O2(-.), (-)OH) production were significantly increased in roots and leaves of both rice cultivars under quinclorac stress, demonstrating an oxidative burst in rice plants. Whereas, application of SA significantly lowered ROS contents under quinclorac stress. Further, exogenous SA treatment significantly modulated antioxidant enzymes and enhanced GSH concentration in stress plants. Anatomical observations of leaf and root revealed that herbicide affected internal structures, while SA played a vital role in protection from toxic effects. Expression analysis of stress hormone ABA genes (OsABA8oxs, OsNCEDs) revealed that quinclorac application enhanced stress condition in cultivar ZJ 88, while SA treatment downregulated ABA genes more in cultivar XS 134, which correlated with the enhanced tolerance to quinclorac induced oxidative stress in this cultivar. The present study delineated that SA played a critical role under quinclorac stress in both rice cultivars by regulating antioxidant defense system, reducing ROS formation and preventing the degradation of internal cell organelles.

  9. Salicylic acid mediates antioxidant defense system and ABA pathway related gene expression in Oryza sativa against quinclorac toxicity.

    PubMed

    Wang, Jian; Lv, Mengting; Islam, Faisal; Gill, Rafaqat A; Yang, Chong; Ali, Basharat; Yan, Guijun; Zhou, Weijun

    2016-11-01

    The auxin herbicide quinclorac is widely used for controlling weeds in transplanted and direct-seeded rice fields. However, its phytotoxic responses on rice are still unknown. Therefore, in the present investigation we studied the effects of different concentrations (0, 0.1 and 0.5g/L) of quinclorac herbicide on the physiological and biochemical changes of two rice cultivars (XS 134 and ZJ 88) and further analyzed the ameliorating role of salicylic acid (SA) on quinclorac toxicity in rice plants. The results revealed that exogenous application of SA significantly increased plant biomass and total chlorophyll contents in herbicide stressed plants. The lipid peroxidation and ROS (H2O2, O2(-.), (-)OH) production were significantly increased in roots and leaves of both rice cultivars under quinclorac stress, demonstrating an oxidative burst in rice plants. Whereas, application of SA significantly lowered ROS contents under quinclorac stress. Further, exogenous SA treatment significantly modulated antioxidant enzymes and enhanced GSH concentration in stress plants. Anatomical observations of leaf and root revealed that herbicide affected internal structures, while SA played a vital role in protection from toxic effects. Expression analysis of stress hormone ABA genes (OsABA8oxs, OsNCEDs) revealed that quinclorac application enhanced stress condition in cultivar ZJ 88, while SA treatment downregulated ABA genes more in cultivar XS 134, which correlated with the enhanced tolerance to quinclorac induced oxidative stress in this cultivar. The present study delineated that SA played a critical role under quinclorac stress in both rice cultivars by regulating antioxidant defense system, reducing ROS formation and preventing the degradation of internal cell organelles. PMID:27448955

  10. Biochemical characterization of the aba2 and aba3 mutants in Arabidopsis thaliana.

    PubMed

    Schwartz, S H; Léon-Kloosterziel, K M; Koornneef, M; Zeevaart, J A

    1997-05-01

    Abscisic acid (ABA)-deficient mutants in a variety of species have been identified by screening for precocious germination and a wilty phenotype. Mutants at two new loci, aba2 and aba3, have recently been isolated in Arabidopsis thaliana (L.) Hynh. (K.M. Léon-Kloosterziel, M. Alvarez-Gil, G.J. Ruijs, S.E. Jacobsen, N.E. Olszewski, S.H. Schwartz, J.A.D. Zeevaart, M. Koornneef [1996] Plant J 10: 655-661), and the biochemical characterization of these mutants is presented here. Protein extracts from aba2 and aba3 plants displayed a greatly reduced ability to convert xanthoxin to ABA relative to the wild type. The next putative intermediate in ABA synthesis, ABA-aldehyde, was efficiently converted to ABA by extracts from aba2 but not by extracts from aba3 plants. This indicates that the aba2 mutant is blocked in the conversion of xanthoxin to ABA-aldehyde and that aba3 is impaired in the conversion of ABA-aldehyde to ABA. Extracts from the aba3 mutant also lacked additional activities that require a molybdenum cofactor (Moco). Nitrate reductase utilizes a Moco but its activity was unaffected in extracts from aba3 plants. Moco hydroxylases in animals require a desulfo moiety of the cofactor. A sulfido ligand can be added to the Moco by treatment with Na2S and dithionite. Treatment of aba3 extracts with Na2S restored ABA-aldehyde oxidase activity. Therefore, the genetic lesion in aba3 appears to be in the introduction of S into the Moco. PMID:9159947

  11. AtrbohD and AtrbohF positively regulate abscisic acid-inhibited primary root growth by affecting Ca2+ signalling and auxin response of roots in Arabidopsis.

    PubMed

    Jiao, Yiheng; Sun, Lirong; Song, Yalin; Wang, Limin; Liu, Liping; Zhang, Liyue; Liu, Bo; Li, Ning; Miao, Chen; Hao, Fushun

    2013-11-01

    Reactive oxygen species (ROS) originating from the NADPH oxidases AtrbohD and AtrbohF play an important role in abscisic acid (ABA)-inhibited primary root growth in Arabidopsis. However, the mechanisms underlying this process remain elusive. In this study, the double mutant atrbohD1/F1 and atrbohD2/F2, in which both AtrbohD and AtrbohF were disrupted, were less sensitive to ABA suppression of root cell elongation than wild-type (WT) plants. Furthermore, the double mutants showed impaired ABA responses in roots, including ROS generation, cytosolic Ca(2+) increases, and activation of plasma membrane Ca(2+)-permeable channels compared with WT. Exogenous H2O2 can activate the Ca(2+) currents in roots of atrbohD1/F1. In addition, exogenous application of the auxin transport inhibitor naphthylphthalamic acid effectively promoted ABA inhibition of root growth of the mutants relative to that of WT. The ABA-induced decreases in auxin sensitivity of the root tips were more pronounced in WT than in atrbohD1/F1. These findings suggest that both AtrbohD and AtrbohF are essential for ABA-promoted ROS production in roots. ROS activate Ca(2+) signalling and reduce auxin sensitivity of roots, thus positively regulating ABA-inhibited primary root growth in Arabidopsis.

  12. The pathway of biosynthesis of abscisic acid in vascular plants: a review of the present state of knowledge of ABA biosynthesis.

    PubMed

    Milborrow, B V

    2001-06-01

    The pathway of biosynthesis of abscisic acid (ABA) can be considered to comprise three stages: (i) early reactions in which small phosphorylated intermediates are assembled as precursors of (ii) intermediate reactions which begin with the formation of the uncyclized C40 carotenoid phytoene and end with the cleavage of 9'-cis-neoxanthin (iii) to form xanthoxal, the C15 skeleton of ABA. The final phase comprising C15 intermediates is not yet completely defined, but the evidence suggests that xanthoxal is first oxidized to xanthoxic acid by a molybdenum-containing aldehyde oxidase and this is defective in the aba3 mutant of Arabidopsis and present in a 1-fold acetone precipitate of bean leaf proteins. This oxidation precludes the involvement of AB-aldehyde as an intermediate. The oxidation of the 4'-hydroxyl group to the ketone and the isomerization of the 1',2'-epoxy group to the 1'-hydroxy-2'-ene may be brought about by one enzyme which is defective in the aba2 mutant and is present in the 3-fold acetone fraction of bean leaves. Isopentenyl diphosphate (IPP) is now known to be derived by the pyruvate-triose (Methyl Erythritol Phosphate, MEP) pathway in chloroplasts. (14C)IPP is incorporated into ABA by washed, intact chloroplasts of spinach leaves, but (14C)mevalonate is not, consequently, all three phases of biosynthesis of ABA occur within chloroplasts. The incorporation of labelled mevalonate into ABA by avocado fruit and orange peel is interpreted as uptake of IPP made in the cytoplasm, where it is the normal precursor of sterols, and incorporated into carotenoids after uptake by a carrier in the chloroplast envelope. An alternative bypass pathway becomes more important in aldehyde oxidase mutants, which may explain why so many wilty mutants have been found with this defect. The C-1 alcohol group is oxidized, possibly by a mono-oxygenase, to give the C-1 carboxyl of ABA. The 2-cis double bond of ABA is essential for its biological activity but it is not known

  13. Degradation of the ABA co-receptor ABI1 by PUB12/13 U-box E3 ligases

    PubMed Central

    Kong, Lingyao; Cheng, Jinkui; Zhu, Yujuan; Ding, Yanglin; Meng, Jingjing; Chen, Zhizhong; Xie, Qi; Guo, Yan; Li, Jigang; Yang, Shuhua; Gong, Zhizhong

    2015-01-01

    Clade A protein phosphatase 2Cs (PP2Cs) are abscisic acid (ABA) co-receptors that block ABA signalling by inhibiting the downstream protein kinases. ABA signalling is activated after PP2Cs are inhibited by ABA-bound PYR/PYL/RCAR ABA receptors (PYLs) in Arabidopsis. However, whether these PP2Cs are regulated by other factors remains unknown. Here, we report that ABI1 (ABA-INSENSITIVE 1) can interact with the U-box E3 ligases PUB12 and PUB13, but is ubiquitinated only when it interacts with ABA receptors in an in vitro assay. A mutant form of ABI1-1 that is unable to interact with PYLs is more stable than the wild-type protein. Both ABI1 degradation and all tested ABA responses are reduced in pub12 pub13 mutants compared with the wild type. Introducing the abi1-3 loss-of-function mutation into pub12 pub13 mutant recovers the ABA-insensitive phenotypes of the pub12 pub13 mutant. We thus uncover an important regulatory mechanism for regulating ABI1 levels by PUB12 and PUB13. PMID:26482222

  14. The role of ABA in triggering ethylene biosynthesis and ripening of tomato fruit

    PubMed Central

    Zhang, Mei; Yuan, Bing; Leng, Ping

    2009-01-01

    In order to understand more details about the role of abscisic acid (ABA) in fruit ripening and senescence of tomato, two cDNAs (LeNCED1 and LeNCED2) which encode 9-cis-epoxycarotenoid dioxygenase (NCED) as a key enzyme in ABA biosynthesis, two cDNAs (LeACS2 and LeACS4) which encode 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, and one cDNA (LeACO1) which encodes ACC oxidase involved in ethylene biosynthesis were cloned from tomato fruit using a reverse transcription-PCR (RT-PCR) approach. The relationship between ABA and ethylene during ripening was also investigated. Among six sampling times in tomato fruits, the LeNCED1 gene was highly expressed only at the breaker stage when the ABA content becomes high. After this, the LeACS2, LeACS4, and LeACO1 genes were expressed with some delay. The change in pattern of ACO activity was in accordance with ethylene production reaching its peak at the pink stage. The maximum ABA content preceded ethylene production in both the seeds and the flesh. The peak value of ABA, ACC, and ACC oxidase activity, and ethylene production all started to increase earlier in seeds than in flesh tissues, although they occurred at different ripening stages. Exogenous ABA treatment increased the ABA content in both flesh and seed, inducing the expression of both ACS and ACO genes, and promoting ethylene synthesis and fruit ripening, while treatment with fluridone or nordihydroguaiaretic acid (NDGA) inhibited them, delaying fruit ripening and softening. Based on the results obtained in this study, it was concluded that LeNCED1 initiates ABA biosynthesis at the onset of fruit ripening, and might act as an original inducer, and ABA accumulation might play a key role in the regulation of ripeness and senescence of tomato fruit. PMID:19246595

  15. Apoptosis in barley aleurone during germination and its inhibition by abscisic acid.

    PubMed

    Wang, M; Oppedijk, B J; Lu, X; Van Duijn, B; Schilperoort, R A

    1996-12-01

    During germination of barley grains, DNA fragmentation was observed in the aleurone. The appearance of DNA fragmentation in the aleurone layer, observed by TUNEL staining in aleurone sections, started near the embryo and extended to the aleurone cells far from the embryo in a time dependent manner. The same spatial temporal activities of hydrolytic enzymes such as alpha-amylase were observed in aleurone. DNA fragmentation could also be seen in vitro under osmotic stress, in isolated aleurone. During aleurone protoplast isolation, a very enhanced and strong DNA fragmentation occurred which was not seen in protoplast preparations of tobacco leaves. ABA was found to inhibit DNA fragmentation occurring in barley aleurone under osmotic stress condition and during protoplast isolation, while the plant growth regulator gibberellic acid counteracted the effect of ABA. Addition of auxin or cytokinin had no significant effect on DNA fragmentation in these cells. To study the role of phosphorylation in ABA signal transduction leading to control of DNA fragmentation (apoptosis), the effects of the phosphatase inhibitor okadaic acid and of phenylarisine oxide on apoptosis were studied. We hypothesize that the regulation of DNA fragmentation in aleurone plays a very important role in spatial and temporal control of aleurone activities during germination. The possible signal transduction pathway of ABA leading to the regulation of DNA fragmentation is discussed.

  16. Involvement of plant endogenous ABA in Bacillus megaterium PGPR activity in tomato plants

    PubMed Central

    2014-01-01

    Background Plant growth-promoting rhizobacteria (PGPR) are naturally occurring soil bacteria which benefit plants by improving plant productivity and immunity. The mechanisms involved in these processes include the regulation of plant hormone levels such as ethylene and abscisic acid (ABA). The aim of the present study was to determine whether the activity of Bacillus megaterium PGPR is affected by the endogenous ABA content of the host plant. The ABA-deficient tomato mutants flacca and sitiens and their near-isogenic wild-type parental lines were used. Growth, stomatal conductance, shoot hormone concentration, competition assay for colonization of tomato root tips, and root expression of plant genes expected to be modulated by ABA and PGPR were examined. Results Contrary to the wild-type plants in which PGPR stimulated growth rates, PGPR caused growth inhibition in ABA-deficient mutant plants. PGPR also triggered an over accumulation of ethylene in ABA-deficient plants which correlated with a higher expression of the pathogenesis-related gene Sl-PR1b. Conclusions Positive correlation between over-accumulation of ethylene and a higher expression of Sl-PR1b in ABA-deficient mutant plants could indicate that maintenance of normal plant endogenous ABA content may be essential for the growth promoting action of B. megaterium by keeping low levels of ethylene production. PMID:24460926

  17. Boric acid and boronic acids inhibition of pigeonpea urease.

    PubMed

    Reddy, K Ravi Charan; Kayastha, Arvind M

    2006-08-01

    Urease from the seeds of pigeonpea was competitively inhibited by boric acid, butylboronic acid, phenylboronic acid, and 4-bromophenylboronic acid; 4-bromophenylboronic acid being the strongest inhibitor, followed by boric acid > butylboronic acid > phenylboronic acid, respectively. Urease inhibition by boric acid is maximal at acidic pH (5.0) and minimal at alkaline pH (10.0), i.e., the trigonal planar B(OH)3 form is a more effective inhibitor than the tetrahedral B(OH)4 -anionic form. Similarly, the anionic form of phenylboronic acid was least inhibiting in nature.

  18. ABA Receptors: Past, Present and Future

    SciTech Connect

    Guo, Jianjun; Yang, Xiaohan; Weston, David; Chen, Jay

    2011-01-01

    Abscisic acid (ABA) is the key plant stress hormone. Consistent with the earlier studies in support of the presence of both membrane- and cytoplasm-localized ABA receptors, recent studies have identified multiple ABA receptors located in various subcellular locations. These include a chloroplast envelope-localized receptor (the H subunit of Chloroplast Mg2+-chelatase/ABA Receptor), two plasma membrane-localized receptors (G-protein Coupled Receptor 2 and GPCR-type G proteins), and one cytosol/nucleus-localized Pyrabactin Resistant (PYR)/PYR-Like (PYL)/Regulatory Component of ABA Receptor 1 (RCAR). Although the downstream molecular events for most of the identified ABA receptors are currently unknown, one of them, PYR/PYL/RACR was found to directly bind and regulate the activity of a long-known central regulator of ABA signaling, the A-group protein phosphatase 2C (PP2C). Together with the Sucrose Non-fermentation Kinase Subfamily 2 (SnRK2s) protein kinases, a central signaling complex (ABA-PYR-PP2Cs-SnRK2s) that is responsible for ABA signal perception and transduction is supported by abundant genetic, physiological, biochemical and structural evidence. The identification of multiple ABA receptors has advanced our understanding of ABA signal perception and transduction while adding an extra layer of complexity.

  19. Conformationally restricted 3'-modified ABA analogs for controlling ABA receptors.

    PubMed

    Takeuchi, Jun; Ohnishi, Toshiyuki; Okamoto, Masanori; Todoroki, Yasushi

    2015-04-14

    The physiological functions of abscisic acid (ABA) are regulated by a signal transduction pathway involving cytosolic ABA receptors, which include 14 PYR/PYL/RCAR (PYL) proteins in Arabidopsis. The development of a PYL antagonist could be a valuable tool to improve our understanding of the roles of ABA. We previously developed 3'-hexylsulfanyl-ABA (AS6), whose S-hexyl chain blocks protein phosphatase 2C (PP2C) binding by steric hindrance. This finding not only validated our structure-based approach to the design of a PYL antagonist, but also provided a basis for the development of a more potent or subclass/subtype selective PYL antagonist. In the present study, we synthesized a conformationally restricted analog of AS6, namely propenyl-ABA with an O-butyl chain (PAO4), to improve the affinity for PYL proteins by reducing the entropic penalty for binding to the receptors. In seed germination assays, (+)-PAO4 was a slightly stronger antagonist than AS6 in Arabidopsis and a significantly stronger antagonist in lettuce. Analysis of the thermodynamic parameters associated with the formation of the Arabidopsis PYL-(+)-PAO4 complex revealed that (+)-PAO4 binds more strongly to PYL5 than AS6 owing to an entropic advantage. In PP2C assays, this enhancement effect was observed only for the monomeric PYL subclass containing PYL5, suggesting that (+)-PAO4 is more effective than AS6 in physiological events involving monomeric PYL proteins as ABA receptors. PMID:25758810

  20. Beta-aminobutyric acid priming of plant defense: the role of ABA and other hormones.

    PubMed

    Baccelli, Ivan; Mauch-Mani, Brigitte

    2016-08-01

    Plants are exposed to recurring biotic and abiotic stresses that can, in extreme situations, lead to substantial yield losses. With the changing environment, the stress pressure is likely to increase and sustainable measures to alleviate the effect on our crops are sought. Priming plants for better stress resistance is one of the sustainable possibilities to reach this goal. Here, we report on the effects of beta-aminobutyric acid, a priming agent with an exceptionally wide range of action and describe its way of preparing plants to defend themselves against various attacks, among others through the modulation of their hormonal defense signaling, and highlight the special role of abscisic acid in this process.

  1. Endodermal ABA signaling promotes lateral root quiescence during salt stress in Arabidopsis seedlings.

    PubMed

    Duan, Lina; Dietrich, Daniela; Ng, Chong Han; Chan, Penny Mei Yeen; Bhalerao, Rishikesh; Bennett, Malcolm J; Dinneny, José R

    2013-01-01

    The endodermal tissue layer is found in the roots of vascular plants and functions as a semipermeable barrier, regulating the transport of solutes from the soil into the vascular stream. As a gateway for solutes, the endodermis may also serve as an important site for sensing and responding to useful or toxic substances in the environment. Here, we show that high salinity, an environmental stress widely impacting agricultural land, regulates growth of the seedling root system through a signaling network operating primarily in the endodermis. We report that salt stress induces an extended quiescent phase in postemergence lateral roots (LRs) whereby the rate of growth is suppressed for several days before recovery begins. Quiescence is correlated with sustained abscisic acid (ABA) response in LRs and is dependent upon genes necessary for ABA biosynthesis, signaling, and transcriptional regulation. We use a tissue-specific strategy to identify the key cell layers where ABA signaling acts to regulate growth. In the endodermis, misexpression of the ABA insensitive1-1 mutant protein, which dominantly inhibits ABA signaling, leads to a substantial recovery in LR growth under salt stress conditions. Gibberellic acid signaling, which antagonizes the ABA pathway, also acts primarily in the endodermis, and we define the crosstalk between these two hormones. Our results identify the endodermis as a gateway with an ABA-dependent guard, which prevents root growth into saline environments.

  2. The ABA receptor PYL9 together with PYL8 plays an important role in regulating lateral root growth.

    PubMed

    Xing, Lu; Zhao, Yang; Gao, Jinghui; Xiang, Chengbin; Zhu, Jian-Kang

    2016-01-01

    Abscisic acid is a phytohormone regulating plant growth, development and stress responses. PYR1/PYL/RCAR proteins are ABA receptors that function by inhibiting PP2Cs to activate SnRK2s, resulting in phosphorylation of ABFs and other effectors of ABA response pathways. Exogenous ABA induces growth quiescence of lateral roots, which is prolonged by knockout of the ABA receptor PYL8. Among the 14 members of PYR1/PYL/RCAR protein family, PYL9 is a close relative of PYL8. Here we show that knockout of both PYL9 and PYL8 resulted in a longer ABA-induced quiescence on lateral root growth and a reduced sensitivity to ABA on primary root growth and lateral root formation compared to knockout of PYL8 alone. Induced overexpression of PYL9 promoted the lateral root elongation in the presence of ABA. The prolonged quiescent phase of the pyl8-1pyl9 double mutant was reversed by exogenous IAA. PYL9 may regulate auxin-responsive genes in vivo through direct interaction with MYB77 and MYB44. Thus, PYL9 and PYL8 are both responsible for recovery of lateral root from ABA inhibition via MYB transcription factors. PMID:27256015

  3. The ABA receptor PYL9 together with PYL8 plays an important role in regulating lateral root growth

    PubMed Central

    Xing, Lu; Zhao, Yang; Gao, Jinghui; Xiang, Chengbin; Zhu, Jian-Kang

    2016-01-01

    Abscisic acid is a phytohormone regulating plant growth, development and stress responses. PYR1/PYL/RCAR proteins are ABA receptors that function by inhibiting PP2Cs to activate SnRK2s, resulting in phosphorylation of ABFs and other effectors of ABA response pathways. Exogenous ABA induces growth quiescence of lateral roots, which is prolonged by knockout of the ABA receptor PYL8. Among the 14 members of PYR1/PYL/RCAR protein family, PYL9 is a close relative of PYL8. Here we show that knockout of both PYL9 and PYL8 resulted in a longer ABA-induced quiescence on lateral root growth and a reduced sensitivity to ABA on primary root growth and lateral root formation compared to knockout of PYL8 alone. Induced overexpression of PYL9 promoted the lateral root elongation in the presence of ABA. The prolonged quiescent phase of the pyl8-1pyl9 double mutant was reversed by exogenous IAA. PYL9 may regulate auxin-responsive genes in vivo through direct interaction with MYB77 and MYB44. Thus, PYL9 and PYL8 are both responsible for recovery of lateral root from ABA inhibition via MYB transcription factors. PMID:27256015

  4. Loss of nitrate reductases NIA1 and NIA2 impairs stomatal closure by altering genes of core ABA signaling components in Arabidopsis.

    PubMed

    Zhao, Chenchen; Cai, Shengguan; Wang, Yizhou; Chen, Zhong-Hua

    2016-06-01

    Nitrate reductases NIA1 and NIA2 determine NO production in plants and are critical to abscisic acid (ABA)-induced stomatal closure. However, the role for NIA1 and NIA2 in ABA signaling has not been paid much attention in nitrate reductase loss-of-function mutant nia1nia2. Recently, we have demonstrated that ABA-inhibited K(+)in current and ABA-enhanced slow anion current were absent in nia1nia2. Exogenous NO restored regulation of these channels for stomatal closure in nia1nia2. In this study, we found that mutating NIA1 and NIA2 impaired nearly all the key components of guard cell ABA signaling pathway in Arabidopsis. We also propose a simplified model for ABA signaling in the nia1nia2 mutant.

  5. Loss of nitrate reductases NIA1 and NIA2 impairs stomatal closure by altering genes of core ABA signaling components in Arabidopsis

    PubMed Central

    Zhao, Chenchen; Cai, Shengguan; Wang, Yizhou; Chen, Zhong-Hua

    2016-01-01

    ABSTRACT Nitrate reductases NIA1 and NIA2 determine NO production in plants and are critical to abscisic acid (ABA)-induced stomatal closure. However, the role for NIA1 and NIA2 in ABA signaling has not been paid much attention in nitrate reductase loss-of-function mutant nia1nia2. Recently, we have demonstrated that ABA-inhibited K+in current and ABA-enhanced slow anion current were absent in nia1nia2. Exogenous NO restored regulation of these channels for stomatal closure in nia1nia2. In this study, we found that mutating NIA1 and NIA2 impaired nearly all the key components of guard cell ABA signaling pathway in Arabidopsis. We also propose a simplified model for ABA signaling in the nia1nia2 mutant. PMID:27171851

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2015-01-01

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

  8. Transcriptomic Analysis Reveals Possible Influences of ABA on Secondary Metabolism of Pigments, Flavonoids and Antioxidants in Tomato Fruit during Ripening

    PubMed Central

    Mou, Wangshu; Li, Dongdong; Luo, Zisheng; Mao, Linchun; Ying, Tiejin

    2015-01-01

    Abscisic acid (ABA) has been proven to be involved in the regulation of climacteric fruit ripening, but a comprehensive investigation of its influence on ripening related processes is still lacking. By applying the next generation sequencing technology, we conducted a comparative analysis of the effects of exogenous ABA and NDGA (Nordihydroguaiaretic acid, an inhibitor of ABA biosynthesis) on tomato fruit ripening. The high throughput sequencing results showed that out of the 25728 genes expressed across all three samples, 10388 were identified as significantly differently expressed genes. Exogenous ABA was found to enhance the transcription of genes involved in pigments metabolism, including carotenoids biosynthesis and chlorophyll degradation, whereas NDGA treatment inhibited these processes. The results also revealed the crucial role of ABA in flavonoids synthesis and regulation of antioxidant system. Intriguingly, we also found that an inhibition of endogenous ABA significantly enhanced the transcriptional abundance of genes involved in photosynthesis. Our results highlighted the significance of ABA in regulating tomato ripening, which provided insight into the regulatory mechanism of fruit maturation and senescence process. PMID:26053166

  9. Transcriptomic Analysis Reveals Possible Influences of ABA on Secondary Metabolism of Pigments, Flavonoids and Antioxidants in Tomato Fruit during Ripening.

    PubMed

    Mou, Wangshu; Li, Dongdong; Luo, Zisheng; Mao, Linchun; Ying, Tiejin

    2015-01-01

    Abscisic acid (ABA) has been proven to be involved in the regulation of climacteric fruit ripening, but a comprehensive investigation of its influence on ripening related processes is still lacking. By applying the next generation sequencing technology, we conducted a comparative analysis of the effects of exogenous ABA and NDGA (Nordihydroguaiaretic acid, an inhibitor of ABA biosynthesis) on tomato fruit ripening. The high throughput sequencing results showed that out of the 25728 genes expressed across all three samples, 10388 were identified as significantly differently expressed genes. Exogenous ABA was found to enhance the transcription of genes involved in pigments metabolism, including carotenoids biosynthesis and chlorophyll degradation, whereas NDGA treatment inhibited these processes. The results also revealed the crucial role of ABA in flavonoids synthesis and regulation of antioxidant system. Intriguingly, we also found that an inhibition of endogenous ABA significantly enhanced the transcriptional abundance of genes involved in photosynthesis. Our results highlighted the significance of ABA in regulating tomato ripening, which provided insight into the regulatory mechanism of fruit maturation and senescence process.

  10. ABA-stimulated SoDOG1 expression is after-ripening inhibited during early imbibition of germinating Sisymbrium officinale seeds.

    PubMed

    Carrillo-Barral, Néstor; Matilla, Angel J; García-Ramas, Cristina; Rodríguez-Gacio, María Del Carmen

    2015-12-01

    DELAY OF GERMINATION 1 (AtDOG1) was the first gene identified as dormancy-associated, but its physiological role in germination is far from being understood. Here, an orthologue of AtDOG1 in Sisymbrium officinale (SoDOG1; KM009050) is being reported. Phylogenetically, the SoDOG1 gene is included into the dicotyledonous group together with DOG1 from Arabidopsis thaliana (EF028470), Brassica rapa (AC189537), Lepidium papillosum (JX512183, JX512185) and Lepidium sativum (GQ411192). The SoDOG1 expression peaked at the onset of the silique maturation stage and there was presence of SoDOG1-mRNA in the freshly collected viable dry seed (i.e. AR0). The SoDOG1 transcripts were also found in other organs, such as open and closed flowers and to a lesser degree in roots and stems. We have previously reported in S. officinale seeds in which sensu stricto germination is positively affected by nitrate and both testa and micropylar endosperm ruptures are temporally separated. In dry viable seeds, the SoDOG1-mRNA level in three different after-ripening (AR) status was AR0 ≈ AR7 (optimal AR) < AR27 (optimal AR was almost lost). The presence of nitrate in the AR0 seed imbibition medium markedly decreased the SoDOG1 expression during sensu stricto germination. However, the nitrate stimulated the SoDOG1 expression during imbibition of AR7 compared to AR0. At the early AR0 seed imbibition (3-6 h), exogenous ABA provoked a very strong stimulation of the SoDOG1 expression. AR inhibits ABA-induced SoDOG1 expression during early germination and gibberellins (GA) can partially mimic this AR effect. A view on the integration of all found results in the sensu stricto germination of S. officinale was conducted.

  11. Effect of grain colour gene (R) on grain dormancy and sensitivity of the embryo to abscisic acid (ABA) in wheat.

    PubMed

    Himi, Eiko; Mares, Daryl J; Yanagisawa, Akira; Noda, Kazuhiko

    2002-07-01

    The level of grain dormancy and sensitivity to ABA of the embryo, a key factor in grain dormancy, were examined in developing grains of a white-grained wheat line, Novosibirskaya 67 (NS-67), and its red-grained near-isogenic lines (ANK-1A to -1D); a red-grained line, AUS 1490, and its white-grained mutant line (EMS-AUS). ANK lines showed higher levels of grain dormancy than NS-67 at harvest maturity. AUS 1490 grain also showed higher dormancy than EMS-AUS grain. These results suggest that the R gene for grain colour can enhance grain dormancy. However, the dormancy effect conferred by the R gene was not large, suggesting that it plays a minor role in the development of grain dormancy. Water extracts of AUS 1490 and EMS-AUS bran contained germination inhibitors equivalent to 1-10 microM ABA, although there was no difference in the amount of inhibitors between AUS 1490 and EMS-AUS. Thus, the grain colour gene of AUS 1490 did not appear to enhance the level of grain dormancy by accumulating germination inhibitors in its bran. Sensitivity to ABA of embryos was higher in grains collected around harvest-maturity for ANK lines and AUS 1490, compared with NS-67 and EMS-AUS. The R gene might enhance grain dormancy by increasing the sensitivity of embryos to ABA.

  12. Expression analysis of abscisic acid (ABA) and metabolic signalling factors in developing endosperm and embryo of barley☆

    PubMed Central

    Chen, Zhiwei; Huang, Jianhua; Muttucumaru, Nira; Powers, Stephen J.; Halford, Nigel G.

    2013-01-01

    The expression of genes encoding components of ABA and metabolic signalling pathways in developing barley endosperm and embryo was investigated. The genes included HvRCAR35_47387 and HvRCAR35_2538 (encoding ABA receptors), HvABI1d (protein phosphatase 2C), HvSnRK2.4, HvSnRK2.6 and HvPKABA1 (SnRK2-type protein kinases) and HvABI5 (ABA response element binding protein; AREBP), as well as two genes encoding SnRK1-type protein kinases. Both SnRK1 and SnRK2 phosphorylate AREBPs, but SnRK2 is activated by ABA whereas SnRK1 may be broken down. Multiple cereal AREBPs with two conserved SnRK1/2 target sites and another class of BZIP transcription factors with SnRK1/2 binding sites, including HvBLZ1, were identified. Barley grain (cv. Triumph) was sampled at 15, 20, 25 and 30 days post-anthesis (dpa). HvRCAR35_47387, HvABI1d, HvSnRK2.4 and HvABI5 were expressed highly in the endosperm but at much lower levels in the embryo. Conversely, HvPKABA1 and HvRCAR35_2538 were expressed at higher levels in the embryo than the endosperm, while HvSnRK2.6 was expressed at similar levels in both. HvRCAR35_47387, HvABI1d, HvSnRK2.4 and HvABI5 all peaked in expression in the endosperm at 20 dpa. A model is proposed in which ABA brings about a transition from a SnRK1-dominated state in the endosperm during grain filling to a SnRK2-dominated state during maturation. PMID:24748715

  13. BRI1-Associated Receptor Kinase 1 Regulates Guard Cell ABA Signaling Mediated by Open Stomata 1 in Arabidopsis.

    PubMed

    Shang, Yun; Dai, Changbo; Lee, Myeong Min; Kwak, June M; Nam, Kyoung Hee

    2016-03-01

    Stomatal movements are critical in regulating gas exchange for photosynthesis and water balance between plant tissues and the atmosphere. The plant hormone abscisic acid (ABA) plays key roles in regulating stomatal closure under various abiotic stresses. In this study, we revealed a novel role of BAK1 in guard cell ABA signaling. We found that the brassinosteroid (BR) signaling mutant bak1 lost more water than wild-type plants and showed ABA insensitivity in stomatal closure. ABA-induced OST1 expression and reactive oxygen species (ROS) production were also impaired in bak1. Unlike direct treatment with H2O2, overexpression of OST1 did not completely rescue the insensitivity of bak1 to ABA. We demonstrated that BAK1 forms a complex with OST1 near the plasma membrane and that the BAK1/OST1 complex is increased in response to ABA in planta. Brassinolide, the most active BR, exerted a negative effect on ABA-induced formation of the BAK1/OST1 complex and OST1 expression. Moreover, we found that BAK1 and ABI1 oppositely regulate OST1 phosphorylation in vitro, and that ABI1 interacts with BAK1 and inhibits the interaction of BAK1 and OST1. Taken together, our results suggest that BAK1 regulates ABA-induced stomatal closure in guard cells.

  14. Counteractive Effects of ABA and GA3 on Extracellular and Intracellular pH and Malate in Barley Aleurone.

    PubMed

    Heimovaara-Dijkstra, S.; Heistek, J. C.; Wang, M.

    1994-09-01

    Barley (Hordeum vulgare L.) aleurone layers are known to constitutively acidify their surroundings, primarily by L-malic acid release (J. Mikola, M. Virtanen [1980] Plant Physiol 66: S-142). Here we demonstrate the antagonistic effects of the plant hormones gibberellic acid (GA3) and abscisic acid (ABA) on the regulation of extracellular pH (pHe) of barley aleurone layers. We observed a strong correlation between ABA-induced enhancement of extracellular acidification and an ABA-induced increase in L-malic acid release. In addition, ABA caused an increase in intracellular L-malate level. GA3 caused a slight decrease in intracellular L-malate level and was able to inhibit the ABA-induced increase in L-malate intracellular concentration and release. In addition, this ABA-induced L-malate release could be completely inhibited by GA3. The ABA-induced release of L-malic acid could not account for the total ABA-induced pHe decrease, suggesting the existence of an additional mechanism involved in the regulation of pHe. It has been reported that ABA induces an intracellular pH (pHi) increase, possibly due to the activation of plasma membrane proton pumps (R. Van der Veen, S. Heimovaara-Dijkstra, M. Wang [1992] Plant Physiol 100: 699-705). A pHi increase, such as that caused by ABA, might be correlated with the intracellular L-malate increase as suggested by the pH stat model of D.D. Davies ([1986] Physiol Plant 67: 702-706). We studied if the effects of GA3 on L-malate concentration were correlated with changes in pHi and found that GA3 caused a pHi decrease and that GA3 and ABA could interfere in the regulation of pHi. In addition, we were able to mimic the effect of both hormones on L-malate release by bringing about artifical pHi changes with the weak acid 5,5-dimethyl-2,4-oxazolidinedione and the weak base methylamine. The physiological meaning of the effects of GA3 and ABA on the regulation of both pHe and pHi during grain germination are discussed.

  15. Counteractive Effects of ABA and GA3 on Extracellular and Intracellular pH and Malate in Barley Aleurone.

    PubMed Central

    Heimovaara-Dijkstra, S.; Heistek, J. C.; Wang, M.

    1994-01-01

    Barley (Hordeum vulgare L.) aleurone layers are known to constitutively acidify their surroundings, primarily by L-malic acid release (J. Mikola, M. Virtanen [1980] Plant Physiol 66: S-142). Here we demonstrate the antagonistic effects of the plant hormones gibberellic acid (GA3) and abscisic acid (ABA) on the regulation of extracellular pH (pHe) of barley aleurone layers. We observed a strong correlation between ABA-induced enhancement of extracellular acidification and an ABA-induced increase in L-malic acid release. In addition, ABA caused an increase in intracellular L-malate level. GA3 caused a slight decrease in intracellular L-malate level and was able to inhibit the ABA-induced increase in L-malate intracellular concentration and release. In addition, this ABA-induced L-malate release could be completely inhibited by GA3. The ABA-induced release of L-malic acid could not account for the total ABA-induced pHe decrease, suggesting the existence of an additional mechanism involved in the regulation of pHe. It has been reported that ABA induces an intracellular pH (pHi) increase, possibly due to the activation of plasma membrane proton pumps (R. Van der Veen, S. Heimovaara-Dijkstra, M. Wang [1992] Plant Physiol 100: 699-705). A pHi increase, such as that caused by ABA, might be correlated with the intracellular L-malate increase as suggested by the pH stat model of D.D. Davies ([1986] Physiol Plant 67: 702-706). We studied if the effects of GA3 on L-malate concentration were correlated with changes in pHi and found that GA3 caused a pHi decrease and that GA3 and ABA could interfere in the regulation of pHi. In addition, we were able to mimic the effect of both hormones on L-malate release by bringing about artifical pHi changes with the weak acid 5,5-dimethyl-2,4-oxazolidinedione and the weak base methylamine. The physiological meaning of the effects of GA3 and ABA on the regulation of both pHe and pHi during grain germination are discussed. PMID:12232334

  16. Root-to-shoot signalling when soil moisture is heterogeneous: increasing the proportion of root biomass in drying soil inhibits leaf growth and increases leaf abscisic acid concentration.

    PubMed

    Martin-Vertedor, Ana Isabel; Dodd, Ian C

    2011-07-01

    To determine whether root-to-shoot signalling of soil moisture heterogeneity depended on root distribution, wild-type (WT) and abscisic acid (ABA)-deficient (Az34) barley (Hordeum vulgare) plants were grown in split pots into which different numbers of seminal roots were inserted. After establishment, all plants received the same irrigation volumes, with one pot watered (w) and the other allowed to dry the soil (d), imposing three treatments (1 d: 3 w, 2 d: 2 w, 3 d: 1 w) that differed in the number of seminal roots exposed to drying soil. Root distribution did not affect leaf water relations and had no sustained effect on plant evapotranspiration (ET). In both genotypes, leaf elongation was less and leaf ABA concentrations were higher in plants with more roots in drying soil, with leaf ABA concentrations and water potentials 30% and 0.2 MPa higher, respectively, in WT plants. Whole-pot soil drying increased xylem ABA concentrations, but maximum values obtained when leaf growth had virtually ceased (100 nm in Az34, 330 nm in WT) had minimal effects (<40% leaf growth inhibition) when xylem supplied to detached shoots. Although ABA may not regulate leaf growth in vivo, genetic variation in foliar ABA concentration in the field may indicate different root distributions between upper (drier) and lower (wetter) soil layers.

  17. Root-to-shoot signalling when soil moisture is heterogeneous: increasing the proportion of root biomass in drying soil inhibits leaf growth and increases leaf abscisic acid concentration.

    PubMed

    Martin-Vertedor, Ana Isabel; Dodd, Ian C

    2011-07-01

    To determine whether root-to-shoot signalling of soil moisture heterogeneity depended on root distribution, wild-type (WT) and abscisic acid (ABA)-deficient (Az34) barley (Hordeum vulgare) plants were grown in split pots into which different numbers of seminal roots were inserted. After establishment, all plants received the same irrigation volumes, with one pot watered (w) and the other allowed to dry the soil (d), imposing three treatments (1 d: 3 w, 2 d: 2 w, 3 d: 1 w) that differed in the number of seminal roots exposed to drying soil. Root distribution did not affect leaf water relations and had no sustained effect on plant evapotranspiration (ET). In both genotypes, leaf elongation was less and leaf ABA concentrations were higher in plants with more roots in drying soil, with leaf ABA concentrations and water potentials 30% and 0.2 MPa higher, respectively, in WT plants. Whole-pot soil drying increased xylem ABA concentrations, but maximum values obtained when leaf growth had virtually ceased (100 nm in Az34, 330 nm in WT) had minimal effects (<40% leaf growth inhibition) when xylem supplied to detached shoots. Although ABA may not regulate leaf growth in vivo, genetic variation in foliar ABA concentration in the field may indicate different root distributions between upper (drier) and lower (wetter) soil layers. PMID:21410712

  18. Effects of ABA and CaCl₂ on GABA accumulation in fava bean germinating under hypoxia-NaCl stress.

    PubMed

    Yang, Runqiang; Hui, Qianru; Gu, Zhenxin

    2016-01-01

    Effects of exogenous abscisic acid (ABA) and CaCl2 on γ-aminobutyric acid (GABA) accumulation of germinated fava bean under hypoxia-NaCl stress were investigated. Exogenous ABA resulted in the enhancement of glutamate decarboxylase (GAD) and diamine oxidase (DAO) activity as well as GABA content in cotyledon and shoot. CaCl2 increased both enzyme activities in shoot and GABA content in cotyledon and shoot. ABA downregulated GAD expression in cotyledon and radicle, while upregulated that in shoot; it also upregulated DAO expression in each organ. CaCl2 upregulated GAD expression in cotyledon, while downregulated that in radicle. However, it upregulated DAO expression in shoot, downregulated that in radicle. ABA inhibitor fluridon and ethylenediaminetetraacetic acid inhibited GAD and DAO activities significantly so that inhibited GABA accumulation through reducing ABA biosynthesis and chelating Ca(2+), respectively. However, they upregulated GAD and DAO expression in varying degrees. These results indicate that ABA and Ca(2+) participate in GABA biosynthesis in fava bean during germination under hypoxia-NaCl stress.

  19. Effects of ABA and CaCl₂ on GABA accumulation in fava bean germinating under hypoxia-NaCl stress.

    PubMed

    Yang, Runqiang; Hui, Qianru; Gu, Zhenxin

    2016-01-01

    Effects of exogenous abscisic acid (ABA) and CaCl2 on γ-aminobutyric acid (GABA) accumulation of germinated fava bean under hypoxia-NaCl stress were investigated. Exogenous ABA resulted in the enhancement of glutamate decarboxylase (GAD) and diamine oxidase (DAO) activity as well as GABA content in cotyledon and shoot. CaCl2 increased both enzyme activities in shoot and GABA content in cotyledon and shoot. ABA downregulated GAD expression in cotyledon and radicle, while upregulated that in shoot; it also upregulated DAO expression in each organ. CaCl2 upregulated GAD expression in cotyledon, while downregulated that in radicle. However, it upregulated DAO expression in shoot, downregulated that in radicle. ABA inhibitor fluridon and ethylenediaminetetraacetic acid inhibited GAD and DAO activities significantly so that inhibited GABA accumulation through reducing ABA biosynthesis and chelating Ca(2+), respectively. However, they upregulated GAD and DAO expression in varying degrees. These results indicate that ABA and Ca(2+) participate in GABA biosynthesis in fava bean during germination under hypoxia-NaCl stress. PMID:26644273

  20. Pyrabactin, an ABA agonist, induced stomatal closure and changes in signalling components of guard cells in abaxial epidermis of Pisum sativum.

    PubMed

    Puli, Mallikarjuna Rao; Raghavendra, Agepati S

    2012-02-01

    Pyrabactin, a synthetic agonist of abscisic acid (ABA), inhibits seed germination and hypocotyl growth and stimulates gene expression in a very similar way to ABA, implying the possible modulation of stomatal function by pyrabactin as well. The effect of pyrabactin on stomatal closure and secondary messengers was therefore studied in guard cells of Pisum sativum abaxial epidermis. Pyrabactin caused marked stomatal closure in a pattern similar to ABA. In addition, pyrabactin elevated the levels of reactive oxygen species (ROS), nitric oxide (NO), and cytoplasmic pH levels in guard cells, as indicated by the respective fluorophores. However, apyrabactin, an inactive analogue of ABA, did not affect either stomatal closure or the signalling components of guard cells. The effects of pyrabactin-induced changes were reversed by pharmalogical compounds that modulate ROS, NO or cytoplasmic pH levels, quite similar to ABA effects. Fusicoccin, a fungal toxin, could reverse the stomatal closure caused by pyrabactin, as well as that caused by ABA. Experiments on stomatal closure by varying concentrations of ABA, in the presence of fixed concentration of pyrabactin, and vice versa, revealed that the actions of ABA and pyrabactin were additive. Further kinetic analysis of data revealed that the apparent K(D) of ABA was increased almost 4-fold in the presence of ABA, suggesting that pyrabactin and ABA were competing with each other either at the same site or close to the active site. It is proposed that pyrabactin could be used to examine the ABA-related signal-transduction components in stomatal guard cells as well as in other plant tissues. It is also suggested that pyrabactin can be used as an antitranspirant or as a priming agent for improving the drought tolerance of crop plants.

  1. Abscisic Acid Regulates Root Elongation Through the Activities of Auxin and Ethylene in Arabidopsis thaliana

    PubMed Central

    Thole, Julie M.; Beisner, Erin R.; Liu, James; Venkova, Savina V.; Strader, Lucia C.

    2014-01-01

    Abscisic acid (ABA) regulates many aspects of plant growth and development, including inhibition of root elongation and seed germination. We performed an ABA resistance screen to identify factors required for ABA response in root elongation inhibition. We identified two classes of Arabidopsis thaliana AR mutants that displayed ABA-resistant root elongation: those that displayed resistance to ABA in both root elongation and seed germination and those that displayed resistance to ABA in root elongation but not in seed germination. We used PCR-based genotyping to identify a mutation in ABA INSENSITIVE2 (ABI2), positional information to identify mutations in AUXIN RESISTANT1 (AUX1) and ETHYLENE INSENSITIVE2 (EIN2), and whole genome sequencing to identify mutations in AUX1, AUXIN RESISTANT4 (AXR4), and ETHYLENE INSENSITIVE ROOT1/PIN-FORMED2 (EIR1/PIN2). Identification of auxin and ethylene response mutants among our isolates suggested that auxin and ethylene responsiveness were required for ABA inhibition of root elongation. To further our understanding of auxin/ethylene/ABA crosstalk, we examined ABA responsiveness of double mutants of ethylene overproducer1 (eto1) or ein2 combined with auxin-resistant mutants and found that auxin and ethylene likely operate in a linear pathway to affect ABA-responsive inhibition of root elongation, whereas these two hormones likely act independently to affect ABA-responsive inhibition of seed germination. PMID:24836325

  2. Abscisic acid regulates root elongation through the activities of auxin and ethylene in Arabidopsis thaliana.

    PubMed

    Thole, Julie M; Beisner, Erin R; Liu, James; Venkova, Savina V; Strader, Lucia C

    2014-05-15

    Abscisic acid (ABA) regulates many aspects of plant growth and development, including inhibition of root elongation and seed germination. We performed an ABA resistance screen to identify factors required for ABA response in root elongation inhibition. We identified two classes of Arabidopsis thaliana AR mutants that displayed ABA-resistant root elongation: those that displayed resistance to ABA in both root elongation and seed germination and those that displayed resistance to ABA in root elongation but not in seed germination. We used PCR-based genotyping to identify a mutation in ABA INSENSITIVE2 (ABI2), positional information to identify mutations in AUXIN RESISTANT1 (AUX1) and ETHYLENE INSENSITIVE2 (EIN2), and whole genome sequencing to identify mutations in AUX1, AUXIN RESISTANT4 (AXR4), and ETHYLENE INSENSITIVE ROOT1/PIN-FORMED2 (EIR1/PIN2). Identification of auxin and ethylene response mutants among our isolates suggested that auxin and ethylene responsiveness were required for ABA inhibition of root elongation. To further our understanding of auxin/ethylene/ABA crosstalk, we examined ABA responsiveness of double mutants of ethylene overproducer1 (eto1) or ein2 combined with auxin-resistant mutants and found that auxin and ethylene likely operate in a linear pathway to affect ABA-responsive inhibition of root elongation, whereas these two hormones likely act independently to affect ABA-responsive inhibition of seed germination.

  3. Nickel inhibits mitochondrial fatty acid oxidation.

    PubMed

    Uppala, Radha; McKinney, Richard W; Brant, Kelly A; Fabisiak, James P; Goetzman, Eric S

    2015-08-01

    Nickel exposure is associated with changes in cellular energy metabolism which may contribute to its carcinogenic properties. Here, we demonstrate that nickel strongly represses mitochondrial fatty acid oxidation-the pathway by which fatty acids are catabolized for energy-in both primary human lung fibroblasts and mouse embryonic fibroblasts. At the concentrations used, nickel suppresses fatty acid oxidation without globally suppressing mitochondrial function as evidenced by increased glucose oxidation to CO2. Pre-treatment with l-carnitine, previously shown to prevent nickel-induced mitochondrial dysfunction in neuroblastoma cells, did not prevent the inhibition of fatty acid oxidation. The effect of nickel on fatty acid oxidation occurred only with prolonged exposure (>5 h), suggesting that direct inhibition of the active sites of metabolic enzymes is not the mechanism of action. Nickel is a known hypoxia-mimetic that activates hypoxia inducible factor-1α (HIF1α). Nickel-induced inhibition of fatty acid oxidation was blunted in HIF1α knockout fibroblasts, implicating HIF1α as one contributor to the mechanism. Additionally, nickel down-regulated the protein levels of the key fatty acid oxidation enzyme very long-chain acyl-CoA dehydrogenase (VLCAD) in a dose-dependent fashion. In conclusion, inhibition of fatty acid oxidation by nickel, concurrent with increased glucose metabolism, represents a form of metabolic reprogramming that may contribute to nickel-induced carcinogenesis.

  4. Nickel Inhibits Mitochondrial Fatty Acid Oxidation

    PubMed Central

    Uppala, Radha; McKinney, Richard W.; Brant, Kelly A.; Fabisiak, James P.; Goetzman, Eric S.

    2015-01-01

    Nickel exposure is associated with changes in cellular energy metabolism which may contribute to its carcinogenic properties. Here, we demonstrate that nickel strongly represses mitochondrial fatty acid oxidation—the pathway by which fatty acids are catabolized for energy—in both primary human lung fibroblasts and mouse embryonic fibroblasts. At the concentrations used, nickel suppresses fatty acid oxidation without globally suppressing mitochondrial function as evidenced by increased glucose oxidation to CO2. Pre-treatment with L-carnitine, previously shown to prevent nickel-induced mitochondrial dysfunction in neuroblastoma cells, did not prevent the inhibition of fatty acid oxidation. The effect of nickel on fatty acid oxidation occurred only with prolonged exposure (>5 hr), suggesting that direct inhibition of the active sites of metabolic enzymes is not the mechanism of action. Nickel is a known hypoxia-mimetic that activates hypoxia inducible factor-1α (HIF1α). Nickel-induced inhibition of fatty acid oxidation was blunted in HIF1α knockout fibroblasts, implicating HIF1α as one contributor to the mechanism. Additionally, nickel down-regulated the protein levels of the key fatty acid oxidation enzyme very long-chain acyl-CoA dehydrogenase (VLCAD) in a dose-dependent fashion. In conclusion, inhibition of fatty acid oxidation by nickel, concurrent with increased glucose metabolism, represents a form of metabolic reprogramming that may contribute to nickel-induced carcinogenesis. PMID:26051273

  5. A rice dehydration-inducible SNF1-related protein kinase 2 phosphorylates an abscisic acid responsive element-binding factor and associates with ABA signaling.

    PubMed

    Chae, Min-Ju; Lee, Jung-Sook; Nam, Myung-Hee; Cho, Kun; Hong, Ji-Yeon; Yi, Sang-A; Suh, Seok-Cheol; Yoon, In-Sun

    2007-01-01

    By a differential cDNA screening technique, we have isolated a dehydration-inducible gene (designated OSRK1) that encodes a 41.8 kD protein kinase of SnRK2 family from Oryza sativa. The OSRK1 transcript level was undetectable in vegetative tissues, but significantly increased by hyperosmotic stress and Abscisic acid (ABA). To determine its biochemical properties, we expressed and isolated OSRK1 and its mutants as glutathione S-transferase fusion proteins in Escherichia coli. In vitro kinase assay showed that OSRK1 can phosphorylate itself and generic substrates as well. Interestingly, OSRK1 showed strong substrate preference for rice bZIP transcription factors and uncommon cofactor requirement for Mn(2+) over Mg(2+). By deletion of C-terminus 73 amino acids or mutations of Ser-158 and Thr-159 to aspartic acids (Asp) in the activation loop, the activity of OSRK1 was dramatically decreased. OSRK1 can transphosphorylate the inactive deletion protein. A rice family of abscisic acid-responsive element (ABRE) binding factor, OREB1 was phosphorylated in vitro by OSRK1 at multiple sites of different functional domains. MALDI-TOF analysis identified a phosphorylation site at Ser44 of OREB1 and mutation of the residue greatly decreased the substrate specificity for OSRK1. The recognition motif for OSRK1, RQSS is highly similar to the consensus substrate sequence of AMPK/SNF1 kinase family. We further showed that OSRK1 interacts with OREB1 in a yeast two-hybrid system and co-localized to nuclei by transient expression analysis of GFP-fused protein in onion epidermis. Finally, ectopic expression of OSRK1 in transgenic tobacco resulted in a reduced sensitivity to ABA in seed germination and root elongation. These findings suggest that OSRK1 is associated with ABA signaling, possibly through the phosphorylation of ABF family in vivo. The interaction between SnRK2 family kinases and ABF transcription factors may constitute an important part of cross-talk mechanism in the stress

  6. Nitric oxide modulates sensitivity to ABA.

    PubMed

    Lozano-Juste, Jorge; León, José

    2010-03-01

    Nitric oxide (NO) is a gas with crucial signaling functions in plant defense and development. As demonstrated by generating a triple nia1nia2noa1-2 mutant with extremely low levels of NO (February 2010 issue of Plant Physiology), NO is synthesized in plants through mainly two different pathways involving nitrate reductase (NR/NIA) and NO Associated 1 (AtNOA1) proteins. Depletion of basal NO levels leads to a priming of ABA-triggered responses that causes hypersensitivity to this hormone and results in enhanced seed dormancy and decreased seed germination and seedling establishment in the triple mutant. NO produced under non-stressed conditions represses inhibition of seed developmental transitions by ABA. Moreover, NO plays a positive role in post-germinative vegetative development and also exerts a critical control of ABA-related functions on stomata closure. The triple nia1nia2noa1-2 mutant is hypersensitive to ABA in stomatal closure thus resulting in a extreme phenotype of resistance to drought. In the light of the recent discovery of PYR/PYL/RCAR as a family of potential ABA receptors, regulation of ABA sensitivity by NO may be exerted either directly on ABA receptors or on downstream signaling components; both two aspects that deserve our present and future attention.

  7. PLASTID MOVEMENT IMPAIRED1 mediates ABA sensitivity during germination and implicates ABA in light-mediated Chloroplast movements.

    PubMed

    Rojas-Pierce, Marcela; Whippo, Craig W; Davis, Phillip A; Hangarter, Roger P; Springer, Patricia S

    2014-10-01

    The plant hormone abscisic acid (ABA) controls many aspects of plant growth and development, including seed development, germination and responses to water-deficit stress. A complex ABA signaling network integrates environmental signals including water availability and light intensity and quality to fine-tune the response to a changing environment. To further define the regulatory pathways that control water-deficit and ABA responses, we carried out a gene-trap tagging screen for water-deficit-regulated genes in Arabidopsis thaliana. This screen identified PLASTID MOVEMENT IMPAIRED1 (PMI1), a gene involved in blue-light-induced chloroplast movement, as functioning in ABA-response pathways. We provide evidence that PMI1 is involved in the regulation of seed germination by ABA, acting upstream of the intersection between ABA and low-glucose signaling pathways. Furthermore, PMI1 participates in the regulation of ABA accumulation during periods of water deficit at the seedling stage. The combined phenotypes of pmi1 mutants in chloroplast movement and ABA responses indicate that ABA signaling may modulate chloroplast motility. This result was further supported by the detection of altered chloroplast movements in the ABA mutants aba1-6, aba2-1 and abi1-1.

  8. Plant growth inhibition by cis-cinnamoyl glucosides and cis-cinnamic acid.

    PubMed

    Hiradate, Syuntaro; Morita, Sayaka; Furubayashi, Akihiro; Fujii, Yoshiharu; Harada, Jiro

    2005-03-01

    Spiraea thunbergii Sieb. contains 1-O-cis-cinnamoyl-beta-D-glucopyranose (CG) and 6-O-(4'-hydroxy-2'-methylene-butyroyl)-1-O-cis-cinnamoyl-beta-D-glucopyranose (BCG) as major plant growth inhibiting constituents. In the present study, we determined the inhibitory activity of CG and BCG on root elongation of germinated seedlings of lettuce (Lactuca sativa), pigweed (Amaranthus retroflexus), red clover (Trifolium pratense), timothy (Phleum pratense), and bok choy (Brassica rapa var chinensis) in comparison with that of two well-known growth inhibitors, 2,4-dichlorophenoxyacetic acid (2,4-D) and (+)-2-cis-4-trans-abscisic acid (cis-ABA), as well as two related chemicals of CG and BCG, cis-cinnamic acid (cis-CA) and trans-cinnamic acid (trans-CA). The EC50 values for CG and BCG on lettuce were roughly one-half to one-quarter of the value for cis-ABA. cis-Cinnamic acid, which is a component of CG and BCG, possessed almost the same inhibitory activity of CG and BCG, suggesting that the essential chemical structure responsible for the inhibitory activity of CG and BCG is cis-CA. The cis-stereochemistry of the methylene moiety is apparently needed for high inhibitory activity, as trans-CA had an EC50 value roughly 100 times that of CG, BCG, and cis-CA. Growth inhibition by CG, BCG, and cis-CA was influenced by the nature of the soil in the growing medium: alluvial soil preserved the bioactivity, whereas volcanic ash and calcareous soils inhibited bioactivity. These findings indicate a potential role of cis-CA and its glucosides as allelochemicals for use as plant growth regulators in agricultural fields.

  9. Plant growth inhibition by cis-cinnamoyl glucosides and cis-cinnamic acid.

    PubMed

    Hiradate, Syuntaro; Morita, Sayaka; Furubayashi, Akihiro; Fujii, Yoshiharu; Harada, Jiro

    2005-03-01

    Spiraea thunbergii Sieb. contains 1-O-cis-cinnamoyl-beta-D-glucopyranose (CG) and 6-O-(4'-hydroxy-2'-methylene-butyroyl)-1-O-cis-cinnamoyl-beta-D-glucopyranose (BCG) as major plant growth inhibiting constituents. In the present study, we determined the inhibitory activity of CG and BCG on root elongation of germinated seedlings of lettuce (Lactuca sativa), pigweed (Amaranthus retroflexus), red clover (Trifolium pratense), timothy (Phleum pratense), and bok choy (Brassica rapa var chinensis) in comparison with that of two well-known growth inhibitors, 2,4-dichlorophenoxyacetic acid (2,4-D) and (+)-2-cis-4-trans-abscisic acid (cis-ABA), as well as two related chemicals of CG and BCG, cis-cinnamic acid (cis-CA) and trans-cinnamic acid (trans-CA). The EC50 values for CG and BCG on lettuce were roughly one-half to one-quarter of the value for cis-ABA. cis-Cinnamic acid, which is a component of CG and BCG, possessed almost the same inhibitory activity of CG and BCG, suggesting that the essential chemical structure responsible for the inhibitory activity of CG and BCG is cis-CA. The cis-stereochemistry of the methylene moiety is apparently needed for high inhibitory activity, as trans-CA had an EC50 value roughly 100 times that of CG, BCG, and cis-CA. Growth inhibition by CG, BCG, and cis-CA was influenced by the nature of the soil in the growing medium: alluvial soil preserved the bioactivity, whereas volcanic ash and calcareous soils inhibited bioactivity. These findings indicate a potential role of cis-CA and its glucosides as allelochemicals for use as plant growth regulators in agricultural fields. PMID:15898503

  10. Abscisic acid in soil facilitates community succession in three forests in China.

    PubMed

    Zhao, Houben; Peng, Shaolin; Chen, Zhuoquan; Wu, Zhongmin; Zhou, Guangyi; Wang, Xu; Qiu, Zhijun

    2011-07-01

    Plants release secondary metabolites into the soil that change the chemical environment around them. Exogenous abscisic acid (ABA) is an important allelochemical whose role in successional trajectories has not been examined. We hypothesized that ABA can accumulate in the soil through successional processes and have an influence on forest dynamics. To this end, we investigated the distribution of ABA in forest communities from early to late successional stages and the response of dominant species to the gradient of ABA concentrations in three types of forests from northern to southern China. Concentrations of ABA in the soils of three forest types increased from early to late successional stages. Pioneer species' litters had the lowest ABA content, and their seed germination and seedling early growth were the most sensitive to the inhibitory effect of ABA. Mid- and late-successional species had a much higher ABA content in fallen leaves than pioneer species, and their seed germination and seedling early growth were inhibited by higher concentrations of ABA than pioneers. Late-successional species showed little response to the highest ABA concentration, possibly due to their large seed size. The results suggest that ABA accumulates in the soil as community succession proceeds. Sensitivity to ABA in the early stages, associated with other characteristics, may result in pioneer species losing their advantage in competition with late-successional species in an increasingly high ABA concentration environment, and being replaced by ABA-tolerant, late-successional species.

  11. Abscisic acid induces a cytosolic calcium decrease in barley aleurone protoplasts.

    PubMed

    Wang, M; Van Duijn, B; Schram, A W

    1991-01-14

    Cytosolic calcium concentrations (Cai) of barley aleurone protoplasts after stimulation with the plant hormone abscisic acid (ABA) were measured by using the calcium-sensitive fluorescent dye Indo-1. The measured basal Cai is about 200 nM. Stimulation with ABA induces a strong dose-dependent decrease in Cai to a minimal value of about 50 nM. This decrease occurs within 5 s. The Ca2+ antagonists La3+ and Cd2+ inhibit the ABA-induced Cai decrease in a dose-dependent manner, while the Ca2+ channel blockers verapamil and nifedipine give no inhibition. The induction of Cai decrease by ABA is consistent with activation of the plasma membrane Ca2(+)-ATPase by ABA. The possible role of this ABA-induced Cai decrease in ABA signal transduction and in counteracting the effects of gibberellic acid are discussed.

  12. The induction of free proline accumulation by endogenous ABA in Arabidopsis thaliana during drought

    SciTech Connect

    Gottlieb, M.L.; Bray, E.A. )

    1991-05-01

    Endogenous levels of abscisic acid (ABA) and free proline increase in response to drought stress. Exogenous ABA has been shown to induce proline accumulation, suggesting that ABA triggers the amino acid response. To determine if endogenous ABA induces free proline accumulation, increases in ABA and proline during drought stress were compared between wild type (WT), ABA-insensitive (abi) and ABA-deficient (aba) mutants of Arabidopsis thaliana. If elevated levels of endogenous ABA signal the proline response, then the mutants would not be expected to accumulate proline during stress. abi should be unable to respond to increased levels of endogenous ABA, while aba should be unable to accumulate sufficient ABA to elicit a proline response. Drought-stressed three week old shoots of WT, abi, and aba exhibited different patterns of endogenous ABA accumulation, but similar patterns of proline accumulation over 24 hours. Although the patterns of endogenous ABA accumulation differed, maximum levels were similar in WT and abi, but aba produced approximately 25% less. However, free proline accumulated in all three plant lines. abi exhibited a greater, more rapid increase in free proline over that in either WT or aba. aba, however, showed the same pattern and levels of accumulation as that in WT. Since free proline accumulated to at least similar levels in both WT and mutants, regardless of the levels of ABA accumulation, it may be that only a small endogenous ABA accumulation is required for proline accumulation. Alternatively, endogenous ABA may not be the direct signal for the proline response during drought stress.

  13. NRGA1, a putative mitochondrial pyruvate carrier, mediates ABA regulation of guard cell ion channels and drought stress responses in Arabidopsis.

    PubMed

    Li, Chun-Long; Wang, Mei; Ma, Xiao-Yan; Zhang, Wei

    2014-10-01

    Abscisic acid (ABA) regulates ion channel activity and stomatal movements in response to drought and other stresses. Here, we show that the Arabidopsis thaliana gene NRGA1 is a putative mitochondrial pyruvate carrier which negatively regulates ABA-induced guard cell signaling. NRGA1 transcript was abundant in the A. thaliana leaf and particularly in the guard cells, and its product was directed to the mitochondria. The heterologous co-expression of NRGA1 and AtMPC1 in yeast complemented a loss-of-function mitochondrial pyruvate carrier (MPC) mutant. The nrga1 loss-of-function mutant was very sensitive to the presence of ABA in the context of stomatal movements, and exhibited a heightened tolerance to drought stress. Disruption of NRGA1 gene resulted in increased ABA inhibition of inward K(+) currents and ABA activation of slow anion currents in guard cells. The nrga1/NRGA1 functional complementation lines restored the mutant's phenotypes. Furthermore, transgenic lines of constitutively overexpressing NRGA1 showed opposite stomatal responses, reduced drought tolerance, and ABA sensitivity of guard cell inward K(+) channel inhibition and anion channel activation. Our findings highlight a putative role for the mitochondrial pyruvate carrier in guard cell ABA signaling in response to drought.

  14. Understanding biocatalyst inhibition by carboxylic acids

    PubMed Central

    Jarboe, Laura R.; Royce, Liam A.; Liu, Ping

    2013-01-01

    Carboxylic acids are an attractive biorenewable chemical in terms of their flexibility and usage as precursors for a variety of industrial chemicals. It has been demonstrated that such carboxylic acids can be fermentatively produced using engineered microbes, such as Escherichia coli and Saccharomyces cerevisiae. However, like many other attractive biorenewable fuels and chemicals, carboxylic acids become inhibitory to these microbes at concentrations below the desired yield and titer. In fact, their potency as microbial inhibitors is highlighted by the fact that many of these carboxylic acids are routinely used as food preservatives. This review highlights the current knowledge regarding the impact that saturated, straight-chain carboxylic acids, such as hexanoic, octanoic, decanoic, and lauric acids can have on E. coli and S. cerevisiae, with the goal of identifying metabolic engineering strategies to increase robustness. Key effects of these carboxylic acids include damage to the cell membrane and a decrease of the microbial internal pH. Certain changes in cell membrane properties, such as composition, fluidity, integrity, and hydrophobicity, and intracellular pH are often associated with increased tolerance. The availability of appropriate exporters, such as Pdr12, can also increase tolerance. The effect on metabolic processes, such as maintaining appropriate respiratory function, regulation of Lrp activity and inhibition of production of key metabolites such as methionine, are also considered. Understanding the mechanisms of biocatalyst inhibition by these desirable products can aid in the engineering of robust strains with improved industrial performance. PMID:24027566

  15. Grafting cucumber onto luffa improves drought tolerance by increasing ABA biosynthesis and sensitivity.

    PubMed

    Liu, Shanshan; Li, Hao; Lv, Xiangzhang; Ahammed, Golam Jalal; Xia, Xiaojian; Zhou, Jie; Shi, Kai; Asami, Tadao; Yu, Jingquan; Zhou, Yanhong

    2016-01-01

    Balancing stomata-dependent CO2 assimilation and transpiration is a key challenge for increasing crop productivity and water use efficiency under drought stress for sustainable crop production worldwide. Here, we show that cucumber and luffa plants with luffa as rootstock have intrinsically increased water use efficiency, decreased transpiration rate and less affected CO2 assimilation capacity following drought stress over those with cucumber as rootstock. Drought accelerated abscisic acid (ABA) accumulation in roots, xylem sap and leaves, and induced the transcript of ABA signaling genes, leading to a decreased stomatal aperture and transpiration in the plants grafted onto luffa roots as compared to plants grafted onto cucumber roots. Furthermore, stomatal movement in the plants grafted onto luffa roots had an increased sensitivity to ABA. Inhibition of ABA biosynthesis in luffa roots decreased the drought tolerance in cucumber and luffa plants. Our study demonstrates that the roots of luffa have developed an enhanced ability to sense the changes in root-zone moisture and could eventually deliver modest level of ABA from roots to shoots that enhances water use efficiency under drought stress. Such a mechanism could be greatly exploited to benefit the agricultural production especially in arid and semi-arid areas. PMID:26832070

  16. Grafting cucumber onto luffa improves drought tolerance by increasing ABA biosynthesis and sensitivity

    PubMed Central

    Liu, Shanshan; Li, Hao; Lv, Xiangzhang; Ahammed, Golam Jalal; Xia, Xiaojian; Zhou, Jie; Shi, Kai; Asami, Tadao; Yu, Jingquan; Zhou, Yanhong

    2016-01-01

    Balancing stomata-dependent CO2 assimilation and transpiration is a key challenge for increasing crop productivity and water use efficiency under drought stress for sustainable crop production worldwide. Here, we show that cucumber and luffa plants with luffa as rootstock have intrinsically increased water use efficiency, decreased transpiration rate and less affected CO2 assimilation capacity following drought stress over those with cucumber as rootstock. Drought accelerated abscisic acid (ABA) accumulation in roots, xylem sap and leaves, and induced the transcript of ABA signaling genes, leading to a decreased stomatal aperture and transpiration in the plants grafted onto luffa roots as compared to plants grafted onto cucumber roots. Furthermore, stomatal movement in the plants grafted onto luffa roots had an increased sensitivity to ABA. Inhibition of ABA biosynthesis in luffa roots decreased the drought tolerance in cucumber and luffa plants. Our study demonstrates that the roots of luffa have developed an enhanced ability to sense the changes in root-zone moisture and could eventually deliver modest level of ABA from roots to shoots that enhances water use efficiency under drought stress. Such a mechanism could be greatly exploited to benefit the agricultural production especially in arid and semi-arid areas. PMID:26832070

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

    PubMed

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

    2007-02-01

    Abscisic acid (ABA) is an important phytohormone that plays a critical role in seed development, dormancy, and stress tolerance. 9-cis-Epoxycarotenoid dioxygenase is the key enzyme controlling ABA biosynthesis and stress tolerance. In this study, we investigated the effect of ectopic expression of another ABA biosynthesis gene, ABA2 (or GLUCOSE INSENSITIVE 1 [GIN1]) encoding a short-chain dehydrogenase/reductase in Arabidopsis (Arabidopsis thaliana). We show that ABA2-overexpressing transgenic plants with elevated ABA levels exhibited seed germination delay and more tolerance to salinity than wild type when grown on agar plates and/or in soil. However, the germination delay was abolished in transgenic plants showing ABA levels over 2-fold higher than that of wild type grown on 250 mm NaCl. The data suggest that there are distinct mechanisms underlying ABA-mediated inhibition of seed germination under diverse stress. The ABA-deficient mutant aba2, with a shorter primary root, can be restored to normal root growth by exogenous application of ABA, whereas transgenic plants overexpressing ABA2 showed normal root growth. The data reflect that the basal levels of ABA are essential for maintaining normal primary root elongation. Furthermore, analysis of ABA2 promoter activity with ABA2::beta-glucuronidase transgenic plants revealed that the promoter activity was enhanced by multiple prolonged stresses, such as drought, salinity, cold, and flooding, but not by short-term stress treatments. Coincidently, prolonged drought stress treatment led to the up-regulation of ABA biosynthetic and sugar-related genes. Thus, the data support ABA2 as a late expression gene that might have a fine-tuning function in mediating ABA biosynthesis through primary metabolic changes in response to stress. PMID:17189333

  18. The Heat Stress Factor HSFA6b Connects ABA Signaling and ABA-Mediated Heat Responses1[OPEN

    PubMed Central

    Yang, Chen-Ru

    2016-01-01

    Heat stress response (HSR) is a conserved mechanism developed to increase the expression of heat shock proteins (HSPs) via a heat shock factor (HSF)-dependent mechanism. Signaling by the stress phytohormone abscisic acid (ABA) is involved in acquired thermotolerance as well. Analysis of Arabidopsis (Arabidopsis thaliana) microarray databases revealed that the expression of HSFA6b, a class A HSF, extensively increased with salinity, osmotic, and cold stresses, but not heat. Here, we show that HSFA6b plays a pivotal role in the response to ABA and in thermotolerance. Salt-inducible HSFA6b expression was down-regulated in ABA-insensitive and -deficient mutants; however, exogenous ABA application restored expression in ABA-deficient, but not -insensitive plants. Thus, ABA signaling is required for proper HSFA6b expression. A transcriptional activation assay of protoplasts revealed that ABA treatment and coexpression of an ABA signaling master effector, ABA-RESPONSIVE ELEMENT-BINDING PROTEIN1, could activate the HSFA6b promoter. In addition, HSFA6b directly bound to the promoter of DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN2A and enhanced its expression. Analysis of ABA responses in seed germination, cotyledon greening, and root growth as well as salt and drought tolerance in HSFA6b-null, overexpression, and dominant negative mutants revealed that HSFA6b is a positive regulator participating in ABA-mediated salt and drought resistance. Thermoprotection tests showed that HSFA6b was required for thermotolerance acquisition. Our study reveals a network in which HSFA6b operates as a downstream regulator of the ABA-mediated stress response and is required for heat stress resistance. This new ABA-signaling pathway is integrated into the complex HSR network in planta. PMID:27493213

  19. The evolution of the role of ABA in the regulation of water-use efficiency: From biochemical mechanisms to stomatal conductance.

    PubMed

    Negin, Boaz; Moshelion, Menachem

    2016-10-01

    Abscisic acid is found in a wide variety of organisms. In the plant kingdom, ABA's role in mediating responses to abiotic stress has been conserved and enhanced throughout evolution. The emergence of plants to terrestrial environments required the development of mechanisms to cope with ongoing and severe abiotic stress such as drought and rapid changes in humidity and temperature. The common understanding is that terrestrial plants evolved strategies ranging from desiccation-tolerance mechanisms (mosses) to drought tolerance (CAM plants), to better exploit different ecological niches. In between these divergent water regulation strategies, ABA plays a significant role in managing plants' adaptation to new environments by optimizing water-use efficiency (WUE) under particular environmental conditions. ABA plays some very different roles in the regulation of WUE. ABA's role in the regulation of guard cells and transpiration has yielded a wide variety of WUE-regulation mechanisms, ranging from no sensitivity (ferns) to low sensitivity (anisohydric behavior) to hypersensitivity to ABA (isohydric behavior and putatively CAM plants). ABA also plays a role in the regulation of non-stomatal, biochemical mechanisms of WUE regulation. In angiosperms, this includes the control of osmotic adjustment and morphological changes, including changes in leaf size, stomatal density, stomatal size and root development. Under severe stress, ABA also appears to initiate leaf senescence via transcriptional regulation, to directly inhibit photosynthesis. PMID:27593466

  20. The evolution of the role of ABA in the regulation of water-use efficiency: From biochemical mechanisms to stomatal conductance.

    PubMed

    Negin, Boaz; Moshelion, Menachem

    2016-10-01

    Abscisic acid is found in a wide variety of organisms. In the plant kingdom, ABA's role in mediating responses to abiotic stress has been conserved and enhanced throughout evolution. The emergence of plants to terrestrial environments required the development of mechanisms to cope with ongoing and severe abiotic stress such as drought and rapid changes in humidity and temperature. The common understanding is that terrestrial plants evolved strategies ranging from desiccation-tolerance mechanisms (mosses) to drought tolerance (CAM plants), to better exploit different ecological niches. In between these divergent water regulation strategies, ABA plays a significant role in managing plants' adaptation to new environments by optimizing water-use efficiency (WUE) under particular environmental conditions. ABA plays some very different roles in the regulation of WUE. ABA's role in the regulation of guard cells and transpiration has yielded a wide variety of WUE-regulation mechanisms, ranging from no sensitivity (ferns) to low sensitivity (anisohydric behavior) to hypersensitivity to ABA (isohydric behavior and putatively CAM plants). ABA also plays a role in the regulation of non-stomatal, biochemical mechanisms of WUE regulation. In angiosperms, this includes the control of osmotic adjustment and morphological changes, including changes in leaf size, stomatal density, stomatal size and root development. Under severe stress, ABA also appears to initiate leaf senescence via transcriptional regulation, to directly inhibit photosynthesis.

  1. BRASSINOSTEROID INSENSITIVE2 interacts with ABSCISIC ACID INSENSITIVE5 to mediate the antagonism of brassinosteroids to abscisic acid during seed germination in Arabidopsis.

    PubMed

    Hu, Yanru; Yu, Diqiu

    2014-11-01

    Seed germination and postgerminative growth are regulated by a delicate hormonal balance. Abscisic acid (ABA) represses Arabidopsis thaliana seed germination and postgerminative growth, while brassinosteroids (BRs) antagonize ABA-mediated inhibition and promote these processes. However, the molecular mechanism underlying BR-repressed ABA signaling remains largely unknown. Here, we show that the Glycogen Synthase Kinase 3-like kinase BRASSINOSTEROID INSENSITIVE2 (BIN2), a critical repressor of BR signaling, positively regulates ABA responses during seed germination and postgerminative growth. Mechanistic investigation revealed that BIN2 physically interacts with ABSCISIC ACID INSENSITIVE5 (ABI5), a bZIP transcription factor. Further genetic analysis demonstrated that the ABA-hypersensitive phenotype of BIN2-overexpressing plants requires ABI5. BIN2 was found to phosphorylate and stabilize ABI5 in the presence of ABA, while application of epibrassinolide (the active form of BRs) inhibited the regulation of ABI5 by BIN2. Consistently, the ABA-induced accumulation of ABI5 was affected in BIN2-related mutants. Moreover, mutations of the BIN2 phosphorylation sites on ABI5 made the mutant protein respond to ABA improperly. Additionally, the expression of several ABI5 regulons was positively modulated by BIN2. These results provide evidence that BIN2 phosphorylates and stabilizes ABI5 to mediate ABA response during seed germination, while BRs repress the BIN2-ABI5 cascade to antagonize ABA-mediated inhibition.

  2. BRASSINOSTEROID INSENSITIVE2 Interacts with ABSCISIC ACID INSENSITIVE5 to Mediate the Antagonism of Brassinosteroids to Abscisic Acid during Seed Germination in Arabidopsis[W

    PubMed Central

    Hu, Yanru; Yu, Diqiu

    2014-01-01

    Seed germination and postgerminative growth are regulated by a delicate hormonal balance. Abscisic acid (ABA) represses Arabidopsis thaliana seed germination and postgerminative growth, while brassinosteroids (BRs) antagonize ABA-mediated inhibition and promote these processes. However, the molecular mechanism underlying BR-repressed ABA signaling remains largely unknown. Here, we show that the Glycogen Synthase Kinase 3-like kinase BRASSINOSTEROID INSENSITIVE2 (BIN2), a critical repressor of BR signaling, positively regulates ABA responses during seed germination and postgerminative growth. Mechanistic investigation revealed that BIN2 physically interacts with ABSCISIC ACID INSENSITIVE5 (ABI5), a bZIP transcription factor. Further genetic analysis demonstrated that the ABA-hypersensitive phenotype of BIN2-overexpressing plants requires ABI5. BIN2 was found to phosphorylate and stabilize ABI5 in the presence of ABA, while application of epibrassinolide (the active form of BRs) inhibited the regulation of ABI5 by BIN2. Consistently, the ABA-induced accumulation of ABI5 was affected in BIN2-related mutants. Moreover, mutations of the BIN2 phosphorylation sites on ABI5 made the mutant protein respond to ABA improperly. Additionally, the expression of several ABI5 regulons was positively modulated by BIN2. These results provide evidence that BIN2 phosphorylates and stabilizes ABI5 to mediate ABA response during seed germination, while BRs repress the BIN2-ABI5 cascade to antagonize ABA-mediated inhibition. PMID:25415975

  3. ABA flow modelling in Ricinus communis exposed to salt stress and variable nutrition

    PubMed Central

    Peuke, Andreas D.

    2016-01-01

    In a series of experiments with Ricinus communis, abscisic acid (ABA) concentrations in tissues and transport saps, its de novo biosynthesis, long-distance transport, and metabolism (degradation) were affected by nutritional conditions, nitrogen (N) source, and nutrient limitation, or salt stress. In the present study these data were statistically re-evaluated, and new correlations presented that underpin the importance of this universal phytohormone. The biggest differences in ABA concentration were observed in xylem sap. N source had the strongest effect; however, nutrient limitation (particularly phosphorus limitation) and salt also had significant effects. ABA was found in greater concentration in phloem sap compared with xylem sap; however, the effect of treatment on ABA concentration in phloem was lower. In the leaves, ABA concentration was most variable compared with the other tissues. This variation was only affected by the N source. In roots, ABA was significantly decreased by nutrient limitation. Of the compartments in which ABA was quantified, xylem sap ABA concentration was most significantly correlated with leaf stomatal conductance and leaf growth. Additionally, ABA concentration in xylem was significantly correlated to that in phloem, indicating a 6-fold concentration increase from xylem to phloem. The ABA flow model showed that biosynthesis of ABA in roots affected the xylem flow of ABA. Moreover, ABA concentration in xylem affected the degradation of the phytohormone in shoots and also its export from shoots via phloem. The role of phloem transport is discussed since it stimulates ABA metabolism in roots. PMID:27440939

  4. ABA and cytokinins: challenge and opportunity for plant stress research.

    PubMed

    Verslues, Paul E

    2016-08-01

    Accumulation of the stress hormone abscisic acid (ABA) induces many cellular mechanisms associated with drought resistance. Recent years have seen a rapid advance in our knowledge of how increased ABA levels are perceived by ABA receptors, particularly the PYL/RCAR receptors, but there has been relatively less new information about how ABA accumulation is controlled and matched to stress severity. ABA synthesis and catabolism, conjugation and deconjugation to glucose, and ABA transport all are involved in controlling ABA levels. This highly buffered system of ABA metabolism represents both a challenge and opportunity in developing a mechanistic understanding of how plants detect and respond to drought. Recent data have also shown that direct manipulation of cytokinin levels in transgenic plants has dramatic effect on drought phenotypes and prompted new interest in the role of cytokinins and cytokinin signaling in drought. Both ABA and cytokinins will continue to be major foci of drought research but likely with different trajectories both in terms of basic research and in translational research aimed at increasing plant performance during drought. PMID:26910054

  5. Two potential Ca(2+)-mobilizing processes depend on the abscisic acid concentration and growth temperature in the Arabidopsis stomatal guard cell.

    PubMed

    Cousson, Alain

    2003-05-01

    The abscisic acid (ABA) stomatal closing signal might be transduced through different pathways, depending on the plant growth temperature (GT) and the applied ABA concentration. This was investigated in epidermal peels of Arabidopsis thaliana (L.) Columbia. Different Ca2+ buffers and guanosine-triphosphate-binding protein (G protein) modulators were tested on stomatal closing under light in response to 3 mumol/L ABA (ABA3 mu) and 30 mumol/L ABA (ABA30 mu) at the 15-17 degrees C and 23-25 degrees C GT ranges. The Ca2+ buffer, 1,2-bis(0-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, used as free acid (BAPTA) or acetoxymethyl ester (BAPTA-AM), similarly inhibited (up to approximately 70% inhibition) stomatal closing to ABA3 mu and ABA30 mu, whereas ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid specifically inhibited (up to approximately 70% inhibition) the ABA3 mu response at the 23-25 degrees C GT range. At the same GT range, the ABA3 mu response was specifically affected by the phospholipase C (PLC) inhibitor 1-[6-[[17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U73122). Moreover, the ABA30 mu response was specifically inhibited by the G protein antagonist pGlu-Gln-D-Trp-Phe-D-Trp-D-Trp-Met-NH2 (GP Ant-2) and by the inactive mastoparan analog, mas 17. The inhibitory effects of GP Ant-2 and mas 17 were additive. None of the tested pharmacological compounds were effective at the 15-17 degrees C GT range. Together, these results confirmed that, depending on GT and the exogenous ABA concentration, stomatal closing to ABA involves either one among two Ca2+ mobilizations or none of them.

  6. The unique mode of action of a divergent member of the ABA-receptor protein family in ABA and stress signaling

    PubMed Central

    Zhao, Yang; Chan, Zhulong; Xing, Lu; Liu, Xiaodong; Hou, Yueh-Ju; Chinnusamy, Viswanathan; Wang, Pengcheng; Duan, Chengguo; Zhu, Jian-Kang

    2013-01-01

    Proteins in the PYR/PYL/RCAR family (PYLs) are known as receptors for the phytohormone ABA. Upon ABA binding, PYL adopts a conformation that allows it to interact with and inhibit clade A protein phosphatase 2Cs (PP2Cs), which are known as the co-receptors for ABA. Inhibition of the PP2Cs then leads to the activation of the SnRK2 family protein kinases that phosphorylate and activate downstream effectors in ABA response pathways. The PYL family has 14 members in Arabidopsis, 13 of which have been demonstrated to function as ABA receptors. The function of PYL13, a divergent member of the family, has been enigmatic. We report here that PYL13 differs from the other PYLs in three key residues that affect ABA perception, and mutations in these three residues can convert PYL13 into a partially functional ABA receptor. Transgenic plants overexpressing PYL13 show increased ABA sensitivity in seed germination and postgermination seedling establishment as well as decreased stomatal conductance, increased water-use efficiency, accelerated stress-responsive gene expression, and enhanced drought resistance. pyl13 mutant plants are less sensitive to ABA inhibition of postgermination seedling establishment. PYL13 interacts with and inhibits some members of clade A PP2Cs (PP2CA in particular) in an ABA-independent manner. PYL13 also interacts with the other PYLs and antagonizes their function as ABA receptors. Our results show that PYL13 is not an ABA receptor but can modulate the ABA pathway by interacting with and inhibiting both the PYL receptors and the PP2C co-receptors. PMID:24189045

  7. Identification and Characterization of ABA-Responsive MicroRNAs in Rice.

    PubMed

    Tian, Caijuan; Zuo, Zhangli; Qiu, Jin-Long

    2015-07-20

    MicroRNAs (miRNAs) are endogenous non-coding small RNAs that silence genes through mRNA degradation or translational inhibition. The phytohormone abscisic acid (ABA) is essential for plant development and adaptation to abiotic and biotic stresses. In Arabidopsis, miRNAs are implicated in ABA functions. However, ABA-responsive miRNAs have not been systematically studied in rice. Here high throughput sequencing of small RNAs revealed that 107 miRNAs were differentially expressed in the rice ABA deficient mutant, Osaba1. Of these, 13 were confirmed by stem-loop RT-PCR. Among them, miR1425-5P, miR169a, miR169n, miR390-5P, miR397a and miR397b were up-regulated, but miR162b reduced in expression in Osaba1. The targets of these 13 miRNAs were predicted and validated by gene expression profiling. Interestingly, the expression levels of these miRNAs and their targets were regulated by ABA. Cleavage sites were detected on 7 of the miRNA targets by 5'-Rapid Amplification of cDNA Ends (5'-RACE). Finally, miR162b and its target OsTRE1 were shown to affect rice resistance to drought stress, suggesting that miR162b increases resistance to drought by targeting OsTRE1. Our work provides important information for further characterization and functional analysis of ABA-responsive miRNAs in rice. PMID:26233894

  8. Xanthophylls and abscisic acid biosynthesis in water-stressed bean leaves

    SciTech Connect

    Li, Y.; Walton, D.C.

    1987-12-01

    Experiments were designed to obtain evidence about the possible role of xanthophylls as abscisic acid (ABA) precursors in water-stressed leaves of Phaseolus vularis L. Leaves were exposed to /sup 14/CO/sub 2/ and the specific activities of several major leaf xanthophylls and stress-induced ABA were determined after a chase in /sup 12/CO/sub 2/ for varying periods of time. The ABA specific radioactivities were about 30 to 70% of that of lutein and violaxanthin regardless of the chase period. The specific activity of neoxanthin, however, was only about 15% of that of ABA. The effects of fluridone on xanthophyll and ABA levels and the extent of labeling of both from /sup 14/CO/sub 2/ were determined. Fluridone did not inhibit the accumulation of ABA when leaves were stressed once, although subsequent stresses in the presence of fluridone did lead to a reduced ABA accumulation. The incorporation of /sup 14/C from /sup 14/CO/sub 2/ into ABA and the xanthophylls was inhibited by fluridone and to about the same extent. The incorporation of /sup 18/O into ABA from violaxanthin which had been labeled in situ by means of the violaxanthin cycle was measured. The results indicated that a portion of the ABA accumulated during stress was formed from violaxanthin which had been labeled with /sup 18/O. The results of these experiments are consistent with a preformed xanthophyll(s) as the major ABA precursor in water-stressed bean leaves.

  9. 1-Aminocyclopropane-1-carboxylic acid and abscisic acid during the germination of sugar beet (Beta vulgaris L.): a comparative study of fruits and seeds.

    PubMed

    Hermann, Katrin; Meinhard, Juliane; Dobrev, Peter; Linkies, Ada; Pesek, Bedrich; Hess, Barbara; Machácková, Ivana; Fischer, Uwe; Leubner-Metzger, Gerhard

    2007-01-01

    The control of sugar beet (Beta vulgaris L.) germination by plant hormones was studied by comparing fruits and seeds. Treatment of sugar beet fruits and seeds with gibberellins, brassinosteroids, auxins, cytokinins, and jasmonates or corresponding hormone biosynthesis inhibitors did not appreciably affect radicle emergence of fruits or seeds. By contrast, treatment with ethylene or the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) promoted radicle emergence of fruits and seeds. Abscisic acid (ABA) acted as an antagonist of ethylene and inhibited radicle emergence of seeds, but not appreciably of fruits. High endogenous contents of ACC and of ABA were evident in seeds and pericarps of dry mature fruits, but declined early during imbibition. ABA-treatment of seeds and fruits induced seed ACC accumulation while ACC-treatment did not affect the seed ABA content. Transcripts of ACC oxidase (ACO, ethylene-forming enzyme) and ABA 8'-hydroxylase (CYP707A, ABA-degrading enzyme) accumulate in fruits and seeds upon imbibition. ABA and ACC and the pericarp did not affect the seed CYP707A transcript levels. By contrast, seed ACO transcript accumulation was promoted by ABA and by pericarp removal, but not by ACC. Quantification of the endogenous ABA and ACC contents, ABA and ACC leaching, and ethylene evolution, demonstrate that an embryo-mediated active ABA extrusion system is involved in keeping the endogenous seed ABA content low by 'active ABA leaching', while the pericarp restricts ACC leaching during imbibition. Sugar beet radicle emergence appears to be controlled by the pericarp, by ABA and ACC leaching, and by an ABA-ethylene antagonism that affects ACC biosynthesis and ACO gene expression.

  10. Copper suppresses abscisic acid catabolism and catalase activity, and inhibits seed germination of rice.

    PubMed

    Ye, Nenghui; Li, Haoxuan; Zhu, Guohui; Liu, Yinggao; Liu, Rui; Xu, Weifeng; Jing, Yu; Peng, Xinxiang; Zhang, Jianhua

    2014-11-01

    Although copper (Cu) is an essential micronutrient for plants, a slight excess of Cu in soil can be harmful to plants. Unfortunately, Cu contamination is a growing problem all over the world due to human activities, and poses a soil stress to plant development. As one of the most important biological processes, seed germination is sensitive to Cu stress. However, little is known about the mechanism of Cu-induced inhibition of seed germination. In the present study, we investigated the relationship between Cu and ABA which is the predominant regulator of seed germination. Cu at a concentration of 30 µM effectively inhibited germination of rice caryopsis. ABA content in germinating seeds under copper stress was also higher than that under control conditions. Quantitative real-time PCR (qRT-PCR) revealed that Cu treatment reduced the expression of OsABA8ox2, a key gene of ABA catabolism in rice seeds. In addition, both malondialdehyde (MDA) and H2O2 contents were increased by Cu stress in the germinating seeds. Antioxidant enzyme assays revealed that only catalase activity was reduced by excess Cu, which was consistent with the mRNA profile of OsCATa during seed germination under Cu stress. Together, our results demonstrate that suppression of ABA catabolism and catalase (CAT) activity by excess Cu leads to the inhibition of seed germination of rice.

  11. Structural basis and functions of abscisic acid receptors PYLs

    PubMed Central

    Zhang, Xing L.; Jiang, Lun; Xin, Qi; Liu, Yang; Tan, Jian X.; Chen, Zhong Z.

    2015-01-01

    Abscisic acid (ABA) plays a key role in many developmental processes and responses to adaptive stresses in plants. Recently, a new family of nucleocytoplasmic PYR/PYL/RCAR (PYLs) has been identified as bona fide ABA receptors. PYLs together with protein phosphatases type-2C (PP2Cs), Snf1 (Sucrose-non-fermentation 1)-related kinases subfamily 2 (SnRK2s) and downstream substrates constitute the core ABA signaling network. Generally, PP2Cs inactivate SnRK2s kinases by physical interaction and direct dephosphorylation. Upon ABA binding, PYLs change their conformations and then contact and inhibit PP2Cs, thus activating SnRK2s. Here, we reviewed the recent progress in research regarding the structures of the core signaling pathways of ABA, including the (+)-ABA, (−)-ABA and ABA analogs pyrabactin as well as 6AS perception by PYLs, SnRK2s mimicking PYLs in binding PP2Cs. PYLs inhibited PP2Cs in both the presence and absence of ABA and activated SnRK2s. The present review elucidates multiple ABA signal perception and transduction by PYLs, which might shed light on how to design small chemical compounds for improving plant performance in the future. PMID:25745428

  12. ABA-deficiency results in reduced plant and fruit size in tomato.

    PubMed

    Nitsch, L; Kohlen, W; Oplaat, C; Charnikhova, T; Cristescu, S; Michieli, P; Wolters-Arts, M; Bouwmeester, H; Mariani, C; Vriezen, W H; Rieu, I

    2012-06-15

    Abscisic acid (ABA) deficient mutants, such as notabilis and flacca, have helped elucidating the role of ABA during plant development and stress responses in tomato (Solanum lycopersicum L.). However, these mutants have only moderately decreased ABA levels. Here we report on plant and fruit development in the more strongly ABA-deficient notabilis/flacca (not/flc) double mutant. We observed that plant growth, leaf-surface area, drought-induced wilting and ABA-related gene expression in the different genotypes were strongly correlated with the ABA levels and thus most strongly affected in the not/flc double mutants. These mutants also had reduced fruit size that was caused by an overall smaller cell size. Lower ABA levels in fruits did not correlate with changes in auxin levels, but were accompanied by higher ethylene evolution rates. This suggests that in a wild-type background ABA stimulates cell enlargement during tomato fruit growth via a negative effect on ethylene synthesis.

  13. ABA says NO to UV-B: a universal response?

    PubMed

    Tossi, Vanesa; Cassia, Raul; Bruzzone, Santina; Zocchi, Elena; Lamattina, Lorenzo

    2012-09-01

    Abscisic acid (ABA) signaling pathways have been widely characterized in plants, whereas the function of ABA in animals is less well understood. However, recent advances show ABA production by a wide range of lower animals and higher mammals. This enables a new evaluation of ABA signaling pathways in different organisms in response to common environmental stress, such as ultraviolet (UV)-B. In this opinion article, we propose that the induction of common signaling components, such as ABA, nitric oxide (NO) and Ca(2+), in plant and animal cells in response to high doses of UV-B, suggests that the evolution of a general mechanism activated by UV-B is conserved in divergent multicellular organisms challenged by a changing common environment.

  14. AtRH57, a DEAD-box RNA helicase, is involved in feedback inhibition of glucose-mediated abscisic acid accumulation during seedling development and additively affects pre-ribosomal RNA processing with high glucose

    PubMed Central

    Hsu, Yi-Feng; Chen, Yun-Chu; Hsiao, Yu-Chun; Wang, Bing-Jyun; Lin, Shih-Yun; Cheng, Wan-Hsing; Jauh, Guang-Yuh; Harada, John J; Wang, Co-Shine

    2014-01-01

    The Arabidopsis thalianaT-DNA insertion mutant rh57-1 exhibited hypersensitivity to glucose (Glc) and abscisic acid (ABA). The other two rh57 mutants also showed Glc hypersensitivity similar to rh57-1, strongly suggesting that the Glc-hypersensitive feature of these mutants results from mutation of AtRH57. rh57-1 and rh57-3 displayed severely impaired seedling growth when grown in Glc concentrations higher than 3%. The gene, AtRH57 (At3g09720), was expressed in all Arabidopsis organs and its transcript was significantly induced by ABA, high Glc and salt. The new AtRH57 belongs to class II DEAD-box RNA helicase gene family. Transient expression of AtRH57-EGFP (enhanced green fluorescent protein) in onion cells indicated that AtRH57 was localized in the nucleus and nucleolus. Purified AtRH57-His protein was shown to unwind double-stranded RNA independent of ATP in vitro. The ABA biosynthesis inhibitor fluridone profoundly redeemed seedling growth arrest mediated by sugar. rh57-1 showed increased ABA levels when exposed to high Glc. Quantitative real time polymerase chain reaction analysis showed that AtRH57 acts in a signaling network downstream of HXK1. A feedback inhibition of ABA accumulation mediated by AtRH57 exists within the sugar-mediated ABA signaling. AtRH57 mutation and high Glc conditions additively caused a severe defect in small ribosomal subunit formation. The accumulation of abnormal pre-rRNA and resistance to protein synthesis-related antibiotics were observed in rh57 mutants and in the wild-type Col-0 under high Glc conditions. These results suggested that AtRH57 plays an important role in rRNA biogenesis in Arabidopsis and participates in response to sugar involving Glc- and ABA signaling during germination and seedling growth. PMID:24176057

  15. AtRH57, a DEAD-box RNA helicase, is involved in feedback inhibition of glucose-mediated abscisic acid accumulation during seedling development and additively affects pre-ribosomal RNA processing with high glucose.

    PubMed

    Hsu, Yi-Feng; Chen, Yun-Chu; Hsiao, Yu-Chun; Wang, Bing-Jyun; Lin, Shih-Yun; Cheng, Wan-Hsing; Jauh, Guang-Yuh; Harada, John J; Wang, Co-Shine

    2014-01-01

    The Arabidopsis thaliana T-DNA insertion mutant rh57-1 exhibited hypersensitivity to glucose (Glc) and abscisic acid (ABA). The other two rh57 mutants also showed Glc hypersensitivity similar to rh57-1, strongly suggesting that the Glc-hypersensitive feature of these mutants results from mutation of AtRH57. rh57-1 and rh57-3 displayed severely impaired seedling growth when grown in Glc concentrations higher than 3%. The gene, AtRH57 (At3g09720), was expressed in all Arabidopsis organs and its transcript was significantly induced by ABA, high Glc and salt. The new AtRH57 belongs to class II DEAD-box RNA helicase gene family. Transient expression of AtRH57-EGFP (enhanced green fluorescent protein) in onion cells indicated that AtRH57 was localized in the nucleus and nucleolus. Purified AtRH57-His protein was shown to unwind double-stranded RNA independent of ATP in vitro. The ABA biosynthesis inhibitor fluridone profoundly redeemed seedling growth arrest mediated by sugar. rh57-1 showed increased ABA levels when exposed to high Glc. Quantitative real time polymerase chain reaction analysis showed that AtRH57 acts in a signaling network downstream of HXK1. A feedback inhibition of ABA accumulation mediated by AtRH57 exists within the sugar-mediated ABA signaling. AtRH57 mutation and high Glc conditions additively caused a severe defect in small ribosomal subunit formation. The accumulation of abnormal pre-rRNA and resistance to protein synthesis-related antibiotics were observed in rh57 mutants and in the wild-type Col-0 under high Glc conditions. These results suggested that AtRH57 plays an important role in rRNA biogenesis in Arabidopsis and participates in response to sugar involving Glc- and ABA signaling during germination and seedling growth.

  16. AtRH57, a DEAD-box RNA helicase, is involved in feedback inhibition of glucose-mediated abscisic acid accumulation during seedling development and additively affects pre-ribosomal RNA processing with high glucose.

    PubMed

    Hsu, Yi-Feng; Chen, Yun-Chu; Hsiao, Yu-Chun; Wang, Bing-Jyun; Lin, Shih-Yun; Cheng, Wan-Hsing; Jauh, Guang-Yuh; Harada, John J; Wang, Co-Shine

    2014-01-01

    The Arabidopsis thaliana T-DNA insertion mutant rh57-1 exhibited hypersensitivity to glucose (Glc) and abscisic acid (ABA). The other two rh57 mutants also showed Glc hypersensitivity similar to rh57-1, strongly suggesting that the Glc-hypersensitive feature of these mutants results from mutation of AtRH57. rh57-1 and rh57-3 displayed severely impaired seedling growth when grown in Glc concentrations higher than 3%. The gene, AtRH57 (At3g09720), was expressed in all Arabidopsis organs and its transcript was significantly induced by ABA, high Glc and salt. The new AtRH57 belongs to class II DEAD-box RNA helicase gene family. Transient expression of AtRH57-EGFP (enhanced green fluorescent protein) in onion cells indicated that AtRH57 was localized in the nucleus and nucleolus. Purified AtRH57-His protein was shown to unwind double-stranded RNA independent of ATP in vitro. The ABA biosynthesis inhibitor fluridone profoundly redeemed seedling growth arrest mediated by sugar. rh57-1 showed increased ABA levels when exposed to high Glc. Quantitative real time polymerase chain reaction analysis showed that AtRH57 acts in a signaling network downstream of HXK1. A feedback inhibition of ABA accumulation mediated by AtRH57 exists within the sugar-mediated ABA signaling. AtRH57 mutation and high Glc conditions additively caused a severe defect in small ribosomal subunit formation. The accumulation of abnormal pre-rRNA and resistance to protein synthesis-related antibiotics were observed in rh57 mutants and in the wild-type Col-0 under high Glc conditions. These results suggested that AtRH57 plays an important role in rRNA biogenesis in Arabidopsis and participates in response to sugar involving Glc- and ABA signaling during germination and seedling growth. PMID:24176057

  17. Crucial Roles of Abscisic Acid Biogenesis in Virulence of Rice Blast Fungus Magnaporthe oryzae

    PubMed Central

    Spence, Carla A.; Lakshmanan, Venkatachalam; Donofrio, Nicole; Bais, Harsh P.

    2015-01-01

    Rice suffers dramatic yield losses due to blast pathogen Magnaporthe oryzae. Pseudomonas chlororaphis EA105, a bacterium that was isolated from the rice rhizosphere, inhibits M. oryzae. It was shown previously that pre-treatment of rice with EA105 reduced the size of blast lesions through jasmonic acid (JA)- and ethylene (ETH)-mediated ISR. Abscisic acid (ABA) acts antagonistically toward salicylic acid (SA), JA, and ETH signaling, to impede plant defense responses. EA105 may be reducing the virulence of M. oryzae by preventing the pathogen from up-regulating the key ABA biosynthetic gene NCED3 in rice roots, as well as a β-glucosidase likely involved in activating conjugated inactive forms of ABA. However, changes in total ABA concentrations were not apparent, provoking the question of whether ABA concentration is an indicator of ABA signaling and response. In the rice-M. oryzae interaction, ABA plays a dual role in disease severity by increasing plant susceptibility and accelerating pathogenesis in the fungus itself. ABA is biosynthesized by M. oryzae. Further, exogenous ABA increased spore germination and appressoria formation, distinct from other plant growth regulators. EA105, which inhibits appressoria formation, counteracted the virulence-promoting effects of ABA on M. oryzae. The role of endogenous fungal ABA in blast disease was confirmed through the inability of a knockout mutant impaired in ABA biosynthesis to form lesions on rice. Therefore, it appears that EA105 is invoking multiple strategies in its protection of rice from blast including direct mechanisms as well as those mediated through plant signaling. ABA is a molecule that is likely implicated in both tactics. PMID:26648962

  18. Reduced ABA Accumulation in the Root System is Caused by ABA Exudation in Upland Rice (Oryza sativa L. var. Gaoshan1) and this Enhanced Drought Adaptation.

    PubMed

    Shi, Lu; Guo, Miaomiao; Ye, Nenghui; Liu, Yinggao; Liu, Rui; Xia, Yiji; Cui, Suxia; Zhang, Jianhua

    2015-05-01

    Lowland rice (Nipponbare) and upland rice (Gaoshan 1) that are comparable under normal and moderate drought conditions showed dramatic differences in severe drought conditions, both naturally occurring long-term drought and simulated rapid water deficits. We focused on their root response and found that enhanced tolerance of upland rice to severe drought conditions was mainly due to the lower level of ABA in its roots than in those of the lowland rice. We first excluded the effect of ABA biosynthesis and catabolism on root-accumulated ABA levels in both types of rice by monitoring the expression of four OsNCED genes and two OsABA8ox genes. Next, we excluded the impact of the aerial parts on roots by suppressing leaf-biosynthesized ABA with fluridone and NDGA (nordihydroguaiaretic acid), and measuring the ABA level in detached roots. Instead, we proved that upland rice had the ability to export considerably more root-sourced ABA than lowland rice under severe drought, which improved ABA-dependent drought adaptation. The investigation of apoplastic pH in root cells and root anatomy showed that ABA leakage in the root system of upland rice was related to high apoplastic pH and the absence of Casparian bands in the sclerenchyma layer. Finally, taking some genes as examples, we predicted that different ABA levels in rice roots stimulated distinct ABA perception and signaling cascades, which influenced its response to water stress.

  19. ABA signaling in stomatal guard cells: lessons from Commelina and Vicia.

    PubMed

    Mori, Izumi C; Murata, Yoshiyuki

    2011-07-01

    Abscisic acid (ABA) signaling mechanisms have been studied in a broad variety of plant species using complementary analyses, taking advantage of different methodologies suitable for each plant species. Early studies on ABA biosynthesis using Solanum lycopersicum mutants suggested an importance of ABA synthesis in stomatal closure. To understand ABA signaling in guard cells, cellular, biochemical and electrophysiological studies in Vicia faba and Commelina communis have been conducted, providing fundamental knowledge that was further reconfirmed by molecular genetic studies of Arabidopsis. In this article, examples of stomatal studies in several plants and prospects in ABA research are discussed.

  20. Multiple impacts of the plant growth-promoting rhizobacterium Variovorax paradoxus 5C-2 on nutrient and ABA relations of Pisum sativum

    PubMed Central

    Dodd, Ian C.

    2012-01-01

    Resolving the physiological mechanisms by which rhizobacteria enhance plant growth is difficult, since many such bacteria contain multiple plant growth-promoting properties. To understand further how the 1-aminocyclopropane-1-carboxylate (ACC) deaminase (ACCd)-containing rhizobacterium Variovorax paradoxus 5C-2 affects plant growth, the flows and partitioning of mineral nutrients and abscisic acid (ABA) and ABA metabolism were studied in pea (Pisum sativum) plants following rhizosphere bacterial inoculation. Although root architecture was not affected, inoculation increased root and shoot biomass, and stomatal conductance, by 20, 15, and 24%, respectively, and increased N, P, K, Ca, and Mg uptake by 16, 81, 50, 46, and 58%, respectively. P deposition in inoculated plant roots was 4.9 times higher than that in uninoculated controls. Rhizobacterial inoculation increased root to shoot xylem flows and shoot to root phloem flows of K by 1.8- and 2.1-fold, respectively. In control plants, major sinks for K deposition were the roots and upper shoot (43% and 49% of total uptake, respectively), while rhizobacterial inoculation increased K distribution to the lower shoot at the expense of other compartments (xylem, phloem, and upper shoot). Despite being unable to metabolize ABA in vitro, V. paradoxus 5C-2 decreased root ABA concentrations and accumulation by 40–60%. Although inoculation decreased xylem ABA flows, phloem ABA flows increased. Whether bacterial ACCd attenuates root to shoot ABA signalling requires further investigation, since ABA is critical to maintain growth of droughted plants, and ACCd-containing organisms have been advocated as a means of minimizing growth inhibition of plants in drying soil. PMID:23136167

  1. Evolution of Abscisic Acid Synthesis and Signaling Mechanisms

    PubMed Central

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

    2011-01-01

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

  2. Cell-free conversion of 1 prime -deoxy- sup 2 H-ABA to sup 2 H-ABA in extracts from Cercospora rosicola

    SciTech Connect

    Al-Nimri, L.; Coolbaugh, R.C. )

    1990-05-01

    The characteristics of the enzyme converting 1{prime}-deoxy-ABA into ABA have been studied in the fungus C. rosicola. Enzyme extracts were prepared from cold-pressed mycelia of C. rosicola. The suspension was a high speed supernatant and a microsomal fraction. A cell-free system was developed to convert 1{prime}-deoxy-{sup 2}H-ABA into {sup 2}H-ABA using a reaction mixture containing 300 {mu}l enzyme extract, 10 {mu}m 1{prime}-deoxy-{sup 2}H-ABA. The reaction products were chromatographed by reverse phase HPLC. The presumptive ABA fractions were collected and {sup 2}H-ABA was quantified by GC-MS using a {sup 2}H-(2Z, 4E)-ABA standard curve. 1{prime}-deoxy-{sup 2}H-ABA was converted to an average of 1.47 pmole {sup 2}H-ABA/mg protein per min. Most of the enzymic activity was found in the microsomal fraction. The reaction required NADPH and was enhanced by FAD. The reaction was not inhibited by triarimol.

  3. The ABI4-induced Arabidopsis ANAC060 transcription factor attenuates ABA signaling and renders seedlings sugar insensitive when present in the nucleus.

    PubMed

    Li, Ping; Zhou, Hua; Shi, Xiaoliang; Yu, Bo; Zhou, Yan; Chen, Suli; Wang, Yufeng; Peng, Yu; Meyer, Rhonda C; Smeekens, Sjef C; Teng, Sheng

    2014-03-01

    Seedling establishment is inhibited on media containing high levels (∼ 6%) of glucose or fructose. Genetic loci that overcome the inhibition of seedling growth on high sugar have been identified using natural variation analysis and mutant selection, providing insight into sugar signaling pathways. In this study, a quantitative trait locus (QTL) analysis was performed for seedling sensitivity to high sugar in a Col/C24 F2 population of Arabidopsis thaliana. A glucose and fructose-sensing QTL, GSQ11, was mapped through selective genotyping and confirmed in near-isogenic lines in both Col and C24 backgrounds. Allelism tests and transgenic complementation showed that GSQ11 lies within the ANAC060 gene. The Col ANAC060 allele confers sugar insensitivity and was dominant over the sugar-sensitive C24 allele. Genomic and mRNA analyses showed that a single-nucleotide polymorphism (SNP) in Col ANAC060 affects the splicing patterns of ANAC060 such that 20 additional nucleotides are present in the mRNA. The insertion created a stop codon, resulting in a truncated ANAC60 protein lacking the transmembrane domain (TMD) that is present in the C24 ANAC060 protein. The absence of the TMD results in the nuclear localization of ANAC060. The short version of the ANAC060 protein is found in ∼ 12% of natural Arabidopsis accessions. Glucose induces GSQ11/ANAC060 expression in a process that requires abscisic acid (ABA) signaling. Chromatin immunoprecipitation-qPCR and transient expression analysis showed that ABI4 directly binds to the GSQ11/ANAC060 promoter to activate transcription. Interestingly, Col ANAC060 reduced ABA sensitivity and Glc-induced ABA accumulation, and ABI4 expression was also reduced in Col ANAC060 lines. Thus, the sugar-ABA signaling cascade induces ANAC060 expression, but the truncated Col ANAC060 protein attenuates ABA induction and ABA signaling. This negative feedback from nuclear ANAC060 on ABA signaling results in sugar insensitivity.

  4. Ethylene-dependent/ethylene-independent ABA regulation of tomato plants colonized by arbuscular mycorrhiza fungi.

    PubMed

    Martín-Rodríguez, José Ángel; León-Morcillo, Rafael; Vierheilig, Horst; Ocampo, Juan Antonio; Ludwig-Müller, Jutta; García-Garrido, José Manuel

    2011-04-01

    We investigated the relationship between ABA and ethylene regulating the formation of the arbuscular mycorrhiza (AM) symbiosis in tomato (Solanum lycopersicum) plants and tried to define the specific roles played by each of these phytohormones in the mycorrhization process. We analysed the impact of ABA biosynthesis inhibition on mycorrhization by Glomus intraradices in transgenic tomato plants with an altered ethylene pathway. We also studied the effects on mycorrhization in sitiens plants treated with the aminoethoxyvinyl glycine hydrochloride (AVG) ethylene biosynthesis inhibitor and supplemented with ABA. In addition, the expression of plant and fungal genes involved in the mycorrhization process was studied. ABA biosynthesis inhibition qualitatively altered the parameters of mycorrhization in accordance with the plant's ethylene perception and ethylene biosynthesis abilities. Inhibition of ABA biosynthesis in wild-type plants negatively affected all the mycorrhization parameters studied, while tomato mutants impaired in ethylene synthesis only showed a reduced arbuscular abundance in mycorrhizal roots. Inhibition of ethylene synthesis in ABA-deficient sitiens plants increased the intensity of mycorrhiza development, while ABA application rescued arbuscule abundance in the root's mycorrhizal zones. The results of our study show an antagonistic interaction between ABA and ethylene, and different roles of each of the two hormones during AM formation. This suggests that a dual ethylene-dependent/ethylene-independent mechanism is involved in ABA regulation of AM formation.

  5. Novel Bioactivity of Ellagic Acid in Inhibiting Human Platelet Activation

    PubMed Central

    Chang, Yi; Chen, Wei-Fan; Lin, Kuan-Hung; Hsieh, Cheng-Ying; Chou, Duen-Suey; Lin, Li-Jyun; Sheu, Joen-Rong; Chang, Chao-Chien

    2013-01-01

    Pomegranates are widely consumed either as fresh fruit or in beverage form as juice and wine. Ellagic acid possesses potent antioxidative properties; it is known to be an effective phytotherapeutic agent with antimutagenic and anticarcinogenic qualities. Ellagic acid (20 to 80 μM) exhibited a potent activity in inhibiting platelet aggregation stimulated by collagen; however, it did not inhibit platelet aggregation stimulated by thrombin, arachidonic acid, or U46619. Treatment with ellagic acid (50 and 80 μM) significantly inhibited platelet activation stimulated by collagen; this alteration was accompanied by the inhibition of relative [Ca2+]i mobilization, and the phosphorylation of phospholipase C (PLC)γ2, protein kinase C (PKC), mitogen-activated protein kinases (MAPKs), and Akt, as well as hydroxyl radical (OH●) formation. In addition, ellagic acid also inhibited p38 MAPK and Akt phosphorylation stimulated by hydrogen peroxide. By contrast, ellagic acid did not significantly affect PKC activation and platelet aggregation stimulated by PDBu. This study is the first to show that, in addition to being considered a possible agent for preventing tumor growth, ellagic acid possesses potent antiplatelet properties. It appears to initially inhibit the PLCγ2-PKC cascade and/or hydroxyl radical formation, followed by decreased phosphorylation of MAPKs and Akt, ultimately inhibiting platelet aggregation. PMID:23533502

  6. Distinct abscisic acid signaling pathways for modulation of guard cell versus mesophyll cell potassium channels revealed by expression studies in Xenopus laevis oocytes

    NASA Technical Reports Server (NTRS)

    Sutton, F.; Paul, S. S.; Wang, X. Q.; Assmann, S. M.; Evans, M. L. (Principal Investigator)

    2000-01-01

    Regulation of guard cell ion transport by abscisic acid (ABA) and in particular ABA inhibition of a guard cell inward K(+) current (I(Kin)) is well documented. However, little is known concerning ABA effects on ion transport in other plant cell types. Here we applied patch clamp techniques to mesophyll cell protoplasts of fava bean (Vicia faba cv Long Pod) plants and demonstrated ABA inhibition of an outward K(+) current (I(Kout)). When mesophyll cell protoplast mRNA (mesophyll mRNA) was expressed in Xenopus laevis oocytes, I(Kout) was generated that displayed similar properties to I(Kout) observed from direct analysis of mesophyll cell protoplasts. I(Kout) expressed by mesophyll mRNA-injected oocytes was inhibited by ABA, indicating that the ABA signal transduction pathway observed in mesophyll cells was preserved in the frog oocytes. Co-injection of oocytes with guard cell protoplast mRNA and cRNA for KAT1, an inward K(+) channel expressed in guard cells, resulted in I(Kin) that was similarly inhibited by ABA. However, oocytes co-injected with mesophyll mRNA and KAT1 cRNA produced I(Kin) that was not inhibited by ABA. These results demonstrate that the mesophyll-encoded signaling mechanism could not substitute for the guard cell pathway. These findings indicate that mesophyll cells and guard cells use distinct and different receptor types and/or signal transduction pathways in ABA regulation of K(+) channels.

  7. Distinct abscisic acid signaling pathways for modulation of guard cell versus mesophyll cell potassium channels revealed by expression studies in Xenopus laevis oocytes.

    PubMed

    Sutton, F; Paul, S S; Wang, X Q; Assmann, S M

    2000-09-01

    Regulation of guard cell ion transport by abscisic acid (ABA) and in particular ABA inhibition of a guard cell inward K(+) current (I(Kin)) is well documented. However, little is known concerning ABA effects on ion transport in other plant cell types. Here we applied patch clamp techniques to mesophyll cell protoplasts of fava bean (Vicia faba cv Long Pod) plants and demonstrated ABA inhibition of an outward K(+) current (I(Kout)). When mesophyll cell protoplast mRNA (mesophyll mRNA) was expressed in Xenopus laevis oocytes, I(Kout) was generated that displayed similar properties to I(Kout) observed from direct analysis of mesophyll cell protoplasts. I(Kout) expressed by mesophyll mRNA-injected oocytes was inhibited by ABA, indicating that the ABA signal transduction pathway observed in mesophyll cells was preserved in the frog oocytes. Co-injection of oocytes with guard cell protoplast mRNA and cRNA for KAT1, an inward K(+) channel expressed in guard cells, resulted in I(Kin) that was similarly inhibited by ABA. However, oocytes co-injected with mesophyll mRNA and KAT1 cRNA produced I(Kin) that was not inhibited by ABA. These results demonstrate that the mesophyll-encoded signaling mechanism could not substitute for the guard cell pathway. These findings indicate that mesophyll cells and guard cells use distinct and different receptor types and/or signal transduction pathways in ABA regulation of K(+) channels. PMID:10982437

  8. Inhibition of Influenza Virus Ribonucleic Acid Polymerase by Ribavirin Triphosphate

    PubMed Central

    Eriksson, Bertil; Helgstrand, Erik; Johansson, Nils Gunnar; Larsson, Alf; Misiorny, Alfons; Noren, Jan Olof; Philipson, Lennart; Stenberg, Kjell; Stening, Goran; Stridh, Stig; Öberg, Bo

    1977-01-01

    Ribavirin 5′-triphosphate (RTP), derived from the broad-spectrum antiviral compound ribavirin (Virazole), can selectively inhibit influenza virus ribonucleic acid polymerase in a cell-free assay. Ribavirin and its 5′-monophosphate have no effect on the polymerase. The inhibition is competitive with respect to adenosine 5′-triphosphate and guanosine 5′-triphosphate. RTP also inhibits ApG- and GpC-stimulated influenza virus ribonucleic acid polymerase. Since ribavirin is phosphorylated in the cell, the inhibition of influenza multiplication in the cell may also be caused by RTP. PMID:879760

  9. ABA receptor PYL9 promotes drought resistance and leaf senescence.

    PubMed

    Zhao, Yang; Chan, Zhulong; Gao, Jinghui; Xing, Lu; Cao, Minjie; Yu, Chunmei; Hu, Yuanlei; You, Jun; Shi, Haitao; Zhu, Yingfang; Gong, Yuehua; Mu, Zixin; Wang, Haiqing; Deng, Xin; Wang, Pengcheng; Bressan, Ray A; Zhu, Jian-Kang

    2016-02-16

    Drought stress is an important environmental factor limiting plant productivity. In this study, we screened drought-resistant transgenic plants from 65 promoter-pyrabactin resistance 1-like (PYL) abscisic acid (ABA) receptor gene combinations and discovered that pRD29A::PYL9 transgenic lines showed dramatically increased drought resistance and drought-induced leaf senescence in both Arabidopsis and rice. Previous studies suggested that ABA promotes senescence by causing ethylene production. However, we found that ABA promotes leaf senescence in an ethylene-independent manner by activating sucrose nonfermenting 1-related protein kinase 2s (SnRK2s), which subsequently phosphorylate ABA-responsive element-binding factors (ABFs) and Related to ABA-Insensitive 3/VP1 (RAV1) transcription factors. The phosphorylated ABFs and RAV1 up-regulate the expression of senescence-associated genes, partly by up-regulating the expression of Oresara 1. The pyl9 and ABA-insensitive 1-1 single mutants, pyl8-1pyl9 double mutant, and snrk2.2/3/6 triple mutant showed reduced ABA-induced leaf senescence relative to the WT, whereas pRD29A::PYL9 transgenic plants showed enhanced ABA-induced leaf senescence. We found that leaf senescence may benefit drought resistance by helping to generate an osmotic potential gradient, which is increased in pRD29A::PYL9 transgenic plants and causes water to preferentially flow to developing tissues. Our results uncover the molecular mechanism of ABA-induced leaf senescence and suggest an important role of PYL9 and leaf senescence in promoting resistance to extreme drought stress. PMID:26831097

  10. ABA receptor PYL9 promotes drought resistance and leaf senescence

    PubMed Central

    Zhao, Yang; Chan, Zhulong; Gao, Jinghui; Xing, Lu; Cao, Minjie; Yu, Chunmei; Hu, Yuanlei; You, Jun; Shi, Haitao; Zhu, Yingfang; Gong, Yuehua; Mu, Zixin; Wang, Haiqing; Deng, Xin; Wang, Pengcheng; Bressan, Ray A.; Zhu, Jian-Kang

    2016-01-01

    Drought stress is an important environmental factor limiting plant productivity. In this study, we screened drought-resistant transgenic plants from 65 promoter-pyrabactin resistance 1-like (PYL) abscisic acid (ABA) receptor gene combinations and discovered that pRD29A::PYL9 transgenic lines showed dramatically increased drought resistance and drought-induced leaf senescence in both Arabidopsis and rice. Previous studies suggested that ABA promotes senescence by causing ethylene production. However, we found that ABA promotes leaf senescence in an ethylene-independent manner by activating sucrose nonfermenting 1-related protein kinase 2s (SnRK2s), which subsequently phosphorylate ABA-responsive element-binding factors (ABFs) and Related to ABA-Insensitive 3/VP1 (RAV1) transcription factors. The phosphorylated ABFs and RAV1 up-regulate the expression of senescence-associated genes, partly by up-regulating the expression of Oresara 1. The pyl9 and ABA-insensitive 1-1 single mutants, pyl8-1pyl9 double mutant, and snrk2.2/3/6 triple mutant showed reduced ABA-induced leaf senescence relative to the WT, whereas pRD29A::PYL9 transgenic plants showed enhanced ABA-induced leaf senescence. We found that leaf senescence may benefit drought resistance by helping to generate an osmotic potential gradient, which is increased in pRD29A::PYL9 transgenic plants and causes water to preferentially flow to developing tissues. Our results uncover the molecular mechanism of ABA-induced leaf senescence and suggest an important role of PYL9 and leaf senescence in promoting resistance to extreme drought stress. PMID:26831097

  11. ABA receptor PYL9 promotes drought resistance and leaf senescence.

    PubMed

    Zhao, Yang; Chan, Zhulong; Gao, Jinghui; Xing, Lu; Cao, Minjie; Yu, Chunmei; Hu, Yuanlei; You, Jun; Shi, Haitao; Zhu, Yingfang; Gong, Yuehua; Mu, Zixin; Wang, Haiqing; Deng, Xin; Wang, Pengcheng; Bressan, Ray A; Zhu, Jian-Kang

    2016-02-16

    Drought stress is an important environmental factor limiting plant productivity. In this study, we screened drought-resistant transgenic plants from 65 promoter-pyrabactin resistance 1-like (PYL) abscisic acid (ABA) receptor gene combinations and discovered that pRD29A::PYL9 transgenic lines showed dramatically increased drought resistance and drought-induced leaf senescence in both Arabidopsis and rice. Previous studies suggested that ABA promotes senescence by causing ethylene production. However, we found that ABA promotes leaf senescence in an ethylene-independent manner by activating sucrose nonfermenting 1-related protein kinase 2s (SnRK2s), which subsequently phosphorylate ABA-responsive element-binding factors (ABFs) and Related to ABA-Insensitive 3/VP1 (RAV1) transcription factors. The phosphorylated ABFs and RAV1 up-regulate the expression of senescence-associated genes, partly by up-regulating the expression of Oresara 1. The pyl9 and ABA-insensitive 1-1 single mutants, pyl8-1pyl9 double mutant, and snrk2.2/3/6 triple mutant showed reduced ABA-induced leaf senescence relative to the WT, whereas pRD29A::PYL9 transgenic plants showed enhanced ABA-induced leaf senescence. We found that leaf senescence may benefit drought resistance by helping to generate an osmotic potential gradient, which is increased in pRD29A::PYL9 transgenic plants and causes water to preferentially flow to developing tissues. Our results uncover the molecular mechanism of ABA-induced leaf senescence and suggest an important role of PYL9 and leaf senescence in promoting resistance to extreme drought stress.

  12. Abscisic Acid Levels and Seed Dormancy

    PubMed Central

    Sondheimer, E.; Tzou, D. S.; Galson, Eva C.

    1968-01-01

    Dormant seeds from Fraxinus species require cold-temperature after-ripening prior to germination. Earlier, we found that abscisic acid (ABA) will inhibit germination of excised nondormant embryos and that this can be reversed with a combination of gibberellic acid and kinetin. Using Milborrow's quantitative “racemate dilution” method the ABA concentration in 3 types of Fraxinus seed and pericarp were determined. While ABA was present in all tissues, the highest concentration was found in the seed and pericarp of dormant F. americana. During the chilling treatment of F. americana the ABA levels decreased 37% in the pericarp and 68% in the seed. The ABA concentration of the seed of the nondormant species, F. ornus, is as low as that found in F. americana seeds after cold treatment. Experiments with exogenously added ABA solutions indicate that it is unlikely that the ABA in the pericarp functions in the regulation of seed dormancy. However, the ABA in the seed does seem to have a regulatory role in germination. Images PMID:16656935

  13. Function of ABA in Stomatal Defense against Biotic and Drought Stresses.

    PubMed

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

    2015-01-01

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

  14. Arabidopsis PYL8 Plays an Important Role for ABA Signaling and Drought Stress Responses.

    PubMed

    Lim, Chae Woo; Baek, Woonhee; Han, Sang-Wook; Lee, Sung Chul

    2013-12-01

    Plants are frequently exposed to numerous environmental stresses such as dehydration and high salinity, and have developed elaborate mechanisms to counteract the deleterious effects of stress. The phytohormone abscisic acid (ABA) plays a critical role as an integrator of plant responses to water-limited condition to activate ABA signal transduction pathway. Although perception of ABA has been suggested to be important, the function of each ABA receptor remains elusive in dehydration condition. Here, we show that ABA receptor, pyrabactin resistance-like protein 8 (PYL8), functions in dehydration conditions. Transgenic plants overexpressing PYL8 exhibited hypersensitive phenotype to ABA in seed germination, seedling growth and establishment. We found that hypersensitivity to ABA of transgenic plants results in high degrees of stomatal closure in response to ABA leading to low transpiration rates and ultimately more vulnerable to drought than the wild-type plants. In addition, high expression of ABA maker genes also contributes to altered drought tolerance phenotype. Overall, this work emphasizes the importance of ABA signaling by ABA receptor in stomata during defense response to drought stress. PMID:25288979

  15. Function of ABA in Stomatal Defense against Biotic and Drought Stresses

    PubMed Central

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

    2015-01-01

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

  16. A link between magnesium-chelatase H subunit and sucrose nonfermenting 1 (SNF1)-related protein kinase SnRK2.6/OST1 in Arabidopsis guard cell signalling in response to abscisic acid.

    PubMed

    Liang, Shan; Lu, Kai; Wu, Zhen; Jiang, Shang-Chuan; Yu, Yong-Tao; Bi, Chao; Xin, Qi; Wang, Xiao-Fang; Zhang, Da-Peng

    2015-10-01

    Magnesium-chelatase H subunit [CHLH/putative abscisic acid (ABA) receptor ABAR] positively regulates guard cell signalling in response to ABA, but the molecular mechanism remains largely unknown. A member of the sucrose nonfermenting 1 (SNF1)-related protein kinase 2 family, SnRK2.6/open stomata 1 (OST1)/SRK2E, which plays a critical role in ABA signalling in Arabidopsis guard cells, interacts with ABAR/CHLH. Neither mutation nor over-expression of the ABAR gene affects significantly ABA-insensitive phenotypes of stomatal movement in the OST1 knockout mutant allele srk2e. However, OST1 over-expression suppresses ABA-insensitive phenotypes of the ABAR mutant allele cch in stomatal movement. These genetic data support that OST1 functions downstream of ABAR in ABA signalling in guard cells. Consistent with this, ABAR protein is phosphorylated, but independently of the OST1 protein kinase. Two ABAR mutant alleles, cch and rtl1, show ABA insensitivity in ABA-induced reactive oxygen species and nitric oxide production, as well as in ABA-activated phosphorylation of a K(+) inward channel KAT1 in guard cells, which is consistent with that observed in the pyr1 pyl1 pyl2 pyl4 quadruple mutant of the well-characterized ABA receptor PYR/PYL/RCAR family acting upstream of OST1. These findings suggest that ABAR shares, at least in part, downstream signalling components with PYR/PYL/RCAR receptors for ABA in guard cells; though cch and rtl1 show strong ABA-insensitive phenotypes in both ABA-induced stomatal closure and inhibition of stomatal opening, while the pyr1 pyl1 pyl2 pyl4 quadruple mutant shows strong ABA insensitivity only in ABA-induced stomatal closure. These data establish a link between ABAR/CHLH and SnRK2.6/OST1 in guard cell signalling in response to ABA.

  17. Postharvest Exogenous Application of Abscisic Acid Reduces Internal Browning in Pineapple.

    PubMed

    Zhang, Qin; Liu, Yulong; He, Congcong; Zhu, Shijiang

    2015-06-10

    Internal browning (IB) is a postharvest physiological disorder causing economic losses in pineapple, but there is no effective control measure. In this study, postharvest application of 380 μM abscisic acid (ABA) reduced IB incidence by 23.4-86.3% and maintained quality in pineapple fruit. ABA reduced phenolic contents and polyphenol oxidase and phenylalanine ammonia lyase activities; increased catalase and peroxidase activities; and decreased O2(·-), H2O2, and malondialdehyde levels. This suggests ABA could control IB through inhibiting phenolics biosynthesis and oxidation and enhancing antioxidant capability. Furthermore, the efficacy of IB control by ABA was not obviously affected by tungstate, ABA biosynthesis inhibitor, nor by diphenylene iodonium, NADPH oxidase inhibitor, nor by lanthanum chloride, calcium channel blocker, suggesting that ABA is sufficient for controlling IB. This process might not involve H2O2 generation, but could involve the Ca(2+) channels activation. These results provide potential for developing effective measures for controlling IB in pineapple.

  18. R-lipoic acid inhibits mammalian pyruvate dehydrogenase kinase.

    PubMed

    Korotchkina, Lioubov G; Sidhu, Sukhdeep; Patel, Mulchand S

    2004-10-01

    The four pyruvate dehydrogenase kinase (PDK) and two pyruvate dehydrogenase phosphatase (PDP) isoenzymes that are present in mammalian tissues regulate activity of the pyruvate dehydrogenase complex (PDC) by phosphorylation/dephosphorylation of its pyruvate dehydrogenase (E1) component. The effect of lipoic acids on the activity of PDKs and PDPs was investigated in purified proteins system. R-lipoic acid, S-lipoic acid and R-dihydrolipoic acid did not significantly affect activities of PDPs and at the same time inhibited PDKs to different extents (PDK1>PDK4 approximately PDK2>PDK3 for R-LA). Since lipoic acids inhibited PDKs activity both when reconstituted in PDC and in the presence of E1 alone, dissociation of PDK from the lipoyl domains of dihydrolipoamide acetyltransferase in the presence of lipoic acids is not a likely explanation for inhibition. The activity of PDK1 towards phosphorylation sites 1, 2 and 3 of E1 was decreased to the same extent in the presence of R-lipoic acid, thus excluding protection of the E1 active site by lipoic acid from phosphorylation. R-lipoic acid inhibited autophosphorylation of PDK2 indicating that it exerted its effect on PDKs directly. Inhibition of PDK1 by R-lipoic acid was not altered by ADP but was decreased in the presence of pyruvate which itself inhibits PDKs. An inhibitory effect of lipoic acid on PDKs would result in less phosphorylation of E1 and hence increased PDC activity. This finding provides a possible mechanism for a glucose (and lactate) lowering effect of R-lipoic acid in diabetic subjects. PMID:15512796

  19. Synthesis and bioactivity of 2',3'-benzoabscisic acid analogs.

    PubMed

    Han, Xiaoqiang; Wan, Chuan; Li, Xiuyun; Li, Hong; Yang, Dongyan; Du, Shijie; Xiao, Yumei; Qin, Zhaohai

    2015-06-01

    2',3'-Benzoabscisic acid 4a is significantly more active than (±)-ABA and can be potentially used as a plant growth regulator for agriculture. In this study, six 4a analogs were designed and synthesized. Bioassay showed that 4a displayed greater activity than (±)-ABA and the six analogs produced less inhibition than 4a itself. Specially, some analogs displayed markedly different activities to different physiological and biochemical process, which were largely different from ABA and 4a. Compared to (±)-ABA, 4b and 4c were more effective germination inhibitors for lettuce, but less effective inhibitors for rice elongation. Five-membered analog 5 was higher or slightly weaker in inhibiting Arabidopsis seed germination and rice elongation, respectively, but at least 10 times less effective than (±)-ABA in lettuce seed germination. Dual acid 6 and alkyne acid 20 nearly produced no inhibitory activity for Arabidopsis seed germination, but displayed excellent activity in inhibiting rice seedling growth. The preference of the analogs to different physiology process indicated that they might provide a strategy to develop novel ABA agonists or antagonist and be used as probe to investigate the function of different ABA receptors. PMID:25913114

  20. Cytosolic alkalinization mediated by abscisic Acid is necessary, but not sufficient, for abscisic Acid-induced gene expression in barley aleurone protoplasts.

    PubMed

    van der Veen, R; Heimovaara-Dijkstra, S; Wang, M

    1992-10-01

    We investigated whether intracellular pH (pH(i)) is a causal mediator in abscisic acid (ABA)-induced gene expression. We measured the change in pH(i) by a "null-point" method during stimulation of barley (Hordeum vulgare cv Himalaya) aleurone protoplasts with ABA and found that ABA induces an increase in pH(i) from 7.11 to 7.30 within 45 min after stimulation. This increase is inhibited by plasma membrane H(+)-ATPase inhibitors, which induce a decrease in pH(i), both in the presence and absence of ABA. This ABA-induced pH(i) increase precedes the expression of RAB-16 mRNA, as measured by northern analysis. ABA-induced pH(i) changes can be bypassed or clamped by addition of either the weak acids 5,5-dimethyl-2,4-oxazolidinedione and propionic acid, which decrease the pH(i), or the weak bases methylamine and ammonia, which increase the pH(i). Artificial pH(i) increases or decreases induced by weak bases or weak acids, respectively, do not induce RAB-16 mRNA expression. Clamping of the pH(i) at a high value with methylamine or ammonia treatment affected the ABA-induced increase of RAB-16 mRNA only slightly. However, inhibition of the ABA-induced pH(i) increase with weak acid or proton pump inhibitor treatments strongly inhibited the ABA-induced RAB-16 mRNA expression. We conclude that, although the ABA-induced the pH(i) increase is correlated with and even precedes the induction of RAB-16 mRNA expression and is an essential component of the transduction pathway leading from the hormone to gene expression, it is not sufficient to cause such expression.

  1. Photoprotectant improves photostability and bioactivity of abscisic acid under UV radiation.

    PubMed

    Gao, Fei; Hu, Tanglu; Tan, Weiming; Yu, Chunxin; Li, Zhaohu; Zhang, Lizhen; Duan, Liusheng

    2016-05-01

    Photosensitivity causes serious drawback for abscisic acid (ABA) application, but preferable methods to stabilize the compound were not found yet. To select an efficient photoprotectant for the improvement of photostability and bioactivity of ABA when exposed to UV light, we tested the effects of a photostabilizer bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (HS-770) and two UV absorbers 2-hydroxy-4-n-octoxy-benzophenone (UV-531) and 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (BP-4) with or without HS-770 on the photodegradation of ABA. Water soluble UV absorber BP-4 and oil soluble UV absorber UV-531 showed significant photo-stabilizing capability on ABA, possibly due to competitive energy absorption of UVB by the UV absorbers. The two absorbers showed no significant difference. Photostabilizer HS-770 accelerated the photodegradation of ABA and did not improve the photo-stabilizing capability of BP-4, likely due to no absorption in UVB region and salt formation with ABA and BP-4. Approximately 26% more ABA was kept when 280mg/l ABA aqueous solution was irradiated by UV light for 2h in the presence of 200mg/l BP-4. What's more, its left bioactivity on wheat seed (JIMAI 22) germination was greatly kept by BP-4, comparing to that of ABA alone. The 300 times diluent of 280mg/l ABA plus 200mg/l BP-4 after 2h irradiation showed more than 13% inhibition on shoot and root growth of wheat seed than that of ABA diluent alone. We concluded that water soluble UV absorber BP-4 was an efficient agent to keep ABA activity under UV radiation. The results could be used to produce photostable products of ABA compound or other water soluble agrichemicals which are sensitive to UV radiation. The frequencies and amounts of the agrichemicals application could be thereafter reduced. PMID:26963431

  2. Crocetinic acid inhibits hedgehog signaling to inhibit pancreatic cancer stem cells

    PubMed Central

    Rangarajan, Parthasarathy; Subramaniam, Dharmalingam; Paul, Santanu; Kwatra, Deep; Palaniyandi, Kanagaraj; Islam, Shamima; Harihar, Sitaram; Ramalingam, Satish; Gutheil, William; Putty, Sandeep; Pradhan, Rohan; Padhye, Subhash; Welch, Danny R.; Anant, Shrikant; Dhar, Animesh

    2015-01-01

    Pancreatic cancer is the fourth leading cause of cancer deaths in the US and no significant treatment is currently available. Here, we describe the effect of crocetinic acid, which we purified from commercial saffron compound crocetin using high performance liquid chromatography. Crocetinic acid inhibits proliferation of pancreatic cancer cell lines in a dose- and time-dependent manner. In addition, it induced apoptosis. Moreover, the compound significantly inhibited epidermal growth factor receptor and Akt phosphorylation. Furthermore, crocetinic acid decreased the number and size of the pancospheres in a dose-dependent manner, and suppressed the expression of the marker protein DCLK-1 (Doublecortin Calcium/Calmodulin-Dependent Kinase-1) suggesting that crocetinic acid targets cancer stem cells (CSC). To understand the mechanism of CSC inhibition, the signaling pathways affected by purified crocetinic acid were dissected. Sonic hedgehog (Shh) upon binding to its cognate receptor patched, allows smoothened to accumulate and activate Gli transcription factor. Crocetinic acid inhibited the expression of both Shh and smoothened. Finally, these data were confirmed in vivo where the compound at a dose of 0.5 mg/Kg bw suppressed growth of tumor xenografts. Collectively, these data suggest that purified crocetinic acid inhibits pancreatic CSC, thereby inhibiting pancreatic tumorigenesis. PMID:26317547

  3. Calcite crystal growth rate inhibition by polycarboxylic acids

    USGS Publications Warehouse

    Reddy, M.M.; Hoch, A.R.

    2001-01-01

    Calcite crystal growth rates measured in the presence of several polycarboxyclic acids show that tetrahydrofurantetracarboxylic acid (THFTCA) and cyclopentanetetracarboxylic acid (CPTCA) are effective growth rate inhibitors at low solution concentrations (0.01 to 1 mg/L). In contrast, linear polycarbocylic acids (citric acid and tricarballylic acid) had no inhibiting effect on calcite growth rates at concentrations up to 10 mg/L. Calcite crystal growth rate inhibition by cyclic polycarboxyclic acids appears to involve blockage of crystal growth sites on the mineral surface by several carboxylate groups. Growth morphology varied for growth in the absence and in the presence of both THFTCA and CPTCA. More effective growth rate reduction by CPTCA relative to THFTCA suggests that inhibitor carboxylate stereochemical orientation controls calcite surface interaction with carboxylate inhibitors. ?? 20O1 Academic Press.

  4. Influence of chilling and drought on water relations and abscisic acid accumulation in bean

    SciTech Connect

    Vernieri, P.; Pardossi, A.; Tognoni, F. )

    1991-01-01

    Intact bean seedlings were subjected to either chilling (4{degree}C) or drought stress. Leaf water relations and abscisic acid (ABA) content were monitored throughout a stress-recovery cycle. Chilling at low relative humidity (RH) and drought caused similar water deficits, as indicated by the decline in relative water content and water potentials, but they had different effects on ABA accumulation. There was a rapid increase in ABA levels in the leaves of water-deprived plants while only slight ABA accumulation was observed after 48 h of chilling (4{degree}C). After 24 h cold treatment there were large changes in turgor but no change in ABA content. Plants chilled for 24 h accumulated ABA only when transferred to recovery conditions (20{degree}C, 90-95% RH, in the dark) to an extent that was related to the rate of leaf rehydration. When the chilling treatment was performed in a water-saturated atmosphere, plants did not suffer any water stress and ABA levels did not increase over a period of 48 h. However, when the chilling treatment lasted for a longer period (72 h), a significant increase in ABA levels was found also in the absence of water deficit. Experiments performed with leaf discs incubated in a mannitol solution (osmotic potential {minus}1{center dot}6 MPa) at different temperatures indicated that low temperature markedly inhibits ABA synthesis and that water stress induces increases in ABA content only at non-limiting warm temperatures.

  5. Designed abscisic acid analogs as antagonists of PYL-PP2C receptor interactions.

    PubMed

    Takeuchi, Jun; Okamoto, Masanori; Akiyama, Tomonori; Muto, Takuya; Yajima, Shunsuke; Sue, Masayuki; Seo, Mitsunori; Kanno, Yuri; Kamo, Tsunashi; Endo, Akira; Nambara, Eiji; Hirai, Nobuhiro; Ohnishi, Toshiyuki; Cutler, Sean R; Todoroki, Yasushi

    2014-06-01

    The plant stress hormone abscisic acid (ABA) is critical for several abiotic stress responses. ABA signaling is normally repressed by group-A protein phosphatases 2C (PP2Cs), but stress-induced ABA binds Arabidopsis PYR/PYL/RCAR (PYL) receptors, which then bind and inhibit PP2Cs. X-ray structures of several receptor-ABA complexes revealed a tunnel above ABA's 3' ring CH that opens at the PP2C binding interface. Here, ABA analogs with sufficiently long 3' alkyl chains were predicted to traverse this tunnel and block PYL-PP2C interactions. To test this, a series of 3'-alkylsulfanyl ABAs were synthesized with different alkyl chain lengths. Physiological, biochemical and structural analyses revealed that a six-carbon alkyl substitution produced a potent ABA antagonist that was sufficiently active to block multiple stress-induced ABA responses in vivo. This study provides a new approach for the design of ABA analogs, and the results validated structure-based design for this target class. PMID:24792952

  6. Designed abscisic acid analogs as antagonists of PYL-PP2C receptor interactions.

    PubMed

    Takeuchi, Jun; Okamoto, Masanori; Akiyama, Tomonori; Muto, Takuya; Yajima, Shunsuke; Sue, Masayuki; Seo, Mitsunori; Kanno, Yuri; Kamo, Tsunashi; Endo, Akira; Nambara, Eiji; Hirai, Nobuhiro; Ohnishi, Toshiyuki; Cutler, Sean R; Todoroki, Yasushi

    2014-06-01

    The plant stress hormone abscisic acid (ABA) is critical for several abiotic stress responses. ABA signaling is normally repressed by group-A protein phosphatases 2C (PP2Cs), but stress-induced ABA binds Arabidopsis PYR/PYL/RCAR (PYL) receptors, which then bind and inhibit PP2Cs. X-ray structures of several receptor-ABA complexes revealed a tunnel above ABA's 3' ring CH that opens at the PP2C binding interface. Here, ABA analogs with sufficiently long 3' alkyl chains were predicted to traverse this tunnel and block PYL-PP2C interactions. To test this, a series of 3'-alkylsulfanyl ABAs were synthesized with different alkyl chain lengths. Physiological, biochemical and structural analyses revealed that a six-carbon alkyl substitution produced a potent ABA antagonist that was sufficiently active to block multiple stress-induced ABA responses in vivo. This study provides a new approach for the design of ABA analogs, and the results validated structure-based design for this target class.

  7. Identification of Interactions between Abscisic Acid and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase.

    PubMed

    Galka, Marek M; Rajagopalan, Nandhakishore; Buhrow, Leann M; Nelson, Ken M; Switala, Jacek; Cutler, Adrian J; Palmer, David R J; Loewen, Peter C; Abrams, Suzanne R; Loewen, Michele C

    2015-01-01

    Abscisic acid ((+)-ABA) is a phytohormone involved in the modulation of developmental processes and stress responses in plants. A chemical proteomics approach using an ABA mimetic probe was combined with in vitro assays, isothermal titration calorimetry (ITC), x-ray crystallography and in silico modelling to identify putative (+)-ABA binding-proteins in crude extracts of Arabidopsis thaliana. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was identified as a putative ABA-binding protein. Radiolabelled-binding assays yielded a Kd of 47 nM for (+)-ABA binding to spinach Rubisco, which was validated by ITC, and found to be similar to reported and experimentally derived values for the native ribulose-1,5-bisphosphate (RuBP) substrate. Functionally, (+)-ABA caused only weak inhibition of Rubisco catalytic activity (Ki of 2.1 mM), but more potent inhibition of Rubisco activation (Ki of ~ 130 μM). Comparative structural analysis of Rubisco in the presence of (+)-ABA with RuBP in the active site revealed only a putative low occupancy (+)-ABA binding site on the surface of the large subunit at a location distal from the active site. However, subtle distortions in electron density in the binding pocket and in silico docking support the possibility of a higher affinity (+)-ABA binding site in the RuBP binding pocket. Overall we conclude that (+)-ABA interacts with Rubisco. While the low occupancy (+)-ABA binding site and weak non-competitive inhibition of catalysis may not be relevant, the high affinity site may allow ABA to act as a negative effector of Rubisco activation. PMID:26197050

  8. Identification of Interactions between Abscisic Acid and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase

    PubMed Central

    Galka, Marek M.; Rajagopalan, Nandhakishore; Buhrow, Leann M.; Nelson, Ken M.; Switala, Jacek; Cutler, Adrian J.; Palmer, David R. J.; Loewen, Peter C.; Abrams, Suzanne R.; Loewen, Michele C.

    2015-01-01

    Abscisic acid ((+)-ABA) is a phytohormone involved in the modulation of developmental processes and stress responses in plants. A chemical proteomics approach using an ABA mimetic probe was combined with in vitro assays, isothermal titration calorimetry (ITC), x-ray crystallography and in silico modelling to identify putative (+)-ABA binding-proteins in crude extracts of Arabidopsis thaliana. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was identified as a putative ABA-binding protein. Radiolabelled-binding assays yielded a Kd of 47 nM for (+)-ABA binding to spinach Rubisco, which was validated by ITC, and found to be similar to reported and experimentally derived values for the native ribulose-1,5-bisphosphate (RuBP) substrate. Functionally, (+)-ABA caused only weak inhibition of Rubisco catalytic activity (Ki of 2.1 mM), but more potent inhibition of Rubisco activation (Ki of ~ 130 μM). Comparative structural analysis of Rubisco in the presence of (+)-ABA with RuBP in the active site revealed only a putative low occupancy (+)-ABA binding site on the surface of the large subunit at a location distal from the active site. However, subtle distortions in electron density in the binding pocket and in silico docking support the possibility of a higher affinity (+)-ABA binding site in the RuBP binding pocket. Overall we conclude that (+)-ABA interacts with Rubisco. While the low occupancy (+)-ABA binding site and weak non-competitive inhibition of catalysis may not be relevant, the high affinity site may allow ABA to act as a negative effector of Rubisco activation. PMID:26197050

  9. Arabidopsis ABA-Activated Kinase MAPKKK18 is Regulated by Protein Phosphatase 2C ABI1 and the Ubiquitin–Proteasome Pathway

    PubMed Central

    Mitula, Filip; Tajdel, Malgorzata; Cieśla, Agata; Kasprowicz-Maluśki, Anna; Kulik, Anna; Babula-Skowrońska, Danuta; Michalak, Michal; Dobrowolska, Grazyna; Sadowski, Jan; Ludwików, Agnieszka

    2015-01-01

    Phosphorylation and dephosphorylation events play an important role in the transmission of the ABA signal. Although SnRK2 [sucrose non-fermenting1-related kinase2] protein kinases and group A protein phosphatase type 2C (PP2C)-type phosphatases constitute the core ABA pathway, mitogen-activated protein kinase (MAPK) pathways are also involved in plant response to ABA. However, little is known about the interplay between MAPKs and PP2Cs or SnRK2 in the regulation of ABA pathways. In this study, an effort was made to elucidate the role of MAP kinase kinase kinase18 (MKKK18) in relation to ABA signaling and response. The MKKK18 knockout lines showed more vigorous root growth, decreased abaxial stomatal index and increased stomatal aperture under normal growth conditions, compared with the control wild-type Columbia line. In addition to transcriptional regulation of the MKKK18 promoter by ABA, we demonstrated using in vitro and in vivo kinase assays that the kinase activity of MKKK18 was regulated by ABA. Analysis of the cellular localization of MKKK18 showed that the active kinase was targeted specifically to the nucleus. Notably, we identified abscisic acid insensitive 1 (ABI1) PP2C as a MKKK18-interacting protein, and demonstrated that ABI1 inhibited its activity. Using a cell-free degradation assay, we also established that MKKK18 was unstable and was degraded by the proteasome pathway. The rate of MKKK18 degradation was delayed in the ABI1 knockout line. Overall, we provide evidence that ABI1 regulates the activity and promotes proteasomal degradation of MKKK18. PMID:26443375

  10. Involvement of ABA- and H2O2-dependent cytosolic glucose-6-phosphate dehydrogenase in maintaining redox homeostasis in soybean roots under drought stress.

    PubMed

    Wang, Huahua; Yang, Lidan; Li, Yan; Hou, Junjie; Huang, Junjun; Liang, Weihong

    2016-10-01

    The roles of abscisic acid (ABA) and hydrogen peroxide (H2O2) in inducing glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) activity and the possible roles of G6PDH in regulating ascorbate-glutathione (AsA-GSH) cycle were investigated in soybean (Glycine max L.) roots under drought stress. Drought caused a marked increase of the total and cytosolic G6PDH activities and triggered a rapid ABA and H2O2 accumulation in soybean roots. Exogenous ABA or H2O2 treatment elevated the total and cytosolic G6PDH activities, whereas suppressing ABA or H2O2 production inhibited the drought-induced increase in total and cytosolic G6PDH activities, suggesting that ABA and H2O2 are required for drought-induced increase of total G6PDH activity, namely cytosolic G6PDH activity. Furthermore, ABA induced H2O2 production by stimulating NADPH oxidase activity under drought stress. Moreover, drought significantly increased the contents of AsA and GSH and the activities of key enzymes in AsA-GSH cycle, while application of G6PDH inhibitor to seedlings significantly reduced the above effect induced by drought. Taken together, these results indicate that H2O2 acting as a downstream signaling molecule of ABA mediates drought-induced increase in cytosolic G6PDH activity, and that enhanced cytosolic G6PDH activity maintains cellular redox homeostasis by regulating AsA-GSH cycle in soybean roots. PMID:27285781

  11. Involvement of ABA- and H2O2-dependent cytosolic glucose-6-phosphate dehydrogenase in maintaining redox homeostasis in soybean roots under drought stress.

    PubMed

    Wang, Huahua; Yang, Lidan; Li, Yan; Hou, Junjie; Huang, Junjun; Liang, Weihong

    2016-10-01

    The roles of abscisic acid (ABA) and hydrogen peroxide (H2O2) in inducing glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) activity and the possible roles of G6PDH in regulating ascorbate-glutathione (AsA-GSH) cycle were investigated in soybean (Glycine max L.) roots under drought stress. Drought caused a marked increase of the total and cytosolic G6PDH activities and triggered a rapid ABA and H2O2 accumulation in soybean roots. Exogenous ABA or H2O2 treatment elevated the total and cytosolic G6PDH activities, whereas suppressing ABA or H2O2 production inhibited the drought-induced increase in total and cytosolic G6PDH activities, suggesting that ABA and H2O2 are required for drought-induced increase of total G6PDH activity, namely cytosolic G6PDH activity. Furthermore, ABA induced H2O2 production by stimulating NADPH oxidase activity under drought stress. Moreover, drought significantly increased the contents of AsA and GSH and the activities of key enzymes in AsA-GSH cycle, while application of G6PDH inhibitor to seedlings significantly reduced the above effect induced by drought. Taken together, these results indicate that H2O2 acting as a downstream signaling molecule of ABA mediates drought-induced increase in cytosolic G6PDH activity, and that enhanced cytosolic G6PDH activity maintains cellular redox homeostasis by regulating AsA-GSH cycle in soybean roots.

  12. MBF1s regulate ABA-dependent germination of Arabidopsis seeds.

    PubMed

    Di Mauro, María Florencia; Iglesias, María José; Arce, Débora Pamela; Valle, Estela Marta; Arnold, Roberto Benech; Tsuda, Kenichi; Yamazaki, Ken-ichi; Casalongué, Claudia Anahí; Godoy, Andrea Verónica

    2012-02-01

    Transcriptional co-activators of the multiprotein bridging factor 1 (MBF1) controls gene expression by connecting transcription factors and the basal transcription machinery. In Arabidopsis thaliana functions of MBF1 genes have been related to stress tolerance and developmental alterations. Endogenous ABA plays a major role in the regulation of Arabidopsis seed dormancy and germination. Seed dormancy and ABA sensitivity are enhanced in ethylene insensitive mutants suggesting that ethylene signal transduction pathway is necessary to fully develop ABA-dependent germination. In this report we showed that a triple knock-down mutant for Arabidopsis MBF1 genes (abc-) has enhanced seed dormancy and displays hypersensitivity to exogenous ABA. In addition, higher ABA contents were detected in abc- seeds after imbibition. These evidences suggest a negative role of MBF1s genes in ABA-dependent inhibition of germination. The participation of MBF1s in ethylene signal transduction pathway is also discussed.

  13. FERONIA interacts with ABI2-type phosphatases to facilitate signaling cross-talk between abscisic acid and RALF peptide in Arabidopsis.

    PubMed

    Chen, Jia; Yu, Feng; Liu, Ying; Du, Changqing; Li, Xiushan; Zhu, Sirui; Wang, Xianchun; Lan, Wenzhi; Rodriguez, Pedro L; Liu, Xuanming; Li, Dongping; Chen, Liangbi; Luan, Sheng

    2016-09-13

    Receptor-like kinase FERONIA (FER) plays a crucial role in plant response to small molecule hormones [e.g., auxin and abscisic acid (ABA)] and peptide signals [e.g., rapid alkalinization factor (RALF)]. It remains unknown how FER integrates these different signaling events in the control of cell growth and stress responses. Under stress conditions, increased levels of ABA will inhibit cell elongation in the roots. In our previous work, we have shown that FER, through activation of the guanine nucleotide exchange factor 1 (GEF1)/4/10-Rho of Plant 11 (ROP11) pathway, enhances the activity of the phosphatase ABA Insensitive 2 (ABI2), a negative regulator of ABA signaling, thereby inhibiting ABA response. In this study, we found that both RALF and ABA activated FER by increasing the phosphorylation level of FER. The FER loss-of-function mutant displayed strong hypersensitivity to both ABA and abiotic stresses such as salt and cold conditions, indicating that FER plays a key role in ABA and stress responses. We further showed that ABI2 directly interacted with and dephosphorylated FER, leading to inhibition of FER activity. Several other ABI2-like phosphatases also function in this pathway, and ABA-dependent FER activation required PYRABACTIN RESISTANCE (PYR)/PYR1-LIKE (PYL)/REGULATORY COMPONENTS OF ABA RECEPTORS (RCAR)-A-type protein phosphatase type 2C (PP2CA) modules. Furthermore, suppression of RALF1 gene expression, similar to disruption of the FER gene, rendered plants hypersensitive to ABA. These results formulated a mechanism for ABA activation of FER and for cross-talk between ABA and peptide hormone RALF in the control of plant growth and responses to stress signals. PMID:27566404

  14. Arabidopsis Tóxicos en Levadura 78 (AtATL78) mediates ABA-dependent ROS signaling in response to drought stress.

    PubMed

    Suh, Ji Yeon; Kim, Soo Jin; Oh, Tae Rin; Cho, Seok Keun; Yang, Seong Wook; Kim, Woo Taek

    2016-01-01

    Plants have developed a variety of complicated responses to cope with drought, one of the most challenging environmental stresses. As a quick response, plants rapidly inhibit stomatal opening under the control of abscisic acid (ABA) signaling pathway, in order to preserve water. Here, we report that Arabidopsis Tóxicos en Levadura (ATL), a RING-type E3 ubiquitin ligase, mediates the ABA-dependent stomatal closure. In contrast to wild-type plants, the stomatal closure was fully impaired in atatl78 mutant plants even in the presence of exogenous ABA and reactive oxygen species (ROS). Besides, under high concentrations of Ca(2+), a down-stream signaling molecule of ABA signaling pathway, atatl78 mutant plants successfully closed the pores. Furthermore, AtATL78 protein indirectly associated with catalases and the deficiency of AtATL78 led the reduction of catalase activity and H2O2, implying the function of AtATL78 in the modulation of ROS activity. Based on these results, we suggest that AtATL78 possibly plays a role in promoting ROS-mediated ABA signaling pathway during drought stress. PMID:26612255

  15. Abscisic acid regulation of DC8, a carrot embryonic gene. [Daucus carota

    SciTech Connect

    Hatzopoulos, P.; Fong, F.; Sung, Z.R. Texas A M Univ., College Station )

    1990-10-01

    DC8 encodes a hydrophylic 66 kilodalton protein located in the cytoplasm and cell walls of carrot (Daucus carota) embryo and endosperm. During somatic embryogenesis, the levels of DC8 mRNA and protein begin to increase 5 days after removal of auxin. To study the role of abscisic acid (ABA) in the regulation of DC8 gene, fluridone, 1-methyl-3-phenyl,-5(3-trifluoro-methyl-phenyl)-4(1H)-pyridinone, was used to inhibit the endogenous ABA content of the embryos. Fluridone, 50 micrograms per milliliter, effectively inhibits the accumulation of ABA in globular-tage embryos. Western and Northern analysis show that when fluridone is added to the culture medium DC8 protein and mRNA decrease to very low levels. ABA added to fluridone supplemented culture media restores the DC8 protein and mRNA to control levels. Globular-stage embryos contain 0.9 to 1.4 {times} 10{sup {minus}7} molar ABA while 10{sup {minus}6} molar exogenously supplied ABA is the optimal concentration for restoration of DC8 protein accumulation in fluridone-treated embryos. The mRNA level is increased after 15 minutes of ABA addition and reaches maximal levels by 60 minutes. Evidence is presented that, unlike other ABA-regulated genes, DC8 is not induced in nonembryonic tissues via desiccation nor addition of ABA.

  16. Inhibition of plant fatty acid synthesis by nitroimidazoles.

    PubMed Central

    Jones, A V; Harwood, J L; Stratford, M R; Stumpf, P K

    1981-01-01

    1. The effect of the addition of a number of nitroimidazoles was tested on fatty acid synthesis by germinating pea seeds, isolated lettuce chloroplasts and a soluble fraction from pea seeds. 2. All the compounds tested had a marked inhibition on stearate desaturation by lettuce chloroplasts and on the synthesis of very-long-chain fatty acids by pea seeds. 3. In contrast, the effect of the drugs on total fatty acid synthesis from [14C]acetate in chloroplasts was related to the compound's electron reduction potentials. 4. Of the compounds used, only metronidazole had a marked inhibition on palmitate elongation in the systems tested. 5. The mechanism of inhibition of plant fatty acid synthesis by nitroimidazoles is discussed and the possible relevance of these findings to their neurotoxicity is suggested. PMID:7325993

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

    PubMed

    Govind, Geetha; Seiler, Christiane; Wobus, Ulrich; Sreenivasulu, Nese

    2011-08-01

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

  18. Membrane-associated transcription factor peptidase, site-2 protease, antagonizes ABA signaling in Arabidopsis.

    PubMed

    Zhou, Shun-Fan; Sun, Le; Valdés, Ana Elisa; Engström, Peter; Song, Ze-Ting; Lu, Sun-Jie; Liu, Jian-Xiang

    2015-10-01

    Abscisic acid plays important roles in maintaining seed dormancy while gibberellins (GA) and other phytohormones antagonize ABA to promote germination. However, how ABA signaling is desensitized during the transition from dormancy to germination is still poorly understood. We functionally characterized the role of membrane-associated transcription factor peptidase, site-2 protease (S2P), in ABA signaling during seed germination in Arabidopsis. Genetic analysis showed that loss-of-function of S2P conferred high ABA sensitivity during seed germination, and expression of the activated form of membrane-associated transcription factor bZIP17, in which the transmembrane domain and endoplasmic reticulum (ER) lumen-facing C-terminus were deleted, in the S2P mutant rescued its ABA-sensitive phenotype. MYC and green fluorescent protein (GFP)-tagged bZIP17 were processed and translocated from the ER to the nucleus in response to ABA treatment. Furthermore, genes encoding negative regulators of ABA signaling, such as the transcription factor ATHB7 and its target genes HAB1, HAB2, HAI1 and AHG3, were up-regulated in seeds of the wild-type upon ABA treatment; this up-regulation was impaired in seeds of S2P mutants. Our results suggest that S2P desensitizes ABA signaling during seed germination through regulating the activation of the membrane-associated transcription factor bZIP17 and therefore controlling the expression level of genes encoding negative regulators of ABA signaling. PMID:25919792

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

    PubMed Central

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

    2016-01-01

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

  20. Transpiration, CO2 assimilation, WUE, and stomatal aperture in leaves of Viscum album (L.): Effect of abscisic acid (ABA) in the xylem sap of its host (Populus x euamericana).

    PubMed

    Escher, Peter; Peuke, Andreas D; Bannister, Peter; Fink, Siegfried; Hartung, Wolfram; Jiang, Fan; Rennenberg, Heinz

    2008-01-01

    Leaves of the mistletoe Viscum album (L.) show a high rate of transpiration, even when the host is under severe drought stress. The hypothesis that a strong control of ABA influx from the xylem sap of the host into the mistletoe prevents stomatal closure in mistletoe leaves was tested under the following conditions: sections of poplar twigs carrying a mistletoe were perfused with artificial xylem sap that contained different ABA concentrations and both transpiration and ABA levels were analysed in mistletoe leaves. Despite variation by a factor of 10(4), the ABA content of the host xylem did not affect ABA levels, leaf transpiration, CO(2) assimilation, WUE, or the degree of stomatal aperture in mistletoe leaves. These observations support the hypothesis of a strong control of ABA influx from the host of the xylem into the mistletoe, although degradation of ABA before it enters the mistletoe leaves cannot be excluded. This mechanism may ensure a water and nutritional status favourable for the mistletoe, even if the water status of the host is impaired. Despite the lack of short-term sensitivity of ABA levels in mistletoe leaves to even strong changes of ABA levels in the xylem sap of the host, ABA levels in mistletoe leaves were relatively high compared to ABA levels in the leaves of several tree species including poplar. Since significant transpiration of the mistletoe leaves was observed despite high ABA levels, a diminished sensitivity of the stomata of mistletoe leaves to ABA has to be concluded. The stomatal density of adaxial Viscum leaves of 89+/-23 stomata per mm is lower than those reported in a study performed at the end of the 19th century.

  1. cGMP-dependent ABA-induced stomatal closure in the ABA-insensitive Arabidopsis mutant abi1-1.

    PubMed

    Dubovskaya, Lyudmila V; Bakakina, Yulia S; Kolesneva, Ekaterina V; Sodel, Dmitry L; McAinsh, Martin R; Hetherington, Alistair M; Volotovski, Igor D

    2011-07-01

    • The drought hormone abscisic acid (ABA) is widely known to produce reductions in stomatal aperture in guard cells. The second messenger cyclic guanosine 3', 5'-monophosphate (cGMP) is thought to form part of the signalling pathway by which ABA induces stomatal closure. • We have examined the signalling events during cGMP-dependent ABA-induced stomatal closure in wild-type Arabidopsis plants and plants of the ABA-insensitive Arabidopsis mutant abi1-1. • We show that cGMP acts downstream of hydrogen peroxide (H(2) O(2) ) and nitric oxide (NO) in the signalling pathway by which ABA induces stomatal closure. H(2) O(2) - and NO-induced increases in the cytosolic free calcium concentration ([Ca(2+) ](cyt) ) were cGMP-dependent, positioning cGMP upstream of [Ca(2+) ](cyt) , and involved the action of the type 2C protein phosphatase ABI1. Increases in cGMP were mediated through the stimulation of guanylyl cyclase by H(2) O(2) and NO. We identify nucleoside diphosphate kinase as a new cGMP target protein in Arabidopsis. • This study positions cGMP downstream of ABA-induced changes in H(2) O(2) and NO, and upstream of increases in [Ca(2+) ](cyt) in the signalling pathway leading to stomatal closure.

  2. Ethylene responses in rice roots and coleoptiles are differentially regulated by a carotenoid isomerase-mediated abscisic acid pathway.

    PubMed

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

    2015-04-01

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

  3. ABA crosstalk with ethylene and nitric oxide in seed dormancy and germination

    PubMed Central

    Arc, Erwann; Sechet, Julien; Corbineau, Françoise; Rajjou, Loïc; Marion-Poll, Annie

    2013-01-01

    Dormancy is an adaptive trait that enables seed germination to coincide with favorable environmental conditions. It has been clearly demonstrated that dormancy is induced by abscisic acid (ABA) during seed development on the mother plant. After seed dispersal, germination is preceded by a decline in ABA in imbibed seeds, which results from ABA catabolism through 8′-hydroxylation. The hormonal balance between ABA and gibberellins (GAs) has been shown to act as an integrator of environmental cues to maintain dormancy or activate germination. The interplay of ABA with other endogenous signals is however less documented. In numerous species, ethylene counteracts ABA signaling pathways and induces germination. In Brassicaceae seeds, ethylene prevents the inhibitory effects of ABA on endosperm cap weakening, thereby facilitating endosperm rupture and radicle emergence. Moreover, enhanced seed dormancy in Arabidopsis ethylene-insensitive mutants results from greater ABA sensitivity. Conversely, ABA limits ethylene action by down-regulating its biosynthesis. Nitric oxide (NO) has been proposed as a common actor in the ABA and ethylene crosstalk in seed. Indeed, convergent evidence indicates that NO is produced rapidly after seed imbibition and promotes germination by inducing the expression of the ABA 8′-hydroxylase gene, CYP707A2, and stimulating ethylene production. The role of NO and other nitrogen-containing compounds, such as nitrate, in seed dormancy breakage and germination stimulation has been reported in several species. This review will describe our current knowledge of ABA crosstalk with ethylene and NO, both volatile compounds that have been shown to counteract ABA action in seeds and to improve dormancy release and germination. PMID:23531630

  4. ABA crosstalk with ethylene and nitric oxide in seed dormancy and germination.

    PubMed

    Arc, Erwann; Sechet, Julien; Corbineau, Françoise; Rajjou, Loïc; Marion-Poll, Annie

    2013-01-01

    Dormancy is an adaptive trait that enables seed germination to coincide with favorable environmental conditions. It has been clearly demonstrated that dormancy is induced by abscisic acid (ABA) during seed development on the mother plant. After seed dispersal, germination is preceded by a decline in ABA in imbibed seeds, which results from ABA catabolism through 8'-hydroxylation. The hormonal balance between ABA and gibberellins (GAs) has been shown to act as an integrator of environmental cues to maintain dormancy or activate germination. The interplay of ABA with other endogenous signals is however less documented. In numerous species, ethylene counteracts ABA signaling pathways and induces germination. In Brassicaceae seeds, ethylene prevents the inhibitory effects of ABA on endosperm cap weakening, thereby facilitating endosperm rupture and radicle emergence. Moreover, enhanced seed dormancy in Arabidopsis ethylene-insensitive mutants results from greater ABA sensitivity. Conversely, ABA limits ethylene action by down-regulating its biosynthesis. Nitric oxide (NO) has been proposed as a common actor in the ABA and ethylene crosstalk in seed. Indeed, convergent evidence indicates that NO is produced rapidly after seed imbibition and promotes germination by inducing the expression of the ABA 8'-hydroxylase gene, CYP707A2, and stimulating ethylene production. The role of NO and other nitrogen-containing compounds, such as nitrate, in seed dormancy breakage and germination stimulation has been reported in several species. This review will describe our current knowledge of ABA crosstalk with ethylene and NO, both volatile compounds that have been shown to counteract ABA action in seeds and to improve dormancy release and germination.

  5. Molecular Mimicry Regulates ABA Signaling by SnRK2 Kinases and PP2C Phosphatases

    SciTech Connect

    Soon, Fen-Fen; Ng, Ley-Moy; Zhou, X. Edward; West, Graham M.; Kovach, Amanda; Tan, M.H. Eileen; Suino-Powell, Kelly M.; He, Yuanzheng; Xu, Yong; Chalmers, Michael J.; Brunzelle, Joseph S.; Zhang, Huiming; Yang, Huaiyu; Jiang, Hualiang; Li, Jun; Yong, Eu-Leong; Cutler, Sean; Zhu, Jian-Kang; Griffin, Patrick R.; Melcher, Karsten; Xu, H. Eric

    2014-10-02

    Abscisic acid (ABA) is an essential hormone for plants to survive environmental stresses. At the center of the ABA signaling network is a subfamily of type 2C protein phosphatases (PP2Cs), which form exclusive interactions with ABA receptors and subfamily 2 Snfl-related kinase (SnRK2s). Here, we report a SnRK2-PP2C complex structure, which reveals marked similarity in PP2C recognition by SnRK2 and ABA receptors. In the complex, the kinase activation loop docks into the active site of PP2C, while the conserved ABA-sensing tryptophan of PP2C inserts into the kinase catalytic cleft, thus mimicking receptor-PP2C interactions. These structural results provide a simple mechanism that directly couples ABA binding to SnRK2 kinase activation and highlight a new paradigm of kinase-phosphatase regulation through mutual packing of their catalytic sites.

  6. Molecular Mimicry Regulates ABA Signaling by SnRK2 Kinases and PP2C Phosphatases

    PubMed Central

    Soon, Fen-Fen; Ng, Ley-Moy; Zhou, X. Edward; West, Graham M.; Kovach, Amanda; Tan, M. H. Eileen; Suino-Powell, Kelly M.; He, Yuanzheng; Xu, Yong; Chalmers, Michael J.; Brunzelle, Joseph S.; Zhang, Huiming; Yang, Huaiyu; Jiang, Hualiang; Li, Jun; Yong, Eu-Leong; Cutler, Sean; Zhu, Jian-Kang; Griffin, Patrick R.; Melcher, Karsten; Xu, H. Eric

    2013-01-01

    Abscisic acid (ABA) is an essential hormone for plants to survive environmental stresses. At the center of the ABA signaling network is a subfamily of type 2C protein phosphatases (PP2Cs), which form exclusive interactions with ABA receptors and subfamily 2 Snfl-related kinase (SnRK2s). Here, we report a SnRK2-PP2C complex structure, which reveals marked similarity in PP2C recognition by SnRK2 and ABA receptors. In the complex, the kinase activation loop docks into the active site of PP2C, while the conserved ABA-sensing tryptophan of PP2C inserts into the kinase catalytic cleft, thus mimicking receptor-PP2C interactions. These structural results provide a simple mechanism that directly couples ABA binding to SnRK2 kinase activation and highlight a new paradigm of kinase-phosphatase regulation through mutual packing of their catalytic sites. PMID:22116026

  7. Alkyl hydroxybenzoic acid derivatives that inhibit HIV-1 protease dimerization.

    PubMed

    Flausino, O A; Dufau, L; Regasini, L O; Petrônio, M S; Silva, D H S; Rose, T; Bolzani, V S; Reboud-Ravaux, M

    2012-01-01

    The therapeutic potential of gallic acid and its derivatives as anti-cancer, antimicrobial and antiviral agents is well known. We have examined the mechanism by which natural gallic acid and newly synthesized gallic acid alkyl esters and related protocatechuic acid alkyl esters inhibit HIV-1 protease to compare the influence of the aromatic ring substitutions on inhibition. We used Zhang-Poorman's kinetic analysis and fluorescent probe binding to demonstrate that several gallic and protecatechuic acid alkyl esters inhibited HIV-1 protease by preventing the dimerization of this obligate homodimeric aspartic protease rather than targeting the active site. The tri-hydroxy substituted benzoic moiety in gallates was more favorable than the di-substituted one in protocatechuates. In both series, the type of inhibition, its mechanism and the inhibitory efficiency dramatically depended on the length of the alkyl chain: no inhibition with alkyl chains less than 8 carbon atoms long. Molecular dynamics simulations corroborated the kinetic data and propose that gallic esters are intercalated between the two N- and C-monomer ends. They complete the β-sheet and disrupt the dimeric enzyme. The best gallic ester (14 carbon atoms, K(id) of 320 nM) also inhibited the multi-mutated protease MDR-HM. These results will aid the rational design of future generations of non-peptide inhibitors of HIV-1 protease dimerization that inhibit multi-mutated proteases. Finally, our work suggests the wide use of gallic and protocatechuic alkyl esters to dissociate intermolecular β-sheets involved in protein-protein interactions.

  8. Overexpression of an ABA biosynthesis gene using a stress inducible promoter enhances drought resistance in petunia

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plants respond to drought stress by closing their stomata and reducing transpirational water loss. The plant hormone abscisic acid (ABA) regulates growth and stomatal closure particularly when the plant is under environmental stresses. One of the key enzymes in the ABA biosynthesis of higher plants ...

  9. Abscisic Acid Is a General Negative Regulator of Arabidopsis Axillary Bud Growth1[OPEN

    PubMed Central

    Yao, Chi; Finlayson, Scott A.

    2015-01-01

    Branching is an important process controlled by intrinsic programs and by environmental signals transduced by a variety of plant hormones. Abscisic acid (ABA) was previously shown to mediate Arabidopsis (Arabidopsis thaliana) branching responses to the ratio of red light (R) to far-red light (FR; an indicator of competition) by suppressing bud outgrowth from lower rosette positions under low R:FR. However, the role of ABA in regulating branching more generally was not investigated. This study shows that ABA restricts lower bud outgrowth and promotes correlative inhibition under both high and low R:FR. ABA was elevated in buds exhibiting delayed outgrowth resulting from bud position and low R:FR and decreased in elongating buds. ABA was reduced in lower buds of hyperbranching mutants deficient in auxin signaling (AUXIN RESISTANT1), MORE AXILLARY BRANCHING (MAX) signaling (MAX2), and BRANCHED1 (BRC1) function, and partial suppression of branch elongation in these mutants by exogenous ABA suggested that ABA may act downstream of these components. Bud BRC1 expression was not altered by exogenous ABA, consistent with a downstream function for ABA. However, the expression of genes encoding the indole-3-acetic acid (IAA) biosynthesis enzyme TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS1, the auxin transporter PIN-FORMED1, and the cell cycle genes CYCLIN A2;1 and PROLIFERATING CELL NUCLEAR ANTIGEN1 in buds was suppressed by ABA, suggesting that it may inhibit bud growth in part by suppressing elements of the cell cycle machinery and bud-autonomous IAA biosynthesis and transport. ABA was found to suppress bud IAA accumulation, thus confirming this aspect of its action. PMID:26149576

  10. Overexpression of an Arabidopsis cysteine-rich receptor-like protein kinase, CRK5, enhances abscisic acid sensitivity and confers drought tolerance

    PubMed Central

    Lu, Kai; Liang, Shan; Wu, Zhen; Bi, Chao; Yu, Yong-Tao; Wang, Xiao-Fang; Zhang, Da-Peng

    2016-01-01

    Receptor-like kinases (RLKs) have been reported to regulate many developmental and defense process, but only a few members have been functionally characterized. In the present study, our observations suggest that one of the RLKs, a membrane-localized cysteine-rich receptor-like protein kinase, CRK5, is involved in abscisic acid (ABA) signaling in Arabidopsis thaliana. Overexpression of CRK5 increases ABA sensitivity in ABA-induced early seedling growth arrest and promotion of stomatal closure and inhibition of stomatal opening. Interestingly, and importantly, overexpression of CRK5 enhances plant drought tolerance without affecting plant growth at the mature stages and plant productivity. Transgenic lines overexpressing a mutated form of CRK5, CRK5 K372E with the change of the 372nd conserved amino acid residue from lysine to glutamic acid in its kinase domain, result in wild-type ABA and drought responses, supporting the role of CRK5 in ABA signaling. The loss-of-function mutation of the CRK5 gene does not affect the ABA response, while overexpression of two homologs of CRK5, CRK4 and CRK19, confers ABA responses, suggesting that these CRK members function redundantly. We further showed that WRKY18, WRKY40 and WRKY60 transcription factors repress the expression of CRK5, and that CRK5 likely functions upstream of ABI2 in ABA signaling. These findings help in understanding the complex ABA signaling network. PMID:27406784

  11. Eskimo plasma constituents, dihomo-gamma-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid inhibit the release of atherogenic mitogens.

    PubMed

    Smith, D L; Willis, A L; Nguyen, N; Conner, D; Zahedi, S; Fulks, J

    1989-01-01

    Studies in man and laboratory animals suggest that omega 3 polyunsaturated fatty acid constituents of fish oils have antiatherosclerotic properties. We have studied the effects of several such polyunsaturated fatty acids for ability to modify the in vitro release of mitogens from human platelets. Such mitogens may produce the fibro-proliferative component of atherosclerotic plaques. Both 5,8,11,14,17-eicosapentaenoic acid (20:5 omega 3) and 4,7,10,13,16,19-docosahexaenoic acid (22:6 omega 3), major constituents of fish oils, inhibited adenosine diphosphate-induced aggregation of platelets and the accompanying release of mitogens. These effects are dose dependent. Linolenic acid (18:3 omega 3), the biosynthetic precursor of eicosapentaenoic acid, also inhibited platelet aggregation and mitogen release. Eicosapentaenoic acid also inhibited mitogen release from human monocyte-derived macrophages, which, in vivo, are an additional source of mitogens during atherogenesis. Potent inhibition of human platelet aggregation and mitogen release was also seen with dihomo-gamma-linolenic acid (8,11,14-eicosatrienoic acid 20:3 omega 6), whose levels are reportedly elevated in Eskimos subsisting on marine diets. We conclude that diets that elevate plasma and/or tissue levels of eicosapentaenoic acid, docosahexaenoic acid and dihomo-gamma-linolenic acid precursor gamma-linolenic acid (18:3 omega 6) may exert antiatherosclerotic effects by inhibiting the release of mitogens from platelets and other cells.

  12. Endogenous abscisic acid is involved in methyl jasmonate-induced reactive oxygen species and nitric oxide production but not in cytosolic alkalization in Arabidopsis guard cells.

    PubMed

    Ye, Wenxiu; Hossain, Mohammad Anowar; Munemasa, Shintaro; Nakamura, Yoshimasa; Mori, Izumi C; Murata, Yoshiyuki

    2013-09-01

    We recently demonstrated that endogenous abscisic acid (ABA) is involved in methyl jasmonate (MeJA)-induced stomatal closure in Arabidopsis thaliana. In this study, we investigated whether endogenous ABA is involved in MeJA-induced reactive oxygen species (ROS) and nitric oxide (NO) production and cytosolic alkalization in guard cells using an ABA-deficient Arabidopsis mutant, aba2-2, and an inhibitor of ABA biosynthesis, fluridon (FLU). The aba2-2 mutation impaired MeJA-induced ROS and NO production. FLU inhibited MeJA-induced ROS production in wild-type guard cells. Pretreatment with 0.1 μM ABA, which does not induce stomatal closure in the wild type, complemented the insensitivity to MeJA of the aba2-2 mutant. However, MeJA induced cytosolic alkalization in both wild-type and aba2-2 guard cells. These results suggest that endogenous ABA is involved in MeJA-induced ROS and NO production but not in MeJA-induced cytosolic alkalization in Arabidopsis guard cells.

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

    PubMed Central

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

    2015-01-01

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

  14. Inhibition of fucosyltransferase VII by gallic acid and its derivatives.

    PubMed

    Niu, Xiaoda; Fan, Xuedong; Sun, Jing; Ting, Pauline; Narula, Satwant; Lundell, Daniel

    2004-05-01

    Gallic acid (GA) and several gallate derivatives were identified as inhibitors of fucosyltransferase VII (FucT VII). The inhibition by GA and (-)-epigallocatechin gallate (EGCG) is time-dependent and irreversible. GA and EGCG showed inhibition with IC(50) of 60 and 700 nM, respectively, after pre-incubation with FucT VII in the presence of MnCl(2). Absence of MnCl(2) results in significantly weaker inhibition. Complexation of Mn(2+) with GA, EGCG, and gallate esters was observed. Such complexation, however, is not rate-limiting for the inhibition of FucT VII. Therefore, time-dependent inhibition of fucosyltransferases by GA and EGCG is likely due to the slow inactivation by the inhibitors or Mn-inhibitor complex. Although Mg(2+) or Ca(2+) can replace Mn(2+) for FucT VII activation, none forms a complex with GA or EGCG and hence results in weaker inhibition of FucT VII. GA and EGCG also inhibit FucT IV and alpha2,3-(N)-sialyltransferase in the low micromolar range. The structure-function divergence could be observed, as EGCG, but not GA or gallate esters, inhibits Zn(2+) containing metalloproteases such as TNFalpha convertase, matrix metalloproteases 2 and 7.

  15. Growth and graviresponsiveness of primary roots of Zea mays seedlings deficient in abscisic acid and gibberellic acid

    NASA Technical Reports Server (NTRS)

    Moore, R.; Dickey, K.

    1985-01-01

    The objective of this research was to determine if gibberellic acid (GA) and/or abscisic acid (ABA) are necessary for graviresponsiveness by primary roots of Zea mays. To accomplish this objective we measured the growth and graviresponsiveness of primary roots of seedlings in which the synthesis of ABA and GA was inhibited collectively and individually by genetic and chemical means. Roots of seedlings treated with Fluridone (an inhibitor of ABA biosynthesis) and Ancymidol (an inhibitor of GA biosynthesis) were characterized by slower growth rates but not significantly different gravicultures as compared to untreated controls. Gravicurvatures of primary roots of d-5 mutants (having undetectable levels of GA) and vp-9 mutants (having undectable levels of ABA) were not significantly different from those of wild-type seedlings. Roots of seedlings in which the biosynthesis of ABA and GA was collectively inhibited were characterized by gravicurvatures not significantly different for those of controls. These results (1) indicate that drastic reductions in the amount of ABA and GA in Z. mays seedlings do not significantly alter root graviresponsiveness, (2) suggest that neither ABA nor GA is necessary for root gravicurvature, and (3) indicate that root gravicurvature is not necessarily proportional to root elongation.

  16. Regulation of the rab17 gene promoter in transgenic Arabidopsis wild-type, ABA-deficient and ABA-insensitive mutants.

    PubMed

    Vilardell, J; Martínez-Zapater, J M; Goday, A; Arenas, C; Pagès, M

    1994-02-01

    The abscisic acid-responsive gene rab17 is induced during maize embryo maturation and in vegetative tissues under water stress conditions. To investigate how ABA is involved in the induction of the rab17 gene, we present here a genetic approach to analyse the transcriptional regulation of the 1.3 kb rab17 promoter fragment in transgenic wild-type Arabidopsis and mutants which are deficient (aba) and insensitive (abi1, abi2 and abi3) to ABA. During seed development the rab17 promoter fragment confers similar temporal and spatial regulation on the reporter gene GUS, both in transgenic wild-type and ABA-deficient and ABA-insensitive mutants. The rab17 promoter was only active in embryo and endosperm during late seed development, although the ABA-deficient embryo mutant showed a reduction in the level of GUS activity. During germination rab17 promoter activity decreases, and GUS activity is not enhanced by water stress in transgenic wild-type and mutant plants. In contrast, transcription of the Arabidopsis endogenous rab gene is stimulated by water stress, both in wild-type and ABA-insensitive mutants. Our data suggest that different molecular mechanisms mediate seed-specific expression and ABA water stress induction of the rab17 gene and indicate strong conservation of the seed-specific regulatory mechanism for rab genes in monocot and dicot plants.

  17. Transcription factor WRKY46 modulates the development of Arabidopsis lateral roots in osmotic/salt stress conditions via regulation of ABA signaling and auxin homeostasis.

    PubMed

    Ding, Zhong Jie; Yan, Jing Ying; Li, Chun Xiao; Li, Gui Xin; Wu, Yun Rong; Zheng, Shao Jian

    2015-10-01

    The development of lateral roots (LR) is known to be severely inhibited by salt or osmotic stress. However, the molecular mechanisms underlying LR development in osmotic/salt stress conditions are poorly understood. Here we show that the gene encoding the WRKY transcription factor WRKY46 (WRKY46) is expressed throughout lateral root primordia (LRP) during early LR development and that expression is subsequently restricted to the stele of the mature LR. In osmotic/salt stress conditions, lack of WRKY46 (in loss-of-function wrky46 mutants) significantly reduces, while overexpression of WRKY46 enhances, LR development. We also show that exogenous auxin largely restores LR development in wrky46 mutants, and that the auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA) inhibits LR development in both wild-type (WT; Col-0) and in a line overexpressing WRKY46 (OV46). Subsequent analysis of abscisic acid (ABA)-related mutants indicated that WRKY46 expression is down-regulated by ABA signaling, and up-regulated by an ABA-independent signal induced by osmotic/salt stress. Next, we show that expression of the DR5:GUS auxin response reporter is reduced in roots of wrky46 mutants, and that both wrky46 mutants and OV46 display altered root levels of free indole-3-acetic acid (IAA) and IAA conjugates. Subsequent RT-qPCR and ChIP-qPCR experiments indicated that WRKY46 directly regulates the expression of ABI4 and of genes regulating auxin conjugation. Finally, analysis of wrky46 abi4 double mutant plants confirms that ABI4 acts downstream of WRKY46. In summary, our results demonstrate that WRKY46 contributes to the feedforward inhibition of osmotic/salt stress-dependent LR inhibition via regulation of ABA signaling and auxin homeostasis.

  18. The site of water stress governs the pattern of ABA synthesis and transport in peanut

    PubMed Central

    Hu, Bo; Cao, Jiajia; Ge, Kui; Li, Ling

    2016-01-01

    Abscisic acid (ABA) is one of the most important phytohormones involved in stress responses in plants. However, knowledge of the effect on ABA distribution and transport of water stress at different sites on the plant is limited. In this study, water stress imposed on peanut leaves or roots by treatment with PEG 6000 is termed “leaf stress” or “root stress”, respectively. Immunoenzyme localization technolony was first used to detect ABA distribution in peanut. Under root stress, ABA biosynthesis and distribution level were all more pronounced in root than in leaf. However, ABA transport and the ability to induce stomatal closure were still better in leaf than in root during root stress; However, ABA biosynthesis initially increased in leaf, then rapidly accumulated in the vascular cambium of leaves and induced stomatal closure under leaf stress; ABA produced in root tissues was also transported to leaf tissues to maintain stomatal closure. The vascular system was involved in the coordination and integration of this complex regulatory mechanism for ABA signal accumulation. Water stress subject to root or leaf results in different of ABA biosynthesis and transport ability that trigger stoma close in peanut. PMID:27694957

  19. Dual Function of NAC072 in ABF3-Mediated ABA-Responsive Gene Regulation in Arabidopsis

    PubMed Central

    Li, Xiaoyun; Li, Xiaoling; Li, Meijuan; Yan, Youcheng; Liu, Xu; Li, Ling

    2016-01-01

    The NAM, ATAF1/2, and CUC2 (NAC) domain proteins play various roles in plant growth and stress responses. Arabidopsis NAC transcription factor NAC072 has been reported as a transcriptional activator in Abscisic acid (ABA)-responsive gene expression. However, the exact function of NAC072 in ABA signaling is still elusive. In this study, we present evidence for the interrelation between NAC072 and ABA-responsive element binding factor 3 (ABF3) that act as a positive regulator of ABA-responsive gene expression in Arabidopsis. The transcript of NAC072 is up-regulated by ABF3 in ABA response, and NAC072 protein interacts with ABF3. Enhanced ABA sensitivity occurs in nac072 mutant plants that overexpressed ABF3. However, overexpression of NAC072 weakened the ABA sensitivity in the abf3 mutant plants, but instead of recovering the ABA sensitivity of abf3. NAC072 and ABF3 cooperate to regulate RD29A expression, but are antagonistic when regulating RD29B expression. Therefore, NAC072 displays a dual function in ABF3-mediated ABA-responsive gene regulation. PMID:27486475

  20. Glycation inhibits trichloroacetic acid (TCA)-induced whey protein precipitation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Four different WPI saccharide conjugates were successfully prepared to test whether glycation could inhibit WPI precipitation induced by trichloroacetic acid (TCA). Conjugates molecular weights after glycation were analyzed with SDS-PAGE. No significant secondary structure change due to glycation wa...

  1. Arabidopsis CPR5 Independently Regulates Seed Germination and Postgermination Arrest of Development through LOX Pathway and ABA Signaling

    PubMed Central

    Yang, Xiang; Wang, Yaqin; Su, Xiaojun; Du, Jinju; Yang, Chengwei

    2011-01-01

    The phytohormone abscisic acid (ABA) and the lipoxygenases (LOXs) pathway play important roles in seed germination and seedling growth and development. Here, we reported on the functional characterization of Arabidopsis CPR5 in the ABA signaling and LOX pathways. The cpr5 mutant was hypersensitive to ABA in the seed germination, cotyledon greening and root growth, whereas transgenic plants overexpressing CPR5 were insensitive. Genetic analysis demonstrated that CPR5 gene may be located downstream of the ABI1 in the ABA signaling pathway. However, the cpr5 mutant showed an ABA independent drought-resistant phenotype. It was also found that the cpr5 mutant was hypersensitive to NDGA and NDGA treatment aggravated the ABA-induced delay in the seed germination and cotyledon greening. Taken together, these results suggest that the CPR5 plays a regulatory role in the regulation of seed germination and early seedling growth through ABA and LOX pathways independently. PMID:21556325

  2. Open Stomata 1 (OST1) is limiting in abscisic acid responses of Arabidopsis guard cells.

    PubMed

    Acharya, Biswa R; Jeon, Byeong Wook; Zhang, Wei; Assmann, Sarah M

    2013-12-01

    Open Stomata 1 (OST1) (SnRK2.6 or SRK2E), a serine/threonine protein kinase, is a positive regulator in abscisic acid (ABA)-mediated stomatal response, but OST1-regulation of K(+) and Ca(2+) currents has not been studied directly in guard cells and it is unknown whether OST1 activity is limiting in ABA-mediated stomatal responses. We employed loss-of-function and gain-of-function approaches to study native ABA responses of Arabidopsis guard cells. We performed stomatal aperture bioassays, patch clamp analyses and reactive oxygen species (ROS) measurements. ABA inhibition of inward K(+) channels and light-induced stomatal opening are reduced in ost1 mutants while transgenic plants overexpressing OST1 show ABA hypersensitivity in these responses. ost1 mutants are insensitive to ABA-induced stomatal closure, regulation of slow anion currents, Ca(2+) -permeable channel activation and ROS production while OST1 overexpressing lines are hypersensitive for these responses, resulting in accelerated stomatal closure in response to ABA. Overexpression of OST1 in planta in the absence of ABA application does not affect basal apertures or ion currents. Moreover, we demonstrate the physical interaction of OST1 with the inward K(+) channel KAT1, the anion channel SLAC1, and the NADPH oxidases AtrbohD and AtrbohF. Our findings support OST1 as a critical limiting component in ABA regulation of stomatal apertures, ion channels and NADPH oxidases in Arabidopsis guard cells.

  3. Inhibition of citrus fungal pathogens by using lactic acid bacteria.

    PubMed

    Gerez, C L; Carbajo, M S; Rollán, G; Torres Leal, G; Font de Valdez, G

    2010-08-01

    The effect of lactic acid bacteria (LAB) on pathogenic fungi was evaluated and the metabolites involved in the antifungal effect were characterized. Penicillium digitatum (INTA 1 to INTA 7) and Geotrichum citri-aurantii (INTA 8) isolated from decayed lemon from commercial packinghouses were treated with imazalil and guazatine to obtain strains resistant to these fungicides. The most resistant strains (4 fungal strains) were selected for evaluating the antifungal activity of 33 LAB strains, among which only 8 strains gave positive results. The antifungal activity of these LAB strains was related to the production of lactic acid, acetic acid, and phenyllactic acid (PLA). A central composite design and the response surface methodology were used to evaluate the inhibitory effect of the organic acids produced by the LAB cultures. The antifungal activity of lactic acid was directly related to its concentration; however, acetic acid and PLA showed a peak of activity at 52.5 and 0.8 mM, respectively, with inhibition rates similar to those obtained with Serenade((R)) (3.0 ppm) imazalil (50 ppm) and guazatine (50 ppm). Beyond the peak of activity, a reduction in effectiveness of both acetic acid and PLA was observed. Comparing the inhibition rate of the organic acids, PLA was about 66- and 600-fold more effective than acetic acid and lactic acid, respectively. This study presents evidences on the antifungal effect of selected LAB strains and their end products. Studies are currently being undertaken to evaluate the effectiveness in preventing postharvest diseases on citrus fruits. PMID:20722936

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

    PubMed

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

    2010-05-01

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

  5. Structural basis for selective activation of ABA receptors

    SciTech Connect

    Peterson, Francis C.; Burgie, E. Sethe; Park, Sang-Youl; Jensen, Davin R.; Weiner, Joshua J.; Bingman, Craig A.; Chang, Chia-En A.; Cutler, Sean R.; Phillips, Jr., George N.; Volkman, Brian F.

    2010-11-01

    Changing environmental conditions and lessening fresh water supplies have sparked intense interest in understanding and manipulating abscisic acid (ABA) signaling, which controls adaptive responses to drought and other abiotic stressors. We recently discovered a selective ABA agonist, pyrabactin, and used it to discover its primary target PYR1, the founding member of the PYR/PYL family of soluble ABA receptors. To understand pyrabactin's selectivity, we have taken a combined structural, chemical and genetic approach. We show that subtle differences between receptor binding pockets control ligand orientation between productive and nonproductive modes. Nonproductive binding occurs without gate closure and prevents receptor activation. Observations in solution show that these orientations are in rapid equilibrium that can be shifted by mutations to control maximal agonist activity. Our results provide a robust framework for the design of new agonists and reveal a new mechanism for agonist selectivity.

  6. Mercaptoimidazolylpropionic acid hydrobromide. Inhibition of tadpole collagenase and related properties.

    PubMed

    Yankeelov, J A; Parish, H A; Spatola, A F

    1978-07-01

    A mercapto analogue of histidine (1), (RS)-2-mercapto-3-(5-imidazolyl)propionic acid (2), was prepared by treatment of (RS)-2-bromo-3-(5-imidazolyl)propionic acid with trithiocarbonate. Decomposition of the resulting intermediate with hydrochloric acid followed by Sephadex G-15 chromatography permitted isolation of 2 as a hydrobromide complex having unusual stability and properties as evidenced by IR and 1H NMR data. The potency of this complex in inhibiting tissue (Rana catesbiana) collagenase was estimated by radial diffusion assay. The amount of 2 required to produce 50% inhibition was 3.8 +/- 1.5 mM compared to 8.7 +/- 2.5 mM for cysteine. Preliminary tests of oxygen susceptibility, mutagenicity, and toxicity suggest that this substance may warrant study as a therapeutic agent for control of collagenase-linked corneal ulcerations. PMID:209189

  7. High relative air humidity and continuous light reduce stomata functionality by affecting the ABA regulation in rose leaves.

    PubMed

    Arve, Louise E; Terfa, Meseret T; Gislerød, Hans Ragnar; Olsen, Jorunn E; Torre, Sissel

    2013-02-01

    Plants developed under high (90%) relative air humidity (RH) have previously been shown to have large, malfunctioning stomata, which results in high water loss during desiccation and reduced dark induced closure. Stomatal movement is to a large extent regulated by abscisic acid (ABA). It has therefore been proposed that low ABA levels contribute to the development of malfunctioning stomata. In this study, we investigated the regulation of ABA content in rose leaves, through hormone analysis and β-glucosidase quantification. Compared with high RH, rose plants developed in moderate RH (60%) and 20 h photoperiod contained higher levels of ABA and β-glucosidase activity. Also, the amount of ABA increased during darkness simultaneously as the ABA-glucose ester (GE) levels decreased. In contrast, plants developed under high RH with 20 h photoperiod showed no increase in ABA levels during darkness, and had low β-glucosidase activity converting ABA-GE to ABA. Continuous lighting (24 h) resulted in low levels of β-glucosidase activity irrespective of RH, indicating that a dark period is essential to activate β-glucosidase. Our results provide new insight into the regulation of ABA under different humidities and photoperiods, and clearly show that β-glucosidase is a key enzyme regulating the ABA pool in rose plants. PMID:22812416

  8. Theobromine Inhibits Uric Acid Crystallization. A Potential Application in the Treatment of Uric Acid Nephrolithiasis

    PubMed Central

    Grases, Felix; Rodriguez, Adrian; Costa-Bauza, Antonia

    2014-01-01

    Purpose To assess the capacity of methylxanthines (caffeine, theophylline, theobromine and paraxanthine) to inhibit uric acid crystallization, and to evaluate their potential application in the treatment of uric acid nephrolithiasis. Materials and Methods The ability of methylxathines to inhibit uric acid nucleation was assayed turbidimetrically. Crystal morphology and its modification due to the effect of theobromine were evaluated by scanning electron microscopy (SEM). The ability of theobromine to inhibit uric acid crystal growth on calculi fragments resulting from extracorporeal shock wave lithotripsy (ESWL) was evaluated using a flow system. Results The turbidimetric assay showed that among the studied methylxanthines, theobromine could markedly inhibit uric acid nucleation. SEM images showed that the presence of theobromine resulted in thinner uric acid crystals. Furthermore, in a flow system theobromine blocked the regrowth of post-ESWL uric acid calculi fragments. Conclusions Theobromine, a natural dimethylxanthine present in high amounts in cocoa, acts as an inhibitor of nucleation and crystal growth of uric acid. Therefore, theobromine may be clinically useful in the treatment of uric acid nephrolithiasis. PMID:25333633

  9. Chlorogenic Acid Inhibits Human Platelet Activation and Thrombus Formation

    PubMed Central

    Fuentes, Eduardo; Caballero, Julio; Alarcón, Marcelo; Rojas, Armando; Palomo, Iván

    2014-01-01

    Background Chlorogenic acid is a potent phenolic antioxidant. However, its effect on platelet aggregation, a critical factor in arterial thrombosis, remains unclear. Consequently, chlorogenic acid-action mechanisms in preventing platelet activation and thrombus formation were examined. Methods and Results Chlorogenic acid in a dose-dependent manner (0.1 to 1 mmol/L) inhibited platelet secretion and aggregation induced by ADP, collagen, arachidonic acid and TRAP-6, and diminished platelet firm adhesion/aggregation and platelet-leukocyte interactions under flow conditions. At these concentrations chlorogenic acid significantly decreased platelet inflammatory mediators (sP-selectin, sCD40L, CCL5 and IL-1β) and increased intraplatelet cAMP levels/PKA activation. Interestingly, SQ22536 (an adenylate cyclase inhibitor) and ZM241385 (a potent A2A receptor antagonist) attenuated the antiplatelet effect of chlorogenic acid. Chlorogenic acid is compatible to the active site of the adenosine A2A receptor as revealed through molecular modeling. In addition, chlorogenic acid had a significantly lower effect on mouse bleeding time when compared to the same dose of aspirin. Conclusions Antiplatelet and antithrombotic effects of chlorogenic acid are associated with the A2A receptor/adenylate cyclase/cAMP/PKA signaling pathway. PMID:24598787

  10. Inhibition of bacterial activity in acid mine drainage

    NASA Astrophysics Data System (ADS)

    Singh, Gurdeep; Bhatnagar, Miss Mridula

    1988-12-01

    Acid mine drainage water give rise to rapid growth and activity of an iron- and sulphur- oxidizing bacterium Thiobacillus ferrooxidians which greatly accelerate acid producing reactions by oxidation of pyrite material associated with coal and adjoining strata. The role of this bacterium in production of acid mine drainage is described. This study presents the data which demonstrate the inhibitory effect of certain organic acids, sodium benzoate, sodium lauryl sulphate, quarternary ammonium compounds on the growth of the acidophilic aerobic autotroph Thiobacillus ferrooxidians. In each experiment, 10 milli-litres of laboratory developed culture of Thiobacillus ferrooxidians was added to 250 milli-litres Erlenmeyer flask containing 90 milli-litres of 9-k media supplemented with FeSO4 7H2O and organic compounds at various concentrations. Control experiments were also carried out. The treated and untreated (control) samples analysed at various time intervals for Ferrous Iron and pH levels. Results from this investigation showed that some organic acids, sodium benzoate, sodium lauryl sulphate and quarternary ammonium compounds at low concentration (10-2 M, 10-50 ppm concentration levels) are effective bactericides and able to inhibit and reduce the Ferrous Iron oxidation and acidity formation by inhibiting the growth of Thiobacillus ferrooxidians is also discussed and presented

  11. Seizure control by decanoic acid through direct AMPA receptor inhibition.

    PubMed

    Chang, Pishan; Augustin, Katrin; Boddum, Kim; Williams, Sophie; Sun, Min; Terschak, John A; Hardege, Jörg D; Chen, Philip E; Walker, Matthew C; Williams, Robin S B

    2016-02-01

    The medium chain triglyceride ketogenic diet is an established treatment for drug-resistant epilepsy that increases plasma levels of decanoic acid and ketones. Recently, decanoic acid has been shown to provide seizure control in vivo, yet its mechanism of action remains unclear. Here we show that decanoic acid, but not the ketones β-hydroxybutryate or acetone, shows antiseizure activity in two acute ex vivo rat hippocampal slice models of epileptiform activity. To search for a mechanism of decanoic acid, we show it has a strong inhibitory effect on excitatory, but not inhibitory, neurotransmission in hippocampal slices. Using heterologous expression of excitatory ionotropic glutamate receptor AMPA subunits in Xenopus oocytes, we show that this effect is through direct AMPA receptor inhibition, a target shared by a recently introduced epilepsy treatment perampanel. Decanoic acid acts as a non-competitive antagonist at therapeutically relevant concentrations, in a voltage- and subunit-dependent manner, and this is sufficient to explain its antiseizure effects. This inhibitory effect is likely to be caused by binding to sites on the M3 helix of the AMPA-GluA2 transmembrane domain; independent from the binding site of perampanel. Together our results indicate that the direct inhibition of excitatory neurotransmission by decanoic acid in the brain contributes to the anti-convulsant effect of the medium chain triglyceride ketogenic diet. PMID:26608744

  12. Abscisic acid signaling through cyclic ADP-ribose in hydroid regeneration.

    PubMed

    Puce, Stefania; Basile, Giovanna; Bavestrello, Giorgio; Bruzzone, Santina; Cerrano, Carlo; Giovine, Marco; Arillo, Attilio; Zocchi, Elena

    2004-09-17

    Cyclic ADP-ribose (cADPR) is an intracellular calcium (Ca(2+)(i)) mobilizer involved in fundamental cell functions from protists to higher plants and mammals. Biochemical similarities between the drought-signaling cascade in plants and the temperature-sensing pathway in marine sponges suggest an ancient evolutionary origin of a signaling cascade involving the phytohormone abscisic acid (ABA), cADPR, and Ca(2+)(i). In Eudendrium racemosum (Hydrozoa, Cnidaria), exogenously added ABA stimulated ADP-ribosyl cyclase activity via a protein kinase A (PKA)-mediated phosphorylation and increased regeneration in the dark to levels observed under light conditions. Light stimulated endogenous ABA synthesis, which was conversely inhibited by the inhibitor of plant ABA synthesis Fluridone. The signal cascade of light-induced regeneration uncovered in E. racemosum: light --> increasing ABA --> PKA --> cyclase activation --> increasing [cADPR](i) --> increasing [Ca(2+)](i) --> regeneration is the first report of a complete signaling pathway in Eumetazoa involving a phytohormone.

  13. Chemical genetics reveals negative regulation of abscisic acid signaling by a plant immune response pathway.

    PubMed

    Kim, Tae-Houn; Hauser, Felix; Ha, Tracy; Xue, Shaowu; Böhmer, Maik; Nishimura, Noriyuki; Munemasa, Shintaro; Hubbard, Katharine; Peine, Nora; Lee, Byeong-Ha; Lee, Stephen; Robert, Nadia; Parker, Jane E; Schroeder, Julian I

    2011-06-01

    Coordinated regulation of protection mechanisms against environmental abiotic stress and pathogen attack is essential for plant adaptation and survival. Initial abiotic stress can interfere with disease-resistance signaling [1-6]. Conversely, initial plant immune signaling may interrupt subsequent abscisic acid (ABA) signal transduction [7, 8]. However, the processes involved in this crosstalk between these signaling networks have not been determined. By screening a 9600-compound chemical library, we identified a small molecule [5-(3,4-dichlorophenyl)furan-2-yl]-piperidine-1-ylmethanethione (DFPM) that rapidly downregulates ABA-dependent gene expression and also inhibits ABA-induced stomatal closure. Transcriptome analyses show that DFPM also stimulates expression of plant defense-related genes. Major early regulators of pathogen-resistance responses, including EDS1, PAD4, RAR1, and SGT1b, are required for DFPM-and notably also for Pseudomonas-interference with ABA signal transduction, whereas salicylic acid, EDS16, and NPR1 are not necessary. Although DFPM does not interfere with early ABA perception by PYR/RCAR receptors or ABA activation of SnRK2 kinases, it disrupts cytosolic Ca(2+) signaling and downstream anion channel activation in a PAD4-dependent manner. Our findings provide evidence that activation of EDS1/PAD4-dependent plant immune responses rapidly disrupts ABA signal transduction and that this occurs at the level of Ca(2+) signaling, illuminating how the initial biotic stress pathway interferes with ABA signaling.

  14. 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

  15. Acid inhibition and infections outside the gastrointestinal tract.

    PubMed

    Vakil, Nimish

    2009-03-01

    Acid-inhibitory agents can alter the flora of the stomach, and epidemiologic studies suggest an association between the use of these agents and the development of pneumonia. Microbiologic studies suggest that a causal association may be biologically plausible because gastric colonization with organisms can occur in patients taking acid suppressive agents. In mechanically ventilated patients, colonization of the oropharynx and stomach may predispose to Gram-negative pneumonias. Despite the associations between acid inhibitor use and pneumonia shown in some studies, the data on community-acquired pneumonias are not conclusive. In clinical practice, prudence would dictate that the need for acid inhibition with histamine-2 receptor antagonists or proton pump inhibitors should be carefully considered in patients who are at risk for pneumonias (elderly patients with chronic lung disease who are on immunosuppressive drugs or corticosteroids and patients with recurrent lung infections requiring frequent antibiotic therapy).

  16. Inhibition studies of soybean (Glycine max) urease with heavy metals, sodium salts of mineral acids, boric acid, and boronic acids.

    PubMed

    Kumar, Sandeep; Kayastha, Arvind M

    2010-10-01

    Various inhibitors were tested for their inhibitory effects on soybean urease. The K(i) values for boric acid, 4-bromophenylboronic acid, butylboronic acid, and phenylboronic acid were 0.20 +/- 0.05 mM, 0.22 +/- 0.04 mM, 1.50 +/- 0.10 mM, and 2.00 +/- 0.11 mM, respectively. The inhibition was competitive type with boric acid and boronic acids. Heavy metal ions including Ag(+), Hg(2+), and Cu(2+) showed strong inhibition on soybean urease, with the silver ion being a potent inhibitor (IC(50) = 2.3 x 10(-8) mM). Time-dependent inhibition studies exhibited biphasic kinetics with all heavy metal ions. Furthermore, inhibition studies with sodium salts of mineral acids (NaF, NaCl, NaNO(3), and Na(2)SO(4)) showed that only F(-) inhibited soybean urease significantly (IC(50) = 2.9 mM). Competitive type of inhibition was observed for this anion with a K(i) value of 1.30 mM.

  17. The Citrus ABA signalosome: identification and transcriptional regulation during sweet orange fruit ripening and leaf dehydration

    PubMed Central

    Rodrigo, María J.

    2012-01-01

    The abscisic acid (ABA) signalling core in plants include the cytosolic ABA receptors (PYR/PYL/RCARs), the clade-A type 2C protein phosphatases (PP2CAs), and the subclass III SNF1-related protein kinases 2 (SnRK2s). The aim of this work was to identify these ABA perception system components in sweet orange and to determine the influence of endogenous ABA on their transcriptional regulation during fruit development and ripening, taking advantage of the comparative analysis between a wild-type and a fruit-specific ABA-deficient mutant. Transcriptional changes in the ABA signalosome during leaf dehydration were also studied. Six PYR/PYL/RCAR, five PP2CA, and two subclass III SnRK2 genes, homologous to those of Arabidopsis, were identified in the Citrus genome. The high degree of homology and conserved motifs for protein folding and for functional activity suggested that these Citrus proteins are bona fide core elements of ABA perception in orange. Opposite expression patterns of CsPYL4 and CsPYL5 and ABA accumulation were found during ripening, although there were few differences between varieties. In contrast, changes in expression of CsPP2CA genes during ripening paralleled those of ABA content and agreeed with the relevant differences between wild-type and mutant fruit transcript accumulation. CsSnRK2 gene expression continuously decreased with ripening and no remarkable differences were found between cultivars. Overall, dehydration had a minor effect on CsPYR/PYL/RCAR and CsSnRK2 expression in vegetative tissue, whereas CsABI1, CsAHG1, and CsAHG3 were highly induced by water stress. The global results suggest that responsiveness to ABA changes during citrus fruit ripening, and leaf dehydration was higher in the CsPP2CA gene negative regulators than in the other ABA signalosome components. PMID:22888124

  18. The Citrus ABA signalosome: identification and transcriptional regulation during sweet orange fruit ripening and leaf dehydration.

    PubMed

    Romero, Paco; Lafuente, María T; Rodrigo, María J

    2012-08-01

    The abscisic acid (ABA) signalling core in plants include the cytosolic ABA receptors (PYR/PYL/RCARs), the clade-A type 2C protein phosphatases (PP2CAs), and the subclass III SNF1-related protein kinases 2 (SnRK2s). The aim of this work was to identify these ABA perception system components in sweet orange and to determine the influence of endogenous ABA on their transcriptional regulation during fruit development and ripening, taking advantage of the comparative analysis between a wild-type and a fruit-specific ABA-deficient mutant. Transcriptional changes in the ABA signalosome during leaf dehydration were also studied. Six PYR/PYL/RCAR, five PP2CA, and two subclass III SnRK2 genes, homologous to those of Arabidopsis, were identified in the Citrus genome. The high degree of homology and conserved motifs for protein folding and for functional activity suggested that these Citrus proteins are bona fide core elements of ABA perception in orange. Opposite expression patterns of CsPYL4 and CsPYL5 and ABA accumulation were found during ripening, although there were few differences between varieties. In contrast, changes in expression of CsPP2CA genes during ripening paralleled those of ABA content and agreeed with the relevant differences between wild-type and mutant fruit transcript accumulation. CsSnRK2 gene expression continuously decreased with ripening and no remarkable differences were found between cultivars. Overall, dehydration had a minor effect on CsPYR/PYL/RCAR and CsSnRK2 expression in vegetative tissue, whereas CsABI1, CsAHG1, and CsAHG3 were highly induced by water stress. The global results suggest that responsiveness to ABA changes during citrus fruit ripening, and leaf dehydration was higher in the CsPP2CA gene negative regulators than in the other ABA signalosome components. PMID:22888124

  19. The Role of MAPK Modules and ABA during Abiotic Stress Signaling.

    PubMed

    de Zelicourt, Axel; Colcombet, Jean; Hirt, Heribert

    2016-08-01

    To respond to abiotic stresses, plants have developed specific mechanisms that allow them to rapidly perceive and respond to environmental changes. The phytohormone abscisic acid (ABA) was shown to be a pivotal regulator of abiotic stress responses in plants, triggering major changes in plant physiology. The ABA core signaling pathway largely relies on the activation of SnRK2 kinases to mediate several rapid responses, including gene regulation, stomatal closure, and plant growth modulation. Mitogen-activated protein kinases (MAPKs) have also been implicated in ABA signaling, but an entire ABA-activated MAPK module was uncovered only recently. In this review, we discuss the evidence for a role of MAPK modules in the context of different plant ABA signaling pathways. PMID:27143288

  20. Inhibition of cardiac mitochondrial respiration by salicylic acid and acetylsalicylate.

    PubMed

    Nulton-Persson, Amy C; Szweda, Luke I; Sadek, Hesham A

    2004-11-01

    Acetylsalicylate, the active ingredient in aspirin, has been shown to be beneficial in the treatment and prevention of cardiovascular disease. Because of the increasing frequency with which salicylates are used, it is important to more fully characterize extra- and intracellular processes that are altered by these compounds. Evidence is provided that treatment of isolated cardiac mitochondria with salicylic acid and to a lesser extent acetylsalicylate resulted in an increase in the rate of uncoupled respiration. In contrast, both compounds inhibited ADP-dependent NADH-linked (state 3) respiration to similar degrees. Under the conditions of our experiments, loss in state 3 respiration resulted from inhibition of the Krebs cycle enzyme alpha-ketoglutarate dehydrogenase (KGDH). Kinetic analysis indicates that salicylic acid acts as a competitive inhibitor at the alpha-ketoglutarate binding site. In contrast, acetylsalicylate inhibited the enzyme in a noncompetitive fashion consistent with interaction with the alpha-ketoglutarate binding site followed by enzyme-catalyzed acetylation. The effects of salicylic acid and acetylsalicylate on cardiac mitochondrial function may contribute to the known cardioprotective effects of therapeutic doses of aspirin, as well as to the toxicity associated with salicylate overdose.

  1. Cinnamic acid increases lignin production and inhibits soybean root growth.

    PubMed

    Salvador, Victor Hugo; Lima, Rogério Barbosa; dos Santos, Wanderley Dantas; Soares, Anderson Ricardo; Böhm, Paulo Alfredo Feitoza; Marchiosi, Rogério; Ferrarese, Maria de Lourdes Lucio; Ferrarese-Filho, Osvaldo

    2013-01-01

    Cinnamic acid is a known allelochemical that affects seed germination and plant root growth and therefore influences several metabolic processes. In the present work, we evaluated its effects on growth, indole-3-acetic acid (IAA) oxidase and cinnamate 4-hydroxylase (C4H) activities and lignin monomer composition in soybean (Glycine max) roots. The results revealed that exogenously applied cinnamic acid inhibited root growth and increased IAA oxidase and C4H activities. The allelochemical increased the total lignin content, thus altering the sum and ratios of the p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) lignin monomers. When applied alone or with cinnamic acid, piperonylic acid (PIP, a quasi-irreversible inhibitor of C4H) reduced C4H activity, lignin and the H, G, S monomer content compared to the cinnamic acid treatment. Taken together, these results indicate that exogenously applied cinnamic acid can be channeled into the phenylpropanoid pathway via the C4H reaction, resulting in an increase in H lignin. In conjunction with enhanced IAA oxidase activity, these metabolic responses lead to the stiffening of the cell wall and are followed by a reduction in soybean root growth.

  2. Cinnamic acid increases lignin production and inhibits soybean root growth.

    PubMed

    Salvador, Victor Hugo; Lima, Rogério Barbosa; dos Santos, Wanderley Dantas; Soares, Anderson Ricardo; Böhm, Paulo Alfredo Feitoza; Marchiosi, Rogério; Ferrarese, Maria de Lourdes Lucio; Ferrarese-Filho, Osvaldo

    2013-01-01

    Cinnamic acid is a known allelochemical that affects seed germination and plant root growth and therefore influences several metabolic processes. In the present work, we evaluated its effects on growth, indole-3-acetic acid (IAA) oxidase and cinnamate 4-hydroxylase (C4H) activities and lignin monomer composition in soybean (Glycine max) roots. The results revealed that exogenously applied cinnamic acid inhibited root growth and increased IAA oxidase and C4H activities. The allelochemical increased the total lignin content, thus altering the sum and ratios of the p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) lignin monomers. When applied alone or with cinnamic acid, piperonylic acid (PIP, a quasi-irreversible inhibitor of C4H) reduced C4H activity, lignin and the H, G, S monomer content compared to the cinnamic acid treatment. Taken together, these results indicate that exogenously applied cinnamic acid can be channeled into the phenylpropanoid pathway via the C4H reaction, resulting in an increase in H lignin. In conjunction with enhanced IAA oxidase activity, these metabolic responses lead to the stiffening of the cell wall and are followed by a reduction in soybean root growth. PMID:23922685

  3. Contribution of cinnamic acid analogues in rosmarinic acid to inhibition of snake venom induced hemorrhage.

    PubMed

    Aung, Hnin Thanda; Furukawa, Tadashi; Nikai, Toshiaki; Niwa, Masatake; Takaya, Yoshiaki

    2011-04-01

    In our previous paper, we reported that rosmarinic acid (1) of Argusia argentea could neutralize snake venom induced hemorrhagic action. Rosmarinic acid (1) consists of two phenylpropanoids: caffeic acid (2) and 3-(3,4-dihydroxyphenyl)lactic acid (3). In this study, we investigated the structural requirements necessary for inhibition of snake venom activity through the use of compounds, which are structurally related to rosmarinic acid (1). By examining anti-hemorrhagic activity of cinnamic acid analogs against Protobothrops flavoviridis (Habu) venom, it was revealed that the presence of the E-enoic acid moiety (-CH=CH-COOH) was critical. Furthermore, among the compound tested, it was concluded that rosmarinic acid (1) (IC(50) 0.15 μM) was the most potent inhibitor against the venom.

  4. ABA in bryophytes: how a universal growth regulator in life became a plant hormone?

    PubMed

    Takezawa, Daisuke; Komatsu, Kenji; Sakata, Yoichi

    2011-07-01

    Abscisic acid (ABA) is not a plant-specific compound but one found in organisms across kingdoms from bacteria to animals, suggesting that it is a ubiquitous and versatile substance that can modulate physiological functions of various organisms. Recent studies have shown that plants developed an elegant system for ABA sensing and early signal transduction mechanisms to modulate responses to environmental stresses for survival in terrestrial conditions. ABA-induced increase in stress tolerance has been reported not only in vascular plants but also in non-vascular bryophytes. Since bryophytes are the key group of organisms in the context of plant evolution, clarification of their ABA-dependent processes is important for understanding evolutionary adaptation of land plants. Molecular approaches using Physcomitrella patens have revealed that ABA plays a role in dehydration stress tolerance in mosses, which comprise a major group of bryophytes. Furthermore, we recently reported that signaling machinery for ABA responses is also conserved in liverworts, representing the most basal members of extant land plant lineage. Conservation of the mechanism for ABA sensing and responses in angiosperms and basal land plants suggests that acquisition of this mechanism for stress tolerance in vegetative tissues was one of the critical evolutionary events for adaptation to the land. This review describes the role of ABA in basal land plants as well as non-land plant organisms and further elaborates on recent progress in molecular studies of model bryophytes by comparative and functional genomic approaches.

  5. Overexpression of the Artemisia Orthologue of ABA Receptor, AaPYL9, Enhances ABA Sensitivity and Improves Artemisinin Content in Artemisia annua L

    PubMed Central

    Zhang, Fangyuan; Lu, Xu; Lv, Zongyou; Zhang, Ling; Zhu, Mengmeng; Jiang, Weiming; Wang, Guofeng; Sun, Xiaofen; Tang, Kexuan

    2013-01-01

    The phytohormone abscisic acid (ABA) plays an important role in plant development and environmental stress response. In this study, we cloned an ABA receptor orthologue, AaPYL9, from Artemisia annua L. AaPYL9 is expressed highly in leaf and flower. AaPYL9 protein can be localized in both nucleus and cytoplasm. Yeast two-hybrid assay shows AaPYL9 can specifically interact with AtABI1 but not with AtABI2, AtHAB1 or AtHAB2. ABA can enhance the interaction between AaPYL9 and AtABI1 while AaPYL9-89 Pro→Ser and AaPYL9-116 His→Ala point mutations abolishes the interaction. BiFC assay shows that AaPYL9 interacts with AtABI1 in nucleus in planta. Transgenic Arabidopsis plants over-expressing AaPYL9 are more sensitive to ABA in the seed germination and primary root growth than wild type. Consistent with this, ABA report genes have higher expression in AaPYL9 overexpressing plants compared to wild type after ABA treatment. Moreover, overexpression of AaPYL9 in A. annua increases not only drought tolerance, but also artemisinin content after ABA treatment, with significant enhancement of the expression of key genes in artemisinin biosynthesis. This study provides a way to develop A. annua with high-yielding artemisinin and high drought resistance. PMID:23437216

  6. Feedback Regulation of ABA Signaling and Biosynthesis by a bZIP Transcription Factor Targets Drought-Resistance-Related Genes.

    PubMed

    Zong, Wei; Tang, Ning; Yang, Jun; Peng, Lei; Ma, Siqi; Xu, Yan; Li, Guoliang; Xiong, Lizhong

    2016-08-01

    The OsbZIP23 transcription factor has been characterized for its essential role in drought resistance in rice (Oryza sativa), but the mechanism is unknown. In this study, we first investigated the transcriptional activation of OsbZIP23. A homolog of SnRK2 protein kinase (SAPK2) was found to interact with and phosphorylate OsbZIP23 for its transcriptional activation. SAPK2 also interacted with OsPP2C49, an ABI1 homolog, which deactivated the SAPK2 to inhibit the transcriptional activation activity of OsbZIP23. Next, we performed genome-wide identification of OsbZIP23 targets by immunoprecipitation sequencing and RNA sequencing analyses in the OsbZIP23-overexpression, osbzip23 mutant, and wild-type rice under normal and drought stress conditions. OsbZIP23 directly regulates a large number of reported genes that function in stress response, hormone signaling, and developmental processes. Among these targets, we found that OsbZIP23 could positively regulate OsPP2C49, and overexpression of OsPP2C49 in rice resulted in significantly decreased sensitivity of the abscisic acid (ABA) response and rapid dehydration. Moreover, OsNCED4 (9-cis-epoxycarotenoid dioxygenase4), a key gene in ABA biosynthesis, was also positively regulated by OsbZIP23. Together, our results suggest that OsbZIP23 acts as a central regulator in ABA signaling and biosynthesis, and drought resistance in rice. PMID:27325665

  7. Cadmium inhibits acid secretion in stimulated frog gastric mucosa

    SciTech Connect

    Gerbino, Andrea; Debellis, Lucantonio; Caroppo, Rosa; Curci, Silvana; Colella, Matilde

    2010-06-01

    Cadmium, a toxic environmental pollutant, affects the function of different organs such as lungs, liver and kidney. Less is known about its toxic effects on the gastric mucosa. The aim of this study was to investigate the mechanisms by which cadmium impacts on the physiology of gastric mucosa. To this end, intact amphibian mucosae were mounted in Ussing chambers and the rate of acid secretion, short circuit current (I{sub sc}), transepithelial potential (V{sub t}) and resistance (R{sub t}) were recorded in the continuous presence of cadmium. Addition of cadmium (20 {mu}M to 1 mM) on the serosal but not luminal side of the mucosae resulted in inhibition of acid secretion and increase in NPPB-sensitive, chloride-dependent short circuit current. Remarkably, cadmium exerted its effects only on histamine-stimulated tissues. Experiments with TPEN, a cell-permeant chelator for heavy metals, showed that cadmium acts from the intracellular side of the acid secreting cells. Furthermore, cadmium-induced inhibition of acid secretion and increase in I{sub sc} cannot be explained by an action on: 1) H{sub 2} histamine receptor, 2) Ca{sup 2+} signalling 3) adenylyl cyclase or 4) carbonic anhydrase. Conversely, cadmium was ineffective in the presence of the H{sup +}/K{sup +}-ATPase blocker omeprazole suggesting that the two compounds likely act on the same target. Our findings suggest that cadmium affects the functionality of histamine-stimulated gastric mucosa by inhibiting the H{sup +}/K{sup +}-ATPase from the intracellular side. These data shed new light on the toxic effect of this dangerous environmental pollutant and may result in new avenues for therapeutic intervention in acute and chronic intoxication.

  8. The Arabidopsis ZINC FINGER PROTEIN3 Interferes with Abscisic Acid and Light Signaling in Seed Germination and Plant Development1[C][W][OPEN

    PubMed Central

    Joseph, Mary Prathiba; Papdi, Csaba; Kozma-Bognár, László; Nagy, István; López-Carbonell, Marta; Rigó, Gábor; Koncz, Csaba; Szabados, László

    2014-01-01

    Seed germination is controlled by environmental signals, including light and endogenous phytohormones. Abscisic acid (ABA) inhibits, whereas gibberellin promotes, germination and early seedling development, respectively. Here, we report that ZFP3, a nuclear C2H2 zinc finger protein, acts as a negative regulator of ABA suppression of seed germination in Arabidopsis (Arabidopsis thaliana). Accordingly, regulated overexpression of ZFP3 and the closely related ZFP1, ZFP4, ZFP6, and ZFP7 zinc finger factors confers ABA insensitivity to seed germination, while the zfp3 zfp4 double mutant displays enhanced ABA susceptibility. Reduced expression of several ABA-induced genes, such as RESPONSIVE TO ABSCISIC ACID18 and transcription factor ABSCISIC ACID-INSENSITIVE4 (ABI4), in ZFP3 overexpression seedlings suggests that ZFP3 negatively regulates ABA signaling. Analysis of ZFP3 overexpression plants revealed multiple phenotypic alterations, such as semidwarf growth habit, defects in fertility, and enhanced sensitivity of hypocotyl elongation to red but not to far-red or blue light. Analysis of genetic interactions with phytochrome and abi mutants indicates that ZFP3 enhances red light signaling by photoreceptors other than phytochrome A and additively increases ABA insensitivity conferred by the abi2, abi4, and abi5 mutations. These data support the conclusion that ZFP3 and the related ZFP subfamily of zinc finger factors regulate light and ABA responses during germination and early seedling development. PMID:24808098

  9. Towards the Identification of New Genes Involved in ABA-Dependent Abiotic Stresses Using Arabidopsis Suppressor Mutants of abh1 Hypersensitivity to ABA during Seed Germination

    PubMed Central

    Daszkowska-Golec, Agata; Chorazy, Edyta; Maluszynski, Miroslaw; Szarejko, Iwona

    2013-01-01

    Abscisic acid plays a pivotal role in the abiotic stress response in plants. Although great progress has been achieved explaining the complexity of the stress and ABA signaling cascade, there are still many questions to answer. Mutants are a valuable tool in the identification of new genes or new alleles of already known genes and in elucidating their role in signaling pathways. We applied a suppressor mutation approach in order to find new components of ABA and abiotic stress signaling in Arabidopsis. Using the abh1 (ABA hypersensitive 1) insertional mutant as a parental line for EMS mutagenesis, we selected several mutants with suppressed hypersensitivity to ABA during seed germination. Here, we present the response to ABA and a wide range of abiotic stresses during the seed germination and young seedling development of two suppressor mutants—soa2 (suppressor of abh1 hypersensitivity to ABA 2) and soa3 (suppressor of abh1 hypersensitivity to ABA 3). Generally, both mutants displayed a suppression of the hypersensitivity of abh1 to ABA, NaCl and mannitol during germination. Both mutants showed a higher level of tolerance than Columbia-0 (Col-0—the parental line of abh1) in high concentrations of glucose. Additionally, soa2 exhibited better root growth than Col-0 in the presence of high ABA concentrations. soa2 and soa3 were drought tolerant and both had about 50% fewer stomata per mm2 than the wild-type but the same number as their parental line—abh1. Taking into account that suppressor mutants had the same genetic background as their parental line—abh1, it was necessary to backcross abh1 with Landsberg erecta four times for the map-based cloning approach. Mapping populations, derived from the cross of abh1 in the Landsberg erecta background with each suppressor mutant, were created. Map based cloning in order to identify the suppressor genes is in progress. PMID:23807502

  10. Inhibition of Aluminum Oxyhydroxide Precipitation with Citric Acid

    SciTech Connect

    Dabbs, Daniel M.; Ramachandran, Usha; Lu, Sang; Liu, Jun; Wang, Li Q.; Aksay, Ilhan A.

    2005-12-06

    Citric acid has been shown to act as an agent for increasing the solubility of aluminum oxyhydroxides in aqueous solutions of high (>2.47 mol/mol) hydroxide-to-aluminum ratios. Conversely, citric acid also colloidally stabilizes particles in aqueous suspensions of aluminum-containing particles. Solutions of aluminum chloride, with and without citric acid added, were titrated with NaO(aq). The presence and size of particles were determined using quasi-elastic light scattering. In solutions that contained no citric acid, particles formed instantaneously when NaOH(aq) was added but these were observed to rapidly diminish in size, disappearing at OH/Al ratios below 2.5 mol/mol. When the OH/Al ratio was raised beyond 2.5 by addingmoreNaOH(aq), suspensions of colloidally stable particles formed. Large polycations containing 13 aluminum atoms were detected by 27Al solution NMR in citric-acid-free solutions with OH/Al ratios slightly lower than 2.5. In comparison, adding citric acid to solutions of aluminum chloride inhibited the formation of large aluminum-containing polycations. The absence of the polycations prevents or retards the subsequent formation of particles, indicating that the polycations, when present, act as seeds to the formation of new particles. Particles did not form in solutions with a citric acid/aluminum ratio of 0.8 until sufficient NaOH(aq) was added to raise the OH/Al ratio to 3.29. By comparison, lower amounts of citric acid did not prevent particles from forming but did retard the rate of growth.

  11. The ABI4-Induced Arabidopsis ANAC060 Transcription Factor Attenuates ABA Signaling and Renders Seedlings Sugar Insensitive when Present in the Nucleus

    PubMed Central

    Shi, Xiaoliang; Yu, Bo; Zhou, Yan; Chen, Suli; Wang, Yufeng; Peng, Yu; Meyer, Rhonda C.; Smeekens, Sjef C.; Teng, Sheng

    2014-01-01

    Seedling establishment is inhibited on media containing high levels (∼6%) of glucose or fructose. Genetic loci that overcome the inhibition of seedling growth on high sugar have been identified using natural variation analysis and mutant selection, providing insight into sugar signaling pathways. In this study, a quantitative trait locus (QTL) analysis was performed for seedling sensitivity to high sugar in a Col/C24 F2 population of Arabidopsis thaliana. A glucose and fructose-sensing QTL, GSQ11, was mapped through selective genotyping and confirmed in near-isogenic lines in both Col and C24 backgrounds. Allelism tests and transgenic complementation showed that GSQ11 lies within the ANAC060 gene. The Col ANAC060 allele confers sugar insensitivity and was dominant over the sugar-sensitive C24 allele. Genomic and mRNA analyses showed that a single-nucleotide polymorphism (SNP) in Col ANAC060 affects the splicing patterns of ANAC060 such that 20 additional nucleotides are present in the mRNA. The insertion created a stop codon, resulting in a truncated ANAC60 protein lacking the transmembrane domain (TMD) that is present in the C24 ANAC060 protein. The absence of the TMD results in the nuclear localization of ANAC060. The short version of the ANAC060 protein is found in ∼12% of natural Arabidopsis accessions. Glucose induces GSQ11/ANAC060 expression in a process that requires abscisic acid (ABA) signaling. Chromatin immunoprecipitation-qPCR and transient expression analysis showed that ABI4 directly binds to the GSQ11/ANAC060 promoter to activate transcription. Interestingly, Col ANAC060 reduced ABA sensitivity and Glc-induced ABA accumulation, and ABI4 expression was also reduced in Col ANAC060 lines. Thus, the sugar-ABA signaling cascade induces ANAC060 expression, but the truncated Col ANAC060 protein attenuates ABA induction and ABA signaling. This negative feedback from nuclear ANAC060 on ABA signaling results in sugar insensitivity. PMID:24625790

  12. Inhibition of Escherichia coli growth and diaminopimelic acid epimerase by 3-chlorodiaminopimelic acid.

    PubMed Central

    Baumann, R J; Bohme, E H; Wiseman, J S; Vaal, M; Nichols, J S

    1988-01-01

    The diaminopimelic acid (DAP) analog, 3-chloro-DAP, was synthesized and tested as the racemic acid for antibacterial activity and for inhibition of DAP epimerase. 3-Chloro-DAP was a potent inhibitor of DAP epimerase purified from Escherichia coli (Ki = 200 nM), and it is argued that 3-chloro-DAP is converted to a tight-binding transition state analog at the active site of this enzyme. Furthermore, 3-chloro-DAP inhibited growth of two E. coli mutants. In one of the mutants known for supersusceptibility to beta-lactams, inhibition was not seen until the mid-log phase of growth, while in the other mutant, a DAP auxotroph, inhibition occurred much earlier. Growth inhibition was reversed by DAP in both strains. In the auxotroph, the reversal was specific for meso-DAP, indicating that DAP epimerase was the target for 3-chloro-DAP. Thus we suggest a novel mechanism of bacterial growth inhibition which depends on DAP epimerase inhibition by a DAP analog. PMID:3056252

  13. ABA is required for Leptosphaeria maculans resistance via ABI1- and ABI4-dependent signaling.

    PubMed

    Kaliff, Maria; Staal, Jens; Myrenås, Mattias; Dixelius, Christina

    2007-04-01

    Abscisic acid (ABA) is a defense hormone with influence on callose-dependent and -independent resistance against Leptosphaeria maculans acting in the RLMcol pathway. ABA-deficient and -insensitive mutants in Ler-0 background (abal-3 and abil-1) displayed susceptibility to L. maculans, along with a significantly decreased level of callose depositions, whereas abi2-1 and abi3-1 remained resistant, together with the abi5-1 mutant of Ws-0 background. Suppressor mutants of abil-1 confirmed that the L. maculans-susceptible response was due to the dominant negative nature of the abil-1 mutant. Highly induced camalexin levels made ABA mutants in Col-0 background (aba2-1, aba3-1, and abi4-1) appear resistant, but displayed enhanced susceptibility as double mutants with pad3-1, impaired in camalexin biosynthesis. beta-Aminobutyric acid (BABA) pretreatment of Ler-0 contributed to an elevated level of endogenous ABA after L. maculans inoculation. Comparisons between (RLM1co1)pad3 and rlmlLerpad3 showed that ABA and BABA enhancement of callose deposition requires induction from RLM1col. ABII, but not ABI2, was found to be involved in a feedback mechanism that modulates RLM1co, expression. Genetic analysis showed further that this feedback occurs upstream of ABI4 and that components downstream of ABI4 modulate ABIJ activity. ABA and BABA treatments of the L. maculans-susceptible callose synthase mutant pmr4 showed that ABA also induces a callose-independent resistance. Similar treatments enhanced callose depositions and induced resistance to L. maculans in oilseed rape, and BABA-induced resistance was found to be independent of salicylic acid.

  14. Ferrous iron oxidation by Thiobacillus ferrooxidans: inhibition with benzoic acid, sorbic acid and sodium lauryl sulfate

    SciTech Connect

    Onysko, S.J.

    1984-07-01

    Acid mine drainage is formed by the weathering or oxidation of pyritic material exposed during coal mining. The rate of pyritic material oxidation can be greatly accelerated by certain acidophilic bacteria such as Thiobacillus ferrooxidans which catalyse the oxidation of ferrous to ferric iron. A number of organic compounds, under laboratory conditions, can apparently inhibit both the oxidation of ferrous to ferric iron by T. ferrooxidans and the weathering of pyritic material by mixed cultures of acid mine drainage micro-organisms. Sodium lauryl sulphate (SLS), an anionic surfactant has proved effective in this respect. Benzoic acid, sorbic acid and SLS at low concentrations, each effectively inhibited bacterial oxidation of ferrous iron in batch cultures of T. ferrooxidans. The rate of chemical oxidation of ferrous iron in low pH, sterile, batch reactors was not substantially affected at the tested concentrations of any of the compounds.

  15. ABA-induced CCCH tandem zinc finger protein OsC3H47 decreases ABA sensitivity and promotes drought tolerance in Oryza sativa.

    PubMed

    Wang, Wenyi; Liu, Bohan; Xu, Mengyun; Jamil, Muhammad; Wang, Guoping

    2015-08-14

    Water deficit causes multiple negative impacts on plants, such as reactive oxygen species (ROS) accumulation, abscisic acid (ABA) induction, stomatal closure, and decreased photosynthesis. Here, we characterized OsC3H47, which belongs to CCCH zinc-finger families, as a drought-stress response gene. It can be strongly induced by NaCl, PEG, ABA, and drought conditions. Overexpression of OsC3H47 significantly enhanced tolerance to drought and salt stresses in rice seedlings, which indicates that OsC3H47 plays important roles in post-stress recovery. However, overexpression of OsC3H47 reduced the ABA sensitivity of rice seedlings. This suggests that OsC3H47 is a newly discovered gene that can control rice drought-stress response, and it may play an important role in ABA feedback and post-transcription processes. PMID:26047696

  16. Priming effect of abscisic acid on alkaline stress tolerance in rice (Oryza sativa L.) seedlings.

    PubMed

    Wei, Li-Xing; Lv, Bing-Sheng; Wang, Ming-Ming; Ma, Hong-Yuan; Yang, Hao-Yu; Liu, Xiao-Long; Jiang, Chang-Jie; Liang, Zheng-Wei

    2015-05-01

    Saline-alkaline stress is characterized by high salinity and high alkalinity (high pH); alkaline stress has been shown to be the primary factor inhibiting rice seedling growth. In this study, we investigated the potential priming effect of abscisic acid (ABA) on tolerance of rice seedlings to alkaline stress simulated by Na2CO3. Seedlings were pretreated with ABA at concentrations of 0 (control), 10, and 50 μM by root-drench for 24 h and then transferred to a Na2CO3 solution that did not contain ABA. Compared to control treatment, pretreatment with ABA substantially improved the survival rate of rice seedlings and increased biomass accumulation after 7 days under the alkaline condition. ABA application at 10 μM also alleviated the inhibitory effects of alkaline stress on the total root length and root surface area. Physiologically, ABA increased relative water content (RWC) and decreased cell membrane injury degree (MI) and Na(+)/K(+) ratios. In contrast, fluridone (an ABA biosynthesis inhibitor) decreased the RWC and increased MI in shoots under the alkaline conditions. These data suggest that ABA has a potent priming effect on the adaptive response to alkaline stress in rice and may be useful for improving rice growth in saline-alkaline paddy fields.

  17. Abscisic Acid Analogues That Act as Universal or Selective Antagonists of Phytohormone Receptors.

    PubMed

    Rajagopalan, Nandhakishore; Nelson, Ken M; Douglas, Amy F; Jheengut, Vishal; Alarcon, Idralyn Q; McKenna, Sean A; Surpin, Marci; Loewen, Michele C; Abrams, Suzanne R

    2016-09-13

    The plant hormone abscisic acid (ABA) plays many important roles in controlling plant development and physiology, from flowering to senescence. ABA is now known to exert its effects through a family of soluble ABA receptors, which in Arabidopsis thaliana has 13 members divided into three clades. Homologues of these receptors are present in other plants, also in relatively large numbers. Investigation of the roles of each homologue in mediating the diverse physiological roles of ABA is hampered by this genetic redundancy. We report herein the in vitro screening of a targeted ABA-like analogue library and identification of novel antagonist hits, including the analogue PBI686 that had been developed previously as a probe for identifying ABA-binding proteins. Further in vitro characterization of PBI686 and development of second-generation leads yielded both receptor-selective and universal antagonist hits. In planta assays in different species have demonstrated that these antagonist leads can overcome various ABA-induced physiological changes. While the general antagonists open up a hitherto unexplored avenue for controlling plant growth through inhibition of ABA-regulated physiological processes, the receptor-selective antagonist can be developed into chemical probes to explore the physiological roles of individual receptors.

  18. Abscisic Acid Antagonizes Ethylene-Induced Hyponastic Growth in Arabidopsis1[OA

    PubMed Central

    Benschop, Joris J.; Millenaar, Frank F.; Smeets, Maaike E.; van Zanten, Martijn; Voesenek, Laurentius A.C.J.; Peeters, Anton J.M.

    2007-01-01

    Ethylene induces enhanced differential growth in petioles of Arabidopsis (Arabidopsis thaliana), resulting in an upward movement of the leaf blades (hyponastic growth). The amplitude of this effect differs between accessions, with Columbia-0 (Col-0) showing a large response, while in Landsberg erecta (Ler), hyponastic growth is minimal. Abscisic acid (ABA) was found to act as an inhibitory factor of this response in both accessions, but the relationship between ethylene and ABA differed between the two; the ability of ABA to inhibit ethylene-induced hyponasty was significantly more pronounced in Col-0. Mutations in ABI1 or ABI3 induced a strong ethylene-regulated hyponastic growth in the less responsive accession Ler, while the response was abolished in the ABA-hypersensitive era1 in Col-0. Modifications in ABA levels altered petiole angles in the absence of applied ethylene, indicating that ABA influences petiole angles also independently from ethylene. A model is proposed whereby the negative effect of ABA on hyponastic growth is overcome by ethylene in Col-0 but not in Ler. However, when ABA signaling is artificially released in Ler, this regulatory mechanism is bypassed, resulting in a strong hyponastic response in this accession. PMID:17158582

  19. Abscisic Acid Analogues That Act as Universal or Selective Antagonists of Phytohormone Receptors.

    PubMed

    Rajagopalan, Nandhakishore; Nelson, Ken M; Douglas, Amy F; Jheengut, Vishal; Alarcon, Idralyn Q; McKenna, Sean A; Surpin, Marci; Loewen, Michele C; Abrams, Suzanne R

    2016-09-13

    The plant hormone abscisic acid (ABA) plays many important roles in controlling plant development and physiology, from flowering to senescence. ABA is now known to exert its effects through a family of soluble ABA receptors, which in Arabidopsis thaliana has 13 members divided into three clades. Homologues of these receptors are present in other plants, also in relatively large numbers. Investigation of the roles of each homologue in mediating the diverse physiological roles of ABA is hampered by this genetic redundancy. We report herein the in vitro screening of a targeted ABA-like analogue library and identification of novel antagonist hits, including the analogue PBI686 that had been developed previously as a probe for identifying ABA-binding proteins. Further in vitro characterization of PBI686 and development of second-generation leads yielded both receptor-selective and universal antagonist hits. In planta assays in different species have demonstrated that these antagonist leads can overcome various ABA-induced physiological changes. While the general antagonists open up a hitherto unexplored avenue for controlling plant growth through inhibition of ABA-regulated physiological processes, the receptor-selective antagonist can be developed into chemical probes to explore the physiological roles of individual receptors. PMID:27523384

  20. Priming effect of abscisic acid on alkaline stress tolerance in rice (Oryza sativa L.) seedlings.

    PubMed

    Wei, Li-Xing; Lv, Bing-Sheng; Wang, Ming-Ming; Ma, Hong-Yuan; Yang, Hao-Yu; Liu, Xiao-Long; Jiang, Chang-Jie; Liang, Zheng-Wei

    2015-05-01

    Saline-alkaline stress is characterized by high salinity and high alkalinity (high pH); alkaline stress has been shown to be the primary factor inhibiting rice seedling growth. In this study, we investigated the potential priming effect of abscisic acid (ABA) on tolerance of rice seedlings to alkaline stress simulated by Na2CO3. Seedlings were pretreated with ABA at concentrations of 0 (control), 10, and 50 μM by root-drench for 24 h and then transferred to a Na2CO3 solution that did not contain ABA. Compared to control treatment, pretreatment with ABA substantially improved the survival rate of rice seedlings and increased biomass accumulation after 7 days under the alkaline condition. ABA application at 10 μM also alleviated the inhibitory effects of alkaline stress on the total root length and root surface area. Physiologically, ABA increased relative water content (RWC) and decreased cell membrane injury degree (MI) and Na(+)/K(+) ratios. In contrast, fluridone (an ABA biosynthesis inhibitor) decreased the RWC and increased MI in shoots under the alkaline conditions. These data suggest that ABA has a potent priming effect on the adaptive response to alkaline stress in rice and may be useful for improving rice growth in saline-alkaline paddy fields. PMID:25780993

  1. GEM, a member of the GRAM domain family of proteins, is part of the ABA signaling pathway

    PubMed Central

    Mauri, Nuria; Fernández-Marcos, María; Costas, Celina; Desvoyes, Bénédicte; Pichel, Antonio; Caro, Elena; Gutierrez, Crisanto

    2016-01-01

    Abscisic acid (ABA) is fundamental for plant development. Multiple factors have been identified that participate in the ABA signaling network, although a role of many proteins still await to be demonstrated. Here we have investigated the role of GEM (GL2 EXPRESSION MODULATOR), originally annotated as an ABA-responsive protein. GEM contains a GRAM domain, a feature shared with other eight Arabidopsis proteins for which we propose the name of GRE (GEM-RELATED) proteins. We found that (i) GEM expression responds to ABA, (ii) its promoter contains ABRE sites required for ABA response, and (iii) GEM expression depends on members of the ABA signaling pathway. This is consistent with the expression pattern of GEM during development in plant locations were ABA is known to play a direct role. We also found that GEM binds various phospholipids, e.g. mono and diphosphates and phosphatidic acid, suggesting a potential link of GEM with membrane-associated processes. Consistent with this, we found that the phosphoinositol-4-phosphate kinase PIP5K9 binds GEM in vivo. Finally, we demonstrated a role of GEM in seed dormancy. Together, our data led us to propose that GEM is an ABA-responsive protein that may function downstream of ABI5 as part of the ABA signaling pathway. PMID:26939893

  2. Salicylic Acid Inhibits Synthesis of Proteinase Inhibitors in Tomato Leaves Induced by Systemin and Jasmonic Acid.

    PubMed Central

    Doares, S. H.; Narvaez-Vasquez, J.; Conconi, A.; Ryan, C. A.

    1995-01-01

    Salicylic acid (SA) and acetylsalicylic acid (ASA), previously shown to inhibit proteinase inhibitor synthesis induced by wounding, oligouronides (H.M. Doherty, R.R. Selvendran, D.J. Bowles [1988] Physiol Mol Plant Pathol 33: 377-384), and linolenic acid (H. Pena-Cortes, T. Albrecht, S. Prat, E.W. Weiler, L. Willmitzer [1993] Planta 191: 123-128), are shown here to be potent inhibitors of systemin-induced and jasmonic acid (JA)-induced synthesis of proteinase inhibitor mRNAs and proteins. The inhibition by SA and ASA of proteinase inhibitor synthesis induced by systemin and JA, as well as by wounding and oligosaccharide elicitors, provides further evidence that both oligosaccharide and polypeptide inducer molecules utilize the octadecanoid pathway to signal the activation of proteinase inhibitor genes. Tomato (Lycopersicon esculentum) leaves were pulse labeled with [35S]methionine, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the inhibitory effects of SA are shown to be specific for the synthesis of a small number of JA-inducible proteins that includes the proteinase inhibitors. Previous results have shown that SA inhibits the conversion of 13S-hydroperoxy linolenic acid to 12-oxo-phytodienoic acid, thereby inhibiting the signaling pathway by blocking synthesis of JA. Here we report that the inhibition of synthesis of proteinase inhibitor proteins and mRNAs by SA in both light and darkness also occurs at a step in the signal transduction pathway, after JA synthesis but preceding transcription of the inhibitor genes. PMID:12228577

  3. The regulatory network of ThbZIP1 in response to abscisic acid treatment

    PubMed Central

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

    2015-01-01

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

  4. Hyperbaric hyperoxia reversibly inhibits erythrocyte phospholipid fatty acid turnover

    NASA Technical Reports Server (NTRS)

    Dise, Craig A.; Clark, James M.; Lambersten, Christian J.; Goodman, David B. P.

    1987-01-01

    The effect of hyperbaric hyperoxia on the acylation of membrane phospholipid was studied by measuring the rates of activation of exogenous tritiated oleic acid to acyl thioester and of transesterification of the thioester into membrane phospholipids in intact human erythrocytes obtained 1 h after an exposure of the subjects to a hyperbaric oxygen atmosphere (3.5 h, 100 pct O2, 3 ATA). Exposure to pure oxygen was found to inhibit both the acylation and transesterification reactions by more than 30 percent, with partial recovery detected 24 h later. On the other hand, no rate changes were observed when isolated membranes from the same batches of cells were used in similar experiments. It is suggested that the decrease in the incorporation of tritiated oleic acid after hyperbaric hyperoxia may reflect an early event in the pathogenesis of oxygen-induced cellular injury and that it may be a useful index for the assessment of the tolerance of tissues to hyperoxia.

  5. The wheat ABA hypersensitive ERA8 mutant is associated with increased preharvest sprouting tolerance and altered hormone accumulation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wheat preharvest sprouting (PHS) is the germination of mature grain on the mother plant when rain occurs before harvest. Higher abscisic acid (ABA) hormone levels and sensitivity are associated with higher seed dormancy and PHS tolerance. Consistent with this, the ABA hypersensitive ERA8 (Enhanced...

  6. Unusal pattern of product inhibition: batch acetic acid fermentation

    SciTech Connect

    Bar, R.; Gainer, J.L.; Kirwan, D.J.

    1987-04-20

    The limited tolerance of microorganisms to their metabolic products results in inhibited growth and product formation. The relationship between the specific growth rate, micro, and the concentration of an inhibitory product has been described by a number of mathematical models. In most cases, micro was found to be inversely proportional to the product concentration and invariably the rate of substrate utilization followed the same pattern. In this communication, the authors report a rather unusual case in which the formation rate of a product, acetic acid, increased with a decreasing growth rate of the microorganism, Acetobacter aceti. Apparently, a similar behavior was mentioned in a review report with respect to Clostridium thermocellum in a batch culture but was not published in the freely circulating literature. The fermentation of ethanol to acetic acid, C/sub 2/H/sub 5/OH + O/sub 2/ = CH/sub 3/COOH + H/sub 2/O is clearly one of the oldest known fermentations. Because of its association with the commercial production of vinegar it has been a subject of extensive but rather technically oriented studies. Suprisingly, the uncommon uncoupling between the inhibited microbial growth and the product formation appears to have been unnoticed. 13 references.

  7. Asiatic acid inhibits pulmonary inflammation induced by cigarette smoke.

    PubMed

    Lee, Jae-Won; Park, Hyun Ah; Kwon, Ok-Kyoung; Jang, Yin-Gi; Kim, Ju Yeong; Choi, Bo Kyung; Lee, Hee Jae; Lee, Sangwoo; Paik, Jin-Hyub; Oh, Sei-Ryang; Ahn, Kyung-Seop; Lee, Hyun-Jun

    2016-10-01

    Asiatic acid (AA) is one of the major components of Titrated extract of Centella asiatica (TECA), which has been reported to possess antioxidant and anti-inflammatory activities. The purpose of this study was to investigate the protective effect of AA on pulmonary inflammation induced by cigarette smoke (CS). AA significantly attenuated the infiltration of inflammatory cells in bronchoalveolar lavage fluid (BALF) of CS exposure mice. AA also decreased ROS production and NE activity, and inhibited the release of proinflammatory cytokines in BALF. AA reduced the recruitment of inflammatory cells and MCP-1 expression in lung tissue of CS exposure mice. AA also attenuated mucus overproduction, and decreased the activation of MAPKs and NF-kB in lung tissue. Furthermore, AA increased HO-1 expression and inhibited the reduced expression of SOD3 in lung tissue. These findings indicate that AA effectively inhibits pulmonary inflammatory response, which is an important process in the development of chronic obstructive pulmonary disease (COPD) via suppression of inflammatory mediators and induction of HO-1. Therefore, we suggest that AA has the potential to treat inflammatory disease such as COPD.

  8. Inhibition of acid sphingomyelinase by tricyclic antidepressants and analogons

    PubMed Central

    Beckmann, Nadine; Sharma, Deepa; Gulbins, Erich; Becker, Katrin Anne; Edelmann, Bärbel

    2014-01-01

    Amitriptyline, a tricyclic antidepressant, has been used in the clinic to treat a number of disorders, in particular major depression and neuropathic pain. In the 1970s the ability of tricyclic antidepressants to inhibit acid sphingomyelinase (ASM) was discovered. The enzyme ASM catalyzes the hydrolysis of sphingomyelin to ceramide. ASM and ceramide were shown to play a crucial role in a wide range of diseases, including cancer, cystic fibrosis, diabetes, Alzheimer's disease, and major depression, as well as viral (e.g., measles virus) and bacterial (e.g., Staphylococcus aureus, Pseudomonas aeruginosa) infections. Ceramide molecules may act in these diseases by the alteration of membrane biophysics, the self-association of ceramide molecules within the cell membrane and the ultimate formation of larger ceramide-enriched membrane domains/platforms. These domains were shown to serve the clustering of certain receptors such as CD95 and may also act in the above named diseases. The potential to block the generation of ceramide by inhibiting the ASM has opened up new therapeutic approaches for the treatment of these conditions. Since amitriptyline is one of the longest used clinical drugs and side effects are well studied, it could potentially become a cheap and easily accessible medication for patients suffering from these diseases. In this review, we aim to provide an overview of current in vitro and in vivo studies and clinical trials utilizing amitriptyline to inhibit ASM and contemplate possible future applications of the drug. PMID:25228885

  9. Effects of abscisic acid and xanthoxin on elongation and gravitropism in primary roots of Zea mays

    NASA Technical Reports Server (NTRS)

    Lee, J. S.; Hasenstein, K. H.; Mulkey, T. J.; Yang, R. L.; Evans, M. L.

    1990-01-01

    We examined the involvement of abscisic acid (ABA) and xanthoxin (Xan) in maize root gravitropism by (1) testing the ability of ABA to allow positive gravitropism in dark-grown seedlings of the maize cultivar LG11, a cultivar known to require light for positive gravitropism of the primary root, (2) comparing curvature in roots in which half of the cap had been excised and replaced with agar containing either ABA or indole-3-acetic acid (IAA), (3) measuring gravitropism in roots of seedlings submerged in oxygenated solutions of ABA or IAA and (4) testing the effect of Xan on root elongation. Using a variety of methods of applying ABA to the root, we found that ABA did not cause horizontally-oriented primary roots of dark-grown seedlings to become positively gravitropic. Replacing half of the root cap of vertically oriented roots with an agar block containing ABA had little or no effect on curvature relative to that of controls in which the half cap was replaced by a plain agar block. Replacement of the removed half cap with IAA either canceled or reversed the curvature displayed by controls. When light-grown seedlings were submerged in ABA they responded strongly to gravistimulation while those in IAA did not. Xan (up to 0.1 mM) did not affect root elongation. The results indicate that ABA is not a likely mediator of root gravitropism and that the putative ABA precursor, Xan, lacks the appropriate growth-inhibiting properties to serve as a mediator of root gravitropism.

  10. Effects of phosphate deficiency and sugars on expression of rab18 in Arabidopsis: hexokinase-dependent and okadaic acid-sensitive transduction of the sugar signal.

    PubMed

    Ciereszko, Iwona; Kleczkowski, Leszek A

    2002-11-13

    The lack of phosphorus in the nutrient medium increased the expression of rab18, an abscisic acid (ABA)-responsive gene, in leaves of Arabidopsis thaliana. The expression of this gene was also upregulated after feeding the excised leaves with D-mannose and sucrose for both wild-type (wt) and aba1 (ABA-deficient) mutant plants. For aba1 mutants, both the phosphate deficiency and sugar effects on rab18 were weaker than in wt plants, suggesting possible involvement of both ABA-dependent and ABA-independent components in signalling. Transgenic Arabidopsis plants with increased hexokinase (HXK) expression had a much higher sucrose-dependent level of rab18 mRNA, implying the HXK involvement in sensing/transmitting the sugar signal. Sucrose-related induction of rab18 was completely inhibited by okadaic acid (OKA), suggesting the involvement of specific protein phosphatase(s) in transduction of the sugar signal. The results suggest that rab18 is regulated via interaction of a plethora of signals, including ABA, sugar and phosphate deficiency, and that the sugar effect is transmitted via a HXK-pathway, involving OKA-sensitive component(s). The findings prompt caution in linking the expression of rab18 solely to ABA signalling.

  11. HAB1–SWI3B Interaction Reveals a Link between Abscisic Acid Signaling and Putative SWI/SNF Chromatin-Remodeling Complexes in Arabidopsis[C][W

    PubMed Central

    Saez, Angela; Rodrigues, Americo; Santiago, Julia; Rubio, Silvia; Rodriguez, Pedro L.

    2008-01-01

    Abscisic acid (ABA) has an important role for plant growth, development, and stress adaptation. HYPERSENSITIVE TO ABA1 (HAB1) is a protein phosphatase type 2C that plays a key role as a negative regulator of ABA signaling; however, the molecular details of HAB1 action in this process are not known. A two-hybrid screen revealed that SWI3B, an Arabidopsis thaliana homolog of the yeast SWI3 subunit of SWI/SNF chromatin-remodeling complexes, is a prevalent interacting partner of HAB1. The interaction mapped to the N-terminal half of SWI3B and required an intact protein phosphatase catalytic domain. Bimolecular fluorescence complementation and coimmunoprecipitation assays confirmed the interaction of HAB1 and SWI3B in the nucleus of plant cells. swi3b mutants showed a reduced sensitivity to ABA-mediated inhibition of seed germination and growth and reduced expression of the ABA-responsive genes RAB18 and RD29B. Chromatin immunoprecipitation experiments showed that the presence of HAB1 in the vicinity of RD29B and RAB18 promoters was abolished by ABA, which suggests a direct involvement of HAB1 in the regulation of ABA-induced transcription. Additionally, our results uncover SWI3B as a novel positive regulator of ABA signaling and suggest that HAB1 modulates ABA response through the regulation of a putative SWI/SNF chromatin-remodeling complex. PMID:19033529

  12. Arabidopsis YAK1 regulates abscisic acid response and drought resistance.

    PubMed

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

    2016-07-01

    Abscisic acid (ABA) is an important phytohormone that controls several plant processes such as seed germination, seedling growth, and abiotic stress response. Here, we report that AtYak1 plays an important role in ABA signaling and postgermination growth in Arabidopsis. AtYak1 knockout mutant plants were hyposensitive to ABA inhibition of seed germination, cotyledon greening, seedling growth, and stomatal movement. atyak1-1 mutant plants display reduced drought stress resistance, as evidenced by water loss rate and survival rate. Molecular genetic analysis revealed that AtYak1 deficiency led to elevated expression of stomatal-related gene, MYB60, and down-regulation of several stress-responsive genes. Altogether, these results indicate that AtYak1 plays a role as a positive regulator in ABA-mediated drought response in Arabidopsis. PMID:27264339

  13. POLYAMINE OXIDASE2 of Arabidopsis contributes to ABA mediated plant developmental processes.

    PubMed

    Wimalasekera, Rinukshi; Schaarschmidt, Frank; Angelini, Riccardo; Cona, Alessandra; Tavladoraki, Parasklevi; Scherer, Günther F E

    2015-11-01

    Polyamines (PA) are catabolised by two groups of amine oxidases, the copper-binding amine oxidases (CuAOs) and the FAD-binding polyamine oxidases (PAOs). Previously, we have shown that CuAO1 is involved in ABA associated growth responses and ABA- and PA-mediated rapid nitric oxide (NO) production. Here we report the differential regulation of expression of POLYAMINE OXIDASE2 of Arabidopsis (AtPAO2) in interaction with ABA, nitrate and ammonium. Without ABA treatment germination, cotyledon growth and fresh weight of pao2 knockdown mutants as well as PAO2OX over-expressor plants were comparable to those of the wild type (WT) plants irrespective of the N source. In the presence of ABA, in pao2 mutants cotyledon growth and fresh weights were more sensitive to inhibition by ABA while PAO2OX over-expressor plants showed a rather similar response to WT. When NO3(-) was the only N source primary root lengths and lateral root numbers were lower in pao2 mutants both without and with exogenous ABA. PAO2OX showed enhanced primary and lateral root growth in media with NO3(-) or NH4(+). Vigorous root growth of PAO2OX and the hypersensitivity of pao2 mutants to ABA suggest a positive function of AtPAO2 in root growth. ABA-induced NO production in pao2 mutants was lower indicating a potential contributory function of AtPAO2 in NO-mediated effects on root growth. PMID:26310141

  14. Kinetic-spectrophotometric determination of ascorbic acid by inhibition of the hydrochloric acid-bromate reaction

    NASA Astrophysics Data System (ADS)

    Ensafi, Ali A.; Rezaei, B.; Movahedinia, H.

    2002-10-01

    A new analytical method was developed for the determination of ascorbic acid in fruit juice and pharmaceuticals. The method is based on its inhibition effect on the reaction between hydrochloric acid and bromate. The decolourisation of Methyl Orange by the reaction products was used to monitor the reaction spectrophotometrically at 510 nm. The linearity range of the calibration graph depends on bromate concentration. The variable affecting the rate of the reaction was investigated. The method is simple, rapid, relatively sensitive and precise. The limit of detection is 7.6×10 -6 M and calibration rang is 8×10 -6-1.2×10 -3 M ascorbic acid. The relative standard deviation of seven replication determinations of 8×10 -6 and 2×10 -5 M ascorbic acid was 2.8 and 1.7%, respectively. The influence of potential interfering substance was studied. The method was successfully applied for the determination of ascorbic acid in pharmaceuticals.

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

    SciTech Connect

    Melcher, Karsten; Ng, Ley-Moy; Zhou, X Edward; Soon, Fen-Fen; Xu, Yong; Suino-Powell, Kelly M; Park, Sang-Youl; Weiner, Joshua J; Fujii, Hiroaki; Chinnusamy, Viswanathan; Kovach, Amanda; Li, Jun; Wang, Yonghong; Li, Jiayang; Peterson, Francis C; Jensen, Davin R; Yong, Eu-Leong; Volkman, Brian F; Cutler, Sean R; Zhu, Jian-Kang; Xu, H Eric

    2010-01-12

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

  16. Linking Turgor with ABA Biosynthesis: Implications for Stomatal Responses to Vapor Pressure Deficit across Land Plants.

    PubMed

    McAdam, Scott A M; Brodribb, Timothy J

    2016-07-01

    Stomatal responses to changes in vapor pressure deficit (VPD) constitute the predominant form of daytime gas-exchange regulation in plants. Stomatal closure in response to increased VPD is driven by the rapid up-regulation of foliar abscisic acid (ABA) biosynthesis and ABA levels in angiosperms; however, very little is known about the physiological trigger for this increase in ABA biosynthesis at increased VPD Using a novel method of modifying leaf cell turgor by the application of external pressures, we test whether changes in turgor pressure can trigger increases in foliar ABA levels over 20 min, a period of time most relevant to the stomatal response to VPD We found in angiosperm species that the biosynthesis of ABA was triggered by reductions in leaf turgor, and in two species tested, that a higher sensitivity of ABA synthesis to leaf turgor corresponded with a higher stomatal sensitivity to VPD In contrast, representative species from nonflowering plant lineages did not show a rapid turgor-triggered increase in foliar ABA levels, which is consistent with previous studies demonstrating passive stomatal responses to changes in VPD in these lineages. Our method provides a new tool for characterizing the response of stomata to water availability.

  17. Loss of ACS7 confers abiotic stress tolerance by modulating ABA sensitivity and accumulation in Arabidopsis.

    PubMed

    Dong, Hui; Zhen, Zhiqin; Peng, Jinying; Chang, Li; Gong, Qingqiu; Wang, Ning Ning

    2011-10-01

    The phytohormones ethylene and abscisic acid (ABA) play essential roles in the abiotic stress adaptation of plants, with both cross-talk of ethylene signalling and ABA biosynthesis and signalling reported. Any reciprocal effects on each other's biosynthesis, however, remain elusive. ACC synthase (ACS) acts as the key enzyme in ethylene biosynthesis. A pilot study on changes in ACS promoter activities in response to abiotic stresses revealed the unique involvement in abiotic stress responses of the only type 3 ACC synthase, ACS7, among all nine ACSs of Arabidopsis. Hence an acs7 mutant was characterized and its abiotic stress responses were analysed. The acs7 mutant germinated slightly faster than the wild type and subsequently maintained a higher growth rate at the vegetative growth stage. Ethylene emission of acs7 was merely one-third of that of the wild type. acs7 exhibited enhanced tolerance to salt, osmotic, and heat stresses. Furthermore, acs7 seeds were hypersensitive to both ABA and glucose during germination. Transcript analyses revealed that acs7 had elevated transcript levels of the stress-responsive genes involved in the ABA-dependent pathway under salt stress. The ABA level was also higher in acs7 following salt treatment. Our data suggest that ACS7 acts as a negative regulator of ABA sensitivity and accumulation under stress and appears as a node in the cross-talk between ethylene and ABA.

  18. Linking Turgor with ABA Biosynthesis: Implications for Stomatal Responses to Vapor Pressure Deficit across Land Plants.

    PubMed

    McAdam, Scott A M; Brodribb, Timothy J

    2016-07-01

    Stomatal responses to changes in vapor pressure deficit (VPD) constitute the predominant form of daytime gas-exchange regulation in plants. Stomatal closure in response to increased VPD is driven by the rapid up-regulation of foliar abscisic acid (ABA) biosynthesis and ABA levels in angiosperms; however, very little is known about the physiological trigger for this increase in ABA biosynthesis at increased VPD Using a novel method of modifying leaf cell turgor by the application of external pressures, we test whether changes in turgor pressure can trigger increases in foliar ABA levels over 20 min, a period of time most relevant to the stomatal response to VPD We found in angiosperm species that the biosynthesis of ABA was triggered by reductions in leaf turgor, and in two species tested, that a higher sensitivity of ABA synthesis to leaf turgor corresponded with a higher stomatal sensitivity to VPD In contrast, representative species from nonflowering plant lineages did not show a rapid turgor-triggered increase in foliar ABA levels, which is consistent with previous studies demonstrating passive stomatal responses to changes in VPD in these lineages. Our method provides a new tool for characterizing the response of stomata to water availability. PMID:27208264

  19. A proteomic analysis of rice seed germination as affected by high temperature and ABA treatment.

    PubMed

    Liu, Shu-Jun; Xu, Heng-Heng; Wang, Wei-Qing; Li, Ni; Wang, Wei-Ping; Møller, Ian Max; Song, Song-Quan

    2015-05-01

    Seed germination is a critical phase in the plant life cycle, but the specific events associated with seed germination are still not fully understood. In this study, we used two-dimensional gel electrophoresis followed by mass spectrometry to investigate the changes in the proteome during imbibition of Oryza sativa seeds at optimal temperature with or without abscisic acid (ABA) and high temperature (germination thermoinhibition) to further identify and quantify key proteins required for seed germination. A total of 121 protein spots showed a significant change in abundance (1.5-fold increase/decrease) during germination under all conditions. Among these proteins, we found seven proteins specifically associated with seed germination including glycosyl hydrolases family 38 protein, granule-bound starch synthase 1, Os03g0842900 (putative steroleosin-B), N-carbamoylputrescine amidase, spermidine synthase 1, tubulin α-1 chain and glutelin type-A; and a total of 20 imbibition response proteins involved in energy metabolism, cell growth, cell defense and storage proteins. High temperature inhibited seed germination by decreasing the abundance of proteins involved in methionine metabolism, amino acid biosynthesis, energy metabolism, reserve degradation, protein folding and stress responses. ABA treatment inhibited germination and decreased the abundance of proteins associated with methionine metabolism, energy production and cell division. Our results show that changes in many biological processes including energy metabolism, protein synthesis and cell defense and rescue occurred as a result of all treatments, while enzymes involved in methionine metabolism and weakening of cell wall specifically accumulated when the seeds germinated at the optimal temperature.

  20. Melatonin promotes seed germination under high salinity by regulating antioxidant systems, ABA and GA₄ interaction in cucumber (Cucumis sativus L.).

    PubMed

    Zhang, Hai-Jun; Zhang, Na; Yang, Rong-Chao; Wang, Li; Sun, Qian-Qian; Li, Dian-Bo; Cao, Yun-Yun; Weeda, Sarah; Zhao, Bing; Ren, Shuxin; Guo, Yang-Dong

    2014-10-01

    Although previous studies have found that melatonin can promote seed germination, the mechanisms involved in perceiving and signaling melatonin remain poorly understood. In this study, it was found that melatonin was synthesized during cucumber seed germination with a peak in melatonin levels occurring 14 hr into germination. This is indicative of a correlation between melatonin synthesis and seed germination. Meanwhile, seeds pretreated with exogenous melatonin (1 μM) showed enhanced germination rates under 150 mM NaCl stress compared to water-pretreated seeds under salinity stress. There are two apparent mechanisms by which melatonin alleviated salinity-induced inhibition of seed germination. Exogenous melatonin decreased oxidative damage induced by NaCl stress by enhancing gene expression of antioxidants. Under NaCl stress, compared to untreated control, the activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were significantly increased by approximately 1.3-5.0-fold, with a concomitant 1.4-2.0-fold increase of CsCu-ZnSOD, CsFe-ZnSOD, CsCAT, and CsPOD in melatonin-pretreated seeds. Melatonin also alleviated salinity stress by affecting abscisic acid (ABA) and gibberellin acid (GA) biosynthesis and catabolism during seed germination. Compared to NaCl treatment, melatonin significantly up-regulated ABA catabolism genes (e.g., CsCYP707A1 and CsCYP707A2, 3.5 and 105-fold higher than NaCl treatment at 16 hr, respectively) and down-regulated ABA biosynthesis genes (e.g., CsNECD2, 0.29-fold of CK2 at 16 hr), resulting in a rapid decrease of ABA content during the early stage of germination. At the same time, melatonin positively up-regulated GA biosynthesis genes (e.g., GA20ox and GA3ox, 2.3 and 3.9-fold higher than NaCl treatment at 0 and 12 hr, respectively), contributing to a significant increase of GA (especially GA4) content. In this study, we provide new evidence suggesting that melatonin alleviates the

  1. Boric acid inhibits embryonic histone deacetylases: A suggested mechanism to explain boric acid-related teratogenicity

    SciTech Connect

    Di Renzo, Francesca; Cappelletti, Graziella; Broccia, Maria L.; Giavini, Erminio; Menegola, Elena . E-mail: elena.menegola@unimi.it

    2007-04-15

    Histone deacetylases (HDAC) control gene expression by changing histonic as well as non histonic protein conformation. HDAC inhibitors (HDACi) are considered to be among the most promising drugs for epigenetic treatment for cancer. Recently a strict relationship between histone hyperacetylation in specific tissues of mouse embryos exposed to two HDACi (valproic acid and trichostatin A) and specific axial skeleton malformations has been demonstrated. The aim of this study is to verify if boric acid (BA), that induces in rodents malformations similar to those valproic acid and trichostatin A-related, acts through similar mechanisms: HDAC inhibition and histone hyperacetylation. Pregnant mice were treated intraperitoneally with a teratogenic dose of BA (1000 mg/kg, day 8 of gestation). Western blot analysis and immunostaining were performed with anti hyperacetylated histone 4 (H4) antibody on embryos explanted 1, 3 or 4 h after treatment and revealed H4 hyperacetylation at the level of somites. HDAC enzyme assay was performed on embryonic nuclear extracts. A significant HDAC inhibition activity (compatible with a mixed type partial inhibition mechanism) was evident with BA. Kinetic analyses indicate that BA modifies substrate affinity by a factor {alpha} = 0.51 and maximum velocity by a factor {beta} = 0.70. This work provides the first evidence for HDAC inhibition by BA and suggests such a molecular mechanism for the induction of BA-related malformations.

  2. Quantitative iTRAQ-based proteomic analysis of phosphoproteins and ABA-regulated phosphoproteins in maize leaves under osmotic stress

    PubMed Central

    Hu, Xiuli; Li, Nana; Wu, Liuji; Li, Chunqi; Li, Chaohai; Zhang, Li; Liu, Tianxue; Wang, Wei

    2015-01-01

    Abscisic acid (ABA) regulates various developmental processes and stress responses in plants. Protein phosphorylation/dephosphorylation is a central post-translational modification (PTM) in ABA signaling. However, the phosphoproteins regulated by ABA under osmotic stress remain unknown in maize. In this study, maize mutant vp5 (deficient in ABA biosynthesis) and wild-type Vp5 were used to identify leaf phosphoproteins regulated by ABA under osmotic stress. Up to 4052 phosphopeptides, corresponding to 3017 phosphoproteins, were identified by Multiplex run iTRAQ-based quantitative proteomic and LC-MS/MS methods. The 4052 phosphopeptides contained 5723 non-redundant phosphosites; 512 phosphopeptides (379 in Vp5, 133 in vp5) displayed at least a 1.5-fold change of phosphorylation level under osmotic stress, of which 40 shared common in both genotypes and were differentially regulated by ABA. Comparing the signaling pathways involved in vp5 response to osmotic stress and those that in Vp5, indicated that ABA played a vital role in regulating these pathways related to mRNA synthesis, protein synthesis and photosynthesis. Our results provide a comprehensive dataset of phosphopeptides and phosphorylation sites regulated by ABA in maize adaptation to osmotic stress. This will be helpful to elucidate the ABA-mediate mechanism of maize endurance to drought by triggering phosphorylation or dephosphorylation cascades. PMID:26503333

  3. Metabolism of 5'alpha,8'-cycloabscisic acid, a highly potent and long-lasting abscisic acid analogue, in radish seedlings.

    PubMed

    Todoroki, Yasushi; Sawada, Masao; Matsumoto, Miyuki; Tsukada, Shigeko; Ueno, Kotomi; Isaka, Masatoshi; Owaki, Mariko; Hirai, Nobuhiro

    2004-01-15

    We synthesized 5'alpha,8'-cycloabscisic acid (CycloABA), a highly potent and long-lasting abscisic acid (ABA) analogue, by a different method from that reported before. CycloABA fed to radish seedlings had more metabolic tolerance than ABA. The major metabolite of CycloABA was the glucose conjugate, which was the minor metabolite of ABA. The 8'-hydroxylated metabolite and its cyclized isomer, which were major metabolites of ABA, were not found as metabolites of CycloABA. The present results suggest that the highly potent and long-lasting activity of CycloABA is caused by resistance to ABA 8'-hydroxylase, and that CycloABA is partially metabolized to the glucose conjugate by ABA glucosyltransferase.

  4. Implication of Abscisic Acid on Ripening and Quality in Sweet Cherries: Differential Effects during Pre- and Post-harvest.

    PubMed

    Tijero, Verónica; Teribia, Natalia; Muñoz, Paula; Munné-Bosch, Sergi

    2016-01-01

    Sweet cherry, a non-climacteric fruit, is usually cold-stored during post-harvest to prevent over-ripening. The aim of the study was to evaluate the role of abscisic acid (ABA) on fruit growth and ripening of this fruit, considering as well its putative implication in over-ripening and effects on quality. We measured the endogenous concentrations of ABA during the ripening of sweet cherries (Prunus avium L. var. Prime Giant) collected from orchard trees and in cherries exposed to 4°C and 23°C during 10 days of post-harvest. Furthermore, we examined to what extent endogenous ABA concentrations were related to quality parameters, such as fruit biomass, anthocyanin accumulation and levels of vitamins C and E. Endogenous concentrations of ABA in fruits increased progressively during fruit growth and ripening on the tree, to decrease later during post-harvest at 23°C. Cold treatment, however, increased ABA levels and led to an inhibition of over-ripening. Furthermore, ABA levels positively correlated with anthocyanin and vitamin E levels during pre-harvest, but not during post-harvest. We conclude that ABA plays a major role in sweet cherry development, stimulating its ripening process and positively influencing quality parameters during pre-harvest. The possible influence of ABA preventing over-ripening in cold-stored sweet cherries is also discussed. PMID:27200070

  5. Implication of Abscisic Acid on Ripening and Quality in Sweet Cherries: Differential Effects during Pre- and Post-harvest

    PubMed Central

    Tijero, Verónica; Teribia, Natalia; Muñoz, Paula; Munné-Bosch, Sergi

    2016-01-01

    Sweet cherry, a non-climacteric fruit, is usually cold-stored during post-harvest to prevent over-ripening. The aim of the study was to evaluate the role of abscisic acid (ABA) on fruit growth and ripening of this fruit, considering as well its putative implication in over-ripening and effects on quality. We measured the endogenous concentrations of ABA during the ripening of sweet cherries (Prunus avium L. var. Prime Giant) collected from orchard trees and in cherries exposed to 4°C and 23°C during 10 days of post-harvest. Furthermore, we examined to what extent endogenous ABA concentrations were related to quality parameters, such as fruit biomass, anthocyanin accumulation and levels of vitamins C and E. Endogenous concentrations of ABA in fruits increased progressively during fruit growth and ripening on the tree, to decrease later during post-harvest at 23°C. Cold treatment, however, increased ABA levels and led to an inhibition of over-ripening. Furthermore, ABA levels positively correlated with anthocyanin and vitamin E levels during pre-harvest, but not during post-harvest. We conclude that ABA plays a major role in sweet cherry development, stimulating its ripening process and positively influencing quality parameters during pre-harvest. The possible influence of ABA preventing over-ripening in cold-stored sweet cherries is also discussed. PMID:27200070

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

  9. Endogenous Abscisic Acid and Indole-3-Acetic Acid and Somatic Embryogenesis in Cultured Leaf Explants of Pennisetum purpureum Schum. 1

    PubMed Central

    Rajasekaran, Kanniah; Hein, Mich B.; Vasil, Indra K.

    1987-01-01

    Effects of application in vivo of glyphosate, fluridone, and paclobutrazol to glasshouse-grown donor plants of Pennisetum purpureum Schum. on endogenous levels of abscisic acid (ABA) and indole-3-acetic acid (IAA) in young leaves and on somatic embryogenesis in cultured leaf explants were studied. Treatment of plants with glyphosate (100 milligrams per liter) resulted in elevated levels of endogenous ABA and IAA in young leaves. In contrast, paclobutrazol (50% active ingredient; 200 milligrams per liter) did not alter the endogenous levels of ABA and IAA. Fluridone (100 milligrams per liter) markedly inhibited synthesis of ABA and leaf explants from fluridone-treated plants lost the capacity for somatic embryogenesis. Explants from glyphosate- or paclobutrazol-treated plants did not show any reduction in embryogenic capacity when compared with untreated control plants. Glyphosate and fluridone were also incorporated into the culture media at various concentrations (0 to 20 milligrams per liter) to study their effects in vitro on somatic embryogenesis in leaf explants from untreated, field-grown plants. Glyphosate was inhibitory to somatic embryogenesis but only at concentrations above 5 milligrams per liter. Fluridone inhibited somatic embryogenesis at all concentrations tested. Inhibition of somatic embryogenesis by fluridone, by either in vivo or in vitro application, could be overcome partially by (±)-ABA added to the culture medium. Exogenous application of (±)-ABA enhanced somatic embryogenesis and reduced the formation of nonembryogenic callus. Application of IAA or gibberellic acid (GA3; >5 milligrams per liter) was inhibitory to somatic embryogenesis. These results indicate that endogenous ABA is one of the important factors controlling the embryogenic capacity of leaf explants in Napier grass. PMID:16665403

  10. Monomethylarsonous acid inhibited endogenous cholesterol biosynthesis in human skin fibroblasts

    SciTech Connect

    Guo, Lei; Xiao, Yongsheng; Wang, Yinsheng

    2014-05-15

    Human exposure to arsenic in drinking water is a widespread public health concern, and such exposure is known to be associated with many human diseases. The detailed molecular mechanisms about how arsenic species contribute to the adverse human health effects, however, remain incompletely understood. Monomethylarsonous acid [MMA(III)] is a highly toxic and stable metabolite of inorganic arsenic. To exploit the mechanisms through which MMA(III) exerts its cytotoxic effect, we adopted a quantitative proteomic approach, by coupling stable isotope labeling by amino acids in cell culture (SILAC) with LC-MS/MS analysis, to examine the variation in the entire proteome of GM00637 human skin fibroblasts following acute MMA(III) exposure. Among the ∼ 6500 unique proteins quantified, ∼ 300 displayed significant changes in expression after exposure with 2 μM MMA(III) for 24 h. Subsequent analysis revealed the perturbation of de novo cholesterol biosynthesis, selenoprotein synthesis and Nrf2 pathways evoked by MMA(III) exposure. Particularly, MMA(III) treatment resulted in considerable down-regulation of several enzymes involved in cholesterol biosynthesis. In addition, real-time PCR analysis showed reduced mRNA levels of select genes in this pathway. Furthermore, MMA(III) exposure contributed to a distinct decline in cellular cholesterol content and significant growth inhibition of multiple cell lines, both of which could be restored by supplementation of cholesterol to the culture media. Collectively, the present study demonstrated that the cytotoxicity of MMA(III) may arise, at least in part, from the down-regulation of cholesterol biosynthesis enzymes and the resultant decrease of cellular cholesterol content. - Highlights: • MMA(III)-induced perturbation of the entire proteome of GM00637 cells is studied. • Quantitative proteomic approach revealed alterations of multiple cellular pathways. • MMA(III) inhibits de novo cholesterol biosynthesis. • MMA

  11. Perfluoroalkyl Acids Inhibit Reductive Dechlorination of Trichloroethene by Repressing Dehalococcoides.

    PubMed

    Weathers, Tess S; Harding-Marjanovic, Katie; Higgins, Christopher P; Alvarez-Cohen, Lisa; Sharp, Jonathan O

    2016-01-01

    The subsurface recalcitrance of perfluoroalkyl acids (PFAAs) derived from aqueous film-forming foams could have adverse impacts on the microbiological processes used for the bioremediation of co-mingled chlorinated solvents such as trichloroethene (TCE). Here, we show that reductive dechlorination by a methanogenic, mixed culture was significantly inhibited when exposed to concentrations representative of PFAA source zones (>66 mg/L total of 11 PFAA analytes, 6 mg/L each). TCE dechlorination, cis-dichloroethene and vinyl chloride production and dechlorination, and ethene generation were all inhibited at these PFAA concentrations. Phylogenetic analysis revealed that the abundances of 65% of the operational taxonomic units (OTUs) changed significantly when grown in the presence of PFAAs, although repression or enhancement resulting from PFAA exposure did not correlate with putative function or phylogeny. Notably, there was significant repression of Dehalococcoides (8-fold decrease in abundance) coupled with a corresponding enhancement of methane-generating Archaea (a 9-fold increase). Growth and dechlorination by axenic cultures of Dehalococcoides mccartyi strain 195 were similarly repressed under these conditions, confirming an inhibitory response of this pivotal genus to PFAA presence. These results suggest that chlorinated solvent bioattenuation rates could be impeded in subsurface environments near PFAA source zones. PMID:26636352

  12. Inhibition of the Hematopoietic Protein Tyrosine Phosphatase by Phenoxyacetic Acids.

    PubMed

    Bobkova, Ekaterina V; Liu, Wallace H; Colayco, Sharon; Rascon, Justin; Vasile, Stefan; Gasior, Carlton; Critton, David A; Chan, Xochella; Dahl, Russell; Su, Ying; Sergienko, Eduard; Chung, Thomas D Y; Mustelin, Tomas; Page, Rebecca; Tautz, Lutz

    2011-02-01

    Protein tyrosine phosphatases (PTPs) have only recently become the focus of attention in the search for novel drug targets despite the fact that they play vital roles in numerous cellular processes and are implicated in many human diseases. The hematopoietic protein tyrosine phosphatase (HePTP) is often found dysregulated in preleukemic myelodysplastic syndrome (MDS), as well as in acute myelogenous leukemia (AML). Physiological substrates of HePTP include the mitogen-activated protein kinases (MAPKs) ERK1/2 and p38. Specific modulators of HePTP catalytic activity will be useful for elucidating mechanisms of MAPK regulation in hematopietic cells, and may also provide treatments for hematopoietic malignancies such as AML. Here we report the discovery of phenoxyacetic acids as inhibitors of HePTP. Structure-activity relationship (SAR) analysis and in silico docking studies reveal the molecular basis of HePTP inhibition by these compounds. We also show that these compounds are able to penetrate cell membranes and inhibit HePTP in human T lymphocytes.

  13. Dynamic subnuclear relocalization of WRKY40, a potential new mechanism of ABA-dependent transcription factor regulation.

    PubMed

    Geilen, Katja; Böhmer, Maik

    2015-01-01

    The phytohormone ABA plays a major role during plant development, e.g. seed maturation and seed germination, and during adaptation to abiotic stresses like stomatal aperture regulation. The three closely related WRKY transcription factors WRKY18, WRKY40 and WRKY60 function in ABA signal transduction. We recently demonstrated that WRKY18 and WRKY40 but not WRKY60 localize to nuclear bodies in A. thaliana mesophyll protoplasts. WRKY40, a negative regulator of ABA-dependent inhibition of seed germination, relocalizes from PNBs to the nucleoplasm in the presence of ABA in a dynamic and phosphorylation-dependent manner. We propose that subnuclear relocalization of WRKY40 might constitute a new regulatory mechanism of ABA-dependent modulation of transcription factor activity. PMID:26479147

  14. Ursolic acid and oleanolic acid from Eriobotrya fragrans inhibited the viability of A549 cells.

    PubMed

    Yuan, Yuan; Gao, Yongshun; Song, Gang; Lin, Shunquan

    2015-02-01

    Loquat {Eriobotrya japonica (Lindl.)}, a kind of Chinese herb, has many efficacies such as anti-inflammatory, antimicrobial and curing chronic bronchitis. However, reports on the pharmacological action of wild loquat extract are limited. In this work, the A549 cell line was selected to study the inhibitory effect of ursolic acid and oleanolic acid (UA, OA) from the leaves of E. fragrans. Results showed that UA/OA inhibited A549 cell viability and induced apoptosis in a dose and time dependent manner. The cell fraction in the G0/G1 phase dramatically increased under treatment with UA/OA. Data showed that UA activated the expression of PARP. UA and OA down-regulated MMP-2 and Bcl-2; on the contrary, they up-regulated Bid. This work demonstrated that UA/OA extracted from wild loquat leaves can significantly inhibit the viability of A549 cells.

  15. ABA Affects Brassinosteroid-Induced Antioxidant Defense via ZmMAP65-1a in Maize Plants.

    PubMed

    Zhu, Yuan; Liu, Weijuan; Sheng, Yu; Zhang, Juan; Chiu, Tsanyu; Yan, Jingwei; Jiang, Mingyi; Tan, Mingpu; Zhang, Aying

    2015-07-01

    Brassinosteroids (BRs) and ABA co-ordinately regulate water deficit tolerance in maize leaves. ZmMAP65-1a, a maize microtubule-associated protein (MAP) which plays an essential role in BR-induced antioxidant defense, has been characterized previously. However, the interactions among BR, ABA and ZmMAP65-1a in water deficit tolerance remain unexplored. In this study, we demonstrated that ABA was required for BR-induced antioxidant defense via ZmMAP65-1a by using biochemical blocking and ABA biosynthetic mutants. The expression of ZmMAP65-1a in maize leaves and mesophyll protoplasts could be increased under polyethylene glycol- (PEG) stimulated water deficit and ABA treatments. Furthermore, the importance of ABA in the early pathway of BR-induced water deficit tolerance was demonstrated by limiting ABA availability. Blocking ABA biosynthesis biochemically or by a null mutation inhibited the downstream gene expression of ZmMAP65-1a and the activity of ZmMAPK5 in the pathway. It also affected the activities of BR-induced antioxidant defense-related enzymes, namely ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), superoxide dismutase (SOD) and NADPH oxidase. In addition, combining results from transiently overexpressed or silenced ZmMAP65-1a in mesophyll protoplasts, we discovered that ZmMAP65-1a mediated the ABA-induced gene expression and activities of APX and SOD. Surprisingly, silencing of ZmMAP65-1a in mesophyll protoplasts did not alter the gene expression of ZmCCaMK and vice versa in response to ABA. Taken together, our data indicate that water deficit-induced ABA is a key mediator in BR-induced antioxidant defense via ZmMAP65-1a in maize.

  16. Reciprocity between abscisic acid and ethylene at the onset of berry ripening and after harvest

    PubMed Central

    2010-01-01

    Background The ripening of grape berry is generally regulated by abscisic acid (ABA), and has no relationship with ethylene function. However, functional interaction and synergism between ABA and ethylene during the beginning of grape berry ripening (véraison) has been found recently. Results The expressions of VvNCED1 encoding 9-cis-epoxycarotenoid dioxygenase (NCED) and VvGT encoding ABA glucosyltransferase were all increased rapidly at the stage of véraison and reached the highest level at 9th week after full bloom. However, VvCYP1 encoding ABA 8'-hydroxylase and VvβG1 encoding berry β-glucosidase are different, whose expression peak appeared at the 10th week after full bloom and in especial VvβG1 remained at a high level till harvest. The VvACO1 encoding 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase, the VvETR2 (ethylene response 2) and VvCTR1 (constitutive triple response 1) had a transient expression peak at pre-véraison, while the VvEIN4 (ethylene insensitive 4) expression gradually increased from the véraison to one week before harvest stage. The above mentioned changes happened again in the berry after harvest. At one week before véraison, double block treatment with NiCl2 plus 1-methylcyclopropene (1-MCP) not only inhibited the release of ethylene and the expression of related genes but also suppressed the transcription of VvNCED1 and the synthesis of ABA which all might result in inhibiting the fruit ripening onset. Treatment with ABA could relieve the double block and restore fruit ripening course. However, after harvest, double block treatment with NiCl2 plus 1-MCP could not suppress the transcription of VvNCED1 and the accumulation of ABA, and also could not inhibit the start of fruit senescence. Conclusion The trace endogenous ethylene induces the transcription of VvNCED1 and then the generation of ABA followed. Both ethylene and ABA are likely to be important and their interplaying may be required to start the process of berry ripening

  17. Ethylene interacts with abscisic acid to regulate endosperm rupture during germination: a comparative approach using Lepidium sativum and Arabidopsis thaliana.

    PubMed

    Linkies, Ada; Müller, Kerstin; Morris, Karl; Turecková, Veronika; Wenk, Meike; Cadman, Cassandra S C; Corbineau, Françoise; Strnad, Miroslav; Lynn, James R; Finch-Savage, William E; Leubner-Metzger, Gerhard

    2009-12-01

    The micropylar endosperm cap covering the radicle in the mature seeds of most angiosperms acts as a constraint that regulates seed germination. Here, we report on a comparative seed biology study with the close Brassicaceae relatives Lepidium sativum and Arabidopsis thaliana showing that ethylene biosynthesis and signaling regulate seed germination by a mechanism that requires the coordinated action of the radicle and the endosperm cap. The larger seed size of Lepidium allows direct tissue-specific biomechanical, biochemical, and transcriptome analyses. We show that ethylene promotes endosperm cap weakening of Lepidium and endosperm rupture of both species and that it counteracts the inhibitory action of abscisic acid (ABA) on these two processes. Cross-species microarrays of the Lepidium micropylar endosperm cap and the radicle show that the ethylene-ABA antagonism involves both tissues and has the micropylar endosperm cap as a major target. Ethylene counteracts the ABA-induced inhibition without affecting seed ABA levels. The Arabidopsis loss-of-function mutants ACC oxidase2 (aco2; ethylene biosynthesis) and constitutive triple response1 (ethylene signaling) are impaired in the 1-aminocyclopropane-1-carboxylic acid (ACC)-mediated reversion of the ABA-induced inhibition of seed germination. Ethylene production by the ACC oxidase orthologs Lepidium ACO2 and Arabidopsis ACO2 appears to be a key regulatory step. Endosperm cap weakening and rupture are promoted by ethylene and inhibited by ABA to regulate germination in a process conserved across the Brassicaceae.

  18. Hydroxamic acid derivatives of mycophenolic acid inhibit histone deacetylase at the cellular level.

    PubMed

    Batovska, Daniela I; Kim, Dong Hoon; Mitsuhashi, Shinya; Cho, Yoon Sun; Kwon, Ho Jeong; Ubukata, Makoto

    2008-10-01

    Mycophenolic acid (MPA, 1), an inhibitor of IMP-dehydrogenase (IMPDH) and a latent PPARgamma agonist, is used as an effective immunosuppressant for clinical transplantation and recently entered clinical trials in advanced multiple myeloma patients. On the other hand, suberoylanilide hydroxamic acid (SAHA), a non-specific histone deacetylase (HDAC) inhibitor, has been approved for treating cutaneous T-cell lymphoma. MPA seemed to bear a cap, a linker, and a weak metal-binding site as a latent inhibitor of HDAC. Therefore, the hydroxamic acid derivatives of mycophenolic acid having an effective metal-binding site, mycophenolic hydroxamic acid (MPHA, 2), 7-O-acetyl mycophenolic acid (7-O-Ac MPHA, 3), and 7-O-lauroyl mycophenolic hydroxamic acid (7-O-L MPHA, 4) were designed and synthesized. All these compounds inhibited histone deacetylase with IC50 values of 1, 0.9 and 0.5 microM, and cell proliferation at concentrations of 2, 1.5 and 1 microM, respectively. PMID:18838793

  19. Parthenolide and abscisic acid synthesis in feverfew are associated but environmental factors affect them dissimilarly.

    PubMed

    Fonseca, Jorge M; Rushing, James W; Rajapakse, Nihal C; Thomas, Ronald L; Riley, Melissa B

    2005-05-01

    The effect of harvest time, shading prior to harvest and water stress on parthenolide (PRT) concentration in feverfew and its possible connection with the abscisic acid (ABA) pathway were investigated. In plants harvested at different times of the day, acetumar the PRT levels were highest during late afternoon while ABA levels were greatest during morning hours. Shading plants during the afternoon prior to harvest caused a two-fold increase in ABA and no significant difference in PRT levels. ABA was higher in water-stressed plants while PRTcontent increased in plants following recovery from a water stress event. ABA inhibitors, norflurazon, sodium tungstate, naproxen and sodium bisulfite, were used to determine the connection between the biosynthesis of PRTand ABA. Norflurazon and naproxen reduced PRT concentration in cut flowers and in 2-month old plants. Sodium bisulfite and sodium tungstate reduced PRT only in cut flowers. Application of 2,4-D, a promoter of ABA synthesis, to potted plants resulted in a 2.5 fold increase in PRT levels. The inhibition of PRT formation in response to ABA inhibitors and the increase in PRT concentration observed with 2,4-D application indicated that PRT is derived from carotenoid synthesis similarly to ABA and not directly from farnesyl pyrosphosphate (FPP) as suggested for other sesquiterpene Lactones. However, PRT and ABA levels are affected dissimilarly by environmental conditions. The overall results of the study indicated that simple agricultural practices, such as harvesting during afternoon and subjecting plants to a single water stress event, can increase PRT concentration in the final feverfew product with no additional costs of production prior to harvest.

  20. Amino acids inhibit kynurenic acid formation via suppression of kynurenine uptake or kynurenic acid synthesis in rat brain in vitro.

    PubMed

    Sekine, Airi; Okamoto, Misaki; Kanatani, Yuka; Sano, Mitsue; Shibata, Katsumi; Fukuwatari, Tsutomu

    2015-01-01

    The tryptophan metabolite, kynurenic acid (KYNA), is a preferential antagonist of the α7 nicotinic acetylcholine receptor at endogenous brain concentrations. Recent studies have suggested that increase of brain KYNA levels is involved in psychiatric disorders such as schizophrenia and depression. KYNA-producing enzymes have broad substrate specificity for amino acids, and brain uptake of kynurenine (KYN), the immediate precursor of KYNA, is via large neutral amino acid transporters (LAT). In the present study, to find out amino acids with the potential to suppress KYNA production, we comprehensively investigated the effects of proteinogenic amino acids on KYNA formation and KYN uptake in rat brain in vitro. Cortical slices of rat brain were incubated for 2 h in Krebs-Ringer buffer containing a physiological concentration of KYN with individual amino acids. Ten out of 19 amino acids (specifically, leucine, isoleucine, phenylalanine, methionine, tyrosine, alanine, cysteine, glutamine, glutamate, and aspartate) significantly reduced KYNA formation at 1 mmol/L. These amino acids showed inhibitory effects in a dose-dependent manner, and partially inhibited KYNA production at physiological concentrations. Leucine, isoleucine, methionine, phenylalanine, and tyrosine, all LAT substrates, also reduced tissue KYN concentrations in a dose-dependent manner, with their inhibitory rates for KYN uptake significantly correlated with KYNA formation. These results suggest that five LAT substrates inhibit KYNA formation via blockade of KYN transport, while the other amino acids act via blockade of the KYNA synthesis reaction in brain. Amino acids can be a good tool to modulate brain function by manipulation of KYNA formation in the brain. This approach may be useful in the treatment and prevention of neurological and psychiatric diseases associated with increased KYNA levels.

  1. Oleanolic acid and ursolic acid: novel hepatitis C virus antivirals that inhibit NS5B activity.

    PubMed

    Kong, Lingbao; Li, Shanshan; Liao, Qingjiao; Zhang, Yanni; Sun, Ruina; Zhu, Xiangdong; Zhang, Qinghua; Wang, Jun; Wu, Xiaoyu; Fang, Xiaonan; Zhu, Ying

    2013-04-01

    Hepatitis C virus (HCV) infects up to 170 million people worldwide and causes significant morbidity and mortality. Unfortunately, current therapy is only curative in approximately 50% of HCV patients and has adverse side effects, which warrants the need to develop novel and effective antivirals against HCV. We have previously reported that the Chinese herb Fructus Ligustri Lucidi (FLL) directly inhibited HCV NS5B RNA-dependent RNA polymerase (RdRp) activity (Kong et al., 2007). In this study, we found that the FLL aqueous extract strongly suppressed HCV replication. Further high-performance liquid chromatography (HPLC) analysis combined with inhibitory assays indicates that oleanolic acid and ursolic acid are two antiviral components within FLL aqueous extract that significantly suppressed the replication of HCV genotype 1b replicon and HCV genotype 2a JFH1 virus. Moreover, oleanolic acid and ursolic acid exhibited anti-HCV activity at least partly through suppressing HCV NS5B RdRp activity as noncompetitive inhibitors. Therefore, our results for the first time demonstrated that natural products oleanolic acid and ursolic acid could be used as potential HCV antivirals that can be applied to clinic trials either as monotherapy or in combination with other HCV antivirals. PMID:23422646

  2. The Arabidopsis bZIP Gene AtbZIP63 Is a Sensitive Integrator of Transient Abscisic Acid and Glucose Signals1[W][OA

    PubMed Central

    Matiolli, Cleverson Carlos; Tomaz, Juarez Pires; Duarte, Gustavo Turqueto; Prado, Fernanda Manso; Del Bem, Luiz Eduardo Vieira; Silveira, Amanda Bortolini; Gauer, Luciane; Corrêa, Luiz Gustavo Guedes; Drumond, Rodrigo Duarte; Viana, Américo José Carvalho; Di Mascio, Paolo; Meyer, Christian; Vincentz, Michel

    2011-01-01

    Glucose modulates plant metabolism, growth, and development. In Arabidopsis (Arabidopsis thaliana), Hexokinase1 (HXK1) is a glucose sensor that may trigger abscisic acid (ABA) synthesis and sensitivity to mediate glucose-induced inhibition of seedling development. Here, we show that the intensity of short-term responses to glucose can vary with ABA activity. We report that the transient (2 h/4 h) repression by 2% glucose of AtbZIP63, a gene encoding a basic-leucine zipper (bZIP) transcription factor partially involved in the Snf1-related kinase KIN10-induced responses to energy limitation, is independent of HXK1 and is not mediated by changes in ABA levels. However, high-concentration (6%) glucose-mediated repression appears to be modulated by ABA, since full repression of AtbZIP63 requires a functional ABA biosynthetic pathway. Furthermore, the combination of glucose and ABA was able to trigger a synergistic repression of AtbZIP63 and its homologue AtbZIP3, revealing a shared regulatory feature consisting of the modulation of glucose sensitivity by ABA. The synergistic regulation of AtbZIP63 was not reproduced by an AtbZIP63 promoter-5′-untranslated region::β-glucuronidase fusion, thus suggesting possible posttranscriptional control. A transcriptional inhibition assay with cordycepin provided further evidence for the regulation of mRNA decay in response to glucose plus ABA. Overall, these results indicate that AtbZIP63 is an important node of the glucose-ABA interaction network. The mechanisms by which AtbZIP63 may participate in the fine-tuning of ABA-mediated abiotic stress responses according to sugar availability (i.e., energy status) are discussed. PMID:21844310

  3. Influence of abscisic acid and sucrose on somatic embryogenesis in Cactus Copiapoa tenuissima Ritt. forma mostruosa.

    PubMed

    Lema-Rumińska, J; Goncerzewicz, K; Gabriel, M

    2013-01-01

    Having produced the embryos of cactus Copiapoa tenuissima Ritt. forma monstruosa at the globular stage and callus, we investigated the effect of abscisic acid (ABA) in the following concentrations: 0, 0.1, 1, 10, and 100  μ M on successive stages of direct (DSE) and indirect somatic embryogenesis (ISE). In the indirect somatic embryogenesis process we also investigated a combined effect of ABA (0, 0.1, 1  μ M) and sucrose (1, 3, 5%). The results showed that a low concentration of ABA (0-1  μ M) stimulates the elongation of embryos at the globular stage and the number of correct embryos in direct somatic embryogenesis, while a high ABA concentration (10-100  μ M) results in growth inhibition and turgor pressure loss of somatic embryos. The indirect somatic embryogenesis study in this cactus suggests that lower ABA concentrations enhance the increase in calli fresh weight, while a high concentration of 10  μ M ABA or more changes calli color and decreases its proliferation rate. However, in the case of indirect somatic embryogenesis, ABA had no effect on the number of somatic embryos and their maturation. Nevertheless, we found a positive effect of sucrose concentration for both the number of somatic embryos and the increase in calli fresh weight.

  4. Influence of Abscisic Acid and Sucrose on Somatic Embryogenesis in Cactus Copiapoa tenuissima Ritt. forma mostruosa

    PubMed Central

    Lema-Rumińska, J.; Goncerzewicz, K.; Gabriel, M.

    2013-01-01

    Having produced the embryos of cactus Copiapoa tenuissima Ritt. forma monstruosa at the globular stage and callus, we investigated the effect of abscisic acid (ABA) in the following concentrations: 0, 0.1, 1, 10, and 100 μM on successive stages of direct (DSE) and indirect somatic embryogenesis (ISE). In the indirect somatic embryogenesis process we also investigated a combined effect of ABA (0, 0.1, 1 μM) and sucrose (1, 3, 5%). The results showed that a low concentration of ABA (0-1 μM) stimulates the elongation of embryos at the globular stage and the number of correct embryos in direct somatic embryogenesis, while a high ABA concentration (10–100 μM) results in growth inhibition and turgor pressure loss of somatic embryos. The indirect somatic embryogenesis study in this cactus suggests that lower ABA concentrations enhance the increase in calli fresh weight, while a high concentration of 10 μM ABA or more changes calli color and decreases its proliferation rate. However, in the case of indirect somatic embryogenesis, ABA had no effect on the number of somatic embryos and their maturation. Nevertheless, we found a positive effect of sucrose concentration for both the number of somatic embryos and the increase in calli fresh weight. PMID:23843737

  5. Salicylic acid induces mitochondrial injury by inhibiting ferrochelatase heme biosynthesis activity.

    PubMed

    Gupta, Vipul; Liu, Shujie; Ando, Hideki; Ishii, Ryohei; Tateno, Shumpei; Kaneko, Yuki; Yugami, Masato; Sakamoto, Satoshi; Yamaguchi, Yuki; Nureki, Osamu; Handa, Hiroshi

    2013-12-01

    Salicylic acid is a classic nonsteroidal anti-inflammatory drug. Although salicylic acid also induces mitochondrial injury, the mechanism of its antimitochondrial activity is not well understood. In this study, by using a one-step affinity purification scheme with salicylic acid-immobilized beads, ferrochelatase (FECH), a homodimeric enzyme involved in heme biosynthesis in mitochondria, was identified as a new molecular target of salicylic acid. Moreover, the cocrystal structure of the FECH-salicylic acid complex was determined. Structural and biochemical studies showed that salicylic acid binds to the dimer interface of FECH in two possible orientations and inhibits its enzymatic activity. Mutational analysis confirmed that Trp301 and Leu311, hydrophobic amino acid residues located at the dimer interface, are directly involved in salicylic acid binding. On a gel filtration column, salicylic acid caused a shift in the elution profile of FECH, indicating that its conformational change is induced by salicylic acid binding. In cultured human cells, salicylic acid treatment or FECH knockdown inhibited heme synthesis, whereas salicylic acid did not exert its inhibitory effect in FECH knockdown cells. Concordantly, salicylic acid treatment or FECH knockdown inhibited heme synthesis in zebrafish embryos. Strikingly, the salicylic acid-induced effect in zebrafish was partially rescued by FECH overexpression. Taken together, these findings illustrate that FECH is responsible for salicylic acid-induced inhibition of heme synthesis, which may contribute to its antimitochondrial and anti-inflammatory function. This study establishes a novel aspect of the complex pharmacological effects of salicylic acid.

  6. The Arabidopsis MIEL1 E3 ligase negatively regulates ABA signalling by promoting protein turnover of MYB96.

    PubMed

    Lee, Hong Gil; Seo, Pil Joon

    2016-01-01

    The phytohormone abscisic acid (ABA) regulates plant responses to various environmental challenges. Controlled protein turnover is an important component of ABA signalling. Here we show that the RING-type E3 ligase MYB30-INTERACTING E3 LIGASE 1 (MIEL1) regulates ABA sensitivity by promoting MYB96 turnover in Arabidopsis. Germination of MIEL1-deficient mutant seeds is hypersensitive to ABA, whereas MIEL1-overexpressing transgenic seeds are less sensitive. MIEL1 can interact with MYB96, a regulator of ABA signalling, and stimulate its ubiquitination and degradation. Genetic analysis shows that MYB96 is epistatic to MIEL1 in the control of ABA sensitivity in seeds. While MIEL1 acts primarily via MYB96 in seed germination, MIEL1 regulates protein turnover of both MYB96 and MYB30 in vegetative tissues. We find that ABA regulates the expression of MYB30-responsive genes during pathogen infection and this regulation is partly dependent on MIEL1. These results suggest that MIEL1 may facilitate crosstalk between ABA and biotic stress signalling. PMID:27615387

  7. The Arabidopsis MIEL1 E3 ligase negatively regulates ABA signalling by promoting protein turnover of MYB96

    PubMed Central

    Lee, Hong Gil; Seo, Pil Joon

    2016-01-01

    The phytohormone abscisic acid (ABA) regulates plant responses to various environmental challenges. Controlled protein turnover is an important component of ABA signalling. Here we show that the RING-type E3 ligase MYB30-INTERACTING E3 LIGASE 1 (MIEL1) regulates ABA sensitivity by promoting MYB96 turnover in Arabidopsis. Germination of MIEL1-deficient mutant seeds is hypersensitive to ABA, whereas MIEL1-overexpressing transgenic seeds are less sensitive. MIEL1 can interact with MYB96, a regulator of ABA signalling, and stimulate its ubiquitination and degradation. Genetic analysis shows that MYB96 is epistatic to MIEL1 in the control of ABA sensitivity in seeds. While MIEL1 acts primarily via MYB96 in seed germination, MIEL1 regulates protein turnover of both MYB96 and MYB30 in vegetative tissues. We find that ABA regulates the expression of MYB30-responsive genes during pathogen infection and this regulation is partly dependent on MIEL1. These results suggest that MIEL1 may facilitate crosstalk between ABA and biotic stress signalling. PMID:27615387

  8. Effect of Paclobutrazol on Water Stress-Induced Abscisic Acid in Apple Seedling Leaves

    PubMed Central

    Wang, Shiow Y.; Sun, Tung; Ji, Zuo L.; Faust, Miklos

    1987-01-01

    Abscisic acid (ABA) was quantitated by enzyme-linked immunosorbent assay (ELISA) in water-stressed leaves from control apple seedlings, and also from apple seedlings treated for 28 days with paclobutrazol ([2RS, 3RS]-1-[4-chlorophenyl]-4,4-dimethyl-2-[1,2,4-triazol-1-yl] pentan-3-ol). The ELISA quantitative estimates were also validated by gas chromatography-electron capture detector and lettuce seed germination inhibition bioassay. Paclobutrazol treatment reduced endogenous ABA levels by about one-third, and prevented the marked accumulation of water-stress-induced ABA that occurred in untreated seedlings. The presence of ABA in the apple leaf extracts was confirmed by gas chromatography-mass spectrometry. PMID:16665559

  9. Liver acid sphingomyelinase inhibits growth of metastatic colon cancer.

    PubMed

    Osawa, Yosuke; Suetsugu, Atsushi; Matsushima-Nishiwaki, Rie; Yasuda, Ichiro; Saibara, Toshiji; Moriwaki, Hisataka; Seishima, Mitsuru; Kozawa, Osamu

    2013-02-01

    Acid sphingomyelinase (ASM) regulates the homeostasis of sphingolipids, including ceramides and sphingosine-1-phosphate (S1P). These sphingolipids regulate carcinogenesis and proliferation, survival, and apoptosis of cancer cells. However, the role of ASM in host defense against liver metastasis remains unclear. In this study, the involvement of ASM in liver metastasis of colon cancer was examined using Asm-/- and Asm+/+ mice that were inoculated with SL4 colon cancer cells to produce metastatic liver tumors. Asm-/- mice demonstrated enhanced tumor growth and reduced macrophage accumulation in the tumor, accompanied by decreased numbers of hepatic myofibroblasts (hMFs), which express tissue inhibitor of metalloproteinase 1 (TIMP1), around the tumor margin. Tumor growth was increased by macrophage depletion or by Timp1 deficiency, but was decreased by hepatocyte-specific ASM overexpression, which was associated with increased S1P production. S1P stimulated macrophage migration and TIMP1 expression in hMFs in vitro. These findings indicate that ASM in the liver inhibits tumor growth through cytotoxic macrophage accumulation and TIMP1 production by hMFs in response to S1P. Targeting ASM may represent a new therapeutic strategy for treating liver metastasis of colon cancer.

  10. Feedback Regulation of ABA Signaling and Biosynthesis by a bZIP Transcription Factor Targets Drought-Resistance-Related Genes1[OPEN

    PubMed Central

    Tang, Ning; Yang, Jun; Peng, Lei; Ma, Siqi; Xu, Yan; Li, Guoliang

    2016-01-01

    The OsbZIP23 transcription factor has been characterized for its essential role in drought resistance in rice (Oryza sativa), but the mechanism is unknown. In this study, we first investigated the transcriptional activation of OsbZIP23. A homolog of SnRK2 protein kinase (SAPK2) was found to interact with and phosphorylate OsbZIP23 for its transcriptional activation. SAPK2 also interacted with OsPP2C49, an ABI1 homolog, which deactivated the SAPK2 to inhibit the transcriptional activation activity of OsbZIP23. Next, we performed genome-wide identification of OsbZIP23 targets by immunoprecipitation sequencing and RNA sequencing analyses in the OsbZIP23-overexpression, osbzip23 mutant, and wild-type rice under normal and drought stress conditions. OsbZIP23 directly regulates a large number of reported genes that function in stress response, hormone signaling, and developmental processes. Among these targets, we found that OsbZIP23 could positively regulate OsPP2C49, and overexpression of OsPP2C49 in rice resulted in significantly decreased sensitivity of the abscisic acid (ABA) response and rapid dehydration. Moreover, OsNCED4 (9-cis-epoxycarotenoid dioxygenase4), a key gene in ABA biosynthesis, was also positively regulated by OsbZIP23. Together, our results suggest that OsbZIP23 acts as a central regulator in ABA signaling and biosynthesis, and drought resistance in rice. PMID:27325665

  11. Ethylene Interacts with Abscisic Acid to Regulate Endosperm Rupture during Germination: A Comparative Approach Using Lepidium sativum and Arabidopsis thaliana[W][OA

    PubMed Central

    Linkies, Ada; Müller, Kerstin; Morris, Karl; Turečková, Veronika; Wenk, Meike; Cadman, Cassandra S.C.; Corbineau, Françoise; Strnad, Miroslav; Lynn, James R.; Finch-Savage, William E.; Leubner-Metzger, Gerhard

    2009-01-01

    The micropylar endosperm cap covering the radicle in the mature seeds of most angiosperms acts as a constraint that regulates seed germination. Here, we report on a comparative seed biology study with the close Brassicaceae relatives Lepidium sativum and Arabidopsis thaliana showing that ethylene biosynthesis and signaling regulate seed germination by a mechanism that requires the coordinated action of the radicle and the endosperm cap. The larger seed size of Lepidium allows direct tissue-specific biomechanical, biochemical, and transcriptome analyses. We show that ethylene promotes endosperm cap weakening of Lepidium and endosperm rupture of both species and that it counteracts the inhibitory action of abscisic acid (ABA) on these two processes. Cross-species microarrays of the Lepidium micropylar endosperm cap and the radicle show that the ethylene-ABA antagonism involves both tissues and has the micropylar endosperm cap as a major target. Ethylene counteracts the ABA-induced inhibition without affecting seed ABA levels. The Arabidopsis loss-of-function mutants ACC oxidase2 (aco2; ethylene biosynthesis) and constitutive triple response1 (ethylene signaling) are impaired in the 1-aminocyclopropane-1-carboxylic acid (ACC)-mediated reversion of the ABA-induced inhibition of seed germination. Ethylene production by the ACC oxidase orthologs Lepidium ACO2 and Arabidopsis ACO2 appears to be a key regulatory step. Endosperm cap weakening and rupture are promoted by ethylene and inhibited by ABA to regulate germination in a process conserved across the Brassicaceae. PMID:20023197

  12. Cellobionic acid inhibition of cellobiohydrolase I and cellobiose dehydrogenase

    Technology Transfer Automated Retrieval System (TEKTRAN)

    End-product inhibition by cellobiose and glucose is a rate-limiting factor in cellulose hydrolysis by cellulases. While cellobiose and glucose inhibition have been extensively investigated, cellobionate inhibition has been minimally studied despite the discovery that accessory proteins such as cello...

  13. Fish oil constituent docosahexa-enoic acid selectively inhibits growth of human papillomavirus immortalized keratinocytes.

    PubMed

    Chen, D; Auborn, K

    1999-02-01

    The omega-3-fatty acids inhibit proliferation of breast cancer cells whereas omega-6-fatty acids stimulate growth. In this study, we examined effects of these fatty acids on human pre-cancerous cells. Cervical keratinocytes, immortalized with the oncogenic human papillomavirus (HPV) type 16, were treated with linoleic acid, an omega-6-fatty acid, and the omega-3-fatty acids, eicosapentaenoic and docosahexaenoic acids. Using both cell counts and bromodeoxyuridine incorporation, docosahexaenoic acid inhibited growth of these cells to a greater extent than eicosapenta-enoic acid. Linoleic acid had no effect. The effect of docosahexaenoic acid was dose dependent and caused growth arrest. Docosahexaenoic acid inhibited growth of HPV16 immortalized foreskin keratinocytes and laryngeal keratinocytes grown from explants of benign tumors caused by papillomavirus, but had no effect on normal foreskin and laryngeal keratinocytes. Docosahexaenoic acid inhibited growth in the presence of estradiol, a growth stimulator for these cells. Indomethacin, a cyclooxygenase inhibitor like docosahexaenoic acid, had only minimal effect on growth. Alpha-tocopherol, a peroxidation inhibitor, abrogated effects of docosahexaenoic acid implying that inhibitory effects were via lipid peroxidation. PMID:10069461

  14. Wall teichoic acid protects Staphylococcus aureus from inhibition by Congo red and other dyes

    PubMed Central

    Suzuki, Takashi; Campbell, Jennifer; Kim, Younghoon; Swoboda, Jonathan G.; Mylonakis, Eleftherios; Walker, Suzanne; Gilmore, Michael S.

    2012-01-01

    Objectives Polyanionic polymers, including lipoteichoic acid and wall teichoic acid, are important determinants of the charged character of the staphylococcal cell wall. This study was designed to investigate the extent to which teichoic acid contributes to protection from anionic azo dyes and to identify barriers to drug penetration for development of new antibiotics for multidrug-resistant Staphylococcus aureus infection. Methods We studied antimicrobial activity of azo dyes against S. aureus strains with or without inhibition of teichoic acid in vitro and in vivo. Results We observed that inhibition of wall teichoic acid expression resulted in an ∼1000-fold increase in susceptibility to azo dyes such as Congo red, reducing its MIC from >1024 to <4 mg/L. Sensitization occurred when the first step in the wall teichoic acid pathway, catalysed by TarO, was inhibited either by mutation or by chemical inhibition. In contrast, genetic blockade of lipoteichoic acid biosynthesis did not confer Congo red susceptibility. Based on this finding, combination therapy was tested using the highly synergistic combination of Congo red plus tunicamycin at sub-MIC concentrations (to inhibit wall teichoic acid biosynthesis). The combination rescued Caenorhabditis elegans from a lethal challenge of S. aureus. Conclusions Our studies show that wall teichoic acid confers protection to S. aureus from anionic azo dyes and related compounds, and its inhibition raises the prospect of development of new combination therapies based on this inhibition. PMID:22615298

  15. Loss of heterophylly in aquatic plants: not ABA-mediated stress but exogenous ABA treatment induces stomatal leaves in Potamogeton perfoliatus.

    PubMed

    Iida, Satoko; Ikeda, Miyuki; Amano, Momoe; Sakayama, Hidetoshi; Kadono, Yasuro; Kosuge, Keiko

    2016-09-01

    Heterophyllous aquatic plants produce aerial (i.e., floating and terrestrial) and submerged leaves-the latter lack stomata-while homophyllous plants contain only submerged leaves, and cannot survive on land. To identify whether differences in morphogenetic potential and/or physiological stress responses are responsible for variation in phenotypic plasticity between two plants types, responses to abscisic acid (ABA) and salinity stress were compared between the closely related, but ecologically diverse pondweeds, Potamogeton wrightii (heterophyllous) and P. perfoliatus (homophyllous). The ABA-treated (1 or 10 μM) P. wrightii plants exhibited heterophylly and produced leaves with stomata. The obligate submerged P. perfoliatus plants were able to produce stomata on their leaves, but there were no changes to leaf shape, and stomatal production occurred only at a high ABA concentration (10 μM). Under salinity stress conditions, only P. wrightii leaves formed stomata. Additionally, the expression of stress-responsive NCED genes, which encode a key enzyme in ABA biosynthesis, was consistently up-regulated in P. wrightii, but only temporarily in P. perfoliatus. The observed species-specific gene expression patterns may be responsible for the induction or suppression of stomatal production during exposure to salinity stress. These results suggest that the two Potamogeton species have an innate morphogenetic ability to form stomata, but the actual production of stomata depends on ABA-mediated stress responses specific to each species and habitat. PMID:27324202

  16. Caffeic acid phenethyl ester inhibits liver fibrosis in rats

    PubMed Central

    Li, Mei; Wang, Xiu-Fang; Shi, Juan-Juan; Li, Ya-Ping; Yang, Ning; Zhai, Song; Dang, Shuang-Suo

    2015-01-01

    AIM: To investigate the hepatoprotective effects and antioxidant activity of caffeic acid phenethyl ester (CAPE) in rats with liver fibrosis. METHODS: A total of 75 male Sprague-Dawley rats were randomly assigned to seven experimental groups: a normal group (n = 10), a vehicle group (n = 10), a model group (n = 15), a vitamin E group (n = 10), and three CAPE groups (CAPE 3, 6 and 12 mg/kg, n = 10, respectively). Liver fibrosis was induced in rats by injecting CCl4 subcutaneously, feeding with high fat forage, and administering 30% alcohol orally for 10 wk. Concurrently, CAPE (3, 6 and 12 mg/kg) was intraperitoneally administered daily for 10 wk. After that, serum total bilirubin (TBil), aminotransferase (ALT) and aspartate aminotransferase (AST) levels were measured to assess hepatotoxicity. To investigate antioxidant activity of CAPE, malondialdehyde (MDA), glutathione (GSH) levels, catalase (CAT) and superoxide dismutase (SOD) activities in liver tissue were determined. Moreover, the effect of CAPE on α-smooth muscle actin (α-SMA), a characteristic hallmark of activated hepatic stellate cells (HSCs), and NF-E2-related factor 2 (Nrf2), a key transcription factor for antioxidant systems, was investigated by immunohistochemistry. RESULTS: Compared to the model group, intraperitoneal administration of CAPE decreased TBil, ALT, and AST levels in liver fibrosis rats (P < 0.05), while serum TBil was decreased by CAPE in a dose-dependent manner. In addition, the liver hydroxyproline contents in both the 6 and 12 mg/kg CAPE groups were markedly lower than that in the model group (P < 0.05 and P < 0.001, respectively). CAPE markedly decreased MDA levels and, in turn, increased GSH levels, as well as CAT and SOD activities in liver fibrosis rats compared to the model group (P < 0.05). Moreover, CAPE effectively inhibited α-SMA expression while increasing Nrf2 expression compared to the model group (P < 0.01). CONCLUSION: The protective effects of CAPE against liver

  17. 3,5-Dihydroxybenzoic acid, a specific agonist for hydroxycarboxylic acid 1, inhibits lipolysis in adipocytes.

    PubMed

    Liu, Changlu; Kuei, Chester; Zhu, Jessica; Yu, Jingxue; Zhang, Li; Shih, Amy; Mirzadegan, Taraneh; Shelton, Jonathan; Sutton, Steven; Connelly, Margery A; Lee, Grace; Carruthers, Nicholas; Wu, Jiejun; Lovenberg, Timothy W

    2012-06-01

    Niacin raises high-density lipoprotein and lowers low-density lipoprotein through the activation of the β-hydroxybutyrate receptor hydroxycarboxylic acid 2 (HCA2) (aka GPR109a) but with an unwanted side effect of cutaneous flushing caused by vascular dilation because of the stimulation of HCA2 receptors in Langerhans cells in skin. HCA1 (aka GPR81), predominantly expressed in adipocytes, was recently identified as a receptor for lactate. Activation of HCA1 in adipocytes by lactate results in the inhibition of lipolysis, suggesting that agonists for HCA1 may be useful for the treatment of dyslipidemia. Lactate is a metabolite of glucose, suggesting that HCA1 may also be involved in the regulation of glucose metabolism. The low potency of lactate to activate HCA1, coupled with its fast turnover rate in vivo, render it an inadequate tool for studying the biological role of lactate/HCA1 in vivo. In this article, we demonstrate the identification of 3-hydroxybenzoic acid (3-HBA) as an agonist for both HCA2 and HCA1, whereas 3,5-dihydroxybenzoic acid (3,5-DHBA) is a specific agonist for only HCA1 (EC(50) ∼150 μM). 3,5-DHBA inhibits lipolysis in wild-type mouse adipocytes but not in HCA1-deficient adipocytes. Therefore, 3,5-DHBA is a useful tool for the in vivo study of HCA1 function and offers a base for further HCA1 agonist design. Because 3-HBA and 3,5-DHBA are polyphenolic acids found in many natural products, such as fruits, berries, and coffee, it is intriguing to speculate that other heretofore undiscovered natural substances may have therapeutic benefits.

  18. Abscisic acid biosynthesis in water-stressed leaves

    SciTech Connect

    Li, Yi.

    1989-01-01

    Although abscisic acid (ABA) was discovered 30 years ago, very little is known about its biosynthetic pathway in higher plants. Two hypotheses have been proposed: (i) a direct pathway involving only C-15 intermediates like farnesyl pyrophosphate, (ii) an indirect pathway involving C-40 intermediates like the xanthophylls. When {sup 14}CO{sub 2} was fed into greened bean plants, the {sup 14}C specific activity of ABA was always lower than those in xanthophylls, such as violaxanthin and lutein, regardless of {sup 12}CO{sub 2} chase periods. The ABA accumulation in green leaves was not affected by fluridone when plants were stressed once, but the {sup 14}C incorporation into ABA was inhibited to the same extent as those of xanthophylls. The incorporation of {sup 18}O into the ABA ring when violaxanthin was labeled by {sup 18}O in vivo via the violaxanthin cycle indicates that at least a portion of ABA was derived from {sup 18}O-labeled violaxanthin during water stress.

  19. Simultaneous inhibition of carbon and nitrogen mineralization in a forest soil by simulated acid precipitation

    SciTech Connect

    Klein, T.M.; Novick, N.J.; Kreitinger, J.P.; Alexander, M.

    1984-06-01

    One method to simulate the long-term exposure of soil to acid rain involves the addition of single doses of concentrated acid. The inhibition of carbon mineralization accompanied by a stimulation of nitrogen mineralization may result from this severe, unnatural treatment. The present study was designed to determine whether the inhibition of carbon mineralization and the accompanying enhanced nitrogen mineralization would occur when soils are treated with more dilute acid for long periods of time, as takes place in nature.

  20. An unusual abscisic acid and gibberellic acid synergism increases somatic embryogenesis, facilitates its genetic analysis and improves transformation in Medicago truncatula.

    PubMed

    Nolan, Kim E; Song, Youhong; Liao, Siyang; Saeed, Nasir A; Zhang, Xiyi; Rose, Ray J

    2014-01-01

    Somatic embryogenesis (SE) can be readily induced in leaf explants of the Jemalong 2HA genotype of the model legume Medicago truncatula by auxin and cytokinin, but rarely in wild-type Jemalong. Gibberellic acid (GA), a hormone not included in the medium, appears to act in Arabidopsis as a repressor of the embryonic state such that low ABA (abscisic acid): GA ratios will inhibit SE. It was important to evaluate the GA effect in M. truncatula in order to formulate generic SE mechanisms, given the Arabidopsis information. It was surprising to find that low ABA:GA ratios in M. truncatula acted synergistically to stimulate SE. The unusual synergism between GA and ABA in inducing SE has utility in improving SE for regeneration and transformation in M. truncatula. Expression of genes previously shown to be important in M. truncatula SE was not increased. In investigating genes previously studied in GA investigations of Arabidopsis SE, there was increased expression of GA2ox and decreased expression of PICKLE, a negative regulator of SE in Arabidopsis. We suggest that in M. truncatula there are different ABA:GA ratios required for down-regulating the PICKLE gene, a repressor of the embryonic state. In M. truncatula it is a low ABA:GA ratio while in Arabidopsis it is a high ABA:GA ratio. In different species the expression of key genes is probably related to differences in how the hormone networks optimise their expression. PMID:24937316

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2016-08-20

    Grapevine buds (Vitis vinifera L) enter endodormancy (ED) after perceiving the short-day (SD) photoperiod signal and undergo metabolic changes that allow them to survive the winter temperatures. In the present study, we observed an inverse relationship between the depth of ED and the respiration rate of grapevine buds. Moreover, the respiration of dormant and non-dormant buds differed in response to temperature and glucose, two stimuli that normally increase respiration in plant tissues. While respiration in non-dormant buds rose sharply in response to both stimuli, respiration in dormant buds was only slightly affected. This suggests that a metabolic inhibitor is present. Here, we propose that the plant hormone abscisic acid (ABA) could be this inhibitor. ABA inhibits respiration in non-dormant buds and represses the expression of respiratory genes, such as ALTERNATIVE NADH DEHYDROGENASE (VaND1, VvaND2), CYTOCHROME OXIDASE (VvCOX6) and CYTOCHROME C (VvCYTC), and induces the expression of VvSnRK1, a gene encoding a member of a highly conserved family of protein kinases that act as energy sensors and regulate gene expression in response to energy depletion. In addition to inducing ED the SD-photoperiod up-regulated the expression of VvNCED, a gene that encodes a key enzyme in ABA synthesis. Taken together, these results suggest that ABA through the mediation of VvSnRK1, could play a key role in the regulation of the metabolic changes accompanying the entry into ED of grapevine buds. PMID:27448722

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

  5. Hydrogen peroxide mediates abscisic acid-induced HSP70 accumulation and heat tolerance in grafted cucumber plants.

    PubMed

    Li, Hao; Liu, Shan-Shan; Yi, Chang-Yu; Wang, Feng; Zhou, Jie; Xia, Xiao-Jian; Shi, Kai; Zhou, Yan-Hong; Yu, Jing-Quan

    2014-12-01

    Root-shoot communications play important roles in plant stress responses. Here, we examined the roles of root-sourced signals in the shoot response to heat in cucumber plants. Cucumber plants grafted onto their own roots and luffa roots were exposed to aerial and root-zone heat to examine their tolerance by assessing the levels of oxidative stress, PSII photoinhibition, accumulation of abscisic acid (ABA), H2 O2 and heat shock protein (HSP) 70 using immunoblotting, chlorophyll fluorescence, immunoassay, CeCl3 staining and Western blotting, respectively. Grafting onto the luffa rootstock enhanced the shoot tolerance to the heat. This enhanced tolerance was associated with increased accumulation of ABA and apoplastic H2 O2 , RBOH transcripts and HSP70 expression and a decrease in oxidative stress in the shoots. The increases in the ABA and H2 O2 concentrations in the shoots were attributed to an increase in ABA transport from roots and an increase in ABA biosynthesis in the shoots when the root-zone and shoots were heat stressed, respectively. Inhibition of H2 O2 accumulation compromised luffa rootstock-induced HSP70 expression and heat tolerance. These results suggest that, under heat stress, ABA triggers the expression of HSP70 in an apoplastic H2 O2 -dependent manner, implicating the role of an ABA-dependent H2 O2 -driven mechanism in a systemic response involving root-shoot communication.

  6. Registration of Zak ERA8 Soft White Spring Wheat Germplasm with Enhanced Response to ABA and Increased Seed Dormancy

    PubMed Central

    Martinez, Shantel A.; Schramm, Elizabeth C.; Harris, Tracy J.; Kidwell, Kimberlee K.; Garland-Campbell, Kimberly; Steber, Camille M.

    2014-01-01

    Zak ERA8 (ENHANCED RESPONSE to ABA8) (Reg. No. GP-966, PI 669443) is a unique line derived from soft white spring wheat (Triticum aestivum L.) cultivar Zak that has increased seed dormancy but after-ripens within 10 to 16 wk. The goal in developing this germplasm was to use increased seed dormancy to improve tolerance to preharvest sprouting, a problem that can cause severe economic losses. This germplasm was developed by USDA–ARS, Pullman, WA, in collaboration with Washington State University. Zak ERA8was tested under experimental number 60.1.27.10. The ERA8mutation was generated by chemical mutagenesis followed by selection for the inability to germinate on abscisic acid (ABA) concentrations too low to inhibit wild-type Zak seed germination. The semidominant Zak ERA8 line has been backcrossed twice to wild-type Zak. Following the first backcross, Zak ERA8 showed similar morphological and grain quality traits to the original Zak cultivar. PMID:25580180

  7. PHO1 expression in guard cells mediates the stomatal response to abscisic acid in Arabidopsis.

    PubMed

    Zimmerli, Céline; Ribot, Cécile; Vavasseur, Alain; Bauer, Hubert; Hedrich, Rainer; Poirier, Yves

    2012-10-01

    Stomatal opening and closing are driven by ion fluxes that cause changes in guard cell turgor and volume. This process is, in turn, regulated by environmental and hormonal signals, including light and the phytohormone abscisic acid (ABA). Here, we present genetic evidence that expression of PHO1 in guard cells of Arabidopsis thaliana is required for full stomatal responses to ABA. PHO1 is involved in the export of phosphate into the root xylem vessels and, as a result, the pho1 mutant is characterized by low shoot phosphate levels. In leaves, PHO1 was found expressed in guard cells and up-regulated following treatment with ABA. The pho1 mutant was unaffected in production of reactive oxygen species following ABA treatment, and in stomatal movements in response to light cues, high extracellular calcium, auxin, and fusicoccin. However, stomatal movements in response to ABA treatment were severely impaired, both in terms of induction of closure and inhibition of opening. Micro-grafting a pho1 shoot scion onto wild-type rootstock resulted in plants with normal shoot growth and phosphate content, but failed to restore normal stomatal response to ABA treatment. PHO1 knockdown using RNA interference specifically in guard cells of wild-type plants caused a reduced stomatal response to ABA. In agreement, specific expression of PHO1 in guard cells of pho1 plants complemented the mutant guard cell phenotype and re-established ABA sensitivity, although full functional complementation was dependent on shoot phosphate sufficiency. Together, these data reveal an important role for phosphate and the action of PHO1 in the stomatal response to ABA.

  8. Mechanism of specific inhibition of phototropism by phenylacetic acid in corn seedling

    SciTech Connect

    Vierstra, R.D.; Poff, K.L.

    1981-05-01

    Using geotropism as a control for phototropism, compounds similar to phenylacetic acid that phototreact with flavins and/or have auxin-like activity were examined for their ability to specifically inhibit phototropism in corn seedlings using geotropism as a control. Results using indole-3-acetic acid, napthalene-1-acetic acid, naphthalene-2-acetic acid, phenylacetic acid, and ..beta..-phenylpyruvic acid suggest that such compounds will specifically inhibit phototropism primarily because of their photoreactivity with flavins and not their auxin activity. In addition, the in vivo concentration of phenylacetic acid required to induce specificity was well below that required to stimulate coleoptile growth. Estimates of the percentage of photoreceptor pigment inactivated by phenylacetic acid (>10%) suggest that phenylacetic acid could be used to photoaffinity label the flavoprotein involved in corn seedling phototropism.

  9. Inhibition of germination of dormant barley (Hordeum vulgare L.) grains by blue light as related to oxygen and hormonal regulation.

    PubMed

    Hoang, Hai Ha; Sechet, Julien; Bailly, Christophe; Leymarie, Juliette; Corbineau, Françoise

    2014-06-01

    Germination of primary dormant barley grains is promoted by darkness and temperatures below 20 °C, but is strongly inhibited by blue light. Exposure under blue light at 10 °C for periods longer than five days, results in a progressive inability to germinate in the dark, considered as secondary dormancy. We demonstrate that the inhibitory effect of blue light is reinforced in hypoxia. The inhibitory effect of blue light is associated with an increase in embryo abscisic acid (ABA) content (by 3.5- to 3.8-fold) and embryo sensitivity to both ABA and hypoxia. Analysis of expression of ABA metabolism genes shows that increase in ABA mainly results in a strong increase in HvNCED1 and HvNCED2 expression, and a slight decrease in HvABA8'OH-1. Among the gibberellins (GA) metabolism genes examined, blue light decreases the expression of HvGA3ox2, involved in GA synthesis, increases that of GA2ox3 and GA2ox5, involved in GA catabolism, and reduces the GA signalling evaluated by the HvExpA11 expression. Expression of secondary dormancy is associated with maintenance of high embryo ABA content and a low HvExpA11 expression. The partial reversion of the inhibitory effect of blue light by green light also suggests that cryptochrome might be involved in this hormonal regulation. PMID:24256416

  10. Inhibition of germination of dormant barley (Hordeum vulgare L.) grains by blue light as related to oxygen and hormonal regulation.

    PubMed

    Hoang, Hai Ha; Sechet, Julien; Bailly, Christophe; Leymarie, Juliette; Corbineau, Françoise

    2014-06-01

    Germination of primary dormant barley grains is promoted by darkness and temperatures below 20 °C, but is strongly inhibited by blue light. Exposure under blue light at 10 °C for periods longer than five days, results in a progressive inability to germinate in the dark, considered as secondary dormancy. We demonstrate that the inhibitory effect of blue light is reinforced in hypoxia. The inhibitory effect of blue light is associated with an increase in embryo abscisic acid (ABA) content (by 3.5- to 3.8-fold) and embryo sensitivity to both ABA and hypoxia. Analysis of expression of ABA metabolism genes shows that increase in ABA mainly results in a strong increase in HvNCED1 and HvNCED2 expression, and a slight decrease in HvABA8'OH-1. Among the gibberellins (GA) metabolism genes examined, blue light decreases the expression of HvGA3ox2, involved in GA synthesis, increases that of GA2ox3 and GA2ox5, involved in GA catabolism, and reduces the GA signalling evaluated by the HvExpA11 expression. Expression of secondary dormancy is associated with maintenance of high embryo ABA content and a low HvExpA11 expression. The partial reversion of the inhibitory effect of blue light by green light also suggests that cryptochrome might be involved in this hormonal regulation.

  11. Changes in the Levels of Calmodulin and of a Calmodulin Inhibitor in the Early Phases of Radish (Raphanus sativus L.) Seed Germination: Effects of Aba and Fusicoccin.

    PubMed

    Cocucci, M; Negrini, N

    1988-11-01

    An inhibitor of Ca(2+)-calmodulin (Cam)-dependent brain phosphodiesterase was present in the soluble fraction of embryo axes from ungerminated radish (Raphanus sativus L.) seeds. This inhibitor is a Ca(2+)-dependent, Cam-binding protein; in fact: (a) its effect was strongly reduced by treatment with proteases; (b) the inhibition was counteracted by Cam but not by Ca(2+); (c) on gel filtration in the presence of Ca(2+), Cam co-chromatographed with the inhibitor. The inhibitor is heat stable and positively charged at pH 7.5. During early phases of germination, the fresh weight and the levels of DNA and RNA of embryo axes increased, the level of the inhibitor decreased, and the level of Cam increased. Abscisic acid (ABA) inhibited germination, the decrease of inhibitor, and the increase of Cam. Fusicoccin (FC) stimulated the increase in fresh weight but not the increase in the RNA and DNA levels; in this condition, the inhibitor level decreased and the increase in Cam level was higher than in the control. In the presence of both ABA and FC, there was an increase in fresh weight not accompanied by an increase in DNA and RNA levels; Cam increased and, on a fresh weight basis, reached the value of the control. These results indicate that the Ca(2+)-Cam system was activated in early germination of radish seeds by an increase in Cam and a decrease in the inhibitor levels, that FC, probably through the activation of membrane functions, increased Cam level, and that the ABA inhibition on germination was not mediated by the Ca(2+)-Cam system.

  12. Interplay between ABA and phospholipases A(2) and D in the response of citrus fruit to postharvest dehydration.

    PubMed

    Romero, Paco; Gandía, Mónica; Alférez, Fernando

    2013-09-01

    The interplay between abscisic acid (ABA) and phospholipases A2 and D (PLA2 and PLD) in the response of citrus fruit to water stress was investigated during postharvest by using an ABA-deficient mutant from 'Navelate' orange named 'Pinalate'. Fruit from both varieties harvested at two different maturation stages (mature-green and full-mature) were subjected to prolonged water loss inducing stem-end rind breakdown (SERB) in full-mature fruit. Treatment with PLA2 inhibitor aristolochic acid (AT) and PLD inhibitor lysophosphatidylethanolamine (LPE) reduced the disorder in both varieties, suggesting that phospholipid metabolism is involved in citrus peel quality. Expression of CsPLDα and CsPLDβ, and CssPLA2α and CssPLA2β was studied by real-time RT-PCR during water stress and in response to ABA. CsPLDα expression increased in mature-green fruit from 'Navelate' but not in 'Pinalate' and ABA did not counteract this effect. ABA enhanced repression of CsPLDα in full-mature fruit. CsPLDβ gene expression decreased in mature-green 'Pinalate', remained unchanged in 'Navelate' and was induced in full-mature fruit from both varieties. CssPLA2α expression increased in mature-green fruit from both varieties whereas in full-mature fruit only increased in 'Navelate'. CssPLA2β expression increased in mature-green flavedo from both varieties, but in full-mature fruit remained steady in 'Navelate' and barely increased in 'Pinalate' fruit. ABA reduced expression in both after prolonged storage. Responsiveness to ABA increased with maturation. Our results show interplay between PLA2 and PLD and suggest that ABA action is upstream phospholipase activation. Response to ABA during water stress in citrus is regulated during fruit maturation and involves membrane phospholipid degradation.

  13. Positive feedback regulation of a Lycium chinense-derived VDE gene by drought-induced endogenous ABA, and over-expression of this VDE gene improve drought-induced photo-damage in Arabidopsis.

    PubMed

    Guan, Chunfeng; Ji, Jing; Zhang, Xuqiang; Li, Xiaozhou; Jin, Chao; Guan, Wenzhu; Wang, Gang

    2015-03-01

    Violaxanthin de-epoxidase (VDE) plays an important role in protecting the photosynthetic apparatus from photo-damage by dissipating excessively absorbed light energy as heat, via the conversion of violaxanthin (V) to intermediate product antheraxanthin (A) and final product zeaxanthin (Z) under light stress. We have cloned a VDE gene (LcVDE) from Lycium chinense, a deciduous woody perennial halophyte, which can grow in a large variety of soil types. The amino acid sequence of LcVDE has high homology with VDEs in other plants. Under drought stress, relative expression of LcVDE and the de-epoxidation ratio (Z+0.5A)/(V+A+Z) increased rapidly, and non-photochemical quenching (NPQ) also rose. Interestingly, these elevations induced by drought stress were reduced by the topical administration of abamine SG, a potent ABA inhibitor via inhibition of NCED in the ABA synthesis pathway. Until now, little has been done to explore the relationship between endogenous ABA and the expression of VDE genes. Since V serves as a common precursor for ABA, these data support the possible involvement of endogenous ABA in the positive feedback regulation of LcVDE gene expression in L. chinense under drought stress. Moreover, the LcVDE may be involved in modulating the level of photosynthesis damage caused by drought stress. Furthermore, the ratio of (Z+0.5A)/(V+A+Z) and NPQ increased more in transgenic Arabidopsis over-expressing LcVDE gene than the wild types under drought stress. The maximum quantum yield of primary photochemistry of PSII (Fv/Fm) in transgenic Arabidopsis decreased more slowly during the stressed period than that in wild types under the same conditions. Furthermore, transgenic Arabidopsis over-expressing LcVDE showed increased tolerance to drought stress.

  14. Tomato PYR/PYL/RCAR abscisic acid receptors show high expression in root, differential sensitivity to the abscisic acid agonist quinabactin, and the capability to enhance plant drought resistance.

    PubMed

    González-Guzmán, Miguel; Rodríguez, Lesia; Lorenzo-Orts, Laura; Pons, Clara; Sarrión-Perdigones, Alejandro; Fernández, Maria A; Peirats-Llobet, Marta; Forment, Javier; Moreno-Alvero, Maria; Cutler, Sean R; Albert, Armando; Granell, Antonio; Rodríguez, Pedro L

    2014-08-01

    Abscisic acid (ABA) plays a crucial role in the plant's response to both biotic and abiotic stress. Sustainable production of food faces several key challenges, particularly the generation of new varieties with improved water use efficiency and drought tolerance. Different studies have shown the potential applications of Arabidopsis PYR/PYL/RCAR ABA receptors to enhance plant drought resistance. Consequently the functional characterization of orthologous genes in crops holds promise for agriculture. The full set of tomato (Solanum lycopersicum) PYR/PYL/RCAR ABA receptors have been identified here. From the 15 putative tomato ABA receptors, 14 of them could be grouped in three subfamilies that correlated well with corresponding Arabidopsis subfamilies. High levels of expression of PYR/PYL/RCAR genes was found in tomato root, and some genes showed predominant expression in leaf and fruit tissues. Functional characterization of tomato receptors was performed through interaction assays with Arabidopsis and tomato clade A protein phosphatase type 2Cs (PP2Cs) as well as phosphatase inhibition studies. Tomato receptors were able to inhibit the activity of clade A PP2Cs differentially in an ABA-dependent manner, and at least three receptors were sensitive to the ABA agonist quinabactin, which inhibited tomato seed germination. Indeed, the chemical activation of ABA signalling induced by quinabactin was able to activate stress-responsive genes. Both dimeric and monomeric tomato receptors were functional in Arabidopsis plant cells, but only overexpression of monomeric-type receptors conferred enhanced drought resistance. In summary, gene expression analyses, and chemical and transgenic approaches revealed distinct properties of tomato PYR/PYL/RCAR ABA receptors that might have biotechnological implications. PMID:24863435

  15. Elevated CO2-Induced Responses in Stomata Require ABA and ABA Signaling.

    PubMed

    Chater, Caspar; Peng, Kai; Movahedi, Mahsa; Dunn, Jessica A; Walker, Heather J; Liang, Yun-Kuan; McLachlan, Deirdre H; Casson, Stuart; Isner, Jean Charles; Wilson, Ian; Neill, Steven J; Hedrich, Rainer; Gray, Julie E; Hetherington, Alistair M

    2015-10-19

    An integral part of global environment change is an increase in the atmospheric concentration of CO2 ([CO2]) [1]. Increased [CO2] reduces leaf stomatal apertures and density of stomata that plays out as reductions in evapotranspiration [2-4]. Surprisingly, given the importance of transpiration to the control of terrestrial water fluxes [5] and plant nutrient acquisition [6], we know comparatively little about the molecular components involved in the intracellular signaling pathways by which [CO2] controls stomatal development and function [7]. Here, we report that elevated [CO2]-induced closure and reductions in stomatal density require the generation of reactive oxygen species (ROS), thereby adding a new common element to these signaling pathways. We also show that the PYR/RCAR family of ABA receptors [8, 9] and ABA itself are required in both responses. Using genetic approaches, we show that ABA in guard cells or their precursors is sufficient to mediate the [CO2]-induced stomatal density response. Taken together, our results suggest that stomatal responses to increased [CO2] operate through the intermediacy of ABA. In the case of [CO2]-induced reductions in stomatal aperture, this occurs by accessing the guard cell ABA signaling pathway. In both [CO2]-mediated responses, our data are consistent with a mechanism in which ABA increases the sensitivity of the system to [CO2] but could also be explained by requirement for a CO2-induced increase in ABA biosynthesis specifically in the guard cell lineage. Furthermore, the dependency of stomatal [CO2] signaling on ABA suggests that the ABA pathway is, in evolutionary terms, likely to be ancestral.

  16. Elevated CO2-Induced Responses in Stomata Require ABA and ABA Signaling.

    PubMed

    Chater, Caspar; Peng, Kai; Movahedi, Mahsa; Dunn, Jessica A; Walker, Heather J; Liang, Yun-Kuan; McLachlan, Deirdre H; Casson, Stuart; Isner, Jean Charles; Wilson, Ian; Neill, Steven J; Hedrich, Rainer; Gray, Julie E; Hetherington, Alistair M

    2015-10-19

    An integral part of global environment change is an increase in the atmospheric concentration of CO2 ([CO2]) [1]. Increased [CO2] reduces leaf stomatal apertures and density of stomata that plays out as reductions in evapotranspiration [2-4]. Surprisingly, given the importance of transpiration to the control of terrestrial water fluxes [5] and plant nutrient acquisition [6], we know comparatively little about the molecular components involved in the intracellular signaling pathways by which [CO2] controls stomatal development and function [7]. Here, we report that elevated [CO2]-induced closure and reductions in stomatal density require the generation of reactive oxygen species (ROS), thereby adding a new common element to these signaling pathways. We also show that the PYR/RCAR family of ABA receptors [8, 9] and ABA itself are required in both responses. Using genetic approaches, we show that ABA in guard cells or their precursors is sufficient to mediate the [CO2]-induced stomatal density response. Taken together, our results suggest that stomatal responses to increased [CO2] operate through the intermediacy of ABA. In the case of [CO2]-induced reductions in stomatal aperture, this occurs by accessing the guard cell ABA signaling pathway. In both [CO2]-mediated responses, our data are consistent with a mechanism in which ABA increases the sensitivity of the system to [CO2] but could also be explained by requirement for a CO2-induced increase in ABA biosynthesis specifically in the guard cell lineage. Furthermore, the dependency of stomatal [CO2] signaling on ABA suggests that the ABA pathway is, in evolutionary terms, likely to be ancestral. PMID:26455301

  17. Kinetic study of oxalic acid inhibition on enzymatic browning.

    PubMed

    Son, S M; Moon, K D; Lee, C Y

    2000-06-01

    Oxalic acid has a strong antibrowning activity. The inhibitory pattern on catechol-PPO model system appeared to be competitive, with a K(i) value of 2.0 mM. When the PPO was incubated with oxalic acid, the activity was not recovered via dialysis, but the inactivated enzyme partially recovered its activity when cupric ion was added. Comparing the relative antibrowning effectiveness of oxalic acid with other common antibrowning agents, oxalic acid with I(50) value of 1.1 mM is as effective as kojic acid and more potent than cysteine and glutathione.

  18. Piperazic acid derivatives inhibit Gli1 in Hedgehog signaling pathway.

    PubMed

    Khatra, Harleen; Kundu, Jayanta; Khan, Pragya Paramita; Duttagupta, Indranil; Pattanayak, Sankha; Sinha, Surajit

    2016-09-15

    Piperazic acid, a non-proteinogenic amino acid, found in complex secondary metabolites and peptide natural substances, has shown down regulation of Gli1 expression in Hedgehog signaling pathway in cell based assays. Further structure activity relationship study indicated that amide derivatives of piperazic acid are more potent than piperazic acid itself, with little to no toxicity. However, other cellular components involved in the pathway were not affected. To the best of our knowledge, this is the first report on the inhibitory property of piperazic acid in this pathway. Hence, this molecule could serve as a useful tool for studying Hedgehog signaling. PMID:27528433

  19. Development of poly(aspartic acid-co-malic acid) composites for calcium carbonate and sulphate scale inhibition.

    PubMed

    Mithil Kumar, N; Gupta, Sanjay Kumar; Jagadeesh, Dani; Kanny, K; Bux, F

    2015-01-01

    Polyaspartic acid (PSI) is suitable for the inhibition of inorganic scale deposition. To enhance its scale inhibition efficiency, PSI was modified by reacting aspartic acid with malic acid (MA) using thermal polycondensation polymerization. This reaction resulted in poly(aspartic acid-co-malic acid) (PSI-co-MA) dual polymer. The structural, chemical and thermal properties of the dual polymers were analysed by using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry and gel permeation chromatography. The effectiveness of six different molar ratios of PSI-co-MA dual polymer for calcium carbonate and calcium sulphate scale inhibition at laboratory scale batch experiments was evaluated with synthetic brine solution at selected doses of polymer at 65-70°C by the static scale test method. The performance of PSI-co-MA dual polymer for the inhibition of calcium carbonate and calcium sulphate precipitation was compared with that of a PSI single polymer. The PSI-co-MA exhibited excellent ability to control inorganic minerals, with approximately 85.36% calcium carbonate inhibition and 100% calcium sulphate inhibition at a level of 10 mg/L PSI-co-MA, respectively. Therefore, it may be reasonably concluded that PSI-co-MA is a highly effective scale inhibitor for cooling water treatment applications.

  20. Bile acid inhibition of taurocholate uptake by rat hepatocytes: role of OH groups

    SciTech Connect

    Bellentani, S.; Hardison, W.G.M.; Marchegiano, P.; Zanasi, G.; Manenti, F.

    1987-03-01

    To define further the structural specificity of the taurocholate uptake site, the authors studied the ability of a variety of taurine-conjugated bile acids with differing hydroxyl substituents on the sterol moiety to inhibit (/sup 14/C) taurocholate uptake. Rat hepatocytes isolated by collagenase perfusion were incubated in a tris (hydroxymethyl) aminomethane-phosphate buffer containing (/sup 14/C)taurocholate in the presence or absence of inhibitor bile acid. Stronger inhibitors were studied at a fixed concentration of 5 ..mu..M, weaker ones at 25 ..mu..M. Initial uptake velocity was measured. Uptake velocity could then be related to taurocholate concentration and a V/sub max/ and K/sub m/ could be determined by applying a nonlinear least squares fit to the data obtained with or without inhibitor. The kinetic parameters allowed the determination of the type of inhibition and of inhibition constants (K/sub i/) of the various test bile acids. The data indicate that bile acids containing a 6- or 7-OH group exhibit competitive inhibition, whereas bile acids with no 6- or 7-OH group exhibit noncompetitive inhibition. Of the compounds exhibiting competitive inhibition, K/sub i/ varied with the number of hydroxyl groups on the sterol moiety. They conclude that the presence of absence of a 6- or 7-OH group dictates the mechanism of inhibition; the number of hydroxyl substituents determines the potency of competitive inhibition.

  1. ABA Suppresses Botrytis cinerea Elicited NO Production in Tomato to Influence H2O2 Generation and Increase Host Susceptibility

    PubMed Central

    Sivakumaran, Anushen; Akinyemi, Aderemi; Mandon, Julian; Cristescu, Simona M.; Hall, Michael A.; Harren, Frans J. M.; Mur, Luis A. J.

    2016-01-01

    Abscisic acid (ABA) production has emerged a susceptibility factor in plant-pathogen interactions. This work examined the interaction of ABA with nitric oxide (NO) in tomato following challenge with the ABA-synthesizing pathogen, Botrytis cinerea. Trace gas detection using a quantum cascade laser detected NO production within minutes of challenge with B. cinerea whilst photoacoustic laser detection detected ethylene production – an established mediator of defense against this pathogen – occurring after 6 h. Application of the NO generation inhibitor N-Nitro-L-arginine methyl ester (L-NAME) suppressed both NO and ethylene production and resistance against B. cinerea. The tomato mutant sitiens fails to accumulate ABA, shows increased resistance to B. cinerea and we noted exhibited elevated NO and ethylene production. Exogenous application of L-NAME or ABA reduced NO production in sitiens and reduced resistance to B. cinerea. Increased resistance to B. cinerea in sitiens have previously been linked to increased reactive oxygen species (ROS) generation but this was reduced in both L-NAME and ABA-treated sitiens. Taken together, our data suggests that ABA can decreases resistance to B. cinerea via reduction of NO production which also suppresses both ROS and ethylene production. PMID:27252724

  2. ABA Suppresses Botrytis cinerea Elicited NO Production in Tomato to Influence H2O2 Generation and Increase Host Susceptibility.

    PubMed

    Sivakumaran, Anushen; Akinyemi, Aderemi; Mandon, Julian; Cristescu, Simona M; Hall, Michael A; Harren, Frans J M; Mur, Luis A J

    2016-01-01

    Abscisic acid (ABA) production has emerged a susceptibility factor in plant-pathogen interactions. This work examined the interaction of ABA with nitric oxide (NO) in tomato following challenge with the ABA-synthesizing pathogen, Botrytis cinerea. Trace gas detection using a quantum cascade laser detected NO production within minutes of challenge with B. cinerea whilst photoacoustic laser detection detected ethylene production - an established mediator of defense against this pathogen - occurring after 6 h. Application of the NO generation inhibitor N-Nitro-L-arginine methyl ester (L-NAME) suppressed both NO and ethylene production and resistance against B. cinerea. The tomato mutant sitiens fails to accumulate ABA, shows increased resistance to B. cinerea and we noted exhibited elevated NO and ethylene production. Exogenous application of L-NAME or ABA reduced NO production in sitiens and reduced resistance to B. cinerea. Increased resistance to B. cinerea in sitiens have previously been linked to increased reactive oxygen species (ROS) generation but this was reduced in both L-NAME and ABA-treated sitiens. Taken together, our data suggests that ABA can decreases resistance to B. cinerea via reduction of NO production which also suppresses both ROS and ethylene production. PMID:27252724

  3. Linking Turgor with ABA Biosynthesis: Implications for Stomatal Responses to Vapor Pressure Deficit across Land Plants1[OPEN

    PubMed Central

    McAdam, Scott A.M.; Brodribb, Timothy J.

    2016-01-01

    Stomatal responses to changes in vapor pressure deficit (VPD) constitute the predominant form of daytime gas-exchange regulation in plants. Stomatal closure in response to increased VPD is driven by the rapid up-regulation of foliar abscisic acid (ABA) biosynthesis and ABA levels in angiosperms; however, very little is known about the physiological trigger for this increase in ABA biosynthesis at increased VPD. Using a novel method of modifying leaf cell turgor by the application of external pressures, we test whether changes in turgor pressure can trigger increases in foliar ABA levels over 20 min, a period of time most relevant to the stomatal response to VPD. We found in angiosperm species that the biosynthesis of ABA was triggered by reductions in leaf turgor, and in two species tested, that a higher sensitivity of ABA synthesis to leaf turgor corresponded with a higher stomatal sensitivity to VPD. In contrast, representative species from nonflowering plant lineages did not show a rapid turgor-triggered increase in foliar ABA levels, which is consistent with previous studies demonstrating passive stomatal responses to changes in VPD in these lineages. Our method provides a new tool for characterizing the response of stomata to water availability. PMID:27208264

  4. [Inhibition of glutamine synthetase activity by biologically active derivatives of glutamic acid].

    PubMed

    Firsova, N A; Selivanova, K M; Alekseeva, L V; Evstigneeva, Z G

    1986-05-01

    The inhibition of activity of glutamine synthetase from Chlorella and porcine brain by 4-hydroxy-D-4-fluoro-D,L- and 4-amino-D,L-glutamic acids diastereoisomers was studied. Each compound was shown to exert the same inhibiting effect on glutamine synthetase from both sources. In case of threo-4-hydroxy-D-glutamic acid the inhibition of the Chlorella enzyme was of a competitive and of a completely mixed type. The enzyme inhibition by 4-fluoro-D, L-glutamic acids seemed to be of a completely non-competitive type. The Ki values for all inhibition reactions were determined. A comparison of biochemical parameters and biological activity revealed that the most effective inhibitors of the enzyme exert a most potent antitumour and antiviral action.

  5. Sustained low abscisic acid levels increase seedling vigor under cold stress in rice (Oryza sativa L.).

    PubMed

    Mega, Ryosuke; Meguro-Maoka, Ayano; Endo, Akira; Shimosaka, Etsuo; Murayama, Seiji; Nambara, Eiji; Seo, Mitsunori; Kanno, Yuri; Abrams, Suzanne R; Sato, Yutaka

    2015-01-01

    Stress-induced abscisic acid (ABA) is mainly catabolized by ABA 8'-hydroxylase (ABA8ox), which also strictly regulates endogenous ABA levels. Although three members of the ABA8ox gene family are conserved in rice, it is not clear which stressors induce expression of these genes. Here, we found that OsABA8ox1 was induced by cold stress within 24 h and that OsABA8ox2 and OsABA8ox3 were not. In contrast, OsABA8ox2 and OsABA8ox3 were ABA-inducible, but OsABA8ox1 was not. OsABA8ox1, OsABA8ox2, and OsABA8ox3 restored germination of a cyp707a1/a2/a3 triple mutant of Arabidopsis to rates comparable to those of the wild type, indicating that OsABA8ox1, OsABA8ox2, and OsABA8ox3 function as ABA-catabolic genes in vivo. Transgenic rice lines overexpressing OsABA8ox1 showed decreased levels of ABA and increased seedling vigor at 15 °C. These results indicate that sustained low levels of ABA lead to increased seedling vigor during cold stress. On the other hand, excessively low endogenous ABA levels caused reduced drought and cold tolerance, although some of the transgenic rice lines expressing OsABA8ox1 at moderate levels did not show these harmful effects. Adequate regulation of endogenous ABA levels is thought to be crucial for maintaining seedling vigor under cold stress and for cold and drought tolerance in rice.

  6. ABA homeostasis and signaling involving multiple subcellular compartments and multiple receptors.

    PubMed

    Xu, Zheng-Yi; Kim, Dae Heon; Hwang, Inhwan

    2013-06-01

    The plant hormone abscisic acid (ABA) plays pivotal roles in many important physiological processes including stomatal closure, seed dormancy, growth and various environmental stresses. In these responses, ABA action is under the control of complex regulatory mechanisms involving homeostasis, perception and signaling. Recent studies provide new insights into these processes, which are of great importance in understanding the mechanisms underlying the evolutionary principle of how plants can survive as a sessile organism under ever-changing environmental conditions. They also form the basis for designing plants that have an enhanced resistance to various stresses in particular abiotic stress.

  7. Inhibition of DNA methylation by caffeic acid and chlorogenic acid, two common catechol-containing coffee polyphenols.

    PubMed

    Lee, Won Jun; Zhu, Bao Ting

    2006-02-01

    We studied the modulating effects of caffeic acid and chlorogenic acid (two common coffee polyphenols) on the in vitro methylation of synthetic DNA substrates and also on the methylation status of the promoter region of a representative gene in two human cancer cells lines. Under conditions that were suitable for the in vitro enzymatic methylation of DNA and dietary catechols, we found that the presence of caffeic acid or chlorogenic acid inhibited in a concentration-dependent manner the DNA methylation catalyzed by prokaryotic M.SssI DNA methyltransferase (DNMT) and human DNMT1. The IC50 values of caffeic acid and chlorogenic acid were 3.0 and 0.75 microM, respectively, for the inhibition of M.SssI DNMT-mediated DNA methylation, and were 2.3 and 0.9 microM, respectively, for the inhibition of human DNMT1-mediated DNA methylation. The maximal in vitro inhibition of DNA methylation was approximately 80% when the highest concentration (20 microM) of caffeic acid or chlorogenic acid was tested. Kinetic analyses showed that DNA methylation catalyzed by M.SssI DNMT or human DNMT1 followed the Michaelis-Menten curve patterns. The presence of caffeic acid or chlorogenic acid inhibited DNA methylation predominantly through a non-competitive mechanism, and this inhibition was largely due to the increased formation of S-adenosyl-L-homocysteine (SAH, a potent inhibitor of DNA methylation), resulting from the catechol-O-methyltransferase (COMT)-mediated O-methylation of these dietary catechols. Using cultured MCF-7 and MAD-MB-231 human breast cancer cells, we also demonstrated that treatment of these cells with caffeic acid or chlorogenic acid partially inhibited the methylation of the promoter region of the RARbeta gene. The findings of our present study provide a general mechanistic basis for the notion that a variety of dietary catechols can function as inhibitors of DNA methylation through increased formation of SAH during the COMT-mediated O-methylation of these dietary

  8. 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.

  9. Proteomic analysis of the effects of ABA treatments on ripening Vitis vinifera berries

    PubMed Central

    Giribaldi, Marzia; Gény, Laurence; Delrot, Serge; Schubert, Andrea

    2010-01-01

    The control of ripening of the non-climacteric grapevine fruit is still a matter of debate, but several lines of evidence point to an important role for the hormone abscisic acid (ABA). The effects of ABA treatments on Cabernet Sauvignon berries before and at véraison were studied using a 2-DE proteomic approach. Proteins from whole deseeded berries (before véraison) and berry flesh and skin (at véraison) treated with 0.76 mM ABA and collected 24 h after treatment were separated and analysed. A total of 60 protein spots showed significant variations between treated and control berries, and 40 proteins, mainly related to general metabolism and cell defence, were identified by LC MS/MS. Our results show that ABA acts mainly through the regulation of mostly the same proteins which are involved in the ripening process, and that several of these changes share common elements with the ABA-induced responses in vegetative tissues. PMID:20388747

  10. Boric acid application guidelines for intergranular corrosion inhibition

    SciTech Connect

    Piskor, S.R. . Nuclear Services Div.)

    1990-12-01

    A significant fraction of the operating Pressurized Water Reactor steam generators have used or are using boric acid as an inhibitor to control stress corrosion cracking, intergranular attack, or denting. Boric acid is applied on line, or by means of crevice flushing, low power soaks, or a combination of these methods. When boric acid is used, it is important to have knowledge about its chemical and physical properties, its effect on corrosion, and its correct application. The data on these subjects may be found in a diversity of sources, which are often not readily available or convenient to use. In addition, new information has recently become available. This report has been prepared and revised to be comprehensive treatise on boric acid relevant to its application in nuclear steam generators. Relevant boric acid information from 1987--89 has been added to provide the latest available data from laboratory testing and power plant application. 5 figs.

  11. ABA gene expression during kernel development in relation to pre-harvest sprouting in wheat and triticale.

    PubMed

    Sarah, De Laethauwer; Jan, De Riek; Geert, Haesaert

    2014-01-01

    Pre-harvest sprouting (PHS) during wet and cool harvest periods remains a serious problem in the production of cereals like barley, wheat and triticale. Being involved in dormancy induction and maintenance during seed development, abscisic acid (ABA) may play a key role to improve dormancy level and hence PHS-tolerance in these grains. In this study, we investigated the ABA levels and expression profiles of ABA biosynthesis and degradation genes during kernel development to explore the potential of these genes for improving PHS-tolerance in wheat and triticale. Plants of a PHS-tolerant and a PHS-susceptible variety of both wheat and triticale were grown under controlled conditions from flowering to harvest. At regular time points, kernels were harvested for ABA analysis and RNA extraction. RNA extracts were used in an RT-qPCR assay to obtain expression profiles of the ABA synthesis genes ZEP, NCED1 and NCED2 and the ABA degradation genes CYP707A1 and CYP707A2. In contrast to reports in Arabidopsis, the ZEP gene was predominantly expressed towards harvest maturity in both wheat and triticale. NCED1 expression coincided well with the observed ABA levels during kernel development, while NCED2 expression was mainly detected in early development, indicating a potential role for dormancy induction. ABA degradation towards harvest maturity was mainly associated with increased CYP707A1 expression, whereas CYP707A2 expression appeared to correlate with the regulation of ABA levels during kernel development. However, no differential expression of the investigated genes was detected between PHS-tolerant and PHS-susceptible varieties.

  12. A role for AMPK in the inhibition of glucose-6-phosphate dehydrogenase by polyunsaturated fatty acids

    SciTech Connect

    Kohan, Alison B.; Talukdar, Indrani; Walsh, Callee M.; Salati, Lisa M.

    2009-10-09

    Both polyunsaturated fatty acids and AMPK promote energy partitioning away from energy consuming processes, such as fatty acid synthesis, towards energy generating processes, such as {beta}-oxidation. In this report, we demonstrate that arachidonic acid activates AMPK in primary rat hepatocytes, and that this effect is p38 MAPK-dependent. Activation of AMPK mimics the inhibition by arachidonic acid of the insulin-mediated induction of G6PD. Similar to intracellular signaling by arachidonic acid, AMPK decreases insulin signal transduction, increasing Ser{sup 307} phosphorylation of IRS-1 and a subsequent decrease in AKT phosphorylation. Overexpression of dominant-negative AMPK abolishes the effect of arachidonic acid on G6PD expression. These data suggest a role for AMPK in the inhibition of G6PD by polyunsaturated fatty acids.

  13. Inhibition of ultraviolet-B skin carcinogenesis by all-trans-retinoic acid regimens that inhibit ornithine decarboxylase induction

    SciTech Connect

    Connor, M.J.; Lowe, N.J.; Breeding, J.H.; Chalet, M.

    1983-01-01

    There is a correlation between the ability to induce the polyamine-biosynthetic enzyme ornithine decarboxylase (ODC) and the tumor-promoting ability of various carcinogens in mouse epidermis. Some agents which inhibit skin carcinogenesis also inhibit ODC induction. In this study, all-trans-retinoic acid (RA) regimens that inhibited the induction of epidermal ODC by ultraviolet-B (UVB) were tested for their ability to inhibit UVB skin carcinogenesis. Hairless mice were irradiated once daily with UVB for 20 days, receiving a total dose of UVB (17.1 kJ/sq m). Topical RA was applied immediately (RA, one dose) or applied 0, 1, 2, 3, and 4 hr (RA, five doses) after each irradiance. The mice were maintained for 52 weeks and then sacrificed. Groups treated with RA tended to have fewer mice with tumors, fewer tumors per mouse, smaller tumor diameters, and slower growing tumors than did appropriate irradiated control groups. RA given five times was more effective than was RA given one time at inhibiting UVB skin carcinogenesis. These results show that RA treatments that inhibit epidermal ODC induction may be effective in reducing the carcinogenicity of UVB.

  14. Galacturonic Acid Inhibits the Growth of Saccharomyces cerevisiae on Galactose, Xylose, and Arabinose

    PubMed Central

    Huisjes, Eline H.; de Hulster, Erik; van Dam, Jan C.; Pronk, Jack T.

    2012-01-01

    The efficient fermentation of mixed substrates is essential for the microbial conversion of second-generation feedstocks, including pectin-rich waste streams such as citrus peel and sugar beet pulp. Galacturonic acid is a major constituent of hydrolysates of these pectin-rich materials. The yeast Saccharomyces cerevisiae, the main producer of bioethanol, cannot use this sugar acid. The impact of galacturonic acid on alcoholic fermentation by S. cerevisiae was investigated with anaerobic batch cultures grown on mixtures of glucose and galactose at various galacturonic acid concentrations and on a mixture of glucose, xylose, and arabinose. In cultures grown at pH 5.0, which is well above the pKa value of galacturonic acid (3.51), the addition of 10 g · liter−1 galacturonic acid did not affect galactose fermentation kinetics and growth. In cultures grown at pH 3.5, the addition of 10 g · liter−1 galacturonic acid did not significantly affect glucose consumption. However, at this lower pH, galacturonic acid completely inhibited growth on galactose and reduced galactose consumption rates by 87%. Additionally, it was shown that galacturonic acid strongly inhibits the fermentation of xylose and arabinose by the engineered pentose-fermenting S. cerevisiae strain IMS0010. The data indicate that inhibition occurs when nondissociated galacturonic acid is present extracellularly and corroborate the hypothesis that a combination of a decreased substrate uptake rate due to competitive inhibition on Gal2p, an increased energy requirement to maintain cellular homeostasis, and/or an accumulation of galacturonic acid 1-phosphate contributes to the inhibition. The role of galacturonic acid as an inhibitor of sugar fermentation should be considered in the design of yeast fermentation processes based on pectin-rich feedstocks. PMID:22582063

  15. Galacturonic acid inhibits the growth of Saccharomyces cerevisiae on galactose, xylose, and arabinose.

    PubMed

    Huisjes, Eline H; de Hulster, Erik; van Dam, Jan C; Pronk, Jack T; van Maris, Antonius J A

    2012-08-01

    The efficient fermentation of mixed substrates is essential for the microbial conversion of second-generation feedstocks, including pectin-rich waste streams such as citrus peel and sugar beet pulp. Galacturonic acid is a major constituent of hydrolysates of these pectin-rich materials. The yeast Saccharomyces cerevisiae, the main producer of bioethanol, cannot use this sugar acid. The impact of galacturonic acid on alcoholic fermentation by S. cerevisiae was investigated with anaerobic batch cultures grown on mixtures of glucose and galactose at various galacturonic acid concentrations and on a mixture of glucose, xylose, and arabinose. In cultures grown at pH 5.0, which is well above the pK(a) value of galacturonic acid (3.51), the addition of 10 g · liter(-1) galacturonic acid did not affect galactose fermentation kinetics and growth. In cultures grown at pH 3.5, the addition of 10 g · liter(-1) galacturonic acid did not significantly affect glucose consumption. However, at this lower pH, galacturonic acid completely inhibited growth on galactose and reduced galactose consumption rates by 87%. Additionally, it was shown that galacturonic acid strongly inhibits the fermentation of xylose and arabinose by the engineered pentose-fermenting S. cerevisiae strain IMS0010. The data indicate that inhibition occurs when nondissociated galacturonic acid is present extracellularly and corroborate the hypothesis that a combination of a decreased substrate uptake rate due to competitive inhibition on Gal2p, an increased energy requirement to maintain cellular homeostasis, and/or an accumulation of galacturonic acid 1-phosphate contributes to the inhibition. The role of galacturonic acid as an inhibitor of sugar fermentation should be considered in the design of yeast fermentation processes based on pectin-rich feedstocks. PMID:22582063

  16. Galacturonic acid inhibits the growth of Saccharomyces cerevisiae on galactose, xylose, and arabinose.

    PubMed

    Huisjes, Eline H; de Hulster, Erik; van Dam, Jan C; Pronk, Jack T; van Maris, Antonius J A

    2012-08-01

    The efficient fermentation of mixed substrates is essential for the microbial conversion of second-generation feedstocks, including pectin-rich waste streams such as citrus peel and sugar beet pulp. Galacturonic acid is a major constituent of hydrolysates of these pectin-rich materials. The yeast Saccharomyces cerevisiae, the main producer of bioethanol, cannot use this sugar acid. The impact of galacturonic acid on alcoholic fermentation by S. cerevisiae was investigated with anaerobic batch cultures grown on mixtures of glucose and galactose at various galacturonic acid concentrations and on a mixture of glucose, xylose, and arabinose. In cultures grown at pH 5.0, which is well above the pK(a) value of galacturonic acid (3.51), the addition of 10 g · liter(-1) galacturonic acid did not affect galactose fermentation kinetics and growth. In cultures grown at pH 3.5, the addition of 10 g · liter(-1) galacturonic acid did not significantly affect glucose consumption. However, at this lower pH, galacturonic acid completely inhibited growth on galactose and reduced galactose consumption rates by 87%. Additionally, it was shown that galacturonic acid strongly inhibits the fermentation of xylose and arabinose by the engineered pentose-fermenting S. cerevisiae strain IMS0010. The data indicate that inhibition occurs when nondissociated galacturonic acid is present extracellularly and corroborate the hypothesis that a combination of a decreased substrate uptake rate due to competitive inhibition on Gal2p, an increased energy requirement to maintain cellular homeostasis, and/or an accumulation of galacturonic acid 1-phosphate contributes to the inhibition. The role of galacturonic acid as an inhibitor of sugar fermentation should be considered in the design of yeast fermentation processes based on pectin-rich feedstocks.

  17. Development of Poly Unsaturated Fatty Acid Derivatives of Aspirin for Inhibition of Platelet Function.

    PubMed

    Roy, Jahnabi; Adili, Reheman; Kulmacz, Richard; Holinstat, Michael; Das, Aditi

    2016-10-01

    The inhibition of platelet aggregation is key to preventing conditions such as myocardial infarction and ischemic stroke. Aspirin is the most widely used drug to inhibit platelet aggregation. Aspirin absorption can be improved further to increase its permeability across biologic membranes via esterification or converting the carboxylic acid to an anhydride. There are several reports indicating that ω-3 and ω-6 fatty acids such as linoleic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) separately inhibit platelet aggregation. Herein, we synthesize anhydride conjugates of aspirin with linoleic acid, EPA, and DHA to form aspirin anhydrides that are expected to have higher permeability across cellular membranes. These aspirin-fatty acid anhydrides inhibited platelet aggregation in washed human platelets and platelet-rich plasma in a dose-dependent manner. In particular, the aspirin-DHA anhydride displayed similar effectiveness to aspirin. Platelet aggregation studies conducted in the presence of various platelet agonists indicated that the aspirin-lipid conjugates act through inhibition of the cyclooxygenase (COX)-thromboxane synthase (TXAS) pathway. Hence, we performed detailed biochemical studies using purified COX-1 as well as TXAS stabilized in nanoscale lipid bilayers of nanodiscs to confirm results from the platelet aggregation studies. We show that although all of the aspirin conjugates act through the COX-TXAS pathway by inhibiting COX-1, the parent fatty acids do not act via this pathway. Finally, we studied the hydrolysis of these compounds in buffer and human plasma, and we demonstrate that all of the aspirin-fatty acid conjugates hydrolyze to the parent molecules aspirin and fatty acid in a controlled manner. PMID:27488919

  18. Fast online determination of surfactant inhibition in acidic phase bioreactors.

    PubMed

    Feitkenhauer, H

    2004-01-01

    Surfactants have been shown to inhibit the anaerobic digestion process severely, with the methanogenic microorganisms being the most affected. The diverse nature of surfactants used even in one (e.g. textile finishing) plant makes an online determination of surfactants sometimes very difficult and expensive. Therefore a fast online determination of inhibitory effects on the acidogenic microorganisms (first step of the degradation cascade) can help to give an early warning signal or to calculate a "pseudo"-surfactant concentration. In a two-phase system this information can be used to protect the methanogenic reactor against surfactant overloading and its long term negative effects. In this paper it is shown that the inhibition is a consequence of microbial inhibition and is not caused by an inactivation of extracellular hydrolytic enzymes (released by the cells for biopolymer cleavage). A titration technique was successfully employed to measure the surfactant inhibition in a laboratory-scale acidification reactor. Additional experiments demonstrate (using sodium dodecyl sulfate as the model substance) how inhibitory effects (and strategies to overcome inhibitory effects) can be investigated efficiently.

  19. Jasmonic acid transient accumulation is needed for abscisic acid increase in citrus roots under drought stress conditions.

    PubMed

    de Ollas, Carlos; Hernando, Bárbara; Arbona, Vicent; Gómez-Cadenas, Aurelio

    2013-03-01

    Phytohormones are central players in sensing and signaling numerous environmental conditions like drought stress. In this work, an experimental system based on severe drought was established and hormone profiling together with gene expression of key enzymes involved in abscisic acid (ABA) and jasmonic acid (JA) biosynthesis was studied in roots of citrumelo CPB 4475 (a commercial citrus rootstock) plants. JA concentration transiently increased after a few hours of stress, returning to control levels 30 h after the onset of the condition. A more progressive ABA accumulation was observed, with the onset of this increase at the same time or right after the JA transient accumulation. Molecular data suggested that, at least, part of the hormonal regulation takes place at the biosynthetic level. These observations also pointed to a possible involvement of JA on ABA biosynthesis under stress. To test this hypothesis, JA and ABA biosynthesis were chemically inhibited and subsequently phenotypes rescued by the addition of exogenous hormones. Results showed that the early JA accumulation was necessary for the subsequent ABA increase in roots under stress whereas the opposite could not be stated. The model includes a burst of JA in roots of citrus under severe drought stress conditions that leads to a more progressive ABA accumulation that will induce later plant responses. The present work adds a new level of interaction between JA and ABA at the biosynthetic level that together with the previously described interaction between signal transduction cascades of the two hormones would allow plants to fine-tune specific responses to different stimuli.

  20. Hardening with salicylic acid induces concentration-dependent changes in abscisic acid biosynthesis of tomato under salt stress.

    PubMed

    Horváth, Edit; Csiszár, Jolán; Gallé, Ágnes; Poór, Péter; Szepesi, Ágnes; Tari, Irma

    2015-07-01

    The role of salicylic acid (SA) in the control of abscisic acid (ABA) biosynthesis is controversial although both plant growth regulators may accumulate in tissues under abiotic and biotic stress conditions. Hardening of tomato plants to salinity stress with 10(-4)M SA ("high SA") resulted in an up-regulation of ABA biosynthesis genes, zeaxanthin epoxidase (SlZEP1), 9-cis-epoxycarotenoid dioxygenase (SlNCED1) and aldehyde oxidases (SlAO1 and SlAO2) in the roots and led to ABA accumulation both in root and leaf tissues. In plants pre-treated with lower concentration of SA (10(-7)M, "low SA"), the up-regulation of SlNCED1 in the roots promoted ABA accumulation in the root tissues but the hormone concentration remained at control level in the leaves. Salt stress induced by 100mM NaCl reduced the transcript abundance of ABA biosynthetic genes and inhibited SlAO activity in plants hardened with "high SA", but the tissues maintained root ABA level over the untreated control. The combined effect of "high SA" and ABA under salt stress led to partially recovered photosynthetic activity, reduced ethylene production in root apices, and restored root growth, which is one of the main features of salt tolerance. Unlike "high SA", hardening with "low SA" had no influence on ethylene production, and led to reduced elongation of roots in plants exposed to 100mM NaCl. The up-regulation of carotenoid cleavage dioxygenases SlCCD1A and SlCCD1B by SA, which produce apocarotenoids, may open new pathways in SA sensing and signalling processes.

  1. Growth inhibition of Cronobacter spp. strains in reconstituted powdered infant formula acidified with organic acids supported by natural stomach acidity.

    PubMed

    Zhu, S; Schnell, S; Fischer, M

    2013-09-01

    Cronobacter is associated with outbreaks of rare, but life-threatening cases of meningitis, necrotizing enterocolitis, and sepsis in newborns. This study was conducted to determine the effect of organic acids on growth of Cronobacter in laboratory medium and reconstituted powdered infant formula (PIF) as well as the bacteriostatic effect of slightly acidified infant formula when combined with neonatal gastric acidity. Inhibitory effect of seven organic acids on four acid sensitive Cronobacter strains was determined in laboratory medium with broth dilution method at pH 5.0, 5.5 and 6.0. Acetic, butyric and propionic acids were most inhibitive against Cronobacter in the laboratory medium. The killing effect of these three acids was partially buffered in reconstituted PIF. Under neonatal gastric acid condition of pH 5.0, the slightly acidified formula which did not exert inhibition effect solely reduced significantly the Cronobacter populations. A synergistic effect of formula moderately acidified with organic acid combined with the physiological infant gastric acid was visible in preventing the rapid growth of Cronobacter in neonatal stomach. The study contributed to a better understanding of the inhibitory effect of organic acids on Cronobacter growth in different matrixes and provided new ideas in terms of controlling bacteria colonization and translocation by acidified formula.

  2. Salicylic acid inhibits enzymatic browning of fresh-cut Chinese chestnut (Castanea mollissima) by competitively inhibiting polyphenol oxidase.

    PubMed

    Zhou, Dan; Li, Lin; Wu, Yanwen; Fan, Junfeng; Ouyang, Jie

    2015-03-15

    The inhibitory effect and associated mechanisms of salicylic acid (SA) on the browning of fresh-cut Chinese chestnut were investigated. Shelled and sliced chestnuts were immersed in different concentrations of an SA solution, and the browning of the chestnut surface and interior were inhibited. The activities of polyphenol oxidase (PPO) and peroxidase (POD) extracted from chestnuts were measured in the presence and absence of SA. SA at concentrations higher than 0.3g/L delayed chestnut browning by significantly inhibiting the PPO activity (P<0.01), and the POD activity was not significantly affected (P>0.05). The binding and inhibition modes of SA with PPO and POD, determined by AUTODOCK 4.2 and Lineweaver-Burk plots, respectively, established SA as a competitive inhibitor of PPO. PMID:25308637

  3. Salicylic acid inhibits enzymatic browning of fresh-cut Chinese chestnut (Castanea mollissima) by competitively inhibiting polyphenol oxidase.

    PubMed

    Zhou, Dan; Li, Lin; Wu, Yanwen; Fan, Junfeng; Ouyang, Jie

    2015-03-15

    The inhibitory effect and associated mechanisms of salicylic acid (SA) on the browning of fresh-cut Chinese chestnut were investigated. Shelled and sliced chestnuts were immersed in different concentrations of an SA solution, and the browning of the chestnut surface and interior were inhibited. The activities of polyphenol oxidase (PPO) and peroxidase (POD) extracted from chestnuts were measured in the presence and absence of SA. SA at concentrations higher than 0.3g/L delayed chestnut browning by significantly inhibiting the PPO activity (P<0.01), and the POD activity was not significantly affected (P>0.05). The binding and inhibition modes of SA with PPO and POD, determined by AUTODOCK 4.2 and Lineweaver-Burk plots, respectively, established SA as a competitive inhibitor of PPO.

  4. Chelator profiling in Deschampsia cespitosa (L.) Beauv. Reveals a Ni reaction, which is distinct from the ABA and cytokinin associated response to Cd.

    PubMed

    Hayward, Allison R; Coates, Kahlan E; Galer, Amy L; Hutchinson, Thomas C; Emery, R J Neil

    2013-03-01

    Plant hormones, including abscisic acid (ABA) and cytokinins (CKs), fluctuate as a result of excess metal exposure. Changes in hormonal concentration regulate plant growth and may also signal activation of metal chelators. The grass Deschampsia cespitosa was dosed with either Ni or Cd or pulsed with exogenous ABA. The roots were analyzed for ABA and CKs and for multiple potential metal chelators including: amino acids, nicotianamine (NA), and phytochelatins (PCs). They were quantified after 3 h and after 7 days, using LC-ESI MS/MS. The Ni treatment caused no measurable change in ABA or CK concentration; however, an increase in NA was documented. The Cd treatment resulted in a short-term ABA increase followed by a reduction in CKs and an increase in PC concentration. An exogenous ABA pulse in non-metal challenged plants induced changes in CKs and PCs that followed those of Cd treatment. Ni and Cd stress resulted in distinctly different detoxification responses. Since the reaction of CKs and putative metal chelators to Cd stress can be mimicked by an exogenous ABA pulse, it is suggested that ABA acts as a stress signal, resulting in reduced growth by way of decreased CK concentration and reduced metal toxicity through increased PC production.

  5. Protease inhibition by oleic acid transfer from chronic wound dressings to albumin.

    PubMed

    Edwards, J Vincent; Howley, Phyllis; Davis, Rachel; Mashchak, Andrew; Goheen, Steven C

    2007-08-01

    High elastase and cathepsin G activities have been observed in chronic wounds to inhibit healing through degradation of growth factors, cytokines, and extracellular matrix proteins. Oleic acid is a non-toxic elastase inhibitor. Cotton wound dressing material was characterized as a transfer carrier for affinity uptake of oleic acid by albumin under conditions mimicking chronic wounds. The mechanism of oleic acid uptake from cotton and binding by albumin was examined with both intact dressings and cotton fiber-designed chromatography. Raman spectra of the albumin-oleic acid complexes under liquid equilibrium conditions revealed fully saturated albumin-oleic acid complexes with a 1:1 weight ratio of albumin:oleic acid. Liquid-solid equilibrium conditions revealed oleic acid transfer from cotton to albumin at 27 mole equivalents of oleic acid per mole albumin. Comparing oleic acid formulated wound dressings for dose dependent ability to lower elastase activity, we found cotton gauze>hydrogel>hydrocolloid. In contrast, the cationic serine protease cathepsin G was inhibited by oleic acid within a narrow range of oleic acid-cotton formulations. 2% albumin was sufficient to transfer quantities of oleic acid necessary to achieve a significant elastase-lowering effect. Oleic acid bound to cotton wound dressings may have promise in the selective lowering of cationic serine protease activity useful in topical application for chronic inflammatory pathogenesis.

  6. DICHLOROACETIC ACID (DCA) INHIBITS PROLIFERATION AND APOPTOSIS IN NORMAL HEPATOCYTES OF MALE F344 RATS

    EPA Science Inventory

    Dichloroacetic acid (DCA} inhibits proliferation and apoptosis in nonnal hepatocytes of
    male F344 rats.

    Large segments of the population are chronically exposed to dichloroacetic acid (DCA}: DCA is a by product of the chlorine disinfection of drinking water, a metab...

  7. Vanadate inhibition of fungal phyA and bacterial appA2 histidine acid phosphatases

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The fungal PhyA protein, which was first identified as an acid optimum phosphomonoesterase (EC 3.1.3.8), could also serve as a vanadate haloperoxidase (EC 1.11.1.10) provided the acid phosphatase activity is shutdown by vanadate. To understand how vanadate inhibits both phytate and pNPP degrading ac...

  8. SOLUBLE HEPATIC δ-AMINOLEVULINIC ACID SYNTHETASE: END-PRODUCT INHIBITION OF THE PARTIALLY PURIFIED ENZYME*

    PubMed Central

    Scholnick, Perry L.; Hammaker, Lydia E.; Marver, Harvey S.

    1969-01-01

    The present study confirms the existence of hepatic δ-aminolevulinic acid synthetase in the cytosol of the liver, suggests that this enzyme may be in transit to the mitochondria, and defines some of the characteristics of the partially purified enzyme. The substrate and cofactor requirements are similar to those of mitochondrial δ-aminolevulinic acid synthetase. Heme strongly inhibits the partially purified enzyme. A number of proteins that bind heme block this inhibition, which explains previous failures to demonstrate heme inhibition in crude systems. End-product inhibition of δ-aminolevulinic acid synthetase in the mitochondria may play an important role in the regulation of heme biosynthesis in eukaryotic cells. PMID:5257968

  9. Mechanism of iron inhibition by stearic acid Langmuir-Blodgett monolayers

    SciTech Connect

    Xing, W.; Shan, Y.; Guo, D.; Lu, T.; Xi, S.

    1995-01-01

    Many organic compounds can be adsorbed onto the interface of a metal and solution to form a thin film that inhibits the corrosion process according to a blocking and/or negative catalytic effect. Using the Langmuir-Blodgett (LB) technique, stearic acid (SA) monolayers were deposited onto the surface of an iron (Fe) electrode to study the inhibition effect and the mechanism of SA in a neutral medium. Molecular orientation and the number of deposited monolayers of SA were shown to have marked effects on inhibition of Fe corrosion. The inhibition mechanism depended mainly on blocking.

  10. Autocrine abscisic acid plays a key role in quartz-induced macrophage activation.

    PubMed

    Magnone, Mirko; Sturla, Laura; Jacchetti, Emanuela; Scarfì, Sonia; Bruzzone, Santina; Usai, Cesare; Guida, Lucrezia; Salis, Annalisa; Damonte, Gianluca; De Flora, Antonio; Zocchi, Elena

    2012-03-01

    Inhalation of quartz induces silicosis, a lung disease where alveolar macrophages release inflammatory mediators, including prostaglandin-E(2) (PGE(2)) and tumor necrosis factor α (TNF-α). Here we report the pivotal role of abscisic acid (ABA), a recently discovered human inflammatory hormone, in silica-induced activation of murine RAW264.7 macrophages and of rat alveolar macrophages (AMs). Stimulation of both RAW264.7 cells and AMs with quartz induced a significant increase of ABA release (5- and 10-fold, respectively), compared to untreated cells. In RAW264.7 cells, autocrine ABA released after quartz stimulation sequentially activates the plasma membrane receptor LANCL2 and NADPH oxidase, generating a Ca(2+) influx resulting in NFκ B nuclear translocation and PGE(2) and TNF-α release (3-, 2-, and 3.5-fold increase, respectively, compared to control, unstimulated cells). Quartz-stimulated RAW264.7 cells silenced for LANCL2 or preincubated with a monoclonal antibody against ABA show an almost complete inhibition of NFκ B nuclear translocation and PGE(2) and TNF-α release compared to controls electroporated with a scramble oligonucleotide or preincubated with an unrelated antibody. AMs showed similar early and late ABA-induced responses as RAW264.7 cells. These findings identify ABA and LANCL2 as key mediators in quartz-induced inflammation, providing possible new targets for antisilicotic therapy.

  11. Postharvest Exogenous Application of Abscisic Acid Reduces Internal Browning in Pineapple.

    PubMed

    Zhang, Qin; Liu, Yulong; He, Congcong; Zhu, Shijiang

    2015-06-10

    Internal browning (IB) is a postharvest physiological disorder causing economic losses in pineapple, but there is no effective control measure. In this study, postharvest application of 380 μM abscisic acid (ABA) reduced IB incidence by 23.4-86.3% and maintained quality in pineapple fruit. ABA reduced phenolic contents and polyphenol oxidase and phenylalanine ammonia lyase activities; increased catalase and peroxidase activities; and decreased O2(·-), H2O2, and malondialdehyde levels. This suggests ABA could control IB through inhibiting phenolics biosynthesis and oxidation and enhancing antioxidant capability. Furthermore, the efficacy of IB control by ABA was not obviously affected by tungstate, ABA biosynthesis inhibitor, nor by diphenylene iodonium, NADPH oxidase inhibitor, nor by lanthanum chloride, calcium channel blocker, suggesting that ABA is sufficient for controlling IB. This process might not involve H2O2 generation, but could involve the Ca(2+) channels activation. These results provide potential for developing effective measures for controlling IB in pineapple. PMID:26007196

  12. Growth inhibition of Erwinia amylovora and related Erwinia species by neutralized short‑chain fatty acids.

    PubMed

    Konecki, Katrin; Gernold, Marina; Wensing, Annette; Geider, Klaus

    2013-11-01

    Short-chain fatty acids (SCFAs) are used to preserve food and could be a tool for control of fire blight caused by Erwinia amylovora on apple, pear and related rosaceous plants. Neutralized acids were added to buffered growth media at 0.5–75 mM and tested at pHs ranging from 6.8 to 5.5. Particularly at low pH, SCFAs with a chain length exceeding that of acetic acid such as propionic acid were effective growth inhibitors of E. amylovora possibly due to uptake of free acid and its intracellular accumulation. We also observed high inhibition with monochloroacetic acid. An E. billingiae strain was as sensitive to the acids as E. amylovora or E. tasmaniensis. Fire blight symptoms on pear slices were reduced when the slices were pretreated with neutralized propionic acid. Propionic acid is well water soluble and could be applied in orchards as a control agent for fire blight.

  13. Roles of Gibberellins and Abscisic Acid in Regulating Germination of Suaeda salsa Dimorphic Seeds Under Salt Stress.

    PubMed

    Li, Weiqiang; Yamaguchi, Shinjiro; Khan, M Ajmal; An, Ping; Liu, Xiaojing; Tran, Lam-Son P

    2015-01-01

    Seed heteromorphism observed in many halophytes is an adaptive phenomenon toward high salinity. However, the relationship between heteromorphic seed germination and germination-related hormones under salt stress remains elusive. To gain an insight into this relationship, the roles of gibberellins (GAs) and abscisic acid (ABA) in regulating germination of Suaeda salsa dimorphic brown and black seeds under salinity were elucidated by studying the kinetics of the two hormones during germination of the two seed types with or without salinity treatment. Morphological analysis suggested that brown and black are in different development stage. The content of ABA was higher in dry brown than in black seeds, which gradually decreased after imbibition in water and salt solutions. Salt stress induced ABA accumulation in both germinating seed types, with higher induction effect on black than brown seeds. Black seeds showed lower germination percentage than brown seeds under both water and salt stress, which might be attributed to their higher ABA sensitivity rather than the difference in ABA content between black and brown seeds. Bioactive GA4 and its biosynthetic precursors showed higher levels in brown than in black seeds, whereas deactivated GAs showed higher content in black than brown seeds in dry or in germinating water or salt solutions. High salinity inhibited seed germination through decreasing the levels of GA4 in both seeds, and the inhibited effect of salt stress on GA4 level of black seeds was more profound than that of brown seeds. Taken together higher GA4 content, and lower ABA sensitivity contributed to the higher germination percentage of brown seeds than black seeds in water and salinity; increased ABA content and sensitivity, and decreased GA4 content by salinity were more profound in black than brown seeds, which contributed to lower germination of black seeds than brown seeds in salinity. The differential regulation of ABA and GA homeostases by salt

  14. Roles of Gibberellins and Abscisic Acid in Regulating Germination of Suaeda salsa Dimorphic Seeds Under Salt Stress

    PubMed Central

    Li, Weiqiang; Yamaguchi, Shinjiro; Khan, M. Ajmal; An, Ping; Liu, Xiaojing; Tran, Lam-Son P.

    2016-01-01

    Seed heteromorphism observed in many halophytes is an adaptive phenomenon toward high salinity. However, the relationship between heteromorphic seed germination and germination-related hormones under salt stress remains elusive. To gain an insight into this relationship, the roles of gibberellins (GAs) and abscisic acid (ABA) in regulating germination of Suaeda salsa dimorphic brown and black seeds under salinity were elucidated by studying the kinetics of the two hormones during germination of the two seed types with or without salinity treatment. Morphological analysis suggested that brown and black are in different development stage. The content of ABA was higher in dry brown than in black seeds, which gradually decreased after imbibition in water and salt solutions. Salt stress induced ABA accumulation in both germinating seed types, with higher induction effect on black than brown seeds. Black seeds showed lower germination percentage than brown seeds under both water and salt stress, which might be attributed to their higher ABA sensitivity rather than the difference in ABA content between black and brown seeds. Bioactive GA4 and its biosynthetic precursors showed higher levels in brown than in black seeds, whereas deactivated GAs showed higher content in black than brown seeds in dry or in germinating water or salt solutions. High salinity inhibited seed germination through decreasing the levels of GA4 in both seeds, and the inhibited effect of salt stress on GA4 level of black seeds was more profound than that of brown seeds. Taken together higher GA4 content, and lower ABA sensitivity contributed to the higher germination percentage of brown seeds than black seeds in water and salinity; increased ABA content and sensitivity, and decreased GA4 content by salinity were more profound in black than brown seeds, which contributed to lower germination of black seeds than brown seeds in salinity. The differential regulation of ABA and GA homeostases by salt

  15. Citric acid inhibits development of cataracts, proteinuria and ketosis in streptozotocin (type 1) diabetic rats.

    PubMed

    Nagai, Ryoji; Nagai, Mime; Shimasaki, Satoko; Baynes, John W; Fujiwara, Yukio

    2010-02-26

    Although many fruits such as lemon and orange contain citric acid, little is known about beneficial effects of citric acid on health. Here we measured the effect of citric acid on the pathogenesis of diabetic complications in streptozotocin-induced diabetic rats. Although oral administration of citric acid to diabetic rats did not affect blood glucose concentration, it delayed the development of cataracts, inhibited accumulation of advanced glycation end-products (AGEs) such as N(epsilon)-(carboxyethyl)lysine (CEL) and N(epsilon)-(carboxymethyl)lysine (CML) in lens proteins, and protected against albuminuria and ketosis. We also show that incubation of protein with acetol, a metabolite formed from acetone by acetone monooxygenase, generate CEL, suggesting that inhibition of ketosis by citric acid may lead to the decrease in CEL in lens proteins. These results demonstrate that the oral administration of citric acid ameliorates ketosis and protects against the development of diabetic complications in an animal model of type 1 diabetes.

  16. Role of hydroxyl group in the inhibitive action of benzoic acid toward corrosion of aluminum in nitric acid

    SciTech Connect

    Yadav, P.N.S.; Singh, A.K.; Wadhwani, R.

    1999-10-01

    Corrosion inhibition action of benzoic acid, p-hydroxy benzoic acid, 2-4-dihydroxy benzoic acid, and 3-4-5-trihydroxy benzoic acid toward aluminum alloy 3003 (UNS A93003) in 20% (wt%) nitric acid (HNO{sub 3}) using different concentrations of these compounds at 30 C, 40 C, and 50 C has been studied thoroughly. 3-4-5-trihydroxy benzoic acid (inhibition efficiency (IE): 30% and 72%) was the most effective inhibitor followed by 2-4-dihydroxy benzoic acid (IE: 22% to 62%) p-hydroxy benzoic acid (IE: 11% to 52%), and benzoic acid (IE: 2.5% to 15%). IE increased with concentration and its maximum value was observed at 0.5% concentration of all inhibitors used. The percentage of IE of the inhibitors decreased with an increase in temperature from 30 C to 50 C. Values of heat adsorption and activation energy were calculated from weight loss data, which came out in the range for the reaction occurring at the surface. The behavior of inhibitors studied deviated from the Langmuir isotherm. The IE of higher hydroxy species was improved when more hydroxy centers were added. Anodic and cathodic polarization curves were shifted toward lower current density regions in the presence of inhibitors. This revealed that they were mixed inhibitors.

  17. Salicylhydroxamic acid (SHAM) inhibition of the dissolved inorganic carbon concentrating process in unicellular green algae

    SciTech Connect

    Goyal, A.; Tolbert, N.E. )

    1990-03-01

    Rates of photosynthetic O{sub 2} evolution, for measuring K{sub 0.5}(CO{sub 2} + HCO{sub 3}{sup {minus}}) at pH 7, upon addition of 50 micromolar HCO{sub 3}{sup {minus}} to air-adapted Chlamydomonas, Dunaliella, or Scenedesmus cells, were inhibited up to 90% by the addition of 1.5 to 4.0 millimolar salicylhydroxamic acid (SHAM) to the aqueous medium. The apparent K{sub i}(SHAM) for Chlamydomonas cells was about 2.5 millimolar, but due to low solubility in water effective concentrations would be lower. Salicylhydroxamic acid did not inhibit oxygen evolution or accumulation of bicarbonate by Scenedesmus cells between pH 8 to 11 or by isolated intact chloroplasts from Dunaliella. Thus, salicylhydroxamic acid appears to inhibit CO{sub 2} uptake, whereas previous results indicate that vanadate inhibits bicarbonate uptake. These conclusions were confirmed by three test procedures with three air-adapted algae at pH 7. Salicylhydroxamic acid inhibited the cellular accumulation of dissolved inorganic carbon, the rate of photosynthetic O{sub 2} evolution dependent on low levels of dissolved inorganic carbon (50 micromolar NaHCO{sub 3}), and the rate of {sup 14}CO{sub 2} fixation with 100 micromolar ({sup 14}C)HCO{sub 3}{sup {minus}}. Salicylhydroxamic acid inhibition of O{sub 2} evolution and {sup 14}CO{sub 2}-fixation was reversed by higher levels of NaHCO{sub 3}. Thus, salicylhydroxamic acid inhibition was apparently not affecting steps of photosynthesis other than CO{sub 2} accumulation. Although salicylhydroxamic acid is an inhibitor of alternative respiration in algae, it is not known whether the two processes are related.

  18. Salicylhydroxamic Acid (SHAM) Inhibition of the Dissolved Inorganic Carbon Concentrating Process in Unicellular Green Algae.

    PubMed

    Goyal, A; Tolbert, N E

    1990-03-01

    Rates of photosynthetic O(2) evolution, for measuring K(0.5)(CO(2) + HCO(3) (-)) at pH 7, upon addition of 50 micromolar HCO(3) (-) to air-adapted Chlamydomonas, Dunaliella, or Scenedesmus cells, were inhibited up to 90% by the addition of 1.5 to 4.0 millimolar salicylhydroxamic acid (SHAM) to the aqueous medium. The apparent K(1)(SHAM) for Chlamydomonas cells was about 2.5 millimolar, but due to low solubility in water effective concentrations would be lower. Salicylhydroxamic acid did not inhibit oxygen evolution or accumulation of bicarbonate by Scenedesmus cells between pH 8 to 11 or by isolated intact chloroplasts from Dunaliella. Thus, salicylhydroxamic acid appears to inhibit CO(2) uptake, whereas previous results indicate that vanadate inhibits bicarbonate uptake. These conclusions were confirmed by three test procedures with three air-adapted algae at pH 7. Salicylhydroxamic acid inhibited the cellular accumulation of dissolved inorganic carbon, the rate of photosynthetic O(2) evolution dependent on low levels of dissolved inorganic carbon (50 micromolar Na-HCO(3)), and the rate of (14)CO(2) fixation with 100 micromolar [(14)C] HCO(3) (-). Salicylhydroxamic acid inhibition of O(2) evolution and (14)CO(2)-fixation was reversed by higher levels of NaHCO(3). Thus, salicylhydroxamic acid inhibition was apparently not affecting steps of photosynthesis other than CO(2) accumulation. Although salicylhydroxamic acid is an inhibitor of alternative respiration in algae, it is not known whether the two processes are related.

  19. Abscisic acid: biosynthesis, inactivation, homoeostasis and signalling.

    PubMed

    Dong, Ting; Park, Youngmin; Hwang, Inhwan

    2015-01-01

    The phytohormone abscisic acid (ABA) plays crucial roles in numerous physiological processes during plant growth and abiotic stress responses. The endogenous ABA level is controlled by complex regulatory mechanisms involving biosynthesis, catabolism, transport and signal transduction pathways. This complex regulatory network may target multiple levels, including transcription, translation and post-translational regulation of genes involved in ABA responses. Most of the genes involved in ABA biosynthesis, catabolism and transport have been characterized. The local ABA concentration is critical for initiating ABA-mediated signalling during plant development and in response to environmental changes. In this chapter we discuss the mechanisms that regulate ABA biosynthesis, catabolism, transport and homoeostasis. We also present the findings of recent research on ABA perception by cellular receptors, and ABA signalling in response to cellular and environmental conditions.

  20. Clavulanic acid inhibits MPP⁺-induced ROS generation and subsequent loss of dopaminergic cells.

    PubMed

    Kost, Gina Chun; Selvaraj, Senthil; Lee, Young Bok; Kim, Deog Joong; Ahn, Chang-Ho; Singh, Brij B

    2012-08-21

    Clavulanic acid is a psychoactive compound that has been shown to modulate central nervous system activity. Importantly, in neurotoxin-induced animal models, clavulanic acid has been shown to improve motor function (Huh et al., 2010) suggesting that it can be neuroprotective; however, the mechanism as how clavulanic acid can induce neuroprotection is not known. We demonstrate here that clavulanic acid abrogates the effects of the neurotoxin 1-methyl-4-phenylpyridinium (MPP(+)) which mimics Parkinson's disease (PD) by inducing neurodegeneration. To further establish the mechanism we identified that clavulanic acid inhibits neurotoxin-induced loss of mitochondrial membrane potential and ROS production. Consistent with these results, neurotoxin-induced increase in Bax levels was also decreased in clavulanic acid treated cells. Importantly, neurotoxin-induced release of cytochrome c levels as well as caspase activation was also inhibited in clavulanic acid treated cells. In addition, Bcl-xl levels were also restored and the Bcl-xl/Bax ratio that is critical for inducing apoptosis was increased in clavulanic acid treated cells. Overall, these results suggest that clavulanic acid is intimately involved in inhibiting neurotoxin-induced loss of mitochondrial function and induction of apoptosis that contributes towards neuronal survival.

  1. Clavulanic acid inhibits MPP+-induced ROS generation and subsequent loss of dopaminergic cells☆

    PubMed Central

    Kost, Gina Chun; Selvaraj, Senthil; Lee, Young Bok; Kim, Deog Joong; Ahn, Chang-Ho; Singh, Brij B.

    2013-01-01

    Clavulanic acid is a psychoactive compound that has been shown to modulate central nervous system activity. Importantly, in neurotoxin-induced animal models, clavulanic acid has been shown to improve motor function (Huh et al., 2010) suggesting that it can be neuroprotective; however, the mechanism as how clavulanic acid can induce neuroprotection is not known. We demonstrate here that clavulanic acid abrogates the effects of the neurotoxin 1-methyl-4-phenylpyridinium (MPP+) which mimics Parkinson’s disease (PD) by inducing neurodegeneration. To further establish the mechanism we identified that clavulanic acid inhibits neurotoxin-induced loss of mitochondrial membrane potential and ROS production. Consistent with these results, neurotoxin-induced increase in Bax levels was also decreased in clavulanic acid treated cells. Importantly, neurotoxin-induced release of cytochrome c levels as well as caspase activation was also inhibited in clavulanic acid treated cells. In addition, Bcl-xl levels were also restored and the Bcl-xl/Bax ratio that is critical for inducing apoptosis was increased in clavulanic acid treated cells. Overall, these results suggest that clavulanic acid is intimately involved in inhibiting neurotoxin-induced loss of mitochondrial function and induction of apoptosis that contributes towards neuronal survival. PMID:22750587

  2. Inhibition of enterobacteria and Listeria growth by lactic, acetic and formic acids.

    PubMed

    Ostling, C E; Lindgren, S E

    1993-07-01

    Minimum inhibitory concentrations (MIC) of undissociated lactic, acetic and formic acids were evaluated for 23 strains of enterobacteria and two of Listeria monocytogenes. The evaluation was performed aerobically and anaerobically in a liquid test system at pH intervals of between 4.2 and 5.4. Growth of the enterobacteria was inhibited at 2-11 mmol l-1, 0.5-14 mmol l-1 and 0.1-1.5 mmol l-1 of undissociated lactic, acetic and formic acids, respectively. The MIC value was slightly lower with anaerobic conditions compared with aerobic conditions. The influence of protons on the inhibition was observed for acetic acid at the low pH values. Undissociated lactic acid was 2 to 5 times more efficient in inhibiting L. monocytogenes than enterobacteria. Acetic acid had a similar inhibitory action on L. monocytogenes compared with enterobacteria. Inorganic acid (HCl) inhibited most enterobacteria at pH 4.0; some strains, however, were able to initiate growth to pH 3.8. The results indicate that the values of undissociated acid which occur in a silage of pH 4.1-4.5 are about 10-100 times higher than required in order to protect the forage from the growth of enterobacteria and L. monocytogenes.

  3. A Dual-Function Transcription Factor, AtYY1, Is a Novel Negative Regulator of the Arabidopsis ABA Response Network.

    PubMed

    Li, Tian; Wu, Xiu-Yun; Li, Hui; Song, Jian-Hui; Liu, Jin-Yuan

    2016-05-01

    Abscisic acid (ABA) plays crucial roles in plant growth and development, as well as in response to various environmental stresses. To date, many regulatory genes involved in the ABA response network have been identified; however, their roles have remained to be fully elucidated. In this study, we identified AtYY1, an Arabidopsis homolog of the mammalian C2H2 zinc-finger transcription factor Yin Yang 1 (YY1), as a novel negative regulator of the ABA response. AtYY1 is a dual-function transcription factor with both repression and activation domains. The expression of AtYY1 was induced by ABA and stress conditions including high salt and dehydration. The yy1 mutant was more sensitive to ABA and NaCl than the wild-type, while overexpressing AtYY1 plants were less sensitive. AtYY1 loss also enhanced ABA-induced stomatal closing and drought resistance. Moreover, AtYY1 can bind the ABA REPRESSOR1 (ABR1) promoter and directly upregulate ABR1 expression, as well as negatively regulate ABA- and salt-responsive gene expression. Additional analysis indicated that ABA INSENSITIVE4 (ABI4) might positively regulate AtYY1 expression and that ABR1 can antagonize this regulation. Our findings provide direct evidence that AtYY1 is a novel negative regulator of the ABA response network and that the ABI4-AtYY1-ABR1 regulatory pathway may fine-tune ABA-responsive gene expression in Arabidopsis. PMID:26961720

  4. An Arabidopsis mitochondria-localized RRL protein mediates abscisic acid signal transduction through mitochondrial retrograde regulation involving ABI4.

    PubMed

    Yao, Xuan; Li, Juanjuan; Liu, Jianping; Liu, Kede

    2015-10-01

    The molecular mechanisms of abscisic acid (ABA) signalling have been studied for many years; however, how mitochondria-localized proteins play roles in ABA signalling remains unclear. Here an Arabidopsis mitochondria-localized protein RRL (RETARDED ROOT GROWTH-LIKE) was shown to function in ABA signalling. A previous study had revealed that the Arabidopsis mitochondria-localized protein RRG (RETARDED ROOT GROWTH) is required for cell division in the root meristem. RRL shares 54% and 57% identity at the nucleotide and amino acid sequences, respectively, with RRG; nevertheless, RRL shows a different function in Arabidopsis. In this study, disruption of RRL decreased ABA sensitivity whereas overexpression of RRL increased ABA sensitivity during seed germination and seedling growth. High expression levels of RRL were found in germinating seeds and developing seedlings, as revealed by β-glucuronidase (GUS) staining of ProRRL-GUS transgenic lines. The analyses of the structure and function of mitochondria in the knockout rrl mutant showed that the disruption of RRL causes extensively internally vacuolated mitochondria and reduced ABA-stimulated reactive oxygen species (ROS) production. Previous studies have revealed that the expression of alternative oxidase (AOX) in the alternative respiratory pathway is increased by mitochondrial retrograde regulation to regain ROS levels when the mitochondrial electron transport chain is impaired. The APETALA2 (AP2)-type transcription factor ABI4 is a regulator of ALTERNATIVE OXIDASE1a (AOX1a) in mitochondrial retrograde signalling. This study showed that ABA-induced AOX1a and ABI4 expression was inhibited in the rrl mutant, suggesting that RRL is probably involved in ABI4-mediated mitochondrial retrograde signalling. Furthermore, the results revealed that ABI4 is a downstream regulatory factor in RRL-mediated ABA signalling in seed germination and seedling growth.

  5. Inhibition of lymphoid tyrosine phosphatase by benzofuran salicylic acids.

    PubMed

    Vang, Torkel; Xie, Yuli; Liu, Wallace H; Vidović, Dusica; Liu, Yidong; Wu, Shuangding; Smith, Deborah H; Rinderspacher, Alison; Chung, Caty; Gong, Gangli; Mustelin, Tomas; Landry, Donald W; Rickert, Robert C; Schürer, Stephan C; Deng, Shi-Xian; Tautz, Lutz

    2011-01-27

    The lymphoid tyrosine phosphatase (Lyp, PTPN22) is a critical negative regulator of T cell antigen receptor (TCR) signaling. A single-nucleotide polymorphism (SNP) in the ptpn22 gene correlates with the incidence of various autoimmune diseases, including type 1 diabetes, rheumatoid arthritis, and systemic lupus erythematosus. Since the disease-associated allele is a more potent inhibitor of TCR signaling, specific Lyp inhibitors may become valuable in treating autoimmunity. Using a structure-based approach, we synthesized a library of 34 compounds that inhibited Lyp with IC(50) values between 0.27 and 6.2 μM. A reporter assay was employed to screen for compounds that enhanced TCR signaling in cells, and several inhibitors displayed a dose-dependent, activating effect. Subsequent probing for Lyp's direct physiological targets by immunoblot analysis confirmed the ability of the compounds to inhibit Lyp in T cells. Selectivity profiling against closely related tyrosine phosphatases and in silico docking studies with the crystal structure of Lyp yielded valuable information for the design of Lyp-specific compounds. PMID:21190368

  6. A Role for Arabidopsis miR399f in Salt, Drought, and ABA Signaling

    PubMed Central

    Baek, Dongwon; Chun, Hyun Jin; Kang, Songhwa; Shin, Gilok; Park, Su Jung; Hong, Hyewon; Kim, Chanmin; Kim, Doh Hoon; Lee, Sang Yeol; Kim, Min Chul; Yun, Dae-Jin

    2016-01-01

    MiR399f plays a crucial role in maintaining phosphate homeostasis in Arabidopsis thaliana. Under phosphate starvation conditions, AtMYB2, which plays a role in plant salt and drought stress responses, directly regulates the expression of miR399f. In this study, we found that miR399f also participates in plant responses to abscisic acid (ABA), and to abiotic stresses including salt and drought. Salt and ABA treatment induced the expression of miR399f, as confirmed by histochemical analysis of promoter-GUS fusions. Transgenic Arabidopsis plants overexpressing miR399f (miR399f-OE) exhibited enhanced tolerance to salt stress and exogenous ABA, but hypersensitivity to drought. Our in silico analysis identified ABF3 and CSP41b as putative target genes of miR399f, and expression analysis revealed that mRNA levels of ABF3 and CSP41b decreased remarkably in miR399f-OE plants under salt stress and in response to treatment with ABA. Moreover, we showed that activation of stress-responsive gene expression in response to salt stress and ABA treatment was impaired in miR399f-OE plants. Thus, these results suggested that in addition to phosphate starvation signaling, miR399f might also modulates plant responses to salt, ABA, and drought, by regulating the expression of newly discovered target genes such as ABF3 and CSP41b. PMID:26674968

  7. A new look at stress: abscisic acid patterns and dynamics at high-resolution.

    PubMed

    Jones, Alexander M

    2016-04-01

    Abscisic acid (ABA) is a key phytohormone promoting abiotic stress tolerance as well as developmental processes such as seed dormancy. A spatiotemporal map of ABA concentrations would greatly advance our understanding of the cell type and timing of ABA action. Organ and tissue-level ABA measurements, as well as indirect in vivo measurements such as cell-specific transcriptional analysis of ABA metabolic enzymes and ABA-responsive promoters, have all contributed to current views of the localization and timing of ABA accumulations. Recently developed Förster resonance energy transfer (FRET) biosensors for ABA that sense ABA levels directly promise to add unprecedented resolution to in vivo ABA spatiotemporal mapping and expand our knowledge of the mechanisms controlling ABA levels in space and time.

  8. Suppression of Spermatogenesis by Bisdichloroacetyldiamines Is Mediated by Inhibition of Testicular Retinoic Acid Biosynthesis

    PubMed Central

    Amory, John K.; Muller, Charles H.; Shimshoni, Jakob A.; Isoherranen, Nina; Paik, Jisun; Moreb, Jan S.; Amory, David W.; Evanoff, Ryan; Goldstein, Alex S.; Griswold, Michael D.

    2012-01-01

    The bisdichloroacetyldiamine WIN 18,446 reversibly inhibits spermatogenesis in many species, including humans; however, the mechanism by which WIN 18,446 functions is unknown. As retinoic acid is essential for spermatogenesis, we hypothesized that WIN 18,446 might inhibit retinoic acid biosynthesis from retinol (vitamin A) within the testes by inhibiting the enzyme aldehyde dehydrogenase 1a2 (ALDH1a2). We studied the effect of WIN 18,446 on ALDH1a2 enzyme activity in vitro, and on spermatogenesis and fertility in vivo, in mature male rabbits for 16 weeks. WIN 18,446 markedly inhibited ALDH1a2 enzyme activity in vitro with an IC50 of 0.3 μM. In vivo, the oral administration of 200 mg/kg WIN 18,446 to male rabbits for 16 weeks significantly reduced intratesticular concentrations of retinoic acid, severely impaired spermatogenesis, and caused infertility. Reduced concentrations of intratesticular retinoic acid were apparent after only 4 weeks of treatment and preceded the decrease in sperm counts and the loss of mature germ cells in tissue samples. Sperm counts and fertility recovered after treatment was discontinued. These findings demonstrate that bisdichloroacetyldiamines such as WIN 18,446 reversibly suppress spermatogenesis via inhibition of testicular retinoic acid biosynthesis by ALDH1a2. These findings suggest that ALDH1a2 is a promising target for the development of a reversible, nonhormonal male contraceptive. PMID:20705791

  9. Epoxygenase metabolites of arachidonic acid inhibit vasopressin response in toad bladder

    SciTech Connect

    Schlondorff, D.; Petty, E.; Oates, J.A.; Jacoby, M.; Levine, S.D. Vanderbilt Univ., Nashville, TN )

    1987-09-01

    In addition to cyclooxygenase and lipoxygenase pathways, the kidney can also metabolize arachidonic acid by a NADPH-dependent cytochrome P-450 enzyme to epoxyeicosatrienoic acids (EETs); furthermore, 5,6-EET has been shown to alter electrolyte transport across isolated renal tubules. The authors examined the effects of three ({sup 14}C-labeled)-EETs (5,6-, 11,12-, and 14,15-EET) on osmotic water flow across toad urinary bladder. All three EETs reversibly inhibited vasopressin-stimulated osmotic water flow with 5,6- and 11,12-EET being the most potent. The effects appeared to be independent of prostaglandins EETs inhibited the water flow response to forskolin but not the response to adenosine 3{prime},5{prime}-cyclic monophosphate (cAMP) or 8-BrcAMP, consistent with an effect on cAMP generation. To determine whether these effects were due to the EETs or to products of their metabolism, they examined the effects of their vicinal diol hydrolysis products, the dihydroxyeicosatrienoic acids. Nonenzymatic conversion of labeled 5,6-EET to its vicinal diol occurred rapidly in the buffer, whereas 11,12-EET was hydrolyzed in a saturable manner only when incubated in the presence of bladder tissue. The dihydroxyeicosatrienoic acids formed inhibited water flow in a manner paralleling that of the EETs. The data support the hypothesis that EETs and their physiologically active dihydroxyeicosatrienoic acid metabolites inhibit vasopressin-stimulated water flow predominantly via inhibition of adenylate cyclase.

  10. The Arabidopsis MYB96 Transcription Factor Is a Positive Regulator of ABSCISIC ACID-INSENSITIVE4 in the Control of Seed Germination.

    PubMed

    Lee, Kyounghee; Lee, Hong Gil; Yoon, Seongmun; Kim, Hyun Uk; Seo, Pil Joon

    2015-06-01

    Seed germination is a key developmental transition that initiates the plant life cycle. The timing of germination is determined by the coordinated action of two phytohormones, gibberellin and abscisic acid (ABA). In particular, ABA plays a key role in integrating environmental information and inhibiting the germination process. The utilization of embryonic lipid reserves contributes to seed germination by acting as an energy source, and ABA suppresses lipid degradation to modulate the germination process. Here, we report that the ABA-responsive R2R3-type MYB transcription factor MYB96, which is highly expressed in embryo, regulates seed germination by controlling the expression of abscisic acid-insensitive4 (ABI4) in Arabidopsis (Arabidopsis thaliana). In the presence of ABA, germination was accelerated in MYB96-deficient myb96-1 seeds, whereas the process was significantly delayed in MYB96-overexpressing activation-tagging myb96-ox seeds. Consistently, myb96-1 seeds degraded a larger extent of lipid reserves even in the presence of ABA, while reduced lipid mobilization was observed in myb96-ox seeds. MYB96 directly regulates ABI4, which acts as a repressor of lipid breakdown, to define its spatial and temporal expression. Genetic analysis further demonstrated that ABI4 is epistatic to MYB96 in the control of seed germination. Taken together, the MYB96-ABI4 module regulates lipid mobilization specifically in the embryo to ensure proper seed germination under suboptimal conditions.

  11. The Arabidopsis MYB96 Transcription Factor Is a Positive Regulator of ABSCISIC ACID-INSENSITIVE4 in the Control of Seed Germination1

    PubMed Central

    Lee, Kyounghee; Lee, Hong Gil; Kim, Hyun Uk; Seo, Pil Joon

    2015-01-01

    Seed germination is a key developmental transition that initiates the plant life cycle. The timing of germination is determined by the coordinated action of two phytohormones, gibberellin and abscisic acid (ABA). In particular, ABA plays a key role in integrating environmental information and inhibiting the germination process. The utilization of embryonic lipid reserves contributes to seed germination by acting as an energy source, and ABA suppresses lipid degradation to modulate the germination process. Here, we report that the ABA-responsive R2R3-type MYB transcription factor MYB96, which is highly expressed in embryo, regulates seed germination by controlling the expression of ABSCISIC ACID-INSENSITIVE4 (ABI4) in Arabidopsis (Arabidopsis thaliana). In the presence of ABA, germination was accelerated in MYB96-deficient myb96-1 seeds, whereas the process was significantly delayed in MYB96-overexpressing activation-tagging myb96-ox seeds. Consistently, myb96-1 seeds degraded a larger extent of lipid reserves even in the presence of ABA, while reduced lipid mobilization was observed in myb96-ox seeds. MYB96 directly regulates ABI4, which acts as a repressor of lipid breakdown, to define its spatial and temporal expression. Genetic analysis further demonstrated that ABI4 is epistatic to MYB96 in the control of seed germination. Taken together, the MYB96-ABI4 module regulates lipid mobilization specifically in the embryo to ensure proper seed germination under suboptimal conditions. PMID:25869652

  12. Mechanism of cinnamic acid-induced trypsin inhibition: a multi-technique approach.

    PubMed

    Zhang, Hongmei; Zhou, Qiuhua; Cao, Jian; Wang, Yanqing

    2013-12-01

    In order to investigate the association of the protease trypsin with cinnamic acid, the interaction was characterized by using fluorescence, UV-vis absorption spectroscopy, molecular modeling and an enzymatic inhibition assay. The binding process may be outlined as follows: cinnamic acid can interact with trypsin with one binding site to form cinnamic acid-trypsin complex, resulting in inhibition of trypsin activity; the spectroscopic data show that the interaction is a spontaneous process with the estimated enthalpy and entropy changes being -8.95 kJ mol(-1) and 50.70 J mol(-1) K(-1), respectively. Noncovalent interactions make the main contribution to stabilize the trypsin-cinnamic acid complex; cinnamic acid can enter into the primary substrate-binding pocket and alter the environment around Trp and Tyr residues.

  13. Punicic Acid a Conjugated Linolenic Acid Inhibits TNFα-Induced Neutrophil Hyperactivation and Protects from Experimental Colon Inflammation in Rats

    PubMed Central

    Boussetta, Tarek; Raad, Houssam; Lettéron, Philippe; Gougerot-Pocidalo, Marie-Anne; Marie, Jean-Claude

    2009-01-01

    Background Neutrophils play a major role in inflammation by releasing large amounts of ROS produced by NADPH-oxidase and myeloperoxidase (MPO). The proinflammatory cytokine TNFα primes ROS production through phosphorylation of the NADPH-oxidase subunit p47phox on Ser345. Conventional anti-inflammatory therapies remain partially successful and may have side effects. Therefore, regulation of neutrophil activation by natural dietary components represents an alternative therapeutic strategy in inflammatory diseases such as inflammatory bowel diseases. The aim of this study was to assess the effect of punicic acid, a conjugated linolenic fatty acid from pomegranate seed oil on TNFα-induced neutrophil hyperactivation in vitro and on colon inflammation in vivo. Methodology and Principal Findings We analyzed the effect of punicic acid on TNFα-induced neutrophil upregulation of ROS production in vitro and on TNBS-induced rat colon inflammation. Results show that punicic acid inhibited TNFα-induced priming of ROS production in vitro while preserving formyl-methionyl-leucyl-phenylalanine (fMLP)-induced response. This effect was mediated by the inhibition of Ser345-p47phox phosphorylation and upstream kinase p38MAPK. Punicic acid also inhibited fMLP- and TNFα+fMLP-induced MPO extracellular release from neutrophils. In vivo experiments showed that punicic acid and pomegranate seed oil intake decreased neutrophil-activation and ROS/MPO-mediated tissue damage as measured by F2-isoprostane release and protected rats from TNBS-induced colon inflammation. Conclusions/Significance These data show that punicic acid exerts a potent anti-inflammatory effect through inhibition of TNFα-induced priming of NADPH oxidase by targeting the p38MAPKinase/Ser345-p47phox-axis and MPO release. This natural dietary compound may provide a novel alternative therapeutic strategy in inflammatory diseases such as inflammatory bowel diseases. PMID:19649246

  14. Inhibition of the gravitropic bending response of flowering shoots by salicylic acid.

    PubMed

    Friedman, Haya; Meir, Shimon; Halevy, Abraham H; Philosoph-Hadas, Sonia

    2003-10-01

    The upward gravitropic bending of cut snapdragon, lupinus and anemone flowering shoots was inhibited by salicylic acid (SA) applied at 0.5 mM and above. This effect was probably not due to acidification of the cytoplasm, since other weak acids did not inhibit bending of snapdragon shoots. In order to study its mode of inhibitory action, we have examined in cut snapdragon shoots the effect of SA on three processes of the gravity-signaling pathway, including: amyloplast sedimentation, formation of ethylene gradient across the stem, and differential growth response. The results show that 1 mM SA inhibited differential ethylene production rates across the horizontal stem and the gravity-induced growth, without significantly inhibiting vertical growth or amyloplast sedimentation following horizontal placement. However, 5 mM SA inhibited all three gravity-induced processes, as well as the growth of vertical shoots, while increasing flower wilting. It may, therefore, be concluded that SA inhibits bending of various cut flowering shoots in a concentration-dependent manner. Thus, at a low concentration SA exerts its effect in snapdragon shoots by inhibiting processes operating downstream to stimulus sensing exerted by amyloplast sedimentation. At a higher concentration SA inhibits bending probably by exerting general negative effects on various cellular processes.

  15. Irreversible inhibition of human immunodeficiency virus type 1 integrase by dicaffeoylquinic acids.

    PubMed

    Zhu, K; Cordeiro, M L; Atienza, J; Robinson, W E; Chow, S A

    1999-04-01

    Human immunodeficiency virus type 1 (HIV-1) and other retroviruses require integration of a double-stranded DNA copy of the RNA genome into the host cell chromosome for productive infection. The viral enzyme, integrase, catalyzes the integration of retroviral DNA and represents an attractive target for developing antiretroviral agents. We identified several derivatives of dicaffeoylquinic acids (DCQAs) that inhibit HIV-1 replication in tissue culture and catalytic activities of HIV-1 integrase in vitro. The specific step at which DCQAs inhibit the integration in vitro and the mechanism of inhibition were examined in the present study. Titration experiments with different concentrations of HIV-1 integrase or DNA substrate found that the effect of DCQAs was exerted on the enzyme and not the DNA. In addition to HIV-1, DCQAs also inhibited the in vitro activities of MLV integrase and truncated variants of feline immunodeficiency virus integrase, suggesting that these compounds interacted with the central core domain of integrase. The inhibition on retroviral integrases was relatively specific, and DCQAs had no effect on several other DNA-modifying enzymes and phosphoryltransferases. Kinetic analysis and dialysis experiments showed that the inhibition of integrase by DCQAs was irreversible. The inhibition did not require the presence of a divalent cation and was unaffected by preassembling integrase onto viral DNA. The results suggest that the irreversible inhibition by DCQAs on integrase is directed toward conserved amino acid residues in the central core domain during catalysis.

  16. The RING finger ubiquitin E3 ligase SDIR1 targets SDIR1-INTERACTING PROTEIN1 for degradation to modulate the salt stress response and ABA signaling in Arabidopsis.

    PubMed

    Zhang, Huawei; Cui, Feng; Wu, Yaorong; Lou, Lijuan; Liu, Lijing; Tian, Miaomiao; Ning, Yuese; Shu, Kai; Tang, Sanyuan; Xie, Qi

    2015-01-01

    The plant hormone abscisic acid (ABA) regulates many aspects of plant development and the stress response. The intracellular E3 ligase SDIR1 (SALT- AND DROUGHT-INDUCED REALLY INTERESTING NEW GENE FINGER1) plays a key role in ABA signaling, regulating ABA-related seed germination and the stress response. In this study, we found that SDIR1 is localized on the endoplasmic reticulum membrane in Arabidopsis thaliana. Using cell biology, molecular biology, and biochemistry approaches, we demonstrated that SDIR1 interacts with and ubiquitinates its substrate, SDIRIP1 (SDIR1-INTERACTING PROTEIN1), to modulate SDIRIP1 stability through the 26S proteasome pathway. SDIRIP1 acts genetically downstream of SDIR1 in ABA and salt stress signaling. In detail, SDIRIP1 selectively regulates the expression of the downstream basic region/leucine zipper motif transcription factor gene ABA-INSENSITIVE5, rather than ABA-RESPONSIVE ELEMENTS BINDING FACTOR3 (ABF3) or ABF4, to regulate ABA-mediated seed germination and the plant salt response. Overall, the SDIR1/SDIRIP1 complex plays a vital role in ABA signaling through the ubiquitination pathway. PMID:25616872

  17. The RING Finger Ubiquitin E3 Ligase SDIR1 Targets SDIR1-INTERACTING PROTEIN1 for Degradation to Modulate the Salt Stress Response and ABA Signaling in Arabidopsis

    PubMed Central

    Zhang, Huawei; Cui, Feng; Wu, Yaorong; Lou, Lijuan; Liu, Lijing; Tian, Miaomiao; Ning, Yuese; Shu, Kai; Tang, Sanyuan; Xie, Qi

    2015-01-01

    The plant hormone abscisic acid (ABA) regulates many aspects of plant development and the stress response. The intracellular E3 ligase SDIR1 (SALT- AND DROUGHT-INDUCED REALLY INTERESTING NEW GENE FINGER1) plays a key role in ABA signaling, regulating ABA-related seed germination and the stress response. In this study, we found that SDIR1 is localized on the endoplasmic reticulum membrane in Arabidopsis thaliana. Using cell biology, molecular biology, and biochemistry approaches, we demonstrated that SDIR1 interacts with and ubiquitinates its substrate, SDIRIP1 (SDIR1-INTERACTING PROTEIN1), to modulate SDIRIP1 stability through the 26S proteasome pathway. SDIRIP1 acts genetically downstream of SDIR1 in ABA and salt stress signaling. In detail, SDIRIP1 selectively regulates the expression of the downstream basic region/leucine zipper motif transcription factor gene ABA-INSENSITIVE5, rather than ABA-RESPONSIVE ELEMENTS BINDING FACTOR3 (ABF3) or ABF4, to regulate ABA-mediated seed germination and the plant salt response. Overall, the SDIR1/SDIRIP1 complex plays a vital role in ABA signaling through the ubiquitination pathway. PMID:25616872

  18. Kinetics of Inhibition of Monoamine Oxidase Using Curcumin and Ellagic Acid

    PubMed Central

    Khatri, Dharmendra Kumar; Juvekar, Archana Ramesh

    2016-01-01

    Background: Curcumin and ellagic are the natural polyphenols having a wide range of pharmacological actions. They have been reported to have their use in various neurological disorders. Objective: This study was aimed to evaluate the effect of curcumin and ellagic acid on the activity of monoamine oxidase (MAO), the enzyme responsible for metabolism of monoamine neurotransmitters which are pivotal for neuronal development and function. Materials and Methods: The in vitro effects of these selected polyphenols on MAO activities in mitochondria isolated from rat brains were examined. Brain mitochondria were assayed for MAO type-B (MAO-B) using benzylamine as substrates. Rat brain mitochondrial MAO preparation was used to study the kinetics of enzyme inhibition using double reciprocal Lineweaver–Burk plot. Results: MAO activity was inhibited by curcumin and ellagic acid; however, higher half maximal inhibitory concentrations of curcumin (500.46 nM) and ellagic acid (412.24 nM) were required compared to the known MAO-B inhibitor selegiline. It is observed that the curcumin and ellagic acid inhibit the MAO activity with both the competitive and noncompetitive type of inhibitions. Conclusions: Curcumin and ellagic acid can be considered a possible source of MAO inhibitor used in the treatment of Parkinson's and other neurological disorders. SUMMARY Monoamine oxidase (MAO) is involved in a variety of neurological disorders including Parkinson's disease (PD)Curcumin and ellagic acid inhibit the monoamine oxidase activityEllagic acid revealed more potent MAO type-B (MAO-B) inhibitory activity than curcuminKinetic studies of MAO inhibition using different concentrations of curcumin and ellagic acid were plotted as double reciprocal Lineweaver–Burk plotThe mode of inhibition of both compounds toward MAO-B is mixed (competitive and uncompetitive) type of inhibition with both the competitive and noncompetitive type of inhibitions. Abbreviations used: MAO: Monoamine oxidase

  19. Abscisic acid and blue light signaling pathways in chloroplast movements in Arabidopsis mesophyll.

    PubMed

    Eckstein, Aleksandra; Krzeszowiec, Weronika; Banaś, Agnieszka Katarzyna; Janowiak, Franciszek; Gabryś, Halina

    2016-01-01

    Abscisic acid (ABA) and phototropins act antagonistically to control stomatal movements. Here, we investigated the role of ABA in phototropin-directed chloroplast movements in mesophyll cells of Arabidopsis thaliana. We analyzed the expression of phototropins at mRNA and protein level under the influence of ABA. PHOT1 mRNA level was decreased by ABA in the dark while it was insensitive to ABA in light. PHOT2 mRNA level was independent of the hormone treatment. The levels of phototropin proteins were down-regulated by ABA, both in darkness and light. No impact of exogenous ABA on amplitudes and kinetics of chloroplast movements was detected. Chloroplast responses in wild type Arabidopsis and three mutants, abi4, abi2 (abscisic acid insensitive4, 2) and aba1 (abscisic acid1), were measured to account for endogenous ABA signaling. The chloroplast responses were slightly reduced in abi2 and aba1 mutants in strong light. To further investigate the effect, abi2 and aba1 mutants were supplemented with exogenous ABA. In the aba1 mutant, the reaction was rescued but in abi2 it was unaffected. Our results show that ABA is not directly involved in phototropin-controlled chloroplast responses in mature leaves of Arabidopsis. However, the disturbance of ABA biosynthesis and signaling in mutants affects some elements of the chloroplast movement mechanism. In line with its role as a stress hormone, ABA appears to enhance plant sensitivity to light and promote the chloroplast avoidance response.

  20. Abscisic acid and blue light signaling pathways in chloroplast movements in Arabidopsis mesophyll.

    PubMed

    Eckstein, Aleksandra; Krzeszowiec, Weronika; Banaś, Agnieszka Katarzyna; Janowiak, Franciszek; Gabryś, Halina

    2016-01-01

    Abscisic acid (ABA) and phototropins act antagonistically to control stomatal movements. Here, we investigated the role of ABA in phototropin-directed chloroplast movements in mesophyll cells of Arabidopsis thaliana. We analyzed the expression of phototropins at mRNA and protein level under the influence of ABA. PHOT1 mRNA level was decreased by ABA in the dark while it was insensitive to ABA in light. PHOT2 mRNA level was independent of the hormone treatment. The levels of phototropin proteins were down-regulated by ABA, both in darkness and light. No impact of exogenous ABA on amplitudes and kinetics of chloroplast movements was detected. Chloroplast responses in wild type Arabidopsis and three mutants, abi4, abi2 (abscisic acid insensitive4, 2) and aba1 (abscisic acid1), were measured to account for endogenous ABA signaling. The chloroplast responses were slightly reduced in abi2 and aba1 mutants in strong light. To further investigate the effect, abi2 and aba1 mutants were supplemented with exogenous ABA. In the aba1 mutant, the reaction was rescued but in abi2 it was unaffected. Our results show that ABA is not directly involved in phototropin-controlled chloroplast responses in mature leaves of Arabidopsis. However, the disturbance of ABA biosynthesis and signaling in mutants affects some elements of the chloroplast movement mechanism. In line with its role as a stress hormone, ABA appears to enhance plant sensitivity to light and promote the chloroplast avoidance response. PMID:27486921

  1. Abscisic acid promotes accumulation of toxin ODAP in relation to free spermine level in grass pea seedlings (Lathyrus sativus L.).

    PubMed

    Xiong, You-Cai; Xing, Geng-Mei; Li, Feng-Min; Wang, Shao-Ming; Fan, Xian-Wei; Li, Zhi-Xiao; Wang, Ya-Fu

    2006-01-01

    Interrelationship among abscisic acid (ABA) content, accumulation of free polyamines and biosynthesis of beta-N-oxalyl-l-alpha,beta-diaminopropionic acid (ODAP) was studied in grass pea (Lathyrus sativus L.) seedlings under drought stress induced by 10% polyethylene glycol (PEG6000). Increase of ABA content occurred prior to that of ODAP and polyamine contents, and was found significantly positive correlation between ABA content and ODAP content. Addition of exogenous ABA increased ODAP content in leaves. On the other hand, pretreatment with alpha-difluoromethylarginine (DFMA), a polyamine biosynthesis inhibitor, significantly suppressed the accumulation of free putrescine (Put), free spermidine (Spd) and free spermine (Spm), which in turn inhibited biosynthesis of ODAP in well-watered leaves. Meanwhile, addition of exogenous Put alleviated DFMA-induced inhibition on the biosynthesis of Put and Spd, but did not affect the biosynthesis of Spm and ODAP in well-watered leaves. Same result was also achieved in drought-stressed leaves. Increasing accumulation of ODAP was significantly correlated with increasing Spm content (R=0.7957**) but not with that of Spd and Put. Therefore, it can be argued that ABA stimulated the biosynthesis of ODAP simultaneously with increasing the level of free Spm under drought stress condition.

  2. MhNCED3 in Malus hupehensis Rehd. induces NO generation under osmotic stress by regulating ABA accumulation.

    PubMed

    Zhang, Wei-wei; Yang, Hong-qiang; You, Shu-zhen; Ran, Kun

    2015-11-01

    Abscisic acid (ABA) biosynthesis has been widely characterized in plants, whereas the effects of ABA biosynthesis on nitric oxide (NO) generation in osmotic stress are less well understood. In this study, Malus hupehensis Rehd. 9-cis-epoxycarotenoid dioxygenase gene (MhNCED3) which is the key gene in ABA biosynthesis was transformed into wild type (WT) and 129B08/nced3 mutant (AtNCED3 deficient), respectively, and two transgenic Arabidopsis lines were obtained. The transgenic Arabidopsis lines displayed higher endogenous ABA content, NO generation rate, AtNIA1 transcript level and nitrate reductase (NR) activity than WT and 129B08/nced3 mutant. Ectopic expression of MhNCED3 reduced the electrolyte leakage and relieved Arabidopsis damage caused by 20% PEG on the growth and development. The ABA content, NO generation rate, AtNIA1 expression and NR activity increased after 20% PEG treatment, importantly, their increases amplitude relative to that in control were higher in two transgenic lines. Additionally, during the treatment for the four genotype Arabidopsis, the time of ABA contents reaching the highest peak was earlier than the time of NO generation, AtNIA1 expression and NR activity reaching their highest peak. These results show that NCED gene indirectly induced endogenous NO generation in osmotic-stressed Arabidopsis partially contributing to the up-regulation of AtNIA1 expression and NR activity.

  3. Carbon dioxide enrichment alleviates heat stress by improving cellular redox homeostasis through an ABA-independent process in tomato plants.

    PubMed

    Li, X; Ahammed, G J; Zhang, Y Q; Zhang, G Q; Sun, Z H; Zhou, J; Zhou, Y H; Xia, X J; Yu, J Q; Shi, K

    2015-01-01

    Plant responses to elevated CO₂ and high temperature are critically regulated through a complex network of phytohormones and redox homeostasis. However, the involvement of abscisic acid (ABA) in plant adaptation to heat stress under elevated CO₂ conditions has not been thoroughly studied. This study investigated the interactive effects of elevated CO₂ (800 μmol·mol(-1) ) and heat stress (42 °C for 24 h) on the endogenous level of ABA and the cellular redox state of two genotypes of tomato with different ABA biosynthesis capacities. Heat stress significantly decreased maximum photochemical efficiency of PSII (Fv/Fm) and leaf water potential, but also increased levels of malondialdehyde (MDA) and electrolyte leakage (EL) in both genotypes. Heat-induced damage was more severe in the ABA-deficient mutant notabilis (not) than in its parental cultivar Ailsa Craig (Ailsa), suggesting that a certain level of endogenous ABA is required to minimise the heat-induced oxidative damage to the photosynthetic apparatus. Irrespective of genotype, the enrichment of CO₂ remarkably stimulated Fv/Fm, MDA and EL in heat-stressed plants towards enhanced tolerance. In addition, elevated CO₂ significantly strengthened the antioxidant capacity of heat-stressed tomato seedlings towards a reduced cellular redox state for a prolonged period, thereby mitigating oxidative stress. However, elevated CO₂ and heat stress did not alter the endogenous level of ABA or the expression of its biosynthetic gene NCED2 in either genotype, indicating that ABA is not involved in elevated CO₂ -induced heat stress alleviation. The results of this study suggest that elevated CO₂ alleviated heat stress through efficient regulation of the cellular redox poise in an ABA-independent manner in tomato plants.

  4. Transcriptional regulation of genes encoding ABA metabolism enzymes during the fruit development and dehydration stress of pear 'Gold Nijisseiki'.

    PubMed

    Dai, Shengjie; Li, Ping; Chen, Pei; Li, Qian; Pei, Yuelin; He, Suihuan; Sun, Yufei; Wang, Ya; Kai, Wenbin; Zhao, Bo; Liao, Yalan; Leng, Ping

    2014-09-01

    To investigate the contribution of abscisic acid (ABA) in pear 'Gold Nijisseiki' during fruit ripening and under dehydration stress, two cDNAs (PpNCED1 and PpNCED2) which encode 9-cis-epoxycarotenoid dioxygenase (NCED) (a key enzyme in ABA biosynthesis), two cDNAs (PpCYP707A1 and PpCYP707A2) which encode 8'-hydroxylase (a key enzyme in the oxidative catabolism of ABA), one cDNA (PpACS3) which encodes 1-aminocyclopropane-1-carboxylic acid (ACC), and one cDNA (PpACO1) which encodes ACC oxidase involved in ethylene biosynthesis were cloned from 'Gold Nijisseiki' fruit. In the pulp, peel and seed, expressions of PpNCED1 and PpNCED2 rose in two stages which corresponded with the increase of ABA levels. The expression of PpCYP707A1 dramatically declined after 60-90 days after full bloom (DAFB) in contrast to the changes of ABA levels during this period, while PpCYP707A2 stayed low during the whole development of fruit. Application of exogenous ABA at 100 DAFB increased the soluble sugar content and the ethylene release but significantly decreased the titratable acid and chlorophyll contents in fruits. When fruits harvested at 100 DAFB were stored in the laboratory (25 °C, 50% relative humidity), the ABA content and the expressions of PpNCED1/2 and PpCYP707A1 in the pulp, peel and seed increased significantly, while ethylene reached its highest value after the maximum peak of ABA accompanied with the expressions of PpACS3 and PpACO1. In sum the endogenous ABA may play an important role in the fruit ripening and dehydration of pear 'Gold Nijisseiki' and the ABA level was regulated mainly by the dynamics of PpNCED1, PpNCED2 and PpCYP707A1 at the transcriptional level.

  5. Eicosopentaneoic Acid and Other Free Fatty Acid Receptor Agonists Inhibit Lysophosphatidic Acid- and Epidermal Growth Factor-Induced Proliferation of Human Breast Cancer Cells

    PubMed Central

    Hopkins, Mandi M.; Zhang, Zhihong; Liu, Ze; Meier, Kathryn E.

    2016-01-01

    Many key actions of ω-3 (n-3) fatty acids have recently been shown to be mediated by two G protein-coupled receptors (GPCRs) in the free fatty acid receptor (FFAR) family, FFA1 (GPR40) and FFA4 (GPR120). n-3 Fatty acids inhibit proliferation of human breast cancer cells in culture and in animals. In the current study, the roles of FFA1 and FFA4 were investigated. In addition, the role of cross-talk between GPCRs activated by lysophosphatidic acid (LPA), and the tyrosine kinase receptor activated by epidermal growth factor (EGF), was examined. In MCF-7 and MDA-MB-231 human breast cancer cell lines, both LPA and EGF stimulated proliferation, Erk activation, Akt activation, and CCN1 induction. LPA antagonists blocked effects of LPA and EGF on proliferation in MCF-7 and MDA-MB-231, and on cell migration in MCF-7. The n-3 fatty acid eicosopentaneoic acid inhibited LPA- and EGF-induced proliferation in both cell lines. Two synthetic FFAR agonists, GW9508 and TUG-891, likewise inhibited LPA- and EGF-induced proliferation. The data suggest a major role for FFA1, which was expressed by both cell lines. The results indicate that n-3 fatty acids inhibit breast cancer cell proliferation via FFARs, and suggest a mechanism involving negative cross-talk between FFARS, LPA receptors, and EGF receptor. PMID:26821052

  6. High Molecular Weight Hyaluronic Acid Inhibits Fibrosis of Endometrium

    PubMed Central

    Zhu, Yi; Hu, Jianguo; Yu, Tinghe; Ren, Yan; Hu, Lina

    2016-01-01

    Background Elevated fibrosis has been found in patients with intrauterine adhesion, which indicates that fibrotic factors may play a critical role in formation of intrauterine adhesion. The aim of this study was to identify the effect of hyaluronic acid (HA) at high and low molecular weight on fibrosis of the endometrium in a mouse model of Asherman’s syndrome. Material/Methods Endometrial fibrosis in a mouse model of Asherman’s syndrome was confirmed. Then HA at high and low molecular weight was injected into the uterine cavity. Endometrial fibrosis was compared among the control group, LMW-HA, and HMW-HA group. The extent of endometrial fibrosis was calculated using Masson stain. The fibrosis markers (TGFβ1, CTGF, collagen I, and collagen III) in endometrial tissue were detected using immunohistochemistry and Western blotting. Results The ratio of the area with endometrial fibrosis to total endometrial area in the HMW-HA group was significantly decreased compared to the control group (P<0.05). The expression of fibrosis markers (TGFβ1, CTGF, collagen I, and collagen III) in the endometrium was attenuated in the HMW-HA group compared to the control group, but the LMW-HA group had no similar effect. Conclusions Hyaluronic acid at high molecular weight may attenuate the degree of endometrial fibrosis after endometrial damage, which may contribute to preventing formation of intrauterine adhesions. PMID:27670361

  7. Sphingoid bases inhibit acid-induced demineralization of hydroxyapatite.

    PubMed

    Valentijn-Benz, Marianne; van 't Hof, Wim; Bikker, Floris J; Nazmi, Kamran; Brand, Henk S; Sotres, Javier; Lindh, Liselott; Arnebrant, Thomas; Veerman, Enno C I

    2015-01-01

    Calcium hydroxyapatite (HAp), the main constituent of dental enamel, is inherently susceptible to the etching and dissolving action of acids, resulting in tooth decay such as dental caries and dental erosion. Since the prevalence of erosive wear is gradually increasing, there is urgent need for agents that protect the enamel against erosive attacks. In the present study we studied in vitro the anti-erosive effects of a number of sphingolipids and sphingoid bases, which form the backbone of sphingolipids. Pretreatment of HAp discs with sphingosine, phytosphingosine (PHS), PHS phosphate and sphinganine significantly protected these against acid-induced demineralization by 80 ± 17%, 78 ± 17%, 78 ± 7% and 81 ± 8%, respectively (p < 0.001). On the other hand, sphingomyelin, acetyl PHS, octanoyl PHS and stearoyl PHS had no anti-erosive effects. Atomic force measurement revealed that HAp discs treated with PHS were almost completely and homogeneously covered by patches of PHS. This suggests that PHS and other sphingoid bases form layers on the surface of HAp, which act as diffusion barriers against H(+) ions. In principle, these anti-erosive properties make PHS and related sphingosines promising and attractive candidates as ingredients in oral care products.

  8. Nitric oxide negatively regulates abscisic acid signaling in guard cells by S-nitrosylation of OST1.

    PubMed

    Wang, Pengcheng; Du, Yanyan; Hou, Yueh-Ju; Zhao, Yang; Hsu, Chuan-Chih; Yuan, Feijuan; Zhu, Xiaohong; Tao, W Andy; Song, Chun-Peng; Zhu, Jian-Kang

    2015-01-13

    The phytohormone abscisic acid (ABA) plays important roles in plant development and adaptation to environmental stress. ABA induces the production of nitric oxide (NO) in guard cells, but how NO regulates ABA signaling is not understood. Here, we show that NO negatively regulates ABA signaling in guard cells by inhibiting open stomata 1 (OST1)/sucrose nonfermenting 1 (SNF1)-related protein kinase 2.6 (SnRK2.6) through S-nitrosylation. We found that SnRK2.6 is S-nitrosylated at cysteine 137, a residue adjacent to the kinase catalytic site. Dysfunction in the S-nitrosoglutathione (GSNO) reductase (GSNOR) gene in the gsnor1-3 mutant causes NO overaccumulation in guard cells, constitutive S-nitrosylation of SnRK2.6, and impairment of ABA-induced stomatal closure. Introduction of the Cys137 to Ser mutated SnRK2.6 into the gsnor1-3/ost1-3 double-mutant partially suppressed the effect of gsnor1-3 on ABA-induced stomatal closure. A cysteine residue corresponding to Cys137 of SnRK2.6 is present in several yeast and human protein kinases and can be S-nitrosylated, suggesting that the S-nitrosylation may be an evolutionarily conserved mechanism for protein kinase regulation.

  9. Nitric oxide negatively regulates abscisic acid signaling in guard cells by S-nitrosylation of OST1

    PubMed Central

    Wang, Pengcheng; Du, Yanyan; Hou, Yueh-Ju; Zhao, Yang; Hsu, Chuan-Chih; Yuan, Feijuan; Zhu, Xiaohong; Tao, W. Andy; Song, Chun-Peng; Zhu, Jian-Kang

    2015-01-01

    The phytohormone abscisic acid (ABA) plays important roles in plant development and adaptation to environmental stress. ABA induces the production of nitric oxide (NO) in guard cells, but how NO regulates ABA signaling is not understood. Here, we show that NO negatively regulates ABA signaling in guard cells by inhibiting open stomata 1 (OST1)/sucrose nonfermenting 1 (SNF1)-related protein kinase 2.6 (SnRK2.6) through S-nitrosylation. We found that SnRK2.6 is S-nitrosylated at cysteine 137, a residue adjacent to the kinase catalytic site. Dysfunction in the S-nitrosoglutathione (GSNO) reductase (GSNOR) gene in the gsnor1-3 mutant causes NO overaccumulation in guard cells, constitutive S-nitrosylation of SnRK2.6, and impairment of ABA-induced stomatal closure. Introduction of the Cys137 to Ser mutated SnRK2.6 into the gsnor1-3/ost1-3 double-mutant partially suppressed the effect of gsnor1-3 on ABA-induced stomatal closure. A cysteine residue corresponding to Cys137 of SnRK2.6 is present in several yeast and human protein kinases and can be S-nitrosylated, suggesting that the S-nitrosylation may be an evolutionarily conserved mechanism for protein kinase regulation. PMID:25550508

  10. alpha-Lipoic acid inhibits inflammatory bone resorption by suppressing prostaglandin E2 synthesis.

    PubMed

    Ha, Hyunil; Lee, Jong-Ho; Kim, Ha-Neui; Kim, Hyun-Man; Kwak, Han Bok; Lee, Seungbok; Kim, Hong-Hee; Lee, Zang Hee

    2006-01-01

    alpha-Lipoic acid (LA) has been intensely investigated as a therapeutic agent for several pathological conditions, including diabetic polyneuropathy. In the present study, we examined the effects of LA on osteoclastic bone loss associated with inflammation. LA significantly inhibited IL-1-induced osteoclast formation in cocultures of mouse osteoblasts and bone marrow cells, but LA had only a marginal effect on osteoclastogenesis from bone marrow macrophages induced by receptor activator of NF-kappaB ligand (RANKL). LA inhibited both the sustained up-regulation of RANKL expression and the production of PGE2 induced by IL-1 in osteoblasts. In addition, treatment with either prostaglandin E2 (PGE2) or RANKL rescued IL-1-induced osteoclast formation inhibited by LA or NS398, a specific cyclooxygenase-2 (COX-2) inhibitor, in cocultures. LA blocked IL-1-induced PGE2 production even in the presence of arachidonic acid, without affecting the expression of COX-2 and membrane-bound PGE2 synthase. Dihydrolipoic acid (the reduced form of LA), but not LA, attenuated recombinant COX-2 activity in vitro. LA also inhibited osteoclast formation and bone loss induced by IL-1 and LPS in mice. Our results suggest that the reduced form of LA inhibits COX-2 activity, PGE2 production, and sustained RANKL expression, thereby inhibiting osteoclast formation and bone loss in inflammatory conditions.

  11. Inhibition of nitrogen fixation in alfalfa by arsenate, heavy metals, fluoride, and simulated Acid rain.

    PubMed

    Porter, J R; Sheridan, R P

    1981-07-01

    The acute effects of aqueous solutions of As, Cd, Cu, Pb, F, and Zn ions at concentrations from 0.01 to 100 micrograms per milliliter and solutions adjusted to pH 2 to 6 with nitric or sulfuric acid were studied with respect to acetylene reduction, net photosynthesis, respiration rate, and chlorophyll content in Vernal alfalfa (Medicago sativa L. cv. Vernal). The effects of the various treatments on acetylene reduction varied from no demonstrable effect by any concentration of F(-) and 42% inhibition by 100 micrograms Pb(2+) per milliliter, to 100% inhibition by 10 micrograms Cd(2+) per milliliter and 100 micrograms per milliliter As, Cu(2+), and Zn(2+) ions. Zn(2+) showed statistically significant inhibition of activity at 0.1 micrograms per milliliter. Acid treatments were not inhibitory above pH 2, at which pH nitric acid inhibited acetylene reduction activity more than did sulfuric acid. The inhibition of acetylene reduction by these ions was Zn(2+) > Cd(2+) > Cu(2+) > AsO(3) (-) > Pb(2+) > F(-). The sensitivity of acetylene reduction to the ions was roughly equal to the sensitivity of photosynthesis, respiration, and chlorophyll content when Pb(2+) was applied, but was 1,000 times more sensitive to Zn(2+). The relationship of the data to field conditions and industrial pollution is discussed.

  12. Inhibition of Nitrogen Fixation in Alfalfa by Arsenate, Heavy Metals, Fluoride, and Simulated Acid Rain

    PubMed Central

    Porter, John R.; Sheridan, Richard P.

    1981-01-01

    The acute effects of aqueous solutions of As, Cd, Cu, Pb, F, and Zn ions at concentrations from 0.01 to 100 micrograms per milliliter and solutions adjusted to pH 2 to 6 with nitric or sulfuric acid were studied with respect to acetylene reduction, net photosynthesis, respiration rate, and chlorophyll content in Vernal alfalfa (Medicago sativa L. cv. Vernal). The effects of the various treatments on acetylene reduction varied from no demonstrable effect by any concentration of F− and 42% inhibition by 100 micrograms Pb2+ per milliliter, to 100% inhibition by 10 micrograms Cd2+ per milliliter and 100 micrograms per milliliter As, Cu2+, and Zn2+ ions. Zn2+ showed statistically significant inhibition of activity at 0.1 micrograms per milliliter. Acid treatments were not inhibitory above pH 2, at which pH nitric acid inhibited acetylene reduction activity more than did sulfuric acid. The inhibition of acetylene reduction by these ions was Zn2+ > Cd2+ > Cu2+ > AsO3− > Pb2+ > F−. The sensitivity of acetylene reduction to the ions was roughly equal to the sensitivity of photosynthesis, respiration, and chlorophyll content when Pb2+ was applied, but was 1,000 times more sensitive to Zn2+. The relationship of the data to field conditions and industrial pollution is discussed. PMID:16661858

  13. Nucleic acid-based inhibition of flavivirus infections.

    PubMed

    Stein, David A; Shi, Pei-Yong

    2008-01-01

    The genus Flavivirus in the family Flaviviridae consists of many arthropod-transmitted human pathogens, including dengue, yellow fever, Japanese encephalitis, West Nile, St. Louis encephalitis, Murray Valley encephalitis, and tick-borne encephalitis viruses. Treatment options against flaviviral disease are extremely limited, with no effective drugs yet commercially available. Recent advances in virology, synthetic organic chemistry, and the discovery of RNA interference (RNAi), have provided the basis for advances in the development of antisense-based approaches to address flaviviral infections. Oligomers of various antisense structural types, targeted to different locations in the flaviviral RNA genome, have now been used to successfully suppress viral gene expression and thereby inhibit flavivirus replication. Double-stranded RNA, containing viral sequence and designed to induce the endogenous cellular machinery of RNAi, has also been shown capable of potently interfering with flavivirus production and transmission. These studies provide insights into flaviviral molecular biology and the basis for the development of novel therapeutic approaches. The goal of this review is to summarize the findings of many of the significant reports that have appeared on the topic of antisense-mediated strategies for the development of antiviral therapy for flaviviruses.

  14. The effects of GA and ABA treatments on metabolite profile of germinating barley.

    PubMed

    Huang, Yuqing; Cai, Shengguan; Ye, Lingzhen; Hu, Hongliang; Li, Chengdao; Zhang, Guoping

    2016-02-01

    Sugar degradation during grain germination is important for malt quality. In malting industry, gibberellin (GA) is frequently used for improvement of malting quality. In this study, the changes of metabolite profiles and starch-degrading enzymes during grain germination, and as affected by GA and abscisic acid (ABA) were investigated using two wild barley accessions XZ72 and XZ95. Totally fifty-two metabolites with known structures were detected and the change of metabolite during germination was time- and genotype dependent. Sugars and amino acids were the most dramatically changed compounds. Addition of GA enhanced the activities of starch-degrading enzymes, and increased most metabolites, especially sugars and amino acids, whereas ABA had the opposite effect. The effect varied with the barley accessions. The current study is the first attempt in investigating the effect of hormones on metabolite profiles in germinating barley grain, being helpful for identifying the factors affecting barley germination or malt quality. PMID:26304431

  15. Inhibition of multiplication of the prototypic arenavirus LCMV by valproic acid

    PubMed Central

    Vázquez-Calvo, Ángela; Martín-Acebes, Miguel A.; Sáiz, Juan-Carlos; Ngo, Nhi; Sobrino, F.; de la Torre, Juan Carlos

    2013-01-01

    Valproic acid (VPA), a short chain fatty acid commonly used for treatment of neurological disorders, has been shown to inhibit production of infectious progeny of different enveloped viruses including the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV). In this study we have investigated the mechanisms by which VPA inhibits LCMV multiplication in cultured cells. VPA reduced production of infectious LCMV progeny and virus propagation without exerting a major blockage on either viral RNA or protein synthesis, but rather affecting the cell release and specific infectivity of LCMV progeny from infected cells. Our results would support the repurposing of VPA as a candidate antiviral drug to combat arenavirus infections. PMID:23735299

  16. Crystal structure of the thioesterase domain of human fatty acid synthase inhibited by orlistat

    SciTech Connect

    Pemble,C.; Johnson, L.; Kridel, S.; Lowther, W.

    2007-01-01

    Human fatty acid synthase (FAS) is uniquely expressed at high levels in many tumor types. Pharmacological inhibition of FAS therefore represents an important therapeutic opportunity. The drug Orlistat, which has been approved by the US Food and Drug Administration, inhibits FAS, induces tumor cell-specific apoptosis and inhibits the growth of prostate tumor xenografts. We determined the 2.3-{angstrom}-resolution crystal structure of the thioesterase domain of FAS inhibited by Orlistat. Orlistat was captured in the active sites of two thioesterase molecules as a stable acyl-enzyme intermediate and as the hydrolyzed product. The details of these interactions reveal the molecular basis for inhibition and suggest a mechanism for acyl-chain length discrimination during the FAS catalytic cycle. Our findings provide a foundation for the development of new cancer drugs that target FAS.

  17. A key ABA catabolic gene, OsABA8ox3, is involved in drought stress resistance in rice.

    PubMed

    Cai, Shanlan; Jiang, Guobin; Ye, Nenghui; Chu, Zhizhan; Xu, Xuezhong; Zhang, Jianhua; Zhu, Guohui

    2015-01-01

    Expressions of ABA biosynthesis genes and catabolism genes are generally co-regulated in plant development and responses to environmental stress. Up-regulation of OsNCED3 gene, a key gene in ABA biosynthesis, has been suggested as a way to enhance plant drought resistance but little is known for the role of ABA catabolic genes during drought stress. In this study, we found that OsABA8ox3 was the most highly expressed gene of the OsABA8ox family in rice leaves. Expression of OsABA8ox3 was promptly induced by rehydration after PEG-mimic dehydration, a tendency opposite to the changes of ABA level. We therefore constructed rice OsABA8ox3 silencing (RNA interference, RNAi) and overexpression plants. There were no obvious phenotype differences between the transgenic seedlings and wild type under normal condition. However, OsABA8ox3 RNAi lines showed significant improvement in drought stress tolerance while the overexpression seedlings were hypersensitive to drought stress when compared with wild type in terms of plant survival rates after 10 days of unwatering. Enzyme activity analysis indicated that OsABA8ox3 RNAi plants had higher superoxide dismutase (SOD) and catalase (CAT) activities and less malondialdehyde (MDA) content than those of wild type when the plants were exposed to dehydration treatment, indicating a better anti-oxidative stress capability and less membrane damage. DNA microarray and real-time PCR analysis under dehydration treatment revealed that expressions of a group of stress/drought-related genes, i.e. LEA genes, were enhanced with higher transcript levels in OsABA8ox3 RNAi transgenic seedlings. We therefore conclude that that OsABA8ox3 gene plays an important role in controlling ABA level and drought stress resistance in rice. PMID:25647508

  18. Inhibition of arachidonic acid metabolism decreases tumor cell invasion and matrix metalloproteinase expression.

    PubMed

    Koontongkaew, Sittichai; Monthanapisut, Paopanga; Saensuk, Theeranuch

    2010-11-01

    Head and neck cancers are known to synthesize arachidonic acid metabolites. Interfering with arachidonic acid metabolism may inhibit growth and invasiveness of cancer cells. In this study we investigate effects of sulindac (the non-selective COX inhibitor), aspirin (the irreversible, preferential COX-1 inhibitor), NS-398 (the selective COX-2 inhibitor), NDGA (nordihydroguaiaretic acid, the selective LOX inhibitor) and ETYA (5,8,11,14-eicosatetraynoic acid, the COX and LOX inhibitor) on cell viability, MMP-2 and MMP-9 activities, and in vitro invasion of cancer cells derived from primary and metastatic head and neck, and colon cancers. The inhibitors of COX and/or LOX could inhibit cell proliferation, MMP activity and invasion in head and neck and colon cancer cells. However, the inhibitory effect was obviously observed in colon cancer cells. Inhibition of arachidonic acid metabolism caused a decrease in cancer cell motility, which partially explained by the inhibition of MMPs. Therefore, COX and LOX pathways play important roles in head and neck cancer cell growth. PMID:20654727

  19. Oleic acid and linoleic acid from Tenebrio molitor larvae inhibit BACE1 activity in vitro: molecular docking studies.

    PubMed

    Youn, Kumju; Yun, Eun-Young; Lee, Jinhyuk; Kim, Ji-Young; Hwang, Jae-Sam; Jeong, Woo-Sik; Jun, Mira

    2014-02-01

    In our ongoing research to find therapeutic compounds for Alzheimer's disease (AD) from natural resources, the inhibitory activity of the BACE1 enzyme by Tenebrio molitor larvae and its major compounds were evaluated. The T. molitor larvae extract and its fractions exhibited strong BACE1 suppression. The major components of hexane fraction possessing both high yield and strong BACE1 inhibition were determined by thin layer chromatography, gas chromatography, and nuclear magnetic resonance analysis. A remarkable composition of unsaturated long chain fatty acids, including oleic acid and linoleic acid, were identified. Oleic acid, in particular, noncompetitively attenuated BACE1 activity with a half-maximal inhibitory concentration (IC₅₀) value of 61.31 μM and Ki value of 34.3 μM. Furthermore, the fatty acids were stably interacted with BACE1 at different allosteric sites of the enzyme bound with the OH of CYS319 and the NH₃ of TYR320 for oleic acid and with the C=O group of GLN304 for linoleic acid. Here, we first revealed novel pharmacophore features of oleic acids and linoleic acid to BACE1 by in silico docking studies. The present findings would clearly suggest potential guidelines for designing novel BACE1 selective inhibitors.

  20. Inhibition of Aeromonas caviae and A. sobria by sodium choloride, citric acid, ascorbic acid, potassium sorbate and extracts of Thymus vulgaris.

    PubMed

    Abu-Ghazaleh, B M

    2000-06-01

    The respective and combined effects of sodium chloride, ascorbic acid, citric acid, potassium sorbate, and Thymus vulgaris extract on the growth of Aeromonas caviae and Aeromonas sobria were investigated. Sodium chloride (3%) significantly reduced the growth and 4% NaCl inhibited growth of the tested strains. Ascorbic acid (0. 1%), potassium sorbate (0.05%), and citric acid (0.03%) slightly inhibited growth. T. vulgaris extract (0.3%) greatly reduced the growth. Various combinations of these compounds prevented growth of the tested strains. A combination of NaCl (3%) and ascorbic acid (0. 1%), citric acid (0.03%) and potassium sorbate (0.05%), or citric acid (0.03%) and ascorbic acid (0.1%) inhibited growth of A. caviae and A. sobria. In fish homogenates, the addition of ascorbic acid (0. 1%) and citric acid (0.03%) was the most effective combination tested.

  1. Benzbromarone, Quercetin, and Folic Acid Inhibit Amylin Aggregation.

    PubMed

    López, Laura C; Varea, Olga; Navarro, Susanna; Carrodeguas, José A; Sanchez de Groot, Natalia; Ventura, Salvador; Sancho, Javier

    2016-01-01

    Human Amylin, or islet amyloid polypeptide (hIAPP), is a small hormone secreted by pancreatic β-cells that forms aggregates under insulin deficiency metabolic conditions, and it constitutes a pathological hallmark of type II diabetes mellitus. In type II diabetes patients, amylin is abnormally increased, self-assembled into amyloid aggregates, and ultimately contributes to the apoptotic death of β-cells by mechanisms that are not completely understood. We have screened a library of approved drugs in order to identify inhibitors of amylin aggregation that could be used as tools to investigate the role of amylin aggregation in type II diabetes or as therapeutics in order to reduce β-cell damage. Interestingly, three of the compounds analyzed-benzbromarone, quercetin, and folic acid-are able to slow down amylin fiber formation according to Thioflavin T binding, turbidimetry, and Transmission Electron Microscopy assays. In addition to the in vitro assays, we have tested the effect of these compounds in an amyloid toxicity cell culture model and we have found that one of them, quercetin, has the ability to partly protect cultured pancreatic insulinoma cells from the cytotoxic effect of amylin. Our data suggests that quercetin can contribute to reduce oxidative damage in pancreatic insulinoma β cells by modulating the aggregation propensity of amylin. PMID:27322259

  2. Retinoic acid attenuates O2-induced inhibition of lung septation.

    PubMed

    Veness-Meehan, Kathleen A; Pierce, Richard A; Moats-Staats, Billie M; Stiles, Alan D

    2002-11-01

    Exposure of the newborn lung to hyperoxia is associated with impaired alveolar development. In newborn rats exposed to hyperoxia and studied at day 14 of life, retinoic acid (RA) treatment improved survival and increased lung collagen but did not improve alveolar development. To determine whether RA treatment during exposure to hyperoxia results in late improvement in alveolarization, we treated newborn rats with RA and hyperoxia from day 3 to day 14 and then weaned O2 to room air by day 20, and studied the animals on day 42. O2-exposed animals had larger mean lung volumes, larger alveoli, and decreased gas-exchange tissue relative to air-exposed animals, whereas RA-treated O2-exposed animals were not statistically different from air-exposed controls. Relative to control animals, elastin staining at day 14 was decreased in hyperoxia-exposed lung independent of RA treatment, and, at day 42, elastin staining was similar in all treatment groups. At day 14, elastin gene expression was similar in all treatment groups, whereas at day 42 lung previously exposed to hyperoxia showed increased elastin signal independent of RA treatment. These results indicate that RA treatment during hyperoxia exposure promotes septal formation without evidence of effects on elastin gene expression after 4 wk of recovery. PMID:12376350

  3. Identification of self-growth-inhibiting compounds lauric acid and 7-(Z)-tetradecenoic acid from Helicobacter pylori.

    PubMed

    Yamashita, Shinpei; Igarashi, Masayuki; Hayashi, Chigusa; Shitara, Tetsuo; Nomoto, Akio; Mizote, Tomoko; Shibasaki, Masakatsu

    2015-06-01

    Helicobacter pylori growth medium is usually supplemented with horse serum (HS) or FCS. However, cyclodextrin derivatives or activated charcoal can replace serum. In this study, we purified self-growth-inhibiting (SGI) compounds from H. pylori growth medium. The compounds were recovered from porous resin, Diaion HP-20, which was added to the H. pylori growth medium instead of known supplements. These SGI compounds were also identified from 2,6-di-O-methyl-β-cyclodextrin, which was supplemented in a pleuropneumonia-like organisms broth. The growth-inhibiting compounds were identified as lauric acid (LA) and 7-(Z)-tetradecenoic acid [7-(Z)-TDA]. Although several fatty acids had been identified in H. pylori, these specific compounds were not previously found in this species. However, we confirmed that these fatty acids were universally present in the cultivation medium of the H. pylori strains examined in this study. A live/dead assay carried out without HS indicated that these compounds were bacteriostatic; however, no significant growth-inhibiting effect was observed against other tested bacterial species that constituted the indigenous bacterial flora. These findings suggested that LA and 7-(Z)-TDA might play important roles in the survival of H. pylori in human stomach epithelial cells. PMID:25767109

  4. Calcite crystal growth inhibition by humic substances with emphasis on hydrophobic acids from the Florida Everglades

    USGS Publications Warehouse

    Hoch, A.R.; Reddy, M.M.; Aiken, G.R.

    2000-01-01

    The crystallization of calcium carbonate minerals plays an integral role in the water chemistry of terrestrial ecosystems. Humic substances, which are ubiquitous in natural waters, have been shown to reduce or inhibit calcite crystal growth in experiments. The purpose of this study is to quantify and understand the kinetic effects of hydrophobic organic acids isolated from the Florida Everglades and a fulvic acid from Lake Fryxell, Antarctica, on the crystal growth of calcite (CaCO3). Highly reproducible calcite growth experiments were performed in a sealed reactor at constant pH, temperature, supersaturation (?? = 4.5), P(CO2) (10-3.5atm), and ionic strength (0.1 M) with various concentrations of organic acids. Higher plant-derived aquatic hydrophobic acids from the Everglades were more effective growth inhibitors than microbially derived fulvic acid from Lake Fryxell. Organic acid aromaticity correlated strongly with growth inhibition. Molecular weight and heteroatom content correlated well with growth inhibition, whereas carboxyl content and aliphatic nature did not. Copyright (C) 1999 Elsevier Science Ltd.

  5. Calcium-dependent oligomerization of CAR proteins at cell membrane modulates ABA signaling

    PubMed Central

    Diaz, Maira; Sanchez-Barrena, Maria Jose; Gonzalez-Rubio, Juana Maria; Rodriguez, Lesia; Fernandez, Daniel; Antoni, Regina; Yunta, Cristina; Belda-Palazon, Borja; Gonzalez-Guzman, Miguel; Peirats-Llobet, Marta; Menendez, Margarita; Boskovic, Jasminka; Marquez, Jose A.; Rodriguez, Pedro L.; Albert, Armando

    2016-01-01

    Regulation of ion transport in plants is essential for cell function. Abiotic stress unbalances cell ion homeostasis, and plants tend to readjust it, regulating membrane transporters and channels. The plant hormone abscisic acid (ABA) and the second messenger Ca2+ are central in such processes, as they are involved in the regulation of protein kinases and phosphatases that control ion transport activity in response to environmental stimuli. The identification and characterization of the molecular mechanisms underlying the effect of ABA and Ca2+ signaling pathways on membrane function are central and could provide opportunities for crop improvement. The C2-domain ABA-related (CAR) family of small proteins is involved in the Ca2+-dependent recruitment of the pyrabactin resistance 1/PYR1-like (PYR/PYL) ABA receptors to the membrane. However, to fully understand CAR function, it is necessary to define a molecular mechanism that integrates Ca2+ sensing, membrane interaction, and the recognition of the PYR/PYL interacting partners. We present structural and biochemical data showing that CARs are peripheral membrane proteins that functionally cluster on the membrane and generate strong positive membrane curvature in a Ca2+-dependent manner. These features represent a mechanism for the generation, stabilization, and/or specific recognition of membrane discontinuities. Such structures may act as signaling platforms involved in the recruitment of PYR/PYL receptors and other signaling components involved in cell responses to stress. PMID:26719420

  6. ABA induces H2O2 production in guard cells, but does not close the stomata on Vicia faba leaves developed at high air humidity.

    PubMed

    Arve, Louise E; Carvalho, Dália R A; Olsen, Jorunn E; Torre, Sissel

    2014-01-01

    Plants developed under constant high (> 85%) relative air humidity (RH) have larger stomata that are unable to close completely. One of the hypotheses for the less responsive stomata is that the plants have reduced sensitivity to abscisic acid (ABA). Both ABA and darkness are signals for stomatal closure and induce the production of the secondary messenger hydrogen peroxide (H2O2). In this study, the ability of Vicia faba plants developed in moderate or high RH to close the stomata in response to darkness, ABA and H2O2 was investigated. Moreover, the ability of the plants to produce H2O2 when treated with ABA or transferred to darkness was also assessed. Our results show that the ABA concentration in moderate RH is not increased during darkness even though the stomata are closing. This indicates that stomatal closure in V. faba during darkness is independent of ABA production. ABA induced both H2O2 production and stomatal closure in stomata formed at moderate RH. H2O2 production, as a result of treatment with ABA, was also observed in stomata formed at high RH, though the closing response was considerably smaller as compared with moderate RH. In either RH, leaf ABA concentration was not affected by darkness. Similarly to ABA treatment, darkness elicited both H2O2 production and stomatal closure following plant cultivation at moderate RH. Contrary to this, neither H2O2 production nor stomatal closure took place when stomata were formed at high RH. These results suggest that the reduced stomatal response in plants developed in continuous high RH is caused by one or more factors downstream of H2O2 in the signaling pathway toward stomatal closure. PMID:25763494

  7. ABA induces H2O2 production in guard cells, but does not close the stomata on Vicia faba leaves developed at high air humidity.

    PubMed

    Arve, Louise E; Carvalho, Dália R A; Olsen, Jorunn E; Torre, Sissel

    2014-01-01

    Plants developed under constant high (> 85%) relative air humidity (RH) have larger stomata that are unable to close completely. One of the hypotheses for the less responsive stomata is that the plants have reduced sensitivity to abscisic acid (ABA). Both ABA and darkness are signals for stomatal closure and induce the production of the secondary messenger hydrogen peroxide (H2O2). In this study, the ability of Vicia faba plants developed in moderate or high RH to close the stomata in response to darkness, ABA and H2O2 was investigated. Moreover, the ability of the plants to produce H2O2 when treated with ABA or transferred to darkness was also assessed. Our results show that the ABA concentration in moderate RH is not increased during darkness even though the stomata are closing. This indicates that stomatal closure in V. faba during darkness is independent of ABA production. ABA induced both H2O2 production and stomatal closure in stomata formed at moderate RH. H2O2 production, as a result of treatment with ABA, was also observed in stomata formed at high RH, though the closing response was considerably smaller as compared with moderate RH. In either RH, leaf ABA concentration was not affected by darkness. Similarly to ABA treatment, darkness elicited both H2O2 production and stomatal closure following plant cultivation at moderate RH. Contrary to this, neither H2O2 production nor stomatal closure took place when stomata were formed at high RH. These results suggest that the reduced stomatal response in plants developed in continuous high RH is caused by one or more factors downstream of H2O2 in the signaling pathway toward stomatal closure.

  8. ABA induces H2O2 production in guard cells, but does not close the stomata on Vicia faba leaves developed at high air humidity

    PubMed Central

    Arve, Louise E; Carvalho, Dália RA; Olsen, Jorunn E; Torre, Sissel

    2014-01-01

    Plants developed under constant high (> 85%) relative air humidity (RH) have larger stomata that are unable to close completely. One of the hypotheses for the less responsive stomata is that the plants have reduced sensitivity to abscisic acid (ABA). Both ABA and darkness are signals for stomatal closure and induce the production of the secondary messenger hydrogen peroxide (H2O2). In this study, the ability of Vicia faba plants developed in moderate or high RH to close the stomata in response to darkness, ABA and H2O2 was investigated. Moreover, the ability of the plants to produce H2O2 when treated with ABA or transferred to darkness was also assessed. Our results show that the ABA concentration in moderate RH is not increased during darkness even though the stomata are closing. This indicates that stomatal closure in V. faba during darkness is independent of ABA production. ABA induced both H2O2 production and stomatal closure in stomata formed at moderate RH. H2O2 production, as a result of treatment with ABA, was also observed in stomata formed at high RH, though the closing response was considerably smaller as compared with moderate RH. In either RH, leaf ABA concentration was not affected by darkness. Similarly to ABA treatment, darkness elicited both H2O2 production and stomatal closure following plant cultivation at moderate RH. Contrary to this, neither H2O2 production nor stomatal closure took place when stomata were formed at high RH. These results suggest that the reduced stomatal response in plants developed in continuous high RH is caused by one or more factors downstream of H2O2 in the signaling pathway toward stomatal closure. PMID:25763494

  9. The Zinc Finger Transcription Factor SlZFP2 Negatively Regulates Abscisic Acid Biosynthesis and Fruit Ripening in Tomato1

    PubMed Central

    Weng, Lin; Zhao, Fangfang; Li, Rong; Xu, Changjie; Chen, Kunsong

    2015-01-01

    Abscisic acid (ABA) regulates plant development and adaptation to environmental conditions. Although the ABA biosynthesis pathway in plants has been thoroughly elucidated, how ABA biosynthetic genes are regulated at the molecular level during plant development is less well understood. Here, we show that the tomato (Solanum lycopersicum) zinc finger transcription factor SlZFP2 is involved in the regulation of ABA biosynthesis during fruit development. Overexpression of SlZFP2 resulted in multiple phenotypic changes, including more branches, early flowering, delayed fruit ripening, lighter seeds, and faster seed germination, whereas down-regulation of its expression caused problematic fruit set, accelerated ripening, and inhibited seed germination. SlZFP2 represses ABA biosynthesis during fruit development through direct suppression of the ABA biosynthetic genes NOTABILIS, SITIENS, and FLACCA and the aldehyde oxidase SlAO1. We also show that SlZFP2 regulates fruit ripening through transcriptional suppression of the ripening regulator COLORLESS NON-RIPENING. Using bacterial one-hybrid screening and a selected amplification and binding assay, we identified the (A/T)(G/C)TT motif as the core binding sequence of SlZFP2. Furthermore, by RNA sequencing profiling, we found that 193 genes containing the SlZFP2-binding motifs in their promoters were differentially expressed in 2 d post anthesis fruits between the SlZFP2 RNA interference line and its nontransgenic sibling. We propose that SlZFP2 functions as a repressor to fine-tune ABA biosynthesis during fruit development and provides a potentially valuable tool for dissecting the role of ABA in fruit ripening. PMID:25637453

  10. The zinc finger transcription factor SlZFP2 negatively regulates abscisic acid biosynthesis and fruit ripening in tomato.

    PubMed

    Weng, Lin; Zhao, Fangfang; Li, Rong; Xu, Changjie; Chen, Kunsong; Xiao, Han

    2015-03-01

    Abscisic acid (ABA) regulates plant development and adaptation to environmental conditions. Although the ABA biosynthesis pathway in plants has been thoroughly elucidated, how ABA biosynthetic genes are regulated at the molecular level during plant development is less well understood. Here, we show that the tomato (Solanum lycopersicum) zinc finger transcription factor SlZFP2 is involved in the regulation of ABA biosynthesis during fruit development. Overexpression of SlZFP2 resulted in multiple phenotypic changes, including more branches, early flowering, delayed fruit ripening, lighter seeds, and faster seed germination, whereas down-regulation of its expression caused problematic fruit set, accelerated ripening, and inhibited seed germination. SlZFP2 represses ABA biosynthesis during fruit development through direct suppression of the ABA biosynthetic genes NOTABILIS, SITIENS, and FLACCA and the aldehyde oxidase SlAO1. We also show that SlZFP2 regulates fruit ripening through transcriptional suppression of the ripening regulator COLORLESS NON-RIPENING. Using bacterial one-hybrid screening and a selected amplification and binding assay, we identified the (A/T)(G/C)TT motif as the core binding sequence of SlZFP2. Furthermore, by RNA sequencing profiling, we found that 193 genes containing the SlZFP2-binding motifs in their promoters were differentially expressed in 2 d post anthesis fruits between the SlZFP2 RNA interference line and its nontransgenic sibling. We propose that SlZFP2 functions as a repressor to fine-tune ABA biosynthesis during fruit development and provides a potentially valuable tool for dissecting the role of ABA in fruit ripening.

  11. Kaurenoic Acid from Aralia continentalis Inhibits Biofilm Formation of Streptococcus mutans

    PubMed Central

    Jeong, Seung-Il; Kim, Beom-Su; Keum, Ki-Suk; Lee, Kwang-Hee; Kang, Sun-Young; Park, Bok-Im; Lee, Young-Rae; You, Yong-Ouk

    2013-01-01

    We isolated a single chemical compound from A. continentalis and identified it to be kaurenoic acid (KA) and investigated the influence of anticariogenic properties. Inhibitory effects of KA on cariogenic properties such as growth, acid production, biofilm formation, and the adherence of S. mutans were evaluated. Furthermore, real-time PCR analysis was performed to evaluate the influence of KA on the genetic expression of virulence factors. KA significantly inhibited the growth and acid production of S. mutans at 2–4 μg/mL and 4 μg/mL of KA, respectively. Furthermore, the adherence onto S-HAs was inhibited at 3-4 μg/mL of KA and biofilm formation was significantly inhibited when treated with 3 μg/mL KA and completely inhibited at 4 μg/mL. Also, the inhibitory effect of KA on biofilm formation was confirmed by SEM. In confocal laser scanning microscopy, bacterial viability gradually decreased by KA in a dose dependent manner. Real-time PCR analysis showed that the expressions of gtfB, gtfC, gbpB, spaP, brpA, relA, and vicR were significantly decreased in S. mutans when it was treated with KA. These results suggest that KA from A. continentalis may be a useful agent for inhibiting the cariogenic properties of S. mutans. PMID:23662113

  12. The Molecular Basis for Dual Fatty Acid Amide Hydrolase (FAAH)/Cyclooxygenase (COX) Inhibition

    PubMed Central

    Palermo, Giulia; Favia, Angelo D.; Convertino, Marino

    2015-01-01

    Abstract The design of multitarget‐directed ligands is a promising strategy for discovering innovative drugs. Here, we report a mechanistic study that clarifies key aspects of the dual inhibition of the fatty acid amide hydrolase (FAAH) and the cyclooxygenase (COX) enzymes by a new multitarget‐directed ligand named ARN2508 (2‐[3‐fluoro‐4‐[3‐(hexylcarbamoyloxy)phenyl]phenyl]propanoic acid). This potent dual inhibitor combines, in a single scaffold, the pharmacophoric elements often needed to block FAAH and COX, that is, a carbamate moiety and the 2‐arylpropionic acid functionality, respectively. Molecular modeling and molecular dynamics simulations suggest that ARN2508 uses a noncovalent mechanism of inhibition to block COXs, while inhibiting FAAH via the acetylation of the catalytic Ser241, in line with previous experimental evidence for covalent FAAH inhibition. This study proposes the molecular basis for the dual FAAH/COX inhibition by this novel hybrid scaffold, stimulating further experimental studies and offering new insights for the rational design of novel anti‐inflammatory agents that simultaneously act on FAAH and COX. PMID:26593700

  13. Photodegradation and inhibition of drug-resistant influenza virus neuraminidase using anthraquinone-sialic acid hybrids.

    PubMed

    Aoki, Yusuke; Tanimoto, Shuho; Takahashi, Daisuke; Toshima, Kazunobu

    2013-02-11

    The anthraquinone-sialic acid hybrids designed effectively degraded not only non-drug-resistant neuraminidase but also drug-resistant neuraminidase, which is an important target of anti-influenza therapy. Degradation was achieved using long-wavelength UV radiation in the absence of any additives and under neutral conditions. Moreover, the hybrids efficiently inhibited neuraminidase activities upon photo-irradiation. PMID:23282898

  14. Selective inhibition of fatty acid oxidation in colonocytes by ibuprofen: a cause of colitis?

    PubMed Central

    Roediger, W E; Millard, S

    1995-01-01

    Ibuprofen is associated with initiation or exacerbation of ulcerative colitis. As ibuprofen selectively inhibited fatty acid oxidation in the liver or caused mitochondrial damage in intestinal cells, its effect on substrate oxidation by isolated colonocytes of man and rat was examined. Ibuprofen dose dependently (2.0-7.5 mmol/l) and selectively inhibited 14CO2 production from labelled n-butyrate in colonocytes from the proximal and distal human colon (n = 12, p = < 0.001). Glucose oxidation was either unaltered or increased. Because short chain fatty acid oxidation is the main source of acetyl-CoA for long chain fatty acid synthesis, the inhibition of prostaglandin synthesis by ibuprofen in the colonic mucosa could also occur at this level. Because the concentrations of ibuprofen that can be attained in the human colon are not known, conclusions drawn from current dosages are tentative. The inhibition of fatty acid oxidation by ibuprofen may be biochemically implicated in the initiation and exacerbation of ulcerative colitis, manifestation of which would depend on the ibuprofen concentrations reached in the colon. PMID:7890237

  15. A 14-3-3 Family Protein from Wild Soybean (Glycine Soja) Regulates ABA Sensitivity in Arabidopsis

    PubMed Central

    Sun, Xiaoli; Sun, Mingzhe; Jia, Bowei; Chen, Chao; Qin, Zhiwei; Yang, Kejun; Shen, Yang; Meiping, Zhang; Mingyang, Cong; Zhu, Yanming

    2015-01-01

    It is widely accepted that the 14-3-3 family proteins are key regulators of multiple stress signal transduction cascades. By conducting genome-wide analysis, researchers have identified the soybean 14-3-3 family proteins; however, until now, there is still no direct genetic evidence showing the involvement of soybean 14-3-3s in ABA responses. Hence, in this study, based on the latest Glycine max genome on Phytozome v10.3, we initially analyzed the evolutionary relationship, genome organization, gene structure and duplication, and three-dimensional structure of soybean 14-3-3 family proteins systematically. Our results suggested that soybean 14-3-3 family was highly evolutionary conserved and possessed segmental duplication in evolution. Then, based on our previous functional characterization of a Glycine soja 14-3-3 protein GsGF14o in drought stress responses, we further investigated the expression characteristics of GsGF14o in detail, and demonstrated its positive roles in ABA sensitivity. Quantitative real-time PCR analyses in Glycine soja seedlings and GUS activity assays in PGsGF14O:GUS transgenic Arabidopsis showed that GsGF14o expression was moderately and rapidly induced by ABA treatment. As expected, GsGF14o overexpression in Arabidopsis augmented the ABA inhibition of seed germination and seedling growth, promoted the ABA induced stomata closure, and up-regulated the expression levels of ABA induced genes. Moreover, through yeast two hybrid analyses, we further demonstrated that GsGF14o physically interacted with the AREB/ABF transcription factors in yeast cells. Taken together, results presented in this study strongly suggested that GsGF14o played an important role in regulation of ABA sensitivity in Arabidopsis. PMID:26717241

  16. A 14-3-3 Family Protein from Wild Soybean (Glycine Soja) Regulates ABA Sensitivity in Arabidopsis.

    PubMed

    Sun, Xiaoli; Sun, Mingzhe; Jia, Bowei; Chen, Chao; Qin, Zhiwei; Yang, Kejun; Shen, Yang; Meiping, Zhang; Mingyang, Cong; Zhu, Yanming

    2015-01-01

    It is widely accepted that the 14-3-3 family proteins are key regulators of multiple stress signal transduction cascades. By conducting genome-wide analysis, researchers have identified the soybean 14-3-3 family proteins; however, until now, there is still no direct genetic evidence showing the involvement of soybean 14-3-3s in ABA responses. Hence, in this study, based on the latest Glycine max genome on Phytozome v10.3, we initially analyzed the evolutionary relationship, genome organization, gene structure and duplication, and three-dimensional structure of soybean 14-3-3 family proteins systematically. Our results suggested that soybean 14-3-3 family was highly evolutionary conserved and possessed segmental duplication in evolution. Then, based on our previous functional characterization of a Glycine soja 14-3-3 protein GsGF14o in drought stress responses, we further investigated the expression characteristics of GsGF14o in detail, and demonstrated its positive roles in ABA sensitivity. Quantitative real-time PCR analyses in Glycine soja seedlings and GUS activity assays in PGsGF14O:GUS transgenic Arabidopsis showed that GsGF14o expression was moderately and rapidly induced by ABA treatment. As expected, GsGF14o overexpression in Arabidopsis augmented the ABA inhibition of seed germination and seedling growth, promoted the ABA induced stomata closure, and up-regulated the expression levels of ABA induced genes. Moreover, through yeast two hybrid analyses, we further demonstrated that GsGF14o physically interacted with the AREB/ABF transcription factors in yeast cells. Taken together, results presented in this study strongly suggested that GsGF14o played an important role in regulation of ABA sensitivity in Arabidopsis. PMID:26717241

  17. A 14-3-3 Family Protein from Wild Soybean (Glycine Soja) Regulates ABA Sensitivity in Arabidopsis.

    PubMed

    Sun, Xiaoli; Sun, Mingzhe; Jia, Bowei; Chen, Chao; Qin, Zhiwei; Yang, Kejun; Shen, Yang; Meiping, Zhang; Mingyang, Cong; Zhu, Yanming

    2015-01-01

    It is widely accepted that the 14-3-3 family proteins are key regulators of multiple stress signal transduction cascades. By conducting genome-wide analysis, researchers have identified the soybean 14-3-3 family proteins; however, until now, there is still no direct genetic evidence showing the involvement of soybean 14-3-3s in ABA responses. Hence, in this study, based on the latest Glycine max genome on Phytozome v10.3, we initially analyzed the evolutionary relationship, genome organization, gene structure and duplication, and three-dimensional structure of soybean 14-3-3 family proteins systematically. Our results suggested that soybean 14-3-3 family was highly evolutionary conserved and possessed segmental duplication in evolution. Then, based on our previous functional characterization of a Glycine soja 14-3-3 protein GsGF14o in drought stress responses, we further investigated the expression characteristics of GsGF14o in detail, and demonstrated its positive roles in ABA sensitivity. Quantitative real-time PCR analyses in Glycine soja seedlings and GUS activity assays in PGsGF14O:GUS transgenic Arabidopsis showed that GsGF14o expression was moderately and rapidly induced by ABA treatment. As expected, GsGF14o overexpression in Arabidopsis augmented the ABA inhibition of seed germination and seedling growth, promoted the ABA induced stomata closure, and up-regulated the expression levels of ABA induced genes. Moreover, through yeast two hybrid analyses, we further demonstrated that GsGF14o physically interacted with the AREB/ABF transcription factors in yeast cells. Taken together, results presented in this study strongly suggested that GsGF14o played an important role in regulation of ABA sensitivity in Arabidopsis.

  18. Fatty acid synthesis is inhibited by inefficient utilization of unusual fatty acids for glycerolipid assembly.

    PubMed

    Bates, Philip D; Johnson, Sean R; Cao, Xia; Li, Jia; Nam, Jeong-Won; Jaworski, Jan G; Ohlrogge, John B; Browse, John

    2014-01-21

    Degradation of unusual fatty acids through β-oxidation within transgenic plants has long been hypothesized as a major factor limiting the production of industrially useful unusual fatty acids in seed oils. Arabidopsis seeds expressing the castor fatty acid hydroxylase accumulate hydroxylated fatty acids up to 17% of total fatty acids in seed triacylglycerols; however, total seed oil is also reduced up to 50%. Investigations into the cause of the reduced oil phenotype through in vivo [(14)C]acetate and [(3)H]2O metabolic labeling of developing seeds surprisingly revealed that the rate of de novo fatty acid synthesis within the transgenic seeds was approximately half that of control seeds. RNAseq analysis indicated no changes in expression of fatty acid synthesis genes in hydroxylase-expressing plants. However, differential [(14)C]acetate and [(14)C]malonate metabolic labeling of hydroxylase-expressing seeds indicated the in vivo acetyl-CoA carboxylase activity was reduced to approximately half that of control seeds. Therefore, the reduction of oil content in the transgenic seeds is consistent with reduced de novo fatty acid synthesis in the plastid rather than fatty acid degradation. Intriguingly, the coexpression of triacylglycerol synthesis isozymes from castor along with the fatty acid hydroxylase alleviated the reduced acetyl-CoA carboxylase activity, restored the rate of fatty acid synthesis, and the accumulation of seed oil was substantially recovered. Together these results suggest a previously unidentified mechanism that detects inefficient utilization of unusual fatty acids within the endoplasmic reticulum and activates an endogenous pathway for posttranslational reduction of fatty acid synthesis within the plastid.

  19. d-Amino Acids Do Not Inhibit Biofilm Formation in Staphylococcus aureus

    PubMed Central

    Sarkar, Sourav; Pires, Marcos M.

    2015-01-01

    Bacteria can either exist in the planktonic (free floating) state or in the biofilm (encased within an organic framework) state. Bacteria biofilms cause industrial concerns and medical complications and there has been a great deal of interest in the discovery of small molecule agents that can inhibit the formation of biofilms or disperse existing structures. Herein we show that, contrary to previously published reports, d-amino acids do not inhibit biofilm formation of Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus), and Staphylococcus epidermis (S. epidermis) at millimolar concentrations. We evaluated a diverse set of natural and unnatural d-amino acids and observed no activity from these compounds in inhibiting biofilm formation. PMID:25658642

  20. d-Amino acids do not inhibit biofilm formation in Staphylococcus aureus.

    PubMed

    Sarkar, Sourav; Pires, Marcos M

    2015-01-01

    Bacteria can either exist in the planktonic (free floating) state or in the biofilm (encased within an organic framework) state. Bacteria biofilms cause industrial concerns and medical complications and there has been a great deal of interest in the discovery of small molecule agents that can inhibit the formation of biofilms or disperse existing structures. Herein we show that, contrary to previously published reports, d-amino acids do not inhibit biofilm formation of Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus), and Staphylococcus epidermis (S. epidermis) at millimolar concentrations. We evaluated a diverse set of natural and unnatural d-amino acids and observed no activity from these compounds in inhibiting biofilm formation. PMID:25658642

  1. Retinoic acid receptor alpha mediates growth inhibition by retinoids in human colon carcinoma HT29 cells.

    PubMed

    Nicke, B; Kaiser, A; Wiedenmann, B; Riecken, E O; Rosewicz, S

    1999-08-11

    Although retinoids have been suggested to inhibit chemically induced colon carcinogenesis, the molecular mechanisms underlying retinoid-mediated growth regulation in colon carcinoma cells are unknown. Therefore, we investigated the biological effects of retinoids on growth in HT29 colon carcinoma cells. All-trans retinoic acid (ATRA) treatment of HT29 cells resulted in a profound inhibition of anchorage-independent growth without biochemical or morphological evidence for induction of differentiation. Treatment with the selective RARalpha agonist Ro 40-6055 completely mimicked the effects of ATRA on growth and transactivation of a betaRAREx2-luciferase reporter construct, while RARbeta- and gamma-specific analogues were ineffective. Furthermore, ATRA-regulated growth and transactivation could be completely blocked by a RARalpha-selective receptor antagonist. Thus, ATRA potently inhibits anchorage-independent growth in HT29 cells and this effect is mainly if not exclusively mediated by the retinoic acid receptor alpha.

  2. Zoledronic acid inhibits pulmonary metastasis dissemination in a preclinical model of Ewing’s sarcoma via inhibition of cell migration

    PubMed Central

    2014-01-01

    Background Ewing’s sarcoma (ES) is the second most frequent primitive malignant bone tumor in adolescents with a very poor prognosis for high risk patients, mainly when lung metastases are detected (overall survival <15% at 5 years). Zoledronic acid (ZA) is a potent inhibitor of bone resorption which induces osteoclast apoptosis. Our previous studies showed a strong therapeutic potential of ZA as it inhibits ES cell growth in vitro and ES primary tumor growth in vivo in a mouse model developed in bone site. However, no data are available on lung metastasis. Therefore, the aim of this study was to determine the effect of ZA on ES cell invasion and metastatic properties. Methods Invasion assays were performed in vitro in Boyden’s chambers covered with Matrigel. Matrix Metalloproteinase (MMP) activity was analyzed by zymography in ES cell culture supernatant. In vivo, a relevant model of spontaneous lung metastases which disseminate from primary ES tumor was induced by the orthotopic injection of 106 human ES cells in the tibia medullar cavity of nude mice. The effect of ZA (50 μg/kg, 3x/week) was studied over a 4-week period. Lung metastases were observed macroscopically at autopsy and analysed by histology. Results ZA induced a strong inhibition of ES cell invasion, probably due to down regulation of MMP-2 and −9 activities as analyzed by zymography. In vivo, ZA inhibits the dissemination of spontaneous lung metastases from a primary ES tumor but had no effect on the growth of established lung metastases. Conclusion These results suggest that ZA could be used early in the treatment of ES to inhibit bone tumor growth but also to prevent the early metastatic events to the lungs. PMID:24612486

  3. Sialic Acid Is Required for Neuronal Inhibition by Soluble MAG but not for Membrane Bound MAG

    PubMed Central

    Al-Bashir, Najat; Mellado, Wilfredo; Filbin, Marie T.

    2016-01-01

    Myelin-Associated Glycoprotein (MAG), a major inhibitor of axonal growth, is a member of the immunoglobulin (Ig) super-family. Importantly, MAG (also known as Siglec-4) is a member of the Siglec family of proteins (sialic acid-binding, immunoglobulin-like lectins), MAG binds to complex gangliosides, specifically GD1a and/or GT1b. Therefore, it has been proposed as neuronal receptors for MAG inhibitory effect of axonal growth. Previously, we showed that MAG binds sialic acid through domain 1 at Arg118 and is able to inhibit axonal growth through domain 5. We developed a neurite outgrowth (NOG) assay, in which both wild type MAG and mutated MAG (MAG Arg118) are expressed on cells. In addition we also developed a soluble form NOG in which we utilized soluble MAG-Fc and mutated MAG (Arg118-Fc). Only MAG-Fc is able to inhibit NOG, but not mutated MAG (Arg118)-Fc that has been mutated at its sialic acid binding site. However, both forms of membrane bound MAG- and MAG (Arg118)- expressing cells still inhibit NOG. Here, we review various results from different groups regarding MAG’s inhibition of axonal growth. Also, we propose a model in which the sialic acid binding is not necessary for the inhibition induced by the membrane form of MAG, but it is necessary for the soluble form of MAG. This finding highlights the importance of understanding the different mechanisms by which MAG inhibits NOG in both the soluble fragmented form and the membrane-bound form in myelin debris following CNS damage. PMID:27065798

  4. Inhibition of lysophospholipase D activity by unsaturated lysophosphatidic acids or seed extracts containing 1-linoleoyl and 1-oleoyl lysophosphatidic acid.

    PubMed

    Liu, Xi-Wen; Sok, Dai-Eun; Yook, Hong-Sun; Sohn, Cheon-Bae; Chung, Young-Jin; Kim, Mee Ree

    2007-10-17

    Lysophospholipase D (lysoPLD), generating lipid mediator lysophosphatidic acid (LPA) from lysophosphatidyclcholine (LPC), is known to be inhibited by lysophosphatidic acids. Meanwhile, some plant lipids are known to contain lysophospholipids as minor components. Therefore, it is interesting to test whether edible seed samples, rich in phospholipids, may contain lysophospholipids, which express a strong inhibition of lysoPLD activity. First, the structural importance of fatty acyl group in LPAs was examined by determining the inhibitory effect of various LPAs on bovine lysoPLD activity. The most potent in the inhibition of lysoPLD activity was linoleoyl-LPA ( K i, 0.21 microM), followed by arachidonoyl-LPA ( K i, 0.55 microM), oleoyl-LPA ( K i, 1.2 microM), and palmitoyl-LPA ( K i, 1.4 microM), based on the fluoresecent assay. The same order of inhibitory potency among LPA analogs with different acyl chains was also found in the spectrophotometric assay. Subsequently, the extracts of 12 edible seeds were screened for the inhibition of lysoPLD activity using both spectrophotometric and fluorescent assays. Among seed extracts tested, the extract from soybean seed, sesame seed, or sunflower seed (30 mg seed weight/mL) was found to exhibit a potent inhibition (>80%) of lysoPLD activity. In further study employing ESI-MS/MS analysis, major LPA components in seed extracts were identified to be 1-linoleoyl LPA, 1-oleoyl LPA, and 1-palmitoyl LPA with 1-linoleoyl LPA being more predominant. Thus, the potent inhibition of lysoPLD activity by seed extracts might be ascribed to the presence of LPA with linoleoyl group rather than other acyl chains. PMID:17887800

  5. Electrophilic Fatty Acid Species Inhibit 5-Lipoxygenase and Attenuate Sepsis-Induced Pulmonary Inflammation

    PubMed Central

    Awwad, Khader; Steinbrink, Svenja D.; Frömel, Timo; Lill, Nicole; Isaak, Johann; Häfner, Ann-Kathrin; Roos, Jessica; Hofmann, Bettina; Heide, Heinrich; Geisslinger, Gerd; Steinhilber, Dieter; Freeman, Bruce A.; Maier, Thorsten J.; Fleming, Ingrid

    2014-01-01

    Abstract Aims: The reaction of nitric oxide and nitrite-derived species with polyunsaturated fatty acids yields electrophilic fatty acid nitroalkene derivatives (NO2-FA), which display anti-inflammatory properties. Given that the 5-lipoxygenase (5-LO, ALOX5) possesses critical nucleophilic amino acids, which are potentially sensitive to electrophilic modifications, we determined the consequences of NO2-FA on 5-LO activity in vitro and on 5-LO-mediated inflammation in vivo. Results: Stimulation of human polymorphonuclear leukocytes (PMNL) with nitro-oleic (NO2-OA) or nitro-linoleic acid (NO2-LA) (but not the parent lipids) resulted in the concentration-dependent and irreversible inhibition of 5-LO activity. Similar effects were observed in cell lysates and using the recombinant human protein, indicating a direct reaction with 5-LO. NO2-FAs did not affect the activity of the platelet-type 12-LO (ALOX12) or 15-LO-1 (ALOX15) in intact cells or the recombinant protein. The NO2-FA-induced inhibition of 5-LO was attributed to the alkylation of Cys418, and the exchange of Cys418 to serine rendered 5-LO insensitive to NO2-FA. In vivo, the systemic administration of NO2-OA to mice decreased neutrophil and monocyte mobilization in response to lipopolysaccharide (LPS), attenuated the formation of the 5-LO product 5-hydroxyeicosatetraenoic acid (5-HETE), and inhibited lung injury. The administration of NO2-OA to 5-LO knockout mice had no effect on LPS-induced neutrophil or monocyte mobilization as well as on lung injury. Innovation: Prophylactic administration of NO2-OA to septic mice inhibits inflammation and promotes its resolution by interfering in 5-LO-mediated inflammatory processes. Conclusion: NO2-FAs directly and irreversibly inhibit 5-LO and attenuate downstream acute inflammatory responses. Antioxid. Redox Signal. 20, 2667–2680. PMID:24206143

  6. Corrosion Inhibition of Carbon Steel by New Thiophene Azo Dye Derivatives in Acidic Solution

    NASA Astrophysics Data System (ADS)

    El-Haddad, Mahmoud N.; Fouda, A. S.; Mostafa, H. A.

    2013-08-01

    Inhibition of carbon steel corrosion in 2 M hydrochloric acid (HCl) solution by thiophene azo dye derivatives were studied using weight loss, electrochemical frequency modulation (EFM), and atomic absorption techniques. The experimental data suggest that the inhibition efficiency increases with increasing inhibitors concentration in presence of 103 μM potassium iodide (KI). This is due to synergistic effect. Thus, the experimental results suggested that the presence of these anions in the solution stabilized the adsorption of inhibitors molecules on the metal surface and improved the inhibition efficiency. The results of EFM experiments are a spectrum of current response as a function of frequency. The corrosion rate and Tafel parameters can be obtained with measurement by analyzing the harmonic frequencies. The adsorption of the inhibitors on metal surface obeys the Langmuir adsorption isotherm. The surface of metal examined using Fourier transform infrared and ultraviolet spectroscopy. Quantum chemical calculations were carried out and relations between computed parameters and experimental inhibition efficiency were discussed.

  7. A balanced JA/ABA status may correlate with adaptation to osmotic stress in Vitis cells.

    PubMed

    Ismail, Ahmed; Seo, Mitsunori; Takebayashi, Yumiko; Kamiya, Yuji; Nick, Peter

    2015-08-01

    Water-related stress is considered a major type of plant stress. Osmotic stress, in particular, represents the common part of all water-related stresses. Therefore, plants have evolved different adaptive mechanisms to cope with osmotic-related disturbances. In the current work, two grapevine cell lines that differ in their osmotic adaptability, Vitis rupestris and Vitis riparia, were investigated under mannitol-induced osmotic stress. To dissect signals that lead to adaptability from those related to sensitivity, osmotic-triggered responses with respect to jasmonic acid (JA) and its active form JA-Ile, abscisic acid (ABA), and stilbene compounds, as well as the expression of their related genes were observed. In addition, the transcript levels of the cellular homeostasis gene NHX1 were examined. The data are discussed with a hypothesis suggesting that a balance of JA and ABA status might correlate with cellular responses, either guiding cells to sensitivity or to progress toward adaptation. PMID:26277753

  8. Inhibition of acid sensing ion channel by ligustrazine on angina model in rat.

    PubMed

    Zhang, Zhi-Gang; Zhang, Xiao-Lan; Wang, Xian-Yue; Luo, Zhu-Rong; Song, Jing-Chun

    2015-01-01

    Ligustrazine, a compound extracted from roots of Ligusticum chuanxiong, is widely used in Chinese traditional medicine to treat cardiac and cerebrovascular diseases and pain, including angina. The mechanism(s) of ligustrazine's effect to reduce angina is not clear. Angina is mediated by cardiac afferent sensory neurons. These neurons display a large acid-evoked depolarizing sodium current that can initiate action potentials in response to acidification that accompanies myocardial ischemia. Acid-sensing ion channels (ASICs) mediate this current. Here we tested the hypothesis that ligustrazine reduces ischemia-induced cardiac dysfunction and acid-evoked pain by an action to inhibit ASIC-mediated current. The effects of ligustrazine to attenuate ischemia-induced ST-segment depression, T wave changes, and myocardial infarct size in hearts of anesthetized rats were determined. Effects of ligustrazine on currents mediated by ASICs expressed in cultured Chinese hamster ovary cells, and effects of the drug on acid-induced nociceptive behavior and acid-induced currents in isolated dorsal root ganglions cells were measured. Ligustrazine significantly attenuated acid-induced ASIC currents, reduced cardiac ischemia-induced electrical dysfunction and infarct size, and decreased the nociceptive response to injection of acid into the paw of the rat hindlimb. The ASIC channel inhibitor A-317567 similarly reduced electrical dysfunction, infarct size, and nociceptive behavior in the rat. Inhibition of ASICs by ligustrazine may explain at least in part the beneficial effects of the drug that are observed in patients with ischemic heart disease and angina. PMID:26692925

  9. Neuraminidase inhibition of Dietary chlorogenic acids and derivatives - potential antivirals from dietary sources.

    PubMed

    Gamaleldin Elsadig Karar, Mohamed; Matei, Marius-Febi; Jaiswal, Rakesh; Illenberger, Susanne; Kuhnert, Nikolai

    2016-04-01

    Plants rich in chlorogenic acids (CGAs), caffeic acids and their derivatives have been found to exert antiviral effects against influenza virus neuroaminidase. In this study several dietary naturally occurring chlorogenic acids, phenolic acids and derivatives were screened for their inhibitory activity against neuroaminidases (NAs) from C. perfringens, H5N1 and recombinant H5N1 (N-His)-Tag using a fluorometric assay. There was no significant difference in inhibition between the different NA enzymes. The enzyme inhibition results indicated that chlorogenic acids and selected derivatives, exhibited high activities against NAs. It seems that the catechol group from caffeic acid was important for the activity. Dietary CGA therefore show promise as potential antiviral agents. However, caffeoyl quinic acids show low bioavailibility and are intensly metabolized by the gut micro flora, only low nM concentrations are observed in plasma and urine, therefore a systemic antiviral effect of these compounds is unlikely. Nevertheless, gut floral metabolites with a catechol moiety or structurally related dietary phenolics with a catechol moiety might serve as interesting compounds for future investigations. PMID:27010419

  10. Comparison of inhibition effects of some benzoic acid derivatives on sheep heart carbonic anhydrase

    NASA Astrophysics Data System (ADS)

    Kiliç, Deryanur; Yildiz, Melike; Şentürk, Murat; Erdoǧan, Orhan; Küfrevioǧlu, Ömer Irfan

    2016-04-01

    Carbonic anhydrase (CA) is a family of metalloenzymes that requires Zn as a cofactor and catalyze the quick conversion of CO2 to HCO3- and H+. Inhibitors of the carbonic anhydrases (CAs) have medical usage of significant diseases such as glaucoma, epilepsy, gastroduodenal ulcers, acid-base disequilibria and neurological disorders. In the present study, inhibition of CA with some benzoic derivatives (1-6) were investigated. Sheep heart CA (shCA) enzyme was isolated by means of designed affinity chromatography gel (cellulose-benzyl-sulfanylamide) 42.45-fold in a yield of 44 % with 564.65 EU/mg. Purified shCA enzyme was used in vitro studies. In the studies, IC50 values were calculated for 3-aminobenzoic acid (1), 4-aminobenzoic acid (2), 2-hydroxybenzoic acid (3), 2-benzoylbenzoic acid (4), 2,3-dimethoxybenzoic acid (5), and 3,4,5-trimethoxybenzoic acid (6), showing the inhibition effects on the purified enzyme. Such molecules can be used as pioneer for discovery of novel effective CA inhibitors for medicinal chemistry applications.

  11. The Arabidopsis abscisic acid response locus ABI4 encodes an APETALA 2 domain protein.

    PubMed Central

    Finkelstein, R R; Wang, M L; Lynch, T J; Rao, S; Goodman, H M

    1998-01-01

    Arabidopsis abscisic acid (ABA)-insensitive abi4 mutants have pleiotropic defects in seed development, including decreased sensitivity to ABA inhibition of germination and altered seed-specific gene expression. This phenotype is consistent with a role for ABI4 in regulating seed responses to ABA and/or seed-specific signals. We isolated the ABI4 gene by positional cloning and confirmed its identity by complementation analysis. The predicted protein product shows homology to a plant-specific family of transcriptional regulators characterized by a conserved DNA binding domain, the APETALA 2 domain. The single mutant allele identified has a single base pair deletion, resulting in a frameshift that should disrupt the C-terminal half of the protein but leave the presumed DNA binding domain intact. Expression analyses showed that despite the seed-specific nature of the mutant phenotype, ABI4 expression is not seed specific. PMID:9634591

  12. Time dependent inhibition of xanthine oxidase in irradiated solutions of folic acid, aminopterin and methotrexate

    SciTech Connect

    Robinson, K.; Pilot, T.F.; Meany, J.E. )

    1990-01-01

    The xanthine oxidase catalyzed oxidation of hypoxanthine was followed by monitoring the formation of uric acid at 290 nm. Inhibition of xanthine oxidase occurs in aqueous solutions of folic acid methotrexate and aminopterin. These compounds are known to dissociate upon exposure to ultraviolet light resulting in the formation of their respective 6-formylpteridine derivatives. The relative rates of dissociation were monitored spectrophotometrically by determining the absorbance of their 2,4-dinitrophenylhydrazine derivatives at 500 nm. When aqueous solutions of folic acid, aminopterin and methotrexate were exposed to uv light, a direct correlation was observed between the concentrations of the 6-formylpteridine derivatives existing in solution and the ability of these solutions to inhibit xanthine oxidase. The relative potency of the respective photolysis products were estimated.

  13. Tannic Acid Inhibits Hepatitis C Virus Entry into Huh7.5 Cells

    PubMed Central

    Hagedorn, Curt H.

    2015-01-01

    Chronic infection with the hepatitis C virus (HCV) is a cause of cirrhosis and hepatocellular carcinoma worldwide. Although antiviral therapy has dramatically improved recently, a number of patients remain untreated and some do not clear infection with treatment. Viral entry is an essential step in initiating and maintaining chronic HCV infections. One dramatic example of this is the nearly 100% infection of newly transplanted livers in patients with chronic hepatitis C. HCV entry inhibitors could play a critical role in preventing HCV infection of newly transplanted livers. Tannic acid, a polymer of gallic acid and glucose molecules, is a plant-derived polyphenol that defends some plants from insects and microbial infections. It has been shown to have a variety of biological effects, including antiviral activity, and is used as a flavoring agent in foods and beverages. In this study, we demonstrate that tannic acid is a potent inhibitor of HCV entry into Huh7.5 cells at low concentrations (IC50 5.8 μM). It also blocks cell-to-cell spread in infectious HCV cell cultures, but does not inhibit HCV replication following infection. Moreover, experimental results indicate that tannic acid inhibits an early step of viral entry, such as the docking of HCV at the cell surface. Gallic acid, tannic acid’s structural component, did not show any anti-HCV activity including inhibition of HCV entry or replication at concentrations up to 25 μM. It is possible the tannin structure is related on the effect on HCV inhibition. Tannic acid, which is widely distributed in plants and foods, has HCV antiviral activity in cell culture at low micromolar concentrations, may provide a relative inexpensive adjuvant to direct-acting HCV antivirals and warrants future investigation. PMID:26186636

  14. Inhibition of N2 fixation in soybean is associated with elevated ureides and amino acids.

    PubMed

    King, C Andy; Purcell, Larry C

    2005-04-01

    Decreased N2 fixation in soybean (Glycine max) L. Merr. during water deficits has been associated with increases in ureides and free amino acids in plant tissues, indicating a potential feedback inhibition by these compounds in response to drought. We evaluated concentrations of ureides and amino acids in leaf and nodule tissue and the concurrent change in N2 fixation in response to exogenous ureides and soil-water treatments for the cultivars Jackson and KS4895. Exogenous ureides applied to the soil and water-deficit treatments inhibited N2 fixation by 85% to 90%. Mn fertilization increased the apparent catabolism of ureides in leaves and hastened the recovery of N2 fixation following exogenous ureide application for both cultivars. Ureides and total free amino acids in leaves and nodules increased during water deficits and coincided with a decline in N2 fixation for both cultivars. N2 fixation recovered to 74% to 90% of control levels 2 d after rewatering drought-stressed plants, but leaf ureides and total nodule amino acids remained elevated in KS4895. Asparagine accounted for 82% of the increase in nodule amino acids relative to well-watered plants at 2 d after rewatering. These results indicate that leaf ureides and nodule asparagine do not feedback inhibit N2 fixation. Compounds whose increase and decrease in concentration mirrored the decline and recovery of N2 fixation included nodule ureides, nodule aspartate, and several amino acids in leaves, indicating that these are potential candidate molecules for feedback inhibition of N2 fixation.

  15. Use of jasmonic acid and salicylic acid to inhibit growth of sugarbeet storage rot pathogens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Jasmonic acid (JA) and salicylic acid (SA) are endogenous plant hormones that induce native plant defense responses and provide protection against a wide range of diseases. Previously, JA, applied after harvest, was shown to protect sugarbeet roots against the storage pathogens, Botrytis cinerea, P...

  16. Root ABA Accumulation Enhances Rice Seedling Drought Tolerance under Ammonium Supply: Interaction with Aquaporins

    PubMed Central

    Ding, Lei; Li, Yingrui; Wang, Ying; Gao, Limin; Wang, Min; Chaumont, François; Shen, Qirong; Guo, Shiwei

    2016-01-01

    In previous studies, we demonstrated that ammonium nutrition enhances the drought tolerance of rice seedlings compared to nitrate nutrition and contributes to a higher root water uptake ability. It remains unclear why rice seedlings maintain a higher water uptake ability when supplied with ammonium under drought stress. Here, we focused on the effects of nitrogen form and drought stress on root abscisic acid (ABA) concentration and aquaporin expression using hydroponics experiments and stimulating drought stress with 10% PEG6000. Drought stress decreased the leaf photosynthetic rate and stomatal conductivity and increased the leaf temperature of plants supplied with either ammonium or nitrate, but especially under nitrate supply. After 4 h of PEG treatment, the root protoplast water permeability and the expression of root PIP and TIP genes decreased in plants supplied with ammonium or nitrate. After 24 h of PEG treatment, the root hydraulic conductivity, the protoplast water permeability, and the expression of some aquaporin genes increased in plants supplied with ammonium compared to those under non-PEG treatment. Root ABA accumulation was induced by 24 h of PEG treatment, especially in plants supplied with ammonium. The addition of exogenous ABA decreased the expression of PIP and TIP genes under non-PEG treatment but increased the expression of some of them under PEG treatment. We concluded that drought stress induced a down-regulation of aquaporin expression, which appeared earlier than did root ABA accumulation. With continued drought stress, aquaporin expression and activity increased due to root ABA accumulation in plants supplied with ammonium. PMID:27559341

  17. Root ABA Accumulation Enhances Rice Seedling Drought Tolerance under Ammonium Supply: Interaction with Aquaporins.

    PubMed

    Ding, Lei; Li, Yingrui; Wang, Ying; Gao, Limin; Wang, Min; Chaumont, François; Shen, Qirong; Guo, Shiwei

    2016-01-01

    In previous studies, we demonstrated that ammonium nutrition enhances the drought tolerance of rice seedlings compared to nitrate nutrition and contributes to a higher root water uptake ability. It remains unclear why rice seedlings maintain a higher water uptake ability when supplied with ammonium under drought stress. Here, we focused on the effects of nitrogen form and drought stress on root abscisic acid (ABA) concentration and aquaporin expression using hydroponics experiments and stimulating drought stress with 10% PEG6000. Drought stress decreased the leaf photosynthetic rate and stomatal conductivity and increased the leaf temperature of plants supplied with either ammonium or nitrate, but especially under nitrate supply. After 4 h of PEG treatment, the root protoplast water permeability and the expression of root PIP and TIP genes decreased in plants supplied with ammonium or nitrate. After 24 h of PEG treatment, the root hydraulic conductivity, the protoplast water permeability, and the expression of some aquaporin genes increased in plants supplied with ammonium compared to those under non-PEG treatment. Root ABA accumulation was induced by 24 h of PEG treatment, especially in plants supplied with ammonium. The addition of exogenous ABA decreased the expression of PIP and TIP genes under non-PEG treatment but increased the expression of some of them under PEG treatment. We concluded that drought stress induced a down-regulation of aquaporin expression, which appeared earlier than did root ABA accumulation. With continued drought stress, aquaporin expression and activity increased due to root ABA accumulation in plants supplied with ammonium. PMID:27559341

  18. In vitro inhibition of salicylic acid derivatives on human cytosolic carbonic anhydrase isozymes I and II.

    PubMed

    Bayram, Esra; Senturk, Murat; Kufrevioglu, O Irfan; Supuran, Claudiu T

    2008-10-15

    The inhibition of two human cytosolic carbonic anhydrase (hCA, EC 4.2.1.1) isozymes, hCA I and II, with a series of salicylic acid derivatives was investigated by using the esterase method with 4-nitrophenyl acetate as substrate. IC(50) values for sulfasalazine, diflunisal, 5-chlorosalicylic