The Experts below are selected from a list of 40668 Experts worldwide ranked by ideXlab platform
Kazuo Shinozaki - One of the best experts on this subject based on the ideXlab platform.
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antagonistic interaction between map kinase and protein phosphatase 2c in stress recovery
Plant Science, 2006Co-Authors: Jeffrey Leung, Jerome Giraudat, Tsuyoshi Mizoguchi, Kazuo Shinozaki, Sofia Orfanidi, Francoise Chefdor, Tamas Meszaros, Susanne Bolte, Laszlo BogreAbstract:The Arabidopsis mitogen-activated kinase MPK6 transmits a diversity of stress signals. However, much less is known about resetting mechanisms subsequent to the stress response. We show that MPK6 is a potential target of abscisic acid-insensitive 1 (ABI1), a protein phosphatase 2C that acts as a key element in attenuating abscisic acid (ABA)-dependent stress signaling. MPK6 can bind to ABI1 in vitro and in yeast, and that a complex containing these two proteins can be co-precipitated from transfected Arabidopsis cells. In whole plants, MPK6 is hyper-reactive to osmotic stress in mutants compromised in ABI1 activity, but not in its closest functional homolog ABI2. Moreover, conditional expression of a dominant-negative form of mpk6 renders plants hypersensitive to ABA. MPK6 enhances the synthesis of ethylene [1]. ABI1 may therefore down modulate ethylene as part of the resetting mechanism after stress.
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the regulatory domain of srk2e ost1 snrk2 6 interacts with ABI1 and integrates abscisic acid aba and osmotic stress signals controlling stomatal closure in arabidopsis
Journal of Biological Chemistry, 2006Co-Authors: Riichiro Yoshida, Taishi Umezawa, Tsuyoshi Mizoguchi, Seiji Takahashi, Fuminori Takahashi, Kazuo ShinozakiAbstract:ABI1 and ABI2 encode PP2C-type protein phosphatases and are thought to negatively regulate many aspects of abscisic acid (ABA) signaling, including stomatal closure in Arabidopsis. In contrast, SRK2E/OST1/SnRK2.6 encodes an Arabidopsis SnRK2 protein kinase and acts as a positive regulator in the ABA-induced stomatal closure. SRK2E/OST1 is activated by osmotic stress as well as by ABA, but the independence of the two activation processes has not yet been determined. Additionally, interaction between SRK2E/OST1 and PP2C-type phosphatases (ABI1 and ABI2) is not understood. In the present study, we demonstrated that the ABI1-1 mutation, but not the abi2-1 mutation, strongly inhibited ABA-dependent SRK2E/OST1 activation. In contrast, osmotic stress activated SRK2E/OST1 even in ABI1-1 and aba2-1 plants. The C-terminal regulatory domain of SRK2E/OST1 was required for its activation by both ABA and osmotic stress in Arabidopsis. The C-terminal domain was functionally divided into Domains I and II. Domain II was required only for the ABA-dependent activation of SRK2E/OST1, whereas Domain I was responsible for the ABA-independent activation. Full-length SRK2E/OST1 completely complemented the wilty phenotype of the srk2e mutant, but SRK2E/OST1 lacking Domain II did not. Domain II interacted with the ABI1 protein in a yeast two-hybrid assay. Our results suggested that the direct interaction between SRK2E/OST1 and ABI1 through Domain II plays a critical role in the control of stomatal closure.
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Transcriptional Regulation of ABI3- and ABA-responsive Genes Including RD29B and RD29A in Seeds, Germinating Embryos, and Seedlings of Arabidopsis
Plant Molecular Biology, 2006Co-Authors: Kazuo Nakashima, Kazuo Shinozaki, Yasunari Fujita, Koji Katsura, Kyonoshin Maruyama, Yoshihiro Narusaka, Motoaki Seki, Kazuko Yamaguchi-shinozakiAbstract:ABA-responsive elements (ABREs) are cis -acting elements and basic leucine zipper (bZIP)-type ABRE-binding proteins (AREBs) are transcriptional activators that function in the expression of RD29B in vegetative tissue of Arabidopsis in response to abscisic acid (ABA) treatment. Dehydration-responsive elements (DREs) function as coupling elements of ABRE in the expression of RD29A in response to ABA. Expression analysis using abi3 and abi5 mutants showed that ABI3 and ABI5 play important roles in the expression of RD29B in seeds. Base-substitution analysis showed that two ABREs function strongly and one ABRE coupled with DRE functions weakly in the expression of RD29A in embryos. In a transient transactivation experiment, ABI3, ABI5 and AREB1 activated transcription of a GUS reporter gene driven by the RD29B promoter strongly but these proteins activated the transcription driven by the RD29A promoter weakly. In 35S :: ABI3 Arabidopsis plants, the expression of RD29B was up-regulated strongly, but that of RD29A was up-regulated weakly. These results indicate that the expression of RD29B having ABREs in the promoter is up-regulated strongly by ABI3, whereas that of RD29A having one ABRE coupled with DREs in the promoter is up-regulated weakly by ABI3. We compared the expression of 7000 Arabidopsis genes in response to ABA treatment during germination and in the vegetative growth stage, and that in 35S :: ABI3 plants using a full-length cDNA microarray. The expression of ABI3- and/or ABA-responsive genes and cis -elements in the promoters are discussed.
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The regulatory domain of SRK2E/OST1/SnRK2.6 interacts with ABI1 and integrates abscisic acid (ABA) and osmotic stress signals controlling stomatal closure in Arabidopsis
The Journal of biological chemistry, 2005Co-Authors: Riichiro Yoshida, Taishi Umezawa, Tsuyoshi Mizoguchi, Seiji Takahashi, Fuminori Takahashi, Kazuo ShinozakiAbstract:ABI1 and ABI2 encode PP2C-type protein phosphatases and are thought to negatively regulate many aspects of abscisic acid (ABA) signaling, including stomatal closure in Arabidopsis. In contrast, SRK2E/OST1/SnRK2.6 encodes an Arabidopsis SnRK2 protein kinase and acts as a positive regulator in the ABA-induced stomatal closure. SRK2E/OST1 is activated by osmotic stress as well as by ABA, but the independence of the two activation processes has not yet been determined. Additionally, interaction between SRK2E/OST1 and PP2C-type phosphatases (ABI1 and ABI2) is not understood. In the present study, we demonstrated that the ABI1-1 mutation, but not the abi2-1 mutation, strongly inhibited ABA-dependent SRK2E/OST1 activation. In contrast, osmotic stress activated SRK2E/OST1 even in ABI1-1 and aba2-1 plants. The C-terminal regulatory domain of SRK2E/OST1 was required for its activation by both ABA and osmotic stress in Arabidopsis. The C-terminal domain was functionally divided into Domains I and II. Domain II was required only for the ABA-dependent activation of SRK2E/OST1, whereas Domain I was responsible for the ABA-independent activation. Full-length SRK2E/OST1 completely complemented the wilty phenotype of the srk2e mutant, but SRK2E/OST1 lacking Domain II did not. Domain II interacted with the ABI1 protein in a yeast two-hybrid assay. Our results suggested that the direct interaction between SRK2E/OST1 and ABI1 through Domain II plays a critical role in the control of stomatal closure.
Julian I. Schroeder - One of the best experts on this subject based on the ideXlab platform.
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reconstitution of abscisic acid activation of slac1 anion channel by cpk6 and ost1 kinases and branched ABI1 pp2c phosphatase action
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Benjamin Brandt, Majid Ghassemian, Dennis E Brodsky, Shaowu Xue, Juntaro Negi, Koh Iba, Jaakko Kangasjarvi, Aaron B Stephan, Julian I. SchroederAbstract:The plant hormone abscisic acid (ABA) is produced in response to abiotic stresses and mediates stomatal closure in response to drought via recently identified ABA receptors (pyrabactin resistance/regulatory component of ABA receptor; PYR/RCAR). SLAC1 encodes a central guard cell S-type anion channel that mediates ABA-induced stomatal closure. Coexpression of the calcium-dependent protein kinase 21 (CPK21), CPK23, or the Open Stomata 1 kinase (OST1) activates SLAC1 anion currents. However, reconstitution of ABA activation of any plant ion channel has not yet been attained. Whether the known core ABA signaling components are sufficient for ABA activation of SLAC1 anion channels or whether additional components are required remains unknown. The Ca2+-dependent protein kinase CPK6 is known to function in vivo in ABA-induced stomatal closure. Here we show that CPK6 robustly activates SLAC1-mediated currents and phosphorylates the SLAC1 N terminus. A phosphorylation site (S59) in SLAC1, crucial for CPK6 activation, was identified. The group A PP2Cs ABI1, ABI2, and PP2CA down-regulated CPK6-mediated SLAC1 activity in oocytes. Unexpectedly, ABI1 directly dephosphorylated the N terminus of SLAC1, indicating an alternate branched early ABA signaling core in which ABI1 targets SLAC1 directly (down-regulation). Furthermore, here we have successfully reconstituted ABA-induced activation of SLAC1 channels in oocytes using the ABA receptor pyrabactin resistant 1 (PYR1) and PP2C phosphatases with two alternate signaling cores including either CPK6 or OST1. Point mutations in ABI1 disrupting PYR1–ABI1 interaction abolished ABA signal transduction. Moreover, by addition of CPK6, a functional ABA signal transduction core from ABA receptors to ion channel activation was reconstituted without a SnRK2 kinase.
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triple loss of function of protein phosphatases type 2c leads to partial constitutive response to endogenous abscisic acid
Plant Physiology, 2009Co-Authors: Silvia Rubio, Julian I. Schroeder, Americo Rodrigues, Angela Saez, Marie B Dizon, Alexander Galle, Taehoun Kim, Julia Santiago, Jaume Flexas, Pedro L RodriguezAbstract:The phytohormone abscisic acid (ABA) is a key regulator of plant growth and development as well as plant responses to situations of decreased water availability. Protein phosphatases type 2C (PP2Cs) from group A, which includes the ABI1/HAB1 and PP2CA branches, are key negative regulators of ABA signaling. Specifically, HAB1, ABI1, ABI2, and PP2CA have been shown to affect both seed and vegetative responses to ABA. To further understand their contribution to ABA signaling and to unravel possible genetic interactions and functional redundancy among them, we have generated different combinations of double and triple mutants impaired in these PP2Cs. Interestingly, hab1-1pp2ca-1 and ABI1-2pp2ca-1 double mutants showed reduced water loss and enhanced resistance to drought stress, which further supports the role of PP2CA in vegetative responses to ABA. Two triple hab1-1ABI1-2abi2-2 and hab1-1ABI1-2pp2ca-1 mutants were generated, which showed an extreme response to exogenous ABA, impaired growth, and partial constitutive response to endogenous ABA. Thus, transcriptomic analysis revealed a partial up-regulation/down-regulation of a subset of ABA-responsive genes in both triple mutants in the absence of exogenous ABA. Comparison of ABA responses in the different pp2c mutants showed that a progressive increase in ABA sensitivity could be obtained through combined inactivation of these PP2Cs. These results indicate that ABA response is finely tuned by the integrated action of these genes, which is required to prevent a constitutive response to endogenous ABA that might have a deleterious effect on growth and development in the absence of environmental stress.
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enhancement of abscisic acid sensitivity and reduction of water consumption in arabidopsis by combined inactivation of the protein phosphatases type 2c ABI1 and hab1
Plant Physiology, 2006Co-Authors: Angela Saez, Julian I. Schroeder, Nadia Robert, Mohammad H Maktabi, Ramon Serrano, Pedro L RodriguezAbstract:Abscisic acid (ABA) plays a key role in plant responses to abiotic stress, particularly drought stress. A wide number of ABA-hypersensitive mutants is known, however, only a few of them resist/avoid drought stress. In this work we have generated ABA-hypersensitive drought-avoidant mutants by simultaneous inactivation of two negative regulators of ABA signaling, i.e. the protein phosphatases type 2C (PP2Cs) ABA-INSENSITIVE1 (ABI1) and HYPERSENSITIVE TO ABA1 (HAB1). Two new recessive loss-of-function alleles of ABI1, ABI1-2 and ABI1-3, were identified in an Arabidopsis (Arabidopsis thaliana) T-DNA collection. These mutants showed enhanced responses to ABA both in seed and vegetative tissues, but only a limited effect on plant drought avoidance. In contrast, generation of double hab1-1 ABI1-2 and hab1-1 ABI1-3 mutants strongly increased plant responsiveness to ABA. Thus, both hab1-1 ABI1-2 and hab1-1 ABI1-3 were particularly sensitive to ABA-mediated inhibition of seed germination. Additionally, vegetative responses to ABA were reinforced in the double mutants, which showed a strong hypersensitivity to ABA in growth assays, stomatal closure, and induction of ABA-responsive genes. Transpirational water loss under drought conditions was noticeably reduced in the double mutants as compared to single parental mutants, which resulted in reduced water consumption of whole plants. Taken together, these results reveal cooperative negative regulation of ABA signaling by ABI1 and HAB1 and suggest that fine tuning of ABA signaling can be attained through combined action of PP2Cs. Finally, these results suggest that combined inactivation of specific PP2Cs involved in ABA signaling could provide an approach for improving crop performance under drought stress conditions.
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localization ion channel regulation and genetic interactions during abscisic acid signaling of the nuclear mrna cap binding protein abh1
Plant Physiology, 2002Co-Authors: Veronique Hugouvieux, Yoshiyuki Murata, Jared Young, June M Kwak, Daniel Z Mackesy, Julian I. SchroederAbstract:Abscisic acid (ABA) regulates developmental processes and abiotic stress responses in plants. We recently characterized a new Arabidopsis mutant, abh1, which shows ABA-hypersensitive regulation of seed germination, stomatal closing, and cytosolic calcium increases in guard cells (V. Hugouvieux, J.M. Kwak, J.I. Schroeder [2001] Cell 106: 477-487). ABH1 encodes the large subunit of a dimeric Arabidopsis mRNA cap-binding complex and in expression profiling experiments was shown to affect mRNA levels of a subset of genes. Here, we show that the dimeric ABH1 and AtCBP20 subunits are ubiquitously expressed. Whole-plant growth phenotypes of abh1 are described and properties of ABH1 in guard cells are further analyzed. Complemented abh1 lines expressing a green fluorescent protein-ABH1 fusion protein demonstrate that ABH1 mainly localizes in guard cell nuclei. Stomatal apertures were smaller in abh1 compared with wild type (WT) when plants were grown at 40% humidity, and similar at 95% humidity. Correlated with stomatal apertures from plants grown at 40% humidity, slow anion channel currents were enhanced and inward potassium channel currents were decreased in abh1 guard cells compared with WT. Gas exchange measurements showed similar primary humidity responses in abh1 and WT, which together with results from abh1/ABI1-1 double-mutant analyses suggest that abh1 shows enhanced sensitivity to endogenous ABA. Double-mutant analyses of the ABA-hypersensitive signaling mutants, era1-2 and abh1, showed complex genetic interactions, suggesting that ABH1 and ERA1 do not modulate the same negative regulator in ABA signaling. Mutations in the RNA-binding protein sad1 showed hypersensitive ABA-induced stomatal closing, whereas hyl1 did not affect this response. These data provide evidence for the model that the mRNA-processing proteins ABH1 and SAD1 function as negative regulators in guard cell ABA signaling.
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abscisic acid activation of plasma membrane ca2 channels in guard cells requires cytosolic nad p h and is differentially disrupted upstream and downstream of reactive oxygen species production in ABI1 1 and abi2 1 protein phosphatase 2c mutants
The Plant Cell, 2001Co-Authors: Yoshiyuki Murata, Izumi C. Mori, Zhenming Pei, Julian I. SchroederAbstract:The hormone abscisic acid (ABA) regulates stress responses and developmental processes in plants. Calcium-permeable channels activated by reactive oxygen species (ROS) have been shown recently to function in the ABA signaling network in Arabidopsis guard cells. Here, we report that ABA activation of these ICa Ca2+ channels requires the presence of NAD(P)H in the cytosol. The protein phosphatase 2C (PP2C) mutant ABI1-1 disrupted ABA activation of ICa channels. Moreover, in ABI1-1, ABA did not induce ROS production. Consistent with these findings, in ABI1-1, H2O2 activation of ICa channels and H2O2-induced stomatal closing were not disrupted, suggesting that ABI1-1 impairs ABA signaling between ABA reception and ROS production. The abi2-1 mutation, which lies in a distinct PP2C gene, also disrupted ABA activation of ICa. However, in contrast to ABI1-1, abi2-1 impaired both H2O2 activation of ICa and H2O2-induced stomatal closing. Furthermore, ABA elicited ROS production in abi2-1. These data suggest a model with the following sequence of events in early ABA signal transduction: ABA, ABI1-1, NAD(P)H-dependent ROS production, abi2-1, ICa Ca2+ channel activation followed by stomatal closing.
Riichiro Yoshida - One of the best experts on this subject based on the ideXlab platform.
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the regulatory domain of srk2e ost1 snrk2 6 interacts with ABI1 and integrates abscisic acid aba and osmotic stress signals controlling stomatal closure in arabidopsis
Journal of Biological Chemistry, 2006Co-Authors: Riichiro Yoshida, Taishi Umezawa, Tsuyoshi Mizoguchi, Seiji Takahashi, Fuminori Takahashi, Kazuo ShinozakiAbstract:ABI1 and ABI2 encode PP2C-type protein phosphatases and are thought to negatively regulate many aspects of abscisic acid (ABA) signaling, including stomatal closure in Arabidopsis. In contrast, SRK2E/OST1/SnRK2.6 encodes an Arabidopsis SnRK2 protein kinase and acts as a positive regulator in the ABA-induced stomatal closure. SRK2E/OST1 is activated by osmotic stress as well as by ABA, but the independence of the two activation processes has not yet been determined. Additionally, interaction between SRK2E/OST1 and PP2C-type phosphatases (ABI1 and ABI2) is not understood. In the present study, we demonstrated that the ABI1-1 mutation, but not the abi2-1 mutation, strongly inhibited ABA-dependent SRK2E/OST1 activation. In contrast, osmotic stress activated SRK2E/OST1 even in ABI1-1 and aba2-1 plants. The C-terminal regulatory domain of SRK2E/OST1 was required for its activation by both ABA and osmotic stress in Arabidopsis. The C-terminal domain was functionally divided into Domains I and II. Domain II was required only for the ABA-dependent activation of SRK2E/OST1, whereas Domain I was responsible for the ABA-independent activation. Full-length SRK2E/OST1 completely complemented the wilty phenotype of the srk2e mutant, but SRK2E/OST1 lacking Domain II did not. Domain II interacted with the ABI1 protein in a yeast two-hybrid assay. Our results suggested that the direct interaction between SRK2E/OST1 and ABI1 through Domain II plays a critical role in the control of stomatal closure.
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The regulatory domain of SRK2E/OST1/SnRK2.6 interacts with ABI1 and integrates abscisic acid (ABA) and osmotic stress signals controlling stomatal closure in Arabidopsis
The Journal of biological chemistry, 2005Co-Authors: Riichiro Yoshida, Taishi Umezawa, Tsuyoshi Mizoguchi, Seiji Takahashi, Fuminori Takahashi, Kazuo ShinozakiAbstract:ABI1 and ABI2 encode PP2C-type protein phosphatases and are thought to negatively regulate many aspects of abscisic acid (ABA) signaling, including stomatal closure in Arabidopsis. In contrast, SRK2E/OST1/SnRK2.6 encodes an Arabidopsis SnRK2 protein kinase and acts as a positive regulator in the ABA-induced stomatal closure. SRK2E/OST1 is activated by osmotic stress as well as by ABA, but the independence of the two activation processes has not yet been determined. Additionally, interaction between SRK2E/OST1 and PP2C-type phosphatases (ABI1 and ABI2) is not understood. In the present study, we demonstrated that the ABI1-1 mutation, but not the abi2-1 mutation, strongly inhibited ABA-dependent SRK2E/OST1 activation. In contrast, osmotic stress activated SRK2E/OST1 even in ABI1-1 and aba2-1 plants. The C-terminal regulatory domain of SRK2E/OST1 was required for its activation by both ABA and osmotic stress in Arabidopsis. The C-terminal domain was functionally divided into Domains I and II. Domain II was required only for the ABA-dependent activation of SRK2E/OST1, whereas Domain I was responsible for the ABA-independent activation. Full-length SRK2E/OST1 completely complemented the wilty phenotype of the srk2e mutant, but SRK2E/OST1 lacking Domain II did not. Domain II interacted with the ABI1 protein in a yeast two-hybrid assay. Our results suggested that the direct interaction between SRK2E/OST1 and ABI1 through Domain II plays a critical role in the control of stomatal closure.
Tsuyoshi Mizoguchi - One of the best experts on this subject based on the ideXlab platform.
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antagonistic interaction between map kinase and protein phosphatase 2c in stress recovery
Plant Science, 2006Co-Authors: Jeffrey Leung, Jerome Giraudat, Tsuyoshi Mizoguchi, Kazuo Shinozaki, Sofia Orfanidi, Francoise Chefdor, Tamas Meszaros, Susanne Bolte, Laszlo BogreAbstract:The Arabidopsis mitogen-activated kinase MPK6 transmits a diversity of stress signals. However, much less is known about resetting mechanisms subsequent to the stress response. We show that MPK6 is a potential target of abscisic acid-insensitive 1 (ABI1), a protein phosphatase 2C that acts as a key element in attenuating abscisic acid (ABA)-dependent stress signaling. MPK6 can bind to ABI1 in vitro and in yeast, and that a complex containing these two proteins can be co-precipitated from transfected Arabidopsis cells. In whole plants, MPK6 is hyper-reactive to osmotic stress in mutants compromised in ABI1 activity, but not in its closest functional homolog ABI2. Moreover, conditional expression of a dominant-negative form of mpk6 renders plants hypersensitive to ABA. MPK6 enhances the synthesis of ethylene [1]. ABI1 may therefore down modulate ethylene as part of the resetting mechanism after stress.
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the regulatory domain of srk2e ost1 snrk2 6 interacts with ABI1 and integrates abscisic acid aba and osmotic stress signals controlling stomatal closure in arabidopsis
Journal of Biological Chemistry, 2006Co-Authors: Riichiro Yoshida, Taishi Umezawa, Tsuyoshi Mizoguchi, Seiji Takahashi, Fuminori Takahashi, Kazuo ShinozakiAbstract:ABI1 and ABI2 encode PP2C-type protein phosphatases and are thought to negatively regulate many aspects of abscisic acid (ABA) signaling, including stomatal closure in Arabidopsis. In contrast, SRK2E/OST1/SnRK2.6 encodes an Arabidopsis SnRK2 protein kinase and acts as a positive regulator in the ABA-induced stomatal closure. SRK2E/OST1 is activated by osmotic stress as well as by ABA, but the independence of the two activation processes has not yet been determined. Additionally, interaction between SRK2E/OST1 and PP2C-type phosphatases (ABI1 and ABI2) is not understood. In the present study, we demonstrated that the ABI1-1 mutation, but not the abi2-1 mutation, strongly inhibited ABA-dependent SRK2E/OST1 activation. In contrast, osmotic stress activated SRK2E/OST1 even in ABI1-1 and aba2-1 plants. The C-terminal regulatory domain of SRK2E/OST1 was required for its activation by both ABA and osmotic stress in Arabidopsis. The C-terminal domain was functionally divided into Domains I and II. Domain II was required only for the ABA-dependent activation of SRK2E/OST1, whereas Domain I was responsible for the ABA-independent activation. Full-length SRK2E/OST1 completely complemented the wilty phenotype of the srk2e mutant, but SRK2E/OST1 lacking Domain II did not. Domain II interacted with the ABI1 protein in a yeast two-hybrid assay. Our results suggested that the direct interaction between SRK2E/OST1 and ABI1 through Domain II plays a critical role in the control of stomatal closure.
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The regulatory domain of SRK2E/OST1/SnRK2.6 interacts with ABI1 and integrates abscisic acid (ABA) and osmotic stress signals controlling stomatal closure in Arabidopsis
The Journal of biological chemistry, 2005Co-Authors: Riichiro Yoshida, Taishi Umezawa, Tsuyoshi Mizoguchi, Seiji Takahashi, Fuminori Takahashi, Kazuo ShinozakiAbstract:ABI1 and ABI2 encode PP2C-type protein phosphatases and are thought to negatively regulate many aspects of abscisic acid (ABA) signaling, including stomatal closure in Arabidopsis. In contrast, SRK2E/OST1/SnRK2.6 encodes an Arabidopsis SnRK2 protein kinase and acts as a positive regulator in the ABA-induced stomatal closure. SRK2E/OST1 is activated by osmotic stress as well as by ABA, but the independence of the two activation processes has not yet been determined. Additionally, interaction between SRK2E/OST1 and PP2C-type phosphatases (ABI1 and ABI2) is not understood. In the present study, we demonstrated that the ABI1-1 mutation, but not the abi2-1 mutation, strongly inhibited ABA-dependent SRK2E/OST1 activation. In contrast, osmotic stress activated SRK2E/OST1 even in ABI1-1 and aba2-1 plants. The C-terminal regulatory domain of SRK2E/OST1 was required for its activation by both ABA and osmotic stress in Arabidopsis. The C-terminal domain was functionally divided into Domains I and II. Domain II was required only for the ABA-dependent activation of SRK2E/OST1, whereas Domain I was responsible for the ABA-independent activation. Full-length SRK2E/OST1 completely complemented the wilty phenotype of the srk2e mutant, but SRK2E/OST1 lacking Domain II did not. Domain II interacted with the ABI1 protein in a yeast two-hybrid assay. Our results suggested that the direct interaction between SRK2E/OST1 and ABI1 through Domain II plays a critical role in the control of stomatal closure.
Pedro L Rodriguez - One of the best experts on this subject based on the ideXlab platform.
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HRS1 acts as a negative regulator of abscisic acid signaling to promote timely germination of Arabidopsis seeds.
PLOS ONE, 2012Co-Authors: Chongming Wu, Pedro L Rodriguez, Huixia Yang, Juanjuan Feng, Ran Wang, Daowen WangAbstract:In this work, we conducted functional analysis of Arabidopsis HRS1 gene in order to provide new insights into the mechanisms governing seed germination. Compared with wild type (WT) control, HRS1 knockout mutant (hrs1-1) exhibited significant germination delays on either normal medium or those supplemented with abscisic acid (ABA) or sodium chloride (NaCl), with the magnitude of the delay being substantially larger on the latter media. The hypersensitivity of hrs1-1 germination to ABA and NaCl required ABI3, ABI4 and ABI5, and was aggravated in the double mutant hrs1-1ABI1-2 and triple mutant hrs1-1hab1-1ABI1-2, indicating that HRS1 acts as a negative regulator of ABA signaling during seed germination. Consistent with this notion, HRS1 expression was found in the embryo axis, and was regulated both temporally and spatially, during seed germination. Further analysis showed that the delay of hrs1-1 germination under normal conditions was associated with reduction in the elongation of the cells located in the lower hypocotyl (LH) and transition zone (TZ) of embryo axis. Interestingly, the germination rate of hrs1-1 was more severely reduced by the inhibitor of cell elongation, and more significantly decreased by the suppressors of plasmalemma H+-ATPase activity, than that of WT control. The plasmalemma H+-ATPase activity in the germinating seeds of hrs1-1 was substantially lower than that exhibited by WT control, and fusicoccin, an activator of this pump, corrected the transient germination delay of hrs1-1. Together, our data suggest that HRS1 may be needed for suppressing ABA signaling in germinating embryo axis, which promotes the timely germination of Arabidopsis seeds probably by facilitating the proper function of plasmalemma H+-ATPase and the efficient elongation of LH and TZ cells.
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triple loss of function of protein phosphatases type 2c leads to partial constitutive response to endogenous abscisic acid
Plant Physiology, 2009Co-Authors: Silvia Rubio, Julian I. Schroeder, Americo Rodrigues, Angela Saez, Marie B Dizon, Alexander Galle, Taehoun Kim, Julia Santiago, Jaume Flexas, Pedro L RodriguezAbstract:The phytohormone abscisic acid (ABA) is a key regulator of plant growth and development as well as plant responses to situations of decreased water availability. Protein phosphatases type 2C (PP2Cs) from group A, which includes the ABI1/HAB1 and PP2CA branches, are key negative regulators of ABA signaling. Specifically, HAB1, ABI1, ABI2, and PP2CA have been shown to affect both seed and vegetative responses to ABA. To further understand their contribution to ABA signaling and to unravel possible genetic interactions and functional redundancy among them, we have generated different combinations of double and triple mutants impaired in these PP2Cs. Interestingly, hab1-1pp2ca-1 and ABI1-2pp2ca-1 double mutants showed reduced water loss and enhanced resistance to drought stress, which further supports the role of PP2CA in vegetative responses to ABA. Two triple hab1-1ABI1-2abi2-2 and hab1-1ABI1-2pp2ca-1 mutants were generated, which showed an extreme response to exogenous ABA, impaired growth, and partial constitutive response to endogenous ABA. Thus, transcriptomic analysis revealed a partial up-regulation/down-regulation of a subset of ABA-responsive genes in both triple mutants in the absence of exogenous ABA. Comparison of ABA responses in the different pp2c mutants showed that a progressive increase in ABA sensitivity could be obtained through combined inactivation of these PP2Cs. These results indicate that ABA response is finely tuned by the integrated action of these genes, which is required to prevent a constitutive response to endogenous ABA that might have a deleterious effect on growth and development in the absence of environmental stress.
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enhancement of abscisic acid sensitivity and reduction of water consumption in arabidopsis by combined inactivation of the protein phosphatases type 2c ABI1 and hab1
Plant Physiology, 2006Co-Authors: Angela Saez, Julian I. Schroeder, Nadia Robert, Mohammad H Maktabi, Ramon Serrano, Pedro L RodriguezAbstract:Abscisic acid (ABA) plays a key role in plant responses to abiotic stress, particularly drought stress. A wide number of ABA-hypersensitive mutants is known, however, only a few of them resist/avoid drought stress. In this work we have generated ABA-hypersensitive drought-avoidant mutants by simultaneous inactivation of two negative regulators of ABA signaling, i.e. the protein phosphatases type 2C (PP2Cs) ABA-INSENSITIVE1 (ABI1) and HYPERSENSITIVE TO ABA1 (HAB1). Two new recessive loss-of-function alleles of ABI1, ABI1-2 and ABI1-3, were identified in an Arabidopsis (Arabidopsis thaliana) T-DNA collection. These mutants showed enhanced responses to ABA both in seed and vegetative tissues, but only a limited effect on plant drought avoidance. In contrast, generation of double hab1-1 ABI1-2 and hab1-1 ABI1-3 mutants strongly increased plant responsiveness to ABA. Thus, both hab1-1 ABI1-2 and hab1-1 ABI1-3 were particularly sensitive to ABA-mediated inhibition of seed germination. Additionally, vegetative responses to ABA were reinforced in the double mutants, which showed a strong hypersensitivity to ABA in growth assays, stomatal closure, and induction of ABA-responsive genes. Transpirational water loss under drought conditions was noticeably reduced in the double mutants as compared to single parental mutants, which resulted in reduced water consumption of whole plants. Taken together, these results reveal cooperative negative regulation of ABA signaling by ABI1 and HAB1 and suggest that fine tuning of ABA signaling can be attained through combined action of PP2Cs. Finally, these results suggest that combined inactivation of specific PP2Cs involved in ABA signaling could provide an approach for improving crop performance under drought stress conditions.
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gain of function and loss of function phenotypes of the protein phosphatase 2c hab1 reveal its role as a negative regulator of abscisic acid signalling
Plant Journal, 2004Co-Authors: Angela Saez, Nadezda Apostolova, Miguel Gonzalezguzman, Mary Paz Gonzalezgarcia, Carlos Nicolas, Oscar Lorenzo, Pedro L RodriguezAbstract:HAB1 was originally cloned on the basis of sequence homology to ABI1 and ABI2, and indeed, a multiple sequence alignment of 32 Arabidopsis protein phosphatases type-2C (PP2Cs) reveals a cluster composed by the four closely related proteins, ABI1, ABI2, HAB1 and At1g17550 (here named HAB2). Characterisation of transgenic plants harbouring a transcriptional fusion ProHAB1: green fluorescent protein (GFP) indicates that HAB1 is broadly expressed within the plant, including key target sites of abscisic acid (ABA) action as guard cells or seeds. The expression of the HAB1 mRNA in vegetative tissues is strongly upregulated in response to exogenous ABA. In this work, we show that constitutive expression of HAB1 in Arabidopsis under a cauliflower mosaic virus (CaMV) 35S promoter led to reduced ABA sensitivity both in seeds and vegetative tissues, compared to wild-type plants. Thus, in the field of ABA signalling, this work represents an example of a stable phenotype in planta after sustained overexpression of a PP2C genes. Additionally, a recessive T-DNA insertion mutant of HAB1 was analysed in this work, whereas previous studies of recessive alleles of PP2C genes were carried out with intragenic revertants of the ABI1-1 and abi2-1 mutants that carry missense mutations in conserved regions of the PP2C domain. In the presence of exogenous ABA, hab1-1 mutant shows ABA-hypersensitive inhibition of seed germination; however, its transpiration rate was similar to that of wild-type plants. The ABA-hypersensitive phenotype of hab1-1 seeds together with the reduced ABA sensitivity of 35S:HAB1 plants are consistent with a role of HAB1 as a negative regulator of ABA signalling. Finally, these results provide new genetic evidence on the function of a PP2C in ABA signalling.
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the sensitivity of abi2 to hydrogen peroxide links the abscisic acid response regulator to redox signalling
Planta, 2002Co-Authors: Michael Meinhard, Pedro L Rodriguez, Erwin GrillAbstract:ABI1 and ABI2 are two protein serine/threonine phosphatases of type 2C (EC 3.1.3.16) that act as key regulators in the responses of Arabidopsis thaliana (L.) Heynh. to abscisic acid (ABA). They are involved in the control of ABA-mediated seed dormancy, stomatal closure and vegetative growth inhibition. Analysis of the enzymatic properties of ABI2 revealed high sensitivities towards protons and unsaturated fatty acids. Furthermore, the protein phosphatase activity of ABI2 is very sensitive to H2O2, which has recently emerged as a secondary messenger of ABA signalling. Upon H2O2 challenge, ABI2 is rapidly inactivated with an IC50 value of 50 µM in the presence of reduced glutathione. Inhibitor studies with phenylarsine oxide and manipulation of the redox status of ABI2 in vitro indicate that oxidation of critical cysteine residue(s) is responsible for inactivation. The levels of the major cellular thiol compounds cysteine and glutathione in leaves and seedlings of A. thaliana are compatible with a physiological role of H2O2 in regulating ABI2 activity. ABI2 is considered to exert negative regulation on ABA action. Thus, transient inactivation of this protein phosphatase by H2O2 would allow or enhance the ABA-dependent signalling process. In conclusion, ABI2 represents a likely target for redox-regulation of a hormonal signalling pathway in higher plants.
