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Shinri Tamura - One of the best experts on this subject based on the ideXlab platform.
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N-Myristoylation is essential for Protein Phosphatases PPM1A and PPM1B to dephosphorylate their physiological substrates in cells.
The Biochemical journal, 2013Co-Authors: Toko Chida, Masakatsu Ando, Tasuku Matsuki, Yutaro Masu, Yuko Nagaura, Teruko Takano-yamamoto, Shinri Tamura, Takayasu KobayashiAbstract:PPM [metal-dependent Protein Phosphatase, formerly called PP2c (Protein Phosphatase 2c)] family members play essential roles in regulating a variety of signalling pathways. While searching for Protein Phosphatase(s) that act on AMPK (AMP-activated Protein kinase), we found that PPM1A and PPM1B are N-myristoylated and that this modification is essential for their ability to dephosphorylate the α subunit of AMPK (AMPKα) in cells. N-Myristoylation was also required for two other functions of PPM1A and PPM1B in cells. Although a non-myristoylated mutation (G2A) of PPM1A and PPM1B prevented membrane association, this relocalization did not likely cause the decreased activity towards AMPKα. In in vitro experiments, the G2A mutants exhibited reduced activities towards AMPKα, but much higher specific activity against an artificial substrate, PNPP (p-nitrophenyl phosphate), compared with the wild-type counterparts. Taken together, the results of the present study suggest that N-myristoylation of PPM1A and PPM1B plays a key role in recognition of their physiological substrates in cells.
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allosteric activation of Protein Phosphatase 2c by d chiro inositol galactosamine a putative mediator mimetic of insulin action
Biochemistry, 2005Co-Authors: David L Brautigan, Michael F Brown, S Grindrod, Gary M Chinigo, A Kruszewski, Stephen M Lukasik, John H Bushweller, M Horal, S Keller, Shinri TamuraAbstract:Insulin-stimulated glucose disposal in skeletal muscle proceeds predominantly through a nonoxidative pathway with glycogen synthase as a rate-limiting enzyme, yet the mechanisms for insulin activation of glycogen synthase are not understood despite years of investigation. Isolation of putative insulin second messengers from beef liver yielded a pseudo-disaccharide consisting of pinitol (3-O-methyl-d-chiro-inositol) β-1,4 linked to galactosamine chelated with Mn2+ (called INS2). Here we show that chemically synthesized INS2 has biological activity that significantly enhances insulin reduction of hyperglycemia in streptozotocin diabetic rats. We used computer modeling to dock INS2 onto the known three-dimensional crystal structure of Protein Phosphatase 2c (PP2c). Modeling and FlexX/CScore energy minimization predicted a unique favorable site on PP2c for INS2 in a surface cleft adjacent to the catalytic center. Binding of INS2 is predicted to involve formation of multiple H-bonds, including one with residue...
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allosteric activation of Protein Phosphatase 2c by d chiro inositol galactosamine a putative mediator mimetic of insulin action
Biochemistry, 2005Co-Authors: David L Brautigan, S Grindrod, Gary M Chinigo, A Kruszewski, Stephen M Lukasik, John H Bushweller, M Horal, S Keller, Milton L Brown, Shinri TamuraAbstract:Insulin-stimulated glucose disposal in skeletal muscle proceeds predominantly through a nonoxidative pathway with glycogen synthase as a rate-limiting enzyme, yet the mechanisms for insulin activation of glycogen synthase are not understood despite years of investigation. Isolation of putative insulin second messengers from beef liver yielded a pseudo-disaccharide consisting of pinitol (3-O-methyl-d-chiro-inositol) beta-1,4 linked to galactosamine chelated with Mn(2+) (called INS2). Here we show that chemically synthesized INS2 has biological activity that significantly enhances insulin reduction of hyperglycemia in streptozotocin diabetic rats. We used computer modeling to dock INS2 onto the known three-dimensional crystal structure of Protein Phosphatase 2c (PP2c). Modeling and FlexX/CScore energy minimization predicted a unique favorable site on PP2c for INS2 in a surface cleft adjacent to the catalytic center. Binding of INS2 is predicted to involve formation of multiple H-bonds, including one with residue Asp163. Wild-type PP2c activity assayed with a phosphopeptide substrate was potently stimulated in a dose-dependent manner by INS2. In contrast, the D163A mutant of PP2c was not activated by INS2. The D163A mutant and wild-type PP2c in the absence of INS2 had the same Mn(2+)-dependent Phosphatase activity with p-nitrophenyl phosphate as a substrate, showing that this mutation did not disrupt the catalytic site. We propose that INS2 allosterically activates PP2c, fulfilling the role of a putative mediator mimetic of insulin signaling to promote Protein dephosphorylation and metabolic responses.
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molecular cloning of pp2cη a novel member of the Protein Phosphatase 2c family
Biochimica et Biophysica Acta, 2003Co-Authors: Ken Ichiro Komaki, Takayasu Kobayashi, Motoko Ohnishi, Koji Katsura, Masato Sasaki, Makoto Watanabe, Shinri TamuraAbstract:We have cloned a novel member of the mouse Protein Phosphatase 2c family, PP2ceta. Sequence analysis suggests that PP2ceta, PP2czeta and NERPP-2c constitute a unique subgroup of the PP2c family. PP2ceta had extremely low activity against alpha-casein compared with PP2calpha and was localized mainly in cell nuclei, suggesting that PP2ceta dephosphorylates a unique nuclear Protein(s) in the cells.
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regulation of the interleukin 1 induced signaling pathways by a novel member of the Protein Phosphatase 2c family pp2ce
Journal of Biological Chemistry, 2003Co-Authors: Koji Katsura, Takayasu Kobayashi, Ken Ichiro Komaki, Jun Ninomiyatsuji, Kunihiro Matsumoto, Hisayuki Nomiyama, Shinri TamuraAbstract:Abstract Although TAK1 signaling plays essential roles in eliciting cellular responses to interleukin-1 (IL-1), a proinflammatory cytokine, how the IL-1-TAK1 signaling pathway is positively and negatively regulated remains poorly understood. In this study, we investigated the possible role of a novel Protein Phosphatase 2c (PP2c) family member, PP2ce, in the regulation of the IL-1-TAK1 signaling pathway. PP2ce was composed of 303 amino acids, and the overall similarity of amino acid sequence between PP2ce and PP2cα was found to be 26%. Ectopic expression of PP2ce inhibited the IL-1- and TAK1-induced activation of mitogen-activated Protein kinase kinase 4 (MKK4)-c-Jun N-terminal kinase or MKK3-p38 signaling pathway. PP2ce dephosphorylated TAK1 in vitro. Co-immunoprecipitation experiments indicated that PP2ce associates stably with TAK1 and attenuates the binding of TAK1 to MKK4 or MKK6. Ectopic expression of a Phosphatase-negative mutant of PP2ce, PP2ce(D/A), which acted as a dominant negative form, enhanced both the association between TAK1 and MKK4 or MKK6 and the TAK1-induced activation of an AP-1 reporter gene. The association between PP2ce and TAK1 was transiently suppressed by IL-1 treatment of the cells. Taken together, these results suggest that, in the absence of IL-1-induced signal, PP2ce contributes to keeping the TAK1 signaling pathway in an inactive state by associating with and dephosphorylating TAK1.
Pedro L Rodriguez - One of the best experts on this subject based on the ideXlab platform.
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ubiquitylation of aba receptors and Protein Phosphatase 2c coreceptors to modulate aba signaling and stress response
International Journal of Molecular Sciences, 2021Co-Authors: Alberto Coego, Jose Julian, Jorge Lozanojuste, Gaston A Pizzio, Abdulwahed F Alrefaei, Pedro L RodriguezAbstract:Post-translational modifications play a fundamental role in regulating Protein function and stability. In particular, Protein ubiquitylation is a multifaceted modification involved in numerous aspects of plant biology. Landmark studies connected the ATP-dependent ubiquitylation of substrates to their degradation by the 26S proteasome; however, nonproteolytic functions of the ubiquitin (Ub) code are also crucial to regulate Protein interactions, activity, and localization. Regarding proteolytic functions of Ub, Lys-48-linked branched chains are the most common chain type for proteasomal degradation, whereas promotion of endocytosis and vacuolar degradation is triggered through monoubiquitylation or Lys63-linked chains introduced in integral or peripheral plasma membrane Proteins. Hormone signaling relies on regulated Protein turnover, and specifically the half-life of ABA signaling components is regulated both through the ubiquitin-26S proteasome system and the endocytic/vacuolar degradation pathway. E3 Ub ligases have been reported that target different ABA signaling core components, i.e., ABA receptors, PP2cs, SnRK2s, and ABFs/ABI5 transcription factors. In this review, we focused specifically on the ubiquitylation of ABA receptors and PP2c coreceptors, as well as other post-translational modifications of ABA receptors (nitration and phosphorylation) that result in their ubiquitination and degradation.
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stress induced Protein Phosphatase 2c is a negative regulator of a mitogen activated Protein kinase
Journal of Biological Chemistry, 2003Co-Authors: Irute Meskiene, Pedro L Rodriguez, Emmanuel Baudouin, Alois Schweighofer, Aneta Liwosz, Claudia Jonak, Heinrich Jelinek, Heribert HirtAbstract:Abstract Protein Phosphatases of type 2c (PP2cs) play important roles in eukaryotic signal transduction. In contrast to other eukaryotes, plants such as Arabidopsis have an unusually large group of 69 different PP2c genes. At present, little is known about the functions and substrates of plant PP2cs. We have previously shown that MP2c, a wound-induced alfalfa PP2c, is a negative regulator of mitogen-activated Protein kinase (MAPK) pathways in yeast and plants. In this report, we provide evidence that alfalfa salt stress-inducible MAPK (SIMK) and stress-activated MAPK (SAMK) are activated by wounding and that MP2c is a MAPK Phosphatase that directly inactivates SIMK but not the wound-activated MAPK, SAMK. SIMK is inactivated through threonine dephosphorylation of the pTEpY motif, which is essential for MAPK activity. Mutant analysis indicated that inactivation of SIMK depends on the catalytic activity of MP2c. A comparison of MP2c with two other PP2cs, ABI2 and AtP2cHA, revealed that although all three Phosphatases have similar activities toward casein as a substrate, only MP2c is able to dephosphorylate and inactivate SIMK. In agreement with the notion that MP2c interacts directly with SIMK, the MAPK was identified as an interacting partner of MP2c in a yeast two-hybrid screen. MP2c can be immunoprecipitated with SIMK in a complex in vivo and shows direct binding to SIMK in vitro in Protein interaction assays. Wound-induced MP2c expression correlates with the time window when SIMK is inactivated, corroborating the notion that MP2c is involved in resetting the SIMK signaling pathway.
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a new Protein Phosphatase 2c fspp2c1 induced by abscisic acid is specifically expressed in dormant beechnut seeds
Plant Physiology, 2001Co-Authors: Oscar Lorenzo, Pedro L Rodriguez, Dolores Rodriguez, Gregorio Nicolas, Carlos NicolasAbstract:An abscisic acid (ABA)-induced cDNA fragment encoding a putative Protein Phosphatase 2c (PP2c) was obtained by means of differential reverse transcriptase-polymerase chain reaction approach. The full-length clone was isolated from a cDNA library constructed using mRNA from ABA-treated beechnut ( Fagus sylvatica ) seeds. This clone presents all the features of plant type PP2c and exhibits homology to members of this family such as AthPP2cA (61%), ABI1 (48%), or ABI2 (47%), therefore it was named FsPP2c1. The expression of FsPP2c1 is detected in dormant seeds and increases after ABA treatment, when seeds are maintained dormant, but it decreases and tends to disappear when dormancy is being released by stratification or under gibberellic acid treatment. Moreover, drought stress seems to have no effect on FsPP2c1 transcript accumulation. The FsPP2c1 transcript expression is tissue specific and was found to accumulate in ABA-treated seeds rather than in other ABA-treated vegetative tissues examined. These results suggest that the corresponding Protein could be related to ABA-induced seed dormancy. By expressing FsPP2c1 in Escherichia coli as a histidine tag fusion Protein, we have obtained direct biochemical evidence supporting Mg 2+ -dependent Phosphatase activity of this Protein.
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Protein Phosphatase 2c (PP2c) function in higher plants
Plant Molecular Biology, 1998Co-Authors: Pedro L RodriguezAbstract:In the past few years, molecular cloning studies have revealed the primary structure of plant Protein serine/threonine Phosphatases. Two structurally distinct families, the PP1/PP2A family and the PP2c family, are present in plants as well as in animals. This review will focus on the plant PP2c family of Protein Phosphatases. Biochemical and molecular genetic studies in Arabidopsis have identified PP2c enzymes as key players in plant signal transduction processes. For instance, the ABI1/ABI2 PP2cs are central components in abscisic acid (ABA) signal transduction. Arabidopsis mutants containing a single amino acid exchange in ABI1 or ABI2 show a reduced response to ABA. Another member of the PP2c family, kinase-associated Protein Phosphatase (KAPP), appears to be an important element in some receptor-like kinase (RLK) signalling pathways. Finally, an alfalfa PP2c acts as a negative regulator of a plant mitogen-activated Protein kinase (MAPK) pathway. Thus, the plant PP2cs function as regulators of various signal transduction pathways.
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abi2 a second Protein Phosphatase 2c involved in abscisic acid signal transduction in arabidopsis
FEBS Letters, 1998Co-Authors: Pedro L Rodriguez, Gregor Benning, Erwin GrillAbstract:The abi2-1 (abscisic acid insensitive) mutant of Arabidopsis thaliana shows abscisic acid (ABA) insensitivity with respect to seed germination and vegetative ABA responses. We identified the ABI2 gene by a combination of positional mapping and homology to ABI1. The ABI2 Protein shows 80% amino acid sequence identity to ABI1, a Protein Phosphatase 2c (PP2c) involved in ABA signaling. The mutation that confers the abi2-1 phenotype is equivalent to the mutation previously identified in abi1-1 and the resulting Gly168Asp abi2 Protein shows a reduced PP2c activity. Thus, a pair of highly homologous PP2cs regulate ABA signaling.
Erwin Grill - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen peroxide is a regulator of ABI1, a Protein Phosphatase 2c from Arabidopsis
FEBS letters, 2001Co-Authors: Michael Meinhard, Erwin GrillAbstract:Abstract Protein Phosphatases 2c (PP2cs) exhibit diverse regulatory functions in signalling pathways of animals, yeast and plants. ABI1 is a PP2c of Arabidopsis that exerts negative control on signalling of the phytohormone abscisic acid (ABA). Characterisation of the redox sensitivity of ABI1 revealed a strong enzymatic inactivation by hydrogen peroxide (H 2 O 2 ) which has recently been implicated as a secondary messenger of ABA signalling. H 2 O 2 reversibly inhibited ABI1 activity in vitro with an IC 50 of approximately 140 μM in the presence of physiological concentrations of glutathione. In addition, ABI1 was highly susceptible to inactivation by phenylarsine oxide (IC 50 =3–4 μM) indicative for the facile oxidation of vicinal cysteine residues. Thus, H 2 O 2 generated during ABA signalling seems to inactivate the negative regulator of the ABA response.
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abi2 a second Protein Phosphatase 2c involved in abscisic acid signal transduction in arabidopsis
FEBS Letters, 1998Co-Authors: Pedro L Rodriguez, Gregor Benning, Erwin GrillAbstract:The abi2-1 (abscisic acid insensitive) mutant of Arabidopsis thaliana shows abscisic acid (ABA) insensitivity with respect to seed germination and vegetative ABA responses. We identified the ABI2 gene by a combination of positional mapping and homology to ABI1. The ABI2 Protein shows 80% amino acid sequence identity to ABI1, a Protein Phosphatase 2c (PP2c) involved in ABA signaling. The mutation that confers the abi2-1 phenotype is equivalent to the mutation previously identified in abi1-1 and the resulting Gly168Asp abi2 Protein shows a reduced PP2c activity. Thus, a pair of highly homologous PP2cs regulate ABA signaling.
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Molecular cloning in Arabidopsis thaliana of a new Protein Phosphatase 2c (PP2c) with homology to ABI1 and ABI2
Plant molecular biology, 1998Co-Authors: Pedro L Rodriguez, Martin P. Leube, Erwin GrillAbstract:We report the cloning of both the cDNA and the corresponding genomic sequence of a new PP2c from Arabidopsis thaliana, named AtP2c-HA (for homology to ABI1/ABI2). The AtP2c-HA cDNA contains an open reading frame of 1536 bp and encodes a putative Protein of 511 amino acids with a predicted molecular mass of 55.7 kDa. The AtP2c-HA Protein is composed of two domains, a C-terminal PP2c catalytic domain and a N-terminal extension of ca. 180 amino acid residues. The deduced amino acid sequence is 55% and 54% identical to ABI1 and ABI2, respectively. Comparison of the genomic structure of the ABI1, ABI2 and AtP2c-HA genes suggests that they belong to a multigene family. The expression of the AtP2c-HA gene is up-regulated by abscisic acid (ABA) treatment.
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a Protein Phosphatase 2c involved in aba signal transduction in arabidopsis thaliana
Science, 1994Co-Authors: Knut Meyer, Martin P. Leube, Erwin GrillAbstract:The plant hormone abscisic acid (ABA) mediates various responses such as stomatal closure, the maintenance of seed dormancy, and the inhibition of plant growth. All three responses are affected in the ABA-insensitive mutant abi1 of Arabidopsis thaliana, suggesting that an early step in the signaling of ABA is controlled by the ABI1 locus. The ABI1 gene was cloned by chromosome walking, and a missense mutation was identified in the structural gene of the abi1 mutant. The ABI1 gene encodes a Protein with high similarity to Protein serine or threonine Phosphatases of type 2c with the novel feature of a putative Ca2+ binding site. Thus, the control of the phosphorylation state of cell signaling components by the ABI1 product could mediate pleiotropic hormone responses.
Jerome Giraudat - 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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ABI1 Protein Phosphatase 2c Is a Negative Regulator of Abscisic Acid Signaling
The Plant cell, 1999Co-Authors: Françoise Gosti, Nathalie Beaudoin, Carine Serizet, Alex Webb, Nicole Vartanian, Jerome GiraudatAbstract:The plant hormone abscisic acid (ABA) is a key regulator of seed maturation and germination and mediates adaptive responses to environmental stress. In Arabidopsis, the ABI1 gene encodes a member of the 2c class of Protein serine/ threonine Phosphatases (PP2c), and the abi1-1 mutation markedly reduces ABA responsiveness in both seeds and vegetative tissues. However, this mutation is dominant and has been the only mutant allele available for the ABI1 gene. Hence, it remained unclear whether ABI1 contributes to ABA signaling, and in case ABI1 does regulate ABA responsiveness, whether it is a positive or negative regulator of ABA action. In this study, we isolated seven novel alleles of the ABI1 gene as intragenic revertants of the abi1-1 mutant. In contrast to the ABA-resistant abi1-1 mutant, these revertants were more sensitive than the wild type to the inhibition of seed germination and seedling root growth by applied ABA. They also displayed increases in seed dormancy and drought adaptive responses that are indicative of a higher responsiveness to endogenous ABA. The revertant alleles were recessive to the wild-type ABI1 allele in enhancing ABA sensitivity, indicating that this ABA-supersensitive phenotype results from a loss of function in ABI1. The seven suppressor mutations are missense mutations in conserved regions of the PP2c domain of ABI1, and each of the corresponding revertant alleles encodes an ABI1 Protein that lacked any detectable PP2c activity in an in vitro enzymatic assay. These results indicate that a loss of ABI1 PP2c activity leads to an enhanced responsiveness to ABA. Thus, the wild-type ABI1 Phosphatase is a negative regulator of ABA responses.
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the arabidopsis abscisic acid insensitive2 abi2 and abi1 genes encode homologous Protein Phosphatases 2c involved in abscisic acid signal transduction
The Plant Cell, 1997Co-Authors: Jeffrey Leung, S. Merlot, Jerome GiraudatAbstract:Abscisic acid (ABA) mediates seed maturation and adaptive responses to environmental stress. In Arabidopsis, the ABA-INSENSITIVE1 (ABI1) Protein Phosphatase 2c is required for proper ABA responsiveness both in seeds and in vegetative tissues. To determine whether the lack of recessive alleles at the corresponding locus could be explained by the existence of redundant genes, we initiated a search for ABI1 homologs. One such homolog turned out to be the ABI2 locus, whose abi2-1 mutation was previously known to decrease ABA sensitivity. Whereas abi1-1 is (semi)dominant, abi2-1 has been described as recessive and maternally controlled at the germination stage. Unexpectedly, the sequence of the abi2-1 mutation showed that it converts Gly-168 to Asp, which is precisely the same amino acid substitution found in abi1-1 and at the coincidental position within the ABI1 Phosphatase domain (Gly-180 to Asp). In vitro assays and functional complementation studies in yeast confirmed that the ABI2 Protein is an active Protein Phosphatase 2c and that the abi2-1 mutation reduced Phosphatase activity as well as affinity to Mg2+. Although a number of differences between the two mutants in adaptive responses to stress have been reported, quantitative comparisons of other major phenotypes showed that the effects of both abi1-1 and abi2-1 on these processes are nearly indistinguishable. Thus, the homologous ABI1 and ABI2 Phosphatases appear to assume partially redundant functions in ABA signaling, which may provide a mechanism to maintain informational homeostasis.
Kazuo Shinozaki - One of the best experts on this subject based on the ideXlab platform.
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type 2c Protein Phosphatases directly regulate abscisic acid activated Protein kinases in arabidopsis
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Taishi Umezawa, Takashi Hirayama, Naoyuki Sugiyama, Masahide Mizoguchi, Shimpei Hayashi, Fumiyoshi Myouga, Kazuko Yamaguchishinozaki, Yasushi Ishihama, Kazuo ShinozakiAbstract:Abscisic acid (ABA) signaling is important for stress responses and developmental processes in plants. A subgroup of Protein Phosphatase 2c (group A PP2c) or SNF1-related Protein kinase 2 (subclass III SnRK2) have been known as major negative or positive regulators of ABA signaling, respectively. Here, we demonstrate the physical and functional linkage between these two major signaling factors. Group A PP2cs interacted physically with SnRK2s in various combinations, and efficiently inactivated ABA-activated SnRK2s via dephosphorylation of multiple Ser/Thr residues in the activation loop. This step was suppressed by the RCAR/PYR ABA receptors in response to ABA. However the abi1–1 mutated PP2c did not respond to the receptors and constitutively inactivated SnRK2. Our results demonstrate that group A PP2cs act as ‘gatekeepers’ of subclass III SnRK2s, unraveling an important regulatory mechanism of ABA signaling.
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aba hypersensitive germination1 encodes a Protein Phosphatase 2c an essential component of abscisic acid signaling in arabidopsis seed
Plant Journal, 2007Co-Authors: Noriyuki Nishimura, Kazuo Shinozaki, Tomo Yoshida, Nobutaka Kitahata, Tadao Asami, Takashi HirayamaAbstract:*† Summary The phytohormone abscisic acid (ABA) regulates physiologically important stress and developmental responses in plants. To reveal the mechanism of response to ABA, we isolated several novel ABAhypersensitive Arabidopsis thaliana mutants, named ahg ( ABA-hypersensitive germination). ahg1-1 mutants showed hypersensitivity to ABA, NaCl, KCl, mannitol, glucose and sucrose during germination and postgermination growth, but did not display any significant phenotypes in adult plants. ahg1-1 seeds accumulated slightly more ABA before stratification and showed increased seed dormancy. Map-based cloning of AHG1 revealed that ahg1-1 has a nonsense mutation in a gene encoding a novel Protein Phosphatase 2c (PP2c). We previously showed that the ahg3-1 mutant has a point mutation in the AtPP2cA gene, which encodes another PP2c that has a major role in the ABA response in seeds (Yoshida et al., 2006b). The levels of AHG1 mRNA were higher in dry seeds and increased during late seed maturation – an expression pattern similar to that of ABI5. Transcriptome analysis revealed that, in ABA-treated germinating seeds, many seed-specific genes and ABAinducible genes were highly expressed in ahg1-1 and ahg3-1 mutants compared with the wild-type. Detailed analysis suggested differences between the functions of AHG1 and AHG3. Dozens of genes were expressed more strongly in the ahg1-1 mutant than in ahg3-1. Promoter–GUS analyses demonstrated both overlapping and distinct expression patterns in seed. In addition, the ahg1-1 ahg3-1 double mutant was more hypersensitive than either monogenic mutant. These results suggest that AHG1 has specific functions in seed development and germination, shared partly with AHG3.
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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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aba hypersensitive germination3 encodes a Protein Phosphatase 2c atpp2ca that strongly regulates abscisic acid signaling during germination among arabidopsis Protein Phosphatase 2cs
Plant Physiology, 2005Co-Authors: Tomo Yoshida, Kazuo Shinozaki, Noriyuki Nishimura, Nobutaka Kitahata, Tadao Asami, Takashi Kuromori, Takuya Ito, Takashi HirayamaAbstract:The phytohormone abscisic acid (ABA) regulates physiologically important developmental processes and stress responses. Previously, we reported on Arabidopsis (Arabidopsis thaliana) L. Heynh. ahg mutants, which are hypersensitive to ABA during germination and early growth. Among them, ABA-hypersensitive germination3 (ahg3) showed the strongest ABA hypersensitivity. In this study, we found that the AHG3 gene is identical to AtPP2cA, which encodes a Protein Phosphatase 2c (PP2c). Although AtPP2cA has been reported to be involved in the ABA response on the basis of results obtained by reverse-genetics approaches, its physiological relevance in the ABA response has not been clarified yet. We demonstrate in vitro and in vivo that the ahg3-1 missense mutation causes the loss of PP2c activity, providing concrete confirmation that this PP2c functions as a negative regulator in ABA signaling. Furthermore, we compared the effects of disruption mutations of eight structurally related PP2c genes of Arabidopsis, including ABI1, ABI2, HAB1, and HAB2, and found that the disruptant mutant of AHG3/AtPP2cA had the strongest ABA hypersensitivity during germination, but it did not display any significant phenotypes in adult plants. Northern-blot analysis clearly showed that AHG3/AtPP2cA is the most active among those PP2c genes in seeds. These results suggest that AHG3/AtPP2cA plays a major role among PP2cs in the ABA response in seeds and that the functions of those PP2cs overlap, but their unique tissue- or development-specific expression confers distinct and indispensable physiological functions in the ABA response.
