Pathway Reconstitution of Abscisic Acid Hormone Activation of SLAC1 Anion Channels via Novel ABA Signaling Protein Kinase

Stomatal pore apertures are narrowing globally due to the continuing rise in atmospheric [CO2]. CO2 elevation and the plant hormone abscisic acid (ABA) both induce rapid stomatal closure. However, the underlying signal transduction mechanisms for CO2/ABA interaction remain unclear. Two models have been considered: (i) CO2 elevation enhances ABA concentrations and/or early ABA signaling in guard cells to induce stomatal closure and (ii) CO2 signaling merges with ABA at OST1/SnRK2.6 protein kinase activation. Here we use genetics, ABA-reporter imaging, stomatal conductance, patch clamp, and biochemical analyses to investigate these models. The strong ABA biosynthesis mutants nced3/nced5 and aba2-1 remain responsive to CO2 elevation. Rapid CO2-triggered stomatal closure in PYR/RCAR ABA receptor quadruple and hextuple mutants is not disrupted but delayed. Time-resolved ABA concentration monitoring in guard cells using a FRET-based ABA-reporter, ABAleon2.15, and ABA reporter gene assays suggest that CO2 elevation does not trigger [ABA] increases in guard cells, in contrast to control ABA exposures. Moreover, CO2 activates guard cell S-type anion channels in nced3/nced5 and ABA receptor hextuple mutants. Unexpectedly, in-gel protein kinase assays show that unlike ABA, elevated CO2 does not activate OST1/SnRK2 kinases in guard cells. The present study points to a model in which rapid CO2 signal transduction leading to stomatal closure occurs via an ABA-independent pathway downstream of OST1/SnRK2.6. Basal ABA signaling and OST1/SnRK2 activity are required to facilitate the stomatal response to elevated CO2. These findings provide insights into the interaction between CO2/ABA signal transduction in light of the continuing rise in atmospheric [CO2].

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Rice Calcium/Calmodulin-Dependent Protein Kinase Directly Phosphorylates a Mitogen-Activated Protein Kinase Kinase to Regulate Abscisic Acid Responses

10.1101/2020.10.21.348805 ◽

2020 ◽

Author(s):

Min Chen ◽

Lan Ni ◽

Jing Chen ◽

Manman Sun ◽

Caihua Qin ◽

...

Keyword(s):

Abscisic Acid ◽

Protein Kinase ◽

Mitogen Activated Protein Kinase ◽

Activation Loop ◽

Aba Signaling ◽

Dependent Protein Kinase ◽

N Terminus ◽

Mitogen Activated Protein ◽

Dependent Protein ◽

Direct Target

ABSTRACTCa2+/calmodulin (CaM)-dependent protein kinase (CCaMK) is an important positive regulator of abscisic acid (ABA) and abiotic stress signaling in plants and is believed to act upstream of mitogen-activated protein kinase (MAPK) in ABA signaling. However, it is unclear how CCaMK activates MAPK in ABA signaling. Here, we show that OsDMI3, a rice (Oryza sativa) CCaMK, directly interacts with and phosphorylates OsMKK1, a MAPK kinase (MKK) in rice, in vitro and in vivo. OsDMI3 was found to directly phosphorylate Thr-25 in the N-terminus of OsMKK1, and this Thr-25 phosphorylation is OsDMI3-specific in ABA signaling. The activation of OsMKK1 and its downstream kinase OsMPK1 is dependent on Thr-25 phosphorylation of OsMKK1 in ABA signaling. Moreover, ABA treatment also induces the phosphorylation in the activation loop of OsMKK1, and the two phosphorylations in the N-terminus and in the activation loop are independent. Further analyses revealed that OsDMI3-mediated phosphorylation of OsMKK1 positively regulates ABA responses in seed germination, root growth, and tolerance to both water stress and oxidative stress. Our results indicate that OsMKK1 is a direct target of OsDMI3, and OsDMI3-mediated phosphorylation of OsMKK1 plays an important role in the activation of MAPK cascade and ABA signaling.One-sentence summaryOsMKK1 is a direct target of OsDMI3, and OsDMI3-mediated phosphorylation of OsMKK1 plays an important role in the activation of MAPK cascade and ABA signaling.The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantcell.org) is: Mingyi Jiang ([email protected])

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Arabidopsis group C Raf-like protein kinases negatively regulate abscisic acid signaling and are direct substrates of SnRK2

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2100073118 ◽

2021 ◽

Vol 118 (30) ◽

pp. e2100073118

Author(s):

Yoshiaki Kamiyama ◽

Misaki Hirotani ◽

Shinnosuke Ishikawa ◽

Fuko Minegishi ◽

Sotaro Katagiri ◽

...

Keyword(s):

Abscisic Acid ◽

Protein Kinase ◽

Stress Responses ◽

Reverse Genetic ◽

Optimal Conditions ◽

Aba Signaling ◽

Wild Type ◽

In Planta ◽

Dependent Inhibition ◽

Biochemical Analyses

The phytohormone abscisic acid (ABA) plays a major role in abiotic stress responses in plants, and subclass III SNF1-related protein kinase 2 (SnRK2) kinases mediate ABA signaling. In this study, we identified Raf36, a group C Raf-like protein kinase in Arabidopsis, as a protein that interacts with multiple SnRK2s. A series of reverse genetic and biochemical analyses revealed that 1) Raf36 negatively regulates ABA responses during postgermination growth, 2) the N terminus of Raf36 is directly phosphorylated by SnRK2s, and 3) Raf36 degradation is enhanced in response to ABA. In addition, Raf22, another C-type Raf-like kinase, functions partially redundantly with Raf36 to regulate ABA responses. A comparative phosphoproteomic analysis of ABA-induced responses of wild-type and raf22raf36-1 plants identified proteins that are phosphorylated downstream of Raf36 and Raf22 in planta. Together, these results support a model in which Raf36/Raf22 function mainly under optimal conditions to suppress ABA responses, whereas in response to ABA, the SnRK2 module promotes Raf36 degradation as a means of alleviating Raf36-dependent inhibition and allowing for heightened ABA signaling to occur.

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SNF1-related protein kinase 2 directly regulate group C Raf-like protein kinases in abscisic acid signaling

10.1101/2020.02.04.933978 ◽

2020 ◽

Cited By ~ 1

Author(s):

Yoshiaki Kamiyama ◽

Misaki Hirotani ◽

Shinnosuke Ishikawa ◽

Fuko Minegishi ◽

Sotaro Katagiri ◽

...

Keyword(s):

Abscisic Acid ◽

Protein Kinase ◽

Stress Responses ◽

Reverse Genetic ◽

Aba Signaling ◽

Related Protein ◽

Wild Type ◽

In Planta ◽

Interacting Protein ◽

Biochemical Analyses

ABSTRUCTA phytohormone abscisic acid (ABA) has a major role in abiotic stress responses in plants, and subclass III SNF1-related protein kinase 2 (SnRK2) mediates ABA signaling. In this study, we identified Raf36, a group C Raf-like protein kinase in Arabidopsis, as an interacting protein with SnRK2. A series of reverse genetic and biochemical analyses revealed that Raf36 negatively regulates ABA responses and is directly phosphorylated by SnRK2s. In addition, we found that Raf22, another C-type Raf-like kinase, functions partially redundantly with Raf36 to regulate ABA responses. Comparative phosphoproteomic analysis using Arabidopsis wild-type and raf22raf36-1 plants identified proteins that are phosphorylated downstream of Raf36 and Raf22 in planta. Together, these results reveal a novel subsection of ABA-responsive phosphosignaling pathways branching from SnRK2.

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Rice calcium/calmodulin-dependent protein kinase directly phosphorylates a mitogen-activated protein kinase kinase to regulate abscisic acid responses

The Plant Cell ◽

10.1093/plcell/koab071 ◽

2021 ◽

Author(s):

Min Chen ◽

Lan Ni ◽

Jing Chen ◽

Manman Sun ◽

Caihua Qin ◽

...

Keyword(s):

Abscisic Acid ◽

Protein Kinase ◽

Mitogen Activated Protein Kinase ◽

Activation Loop ◽

Aba Signaling ◽

Dependent Protein Kinase ◽

N Terminus ◽

Mitogen Activated Protein ◽

Dependent Protein

Abstract Ca2+/calmodulin (CaM)-dependent protein kinase (CCaMK) is an important positive regulator of abscisic acid (ABA) and abiotic stress signaling in plants and is believed to act upstream of mitogen-activated protein kinase (MAPK) in ABA signaling. However, it is unclear how CCaMK activates MAPK in ABA signaling. Here, we show that OsDMI3, a rice (Oryza sativa) CCaMK, directly interacts with and phosphorylates OsMKK1, a MAPK kinase (MKK) in rice, in vitro and in vivo. OsDMI3 was found to directly phosphorylate Thr-25 in the N-terminus of OsMKK1, and this Thr-25 phosphorylation is OsDMI3-specific in ABA signaling. The activation of OsMKK1 and its downstream kinase OsMPK1 is dependent on Thr-25 phosphorylation of OsMKK1 in ABA signaling. Moreover, ABA treatment induces phosphorylation in the activation loop of OsMKK1, and the two phosphorylations, in the N-terminus and in the activation loop, are independent. Further analyses revealed that OsDMI3-mediated phosphorylation of OsMKK1 positively regulates ABA responses in seed germination, root growth, and tolerance to both water stress and oxidative stress. Our results indicate that OsMKK1 is a direct target of OsDMI3, and OsDMI3-mediated phosphorylation of OsMKK1 plays an important role in activating the MAPK cascade and ABA signaling.

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Protein Kinase Cascade Involved in Rapid ABA-signaling in Guard Cells of Vicia faba

Zeitschrift für Naturforschung C ◽

10.1515/znc-2005-9-1017 ◽

2005 ◽

Vol 60 (9-10) ◽

pp. 769-773 ◽

Cited By ~ 3

Author(s):

Takuya Furuichi ◽

Izumi C. Mori ◽

Shoshi Muto

Keyword(s):

Abscisic Acid ◽

Protein Kinase ◽

Stress Responses ◽

Guard Cells ◽

Aba Signaling ◽

Carboxy Terminus ◽

Mrna Binding Protein ◽

Kinase Cascade ◽

Mrna Binding ◽

Protein Kinase Cascade

Abstract Protein kinases are involved in signal transduction for environmental stress responses. In response to drought and salinity, a 48-kDa protein kinase (AAPK; abscisic acid-activated protein kinase (AAPK) in guard cells is activated by abscisic acid (ABA) and phosphorylates several targets such as the carboxy-terminus of inward-rectifying K+ channel and heterogeneous mRNA binding protein to adopt to the changing environment. The AAPK expressed specifically in guard cells, and recombinant AAPK was phosphorylated only with the extract from ABA-treated guard cells but not from untreated cells. This indicates the presence of an AAPK kinase (AAPKK), which is activated by ABA and phosphorylates AAPK preceding the activation of AAPK. Both AAPK and AAPKK are involved in the protein kinase cascade for the rapid ABA-signaling.

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Nitric oxide negatively regulates abscisic acid signaling in guard cells by S-nitrosylation of OST1

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1423481112 ◽

2014 ◽

Vol 112 (2) ◽

pp. 613-618 ◽

Cited By ~ 178

Author(s):

Pengcheng Wang ◽

Yanyan Du ◽

Yueh-Ju Hou ◽

Yang Zhao ◽

Chuan-Chih Hsu ◽

...

Keyword(s):

Nitric Oxide ◽

Abscisic Acid ◽

Protein Kinase ◽

Stomatal Closure ◽

Guard Cells ◽

Cysteine Residue ◽

Aba Signaling ◽

Related Protein ◽

Abscisic Acid Signaling ◽

Evolutionarily Conserved

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.

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