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bioRxiv · 10.1101/2024.07.05.602132

MAP4K1 and MAP4K2 regulate ABA-induced and Ca2+-mediated stomatal closure in Arabidopsis

Yamashita, K.·Katagiri, S.·Takase, H.·Li, Y.·Otoguro, A.·Kamiyama, Y.·Yamauchi, S.·Takemiya, A.·Mori, I. C.·Umezawa, T.
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Abstract

Abscisic acid (ABA)-induced stomatal closure limits water loss from plants under drought stress. To investigate signaling pathways involved in stomatal closure, we performed a phosphoproteomic analysis of ABA-treated Arabidopsis guard cell protoplasts (GCPs). From this analysis, we discovered that MITOGEN-ACTIVATED PROTEIN 4 KINASE 1 (MAP4K1) is phosphorylated in response to ABA. Subsequent biochemical assays showed that Ser-479 of MAP4K1 is directly phosphorylated by SRK2E (OST1/SnRK2.6), a protein kinase that plays a central role in ABA-induced responses. Mutational analyses of MAP4K1, as well as closely related MAP4K2, revealed that both kinases positively regulate ABA-induced stomatal closure, and that Ser-479 of MAP4K1 was required for this phenotype. In map4k1map4k2, stomatal closure was induced by exogenous Ca2+ but not H2O2. Furthermore, electrophysiology experiments showed that MAP4K1/2 are required for ABA-dependent activation of Ca2+-permeable channels in GCPs. Together, our results indicate that SnRK2 and MAP4K1/2 function as a signaling module to regulate Ca2+-mediated stomatal closure.

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Yamashita, K., Katagiri, S., Takase, H., Li, Y., Otoguro, A., Kamiyama, Y., Yamauchi, S., Takemiya, A., Mori, I. C., Umezawa, T.. 2024-07-05. MAP4K1 and MAP4K2 regulate ABA-induced and Ca2+-mediated stomatal closure in Arabidopsis. https://doi.org/10.1101/2024.07.05.602132

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