Identification and characterization of an ABA-activated MAP kinase cascade in Arabidopsis thaliana

Abstract
Summary Abscisic acid (ABA) is a major phytohormone involved in important stress-related and developmental plant processes. Recent phosphoproteomic analyses revealed a large set of ABA-triggered phosphoproteins as putative mitogen-activated protein kinase (MAPK) targets, although the evidence for MAPKs involved in ABA signalling is still scarce. Here, we identified and reconstituted in vivo a complete ABA-activated MAPK cascade, composed of the MAP3Ks MAP3K17/18, the MAP2K MKK3 and the four C group MAPKs MPK1/2/7/14. In planta, we show that ABA activation of MPK7 is blocked in mkk3-1 and map3k17mapk3k18 plants. Coherently, both mutants exhibit hypersensitivity to ABA and altered expression of a set of ABA-dependent genes. A genetic analysis further reveals that this MAPK cascade is activated by the PYR/PYL/RCAR-SnRK2-PP2C ABA core signalling module through protein synthesis of the MAP3Ks, unveiling an atypical mechanism for MAPK activation in eukaryotes. Our work provides evidence for a role of an ABA-induced MAPK pathway in plant stress signalling. Significance Statement We report in this article the identification of a complete MAPK module, composed of MAP3K17/18, MKK3 and MPK1/2/7/14, which is activated by ABA through the ABA core signalling complex. We showed that the activation of this module requires the MAP3K protein synthesis which occurs after hours of stress treatment, suggesting that the pathway is involved in a delayed wave of cellular responses to ABA and drought. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

Citation
Danquah, A., de Zélicourt, A., Boudsocq, M., Neubauer, J., Frei dit Frey, N., Leonhardt, N., … Colcombet, J. (2015). Identification and characterization of an ABA-activated MAP kinase cascade inArabidopsis thaliana. The Plant Journal, 82(2), 232–244. doi:10.1111/tpj.12808

Acknowledgements
We thank Sean Cutler, Sylvain Merlot and Jane Parker for kindly providing hab1G246D line, pyr1pyl1pyl2pyl4 mutant and pEXCS-GW-mYFP-nls plasmid, respectively. This work was supported by the Institut National de Recherche Agronomique and the Agence Nationale de la Recherche. AD was supported by the Ghanaian Ministry of Education.

Publisher
Wiley

Journal
The Plant Journal

DOI
10.1111/tpj.12808

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