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SUMO enables substrate selectivity by mitogen-activated protein kinases to regulate immunity in plants

Verma, Vivek and Srivastava, Anjil K. and Gough, Catherine and Campanaro, Alberto and Srivastava, Moumita and Morrell, Rebecca and Joyce, Joshua and Bailey, Mark and Zhang, Cunjin and Krysan, Patrick J. and Sadanandom, Ari (2021) 'SUMO enables substrate selectivity by mitogen-activated protein kinases to regulate immunity in plants.', Proceedings of the National Academy of Sciences, 118 (10). e2021351118.


The versatility of mitogen-activated protein kinases (MAPKs) in translating exogenous and endogenous stimuli into appropriate cellular responses depends on its substrate specificity. In animals, several mechanisms have been proposed about how MAPKs maintain specificity to regulate distinct functional pathways. However, little is known of mechanisms that enable substrate selectivity in plant MAPKs. Small ubiquitin-like modifier (SUMO), a posttranslational modification system, plays an important role in plant development and defense by rapid reprogramming of cellular events. In this study we identified a functional SUMO interaction motif (SIM) in Arabidopsis MPK3 and MPK6 that reveals a mechanism for selective interaction of MPK3/6 with SUMO-conjugated WRKY33, during defense. We show that WRKY33 is rapidly SUMOylated in response to Botrytis cinerea infection and flg22 elicitor treatment. SUMOylation mediates WRKY33 phosphorylation by MPKs and consequent transcription factor activity. Disruption of either WRKY33 SUMO or MPK3/6 SIM sites attenuates their interaction and inactivates WRKY33-mediated defense. However, MPK3/6 SIM mutants show normal interaction with a non-SUMOylated form of another transcription factor, SPEECHLESS, unraveling a role for SUMOylation in differential substrate selectivity by MPKs. We reveal that the SUMO proteases, SUMO PROTEASE RELATED TO FERTILITY1 (SPF1) and SPF2 control WRKY33 SUMOylation and demonstrate a role for these SUMO proteases in defense. Our data reveal a mechanism by which MPK3/6 prioritize molecular pathways by differentially selecting substrates using the SUMO–SIM module during defense responses.

Item Type:Article
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Available under License - Creative Commons Attribution Non-commercial No Derivatives 4.0.
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Publisher statement:Copyright © 2021 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).
Date accepted:20 January 2021
Date deposited:24 June 2021
Date of first online publication:01 March 2021
Date first made open access:24 June 2021

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