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Plant J. 2019 Feb 9. doi: 10.1111/tpj.14278. [Epub ahead of print]

The Mediator kinase module acts as a positive regulator of salicylic acid accumulation and systemic acquired resistance.

Author information

1
Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.
2
Department of Botany, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.
3
Department of Chemistry, University of British Columbia, Vancouver, BC, Canada, V6T 1Z1.

Abstract

In plants, the calmodulin-binding transcription activators (CAMTAs) are required for transcriptional regulation of abiotic and biotic stress responses. Among them, CAMTA3 in Arabidopsis has been intensively studied and shown to function redundantly with CAMTA1 and CAMTA2 to regulate plant immunity. The camta1/2/3 triple mutant accordingly exhibits severe dwarfism due to autoimmunity. Here, through a suppressor screen using camta1/2/3 triple mutant, we found that a mutation in Cyclin-Dependent Kinase 8 (CDK8) partially suppresses the dwarfism and constitutive resistance phenotypes of camta1/2/3. CDK8 positively regulates steady-state SA levels and systemic required resistance (SAR). The expression of salicylic acid (SA) biosynthesis genes such as ICS1 and EDS5 is down-regulated in cdk8 mutants under uninfected conditions, suggesting that CDK8 contributes to the transcriptional regulation of these SA pathway genes. Knocking out another Mediator kinase module member MED12 yielded similar defects including decreased steady-state SA level and compromised SAR, suggesting that the whole Mediator kinase module contributes to the transcriptional regulation of SA levels and SAR. This article is protected by copyright. All rights reserved.

KEYWORDS:

CAMTA ; Arabidopsis thaliana; CDK8; MED12; Mediator; plant immunity; salicylic acid; systemic acquired resistance; transcriptional regulation

PMID:
30739357
DOI:
10.1111/tpj.14278

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