Mediator Subunit MED25 Couples Alternative Splicing of JAZ Genes with Fine-Tuning of Jasmonate Signaling.

Fangming Wu,Qingzhe Zhai,Lei Deng,Chuanyou Li,Qian Chen,Jiuhai Zhao

doi:10.1105/tpc.19.00583

Abstract

JASMONATE ZIM-DOMAIN (JAZ) transcriptional repressors are key regulators of jasmonate (JA) signaling in plants. At the resting stage, the C-terminal Jas motifs of JAZ proteins bind the transcription factor MYC2 to repress JA signaling. Upon hormone elicitation, the Jas motif binds the hormone receptor CORONATINE INSENSITIVE1, which mediates proteasomal degradation of JAZs and thereby allowing the Mediator subunit MED25 to activate MYC2. Subsequently, plants desensitize JA signaling by feedback generation of dominant JAZ splice variants that repress MYC2. Here we report the mechanistic function of Arabidopsis (Arabidopsis thaliana) MED25 in regulating the alternative splicing of JAZ genes through recruiting the splicing factors PRE-mRNA-PROCESSING PROTEIN 39a (PRP39a) and PRP40a. We demonstrate that JA-induced generation of JAZ splice variants depends on MED25 and that MED25 recruits PRP39a and PRP40a to promote the full splicing of JAZ genes. Therefore, MED25 forms a module with PRP39a and PRP40a to prevent excessive desensitization of JA signaling mediated by JAZ splice variants.

Highlights

Jasmonate (JA) is a lipid-derived hormone that regulates diverse aspects of plant immunity and development (Browse, 2009; Wasternack and Hause, 2013; Chini et al., 2016; Goossens et al, 2016; Zhai et al, 2017)
Generation of dominant JASMONATE ZIM-DOMAIN (JAZ) splice variants is an integral part of MYC2- and
We selected JAZ6, which contains a representative Jas intron, as a model to investigate whether the alternative splicing (AS) of JAZ genes depends on the core JA signaling components including CORONATINE-INSENSITIVE 1 (COI1), MYC2 and MED25

Summary

Introduction

Jasmonate (JA) is a lipid-derived hormone that regulates diverse aspects of plant immunity and development (Browse, 2009; Wasternack and Hause, 2013; Chini et al., 2016; Goossens et al, 2016; Zhai et al, 2017). In Arabidopsis thaliana, JA triggers a genome-wide transcriptional program that is largely regulated by MYC2 (Boter et al., 2004; Lorenzo et al, 2004; Dombrecht et al, 2007; Fernandez-Calvo et al, 2011; Kazan and Manners, 2013; Zhai et al, 2013; Chini et al, 2016; Zhai et al, 2017) The activity of this master transcription factor depends on its physical and functional interactions with MED25, a subunit of the plant Mediator transcriptional coactivator complex (Cevik et al, 2012; Chen et al, 2012; An et al, 2017; Zhai et al, 2018; Wang et al, 2019). JAZ proteins can act as both transcriptional repressors (in the absence of JA-Ile) and hormone co-receptors (in the presence of JA-Ile)

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