SAPK10-Mediated Phosphorylation on WRKY72 Releases Its Suppression on Jasmonic Acid Biosynthesis and Bacterial Blight Resistance

Yuxuan Hou,Yifeng Wang,Liqun Tang,Xiaohong Tong,Ling Wang,Lianmeng Liu,Shiwen Huang,Jian Zhang

doi:10.1016/j.isci.2019.06.009

Abstract

SummaryBacterial blight caused by the infection of Xanthomonas oryzae pv. oryzae (Xoo) is a devastating disease that severely challenges the yield of rice. Here, we report the identification of a “SAPK10-WRKY72-AOS1” module, through which Xoo infection stimulates the suppression of jasmonic acid (JA) biosynthesis to cause Xoo susceptibility. WRKY72 directly binds to the W-box in the promoter of JA biosynthesis gene AOS1 and represses its transcription by inducing DNA hypermethylation on the target site, which finally led to lower endogenous JA level and higher Xoo susceptibility. Abscisic acid (ABA)-inducible SnRK2-type kinase SAPK10 phosphorylates WRKY72 at Thr 129. The SAPK10-mediated phosphorylation impairs the DNA-binding ability of WRKY72 and releases its suppression on AOS1 and JA biosynthesis. Our work highlights a module of how pathogen stimuli lead to plant susceptibility, as well as a potential pathway for ABA-JA interplay with post-translational modification and epigenetic regulation mechanism involved.

Highlights

The plant innate immune system is considered to contain two interconnected layers termed PTI and ETI (Jones and Dangl, 2006)
Transcription of WRKY72 Is Induced by Xanthomonas oryzae pv. oryzae (Xoo) Infection and Exogenous jasmonic acid (JA) To find out the rice WRKYs involved in defense against bacterial blight, we performed Quantitative RT-PCR (qRT-PCR) analysis of various WRKYs in a time line after Xoo inoculation and found that WRKY72 (LOC_Os11g29870) is highly induced
WRKY72 responds to treatment of exogenous phytohormones JA and Abscisic acid (ABA)

Summary

Introduction

The plant innate immune system is considered to contain two interconnected layers termed PTI (pathogenassociated molecular patterns-triggered immunity) and ETI (effector-triggered immunity) (Jones and Dangl, 2006). Once plant intercepts pathogen-associated molecular patterns (PAMPs) such as chitin and flagellin, it activates downstream defense signaling to provide the first layer (Jones and Dangl, 2006; Saijo et al, 2018). Plant resistance (R) proteins trigger ETI that provokes highly efficient defense responses upon effectors (Jones and Dangl, 2006; Peng et al, 2017). WRKY proteins recognize the W-box (T)TGAC(C/T) or W-like box cis-regulatory elements, which are often found in many defense gene promoters. In addition to the W-box, it can bind other cis elements, such as sugarresponsive element (AA/TAA) in barley and pathogen response element (TACTGCGCTTAGT) in rice (Cai et al, 2008; Cheng et al, 2015; Sun et al, 2003)

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