LUX ARRHYTHMO mediates crosstalk between the circadian clock and defense in Arabidopsis

Chong Zhang,Riki Egoshi,Nadim Alkharouf,Daniela Lin,Min Gao,C Robertson Mcclung,Omar Darwish,Hua Lu,Teklu Dawit,William Angel,Amelia Hallworth,Linda Wiratan,Nicholas C Seitz,Xiping Wang

doi:10.1038/s41467-019-10485-6

Abstract

The circadian clock is known to regulate plant innate immunity but the underlying mechanism of this regulation remains largely unclear. We show here that mutations in the core clock component LUX ARRHYTHMO (LUX) disrupt circadian regulation of stomata under free running and Pseudomonassyringae challenge conditions as well as defense signaling mediated by SA and JA, leading to compromised disease resistance. RNA-seq analysis reveals that both clock- and defense-related genes are regulated by LUX. LUX binds to clock gene promoters that have not been shown before, expanding the clock gene networks that require LUX function. LUX also binds to the promoters of EDS1 and JAZ5, likely acting through these genes to affect SA- and JA-signaling. We further show that JA signaling reciprocally affects clock activity. Thus, our data support crosstalk between the circadian clock and plant innate immunity and imply an important role of LUX in this process.

Highlights

The circadian clock is known to regulate plant innate immunity but the underlying mechanism of this regulation remains largely unclear
Recent studies have established the role of the circadian clock in regulating plant innate immunity
The mechanisms underlying this role of the circadian clock are still not well understood

Summary

Introduction

The circadian clock is known to regulate plant innate immunity but the underlying mechanism of this regulation remains largely unclear. We show here that mutations in the core clock component LUX ARRHYTHMO (LUX) disrupt circadian regulation of stomata under free running and Pseudomonas syringae challenge conditions as well as defense signaling mediated by SA and JA, leading to compromised disease resistance. In the presence of pathogens and pests, plants activate acute defense responses, including drastic increases in SA and other defense compounds and reprogramming of defense-related genes. While the levels of SA oscillate daily in unchallenged plants[16,17], timely accumulation of SA in high abundance in the local infected region dictates the outcome of plant response to some pathogens[20,21] Genes affecting such acute SA accumulation are important for plant defense[22,23,24], no clock genes have yet been reported to play such a role in SA regulation. Our data reveal an important role of LUX mediating the crosstalk between the circadian clock and plant innate immunity

Methods

Results

Conclusion