CAM5, WRKY53, and TGA5 regulate defense gene expression mediated by the volatile organic compound ethyl vinyl ketone

Abstract

AbstractPlants produce ethyl vinyl ketone (evk) in response to biotic stress, but the evk’s identification and downstream defense response remain unclear. In this paper, it is predicted by docking for the first time that evk can be recognized by RBOH protein and assist the electron transfer of RBOHD/RBOHF by binding to its FAD or NADPH binding site. Here, we show that evk treatment increased H2O2and intracellular calcium concentrations inArabidopsis thalianamesophyll cells, as observed by confocal laser scanning microscopy and non-invasive micro-test technology, and that H2O2signaling functioned upstream of Ca2+signaling. Yeast two-hybrid, firefly luciferase complementation imaging, andin vitropull-down assays demonstrated that the ACA8 (AUTOINHIBITED Ca2+-ATPASE, ISOFORM 8)–CML8 (CALMODULIN-LIKE 8) interaction promoted Ca2+efflux to return Ca2+levels to the resting state. Evk treatment led to the antagonism of salicylic acid (SA) and jasmonic acid (JA). CALMODULIN 5 (CAM5) positively regulatesWRKY53expression, and CAM5 and WRKY53 positively regulate SA-related gene expression. These proteins physically interact and form a complex that is unlocked by Ca2+to release WRKY53. An electrophoretic mobility shift assay and dual-luciferase reporter assay demonstrated that WRKY53 and TGA5 cooperate to enhance the expression of the defense genePATHOGENESIS-REALTED 1(PR1) and that WRKY53 enhances the binding of TGA5 to thePR1promoter. This paper proposes a framework that evk, as a RES substance, can achieve plant’s ‘REScue’ through complete defense response.