HvWRKY2 acts as an immunity suppressor and targets HvCEBiP to regulate powdery mildew resistance in barley
Deshui Yu, Renchun Fan, Ling Zhang, Pengya Xue, Libing Liao, Meizhen Hu, Yanjun Cheng, Jine Li, Ting Qi, Shaojuan Jing, Qiuyun Wang, Arvind Bhatt, Qian‐Hua Shen
Abstract
Plants use a sophisticated immune system to perceive pathogen infection and activate immune responses in a tightly controlled manner. In barley, HvWRKY2 acts as a repressor in barley disease resistance to the powdery mildew fungus, Blumeria graminis f. sp. hordei (Bgh). However, the molecular features of HvWRKY2 in its DNA-binding and repressor functions, as well as its target genes, are uncharacterized. We show that the W-box binding of HvWRKY2 requires an intact WRKY domain and an upstream sequence of ∼75 amino acids, and the HvWRKY2 W-box binding activity is linked to its repressor function in disease resistance. Chromatin immunoprecipitation (ChIP)-seq analysis identified HvCEBiP, a putative chitin receptor gene, as a target gene of HvWRKY2 in overexpressing transgenic barley plants. ChIP-qPCR and Electrophoretic Mobility Shift Assay (EMSA) verified the direct binding of HvWRKY2 to a W-box-containing sequence in the HvCEBiP promoter. HvCEBiP positively regulates resistance against Bgh in barley. Our findings suggest that HvWRKY2 represses barley basal immunity by directly targeting pathogen-associated molecular pattern (PAMP) recognition receptor genes, suggesting that HvCEBiP and likely chitin signaling function in barley PAMP-triggered immune responses to Bgh infection.