The WAKL10 Gene Promotes Flg22-Triggered Immunity by Interacting with FLS2 and BAK1 in Arabidopsis

Background/Objectives: The wall-associated kinases (WAKs) and WAK-like proteins (WAKLs) comprise a unique receptor-like kinase subfamily in plants, which have been shown to regulate plant development and defense responses by sensing cell wall-derived components, such as pectin or pectin fragments. In this study, we aimed to characterize the function of WAKL10 in flg22-triggered immunity in Arabidopsis. Methods: Through functional analyses of WAKL genes in Arabidopsis, we identified WAKL10 as the most pronouncedly induced WAKL member in response to flg22 treatment. Gain- and loss-of-function genetic analyses were performed to assess its role in flg22-triggered immune responses, including mitogen-activated protein kinase (MAPK) activation, reactive oxygen species (ROS) burst, and defense gene induction. Transgenic Arabidopsis plants expressing a kinase domain-deleted mutant (WAKL10-ΔK) were generated. Co-immunoprecipitation assays were conducted to examine interactions with FLAGELLIN-SENSITIVE 2 (FLS2) and BRI1-ASSOCIATED RECEPTOR KINASE 1 (BAK1). Heterologous overexpression of WAKL10 in tomato was also tested for bacterial disease resistance. Results:WAKL10 positively regulates flg22-triggered immune responses. Interestingly, WAKL10-ΔK retains the capacity to potentiate these responses. Co-immunoprecipitation assays showed that both wild-type WAKL10 and WAKL10-ΔK constitutively associate with FLS2 and BAK1. Overexpression of WAKL10 in tomato confers enhanced bacterial disease resistance. Conclusions: The extracellular domain of WAKL10 promotes FLS2-BAK1 complex formation, thereby contributing to flg22 signaling. This study reveals a new function of WAKLs, distinguished from their proposed role in sensing cell wall components. The functional conservation of WAKL10 suggests its potential application in engineering disease resistance in crop plants.