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.
Zhang et al. (Sat,) studied this question.