Capsicum annuum RPW8 Confers Broad-Spectrum Resistance against Multiple Pathogens.

Pepper (Capsicum annuum) suffers substantial yield and quality losses caused by pathogens including Phytophthora capsici, Botrytis cinerea, and Ralstonia solanacearum. Although the atypical resistance protein RPW8 is recognized to confer disease resistance, its role in pepper immunity remains unexplored. Here, we show that CaRPW8 expression is significantly induced following P. capsici infection. Phylogenetic analyses revealed that CaRPW8 exhibits high similarity with its Solanaceae homologues. Unlike Arabidopsis RPW8 proteins, CaRPW8 localized to the plasma membrane. Silencing of CaRPW8 significantly increased pepper's susceptibility to P. capsici, B. cinerea, and R. solanacearum, while transient overexpression enhanced the resistance. Moreover, stable overexpression of CaRPW8 in Nicotiana benthamiana also conferred enhanced broad-spectrum resistance. Mechanistically, CaRPW8 orchestrated a synergistic defense network by promoting callose deposition and reactive oxygen species (ROS) accumulation. Collectively, this study provided evidence for RPW8-mediated immunity through a synergistic "callose-ROS" defense module and established CaRPW8 as a promising candidate for engineering broad-spectrum resistance.