Characterization of PAMP-induced peptides and mechanistic insights into SlPIP2-mediated defense in tomato.

SlPIP2 modulates the expression of PR genes, the activity of antioxidant enzymes, and the accumulation of defense-related metabolites in tomato, and concurrently contributes to enhanced resistance against Phytophthora infestans and Botrytis cinerea. Tomato (Solanum lycopersicum), as one of the most popular horticultural crops, is widely cultivated worldwide, however, its yield and quality is continually threatened by P. infestans. Plant peptides are engaged in the regulation of plant growth and immunity. PAMP-induced Peptides (PIPs) are new class of signaling peptides with diverse biologic roles in the regulation of plant defense responses. In this study, a total of seven SlPIP genes were identified in the tomato genome, and their expression profiles were analyzed under P. infestans infection. Among the SlPIP family members, SlPIP2 exhibited a significant response to pathogen infection. Through a combination of virus-induced gene silencing (VIGS) and gene overexpression, we demonstrated that SlPIP2 precursor (SlprePIP2) positively regulates tomato resistance. Notably, exogenous application of SlPIP2 enhanced plant defense responses, increasing resistance not only to P. infestans but also to B. cinerea, thereby highlighting its potential role in conferring broad-spectrum disease defense. To elucidate how SlPIP2 affected to tomato resistance, we performed transcriptomic analysis on tomato seedlings sprayed with HO and SlPIP2. GO and KEGG enrichment analyses revealed that SlPIP2 affects several key pathways including camalexin biosynthesis, plant-pathogen interactions, and MAPK signaling. Transcriptomic analysis further revealed that SlPIP2 regulates the expression of various transcription factors and hormone-related genes. In addition, SlPIP2 modulates the activity of antioxidant enzymes and accumulation of key defense-related metabolites. Collectively, our findings underscore the potential of SlPIP2 to enhance disease resistance in tomato, providing valuable insights and promising strategies for crop improvement and sustainable disease management.