Host-Specific Transcriptional Responses ofPhytophthora capsiciDuring Early Crown Infection in Cucurbitaceous and Solanaceous Plants

Phytophthora capsiciis a broad-host-range oomycete phytopathogen responsible for economic losses in crops worldwide. Previous transcriptomic analyses have focused mainly on plant responses to infection. However, the transcriptional adaptations of the phytopathogen to different host species remain poorly understood. In this study, we investigated the transcriptomic response ofP. capsiciduring early infection inCucumis sativus, Cucumis melo, Capsicum annuumCM334, andSolanum lycopersicumby RNA-seq and multiphoton microscopy. Focusing on crown infections since it is the natural entry point for the pathogen.

Our results reveal striking host-specific infection strategies. In tomato, rapid necrosis at 12-27 hours post-inoculation was associated with early metabolic reprogramming and effector repression. In contrast, cucurbits exhibited delayed necrosis (36-102 hpi), supporting extensive host intracellular colonization and upregulation of carbohydrate metabolism pathways. Partially resistant CM334 chili pepper restricted pathogen proliferation, withP. capsicidisplaying transcriptional signatures indicative of metabolic stress. In addition, effector expression is tightly regulated, with the differential deployment of RxLR, NLP, and CRN families across hosts.

Comparative transcriptomics highlights metabolic reprogramming as a key determinant of infection success, withP. capsicifine-tuning its gene expression to exploit host-specific vulnerabilities. These findings provide novel insights intoP. capsiciadaptive strategies in soil-borne infections and underscore the importance of targeting crown infection sites for disease management. Future research should integrate host transcriptomics and functional studies to elucidate the molecular determinants of host specificity.