Functional Characterization of Protease Inhibitor SlPinII5 in Tomato Resistance to Late Blight

Tomato yield and quality are severely threatened by late
blight
caused by Phytophthora infestans. Enhancing
natural disease resistance offers a sustainable alternative to chemical
control. Proteinase inhibitor II (PinII) has emerged as a promising
candidate for improving plant resistance. However, the functional
basis of their role in tomato defense remains largely unclear. In
this study, 12 SlPinII genes were identified, and SlPinII5 was selected for its strong response to P. infestans. Functional analyses showed that SlPinII5 enhances tomato resistance by activating defense-related
genes, modulating enzyme activities, and regulating reactive oxygen
species. Enrichment analysis of differentially expressed genes indicated
that SlPinII5 is involved in regulating several disease
resistance-related pathways. Moreover, purified SlPinII5 directly
inhibited P. infestans growth and reduced
infection in tomato leaves and fruits. These findings indicate that
SlPinII5 positively regulates tomato defense, providing insights for
resistance breeding and sustainable disease management.