The universal stress protein SlUSP1 modulates Botrytis cinerea resistance via ATP-dependent chitinase activation in...

Universal Stress Proteins (USP) are involved in multiple stress responses across diverse species. In tomato (Solanum lycopersicum), the pathogen Botrytis cinerea causes significant yield losses. This study identifies tomato SlUSP1 as a cytoplasmic protein and a positive regulator of defense against B. cinerea. Overexpression of SlUSP1 in tomato reduced disease symptoms, elevated defense-related gene expression, and enhanced antioxidant enzyme activity during infection, whereas slusp1 knockout lines showed increased susceptibility. We demonstrate that SlUSP1 is degraded via ubiquitination mediated by SlWDR23 and SlWDR110, two WD40 repeat proteins that function as substrate receptors for the CRL4 ubiquitin ligase complex. B. cinerea infection suppresses SlWDR23 and SlWDR110, leading to SlUSP1 accumulation, which in turn enhances chitinase activity in an ATP hydrolysis-dependent manner. These findings establish the CRL4^{SlWDR23/SlWDR110}-SlUSP1-chitinase regulatory mechanism in antifungal defense in tomato and highlight the potential of gene‑editing for improving crop resistance.