Temporal expression patterns of SnRK1 and WRKY3 defense genes reveal cultivar-specific responses to tomato curly stunt virus infection

Tomato curly stunt virus (ToCSV) significantly impacts tomato production globally, yet the molecular mechanisms underlying cultivar-specific resistance responses remain poorly understood. We investigated the temporal expression of two key defense-related genes, Sucrose Non-Fermenting 1-Related Protein Kinase 1 (SnRK1) and WRKY transcription factor 3 (WRKY3), across four tomato cultivars with varying susceptibility to ToCSV: susceptible (Rooikhaki, Moneymaker), tolerant (NIL396), and resistant (ESTY). Using quantitative real-time PCR, we analyzed gene expression at 8, 15, and 35 days post-infection, representing early infection, symptom onset, and systemic viral movement stages. Viral quantification revealed distinct accumulation patterns, with susceptible cultivars showing 283–440 % increases in viral load between 15 and 35 dpi, while the tolerant cultivar maintained stable levels and the resistant cultivar remained undetectable. SnRK1 expression patterns differed between cultivars: susceptible lines showed initial downregulation (15 dpi) followed by upregulation (35 dpi), while the resistant cultivar exhibited consistent downregulation. WRKY3 displayed complex temporal patterns, with most cultivars showing early upregulation followed by late-stage downregulation, except the resistant cultivar, which maintained downregulation throughout. These results provide the first comparative temporal analysis of defense gene expression in the tomato-ToCSV pathosystem and suggest that resistance mechanisms involve distinct regulatory strategies rather than simple gene activation patterns.