7-Hydroxylathyrol defeats geminivirus through targeting C4 and activating host defense

Tomato yellow leaf curl virus (TYLCV), which belongs to Geminiviruses, is a notorious plant virus that poses a threat to global agriculture. 7-Hydroxylathyrol is a renowned lathyrane diterpenoid with a broad spectrum of pharmacological activities. However, its efficacy against plant pathogens remains unknown. In this study, we investigated the antiviral activity of 7-hydroxylathyrol against TYLCV and explored the molecular mechanisms underlying its antiviral effects. 7-Hydroxylathyrol significantly disrupted TYLCV and inhibited its accumulation in Nicotiana benthamiana. To explore the mechanism of 7-hydroxylathyrol against TYLCV, proteins encoded by TYLCV were purified, and their interactions with 7-hydroxylathyrol were studied. Biolayer interferometry and pull-down experiments showed that 7-hydroxylathyrol bound to C4 with a dissociation constant of 6.50 × 10^-8 M, while it could not bind to other viral proteins. Moreover, 7-hydroxylathyrol inhibited gene expression and protein accumulation of C4 in N. benthamiana, and the infectious clone TYLCV(ΔC4), which contains a nontranslatable C4, weakened the inhibitory effect of 7-hydroxylathyrol against the virus. Furthermore, molecular docking and point mutation analyses were implemented, and results indicated that the specific R37 and T38 of C4 were critical for the interaction between 7-hydroxylathyrol and C4. In addition, 7-hydroxylathyrol could inhibit another geminivirus, tobacco curly shoot virus (TbCSV), which also possessed these two conserved sites. At last, we found that 7-hydroxylathyrol enhanced the plant defense capacity by increasing the activity of defense enzymes and upregulating the expression of pathogenesis-related genes. These results demonstrated that 7-hydroxylathyrol possessed a dual antiviral mechanism of binding TYLCV C4 and activating plant defense responses. This study provided key insights for designing novel plant geminivirus inhibitors.