Targeted dsRNA-mediated suppression of Phytophthora infestans infection via Avr3a

Phytophthora infestans (P. infestans) is a highly destructive oomycete that causes the late blight in Solanaceous crops, such as potatoes and tomatoes, reducing crop yield. Although many pesticides are used to control P. infestans, the pathogen has evolved resistance to these chemical pesticides over time. In this study, we employed RNAi technology as an alternative strategy to suppress P. infestans infection. We designed and synthesized two dsRNAs targeting 5' and 3' regions of the Avirulence Protein 3a (Avr3a) gene, a key effector essential for the virulence of P. infestans. Interestingly, the dsRNA targeting the 5' region which contains the conserved RxLR-EER motif of Avr3a exhibited more substantial suppression of P. infestans infection and Avr3a expression level compared to the 3' region targeting dsRNA. Additionally, we identified changes in the expression of genes related to pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) in plants treated with these dsRNAs. In leaves treated with dsRNAs targeting Avr3a, the expression of PTI-related genes was restored, while ETI-related genes showed lower expression levels compared to the mock-treated leaves. These results suggest that dsRNAs targeting Avr3a effectively suppress P. infestans infection, enabling plants to achieve balanced immunity and enhanced defense.