Phytophthora infestans Effector Protein Pi08174 Suppresses Potato Immune Defense via Multiple Resistance Pathways

Late blight, caused by Phytophthora infestans, is a devastating disease that affects potato production. During the interactions with P. infestans, effectors are secreted into the plant to control the cellular activity of the host and suppress the plant immune response. However, the pathogenic mechanisms underlying most P. infestans effectors are still unclear. In this study, we focused on effector Pi08174, which is associated with immunosuppression. Agrobacterium-mediated transient expression of Pi08174 induces intense cell death and reactive oxygen species (ROS) accumulation in Nicotiana benthamiana. Overexpression of Pi08174 in potato promotes P. infestans infestation, and the transcriptome analysis of P. infestans inoculated and non-inoculated OE-Pi08174 showed that Pi08174 induced differential expression of genes in the PAMP-triggered immunity (PTI), ethylene (ET) and jasmonic acid (JA) pathways in potatoes when not inoculated with the pathogen. Also, chloroplast, mitochondrial, and antioxidant-related genes are involved in the cellular homeostasis in OE-Pi08174. After inoculation with the pathogen, multiple pathways, including the endoplasmic reticulum and cell wall, were involved in OE-Pi08174 interaction with P. infestans, and Pi08174 increased the expression of genes related to mycelial growth and virulence of P. infestans. These findings provide new insights into the regulation of plant immunity by Pi08174 and deepen our understanding of the complex relationships between pathogens and host plants.