The role of ribosomal protein StRPS5 in mediating resistance of Solanum tuberosum plants to Phytophthora infestans

Potato late blight caused by Phytophthora infestans is a devastating disease in potato production. Effectors secreted by P. infestans can target plant proteins and disrupt plant immune responses. The research on plant target proteins has mainly focused on ubiquitination, immune-related proteases, MAPK signal transduction pathways, and transcription factors. The question of whether plants possess novel disease resistance-related proteins or pathways remains unanswered. In this study, we identified a potato ribosomal protein, StRPS5, as a target of the P. infestans RxLR effector, Pi16275. Subcellular co-localization of StRPS5 and Pi16275 was observed in the nucleus, cytoplasm and cell membrane of Nicotiana benthamiana. The expression of StRPS5 was induced and up-regulated in the early stage of P. infestans infection. Furthermore, transient overexpression of StRPS5 in tobacco leaves was observed to inhibit the infection. We also observed a significant accumulation of H₂O₂ at the site of StRPS5 overexpression, indicating a role of StRPS5 in promoting the outbreak of reactive oxygen species (ROS) burst after pathogen infection. Silencing of StRPS5 in potato exhibited a marked increase in susceptibility towards P. infestans, whereas overexpression of the gene led to an enhancement of disease resistance. As ROS are key signaling molecules in plant immune responses against pathogens, we investigated flg22-triggered ROS accumulation in transgenic potatoes and the results showed that ROS accumulation in StRPS5-silenced leaves was significantly depressed, while the accumulation was increased in StRPS5-overexpressing leaves. Collectively, our findings demonstrate that potato ribosomal protein StRPS5 serves as a target for the P. infestans effector Pi16275 and that StRPS5 positively regulates potato resistance to P. infestans by increasing the accumulation of ROS.