VmSpm1: a secretory protein from Valsa mali that targets apple's abscisic acid receptor MdPYL4 to suppress jasmonic acid signaling and enhance infection

The Magnaporthe oryzae effector MoCHT1 targets and stabilizes rice OsLLB to suppress jasmonic acid synthesis and enhance infection

Rice blast disease caused by Magnaporthe oryzae (M. oryzae) poses a serious threat to rice security worldwide. This filamentous pathogen modulates rice defense responses by secreting effectors to facilitate infection. The phytohormone jasmonic acid (JA) plays crucial roles in the response to rice blast fungus, however, how M. oryzae disrupts JA-mediated resistance in rice is not well understood. In this study, we identify a new effector, a chloroplast-targeting protein (MoCHT1), from M. oryzae. Knocking out MoCHT1 decreases virulence, whereas heterologous expression of MoCHT1 in rice compromises disease resistance. MoCHT1 interacts with a rice LESION AND LAMINA BENDING (OsLLB) protein, a negative regulator of JA biosynthesis in the chloroplast. Loss-of-function of OsLLB leads to increased JA accumulation, thereby improving resistance to rice blast. The interaction between MoCHT1 and OsLLB results in the inhibition of OsLLB degradation, consequently reducing JA accumulation, thereby impairing JA content and decreasing plant disease resistance. Overall, this study reveals the molecular mechanism by which M. oryzae utilizes MoCHT1 to subvert rice JA signaling, broadening our understanding of how pathogens circumvent host immune responses by manipulating plant defense hormone biosynthesis.

The Valsa mali Effector VmSR1 Accelerates the Degradation of Tudor-SN2 to Suppress RNA Silencing and Plant Immunity

The apple Valsa canker caused by Valsa mali is one of the most destructive trunk diseases in apple production and disease management. Understanding the interaction between the pathogen and host is a critical foundation for developing durable disease control technologies. In this study, we showed that VmSR1 from V. mali can suppress the plant immune response and promote pathogen infection. VmSR1 associates with the Tudor staphylococcal nuclease 2 (TSN2) proteins in Malus domestica (apple), Arabidopsis thaliana and Nicotiana benthamiana, promotes degradation of TSN2 proteins, and suppresses the abundance of multiple miRNAs an Silencing of TSN2 significantly reduced the abundance of miRNAs and weakened the resistance of apple leaves to V. mali as well as N. benthamiana to Sclerotinia sclerotiorum. These findings expand the understanding of the function of effectors as RNA silencing suppressors during host-pathogen interactions and deepen the understanding of effectors regulating host immunity.