The conserved aphid saliva chemosensory protein effector Mp10 targets plant AMSH deubiquitinases at cellular membranes to suppress pattern-triggered immunity

Chemosensory proteins (CSPs) are a conserved family present in insects and other arthropods, recognized for their critical roles in both intra- and interspecies communication. However, the functional mechanisms of these proteins remain largely unexplored. In our previous research, we identified a CSP in aphid saliva, Mp10, from the peach-potato aphid Myzus persicae, which functions as an effector protein modulating host plant immunity. Mp10 suppresses pattern recognition receptor (PRR)-triggered immunity (PTI), the first layer of plant defence, while also inducing effector-triggered immunity (ETI). In this study, we elucidate the molecular mechanisms by which Mp10 suppresses PTI. Our findings reveal that Mp10 interacts with AMSH deubiquitinase enzymes in plants, as shown by yeast two-hybrid, co-immunoprecipitation (co-IP), and FRET-FLIM assays, with these interactions predominantly localized to intracellular membranes. Mp10 was found to modulate the dynamics of membrane-bound PRR receptor kinases in plant cells. Co-IP and mass spectrometry analyses demonstrated that Mp10 and AMSH2 associate with a range of PRR kinases, PRR-associated kinases, and proteins involved in the intracellular trafficking of membrane proteins. Mp10 reduces the accumulation of these kinases at the cell surface by promoting their internalization to internal membranes, thereby dampening PTI. Supporting this, a dominant-negative catalytically inactive variant of AMSH2 also inhibits PTI. Interestingly, Mp10 orthologues from other sap-feeding hemipteran insects exhibit similar immune-suppressive activities, and our findings show that their interaction with plant AMSH proteins is conserved, indicating this immune-suppression mechanism is evolutionarily ancient.