Aphid effector pair Mp1-Mp58 forms an effector complex that targets a host trafficking protein.

Pathogen and pest effectors play a crucial role in manipulating plant biological processes, facilitating infection and infestation. While pathogens and pests secrete repertoires of effectors into host plants, most effector function studies focus on characterizing individual proteins. Our previous work identified a genetically linked and co-regulated gene pair in the aphid pest Myzus persicae encoding effectors Mp1 and Mp58. Here, we explored the functional link between these two effectors. We revealed that effectors Mp1 and Mp58 interact in planta and in vitro and form an oligomeric complex. The putative orthologues of the Mp1-Mp58 pair in the aphid species Rhopalosiphum padi, Rp1 and Rp58, also interact, but members of the pair cannot interact across aphid species, suggesting that effector pairs have co-evolved within each aphid species but diversified across species. Both Mp1 and Mp58 associate with the host Vacuolar Protein Sorting associated Protein 52 (VPS52) to form an Mp1-Mp58-VPS52 complex, which localizes at vesicle-like structures. Our findings point to effector complex formation in plant-insect interactions and highlight a further layer of complexity in the molecular dialogue between insects and their host plants. Our work highlights the importance of considering the context in which effectors may function within a larger effector repertoire.