Endosomal sorting complexes required for transport (ESCRT) play a key role in membrane trafficking and are hijacked by several plant RNA viruses for their replication. In melon, the ESCRT protein CmVPS4 was recently described as a new susceptibility factor to watermelon mosaic virus (WMV, potyvirus) [1]. Indeed, a single amino acid change (P30R) in the CmVPS4 protein is responsible for WMV recessive resistance but the underlying molecular mechanisms are currently unknown. Plant ESCRT proteins have been shown to interact with viral proteins of members of the families Tombusviridae and Bromoviridae. In particular, AtVPS4 protein of A. thaliana interacts directly with the p33 replicase of tomato bushy stunt virus (Tombusviridae) for the formation of viral replication compartment (VRC). We therefore hypothesized that the P30R mutation in CmVPS4 protein in melon could prevent an interaction with a so far undetermined WMV protein. One candidate protein was the potyviral 6K2 that induces the formation of endoplasmic reticulum (ER)-derived viral vesicles crucial for potyvirus replication. Here using Split-ubiquitin membrane Y2H assay, we showed that CmVPS4 interacts with WMV-6K2. We confirmed that the orthologous protein AtVPS4 interacts with TuMV-6K2, in both SuY2H and in planta using BiFC. The 6K2/VPS4 interaction occurs at the VRC level during TuMV infection, suggesting that ESCRT complexes could also play a role in the replication of potyviruses. In the melon/WMV pathosystem, how and where the interaction between CmVPS4 and WMV-6K2 occurs and how the P30R amino acid change is responsible for the resistance are questions that are currently being addressed.[1] DOI: 10.1093/jxb/erac135Read less <