Cauliflower mosaic virus (CaMV) forms transmission bodies (TB) in infected cells that are viral inclusions mandatory for aphid transmission of CaMV. TB are composed mainly of viral proteinsP2 and P3 and some virus particles. When an aphid inserts its stylets into infected plant cells, the mechanical and/or chemical stress caused by the sting induces a rapid and reversible response of the TB: tubulin flows into the TB, then the TB disintegrates, and its P2 contents relocates on microtubule networks. Simultaneously, virus particles are recruited from virus factories and associate with the P2-microtubule networks. This phenomenon that we have named Transmission activation enhances greatly CaMV transmission. The TB reaction obviously requires hitherto unknown host cell factors that are diverted to allow transmission.To identify these host factors, we are developing a method based on Proximity Ligation Assays (PLA) to detect proteins interactions in fixed tissues or cells. A myc-tagged cDNA library of Arabidopsis thaliana is cloned in a vector for transient expression and used to transfect CaMV-infected protoplasts. Specific interactions between the major TB component P2 and library proteins are then detected by Duolink technology using antibodies against P2 and the myc-tag. Finally, cells positive for interactions will be isolated by laser microdissection or FACS and the candidate protein is identified by sequencing of the transfected plasmids after amplification in bacteria. We are currently setting up this new method in a “proof of principle” approach using the established interaction between P2 and tubulin and present our first results. Once its feasibility shown, this method can be also used to identify and characterize interactions in other experimental systems.