Aphids are sap-feeding insects with piercing-sucking mouthparts. They are serious pests in agriculture, particularly becausethey transmit numerous plant viruses causing diseases in almost all important crops worldwide. The majority of these virusesare transmitted in a non-circulative manner where viruses are retained on specific, yet unknown, receptors located in theaphids’ stylets. A thorough characterization of the ultrastructure of the stylets lead to the discovery of the acrostyle, an“organ” located at the tip of aphids’ maxillary stylets which harbors the receptors of Cauliflower mosaic virus and possiblythose for numerous agronomically important non-circulatively transmitted viruses1,2.Apart from transmitting plant pathogens, the acrostyle, which is conserved across many aphid species, has likely an intrinsicfunction for the insect itself. At the confluence of the food and salivary canals, in contact with cell contents, phloem sap andaphid saliva, the acrostyle is expected to play a key role in plant/insect compatible interactions. Indeed, when the aphid isfeeding, the plant produces proteins and secondary metabolites with toxic or repellent effects to counter the insect’s attack3.Effectors, able to counteract these plant defenses, are delivered mixed together with saliva4 directly into the host-styletinterface. Thus the acrostyle may be important for the settlement of aphid on its host plant through the binding of toxiccompounds from the plant or the retention, concentration and release of effectors from saliva into plant cells.In attempts to understand the role of the acrostyle during the aphid feeding process and to acquire significant knowledge onplant/insect interactions, the repertoire of the cuticular proteins displaying surface exposed domains at the acrostyle will beestablished. Putative partners in plant and in aphid saliva that could interact with these cuticular proteins will be tested, usingseveral approaches among which classical biochemical interaction assays co-expression in heterologous system orscreening of libraries in the yeast-two-hybrid system. In parallel, RNAi technology will be performed to characterize theimpact of knocking down of the expression of the cuticular protein(s) identified in the acrostyle on aphid feeding behavior.