Résumé
Aphids are among the most devastating insect pests on cultivated plants worldwide. They weaken their host plants by ingesting plant sap through their specialized piercing-sucking mouthparts. They also act as vectors and are known to transmit around 50% of the insect-borne phytoviruses. The majority of these viruses are transmitted in a noncirculative way: they are reversibly retained on specific receptors located on the cuticle of aphid stylets during their journey from one plant to another and can be rapidly inoculated into a new host within a single puncture lasting a few seconds. The Cauliflower mosaic virus (CaMV) has been shown to bind to receptors present at the surface of the acrostyle, a nano-organ at the tip of aphid maxillary stylets, on which Potyviruses and Cucumoviruses could also bind. The identification of these receptors is a key challenge to understand the mechanisms underlying noncirculative virus transmission and to develop new strategies to disrupt virus-vectors interactions. We have characterized the repertoire of the cuticular proteins of Acyrthosiphon pisum stylets by proteomics analysis, and determined the ones that display peptides directly exposed at the surface of the acrotyle, the Stylins. Their role in the transmission of noncirculative viruses is currently evaluated by silencing their genes through RNAi technology. Apart from plant viruses, we suspect that Stylins could bind other molecules present in the plant or in the aphid saliva, and therefore play a role in plant-aphid interactions. An interaction between one Stylin and the effector Mp10 was revealed in the yeast two-hybrid system. We also showed that this effector is able to bind the acrostyle of dissected stylets. These results suggest that the acrostyle might play a role not only in virus retention but also during the aphid-feeding process in binding effectors known to counteract plant defenses