Do stylet‐borne aphid‐transmitted viruses share the same binding sites?

Abstract Specific binding sites for non‐circulative viruses within the mouthparts of aphid vectors have been investigated with limited success. Such sites have been described more precisely for cauliflower mosaic virus (CaMV, Caulimovirus ), and shown to be restricted to the acrostyle, a specific anatomical structure located in the common duct of the aphid stylets. However, the nature and precise location of binding sites of other non‐circulative viruses (e.g., cucumoviruses and potyviruses), and whether distinct viral species compete for the same sites remains unknown. In this study, competition between non‐circulative viruses for binding sites was assessed for viruses that differ in their transmission mode: cucumber mosaic virus (CMV, Cucumovirus ), transmitted by the capsid strategy, and three viruses using the helper strategy for their transmission—turnip mosaic virus (TuMV, Potyvirus ), zucchini yellow mosaic virus (ZYMV, Potyvirus ), and CaMV. In this work, we performed competition and sequential acquisition experiments, with contrasting results obtained depending on the virus species used and the sequence of acquisition/inoculation of the potentially competing viruses. Our results showed that potyviruses and caulimoviruses do not appear to compete for the same binding sites and/or receptors within aphid stylets, as no modifications in their transmission rates were observed regardless of their acquisition sequence. However, a decrease of CMV transmission rate when ZYMV was previously acquired, suggests that potyviruses and cucumoviruses might compete for binding sites in their aphid vectors. Moreover, we observed that potyviruses and cucumoviruses can be co‐acquired and co‐inoculated in the same plant cell during a single intracellular puncture, demonstrating co‐infection of individual cells by more than a single virus species.