Stylins in the acrostyle cuticular interface mediate non-circulative stylet-borne virus transmission

Non-circulative transmission of plant viruses relies on rapid and reversible interactions between virions and their vectors, occurring either in the stylets or in the foregut. Stylet-borne viruses are retained in aphid stylets at the surface of the cuticle, especially on the acrostyle, an acellular specialized structure at the distal tip of maxillary stylets. Recent studies have identified a small set of cuticular proteins, called stylins, with domains directly exposed at the virus-acrostyle interface, thus potentially contributing to virus binding. The acrostyle was also shown to retain the salivary effector Mp10, likely via Stylin-03, suggesting that stylins mediate the retention of important molecules for successful aphid feeding. Several stylins are exploited by viruses across diverse genera for transmission. In particular, functional studies using RNAi-mediated gene knockdown and CRISPR-Cas9 mutagenesis in aphids demonstrated that Stylin-01 is required for efficient transmission of both cauliflower mosaic virus and turnip mosaic virus, with Stylin-04/04bis further contributing to the latter. The observation of residual transmission after disrupting individual stylins suggests functional redundancy within the acrostyle. This review highlights stylins as core components of the aphid stylet cuticular acellular interaction platform that enable non-circulative virus transmission.