Beet Chlorosis Virus Infection Mitigates Aphid-Induced Plant Defences and Improves Plant Acceptability to Aphid Vectors.

Plant viruses often alter host traits in ways that affect interactions with herbivores, potentially facilitating their own acquisition and transmission by insect vectors. However, little is known about the molecular mechanisms underlying this phenomenon. This is particularly true for agronomically important pathosystems, such as the viruses responsible for sugar beet yellowing. Among them is the beet chlorosis virus (BChV), whose effects on aphid vector behaviour and plant defence mechanisms have not been fully characterised. In this study, we demonstrate that BChV infection suppresses sugar beet defences induced by aphid pre-infestation, enhancing plant acceptability for aphids. Specifically, gene expression analyses revealed a downregulation of the aphid-induced ethylene pathway in infected plants, along with alterations in the salicylic acid pathway that may benefit aphids. Metabolic profiling highlighted reduced levels of phenolic acids, including cinnamic and coumaric acids, in virus-infected plants which likely contribute to increased plant acceptability by aphids. By integrating gene expression, metabolic profiling, and behavioural assays, our findings illustrate how BChV manipulates host-plant defences to potentially increase its transmission by aphids, underscoring the broad ecological and evolutionary significance of virus-mediated plant-vector interactions.