Baculovirus manipulation of nutrient-based host choice via an infection responsive olfactory receptor in Spodoptera...

Baculoviruses are widely used as biological control agents against lepidopteran pests, yet their effects on host feeding and oviposition behaviour remain poorly understood compared with plant and vertebrate viruses that are known to manipulate vector host choice. Here, using Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) and its host S. exigua as a model, we show that viral infection reconfigures host use through an axis linking olfaction and nutrition. SeMNPV infection of fifth instar larvae shifted feeding preference from carbohydrate-rich to protein-rich host plants, a pattern that was independently confirmed on artificial diets differing only in protein to carbohydrate ratio. Comprehensive analysis of genomic and transcriptomic data allowed us to annotate 66 olfactory receptor (OR) genes, among which SexiOR23 was strongly induced by SeMNPV. RNA interference of SexiOR23 abolished the infection-associated shift toward protein-rich hosts and restored the original preference for carbohydrate-rich diets, demonstrating that SexiOR23 is required for the virus-associated change in nutrient-oriented feeding. Furthermore, infected larvae feeding on high-protein diets exhibited reduced susceptibility and increased resistance to SeMNPV relative to larvae on standard diets, whereas silencing SexiOR23 did not alter viral sensitivity, indicating that this receptor drives behavioural reprogramming rather than immune activation per se. Moreover, the behavioural modification persisted into the adult stage: viruliferous females showed pronounced upregulation of SexiOR23 and switched oviposition preference from carbohydrate-rich to protein-rich host plants. These findings identify a mechanistic link between baculovirus infection, OR gene regulation and nutrient-based host choice, provide a new perspective on the ecological adaptation of noctuid pests, and offer a conceptual framework for refining SeMNPV-based biocontrol using semiochemical-guided strategies for more precise management of S. exigua.