Bacterial‐driven odorant receptor expression shifts alter olfactory behaviour in the oriental fruit fly

Abstract Insects rely on sophisticated olfactory systems to decode dynamic environmental cues for survival. While recent studies highlight microbiota‐mediated modulation of insect behavioural plasticity, the molecular mechanisms underlying such microbial influence remain elusive. Here, we reported that Bactrocera dorsalis gut symbiont Enterobacter sp. (MU‐1) can shift host olfactory‐guided behaviour. When adult B. dorsalis individuals had low endogenous levels of MU‐1, they exhibited avoidance of environmental MU‐1. Conversely, at normal physiological levels, they displayed a preference for MU‐1. Subsequent research indicated that MU‐1 promotes the development and growth of B. dorsalis larvae. Further transcriptome sequencing of adult heads identified four odorant receptors ( OR83a , OR67c , OR67d‐like , OR24a ) that were upregulated after antibiotic treatment. qRT‐PCR validation pinpointed OR67c as the only receptor affected by MU‐1 levels. RNA interference then found that OR67c is implicated in detecting the MU‐1 signal. Our findings unveil a tripartite interplay between gut bacteria, chemoreceptor tuning and behavioural adaptation, establishing a novel mechanism for host‐microbe crosstalk in insect sensory ecology.