Rice dwarf virus upregulates the odorant receptor co‐receptor of <scp> <i>Nephotettix cincticeps</i> </scp> to enhance perception of 2‐heptanol emitted from virus‐infected rice and promote its transmission

BACKGROUND: Insect odorant receptor co-receptors (Orcos) are pivotal for insect perception of host plant volatiles. We previously found that 2-heptanol-released from rice dwarf virus (RDV)-infected rice plants-repels viruliferous green rice leafhoppers (GRLHs, Nephotettix cincticeps), redirecting them to feed on RDV-free plants and thereby facilitating viral spread. However, whether Orco in N. cincticeps (NcinOrco) influences the detection of this repellent volatile and contributes to viral transmission remains unknown. RESULTS: Here, we found that NcinOrco contains seven transmembrane domains and is phylogenetically conserved. Expression profiling revealed that NcinOrco exhibits antennal-predominant expression (~5-fold) that is significantly upregulated upon RDV acquisition (~2-fold). Crucially, RNAi-mediated silencing of NcinOrco abolished the repellent behavioral response of viruliferous GRLHs (VG) to 2-heptanol (mean number of VG to paraffin oil versus 2-heptanol: dsGFP, 9.0 versus 4.4, P < 0.001; dsNcinOrco, 7.4 versus 7.0, P > 0.05), eliminated preference for RDV-free plants (mean number of VG on RDV-free versus RDV-infected: dsGFP, 9.5 versus 5.1, P < 0.001; dsNcinOrco, 7.8 versus 7.0, P > 0.05), and impaired RDV transmission efficiency (mean transmission rates on MH63 versus MH63 + 2-heptanol: dsGFP, 76% versus 35%, P < 0.001; dsNcinOrco, 51% versus 52%, P > 0.05). CONCLUSION: Our results indicate that NcinOrco is essential for detecting a key host-emitted repellent volatile, revealing how a plant virus may alter a core olfactory component to modify vector behavior and aid its transmission. Together, these findings contribute to the understanding of insect chemoreception under pathogenic stress and highlight a potential molecular interface in plant-virus-vector interactions. © 2026 Society of Chemical Industry.