Ionotropic receptor co-receptors drive host-seeking behavior in the white-backed planthopper (Hemiptera: Delphacidae)

The white-backed planthopper, Sogatella furcifera (Horváth, 1899), is a destructive rice pest that causes severe yield losses across Asia. Here, we manually curated a class of olfactory receptors: ionotropic receptors (IRs) genes using genomic and transcriptomic data, characterized tissue-specific expression profiles, and explored the functions of 3 IRco genes (SfurIR8a, SfurIR25a, SfurIR76b) via RNA interference (RNAi) and two-choice behavioral assays. We identified 14 IR genes and 3 IRco genes in S. furcifera, and the 3 IRco genes were predominantly expressed in the antennae of both sexes. qPCR verification confirmed that the expression of the 3 IRco genes was significantly downregulated after RNAi, with no obvious lethal effects on the nymphs. Behavioral assays showed that silencing any of the 3 IRco genes drastically impaired the host location ability of S. furcifera. Compared with the control, the relative response rate to rice seedlings dropped from positive to negative values at 2.5 and 3 h, the lack-of-response percentage increased notably, and the precise positioning rate on rice seedlings decreased significantly. These results demonstrate that SfurIR8a, SfurIR25a, and SfurIR76b are essential for olfactory perception and host-seeking behavior in S. furcifera. This study reveals the molecular basis of IRco-mediated olfactory processes in this pest and provides promising gene targets for developing novel olfactory-disruption strategies for rice pest management.