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The takeout (TO) gene family impacts diverse physiological and behavioral functions in insects, yet specific olfactory-associated roles for the family have yet to be fully elucidated. To provide insights into TO function in rice planthoppers, the genomes of three rice planthoppers (white-backed planthopper, brown planthopper and small brown planthopper) were searched for TO homologs and their degree of conservation assessed via chromosomal localization, exon-intron boundaries, phylogenetic relationships and protein domains/motifs. We performed a tissue-specific expression analysis of the 20 TO genes in the white-backed planthopper (WBPH, Sogatella furcifera) and found that SfTO17 is enriched in adult antennae. RNAi-mediated knockdown of SfTO17 impaired WBPH olfaction and reduced host-seeking responses following exposure to rice plants. The binding profile of β-ionone, hexyl benzoate and benzyl benzoate with recombinant SfTO17 was evaluated via competitive fluorescence binding assays. Conformational prediction of SfTO17 coupled with molecular docking analyses revealed several amino acid residues potentially critical for odorant binding. This study demonstrates the olfactory function of SfTO17 in WBPH and highlights its potential as a target for controlling this rice pest. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

Background: The white-backed planthopper (WBPH, Sogatella furcifera) is a major rice pest that exhibits condition dependent wing dimorphisms - a macropterous (long wing) form and a brachypterous (short wing) form. Although, the gene cascade that regulates wing development and dimorphic differentiation has been largely defined, the utility of these genes as targets for pest control has yet to be fully explored., Results: Five genes typically associated with the developmental signaling network, armadillo (arm), apterous A (apA), scalloped (sd), dachs (d), and yorkie (yki) were identified from the WBPH genome and their roles in wing development assessed following RNA interference (RNAi)-mediated knockdown. At 5 days-post injection, transcript levels for all five targets were substantially decreased compared with the dsGFP control group. Among the treatment groups, those injected with dsSfarm had the most pronounced effects on transcript reduction, mortality (95 ± 3%), and incidence (45 ± 3%) of wing deformities, whereas those injected with dsSfyki had the lowest incidence (6.7 ± 4%). To assess the utility of topical RNAi for Sfarm, we used a spray-based approach that complexed a large-scale, bacteria-based double-stranded RNA (dsRNA) expression pipeline with star polycation (SPc) nanoparticles. Rice seedlings infested with third and fourth instar nymphs were sprayed with SPc-dsRNA formulations and RNAi phenotypic effects were assessed over time. At 2 days post-spray, Sfarm transcript levels decreased by 86 ± 9.5% compared with dsGFP groups, and the subsequent incidences of mortality and wing defects were elevated in the treatment group., Conclusions: This study characterized five genes in the WBPH developmental signaling cascade, assessed their impact on survival and wing development via RNAi, and developed a nanoparticle-dsRNA spray approach for potential field control of WBPH. © 2023 Society of Chemical Industry., (© 2023 Society of Chemical Industry.)