BACKGROUND Carboxyl/cholinesterases (CCEs) are thought to play a pivotal role in the degradation of sex pheromones and plant‐derived odorants in insects, but their exact biochemistry and physiological functions remain unclear. RESULTS In this study, two paralogous antennae‐enriched CCEs from Plutella xylostella (PxylCCE16a and 16c) were identified and functionally characterized. High‐purity protein preparations of active recombinant PxylCCE16a and 16c have been obtained from Sf9 insect cells by Ni2+ affinity purification. Our results revealed that the purified recombinant PxylCCE016c is able to degrade two sex pheromone components Z9‐14:Ac and Z11‐16:Ac at 27.64 ± 0.79% and 24.40 ± 3.07%, respectively, while PxylCCE016a presented relatively lower activity. Additionally, a similar difference in activity was measured in plant‐derived odorants. Furthermore, both CCEs displayed obvious preferences for the two sex pheromone components, especially on Z11‐16:Ac (Km values are in the range 7.82–45.06 μmol L–1) which much lower than plant odorants (Km values are in the range 1290–4030 μmol L–1). Furthermore, the activity of the two newly identified CCEs is pH‐dependent. The activity at pH 6.5 is obviously higher than that at pH 5.0. Interestingly, only PxylCCE016c can be inhibited by a common esterase inhibitor triphenyl phosphate (TPP) with LC50 of 1570 ± 520 μmol L–1. CONCLUSION PxylCCE16c plays a more essential role in odorant degradation than PxylCCE16a. Moreover, the current study provides novel potential pesticide targets for the notorious moth Plutella xylostella. © 2021 Society of Chemical Industry

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BACKGROUND: Epidermal growth factor receptor (EGFR), zinc finger homeodomain-2 (zfh-2), Abdominal-A (Abd-A), and Abdominal-B (Abd-B) regulate the growth and development of the insect abdomen. However, their potential roles in pest control have not been fully assessed. The development of insecticide resistance to multiple chemistries in the white-backed planthopper (WBPH), a major pest of rice, has prompted interest in novel pest control approaches that are ecologically friendly. Although pest management approaches based on double-stranded RNA (dsRNA)-mediated RNA interference (RNAi) have potential, their susceptibility to degradation limits large-scale field applications. These limitations, however, can be overcome with nanoparticle-dsRNA complexes that have greater environmental stability and improved cellular uptake.RESULTS: In this study, at 5 days post-injection, transcripts for the four gene targets were reduced relative to controls and all of the experimental groups exhibited significant phenotypic defects and increased mortality. To evaluate the potential of these gene targets for field applications, a nanocarrier-dsRNA spray delivery system was assessed for RNAi efficacy. At 11 days post-spray, significant phenotypic defects and increased mortality were observed in all experimental groups. CONCLUSION: Taken together, the results confirm the suitability of the target genes (SfEGFR, Sfzfh-2, SfAbd-A, and SfAbd-B) for pest management and demonstrate the efficacy of the nanocarrier spray system for inducing RNAi-mediated knockdown. As such, the study lays the foundation for the further development and optimization of this technology for large-scale field applications.

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.

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