BackgroundRNA interference (RNAi) is an effective tool to examine the function of individual genes. Carboxylesterases (CarE, EC 3.1.1.1) are known to play significant roles in the metabolism of xenobiotic compounds in many insect species. Previous studies in our laboratory found that CarE expression was up-regulated in Aphis gossypii (Glover) (Hemiptera: Aphididae) adults of both omethoate and malathion resistant strains, indicating the potential involvement of CarE in organophosphorus (OP) insecticide resistance. Functional analysis (RNAi) is therefore warranted to investigate the role of CarE in A. gossypii to OPs resistance.Result CarE expression in omethoate resistant individuals of Aphis gossypii was dramatically suppressed following ingestion of dsRNA-CarE. The highest knockdown efficiency (33%) was observed at 72 h after feeding when dsRNA-CarE concentration was 100 ng/µL. The CarE activities from the CarE knockdown aphids were consistent with the correspondingly significant reduction in CarE expression. The CarE activity in the individuals of control aphids was concentrated in the range of 650–900 mOD/per/min, while in the individuals of dsRNA-CarE-fed aphids, the CarE activity was concentrated in the range of 500–800 mOD/per/min. In vitro inhibition experiments also demonstrated that total CarE activity in the CarE knockdown aphids decreased significantly as compared to control aphids. Bioassay results of aphids fed dsRNA-CarE indicated that suppression of CarE expression increased susceptibility to omethoate in individuals of the resistant aphid strains.ConclusionThe results of this study not only suggest that ingestion of dsRNA through artificial diet could be exploited for functional genomic studies in cotton aphids, but also indicate that CarE can be considered as a major target of organophosphorus insecticide (OPs) resistance in A. gossypii. Further, our results suggest that the CarE would be a propitious target for OPs resistant aphid control, and insect-resistant transgenic plants may be obtained through plant RNAi-mediated silencing of insect CarE expression.

Due to the application prospect in wearable field, flexible conductive hydrogel sensors have attracted a lot of attention owing to their stretchability, sensitivity, self-repairing capacity and excellent compatibility. However, most...

The mycotoxin zearalenone (ZEN) is a secondary metabolite produced mainly by Fusarium species. ZEN poses health hazards both for humans and animals, as a major contaminant in the food and feed industries. Currently, there is no effective technique for degrading ZEN during industrial processes. In this study, we isolated and biochemically characterized a novel lactone hydrolase, ZHD607, isolated from Phialophora americana, cloned, and exogenously expressed in Pichia pastoris. ZHD607 was characterized as a mesophilic lactone hydrolase having a neutral pH and showing optimal activity at 35 °C and pH 8.0. Two mutants, ZHDM1 and I160Y, generated from ZHD607 based on structure and sequence alignment analyses, exhibited 2.9-and 3.4-fold higher activity towards ZEN than did ZHD607. Molecular dynamics simulation revealed diverse mechanisms driving this improved catalytic activity. These findings enrich our knowledge about ZHD enzyme family and represent an important step toward industrialization of ZEN-detoxifying lactone hydrolases.