Effects of exposure to three acaricides on the expression of TtABCB and TtABCG genes in Tetranychus truncatus

Tetranychus truncatus is one of the major pests on maize and other crops, and it has developed resistance to numerous pesticides, which makes its control more difficult. ATP-binding cassette (ABC) transporters, a ubiquitous transmembrane protein superfamily in organisms, play crucial roles in detoxification by the transmembrane transport of endogenous and exogenous substrates. In this study, we systematically screened ABC transporter genes of adult maites T. truncatus and made a phylogenetic analyses. In addition, the toxicity of abamectin, propargite and bifenazate to T. truncatus at different exposure durations was evaluated. RT-qPCR was used to evaluate the expression profiles of two ABC transporter subfamilies, TtABCB and TtABCG, at different developmental stages of female adults (eggs, larvae, nymphs and adults) and their transcription responses to the three acaricides. The results showed that 62 ABC transporter genes were identified from the transcriptome data of T. truncatus. According to phylogenetic analysis and conserved domain analysis, these genes were classified into eight subfamilies(named TtABCA~TtABCH). Among them, TtABCB and TtABCG subfamilies were expressed at all developmental stages of T. truncatus (egg, larva, nymph, and adult), but the relative expression levels were different at developmental stages. When female adult mites of T. truncatus were treated at 24 h and 48 h, the toxicity ranking was abamectin > bifenazate > propargite.), while at 72 hours, the toxicity of propargite was higher than that of bifenazate (abamectin > propargite > bifenazate). Four genes (TtABCB1, TtABCB3, TtABCB4 and TtABCG1 4) up-regulated significantly when exposed to all three acaricides, indicating that T. truncatus might up-regulated these four genes in response to the stress of these three acaricides, where TtABCB3 and TtABCG1 could be involved in the detoxification metabolism of T. truncatus to the three acaricides. These findings provide important insights for screening targeted resistance genes and integrated pest management of T. truncatus.