UDP-glycosyltransferase genes and their association and mutations associated with pyrethroid resistance in Anopheles sinensis (Diptera: Culicidae).

backgroundUDP-glycosyltransferase (UGT) is an important biotransformation superfamily of enzymes. They catalyze the transfer of glycosyl residues from activated nucleotide sugars to acceptor hydrophobic molecules, and function in several physiological processes, including detoxification, olfaction, cuticle formation, pigmentation. The diversity, classification, scaffold location, characteristics, phylogenetics, and evolution of the superfamily of genes at whole genome level, and their association and mutations associated with pyrethroid resistance are still little known.

methodsThe present study identified UGT genes in Anopheles sinensis genome, classified UGT genes in An. sinensis, Anopheles gambiae, Aedes aegypti and Drosophila melanogaster genomes, and analysed the scaffold location, characteristics, phylogenetics, and evolution of An. sinensis UGT genes using bioinformatics methods. The present study also identified the UGTs associated with pyrethroid resistance using three field pyrethroid-resistant populations with RNA-seq and RT-qPCR, and the mutations associated with pyrethroid resistance with genome re-sequencing in An. sinensis.

resultsThere are 30 putative UGTs in An. sinensis genome, which are classified into 12 families (UGT301, UGT302, UGT306, UGT308, UGT309, UGT310, UGT313, UGT314, UGT315, UGT36, UGT49, UGT50) and further into 23 sub-families. The UGT308 is significantly expanded in gene number compared with other families. A total of 119 UGTs from An. sinensis, An. gambiae, Aedes aegypti and Drosophila melanogaster genomes are classified into 19 families, of which seven are specific for three mosquito species and seven are specific for Drosophila melanogaster. The UGT308 and UGT302 are proposed to main families involved in pyrethroid resistance. The AsUGT308D3 is proposed to be the essential UGT gene for the participation in biotransformation in pyrethroid detoxification process, which is possibly regulated by eight SNPs in its 3' flanking region. The UGT302A3 is also associated with pyrethroid resistance, and four amino acid mutations in its coding sequences might enhance its catalytic activity and further result in higher insecticide resistance.

conclusionsThis study provides the diversity, phylogenetics and evolution of UGT genes, and potential UGT members and mutations involved in pyrethroid resistance in An. sinensis, and lays an important basis for the better understanding and further research on UGT function in defense against insecticide stress.