Molecular Characterization of Chitin Synthase Gene in (Boisduval) and Its Response to Sublethal Concentrations of an Insecticide.

The carmine spider mite, (Boisduval), is one of the most important acarine pest species. At present, its control remains primarily dependent on using various chemical insecticides/acaricides in agricultural crops worldwide. To clarify the mechanism whereby responds to insecticide exposure, we identified the chitin synthase 1 gene () and then explored the gene expression levels of at different developmental stages of . We also investigated the effects of sublethal concentrations of diflubenzuron on the toxicities and survivals of eggs and larvae as well as expression levels. The full-length cDNA sequence contains an open reading frame (ORF) of 4881 nucleotides that encoded for a 1474 amino acid residues protein. The predicted TcCHS1 protein had a molecular mass of 168.35 kDa and an isoelectric point of 6.26, and its amino acid sequence contained all the signature motifs (EDR, QRRRW and TWGTR) of chitin synthases. The results of phylogenetic analyses demonstrated that the putative CHS1 amino acid sequence of revealed high similarities with chitin synthases in other insects and mites. Additionally, at the molecular level, transcriptional analysis by real-time quantitative PCR in different developmental stages of revealed that mRNA was expressed in all stages, and highest in eggs and female adults, but lowest in deutonymphs. Furthermore, the results of toxicity bioassays indicated that diflubenzuron treatment resulted in high mortality rates in eggs and larvae of . The mRNA expression levels of from the eggs and larvae of were up-regulated in response to sublethal concentrations of diflubenzuron exposures. Together, all these results demonstrate that diflubenzuron has ovicidal and larvicidal effects and may play an important role in the growth and development of and may disrupt the chitin biosynthesis, thereby controlling populations.