Diaphorina citri Kuwayama is the vector of citrus “huanglongbing”, a citrus disease which poses a significant threat to the global citrus industry. Trehalose-6-phosphate synthase (TPS) plays an important role in the regulation of trehalose levels of insects, while its functions in D. citri are unclear. In this study, full-length cDNA sequences of the TPS gene from D. citri (DcTPS) were cloned and its expression patterns at various developmental stages were investigated. The results indicated that DcTPS mRNA was expressed at each developmental stage and the highest DcTPS expression was found in the fifth-instar nymphs of D. citri. Additionally, mortality and deformity of D. citri were observed after 24 and 48 h by feeding with three different dsRNA concentrations (20, 100 and 500 ng/μL). The results indicated that DcTPS expression was declined, and mortality and malformation in nymphs were increased via feeding with dsDcTPS. Moreover, the enzyme and trehalose content were decreased, while the content of glucose was significantly higher than that of untreated (control) individuals. This suggests that DcTPS might be vital for the growth and development of D. citri and further studies of the genes should be related to molting and metabolism for controlling D. citri.

The carmine spider mite, Tetranychus cinnabarinus (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 T. cinnabarinus responds to insecticide exposure, we identified the chitin synthase 1 gene (TcCHS1) and then explored the gene expression levels of TcCHS1 at different developmental stages of T. cinnabarinus. We also investigated the effects of sublethal concentrations of diflubenzuron on the toxicities and survivals of T. cinnabarinus eggs and larvae as well as TcCHS1 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 T. cinnabarinus 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 T. cinnabarinus revealed that TcCHS1 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 T. cinnabarinus. The mRNA expression levels of TcCHS1 from the eggs and larvae of T. cinnabarinus were up-regulated in response to sublethal concentrations of diflubenzuron exposures. Together, all these results demonstrate that diflubenzuron has ovicidal and larvicidal effects and TcCHS1 may play an important role in the growth and development of T. cinnabarinus and may disrupt the chitin biosynthesis, thereby controlling T. cinnabarinus populations.

Grain contaminated by cadmium (Cd) has become a serious food security problem, and it is necessary to determine and evaluate the toxic effect and defense mechanism of long-term heavy metal pollution in grain. In order to evaluate the effects of long-term heavy metal Cd stress on the stored grain pests, Aleuroglyphus ovatus were fed with an artificial diet supplemented with different concentrations of Cd (0, 5, 10, 20 mg/kg). The development, fecundity and detoxification enzymes of A. ovatus were analyzed and observed. In this study, the immature duration of A. ovatus was significantly prolonged under long-term Cd stress. Moreover, the survival duration of female adults was significantly shortened. The total number of eggs laid and the daily number laid per female adult decreased significantly. There were significant differences in protein content at protonymph and tritonymph stages when the concentration of Cd exceeded 10 mg/kg. The protein content of female adults was higher than that of male adults. The activity of detoxification enzymes showed differences in different conditions, such as development stage, Cd concentration and gender. These findings confirmed that A. ovatus were sensitive to Cd, and their offspring were severely affected under long-term Cd stress. Therefore, A. ovatus is a good model for evaluating the toxicity of long-term heavy metal Cd stress. The study provides the basis and enriches the research content of heavy metal pollution on mites, contributing to the harmonious and healthy development between the environment and human beings.