Chitin synthase 1 (CHS1) is an essential gene regulating chitin during different developmental stages of arthropods. In the current study, we explored for the first time the role of CHS1 gene regulation in the citrus red mite, Panonychus citri (McGregor) (Acari: Tetranychidae), by silencing its expression using (RNA interference) RNAi-based strategies. The results reveal that P. citri tested in different developmental stages, including larvae, protonymphs, deutonymphs, and adults fed on sweet orange leaves dipped in various concentrations (200, 400, 600, and 800 ng/μL) of dsRNA-PcCHS1, resulted in a continuous reduction in their gene expression, and the extent of transcript knockdown was positively correlated with the concentration of dsRNA. Concentration-mortality response assays revealed a mortality of more than 50% among all the studied developmental stages, except for adulthood. Furthermore, the target gene dsRNA-PcCHS1 treatment of larvae, protonymphs, deutonymphs, and females at a treatment rate of 800 ng/mL of dsRNA significantly decreased the egg-laying rates by 48.50%, 43.79%, 54%, and 39%, respectively, and the hatching rates were also considerably reduced by 64.70%, 70%, 64%, and 52.90%, respectively. Moreover, using the leaf dip method, we found that the RNA interference effectively reduced the PcCHS1 transcript levels by 42.50% and 42.06% in the eggs and adults, respectively. The results of this study demonstrate that the RNAi of PcCHS1 can dramatically reduce the survival and fecundity of P. citri, but the dsRNA concentrations and developmental stages can significantly influence the RNAi effects. These findings indicate the potential utility of the PcCHS1 gene in causing developmental irregularities, which could aid in the development of effective and novel RNAi-based strategies for controlling P. citri.
Keywords: RNAi; chitin regulation; citrus red mites; dsRNA; egg-hatch viability; infertility; parental RNAi; sterility.