Knockdown of farnesyl pyrophosphate synthetase gene TuFPPS by RNAi extends quiescent period and halts molting of the spider mite, Tetranychus urticae

Farnesyl pyrophosphate synthase (FPPS) is crucial in the juvenile hormone (JH) biosynthesis pathway in insects, particularly regulating the molting process. However, its role in the post-embryonic development and molting of spider mites remains unclear. This study investigated the function of TuFPPS in the deutonymphal stage of the two-spotted spider mite, Tetranychus urticae, an important pest in agriculture. The expression pattern of TuFPPS demonstrated that its transcript level was increased significantly in the middle of the quiescent period (28 h). Knockdown of TuFPPS by RNAi caused a delay of development with a marked extension of the quiescent period, and the molting process was delayed. Ultimately, the treated mites failed to molt and died with 80% mortality at 108 h before molting, while >90% of the mites in the control had successfully molted. To investigate potential functions of TuFPPS in the quiescent period and molting process of T. urticae, we performed a genome-wide RNA sequencing analysis following RNAi-mediated knockdown of TuFPPS. Four genes were selected based on the thresholds. These genes, which are involved in carbohydrate metabolism, fatty acid and lipid metabolism, amino acid metabolism and ABC transporters, were affected. Taken together, our data suggest that TuFPPS plays an important role in regulating the energy transport, intracellular digestion and energy supply as is the case with ametabolous insects, which in turn lays a foundation for the study of the molecular mechanism of JH/MF (methyl farnesoate) in the post-embryonic development and molting of mites, and also provides a potential target for their control, exemplified here with T. urticae.