Targeting Syntaxin 1A via RNA interference inhibits feeding and midgut development in Locusta migratoria

Syntaxin 1A (Syx1A) has diverse and indispensable functions in animals. Previous studies have mainly focused on the roles of Syx1A in Drosophila, and so how Syx1A operates during the development of other insects remains poorly understood. This study investigated whether disrupting LmSyx1A using RNA interference (RNAi) affects the growth and development of Locusta migratoria. LmSyx1A was expressed in all tissues tested, with the highest expression observed in the fat body. After 5th-instar nymphs were injected with double-stranded LmSyx1A (dsLmSyx1A), none of the nymphs were able to molt normally and all eventually died. The silencing of LmSyx1A resulted in the cessation of feeding, body weight loss, and atrophy of the midgut and gastric cecum in locusts. Hematoxylin and eosin (H&E) staining showed that the columnar cells in the midgut were severely damaged, with microvilli defects visible in dsLmSyx1A-injected nymphs. Secretory vesicles were observed with transmission electron microscopy (TEM). In addition, reverse transcription quantitative polymerase chain reaction (RT-qPCR) further indicates that silencing LmSyx1A repressed the expression of genes involved in the insulin/mammalian target of rapamycin (mTOR)-associated nutritional pathway. Taken together, these results suggest that LmSyx1A significantly affects the midgut cell layer of locust nymphs, which was partially associated with the downregulation of the insulin/mTOR-associated nutritional pathway. Thus, we argue that LmSyx1A is a suitable target for developing dsRNA-based biological pesticides for managing L. migratoria.