Knockdown of Sec1/Munc18 (SM) family genes impairs feeding and molting in Locusta migratoria

Sec1/Munc18 (SM) family proteins are conserved in eukaryotic cells and play an active role during membrane fusion. Previous functional studies on SM genes in insects were mainly conducted in holometabolous insects, although current knowledge of SM gene function in hemimetabolous insects is unclear.

In this paper, five complementary DNA sequences of SM genes (LmRop, LmSly1, LmVps45, LmVps33a, and LmVps33b) were identified in Locusta migratoria. Injecting double-stranded (ds)RNA against these genes into fifth-instar nymphs resulted in various degrees of mortality. Nymphs injected with dsLmRop or dsLmSly1 ceased feeding, lost body weight and 100% died before molting. LmRop exhibited predominant expression in the foregut, followed by the hindgut and integument. Hematoxylin and eosin staining further showed severe damage to cells of the foregut, with the cuticle and muscle of the foregut, and microvilli of the midgut and gastric cecum destroyed after silencing LmRop. In addition, no apolysis occurred in the integument of insects treated with dsLmRop. LmSly1 was predominately expressed in the integument, with relative higher expression in the foregut and hindgut. Furthermore, both the synthesis of new cuticle and degradation of the old cuticle were blocked in dsLmSly1-injected insects. In addition, the microvilli of the midgut and gastric cecum disappeared in some regions, and slightly thinner muscle was found in the foregut of dsLmSly1-treated insects.

In short, our results showed that knockdown of LmRop and LmSly1 led to abnormalities in digestion and molting of locusts. Therefore, these two SM genes have promise as key targets for RNA interference-based control of L. migratoria. © 2025 Society of Chemical Industry.