The full cDNA of chitinase gene (LmChi) from the midgut of Locusta migratoria manilensis (Meyen) was cloned by means of 3′-RACE and 5′-RACE. The results showed that the cDNA was 1 604 bp in length and contained an open reading frame (ORF) of 1 452 bp (GenBank accession number: EF092841), which encoded 483 amino acids. The deduced amino acid sequence, which was composed of a signal peptide, a chitinase active site, a C-terminal serine-rich region and a domain normal present in chitinase, showed a high similarity with other insect chitinases from family 18. Semi-quantitative RT-PCR indicated that LmChi expressed only in the midgut, but not in the integument, foregut and hindgut of L. migratoria manilensis.

Molting is required for progression between larval stages in the life cycle of an insect. The essence of insect molting is the laying down of new cuticle followed by shedding of the old cuticle. Degradation and recycling of old cuticle are brought about by enzymes present in the molting fluid, which fills the space between the old and new cuticle. Here, we describe the cloning of a novel protease gene from Locusta migratoria manilensis, designated as Lm-TSP. The cDNA and its deduced protein sequences were deposited in GenBank (accession numbers EF081255 and ABN13876, respectively). Sequence analysis indicated that Lm-TSP belongs to the trypsin-like serine protease family. We show, by RNA interference (RNAi), that silencing of Lm-TSP leads to dramatic reductions in protease and cuticle-degrading activity of a molting fluid, which leads to molting defects from fourth-instar larvae (L4) to fifth-instar larvae (L5), and between L5 and adult stages. These observations suggest that Lm-TSP plays a critical role in L. migratoria manilensis ecdysis.