A midgut-specific chymotrypsin cDNA (Slctlp1) from Spodoptera litura: cloning, characterization, localization and expression analysis.

Serine proteases play important roles in food digestion and immune response during insect development. A full-length cDNA (Slctlp1) encoding a chymotrypsin-like serine protease was cloned from Spodoptera litura and characterized for its cDNA structure, developmental and induced expression and localization. The deduced protein of the Slctlp1 cDNA contains a catalytic triad and a substrate specificity pocket found in most of the serine proteases. Both the transcripts and protein of Slctlp1 were predominately expressed in the midgut at the feeding stages during the larval development. Immunohistochemistry analysis indicated that the SLCTLP1 protein was predominately present in the midgut of the 6th instar feeding larvae. Starvation suppressed the expression of Slctlp1 gene and protein in 6th instar larvae and the protein expression was increased again by re-feeding the insect. The results suggest that the cloned Slctlp1 cDNA may be involved in food protein digestion at the feeding stages during larval development.