Molecular cloning and characterization of a cDNA encoding a larval cuticle protein of Bombyx mori

Cuticle proteins termed LCPs are the major protein components of the larval integument of the silkworm, Bombyx mori. We purified an 18 kDa LCP (LCP18) from the guanidine hydrochloride extract of the larval cuticle and identified an LCP18 cDNA clone. The deduced primary structure and mRNA expression pattern of LCP18 are similar to those of other Bombyx LCPs and to several cuticle proteins identified in other insect species. RNA blot analysis demonstrated that the biosynthesis of LCP18 is regulated in a stage-dependent manner at the level of mRNA in epidermal cells. An in vivo study using a juvenile hormone analogue suggested that juvenile hormone positively regulates expression of LCP18 mRNA during larval intermolt stages.