Regulation of serpin gene-1 in Manduca sexta

Hemolymph of Manduca sexta contains proteins from the serpin superfamily, which are inhibitors of serine proteinases. We have used probes specific for M. sexta serpin gene-1 mRNA and protein to study the expression and hormonal regulation of this gene. Serpin gene-1 is expressed at a high level in larval fat body and at a lower abundance in hemocytes, where serpin protein is localized in the granules of granular cells. Serpin gene-1 mRNA is abundant in the fat body of feeding fourth and fifth instar larvae, but disappears abruptly at molts and at the wandering stage. The concentration of serpin proteins in hemolymph during development is correlated with the abundance of serpin mRNA in fat body. Results of in vivo and in vitro experiments indicate that 20-hydroxyecdysone has a role in negative regulation of serpin gene-1.