TMOF-like factor controls the biosynthesis of serine proteases in the larval gut of Heliothis virescens

Proteolytic enzyme biosynthesis in the midgut of the 4th instar larva of He liothis virescens is cyclical. Protease activity increases immediately afte r the molt from the 3rd to the 4th instar larvae and declines just before t he molt into the 5th instar. Characterization of the midgut proteases using soybean tryspin inhibitor (SBTI) Bowman Birk Inhibitor (BBI) 4-(2-aminoeth yl)benzensulfonylfluoride (AEBSF) and N-tosyl-L-phenylalanine chloromethylk etone (TPCK) indicate that protease activity is mostly trypsinlike (80%) wi th a small amount of chymotrypsinlike activity (20%). Injections of late 3r d and 4th instar larval hemolymph into H. virescens larvae inhibited tryspi n biosynthesis in the larval midgut. Similar results were obtained when hig hly purified 4th instar larval hemolymph that crossreacted with Aea-TMOF an tisurm using ELISA was injected into 2nd instar larvae. Injections of Aea-T MOF and its analogues into 2nd instar, and Aea-TMOF alone into 4th instar l arvae stopped trypsin biosynthesis 24 and 48 h after the injections, respec tively. Injections of 4th instar H. virescens larval hemolymph into female Aedes aegypti that took a blood meal stopped trypsin biosynthesis and egg d evelopment. These results show that the biosynthesis of trypsinlike enzymes in the midgut of a lepidoptera. is modulated with a hemolymph circulating TMOF-like factor that is closely related to Aea-TMOF. Arch. Insect Biochem. Physiol. 47:169-180, 2001. (C) 2001 Wiley-Liss, Inc.