Regulation and synthesis of selected bacteria-induced proteins in Manduca sexta

The levels of different induced immune proteins in feeding larvae peak at different times following induction with bacteria. If induction is within a few days of wandering, relatively high levels of immune proteins, induced in the feeding larval stage, persist into the wandering larva stage. A period exists, during the feeding-larva to wandering larva transition, when the larva are apparently unable to effectively induce the immune proteins; the larvae are unusually susceptible to bacterial attack during this period. The regulation of several proteins, inducible in larvae, is altered; proteins denoted M4 and M11 which are inducible in larvae are constitutively synthesized in wandering larvae, as well as the subsequent prepupal and pupal stages. The detailed protein analysis here has identified a second component of the larva-specific scolexin (formerly denoted M13), tentatively assumed to be an additional subunit or modified form; two other larva-specific, inducible proteins have been identified. Two non-bactericidal inducible proteins, denoted M11 and scolexin, were found to be induced by abdominal ligation; other immune proteins, including those which are bactericidal, were not. Ligation did not, however, interfere with the induction of all the immune complement of proteins when the ligated larvae were injected with bacteria. These data would suggest that the synthesis of some bacteria-induced proteins are also subject to different regulatory stimuli, and permit one to tentatively assume that neither JH or ecdysteroid synthesis is required for induction to take place. In vitro translations with feeding and wandering larval mRNA tend to support earlier data which indicated that the epidermis is the main source of scolexin.