Hormonal regulation and patterning of the Broad-Complex in the epidermis and wing discs of the tobacco hornworm, Manduca sexta

Expression of manduca Broad-Complex (BR-C) mRNA in the larval epidermis is under the dual control of ecdysone and juvenile hormone (TH). Immunocytoche mistry with antibodies that recognize the core, Z2, and Z4 domains of Mandu ca BR-C proteins showed that BR-C appearance not only temporally correlates with pupal commitment of the epidermis on day 3 of the fifth (final) larva l instar, but also occurs in a strict spatial pattern within the abdominal segment similar to that seen for the loss of sensitivity to TH. Levels of Z 2 and Z4 BR-C proteins shift with Z2 predominating at pupal commitment and Z4 dominant during early pupal cuticle synthesis. Both induction of BR-C mR NA in the epidermis by 20-hydroxyecdysone (20E) and its suppression by TH w ere shown to be independent of new protein synthesis. for suppression TH mu st be present during the initial exposure to 20E. When TH was given 6 h aft er 20E, suppression was only seen in those regions that had not yet express ed BR-C. In the wing discs BR-C was first detected earlier 1.5 days after e cdysis, coincident with the pupal commitment of the wing. Our findings sugg est that BR-C expression is one of the first molecular events underlying pu pal commitment of both epidermis and wing discs. (C) 2001 Academic Press.