The role of allatostatic and allatotropic neuropeptides in the regulation of juvenile hormone biosynthesis in Lacanobia oleracea (Lepidoptera : Noctuidae)

In the sphinghid moth Manduca sexta, two allatoactive neuropeptides: appear to be responsible for regulating juvenile hormone (JH) production by the c orpora allata (CA). These peptides (M. sexta allatostatin, Mas-AS, and M. s exta allatotropin. Mas-AT) respectively inhibit and stimulate in vitro JH b iosynthesis by CA in this insect. However, although Mas-AS inhibits CA in b oth larval and adult insects, Mas-AT is active only in adult M. sexta. The situation in other lepidopteran species is less clear-cut and. although bot h peptides have been detected (usually by immunologic and/or molecular tech niques) in several other moths (including noctuids), their function as regu lators of JH production remains uncertain. In the tomato moth Lacanobia ole racea (Lepidoptera: Noctuidae), we have previously demonstrated the occurre nce of Mas-AS and/or Mas-AT in extracts of CA. brain and other organs, and have shown that both peptides are present in larval and adult forms. Howeve r, in L. oleracea, although Mas-AS inhibits larval and adult CA in vitro, i t does so only at relatively high concentrations, and to a maximum of only similar to 70%. By contrast. Mas-AT (which is also present in larval and ad ult L. oleracea stimulates larval and adult CA, but is substantially more p otent (similar to 100 fold) than the allatostatin. In this paper we present the results of paired, concurrent measurements (using ELISA) of levels of Max-AS and Mas-AT in brains, CA and hemolymph (plasma and hemocytes) of L. oleracea at times when there are marked changes in JH titers. We also prese nt data on the in vitro rates of JH biosynthesis: by isolated CA, and on he molymph JH esterase activity measured at the same critical developmental ri mes, and discuss all of these data in relation to the putative allatoregula tory rules of the M. sexta allatotropic and allatostatic neuropeptides in L . oleracea. (C) 2001 Elsevier Science Inc. All rights reserved.