Developmental Role of Juvenile Hormone Metabolism in Lepidoptera

Abstract

SYNOPSIS. Lepidopteran juvenile hormone (JH) esterase appears to have a functional role in the regulation of embryogenesis, larval growth and development, and adult reproduction. In preovipositional and newly laid eggs of the tobacco hornworm, Manduca sexta , JH esterase activity was elevated presumably to metabolize maternal JHs, and then declined after blastoderm formation. Also, a single peak in hemolymph JH esterase activity was found prior to ecdysis in the second through the fourth instar of M. sexta , the function of which is unclear. However, in the last instar, elevated hemolymph JH esterase activity was noted prior to wandering and again prior to ecdysis to scavenge the last traces of JH necessary for normal development. The hemolymph JH esterase is likely of multiple tissue origin for the prewandering peak with the fat body excluded as a source for the prepupal peak; an inhibitory factor from the brain and JH regulate JH esterase biosynthesis. In adult cabbage loopers, Trichoplusia ni , elevated hemolymph JH esterase activity appeared to be important in reducing the JH titer and preventing egg maturation. Structure/activity data with trifluoromethylketones were incorporated into the design of a novel, JH esterase inhibitor, the sulfone and hydrate of octylthio-1,1,1- trifluoropropan-2-one, with selective and persistent, in vivo inhibitory activity. The topical application of this compound to last instar larvae and virgin adults of T. ni produced juvenizing effects (delayed pupation and induced egg maturation/oviposition, respectively) providing direct evidence of a functional role for JH esterase in lepidopteran development.