Developmental Role of Juvenile Hormone Metabolism in Lepidoptera

SYNOPSIS. Lepidopteran juvenile hormone (JH) esterase appearsto have a functional role in the regulation of embryogenesis,larval growth and development, and adult reproduction. In preovipositionaland newly laid eggs of the tobacco hornworm, Manduca sexta,JH esterase activity was elevated presumably to metabolize maternalJHs, and then declined after blastoderm formation. Also, a singlepeak in hemolymph JH esterase activity was found prior to ecdysisin the second through the fourth instar of M. sexta, the functionof which is unclear. However, in the last instar, elevated hemolymphJH esterase activity was noted prior to wandering and againprior to ecdysis to scavenge the last traces of JH necessaryfor normal development. The hemolymph JH esterase is likelyof multiple tissue origin for the prewandering peak with thefat body excluded as a source for the prepupal peak; an inhibitoryfactor from the brain and JH regulate JH esterase biosynthesis.In adult cabbage loopers, Trichoplusia ni, elevated hemolymphJH esterase activity appeared to be important in reducing theJH titer and preventing egg maturation. Structure/activity datawith trifluoromethylketones were incorporated into the designof a novel, JH esterase inhibitor, the sulfone and hydrate ofoctylthio-1,1,1- trifluoropropan-2-one, with selective and persistent,in vivo inhibitory activity. The topical application of thiscompound to last instar larvae and virgin adults of T. ni producedjuvenizing effects (delayed pupation and induced egg maturation/oviposition,respectively) providing direct evidence of a functional rolefor JH esterase in lepidopteran development.