DEVELOPMENTAL ROLE OF JUVENILE-HORMONE METABOLISM IN LEPIDOPTERA

Lepidopteran juvenile hormone (JH) esterase appears to have a function al role in the regulation of embryogenesis, larval growth and developm ent, and adult reproduction. In preovipositional and newly laid eggs o f the tobacco hornworm, Manduca sexta, JH esterase activity was elevat ed presumably to metabolize maternal JHs, and then declined after blas toderm formation. Also, a single peak in hemolymph JH esterase activit y was found prior to ecdysis in the second through the fourth instar o f M. sexta, the function of which is unclear. However, in the last ins tar, elevated hemolymph JH esterase activity was noted prior to wander ing and again prior to ecdysis to scavenge the last traces of JH neces sary for normal development. The hemolymph JH esterase is likely of mu ltiple tissue origin for the prewandering peak with the fat body exclu ded as a source for the prepupal peak; an inhibitory factor from the b rain and JH regulate JH esterase biosynthesis. In adult cabbage looper s, Trichoplusia ni, elevated hemolymph JH esterase activity appeared t o 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 hy drate of octylthio-1,1,1-trifluoropropan-2-one, with selective and per sistent, in vivo inhibitory activity. The topical application of this compound to last instar larvae and virgin adults of T. ni produced juv enizing effects (delayed pupation and induced egg maturation/ovipositi on, respectively) providing direct evidence of a functional role for J H esterase in lepidopteran development.