IP Integument

Hormonal regulation of cuticle formation and chitin synthesis

A. Retnakaran 1, W. Tomkins 1, M. Primavera 1, T. Ladd 1, Q.-L. Feng 1, B. M. Arif 1 and S.R. Palli 1,2

1 Great Lakes Forestry Centre, Canadian Forest Service, P.O. Box 490, Sault Ste. Marie, Ontario, Canada, P6A 5M7; 2 Rohm and Haas Research Laboratories, 727 Norristown Road, Spring House, Penn., 19477, USA

Cuticle formation, chitin synthesis and endocuticular elaboration occur during the inter-molt period early in each stadium prior to the appearance of the ecdysone peak in the hemolymph. The formation of the cuticulin layer, dense epicuticle and the secretion of the molting fluid are up-regulated by ecdysone whereas sclerotization, chitin synthesis, endocuticular elaboration and ecdysis are down-regulated by this hormone. Juvenile hormone modulates the effects of ecdysone and alteration of its titer leads to phenotypic changes in the cuticle. Structural and sclerotization genes such as LCP-14 and DDC are expressed in the absence of ecdysone whereas molt genes such as the transcription factors E75 and CHR3 that transactivate genes responsible for the molting fluid, cuticulin, epicuticle and ecdysis are expressed in the presence of ecdysone. Elucidation of the molecular regulatory mechanism and ultrastuctural changes in cuticle morphogenesis using a non-steroidal ecdysone agonist, RH-5992, in the spruce budworm, Choristoneura fumiferana, will be described.

Key Words: Cuticle, Chitin, Ecdysone, Sclerotization, Juvenile hormone, Transcription factors, RH-5992, Choristoneura fumiferana

Copyright: Session 13 – INSECT PHISIOLOGY, NEUROSCIENCES, IMMUNITY AND CELL BIOLOGY Symposium and Poster Session, ABSTRACT BOOK II – XXI-International Congress of Entomology, Brazil, August 20-26, 2000