DEVELOPMENT OF GENITAL IMAGINAL DISKS OF HELIOTHIS-VIRESCENS CULTURE INVITRO WITH 20-HYDROXYECDYSONE AND FAT-BODY OR TESTIS SHEATHS

Genital imaginal discs were dissected from Heliothis virescens pupae j ust after diapause break and cultured in vitro. The discs continued to grow and differentiate when maintained in media containing sufficient ly high titers of 20-hydroxyecdysone (20HE) and co-cultured fat body o r testis sheath tissue, or extract of fat body previously exposed to 2 0HE in vitro. Continuous changes were observed for approximately 30 da ys. Other tissues provided only temporary (5-8 day) developmental supp ort. Genetal discs did not develop in the absence of 20 HE. Discs co-c ultured with fat body in 20 HE medium synthesized more protein and DNA than discs co-cultured with fat body but without 20 HE. Fat body and testis sheath tissue, cultured with sufficient titers of 20 HE, produc ed factors essential to the development of genital imaginal discs of H . virescens.