Follicle Cell Calmodulin in Blattella germanica: Transcript Accumulation during Vitellogenesis Is Regulated by Juvenile Hormone

Abstract

There is abundant calmodulin (CaM) in the oocytes and eggs of B. germanica . Whether oocytes accumulate CaM for immediate use or use at a later stage in their development is still unknown. We show that isolated follicle cells accumulate more CaM transcripts per unit RNA than any other control tissue. CaM transcript increases exponentially 4800-fold in follicles during the 96-hr viteliogenic period in the absence of cell division. This includes a 32-fold increase in total follicle RNA during the period and an 150-fold increase in relative titer of the CaM transcript. In comparison, levels of actin transcripts increase exponentially 1200-fold during the same developmental period. On the other hand fat body tissue shows little relative increase of CaM transcripts despite a 4-fold increase in total RNA over the 4-day developmental period. Both the CaM and actin transcripts are more highly concentrated in the Day 4 follicle cell layer, being found in 84- and 33-fold greater titer, respectively, than in fat body RNA. Deprivation of juvenile hormone (JH), by head ligation, not only causes atresia of the follicles, but also reduces accumulated CaM transcripts. Reestablishing JH titer by injection allows a selected population of follicles to develop to full size and also reinstates CaM transcript levels above that of unligated controls within 24 hr.