Hypertrehalosemic hormone effects on transcriptional activity in the fat body of the cockroach, Blaberus discoidalis.

Gene expression was examined in the fat body of adult male Blaberus discoidalis cockroaches in response to the hypertrehalosemic hormone (HTH). HTH regulates a natural peak of heme synthesis in the fat body at day 4 of adult life. Inhibition of transcriptional activity by alpha-amanitin suppressed both the natural increase in heme biosynthesis at day 4, and the increase that was induced in decapitated animals by HTH administration. In contrast, the regimen of alpha-amanitin treatments that suppressed HTH-responsive heme biosynthesis had no effect on the ability of HTH to increase hemolymph carbohydrate. HTH administration to decapitated animals produced a 25% increase in total fat body RNA and a 3-fold increase in [3H]uridine incorporation. In vitro translation of fat body RNA showed that HTH increased the synthesis of polypeptides at 24, 60 and 77 kDa. The results suggest that HTH affects fat body heme synthesis through gene expression, and evidence was obtained for three polypeptides that increase in the fat body in response to HTH.