The Role of the Caspase Dronc in Fat Body Remodeling in Drosophila melanogaster



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During metamorphosis in Drosophila melanogaster larval tissues such as salivary glands are eliminated by programmed cell death (PCD). In contrast, the larval fat body evades PCD and undergoes a process of remodeling and dissociation that is completed during the ecdysone-triggered prepupal-pupal transition 10-12 hours after puparium formation (Riddiford, 1993). In response to ecdysone, a cascade involving the induction of the proapoptotic genes hid and ark is activated. In salivary glands, the proapoptotic proteins indirectly activate PCD caspases leading to salivary glands histolysis. Prior to the prepupal ecdysone pulse, the competence factor βftz-f1 gene is expressed and is involved in preparing tissues to appropriately respond to the ecdysone pulse. DRONC, an apoptotic caspase, has been implicated in larval salivary gland PCD. In this study, I hypothesize that fat body evades PCD due to downregulation of Dronc expression compared to salivary glands. I show that Dronc is down-regulated in fat body at 10, 12 and 14 hours APF compared to salivary gland in wild-type animals. I also show that the competence factor βFTZ-F1 upregulates Dronc expression in the fat body, but in less optimal manner that it is in salivary glands. I do this by using cg-Gal4; UAS-dBlimp-1 animals expressing βftz-f1 repressor dBlimp-1.



Dronc, fat body remodeling, cell death, caspases, ecdysone