The Role of the Caspase Dronc in Fat Body Remodeling in Drosophila melanogaster
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Date
2013-05-18
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Abstract
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.
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Keywords
Dronc, fat body remodeling, cell death, caspases, ecdysone