| Summary: | 碩士 === 東海大學 === 生命科學系 === 99 === Unpaired3 (Upd3) is a ligand of Janus Kinase/ Signal Transducers and Activators of Transcription (Jak/STAT) signaling in Drosophila. upd3 takes part in eye, gonad, haematopoiesis and immune response. upd3 is expressed in eye-antenna disc, gonad in the larval stages and testis in adult. The upd3 null mutant is fertile and viable with small eye. Upd3 regulates hemocyte differentiation to maintain homeostasis of hemolymph in the larval stages. upd3 is induced after septic injury or oral infection in midgut to maintain homeostasis of intestine in the larval stage. The appropriate regulation of ligands temporally and spatially is required to activate Jak/STAT signaling to control multiple developmental processes. In this study, I focus on the transcriptional regulation of the upd3 gene and further study the upstream signaling of the upd3 gene. I analyzed the upd3 enhancers in vivo. The 17.8Kb genomic regions around the upd3 gene, designed as 17 constructs, were analyzed. These upd3 genomic fragments were cloned to enhancer-testing vector, pH-Stinger, which contains a GFP reporter. The enhancer-testing constructs were injected into Drosophila and then selected for transgenic lines. The expression pattern of GFP reporter was examined in vivo. I found a possible 1.2Kb upd3 enhancer, M fragment. M fragment locates at 1.8Kb downstream of the upd3 gene. It may regulate eye, intestine cells, posterior signaling center (PSC) in lymph gland and hub in testis. I narrowed down this enhancer fragment and found a smaller fragment, M1, which can express the upd3 gene in the stem cell niche of gonad and lymph gland in Drosophila. To understand the upstream signaling of the upd3 gene, I predicted the possible transcriptional factor binding sites. I found multiple Suppressor of Hairless (Su(H)), STAT92E and AP-1 binding sites in 17.8Kb genomic regions of the upd3 gene. There are two Su(H) and two STAT92E binding sites in the possible 0.8Kb upd3 enhancer fragment (M1 fragment). The M1 fragment may regulate upd3 transcription through Notch signaling and Jak/STAT signaling. Based on my study, I found a minimal fragment can express the upd3 gene in the stem cell niche of gonad and lymph gland in Drosophila. The discovery of 0.8 Kb DNA fragment may help us to understand the roles of the upd3 gene in the male gonad and lymph gland development in Drosophila.
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