New insights for Drosophila GAGA factor in larvae

GAGA factor plays important roles during Drosophila embryogenesis and its maternal contribution is essential for early development. Here, the role of GAGA factor was studied in 3rd instar larvae using depletion and overexpression conditions in wing disc and transcriptome analysis. We found that genes changing expression were different to those previously described using GAGA mutants in embryos. No apparent phenotypes on GAGA depletion could usually be observed at larval stages in imaginal discs but a strong effect on salivary gland polytene chromosomes was observed. In the adult, GAGA depletion produced many defects like abnormal cell proliferation in the wing, impaired dorsal closure and resulted in homeotic transformation of abdominal segment A5. Unexpectedly, no effects on Ultrabithorax expression were observed. Short overexpression of GAGA factor in 3rd instar larvae also resulted in activation of a set of genes not previously described to be under GAGA regulation, and in lethality ...GAGA因子（GAGA factor）在果蝇（Drosophila）胚胎发生过程中发挥关键作用，其母源贡献对早期发育至关重要。本研究以三龄幼虫的翅盘（wing disc）为研究对象，通过基因敲低与过表达体系结合转录组分析（transcriptome analysis），探究了GAGA因子的生物学功能。研究发现，本研究中表达发生改变的基因，与此前通过胚胎时期GAGA突变体（GAGA mutants）得到的差异基因存在显著差异。在幼虫阶段的成虫盘（imaginal discs）中，通常难以观测到GAGA敲低引发的明显表型，但在唾液腺多线染色体（salivary gland polytene chromosomes）中却能检测到显著影响。在成虫体内，GAGA敲低会引发多种发育缺陷：包括翅部细胞增殖异常、背闭合受损，以及腹部体节A5发生同源异型转化。令人意外的是，本研究未观测到对超胸基因（Ultrabithorax）表达的调控效应。在三龄幼虫中短时过表达GAGA因子，同样会激活一批此前未被报道受GAGA因子调控的基因，并最终导致个体致死……