Chasan R, Anderson K V
Department of Molecular Biology, University of California, Berkeley 94720.
Cell. 1989 Feb 10;56(3):391-400. doi: 10.1016/0092-8674(89)90242-0.
The maternally transcribed product of the Drosophila easter gene is essential for the establishment of a normal dorsal-ventral pattern in embryos. Loss-of-function mutations in easter result in a dorsalization of the embryonic pattern, while dominant gain-of-function mutations ventralize the embryonic pattern. P element insertion alleles of easter were isolated and used to identify genomic and cDNA clones that include the easter gene. Injection of in vitro-synthesized transcripts of the cDNA into embryos from easter mutant females completely rescued the mutant phenotype, allowing normal development. This result confirmed that the cDNA encodes easter and that the easter product is only required after fertilization. The sequence of the cDNA suggests that the product of the easter gene is an extracytoplasmic serine protease. The implications of the dominant alleles of this putative protease for the mechanism of dorsal-ventral pattern formation are discussed.
果蝇easter基因由母体转录的产物对于胚胎中正常背腹模式的建立至关重要。easter基因功能缺失突变会导致胚胎模式背化，而显性功能获得性突变则会使胚胎模式腹化。分离出easter基因的P因子插入等位基因，并用于鉴定包含easter基因的基因组和cDNA克隆。将体外合成的cDNA转录本注射到easter突变雌性的胚胎中，完全挽救了突变表型，使胚胎能够正常发育。这一结果证实该cDNA编码easter基因，且easter基因产物仅在受精后才是必需的。cDNA序列表明，easter基因的产物是一种胞外丝氨酸蛋白酶。文中讨论了这种假定蛋白酶的显性等位基因对背腹模式形成机制的影响。
