Kuo Y M, Jones N, Zhou B, Panzer S, Larson V, Beckendorf S K
Department of Molecular and Cell Biology, Division of Genetics, University of California, Berkeley, 94720, USA.
Development. 1996 Jun;122(6):1909-17. doi: 10.1242/dev.122.6.1909.
Organogenesis in Drosophila embryos begins at 4-5 hours of development as the expression of organ-specific genes is initiated. The salivary primordium, which occupies the ventral epidermis of parasegment 2, is among the earliest to be defined. It is soon divided into two distinct regions: the more dorsal pregland cells and the more ventral preduct cells. We show that it is the opposing activities of the Drosophila EGF receptor (DER) signaling pathway and the Fork head transcription factor that distinguish these cell types and set up the boundary between them. DER signaling acts ventrally to block fork head expression in the preduct cells, thereby restricting gland identity to the more dorsal cells. Fork head in turn blocks expression of duct-specific genes in the pregland cells, thereby restricting duct identity to the more ventral cells. A third regulatory activity, the Trachealess transcription factor, is also required to establish the identity of the preduct cells, but we show that it acts independently or downstream from the DER:fork head confrontation. In trachealess mutants, subdivision of the salivary primordium occurs normally and the dorsal cells form glands, but the ventral cells are undetermined. We present a model proposing that trachealess is the crucial duct-specific gene that Fork head represses to distinguish pregland from preduct cells.
果蝇胚胎的器官发生在发育4 - 5小时时开始，此时器官特异性基因的表达被启动。占据副节2腹侧表皮的唾液原基是最早被确定的结构之一。它很快被分为两个不同的区域：背侧的前腺细胞和腹侧的前导管细胞。我们发现，果蝇表皮生长因子受体（DER）信号通路和叉头转录因子的相反作用区分了这些细胞类型，并在它们之间建立了边界。DER信号在腹侧起作用，阻止前导管细胞中叉头的表达，从而将腺体特性限制在更靠背侧的细胞中。叉头反过来又阻止前腺细胞中导管特异性基因的表达，从而将导管特性限制在更靠腹侧的细胞中。第三种调节活性，即无气管转录因子，对于确定前导管细胞的特性也是必需的，但我们发现它独立于DER：叉头的对抗作用或在其下游起作用。在无气管突变体中，唾液原基的细分正常发生，背侧细胞形成腺体，但腹侧细胞未分化。我们提出了一个模型，认为无气管是叉头抑制的关键导管特异性基因，以区分前腺细胞和前导管细胞。
