Riese J, Tremml G, Bienz M
MRC Laboratory of Molecular Biology, Cambridge, UK.
Development. 1997 Sep;124(17):3353-61. doi: 10.1242/dev.124.17.3353.
The Drosophila endoderm is patterned by the signals Decapentaplegic and Wingless secreted from the visceral mesoderm. This induction culminates in a precise pattern of spatially restricted expression of labial, a selector gene with a role in cell type specification in the larval midgut. Here, we show that Decapentaplegic signalling induces elevated expression of the Drosophila AP-1 transcription factor D-Fos in a slightly broader endodermal region than labial. This induction occurs in parallel to, and independently of, that of labial. Furthermore, we present evidence that D-Fos is required for labial induction in the embryo as well as for maintenance of labial expression through larval stages; and that D-Fos is critical for cellular differentiation in the larval gut. We propose that Decapentaplegic, by inducing D-Fos, broadly defines an endodermal region which thus becomes predisposed to express labial, and that D-Fos cooperates with signal-activated response factors to confer the precise pattern of labial expression in this region.
果蝇内胚层的形成是由来自内脏中胚层分泌的信号分子“十体节蛋白”（Decapentaplegic）和“无翅蛋白”（Wingless）所调控的。这种诱导作用最终导致了唇基因（labial）在空间上受到限制的精确表达模式，唇基因是一种选择基因，在幼虫中肠的细胞类型特化过程中发挥作用。在此，我们表明，十体节蛋白信号传导在比唇基因表达区域稍宽的内胚层区域诱导果蝇AP - 1转录因子D - Fos的表达升高。这种诱导作用与唇基因的诱导作用同时发生且相互独立。此外，我们提供的证据表明，D - Fos在胚胎期唇基因的诱导以及幼虫阶段唇基因表达的维持过程中都是必需的；并且D - Fos对幼虫肠道的细胞分化至关重要。我们提出，十体节蛋白通过诱导D - Fos，广泛地界定了一个内胚层区域，该区域因此易于表达唇基因，并且D - Fos与信号激活的反应因子协同作用，在该区域赋予唇基因精确的表达模式。
