Affolter M, Walldorf U, Kloter U, Schier A F, Gehring W J
Biozentrum, University of Basel, Switzerland.
Development. 1993 Apr;117(4):1199-210. doi: 10.1242/dev.117.4.1199.
An induction process occurring between the mesodermal and the endodermal germ layers has recently been described in the regulation of the Drosophila homeotic gene labial (lab). We report here that proper spatial regulation of the Drosophila POU box gene pdm-1 products also involves interaction between these two germ layers. pdm-1 transcripts are initially present in both the anterior and the posterior endodermal midgut primordia. Upon fusion of the two primordia, transcripts disappear from two regions in the endoderm, a central domain and an anterior domain. The anterior repression domain of pdm-1 is independent of the expression of known homeotic genes and genes encoding secreted signalling molecules in the visceral mesoderm, both for its positioning and its repression. Repression in the central domain requires both the homeotic gene Ultrabithorax (Ubx) and the decapentaplegic (dpp) gene, which encodes a secreted protein. Both of these genes are also required for lab induction. However, the analysis of pdm-1 expression in various mutant backgrounds indicates that the regulation of lab and pdm-1 across germ layers is controlled by different genetic cascades. Our study indicates that dpp is not the signal that dictates central pdm-1 repression across germ layers and suggests that in the same midgut region, different signalling pathways result in the differential activation or repression of potential transcription factors.
最近在果蝇同源异型基因唇（lab）的调控中描述了一种发生在中胚层和内胚层胚层之间的诱导过程。我们在此报告，果蝇POU盒基因pdm - 1产物的正确空间调控也涉及这两个胚层之间的相互作用。pdm - 1转录本最初存在于前后端内胚层中肠原基。两个原基融合后，转录本在内胚层的两个区域消失，一个是中央区域，一个是前部区域。pdm - 1的前部抑制区域在其定位和抑制方面均独立于已知同源异型基因和在内脏中胚层中编码分泌信号分子的基因的表达。中央区域的抑制需要同源异型基因超双胸（Ubx）和编码一种分泌蛋白的脱壳蛋白（dpp）基因。这两个基因对于lab的诱导也是必需的。然而，在各种突变背景下对pdm - 1表达的分析表明，lab和pdm - 1跨胚层的调控由不同的遗传级联控制。我们的研究表明，dpp不是决定跨胚层中央pdm - 1抑制的信号，并表明在同一中肠区域，不同的信号通路导致潜在转录因子的差异激活或抑制。
