Schaeffer V, Killian D, Desplan C, Wimmer E A
Department of Biology, New York University, New York NY 10003 USA.
Development. 2000 Sep;127(18):3993-9. doi: 10.1242/dev.127.18.3993.
In Drosophila, the gradient of the Bicoid (Bcd) morphogen organizes the anteroposterior axis while the ends of the embryo are patterned by the maternal terminal system. At the posterior pole, expression of terminal gap genes is mediated by the local activation of the Torso receptor tyrosine kinase (Tor). At the anterior, terminal gap genes are also activated by the Tor pathway but Bcd contributes to their activation. Here we present evidence that Tor and Bcd act independently on common target genes in an additive manner. Furthermore, we show that the terminal maternal system is not required for proper head development, since high levels of Bcd activity can functionally rescue the lack of terminal system activity at the anterior pole. This observation is consistent with a recent evolution of an anterior morphogenetic center consisting of Bcd and anterior Tor function.
在果蝇中，形态发生素双尾（Bcd）的梯度组织前后轴，而胚胎的两端则由母体末端系统进行模式化。在后极，末端间隙基因的表达由躯干受体酪氨酸激酶（Tor）的局部激活介导。在前部，末端间隙基因也由Tor信号通路激活，但Bcd也有助于它们的激活。在这里，我们提供证据表明，Tor和Bcd以相加的方式独立作用于共同的靶基因。此外，我们表明，适当的头部发育不需要末端母体系统，因为高水平的Bcd活性可以在功能上挽救前极末端系统活性的缺失。这一观察结果与最近由Bcd和前部Tor功能组成的前部形态发生中心的进化一致。
