Regulation of the Tribolium homologues of caudal and hunchback in Drosophila: evidence for maternal gradient systems in a short germ embryo.
Regulation of the Tribolium homologues of caudal and hunchback in Drosophila: evidence for maternal gradient systems in a short germ embryo.
复制标题
果蝇尾部和驼背的谷盗同源物的调节：短胚芽中母体梯度系统的证据。
作者：
Christian Wolff;Reinhard Schröder;C. Schulz;Diethard Tautz;Martin Klingler
在短胚中，胚原基形成于卵的后腹侧，而前背区域成为胚外浆膜。很难理解像果蝇中的双曲面那样的前梯度如何能在这些胚胎中直接参与胚原基的形成。此外，由于尚不可能从双翅目以外的任何物种中恢复bicoid同源物，因此推测前bicoid梯度可能是昆虫进化过程中的晚期添加物。本研究通过分析赤拟谷盗短胚中bicoid潜在靶基因的调控来解决这一问题。我们表明，同源的尾部和驼背拟谷盗的果蝇bicoid的调节。在果蝇中，母体尾部RNA被bicoid抑制。我们发现，赤拟谷盗尾RNA也被抑制bicoid，当它被转移到果蝇胚胎的母系启动子。这有力地表明，一个功能bicoid同源物必须存在于拟谷盗属。第二个靶基因hunchback在果蝇中被bicoid转录激活。将赤拟谷盗驼背的调控区转移到果蝇中也会导致早期母体因子（包括bicoid）的调控，但其模式更容易让人联想到赤拟谷盗驼背的表达，即在两个早期胚盘结构域中。使用增强子映射结构和足迹，我们表明，尾激活后，这些域通过一个特定的启动子。我们的实验表明，在从短到长的胚胎发生的进化过渡的一个主要事件是开关从激活的驼背缺口域的尾部直接激活bicoid。这种调节开关可以解释这个结构域如何从短胚胚的后部位置转移到长胚昆虫的前部位置，并且它还表明前部梯度如何在短胚中形成胚基，即通过调节尾部的表达。
In short germ embryos, the germ rudiment forms at the posterior ventral side of the egg, while the anterior-dorsal region becomes the extra-embryonic serosa. It is difficult to see how an anterior gradient like that of bicoid in Drosophila could in these embryos be directly involved in patterning of the germ rudiment. Moreover, since it has not yet been possible to recover a bicoid homologue from any species outside the diptera, it has been speculated that the anterior bicoid gradient could be a late addition during insect evolution. We addressed this question by analysing the regulation of potential target genes of bicoid in the short germ embryo of Tribolium castaneum. We demonstrate that homologues of caudal and hunchback from Tribolium are regulated by Drosophila bicoid. In Drosophila, maternal caudal RNA is translationally repressed by bicoid. We find that Tribolium caudal RNA is also translationally repressed by bicoid, when it is transferred into Drosophila embryos under a maternal promoter. This strongly suggests that a functional bicoid homologue must exist in Tribolium. The second target gene, hunchback, is transcriptionally activated by bicoid in Drosophila. Transfer of the regulatory region of Tribolium hunchback into Drosophila also results in regulation by early maternal factors, including bicoid, but in a pattern that is more reminiscent of Tribolium hunchback expression, namely in two early blastoderm domains. Using enhancer mapping constructs and footprinting, we show that caudal activates the posterior of these domains via a specific promoter. Our experiments suggest that a major event in the evolutionary transition from short to long germ embryogenesis was the switch from activation of the hunchback gap domain by caudal to direct activation by bicoid. This regulatory switch can explain how this domain shifted from a posterior location in short germ embryos to its anterior position in long germ insects, and it also suggest how an anterior gradient can pattern the germ rudiment in short germ embryos, i.e. by regulating the expression of caudal.
驼背的后条纹表达是由两个启动子通过一个共同的增强子元件驱动的。
DOI：
10.1242/dev.121.9.3067
发表时间：
1995
期刊：
Development (Cambridge, England)
影响因子：
--
作者：
Margolis,JS;Borowsky,ML;Steingrímsson,E;Shim,CW;Lengyel,JA;Posakony,JW
通讯作者：
Posakony,JW
果蝇分割基因表达的母体控制。
影响因子：
64.8
作者：
Carroll,SB;Winslow,GM;Schupbach,T;Scott,MP
通讯作者：
Scott,MP