Schröder Reinhard
Interfakultäres Institut für Zellbiologie, Universität Tübingen, Abt. Genetik der Tiere, Auf der Morgenstelle 28, 72076 Tübingen, Germany.
Nature. 2003 Apr 10;422(6932):621-5. doi: 10.1038/nature01536.
In Drosophila, the morphogen Bicoid organizes anterior patterning in a concentration-dependent manner by activating the transcription of target genes such as orthodenticle (otd) and hunchback (hb), and by repressing the translation of caudal. Homologues of the bicoid gene have not been isolated in any organism apart from the higher Dipterans. In fact, head and thorax formation in other insects is poorly understood. To elucidate this process in a short-germband insect, I analysed the function of the conserved genes orthodenticle-1 (otd-1) and hb in the flour beetle Tribolium castaneum. Here I show that, in contrast to Drosophila, Tribolium otd-1 messenger RNA is maternally inherited by the embryo. Reduction of Tribolium otd-1 levels by RNA interference (RNAi) results in headless embryos. This shows that otd-1 is required for anterior patterning in Tribolium. As in Drosophila, Tribolium hb specifies posterior gnathal and thoracic segments. The head, thorax and the anterior abdomen fail to develop in otd-1/hb double-RNAi embryos. This phenotype is similar to that of strong bicoid mutants in Drosophila. I propose that otd-1 and hb are part of an ancestral anterior patterning system.
在果蝇中，形态发生素双胸蛋白（Bicoid）通过激活目标基因（如正齿蛋白（orthodenticle，otd）和驼背蛋白（hunchback，hb））的转录以及抑制尾蛋白（caudal）的翻译，以浓度依赖的方式组织前部模式形成。除了高等双翅目昆虫外，尚未在任何生物体中分离出双胸蛋白基因的同源物。事实上，其他昆虫头部和胸部的形成过程还知之甚少。为了阐明短胚带昆虫中的这一过程，我分析了面粉甲虫赤拟谷盗（Tribolium castaneum）中保守基因正齿蛋白-1（otd-1）和hb的功能。在此我表明，与果蝇不同，赤拟谷盗otd-1信使核糖核酸（mRNA）由胚胎母系遗传。通过RNA干扰（RNAi）降低赤拟谷盗otd-1水平会导致无头胚胎。这表明otd-1是赤拟谷盗前部模式形成所必需的。与果蝇一样，赤拟谷盗hb决定后部颚节和胸节。在otd-1/hb双RNAi胚胎中，头部、胸部和前腹部无法发育。这种表型与果蝇中强双胸蛋白突变体的表型相似。我提出otd-1和hb是祖先前部模式形成系统的一部分。
