Maternal activation of gap genes in the hover fly Episyrphus
Maternal activation of gap genes in the hover fly Episyrphus
复制标题
DOI：
10.1242/dev.046649
复制
发表时间：
2010-05-15
期刊：
影响因子：
4.6
通讯作者：
Schmidt-Ott, Urs
中科院分区：
文献类型：
--
作者：
Lemke, Steffen;Busch, Stephanie E.;Schmidt-Ott, Urs
昆虫身体计划的同源异构体组织是随着GAP基因的激活而启动的，GAP基因是一组转录因子编码基因，在早期胚胎的前后轴上广泛且部分重叠的结构域中合子表达。GAP基因表达结构域沿AP轴的空间格局一般是保守的，但调节其表达的母体基因却不是这样。在全面了解果蝇母体GAP基因激活的基础上，我们利用悬浮蝇Eisyrphus balteatus(Syrphidae)的功能丧失和功能获得实验来解决GAP基因的母体调控如何进化的问题。我们发现，在Episyrphus中，高度发散的双曲面直系基因是胚胎AP极性的唯一原因。二粒石斑鱼抑制尾部前合子的表达，并激活前部和中央GAP基因正齿、驼背和Kruppel。在类双核缺陷的Episyrphus胚胎中，Nanos不足以沿AP轴产生形态不对称。此外，我们发现躯干短暂地调节尾部的前抑制，并且是正齿的激活所必需的，而Knirps、巨人、驼背、无尾和huckebein的所有后部间隙基因结构域都依赖于尾部。我们得出结论，在高等果蝇(Cyclorrhapha)的辐射过程中，所有母体坐标基因都改变了它们的特定功能。
The metameric organization of the insect body plan is initiated with the activation of gap genes, a set of transcription-factor-encoding genes that are zygotically expressed in broad and partially overlapping domains along the anteroposterior (AP) axis of the early embryo. The spatial pattern of gap gene expression domains along the AP axis is generally conserved, but the maternal genes that regulate their expression are not. Building on the comprehensive knowledge of maternal gap gene activation in Drosophila, we used loss-and gain-of-function experiments in the hover fly Episyrphus balteatus (Syrphidae) to address the question of how the maternal regulation of gap genes evolved. We find that, in Episyrphus, a highly diverged bicoid ortholog is solely responsible for the AP polarity of the embryo. Episyrphus bicoid represses anterior zygotic expression of caudal and activates the anterior and central gap genes orthodenticle, hunchback and Kruppel. In bicoid-deficient Episyrphus embryos, nanos is insufficient to generate morphological asymmetry along the AP axis. Furthermore, we find that torso transiently regulates anterior repression of caudal and is required for the activation of orthodenticle, whereas all posterior gap gene domains of knirps, giant, hunchback, tailless and huckebein depend on caudal. We conclude that all maternal coordinate genes have altered their specific functions during the radiation of higher flies (Cyclorrhapha).