Department of Earth Sciences, Uppsala University, Villavägen 16, 75236, Palaeobiology, Sweden.
Evolutionary Ecology, Faculty of Biology, Ludwig-Maximilians Universität München, Grosshaderner Strasse 2, 82152, Biozentrum, Germany.
Dev Genes Evol. 2022 Feb;232(1):27-37. doi: 10.1007/s00427-022-00684-5. Epub 2022 Jan 17.
In the arthropod model species Drosophila melanogaster, a dipteran fly, segmentation of the anterior-posterior body axis is under control of a hierarchic gene cascade. Segmental boundaries that form morphological grooves are established posteriorly within the segmental expression domain of the segment-polarity gene (SPG) engrailed (en). More important for the development of the fly, however, are the parasegmental boundaries that are established at the interface of en expressing cells and anteriorly adjacent wingless (wg) expressing cells. In Drosophila, both segmental and transient parasegmental grooves form. The latter are positioned anterior to the expression of en. Although the function of the SPGs in establishing and maintaining segmental and parasegmental boundaries is highly conserved among arthropods, parasegmental grooves have only been reported for Drosophila, and a spider (Cupiennius salei). Here, we present new data on en expression, and re-evaluate published data, from four distantly related spiders, including Cupiennius, and a distantly related chelicerate, the harvestman Phalangium opilio. Gene expression analysis of en genes in these animals does not corroborate the presence of parasegmental grooves. Consequently, our data question the general presence of parasegmental grooves in arthropods.
在节肢动物模式生物黑腹果蝇中，一种双翅目昆虫，前后体轴的分段受分级基因级联控制。形成形态凹槽的分段边界在后段极性基因（SPG） engrailed（en）的分段表达域内建立。然而，对于蝇类的发育更重要的是在 en 表达细胞和前部相邻的无翅（wg）表达细胞的界面处建立的副节段边界。在果蝇中，形成了分段和瞬时副节段凹槽。后者位于 en 表达的前面。尽管 SPG 在建立和维持分段和副节段边界方面的功能在节肢动物中高度保守，但副节段凹槽仅在果蝇和一种蜘蛛（Cupiennius salei）中报道过。在这里，我们提供了来自四个远缘蜘蛛（包括 Cupiennius 和远缘螯肢动物 harvestman Phalangium opilio）的 en 表达的新数据，并重新评估了已发表的数据。对这些动物的 en 基因的基因表达分析不支持副节段凹槽的存在。因此，我们的数据质疑副节段凹槽在节肢动物中的普遍存在。
