Genikhovich Grigory, Technau Ulrich
Department for Molecular Evolution and Development, Centre of Organismal Systems Biology, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria
Development. 2017 Oct 1;144(19):3392-3404. doi: 10.1242/dev.141507.
Bilaterality - the possession of two orthogonal body axes - is the name-giving trait of all bilaterian animals. These body axes are established during early embryogenesis and serve as a three-dimensional coordinate system that provides crucial spatial cues for developing cells, tissues, organs and appendages. The emergence of bilaterality was a major evolutionary transition, as it allowed animals to evolve more complex body plans. Therefore, how bilaterality evolved and whether it evolved once or several times independently is a fundamental issue in evolutionary developmental biology. Recent findings from non-bilaterian animals, in particular from Cnidaria, the sister group to Bilateria, have shed new light into the evolutionary origin of bilaterality. Here, we compare the molecular control of body axes in radially and bilaterally symmetric cnidarians and bilaterians, identify the minimal set of traits common for Bilateria, and evaluate whether bilaterality arose once or more than once during evolution.
两侧对称——拥有两条相互垂直的身体轴——是所有两侧对称动物的标志性特征。这些身体轴在胚胎发育早期确立，并作为一个三维坐标系，为细胞、组织、器官和附属肢体的发育提供关键的空间线索。两侧对称的出现是一次重大的进化转变，因为它使动物能够进化出更复杂的身体结构。因此，两侧对称是如何进化的，以及它是独立进化了一次还是多次，是进化发育生物学中的一个基本问题。来自非两侧对称动物，特别是刺胞动物（两侧对称动物的姐妹类群）的最新研究结果，为两侧对称的进化起源提供了新的线索。在这里，我们比较了辐射对称和两侧对称的刺胞动物以及两侧对称动物中身体轴的分子控制机制，确定了两侧对称动物共有的最小特征集，并评估了两侧对称在进化过程中是出现了一次还是多次。
