Department of Genetics, University of Cambridge, Cambridge, CB2 3EH, UK.
School of Life Sciences Research Complex, University of Dundee, Dow Street, Dundee, DD1 5EH, UK.
Development. 2023 Apr 1;150(7). doi: 10.1242/dev.200885. Epub 2023 Apr 17.
During gastrulation, early embryos specify and reorganise the topology of their germ layers. Surprisingly, this fundamental and early process does not appear to be rigidly constrained by evolutionary pressures; instead, the morphology of gastrulation is highly variable throughout the animal kingdom. Recent experimental results demonstrate that it is possible to generate different alternative gastrulation modes in single organisms, such as in early cnidarian, arthropod and vertebrate embryos. Here, we review the mechanisms that underlie the plasticity of vertebrate gastrulation both when experimentally manipulated and during evolution. Using the insights obtained from these experiments we discuss the effects of the increase in yolk volume on the morphology of gastrulation and provide new insights into two crucial innovations during amniote gastrulation: the transition from a ring-shaped mesoderm domain in anamniotes to a crescent-shaped domain in amniotes, and the evolution of the reptilian blastoporal plate/canal into the avian primitive streak.
在原肠胚形成过程中，早期胚胎指定并重新组织它们的胚层拓扑结构。令人惊讶的是，这一基本且早期的过程似乎并没有受到进化压力的严格限制；相反，原肠胚形成的形态在整个动物界具有高度的可变性。最近的实验结果表明，在单个生物体中产生不同的替代原肠胚形成模式是可能的，例如在早期刺胞动物、节肢动物和脊椎动物胚胎中。在这里，我们回顾了在实验操作和进化过程中，脊椎动物原肠胚形成可塑性的机制。利用从这些实验中获得的见解，我们讨论了卵黄体积增加对原肠胚形成形态的影响，并为羊膜动物原肠胚形成中的两个关键创新提供了新的见解：无羊膜动物的环形状中胚层域到羊膜动物的新月形域的转变，以及爬行动物原口板/通道向鸟类原条的进化。
