PDF(Pubmed)
Abstract：
Despite the morphological diversity of animals, their basic anatomical patterns-the body plans in each animal phylum-have remained highly conserved over hundreds of millions of evolutionary years. This is attributed to conservation of the body plan-establishing developmental period (the phylotypic period) in each lineage. However, the evolutionary mechanism behind this phylotypic period conservation remains under debate. A variety of hypotheses based on the concept of modern synthesis have been proposed, such as negative selection in the phylotypic period through its vulnerability to embryonic lethality. Here we tested a new hypothesis that the phylotypic period is developmentally stable; it has less potential to produce phenotypic variations than the other stages, and this has most likely led to the evolutionary conservation of body plans.
By analyzing the embryos of inbred Japanese medaka embryos raised under the same laboratory conditions and measuring the whole embryonic transcriptome as a phenotype, we found that the phylotypic period has greater developmental stability than other stages. Comparison of phenotypic differences between two wild medaka populations indicated that the phylotypic period and its genes in this period remained less variational, even after environmental and mutational modifications accumulated during intraspecies evolution. Genes with stable expression levels were enriched with those involved in cell-cell signalling and morphological specification such as Wnt and Hox, implying possible involvement in body plan development of these genes.
This study demonstrated the correspondence between the developmental stage with low potential to produce phenotypic variations and that with low diversity in micro- and macroevolution, namely the phylotypic period. Whereas modern synthesis explains evolution as a process of shaping of phenotypic variations caused by mutations, our results highlight the possibility that phenotypic variations are readily limited by the intrinsic nature of organisms, namely developmental stability, thus biasing evolutionary outcomes.
By analyzing the embryos of inbred Japanese medaka embryos raised under the same laboratory conditions and measuring the whole embryonic transcriptome as a phenotype, we found that the phylotypic period has greater developmental stability than other stages. Comparison of phenotypic differences between two wild medaka populations indicated that the phylotypic period and its genes in this period remained less variational, even after environmental and mutational modifications accumulated during intraspecies evolution. Genes with stable expression levels were enriched with those involved in cell-cell signalling and morphological specification such as Wnt and Hox, implying possible involvement in body plan development of these genes.
This study demonstrated the correspondence between the developmental stage with low potential to produce phenotypic variations and that with low diversity in micro- and macroevolution, namely the phylotypic period. Whereas modern synthesis explains evolution as a process of shaping of phenotypic variations caused by mutations, our results highlight the possibility that phenotypic variations are readily limited by the intrinsic nature of organisms, namely developmental stability, thus biasing evolutionary outcomes.
摘要：
尽管动物的形态多样性,它们的基本解剖模式-每个动物门的身体计划-在数亿年的进化中一直保持高度保守。这归因于每个谱系中身体计划建立发育期（育型期）的保守性。然而,这个生理型时期保守背后的进化机制仍在争论中。提出了基于现代综合概念的各种假设，例如，通过其对胚胎致命性的脆弱性，在生理阶段进行阴性选择。在这里，我们测试了一个新的假设，即生理阶段是发育稳定的；与其他阶段相比，它产生表型变异的可能性较小，这很可能导致了身体计划的进化保守。
通过分析在相同实验室条件下培养的近交日本medaka胚胎的胚胎，并测量整个胚胎转录组作为表型，我们发现，生理阶段比其他阶段具有更大的发育稳定性。两个野生medaka种群之间的表型差异的比较表明，该时期的适形期及其基因的变化较小，即使在物种内进化过程中积累了环境和突变修饰。具有稳定表达水平的基因富集了参与细胞-细胞信号传导和形态学规范的基因，如Wnt和Hox。暗示这些基因可能参与身体计划的发展。
这项研究证明了产生表型变异潜力低的发育阶段与微观和宏观进化多样性低的发育阶段之间的对应关系。即适形期。现代合成将进化解释为由突变引起的表型变异的形成过程，我们的结果强调了表型变异容易受到生物体内在性质限制的可能性，即发展稳定，从而使进化结果产生偏差。
通过分析在相同实验室条件下培养的近交日本medaka胚胎的胚胎，并测量整个胚胎转录组作为表型，我们发现，生理阶段比其他阶段具有更大的发育稳定性。两个野生medaka种群之间的表型差异的比较表明，该时期的适形期及其基因的变化较小，即使在物种内进化过程中积累了环境和突变修饰。具有稳定表达水平的基因富集了参与细胞-细胞信号传导和形态学规范的基因，如Wnt和Hox。暗示这些基因可能参与身体计划的发展。
这项研究证明了产生表型变异潜力低的发育阶段与微观和宏观进化多样性低的发育阶段之间的对应关系。即适形期。现代合成将进化解释为由突变引起的表型变异的形成过程，我们的结果强调了表型变异容易受到生物体内在性质限制的可能性，即发展稳定，从而使进化结果产生偏差。
