Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile.
Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
J Exp Zool B Mol Dev Evol. 2023 Dec;340(8):531-540. doi: 10.1002/jez.b.23023. Epub 2020 Dec 31.
Living beings are autopoietic systems with highly context-dependent structural dynamics and interactions, that determine whether a disturbance in the genotype or environment will lead or not to phenotypic change. The concept of epigenesis entails how a change in the phenotype may not correspond to a change in the structure of an earlier developmental stage, including the genome. Disturbances of embryonic structure may fail to change the phenotype, as in regulated development, or when different genotypes are associated to a single phenotype. Likewise, the same genotype or early embryonic structure may develop different phenotypes, as in phenotypic plasticity. Disturbances that fail to trigger phenotypic change are considered neutral, but even so, they can alter unexpressed developmental potential. Here, we present conceptual diagrams of the "epigenic field": similar to Waddington's epigenetic landscapes, but including the ontogenic niche (organism/environment interactional dynamics during ontogeny) as a factor in defining epigenic fields, rather than just selecting among possible pathways. Our diagrams illustrate transgenerational changes of genotype, ontogenic niche, and their correspondence (or lack thereof) with changes of phenotype. Epigenic fields provide a simple way to understand developmental constraints on evolution, for instance: how constraints evolve as a result of developmental system drift; how neutral changes can be involved in genetic assimilation and de-assimilation; and how constraints can evolve as a result of neutral changes in the ontogenic niche (not only the genotype). We argue that evolutionary thinking can benefit from a framework for evolution with conceptual foundations at the organismal level.
生物是具有高度语境依赖性结构动态和相互作用的自组织系统，这些动态和相互作用决定了基因型或环境的干扰是否会导致表型变化。发生表观遗传的概念涉及到表型的变化可能与早期发育阶段结构的变化（包括基因组）不对应。胚胎结构的干扰可能不会改变表型，如在调控发育或不同基因型与单一表型相关联的情况下。同样，相同的基因型或早期胚胎结构可能会发展出不同的表型，如表型可塑性。未能引发表型变化的干扰被认为是中性的，但即使如此，它们也可以改变未表达的发育潜力。在这里，我们展示了“表观遗传场”的概念图：类似于 Waddington 的表观遗传景观，但包括个体发生时的生态位（个体发生过程中生物体/环境相互作用的动态）作为定义表观遗传场的一个因素，而不仅仅是在可能的途径中进行选择。我们的图表说明了基因型、个体发生时的生态位及其与表型变化的对应关系（或缺乏对应关系）的跨代变化。表观遗传场为理解进化对发育的限制提供了一种简单的方法，例如：由于发育系统漂移，限制如何进化；中性变化如何参与遗传同化和去同化；以及由于个体发生时的生态位（不仅是基因型）中的中性变化，限制如何进化。我们认为，进化思维可以从一个在生物体层面具有概念基础的进化框架中受益。
