Vogt Günter
Faculty of Biosciences, University of Heidelberg, Im Neuenheimer Feld 230, D-69120, Heidelberg, Germany,
J Biosci. 2015 Mar;40(1):159-204. doi: 10.1007/s12038-015-9506-8.
This article reviews the production of different phenotypes from the same genotype in the same environment by stochastic cellular events, nonlinear mechanisms during patterning and morphogenesis, and probabilistic self-reinforcing circuitries in the adult life. These aspects of phenotypic variation are summarized under the term 'stochastic developmental variation' (SDV) in the following. In the past, SDV has been viewed primarily as a nuisance, impairing laboratory experiments, pharmaceutical testing, and true-to-type breeding. This article also emphasizes the positive biological effects of SDV and discusses implications for genotype-to-phenotype mapping, biological individuation, ecology, evolution, and applied biology. There is strong evidence from experiments with genetically identical organisms performed in narrowly standardized laboratory set-ups that SDV is a source of phenotypic variation in its own right aside from genetic variation and environmental variation. It is obviously mediated by molecular and higher-order epigenetic mechanisms. Comparison of SDV in animals, plants, fungi, protists, bacteria, archaeans, and viruses suggests that it is a ubiquitous and phylogenetically old phenomenon. In animals, it is usually smallest for morphometric traits and highest for life history traits and behaviour. SDV is thought to contribute to phenotypic diversity in all populations but is particularly relevant for asexually reproducing and genetically impoverished populations, where it generates individuality despite genetic uniformity. In each generation, SDV produces a range of phenotypes around a well-adapted target phenotype, which is interpreted as a bet-hedging strategy to cope with the unpredictability of dynamic environments. At least some manifestations of SDV are heritable, adaptable, selectable, and evolvable, and therefore, SDV may be seen as a hitherto overlooked evolution factor. SDV is also relevant for husbandry, agriculture, and medicine because most pathogens are asexuals that exploit this third source of phenotypic variation to modify infectivity and resistance to antibiotics. Since SDV affects all types of organisms and almost all aspects of life, it urgently requires more intense research and a better integration into biological thinking.
本文回顾了在相同环境中，通过随机细胞事件、模式形成和形态发生过程中的非线性机制以及成年期的概率性自我强化回路，从同一基因型产生不同表型的过程。以下将这些表型变异的方面总结为“随机发育变异”（SDV）。过去，SDV主要被视为一种麻烦，会影响实验室实验、药物测试和纯种繁育。本文还强调了SDV的积极生物学效应，并讨论了其对基因型到表型映射、生物个体化、生态学、进化和应用生物学的影响。在严格标准化的实验室环境中对基因相同的生物体进行的实验有强有力的证据表明，除了遗传变异和环境变异外，SDV本身就是表型变异的一个来源。它显然是由分子和高阶表观遗传机制介导的。对动物、植物、真菌、原生生物、细菌、古生菌和病毒中的SDV进行比较表明，它是一种普遍存在且在系统发育上古老的现象。在动物中，形态测量性状的SDV通常最小，而生活史性状和行为的SDV最高。SDV被认为对所有种群的表型多样性都有贡献，但对无性繁殖和基因匮乏的种群尤为重要，在这些种群中，尽管基因一致，但它仍能产生个体差异。在每一代中，SDV会在一个适应良好的目标表型周围产生一系列表型，这被解释为一种应对动态环境不可预测性的风险对冲策略。SDV的至少一些表现是可遗传的、可适应的、可选择的和可进化的，因此，SDV可能被视为一个迄今为止被忽视的进化因素。SDV在畜牧业、农业和医学中也很重要，因为大多数病原体都是无性繁殖的，它们利用这第三种表型变异来源来改变感染性和对抗生素的抗性。由于SDV影响所有类型的生物体以及生命的几乎所有方面，因此迫切需要更深入的研究，并更好地融入生物学思维。
