Holló Gábor
Institute of Psychology, University of Debrecen, H-4002, Debrecen, P.O. Box 400, Hungary.
Biol Direct. 2017 May 17;12(1):11. doi: 10.1186/s13062-017-0182-5.
ᅟ: Symmetry is an eye-catching feature of animal body plans, yet its causes are not well enough understood. The evolution of animal form is mainly due to changes in gene regulatory networks (GRNs). Based on theoretical considerations regarding fundamental GRN properties, it has recently been proposed that the animal genome, on large time scales, should be regarded as a system which can construct both the main symmetries - radial and bilateral - simultaneously; and that the expression of any of these depends on functional constraints. Current theories explain biological symmetry as a pattern mostly determined by phylogenetic constraints, and more by chance than by necessity. In contrast to this conception, I suggest that physical effects, which in many cases act as proximate, direct, tissue-shaping factors during ontogenesis, are also the ultimate causes - i.e. the indirect factors which provide a selective advantage - of animal symmetry, from organs to body plan level patterns. In this respect, animal symmetry is a necessary product of evolution. This proposition offers a parsimonious view of symmetry as a basic feature of the animal body plan, suggesting that molecules and physical forces act in a beautiful harmony to create symmetrical structures, but that the concert itself is directed by the latter.
This article was reviewed by Eugene Koonin, Zoltán Varga and Michaël Manuel.
对称是动物身体结构引人注目的特征，但其成因尚未得到充分理解。动物形态的进化主要归因于基因调控网络（GRNs）的变化。基于对GRN基本特性的理论思考，最近有人提出，在较长时间尺度上，动物基因组应被视为一个能够同时构建两种主要对称性——辐射对称和双侧对称——的系统；并且其中任何一种对称性的表达都取决于功能限制。当前理论将生物对称性解释为一种模式，主要由系统发育限制决定，更多是偶然而非必然。与这种观念相反，我认为物理效应在许多情况下在个体发育过程中作为直接的、组织塑造因素起作用，同时也是动物对称性从器官到身体结构水平模式的最终原因——即提供选择优势的间接因素。在这方面，动物对称性是进化的必然产物。这一观点为对称性作为动物身体结构的基本特征提供了一种简洁的看法，表明分子和物理力以美妙的和谐作用来创造对称结构，但这种协同本身是由物理力引导的。
本文由尤金·库宁、佐尔坦·瓦尔加和米夏埃尔·曼努埃尔评审。
