Department of Biochemistry, University of Zurich, Zurich, Switzerland.
PLoS Comput Biol. 2010 Mar 26;6(3):e1000719. doi: 10.1371/journal.pcbi.1000719.
Organismal development and many cell biological processes are organized in a modular fashion, where regulatory molecules form groups with many interactions within a group and few interactions between groups. Thus, the activity of elements within a module depends little on elements outside of it. Modularity facilitates the production of heritable variation and of evolutionary innovations. There is no consensus on how modularity might evolve, especially for modules in development. We show that modularity can increase in gene regulatory networks as a byproduct of specialization in gene activity. Such specialization occurs after gene regulatory networks are selected to produce new gene activity patterns that appear in a specific body structure or under a specific environmental condition. Modules that arise after specialization in gene activity comprise genes that show concerted changes in gene activities. This and other observations suggest that modularity evolves because it decreases interference between different groups of genes. Our work can explain the appearance and maintenance of modularity through a mechanism that is not contingent on environmental change. We also show how modularity can facilitate co-option, the utilization of existing gene activity to build new gene activity patterns, a frequent feature of evolutionary innovations.
生物体发育和许多细胞生物学过程以模块化的方式组织，其中调节分子在一个组内形成具有许多相互作用的组，而在组之间很少有相互作用。因此，一个模块内的元素的活性很少依赖于其外部的元素。模块性促进了遗传变异和进化创新的产生。对于发育中的模块，模块性如何进化尚没有共识。我们表明，随着基因活性的专业化，基因调控网络中的模块性可以作为副产品而增加。这种专业化发生在基因调控网络被选择以产生新的基因活性模式之后，这些模式出现在特定的身体结构或特定的环境条件下。在基因活性专业化之后出现的模块包括表现出基因活性协同变化的基因。这一观察结果和其他观察结果表明，模块性的进化是因为它减少了不同基因群之间的干扰。我们的工作可以通过一种不依赖于环境变化的机制来解释模块性的出现和维持。我们还展示了模块性如何促进共适应，即利用现有基因活性来构建新的基因活性模式，这是进化创新的一个常见特征。
