Department of Biology and Department of Computer Science and Engineering, York University, Toronto, ON, Canada M3J 1P3.
Proc Natl Acad Sci U S A. 2014 Feb 18;111(7):2614-9. doi: 10.1073/pnas.1315506111. Epub 2014 Jan 31.
Most theories used to explain the evolution of eusociality rest upon two key assumptions: mutations affecting the phenotype of sterile workers evolve by positive selection if the resulting traits benefit fertile kin, and that worker traits provide the primary mechanism allowing social insects to adapt to their environment. Despite the common view that positive selection drives phenotypic evolution of workers, we know very little about the prevalence of positive selection acting on the genomes of eusocial insects. We mapped the footprints of positive selection in Apis mellifera through analysis of 40 individual genomes, allowing us to identify thousands of genes and regulatory sequences with signatures of adaptive evolution over multiple timescales. We found Apoidea- and Apis-specific genes to be enriched for signatures of positive selection, indicating that novel genes play a disproportionately large role in adaptive evolution of eusocial insects. Worker-biased proteins have higher signatures of adaptive evolution relative to queen-biased proteins, supporting the view that worker traits are key to adaptation. We also found genes regulating worker division of labor to be enriched for signs of positive selection. Finally, genes associated with worker behavior based on analysis of brain gene expression were highly enriched for adaptive protein and cis-regulatory evolution. Our study highlights the significant contribution of worker phenotypes to adaptive evolution in social insects, and provides a wealth of knowledge on the loci that influence fitness in honey bees.
如果影响不育工蜂表型的突变对有亲缘关系的可育个体有益，那么这些突变就会受到正选择的影响，而且工蜂的特征是使社会性昆虫适应环境的主要机制。尽管人们普遍认为正选择推动了工蜂的表型进化，但我们对作用于真社会性昆虫基因组的正选择的普遍性知之甚少。我们通过分析 40 个个体基因组，在蜜蜂中绘制了正选择的足迹图，从而能够识别出数千个具有跨多个时间尺度的适应性进化特征的基因和调控序列。我们发现，Apoidea 和蜜蜂特有的基因富集了正选择的特征，这表明新基因在社会性昆虫的适应性进化中起着不成比例的重要作用。相对于蜂王偏爱的蛋白质，工蜂偏爱的蛋白质具有更高的适应性进化特征，这支持了工蜂特征是适应的关键这一观点。我们还发现，调节工蜂分工的基因富集了正选择的迹象。最后，基于对大脑基因表达的分析，与工蜂行为相关的基因在适应性蛋白和顺式调控进化方面高度富集。我们的研究强调了工蜂表型对社会性昆虫适应性进化的重要贡献，并为影响蜜蜂适应性的基因提供了丰富的知识。
