Relaxed selection is a precursor to the evolution of phenotypic plasticity
Relaxed selection is a precursor to the evolution of phenotypic plasticity
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DOI：
10.1073/pnas.1104825108
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发表时间：
2011-09-20
影响因子：
11.1
通讯作者：
Goodisman, Michael A. D.
中科院分区：
文献类型：
--
作者：
Hunt, Brendan G.;Ometto, Lino;Goodisman, Michael A. D.
表型可塑性允许生物在不同的条件下产生不同的表型，是生物体对环境做出适应性反应的最重要的方式之一。然而，表型可塑性和分子进化之间的关系仍然知之甚少。我们通过研究与火蚁的表型塑料种姓、性别和发育阶段相关的基因的进化来解决这个问题。我们首先确定了与不列颠链霉菌表型可塑性相关的基因是否如理论模型所预测的那样以快速的速度进化。我们发现，与普遍表达的基因相比，在不同种姓、性别和发育阶段之间差异表达的基因都表现出更高的进化速度。接下来，我们研究了与种姓产生相关的基因的进化史。令人惊讶的是，我们发现，不列颠蜜蜂和群居蜜蜂中种姓偏见基因的同源基因在没有种姓的谱系中进化得很快。因此，与一些理论预测相反，我们的结果表明，分子进化的快速速度可能主要不是表型可塑性的结果。相反，在宽松的净化选择下进化的基因可能更容易在交替表型的进化过程中采用新的有偏见的表达形式。这些结果表明，在表型可塑性的进化起源中，对蛋白质编码基因的松弛选择性约束是一个重要而被忽视的因素。
Phenotypic plasticity allows organisms to produce alternative phenotypes under different conditions and represents one of the most important ways by which organisms adaptively respond to the environment. However, the relationship between phenotypic plasticity and molecular evolution remains poorly understood. We addressed this issue by investigating the evolution of genes associated with phenotypically plastic castes, sexes, and developmental stages of the fire ant Solenopsis invicta. We first determined if genes associated with phenotypic plasticity in S. invicta evolved at a rapid rate, as predicted under theoretical models. We found that genes differentially expressed between S. invicta castes, sexes, and developmental stages all exhibited elevated rates of evolution compared with ubiquitously expressed genes. We next investigated the evolutionary history of genes associated with the production of castes. Surprisingly, we found that orthologs of caste-biased genes in S. invicta and the social bee Apis mellifera evolved rapidly in lineages without castes. Thus, in contrast to some theoretical predictions, our results suggest that rapid rates of molecular evolution may not arise primarily as a consequence of phenotypic plasticity. Instead, genes evolving under relaxed purifying selection may more readily adopt new forms of biased expression during the evolution of alternate phenotypes. These results suggest that relaxed selective constraint on protein-coding genes is an important and underappreciated element in the evolutionary origin of phenotypic plasticity.