Institute for Ecology and Evolution, University of Oregon, Eugene, OR 97403, USA.
Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA.
G3 (Bethesda). 2021 Apr 15;11(4). doi: 10.1093/g3journal/jkab045.
The adaptation of complex organisms to changing environments has been a central question in evolutionary quantitative genetics since its inception. The structure of the genotype-phenotype maps is critical because pleiotropic effects can generate widespread correlated responses to selection and potentially restrict the extent of evolutionary change. In this study, we use experimental evolution to dissect the genetic architecture of natural variation for acute heat stress and oxidative stress response in the nematode Caenorhabiditis remanei. Previous work in the classic model nematode Caenorhabiditis elegans has found that abiotic stress response is controlled by a handful of genes of major effect and that mutations in any one of these genes can have widespread pleiotropic effects on multiple stress response traits. Here, we find that acute heat stress response and acute oxidative response in C. remanei are polygenic, complex traits, with hundreds of genomic regions responding to selection. In contrast to expectation from mutation studies, we find that evolved acute heat stress and acute oxidative stress response for the most part display independent genetic bases. This lack of correlation is reflected at the levels of phenotype, gene expression, and in the genomic response to selection. Thus, while these findings support the general view that rapid adaptation can be generated by changes at hundreds to thousands of sites in the genome, the architecture of segregating variation is likely to be determined by the pleiotropic structure of the underlying genetic networks.
复杂生物对环境变化的适应一直是进化数量遗传学自成立以来的核心问题。基因型-表型图谱的结构至关重要，因为多效性效应可以产生广泛的与选择相关的相关性反应，并可能限制进化变化的程度。在这项研究中，我们使用实验进化来剖析秀丽隐杆线虫自然变异的遗传结构，这些变异与急性热应激和氧化应激反应有关。经典模式线虫秀丽隐杆线虫的先前工作发现，非生物胁迫反应受少数几个主要效应基因控制，这些基因中的任何一个突变都可能对多种胁迫反应性状产生广泛的多效性影响。在这里，我们发现秀丽隐杆线虫的急性热应激反应和急性氧化应激反应是多基因的复杂性状，有数百个基因组区域对选择做出反应。与突变研究的预期相反，我们发现进化的急性热应激和急性氧化应激反应在很大程度上显示出独立的遗传基础。这种缺乏相关性反映在表型、基因表达以及对选择的基因组反应水平上。因此，虽然这些发现支持了快速适应可以通过基因组中数百到数千个位点的变化产生的一般观点，但分离变异的结构可能取决于潜在遗传网络的多效性结构。
