Data from: Fitness change in relation to mutation number in spontaneous mutation accumulation lines of Chlamydomonas reinhardtii

Although all genetic variation ultimately stems from mutations, their properties are difficult to study directly. Here, we used multiple mutation accumulation (MA) lines derived from five genetic backgrounds of the green algae Chlamydomonas reinhardtii that have been previously subjected to whole genome sequencing to investigate the relationship between the number of spontaneous mutations and change in fitness from a non-evolved ancestor. MA lines were on average less fit than their ancestors and we detected a significantly negative correlation between the change in fitness and the total number of accumulated mutations in the genome. Likewise, the number of mutations located within coding regions significantly and negatively impacted MA line fitness. We used the fitness data to parameterize a maximum likelihood model to estimate discrete categories of mutational effects, and found that models containing one to two mutational effect categories (one neutral and one deleterious category) fitted the data best. However, the best-fitting mutational effects models were highly dependent on the genetic background of the ancestral strain.尽管所有遗传变异归根结底都源于突变，但其自身特性却难以直接开展研究。本研究借助此前已完成全基因组测序的、源自5种遗传背景的莱茵衣藻（Chlamydomonas reinhardtii）多株突变累积（mutation accumulation, MA）品系，探究自发突变数量与未进化祖先的适合度变化之间的关联。结果显示，MA品系的平均适合度低于其祖先亲本，且适合度变化与基因组中累积突变的总数量之间存在显著负相关关系。同样，编码区域内的突变数量也对MA品系的适合度产生了显著负向影响。本研究通过适合度数据对最大似然模型进行参数化，以估算突变效应的离散类别；结果表明，包含1至2类突变效应（1类中性类别与1类有害类别）的模型与数据拟合度最优。不过，拟合效果最优的突变效应模型高度依赖于祖先菌株的遗传背景。