Mutation accumulation lines are used to determine the amount of variation added each generation due to mutations in C.reinhardtii.. The effect of mutation on gene expression in Chlamydomonas reinhardtii

Survival hinges on the malleability of DNA in response to environmental demands; mutations arise from accidental alterations of DNA sequences and provide the raw material for evolution by introducing genetic variation. Gene expression can be used to link the effect of mutations on the genome – genotype, and its respective phenotypic change. It has been used to study de novo mutations and their effects on gene networks, regulation, and other phenotypic traits including fitness. Here, we sequenced the mRNA of 28 mutation accumulation lines derived from two independent wild-type genotypes of the green algae Chlamydomonas reinhardtii. We found the median mutational variance was up to 18 orders of magnitude higher than past studies possibly indicative of a more responsive transcriptome in microbes. We calculated the amount of expression variation contributed per mutation over several generations and found that high expression genes underwent a lower total expression change than that of lower expression genes. Genes that underwent significant expression change did so in both directions’ indicative of trans-acting effects. Surprisingly, we did not find a correlation between fitness and expression change, though future studies can disentangle the individual phenotypic and fitness-related effects of each mutation rather than the collective.

生物的生存依赖于DNA响应环境需求的可塑性；突变源于DNA序列的偶然改变，通过引入遗传变异为进化提供原始素材。基因表达可用于关联突变对基因组（即基因型）的影响，及其对应的表型变化。该方法已被用于研究新发突变（de novo mutations）及其对基因网络、调控过程以及包括适合度在内的其他表型性状的影响。本研究对源自两株独立野生型基因型的莱茵衣藻（Chlamydomonas reinhardtii）的28个突变积累株系的mRNA进行了测序。我们发现，突变方差的中位数较以往研究高出多达18个数量级，这或预示着微生物中存在更为敏感的转录组。我们计算了多代中每处突变所贡献的表达变异量，发现高表达基因的总表达变化幅度低于低表达基因。发生显著表达变化的基因，其表达变化方向涵盖上调与下调两类，这提示存在反式作用效应（trans-acting effects）。令人意外的是，我们未发现适合度与表达变化之间存在相关性；不过未来的研究可厘清单个突变各自的表型效应及其与适合度相关的效应，而非仅关注整体的集体效应。