Department of Biology, University of Maryland - College Park, College Park, Maryland, United States of America.
PLoS Genet. 2019 Nov 8;15(11):e1008493. doi: 10.1371/journal.pgen.1008493. eCollection 2019 Nov.
Genomic GC content varies widely among microbes for reasons unknown. While mutation bias partially explains this variation, prokaryotes near-universally have a higher GC content than predicted solely by this bias. Debate surrounds the relative importance of the remaining explanations of selection versus biased gene conversion favoring GC alleles. Some environments (e.g. soils) are associated with a high genomic GC content of their inhabitants, which implies that either high GC content is a selective adaptation to particular habitats, or that certain habitats favor increased rates of gene conversion. Here, we report a novel association between the presence of the non-homologous end joining DNA double-strand break repair pathway and GC content; this observation suggests that DNA damage may be a fundamental driver of GC content, leading in part to the many environmental patterns observed to-date. We discuss potential mechanisms accounting for the observed association, and provide preliminary evidence that sites experiencing higher rates of double-strand breaks are under selection for increased GC content relative to the genomic background.
基因组 GC 含量在微生物中差异很大，原因尚不清楚。虽然突变偏向部分解释了这种变异，但原核生物的 GC 含量普遍高于仅由这种偏向预测的 GC 含量。关于选择与有利于 GC 等位基因的偏向基因转换的剩余解释的相对重要性存在争议。一些环境（例如土壤）与其居民的高基因组 GC 含量有关，这意味着要么高 GC 含量是对特定栖息地的选择性适应，要么某些栖息地有利于增加基因转换的速度。在这里，我们报告了非同源末端连接 DNA 双链断裂修复途径与 GC 含量之间的新关联；这一观察结果表明，DNA 损伤可能是 GC 含量的一个基本驱动因素，部分导致了迄今为止观察到的许多环境模式。我们讨论了解释观察到的关联的潜在机制，并提供了初步证据表明，与基因组背景相比，经历更高双链断裂速率的位点受到增加 GC 含量的选择。
