Department of Zoology, Institute of Biology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany.
Genome Biol Evol. 2013;5(1):151-62. doi: 10.1093/gbe/evs133.
Microsatellites, or simple sequence repeats (SSRs), are common and widespread DNA elements in genomes of many organisms. However, their dynamics in genome evolution is unclear, whereby they are thought to evolve neutrally. More available genome sequences along with dated phylogenies allowed for studying the evolution of these repetitive DNA elements along evolutionary time scales. This could be used to compare rates of genome evolution. We show that SSRs in insects can be retained for several hundred million years. Different types of microsatellites seem to be retained longer than others. By comparing Dipteran with Hymenopteran species, we found very similar patterns of SSR loss during their evolution, but both taxa differ profoundly in the rate. Relative to divergence time, Diptera lost SSRs twice as fast as Hymenoptera. The loss of SSRs on the Drosophila melanogaster X-chromosome was higher than on the other chromosomes. However, accounting for generation time, the Diptera show an 8.5-fold slower rate of SSR loss than the Hymenoptera, which, in contrast to previous studies, suggests a faster genome evolution in the latter. This shows that generation time differences can have a profound effect. A faster genome evolution in these insects could be facilitated by several factors very different to Diptera, which is discussed in light of our results on the haplodiploid D. melanogaster X-chromosome. Furthermore, large numbers of SSRs can be found to be in synteny and thus could be exploited as a tool to investigate genome structure and evolution.
微卫星或简单重复序列（SSR）是许多生物基因组中常见且广泛分布的 DNA 元件。然而，它们在基因组进化中的动态尚不清楚，人们认为它们是中性进化的。随着更多基因组序列和有时间标记的系统发育树的出现，人们可以研究这些重复 DNA 元件在进化时间尺度上的演化。这可以用来比较基因组演化的速度。我们表明，昆虫中的 SSR 可以保留数亿年。不同类型的微卫星似乎比其他类型保留得更久。通过比较双翅目和膜翅目物种，我们发现它们在进化过程中 SSR 的丢失模式非常相似，但这两个类群在速度上有很大的差异。相对于分歧时间，双翅目丢失 SSR 的速度是膜翅目的两倍。黑腹果蝇 X 染色体上 SSR 的丢失速度高于其他染色体。然而，考虑到世代时间，双翅目昆虫的 SSR 丢失速度比膜翅目昆虫慢 8.5 倍，这与之前的研究结果相反，表明后者的基因组演化速度更快。这表明世代时间的差异会产生深远的影响。这些昆虫更快的基因组演化可能是由与双翅目非常不同的几个因素促成的，这一点在考虑到我们对单倍二倍体黑腹果蝇 X 染色体的研究结果时，是值得讨论的。此外，大量的 SSR 可以被发现是同线的，因此可以被用作研究基因组结构和演化的工具。
