Noor M A, Kliman R M, Machado C A
Department of Biological Sciences, Louisiana State University, Baton Rouge 70803, USA.
Mol Biol Evol. 2001 Apr;18(4):551-6. doi: 10.1093/oxfordjournals.molbev.a003834.
The evolutionary origins of microsatellites are not well understood. Some investigators have suggested that point mutations that expand repeat arrays beyond a threshold size trigger microsatellites to become variable. However, little empirical data has been brought forth on this and related issues. In this study, we examine the evolutionary history of microsatellites in six species within the obscura group of Drosophila, tracing changes in microsatellite alleles using both PCR product size and sequence data. We found little evidence supporting a general role of point mutations triggering initial microsatellite expansion, and no consistent threshold size for expansion was observed. Flanking region length variation was extensive when alleles were sequenced in distantly related species, and some species possessed altogether different repeat arrays between the same primer binding sites. Our results suggest extreme caution in using microsatellite allele sizes for phylogenetic analyses or to infer divergences between populations.
微卫星的进化起源尚未得到很好的理解。一些研究者认为，点突变使重复序列阵列扩展到超过阈值大小会触发微卫星变得可变。然而，关于这一点及相关问题几乎没有实证数据。在本研究中，我们研究了果蝇obscura组六个物种中微卫星的进化历史，利用PCR产物大小和序列数据追踪微卫星等位基因的变化。我们几乎没有发现证据支持点突变触发微卫星初始扩展的普遍作用，也未观察到一致的扩展阈值大小。当对远缘物种的等位基因进行测序时，侧翼区域长度变化很大，并且一些物种在相同引物结合位点之间完全拥有不同的重复序列阵列。我们的结果表明，在将微卫星等位基因大小用于系统发育分析或推断种群间差异时要极其谨慎。
