Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, 46022 València, Spain.
Genetics. 2010 Jul;185(3):983-9. doi: 10.1534/genetics.110.115915. Epub 2010 May 3.
Knowing mutation rates and the molecular spectrum of spontaneous mutations is important to understanding how the genetic composition of viral populations evolves. Previous studies have shown that the rate of spontaneous mutations for RNA viruses widely varies between 0.01 and 2 mutations per genome and generation, with plant RNA viruses always occupying the lower side of this range. However, this peculiarity of plant RNA viruses is based on a very limited number of studies. Here we analyze the spontaneous mutational spectrum and the mutation rate of Tobacco etch potyvirus, a model system of positive sense RNA viruses. Our experimental setup minimizes the action of purifying selection on the mutational spectrum, thus giving a picture of what types of mutations are produced by the viral replicase. As expected for a neutral target, we found that transitions and nonsynonymous (including a few stop codons and small deletions) mutations were the most abundant type. This spectrum was notably different from the one previously described for another plant virus. We have estimated that the spontaneous mutation rate for this virus was in the range 10(-6)-10(-5) mutations per site and generation. Our estimates are in the same biological ballpark that previous values reported for plant RNA viruses. This finding gives further support to the idea that plant RNA viruses may have lower mutation rates than their animal counterparts.
了解自发突变率和分子谱对于理解病毒群体的遗传组成如何进化非常重要。先前的研究表明，RNA 病毒的自发突变率在每个基因组和代之间的 0.01 到 2 个突变之间广泛变化，植物 RNA 病毒总是处于这个范围的较低端。然而，植物 RNA 病毒的这种特殊性是基于非常有限的研究。在这里，我们分析了烟草蚀纹病毒的自发突变谱和突变率，这是正链 RNA 病毒的一个模型系统。我们的实验设置将选择压力对突变谱的作用最小化，从而描绘出病毒复制酶产生的突变类型。正如对中性靶标所预期的那样，我们发现转换和非同义（包括一些终止密码子和小缺失）突变是最丰富的类型。该谱与之前描述的另一种植物病毒的谱明显不同。我们估计该病毒的自发突变率为每个位点和代 10(-6)-10(-5)个突变。我们的估计值与先前报道的植物 RNA 病毒的数值在相同的生物学范围内。这一发现进一步支持了植物 RNA 病毒的突变率可能低于其动物对应物的观点。
