Alexander Michelle, Ho Simon Y W, Molak Martyna, Barnett Ross, Carlborg Örjan, Dorshorst Ben, Honaker Christa, Besnier Francois, Wahlberg Per, Dobney Keith, Siegel Paul, Andersson Leif, Larson Greger
BioArCh Biology S Block, University of York, Wentworth Way, Heslington, York YO10 5DD, UK Department of Archaeology, School of Geosciences, University of Aberdeen, St. Mary's, Elphinstone Road, AB24 3UF, UK.
School of Biological Sciences, University of Sydney, Sydney, New South Wales 2006, Australia.
Biol Lett. 2015 Oct;11(10). doi: 10.1098/rsbl.2015.0561.
Mitochondrial genomes represent a valuable source of data for evolutionary research, but studies of their short-term evolution have typically been limited to invertebrates, humans and laboratory organisms. Here we present a detailed study of 12 mitochondrial genomes that span a total of 385 transmissions in a well-documented 50-generation pedigree in which two lineages of chickens were selected for low and high juvenile body weight. These data allowed us to test the hypothesis of time-dependent evolutionary rates and the assumption of strict maternal mitochondrial transmission, and to investigate the role of mitochondrial mutations in determining phenotype. The identification of a non-synonymous mutation in ND4L and a synonymous mutation in CYTB, both novel mutations in Gallus, allowed us to estimate a molecular rate of 3.13 × 10(-7) mutations/site/year (95% confidence interval 3.75 × 10(-8)-1.12 × 10(-6)). This is substantially higher than avian rate estimates based upon fossil calibrations. Ascertaining which of the two novel mutations was present in an additional 49 individuals also revealed an instance of paternal inheritance of mtDNA. Lastly, an association analysis demonstrated that neither of the point mutations was strongly associated with the phenotypic differences between the two selection lines. Together, these observations reveal the highly dynamic nature of mitochondrial evolution over short time periods.
线粒体基因组是进化研究的宝贵数据来源，但对其短期进化的研究通常仅限于无脊椎动物、人类和实验室生物。在此，我们对12个线粒体基因组进行了详细研究，这些基因组在一个记录完备的50代家系中总共经历了385次遗传传递，该家系中两个鸡系分别被选择用于低和高幼年体重。这些数据使我们能够检验时间依赖性进化速率的假设以及严格母系线粒体遗传的假设，并研究线粒体突变在决定表型中的作用。在ND4L中鉴定出一个非同义突变以及在CYTB中鉴定出一个同义突变，这两个都是原鸡中的新突变，使我们能够估计分子速率为3.13×10^(-7) 个突变/位点/年（95%置信区间为3.75×10^(-8)-1.12×10^(-6)）。这显著高于基于化石校准的鸟类速率估计。确定这两个新突变在另外49个个体中存在哪一个，还揭示了线粒体DNA父系遗传的一个实例。最后，关联分析表明这两个点突变均与两个选择系之间的表型差异没有强烈关联。总之，这些观察结果揭示了线粒体在短时间内进化的高度动态性质。
