A new look at genome size, evolutionary duration and genetic variation in salamanders
A new look at genome size, evolutionary duration and genetic variation in salamanders
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DOI：
10.1016/j.crpv.2014.06.002
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发表时间：
2014-10-01
影响因子：
1.1
通讯作者：
Sclavi, Bianca
中科院分区：
文献类型：
--
作者：
Herrick, John;Sclavi, Bianca
蝾螈拥有脊椎动物中最大的基因组，也是报告的遗传多样性水平最低的一些。特别是幼形类，在泌尿系统中平均具有最大的基因组，并且显示出异常低的核苷酸和蛋白质变异水平。在这里，我们解决的问题，在8个不同的蝾螈家庭的基因组大小的遗传变异。使用rag1基因作为进化速率的探针，我们发现，在专性幼象（neotenes）和其他蝾螈物种的替代率非常低。在某些情况下，替代率与软骨鱼的报告一样低，软骨鱼是迄今为止脊椎动物中突变率最低的。在此基础上，我们还发现了大齿鲨科的基因组大小与系统发育年龄之间的相关性，这表明大齿鲨科的基因组大小演化具有更普遍的趋势。Plethodontidae，此外，显示出更高水平的遗传变异比专性neotene家庭，在陆地蝾螈更大的栖息地异质性相一致。最后，我们提出了一个基因，rag1，其取代率与基因组大小呈负相关的第一个直接证据。基于这些和其他观察，我们提出了一个假设，根据该假设，在脊椎动物进化过程中，随着基因组大小的减少，核基因的突变率往往会增加。(C)2014年，科学院。由Elsevier Masson SAS出版。All rights reserved.
Salamanders have some of the largest genomes among vertebrates, and also some of the lowest reported levels of genetic diversity. Paedomorphs, in particular, have the largest genomes on average among urodela, and display exceptionally low levels of nucleotide and protein variation. Here, we address the question of genetic variation in relation to genome size in eight different salamander families. Using the rag1 gene as a probe for evolutionary rates, we found that rates of substitution are exceptionally low in obligate paedomorphs (neotenes) and other salamander species. Substitution rates in some cases are as low as those reported for cartilaginous fish, which have the slowest mutation rates recorded so far in vertebrates. Confirming and extending an earlier study, we also found that genome size is correlated with phylogenetic age in Plethodontidae, indicating a more general trend in genome size evolution in urodela. The Plethodontidae, furthermore, display much higher levels of genetic variance than the obligate neotene families, consistent with greater habitat heterogeneity in terrestrial salamanders. Finally, we present the first direct evidence of a gene, rag1, whose substitution rate is negatively associated with genome size. Based on these and other observations, we propose a hypothesis according to which mutation rates in nuclear genes tend to increase as genome size decreases during the course of vertebrate evolution. (C) 2014 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.