Abascal Federico, Posada David, Zardoya Rafael
Departamento de Biodiversidad y Biología Evolutiva, Museo Nacional de Ciencias Naturales CSIC, José Gutiérrez Abascal 2, 28006 Madrid, Spain.
Mitochondrial DNA. 2012 Apr;23(2):84-91. doi: 10.3109/19401736.2011.653801. Epub 2012 Mar 7.
A variant of the invertebrate mitochondrial genetic code was previously identified in arthropods (Abascal et al. 2006a, PLoS Biol 4:e127) in which, instead of translating the AGG codon as serine, as in other invertebrates, some arthropods translate AGG as lysine. Here, we revisit the evolution of the genetic code in arthropods taking into account that (1) the number of arthropod mitochondrial genomes sequenced has triplicated since the original findings were published; (2) the phylogeny of arthropods has been recently resolved with confidence for many groups; and (3) sophisticated probabilistic methods can be applied to analyze the evolution of the genetic code in arthropod mitochondria. According to our analyses, evolutionary shifts in the genetic code have been more common than previously inferred, with many taxonomic groups displaying two alternative codes. Ancestral character-state reconstruction using probabilistic methods confirmed that the arthropod ancestor most likely translated AGG as lysine. Point mutations at tRNA-Lys and tRNA-Ser correlated with the meaning of the AGG codon. In addition, we identified three variables (GC content, number of AGG codons, and taxonomic information) that best explain the use of each of the two alternative genetic codes.
先前在节肢动物中发现了一种无脊椎动物线粒体遗传密码的变体（阿巴斯卡尔等人，2006年a，《公共科学图书馆·生物学》4：e127），在该变体中，与其他无脊椎动物将AGG密码子翻译为丝氨酸不同，一些节肢动物将AGG翻译为赖氨酸。在此，我们重新审视节肢动物遗传密码的进化，考虑到：（1）自最初的发现发表以来，已测序的节肢动物线粒体基因组数量增加了两倍；（2）节肢动物的系统发育最近已被许多类群可靠地解析；（3）可以应用复杂的概率方法来分析节肢动物线粒体遗传密码的进化。根据我们的分析，遗传密码的进化转变比先前推断的更为常见，许多分类群显示出两种替代密码。使用概率方法进行的祖先特征状态重建证实，节肢动物祖先很可能将AGG翻译为赖氨酸。tRNA-Lys和tRNA-Ser的点突变与AGG密码子的含义相关。此外，我们确定了三个变量（GC含量、AGG密码子数量和分类信息），它们最能解释两种替代遗传密码中每一种的使用情况。
