Department of Biological Sciences, National University of Singapore, Singapore, Singapore.
Tropical Marine Science Institute, National University of Singapore, Singapore, Singapore.
Mol Biol Evol. 2021 Mar 9;38(3):981-985. doi: 10.1093/molbev/msaa262.
The mitochondrial genetic code is much more varied than the standard genetic code. The invertebrate mitochondrial code, for instance, comprises six initiation codons, including five alternative start codons. However, only two initiation codons are known in the echinoderm and flatworm mitochondrial code, the canonical ATG and alternative GTG. Here, we analyzed 23 Asteroidea mitogenomes, including ten newly sequenced species and unambiguously identified at least two other start codons, ATT and ATC, both of which also initiate translation of mitochondrial genes in other invertebrates. These findings underscore the diversity of the genetic code and expand upon the suite of initiation codons among echinoderms to avoid erroneous annotations. Our analyses have also uncovered the remarkable conservation of gene order among asteroids, echinoids, and holothuroids, with only an interchange between two gene positions in asteroids over ∼500 Ma of echinoderm evolution.
线粒体遗传密码比标准遗传密码更加多样化。例如，无脊椎动物的线粒体密码包含六个起始密码子，其中包括五个备用起始密码子。然而，在棘皮动物和扁形动物的线粒体密码中，仅知两个起始密码子，即规范的 ATG 和备用的 GTG。在这里，我们分析了 23 种海星线粒体基因组，包括十个新测序的物种，并明确鉴定出至少另外两个起始密码子 ATT 和 ATC，这两个密码子也都在其他无脊椎动物中起始翻译线粒体基因。这些发现强调了遗传密码的多样性，并扩展了棘皮动物中起始密码子的套件，以避免错误注释。我们的分析还揭示了海星、海胆和海参之间基因排列的惊人保守性，在大约 5 亿年的棘皮动物进化过程中，海星中只有两个基因位置发生了互换。
