Burger Gertraud, Yan Yifei, Javadi Pasha, Lang B Franz
Robert Cedergren Centre for Bioinformatics and Genomics, Département de Biochimie, Université de Montréal, C.P. 6128, Montréal, Québec, H3T 1J4, Canada.
Trends Genet. 2009 Sep;25(9):381-6. doi: 10.1016/j.tig.2009.07.003. Epub 2009 Aug 27.
Placozoa - the simplest known free-living animals - have been considered primitive, early diverging metazoans based on mitochondrial genome structure and phylogeny. Here we reanalyze placozoan mitochondrial DNAs, reported to include a highly unorthodox, fragmented and incomplete cox1 gene. We discover overlooked exons and split group I introns that mediate trans-splicing of the discontinuous placozoan cox1. Furthermore, we find that cox1 expression involves U-to-C editing, reconstituting an otherwise invariant, essential histidine involved in copper binding. These atypical features qualify placozoan mitochondrial gene and genome organization as derived rather than primitive. Whether the Placozoa diverged early or late during metazoan evolution remains unresolved by mitochondrial phylogeny.
扁盘动物门——已知最简单的自由生活动物——基于线粒体基因组结构和系统发育，一直被认为是原始的、早期分化的后生动物。在此，我们重新分析了扁盘动物的线粒体DNA，据报道其包含一个高度非正统、片段化且不完整的细胞色素c氧化酶亚基1（cox1）基因。我们发现了被忽视的外显子和介导不连续扁盘动物cox1反式剪接的I组内含子。此外，我们发现cox1的表达涉及U到C的编辑，从而重建了一个原本不变的、参与铜结合的必需组氨酸。这些非典型特征表明扁盘动物线粒体基因和基因组组织是衍生的而非原始的。扁盘动物门在后生动物进化过程中是早期还是晚期分化，线粒体系统发育仍未解决。
