Mitochondrial genome of Trichoplax adhaerens supports Placozoa as the basal lower metazoan phylum
Mitochondrial genome of Trichoplax adhaerens supports Placozoa as the basal lower metazoan phylum
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DOI：
10.1073/pnas.0602076103
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发表时间：
2006-06-06
影响因子：
11.1
通讯作者：
Schierwater, B
中科院分区：
文献类型：
--
作者：
Dellaporta, SL;Xu, A;Schierwater, B
多细胞动物的线粒体基因组通常是15-24kb的环状分子，编码一套几乎相同的12-14氧化磷酸化蛋白质和24-25个结构RNA(16S rRNA、12S rRNA和tRNAs)。这些基因组缺乏显着的基因内间隔区，并且通常没有内含子。在这里，我们报道了粘性绒毛虫(Trichoplax Adhaerens)的完整线粒体基因组序列，这是已知的动物中最简单的后生动物，没有器官，没有基膜，只有四种不同的体细胞类型。我们的分析表明，Trichoplax线粒体包含已知的最大的后生动物mtDNA基因组，长度为43,079 bp，是典型后生动物mtDNA大小的两倍多。线粒体的大小是由于大量的基因内间隔区，几个功能未知的内含子和开放阅读框，以及通常比其他动物中发现的更大的蛋白质编码区。Trichoplax mtDNA不仅具有已知的后生动物外类群线粒体基因组的特征，如壶菌和鞭毛虫，更重要的是，它共享后生动物特有的派生特征。线粒体蛋白质的系统发育分析为后生动物门的定位提供了有力的支持。
Mitochondrial genomes of multicellular animals are typically 15- to 24-kb circular molecules that encode a nearly identical set of 12-14 proteins for oxidative phosphorylation and 24-25 structural RNAs (16S rRNA, 12S rRNA, and tRNAs). These genomes lack significant intragenic spacers and are generally without introns. Here, we report the complete mitochondrial genome sequence of the placozoan Trichoplax adhaerens, a metazoan with the simplest known body plan of any animal, possessing no organs, no basal membrane, and only four different somatic cell types. Our analysis shows that the Trichoplax mitochondrion contains the largest known metazoan mtDNA genome at 43,079 bp, more than twice the size of the typical metazoan mtDNA. The mitochondrion's size is due to numerous intragenic spacers, several introns and ORFs of unknown function, and protein-coding regions that are generally larger than those found in other animals. Not only does the Trichoplax mtDNA have characteristics of the mitochondrial genomes of known metazoan outgroups, such as chytrid fungi and choanoflagellates, but, more importantly, it shares derived features unique to the Metazoa. Phylogenetic analyses of mitochondrial proteins provide strong support for the placement of the phylum Placozoa at the root of the Metazoa.