Mitochondrial genomes of Galathealinum, Helobdella, and Platynereis:: Sequence and gene arrangement comparisons indicate that Pogonophora is not a phylum and Annelida and Arthropoda are not sister taxa
Mitochondrial genomes of Galathealinum, Helobdella, and Platynereis:: Sequence and gene arrangement comparisons indicate that Pogonophora is not a phylum and Annelida and Arthropoda are not sister taxa
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DOI：
10.1093/oxfordjournals.molbev.a026241
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发表时间：
2000-01-01
影响因子：
10.7
通讯作者：
Brown, WM
中科院分区：
文献类型：
--
作者：
Boore, JL;Brown, WM
我们报告了一个超过一半（>7,500 nt）的线粒体基因组的连续区域的Platynereis dumerii（环节动物：多毛类），Helobdella robusta（环节动物：水蛭目），Galathealinum brachiosum（Pogonophora：Perviata）。Helobdella和Galathealinum中鉴定的所有22个基因的相对排列彼此相同，并且与之前研究的寡毛纲环节动物Lumbricus的线粒体DNA中的排列相同。与此相反，Platynereis不同于这些类群中的几个tRNA基因的位置，并在有两个额外的tRNA基因（trnC和trnM）和一个大的非编码序列在这一地区。这些和其他已发表的类群之间的相对基因排列和核苷酸和推断的氨基酸序列的比较提供了有力的支持环节动物，软体动物的分支，不包括节肢动物，并列入pogonophorans环节动物，而不是给他们单独的门的地位。基因排列比较包括首次使用最近描述的方法对以前未发表的数据。尽管线粒体蛋白质编码基因通常使用多种替代起始密码子，但ATG似乎是本文报道的所有启动子中的一个。大的非编码区（1，091 nt）确定在Platynereis的非编码区的蚯蚓没有显着的序列相似性，虽然每个包含运行的TA二核苷酸和均聚物，这可能是潜在的信号元件。Helobdella和Galathealinum中同义密码子使用有很强的偏好性。在后一分类群中，5个密码子完全未使用，13个密码子使用三次或更少次，并且G仅在2，236个密码子中的26个中出现在第三密码子位置。核苷酸组成的偏见似乎影响蛋白质的氨基酸组成。
We report a contiguous region of more than half (>7,500 nt) of the mitochondrial genomes for Platynereis dumerii (Annelida: Polychaeta), Helobdella robusta (Annelida: Hirudinida), and Galathealinum brachiosum (Pogonophora: Perviata). The relative arrangements of all 22 genes identified for Helobdella and Galathealinum are identical to one another and to their arrangements in the mtDNA of the previously studied oligochaete annelid Lumbricus. In contrast, Platynereis differs from these taxa in the positions of several tRNA genes and in having two additional tRNA genes (trnC and trnM) and a large noncoding sequence in this region. Comparisons of relative gene arrangements and of the nucleotide and inferred amino acid sequences among these and other published taxa provide strong support for an annelid-mollusk clade that excludes arthropods, and for the inclusion of pogonophorans within Annelida, rather than giving them separate phylum status. Gene arrangement comparisons include the first use of a recently described method on previously unpublished data. Although a variety of alternative initiation codons are typically used by mitochondrial protein-encoding genes, ATG appears to be the initiator for all but one reported here. The large noncoding region (1,091 nt) identified in Platynereis has no significant sequence similarity to the noncoding region of Lumbricus, although each contains runs of TA dinucleotides and of homopolymers, which could potentially serve as signaling elements. There is strong bias for synonymous codon usage in Helobdella and especially in Galathealinum. in this latter taxon, 5 codons are completely unused, 13 are used three or fewer times, and G appears at third codon positions in only 26 of the 2,236 codons. Nucleotide composition bias appears to influence amino acid composition of the proteins.