湾鳄(Crocodylus porosus)线粒体基因组全序列结构分析与鳄类系统发生

该文测序了湾鳄的线粒体基因组全序列,全长为16,917bp。湾鳄mtDNA结构与其他脊椎动物相似,由22个tRNA,2个rRNA和13个蛋白质编码基因及1个非编码的控制区(D-loop)所组成。除NADH6和tRNAGln、tRNAAla、tRNAAsn、tRNACys、tRNATyr、tRNASer(UCN)、tRNAGlu、tRNAPro在L-链上编码之外,其余基因均在H-链编码。基因排列顺序与已测序的鳄类一致,这显示了鳄类线粒体基因排列顺序上的保守性。但鳄类线粒体基因排列顺序与脊椎动物的典型排列方式相比,有较大的差异,尤其是tRNAPhe基因的重排、tRNASer-tRNAHis-tRNALeu基因族的排列方式等。湾鳄mtDNA和已测序的鳄类一样,缺失轻链复制起始点(OLR)。基于17种鳄mtDNA控制区保守区,采用PAUP4.0最大简约法(Maximumparsimony,MP)构建MP树,邻接法(Neighbor-joiningmethod,NJ)构建NJ树,结果显示:食鱼鳄(Gavialisgangeticus)和假食鱼鳄(Tomistomaschlegelii)聚为一支后再与鳄科(Crocodylidae)的其他物种形成姐妹群,这与基于食鱼鳄和假食鱼鳄的线粒体全序列的分析结果一致,支持将食鱼鳄并入鳄科的观点。结果还支持非洲窄吻鳄(Crocodyluscataphractus)与鳄属(Crocodylus)构成姐妹群,可以单独划分为属的观点。

The Complete Mitochondrial Genome of Salt-water Crocodile (Crocodylus porosus) and Phylogeny of Crocodilians

The nucleotide sequence of the complete mitochondrial DNA (mtDNA) molecule of the salt-water crocodile (Crocodylus porosus) was determined in this article. The molecule is 16,917 base pairs (bp) in length, and codes for 22 tRNAs, 13 pro- tein-coding genes, 2 rRNAs, as well as a control region (D-loop), as is characteristic for mitochondrial genomes of other metazoans. The gene order conforms to that of other crocodilians sequenced, but the arrangement of some tRNA genes differs from other verte- brates. It shows that the gene order of crocodilians is remarkably conserved. In this study, the relationships among crocodilians were examined in the phylogenetic analysis based on the control conserved regions of 17 crocodilians. The results suggest that the gharial (Gavialis gangeticus) joins the false gharial (Tomistoma schlegelii) on a common branch, and then constitutes a sister group to tra- ditional Crocodylidae. Thus, the result supports that G. gangeticus belongs to Crocodylidae. The analyses also suggest that the Afri- can slender-snouted crocodile (Crocodylus cataphractus) can be treated as an isolated genus, and constitutes a sister group to Crocodylus.