Analysis On The Complete Mitochondrial Genome Sequences Of Six Avian Species

With more than9,000living species, Aves is the most prosperous class invertebrates. The origin and phylogenetic relationships of Aves have been extensivelyinvestigated, but some key issues remain unresolved. The mitochondrial DNA(mtDNA), with its intrinsic characteristics (small genome size, simple genomestructure, maternal inheritance mode, fast substitution rate etc), have played great rolesin taxonomic and phylogenetic researches of vertebrates. The analysis on the geneticstructure and evolutionary history of avian mitochondrial genomes can providevaluable information for molecular phylogenetic investigations and speciesconservation. To date, there were only about260avian mitogenomes have beendeposited in the GenBank, which is insufficient comparing with the huge number ofspecies. In this thesis, we obtained the complete mtDNAs of Tachybaptus ruficollis(Podicipediformes), Egretta garzetta (Ciconiiformes), Halcyon pileata, Ceryle rudis(Coraciiformes), Amaurornis phoenicurus and Amaurornis akool (Gruiformes) withPCR and sequencing techniques for the first time.The entire sequence of six birds were among16,688bp-17,612bp in length, andthey have similar composition and structure characters:(1) the genome including13protein-coding genes, two rRNA genes,22tRNA genes and a control region. Amongthem,8tRNA genes and a protein-coding gene were encoded on the L-strand, whilethe other genes were encoded on the H-strand;(2) the genome showed AT preferencewith an AT content of53.7%~57.5%comparing with a GC content of42.5%~46.3%;(3) the control region can be divided into three different domains(Domain I-III),including a putative termination-associated sequence (TAS), several conservedsequence boxes ((F, E, D, C and1), the origin of H-strand replication (OH) and thebidirectional light-and heavy-strand transcription promoters (LSP/HSP). Thesefeatures consisted with the characters of avian mitogenomes. However, there still weresome differences among six studied mitogenomes：(1) there was a “C” insertion at theposition174in ND3of T. ruficollis, E. garzetta, H. pileata, and there was an extra base“A” at the position175in ND3of C. rudis, while A. phoenicurus and A. akool had noany insertion at all;(2) except A. akool, there were different kinds of tandem repeatsequences in Domain III of the other five speices. Among the four avian orders involved, only the Ciconiiformes had abundantmitogenome information, we constructed the phylogenetic tree including E. garzettaand other ten species based on complete mitogenome sequences using Bayesianmethod. The results showed that:(1) In Ciconiiformes, the Ardeidae, Threskiorothidaeand Ciconiidae were all monophyletic families,(posterior probabilities=1.00);(2) InArdeidae, Egretta was more closely related to Ardea than to Nycticorax;(3) InThreskiornithidae, Platalea had more close relationship with Threskiornis than withNipponia;(4) about the relationship among three families, our results supported themore close relationship between Threskiorothidae and Ciconiidae. Most of ourconclusions were similar with those in recent molecular phylogenetic investigations onCiconiiformes. Our work provided valuable mitogenome information for molecularphylogenetic analysis of Aves, and proved the validity of complete mitogenome inphylogenetic study.