The complete mitochondrial genomes of Asio flammeus and Asio otus were sequenced and found to span 18858 bp and 18493 bp,respectively.It is surprising to find the former to be the largest among all avian mitochondrial genomes sequenced so far.The two genomes have very similar gene order with that of Gallus gallus,neither contains the pseudo control region,but both have a single extra base,namely Cytidine,at position 174 in ND3 gene.The control regions of Asio flammeus and Asio otus’ mitochondrial genomes span 3288 bp and 2926 bp respectively,which are the longest among vertebrates except for Myxine glutinosa and contribute to the large size of two genomes.The 3′end of the control region of Asio flammeus and Asio otus contains many tandemly repeated sequences,which are highly similar to a putative control element,i.e.Mt5,and may form stable stem-loop secondary structures.Such repeated sequences probably play an important role in regulating transcription and replication of mitochondrial genome.Our results may provide important clues for uncovering the origin and evolution mechanisms of mitochondrion genome.

The taxomic classification and phylogenetic relationships within the bear family remain argumentative subjects in recent years.Prior investigation has been concentrated on the application of different mitochondrial(mt)sequence data,herein we employ two nuclear single-copy gene segments,the partial exon 1 from gene encoding interphotoreceptor retinoid binding protein(IRBP)and the complete intron 1 from transthyretin(TTR)gene,in conjunction with previously published mt data,to clarify these enigmatic problems.The combined analyses of nuclear IRBP and TTR datasets not only corroborated prior hypotheses,positioning the spectacled bear most basally and grouping the brown and polar bear together but also provided new insights into the bear phylogeny,suggesting the sister-taxa association of sloth bear and sun bear with strong support.Analyses based on combination of nuclear and mt genes differed from nuclear analysis in recognizing the sloth bears as the earliest diverging species among the subfamily ursine representatives while the exact placement of the sun bear did not resolved.Asiatic and American black bears clustered as sister group in all analyses with moderate levels of bootstrap support and high posterior probabilities.Comparisons between the nuclear and mtDNA findings suggested that our combined nuclear dataset have the resolving power comparable to mtDNA dataset for the phylogenetic interpretation of the bear family.As can be seen from present study,the unanimous phylogeny for this recently derived family was still not produced and additional independent genetic markers were in need.

Phylogenetic relationships among 37 living species of order Carnivora spanning a relatively broad range of divergence times and taxonomic levels were examined using nuclear sequence data from exon 1 of the IRBP gene(1.3kb)and first intron of the TTR gene(1kb).These data were used to analyze carnivoran phylogeny at the family and generic level as well as the interspecific relationships within recently derived Felidae.Phylogenetic results using a combined IRBP + TTR dataset strongly supported within the superfamily Califormia,the red panda as the closest lineage to procyonid-mustelid(i.e.,Musteloidea)clade followed by pinnipeds(Otariidae and Phocidae),Ursidae(including the giant panda),and Canidae.Four feliform families,namely the monophyletic Herpestidae,Hyaenidae,and Felidae,as well as the paraphyletic Viverridae were consistently recovered convincingly.The utilities of these two gene segments for the phylogenetic analyses were extensively explored and both were found to be fairly informative for higher-group associations within the order Carnivora,but not for those of low level divergence at the species level.Therefore,there is a need to find additional genetic markers with more rapid mutation rates that would bediagnostic at deciphering relatively recent relationships within the Carnivora.

利用Long-PCR和PrimerWalking结合克隆测序法对短耳鸮和长耳鸮线粒体基因组进行了全序列测定，结果表明：短耳鸮mtDNA序列全长为18858bp，长耳鸮mtDNA全长为18493bp，其中短耳鸮mtDNA是目前已知最长的鸟类线粒体基因组，两种鸮类的基因组结构和基因排列顺序与家鸡相同，无假控制区，在ND3基因174位点都存在一个额外插入的胞苷酸（C）.控制区序列异常增大是造成这两种鸟类mtDNA增大的主要原因，短耳鸮控制区长度为3288bp，长耳鸮为2926bp，这是目前已知的脊椎动物线粒体基因组中仅次于盲鳗的最大的控制区，在其控制区3，端存在大量的串联重复序列，分析发现这两种鸮类的重复序列和Mt5调控元件有较高的序列相似性，且能形成多重的茎环二级结构，这表明该重复序列可能具有一定的生理功能，影响线粒体基因组的复制或转录表达，从而使相应物种具有更大的选择优势，以适应环境和生存竞争．