雀科9种鸟类11个线粒体tRNA基因序列及二级结构比较研究

利用PCR方法对雀科9种鸟类11个线粒体基因组中3个主要的tRNA基因簇,即IQM(tRNAIle-tRNAGln-tRNAMet),WANCY(tRNATrp-tlRNAAla-tRNAsn-tRNACyB-tRNATyr)和HSL(tRNAHis-tRNASer(AGY)-tRNALeu(CUN))进行扩增和序列测定,这些tRNA基因序列中可变核苷酸位点占15%,其中59%出现在环区,且存在插入核苷酸;茎区相对保守,其中一些变异如双链的互补性碱基突变,G-u配对等对于维系tRNA二级结构的稳定性非常重要.利用11个线粒体tRNA基因全序列,以鹌鹑为外群构建了雀科9种鸟类的系统发育树,结果表明:黄雀与其它物种关系较远;鹀亚科中灰头鹀与雀亚科关系最近,而小鹀与三道眉草鹀比较特化,这与根据二级结构特征得出的结论相吻合.利用茎区序列构建的NJ树在鹀亚科物种的分类地位上存在分歧,可能是由于核苷酸数目较少,信息量小,在解决近缘物种间的分类地位时受到限制.结合线粒体tRNA基因二级结构特征比较和系统发育分析,初步认为线粒体tRNA基因二级结构特征对于推断雀科属间的分类地位具有较高的置信度.

Comparative Study of Eleven Mitochondrial tRNA Gene Sequences and Secondary Structures in Nine Species of Fringillidae

Three major clusters of eleven mitochondrial tRNA genes (tRNA~(Ile)-tRNA~(Gln)-tRNA~(Met), tRNA~(Trp)-tRNA~(Ala)-tRNA~(Asn)-tRNA~(Cys)-tRNA~(Tyr) and tRNA~(His)-tRNA~(Ser(AGY))-tRNA~(Leu(CUN))) from nine species in Fringillidae were amplified and sequenced. About 15% of these sequences were variable, 59% of which were involved in the loop regions. The stem regions were relatively conserved, and the variable base-pair mutations were under the restriction of compensatory changes or G-U wobble pairing. Maximum-parsimony and Maximum-likelihood analyses of these (tRNA gene) sequences with Coturnix coturnix as outgroup yielded a phylogenetic tree similar to that constructed by Neighbor-joining (NJ) method, except for the relationship among Emberizinae taxa. The comparison of the secondary structure characters revealed that the relationship of the nine species is consistent with that of the phylogenetic analysis, e.g.Carduelis sinica has a distant relationship with other Fringillidae taxa, Emberiza spodocephala and Emberiza pusilla were specialized species within Emberizinae. This suggests that the characters of the secondary structure may provide phylogenetic information on relatively short internal branches below the genus level. The NJ tree constructed by stem-forming nucleotides did not well resolve the relationship among species with Emberizinae. Based on our results, stem sequences may be only available at genus or higher level, and the secondary-structure characters may be useful to determine the relationship among different genera in Fringillidae with higher phylogenetic performance.