番石榴实蝇和瓜实蝇的线粒体L-rRNA基因测序及双翅目昆虫L-rRNA基因的结构特征与系统发育关系分析

RNA二级结构比一级结构包含更多的信息, 在物种系统发育分析中更能反应真实情况。因而, 本研究对番石榴实蝇Bactrocera correcta和瓜实蝇B. cucurbitae的L-rRNA全基因进行了测序, 构建了双翅目L-rRNA基因二级结构的模式图, 并分析了其结构特征, 而后基于H45~H47茎环结构参数和结构序列及L-rRNA结构序列对双翅目13科的系统发育关系进行了初步分析。结果表明： 双翅目昆虫具有保守的L-rRNA二级结构; 不同结构区碱基组成和分布不均匀, Ⅳ区和Ⅴ区的完全保守碱基含量最高, GC含量最高, 绝大部分科Ⅵ区的AT斜率均小于0; 科内特有碱基和科间少数保守碱基大部分为G或C。瘿蚊科与双翅目其他科具有较远的系统发育关系, 而丽蝇科、 寄蝇科和食蚜蝇科有相近的系统发育关系; 虻科与网翅虻科同在一个小分支; 蠓科与蚊科同在一个大的系统发育分支。利用单方面参数不易得到理想的进化结果, 准确系统发育分析需要结合多方面的参数。

Sequencing of mitochondrial L-rRNA genes of Bactrocera cucurbitae and B. correcta (Diptera: Tephritidae ) and the analysis of structural characteristics and phylogenetic relationship of L-rRNA genes in dipterans

The RNA secondary structure contains more information than its primary structure, and can indicate the phylogenetic relationship more really. Therefore, the complete sequences of mitochondrial L-rRNA genes of Bactrocera cucurbitae and B. correcta were sequenced in this study, and the structural model of L-rRNA genes in Diptera was constructed. The characteristics of L-rRNA secondary structure was analyzed, and preliminary phylogenetic features were inferred based on stem-loop parameters and structural sequences of H45-H47, and structural sequences of L-rRNA genes among 13 families in Diptera. The results showed that the dipterans share the conserved secondary structure of L-rRNA gene; the nucleotide composition and distribution vary within different structure regions of L-rRNA gene; the highest content of completely conserved nucleotides was found in region Ⅳ and Ⅴ; the region Ⅳ and Ⅴ also contains the highest GC content; the AT-skew is negative in region Ⅵ of L-rRNA gene of the majority of dipteran families; the unique bases within individual family and individually conserved nucleotides between families present higher content of G or C. The family Cecidomyiidae exhibits much farther distance with other dipteran families, while Calliphoridae, Tachinidae and Syrphidae share much closer phylogenetic relationship; Tabanidae and Nemestrinidae belong to a small branch; Ceratopogonidae and Culicidae share a large phylogenetic branch. The satisfied phylogenetic result would not be obtained easily using single phylogenetic parameter, and it is thus necessary to infer accurate phylogenesis through combined parameters of different features.