Song Sheng-Nan, Tang Pu, Wei Shu-Jun, Chen Xue-Xin
State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China.
Institute of Plant and Environmental Protection, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China.
Sci Rep. 2016 Feb 16;6:20972. doi: 10.1038/srep20972.
The Symphyta is traditionally accepted as a paraphyletic group located in a basal position of the order Hymenoptera. Herein, we conducted a comparative analysis of the mitochondrial genomes in the Symphyta by describing two newly sequenced ones, from Trichiosoma anthracinum, representing the first mitochondrial genome in family Cimbicidae, and Asiemphytus rufocephalus, from family Tenthredinidae. The sequenced lengths of these two mitochondrial genomes were 15,392 and 14,864 bp, respectively. Within the sequenced region, trnC and trnY were rearranged to the upstream of trnI-nad2 in T. anthracinum, while in A. rufocephalus all sequenced genes were arranged in the putative insect ancestral gene arrangement. Rearrangement of the tRNA genes is common in the Symphyta. The rearranged genes are mainly from trnL1 and two tRNA clusters of trnI-trnQ-trnM and trnW-trnC-trnY. The mitochondrial genomes of Symphyta show a biased usage of A and T rather than G and C. Protein-coding genes in Symphyta species show a lower evolutionary rate than those of Apocrita. The Ka/Ks ratios were all less than 1, indicating purifying selection of Symphyta species. Phylogenetic analyses supported the paraphyly and basal position of Symphyta in Hymenoptera. The well-supported phylogenetic relationship in the study is Tenthredinoidea + (Cephoidea + (Orussoidea + Apocrita)).
叶蜂传统上被认为是一个并系类群，位于膜翅目昆虫的基部位置。在此，我们通过描述两个新测序的线粒体基因组，对叶蜂的线粒体基因组进行了比较分析，这两个基因组分别来自炭疽毛叶蜂（Trichiosoma anthracinum），代表锤角叶蜂科的首个线粒体基因组，以及来自三节叶蜂科的红头亚洲叶蜂（Asiemphytus rufocephalus）。这两个线粒体基因组的测序长度分别为15,392和14,864 bp。在测序区域内，炭疽毛叶蜂中的trnC和trnY被重排到trnI-nad2的上游，而在红头亚洲叶蜂中，所有测序基因都按假定的昆虫祖先基因排列方式排列。tRNA基因的重排在叶蜂中很常见。重排的基因主要来自trnL1以及trnI-trnQ-trnM和trnW-trnC-trnY这两个tRNA簇。叶蜂的线粒体基因组显示出对A和T而非G和C的偏向性使用。叶蜂物种中的蛋白质编码基因进化速率低于细腰亚目昆虫。Ka/Ks比值均小于1，表明叶蜂物种受到纯化选择。系统发育分析支持叶蜂在膜翅目中的并系性和基部位置。该研究中得到充分支持的系统发育关系是三节叶蜂总科 + （茎蜂总科 + （扁叶蜂总科 + 细腰亚目））。
