Mitochondrial Genomics Research (Hemiptera: Polygonaceae)

The aphid subfamily Hormaphidinae (Hemiptera:Aphididae) is an extraordinary aphids group, which is a good ideal model for the study of the biological evolution. It comprises three tribes (Cerataphidini, Hormaphidini and Nipponaphidini). As of January 2016, seven complete mitochondrial genomes of aphids have been reported, which does not include mitochondrial DNA of Hormaphidinae. The basic characteristics of this subfamily mitochondrial genomes based on comparative genomics and the phylogeny of this subfamily based on the detail mitochondrial genomes has not been reported.Sampled taxa in this research included species from three redefinedly tribes in Hormaphidinae (five genera of Cerataphidini; two genera of Hormaphidini; four of Nipponaphidini). Four complete and seven nearly complete mitochondrial genomes of Hormaphidinae have been obtained.All mitochondrail genome information has been annotated and it has also been analyzed by comparative genomics methods. Meanwhile molecular phylogeny of Hormaphidinae has been reconstructed based on all information above. The main results are shown as below.1. The length of mitochondrial genome of Hormaphis betulae?Cerataphis brasiliensis? Schizoneuraphis gallarum-. Neothoracaphis yanonis is respectly 15088 bp?14920 bp? 14988bp.15080 bp. Except C. brasiliensis, they have 37 genes including 13 Protein codon genes, 22 transfer RNAs,2 ribosomal RNAs and control region, which have the same order as the arrangement of Drosophila melanogaster (the putative insect ancestral).2. The start codon of 13 PCGs is one of the typical ATN codons (ATA. ATT?ATC and ATG) and the termination condons are TAA and T. The gene of the fastest evolution is nad4, contrary, the slowest is coxl.3. There is obvious codon usage preference in PCGs. The most abundant codons are NNA/NNU, which is also the kind of support of codon usage preference about Hormaphidinae.4. In H.betulae?C.brasiliensis. S.gallarum and N.yanonis, the content of AT is respectively 82.2%.84.2%,82.6%.83.9%, which also indicates the codon usage preference.5. The typical clover-leaf structure was predicted in 21 of the 22 tRNA except for trnSl (AGN) missing DHU arm. There are some non-classical base pairing in the structure of tRNA, such as A=A,G-U. Meanwhile, all of the rRNA structure is in line with the typical characteristics of aphids.6. In C. brasiliensis, the missing gene is trnG (Gly); nad3 and cox3 has an common sequence, which has 351 base overlaps.7. In Schizoneuraphis gallarum and Reticulaphis yanonis, there is tRNA-like sequence. In Schizoneuraphis gallarum, the gene sequene of trnS can encode trnW in the opposite direction; In Reticulaphis yanonis, the gene sequene of trnE can also encode trnF in the reverse direction.8. Phylogenetic tree was estimated using ML and BI based on 13 PCGs. Hormaphidinae was recovered as monophyletic. Meanwhile, the monophyly of Hormaphidini and Nipponaphidini was supported.In this study, we reported firstly the mitochondrial genome of the subfamily Hormaphidinae including three tribes and the whole mitochondrial genome were detailedly annotated. We summarized the basic characteristics of the mitochondrial genome of the subfamily Hormaphidinae by means of comparative genomics; we reconstructed the phylogenetic relationships of Hormaphidinae based on 13 PCGs, which confirmed the previous results and added to effective information for phylogeny. All in all, this study laid a foundation for the further research on the development of aphid system, the characteristics of the aphid mitochondrial genome and other evolutionary theories.