Complete Mitochondrial Genome Sequence Of Schlechtendalia Chinensis And Evolutionary Analysis

The Rhus gall aphids (Insecta, Homoptera, Pemphigidae, section five root aphid subfamily Fordinae) is the important economic aphids for their applications in the area of medical and chemical industry. In their life cycles, the Rhus gall aphids transfer hosts between the primary hosts-Rhus species and the secondary hosts-moss species. This aphid group includes6genus14species, and mostly distribute in East-Asia exception for one species in North Amarica, among which the species Schlechtendalia chinensis is widely distributed. Its primary host is Rhus chinensis, and the secondary host is Mniaceae. Until now, the research on the complete mitochondrial genome of Schlechtendalia chinensis has not been reported.In cell biology, a mitochondrion (plural mitochondria) is a membrane enclosed organelle found in most eukaryoticcells, whose size is around15-20kb. Mitochondria are sometimes described as "cellular power plants" because they generate most of the cell’s supply ofadenosine triphosphate (ATP), used as a source of chemical energy. Mitochondrial genome usually contain protein coding genes (PCG), transfer RNA (tRNA), ribosomal RNA (rRNA), Control Region or A+T rich. The part of the protein coding region and A+T rich area is more conservative, so the complete mitochondrial genome has important significance for the research of molecular.In this study, we sequenced the complete mitochondrial genome sequence of Schlechtendalia chinensis by PCR technology and cloning method. The main results are as following:1. The whole mitochondrial genome sequence of Schlechtendalia chinensis is15,568bp (one fragment was not obtained), which is a closed circular double-stranded DNA structure. The mitochondrial genome contains37genes, including13protein coding genes,22tRNA genes,2rRNA gene and an A+T rich. In the coding region, the content of AT%is high (reaching83%), which comform the common characteristic of insect mitochondrial gene. From the composition of protein coding region, the AT%of A+T rich is88.6%, which is the highest of the coding regions.2. All the13protein coding genes are observed to use ATA, ATG, ATT and TAA as initiation codon. And the terminators are T, TAA and ATG, respectively. In the coding regions, Cytb, COI, COII, COIII are conserved. The rRNA sequences account for6.5%of the total mitochondrial genome.3. Using the tRNAscan-SE online, the22tRNA are consistent with other aphids. The length of tRNA is about60-70bp. In all the tRNA, there are5tRNA genes (Asp, Ala, Glu, Thr and Trp) positioned in the light chain (L). All the tRNAs are folded in the form of a typical clover leaf structure.4. From the GenBank, we download the whole mitochondrial genome sequences of the two aphids species Acyrthosiphon pisum and Schizaphis graminum. Comparing with the two sequences, the following results were obtained:First, the length of Acyrthosiphon pisum mtDNA genome sequence is longer than the other two. Second, the A+T rich region and ND2of Schlechtendalia chinensis is different with other aphids. Finally, in case of the initiation and termination codon, the three species of aphids are the same, except for the ND1and ND2of Schlechtendalia chinensis using T as termination codon. The genome organization of Acyrthosiphon pisum is different from Schlechtendalia chinensis, suggesting that the evolution of Acyrthosiphon pisum is earlier than others. In addition, the location of ND2and tRNA also played a positive role in the evolution of aphids.