Study On The Mitochondrial Genomes Of Representative Aphid Species(Hemiptera: Aphidoidea And Adelgoidea)

Mitochondrial genome has been generally applied in biological systemtics due to its unique properties, including simple genomic organization, maternal inheritance, high evolutionary rate as well as no genetic recombination, repeat DNA and introns. Although mitochondrial genome is small, it contains abundant signals for resolving phylogenetic relationships, such as nucleotide sequences, gene content, and gene arrangement. In published mitochondrial genomes of Hemiptera, obvious gene rearrangements are found in Sternorrhyncha, such as protein coding genes and tRNAs. While in Clypeorrhyncha and Reduviidae, gene arrangements are consistent with that of the putative arthropoda ancestor except some tRNA genes. For the published mitochondrial genomes of three aphid species, i.e. Acyrthosiphon pisum (Harris), Schizaphis graminum (Rondani) and Daktulosphaira vitifoliae (Fitch), their gene arrangements and contents are consistent with that of the putative arthropoda ancestor, except the mitochondrial genome of A. pisum contains three tRNA-Met.Comparing with other mitochondrial genomes of Hemiptera species, the conclusions can accumulate basic data for phylogenetic study of aphid. In the present study, mitochondrial genomes of three aphid species, i.e. Aphis glycines Matsmura, Eriosoma lanigerum (Hausmann), Adelges laricis (Vall), were sequenced by using Long PCR and primer walking. About 90%, 38% and 36% of the mitochondrial genome of Aphis glycines Matsmura, Eriosoma lanigerum (Hausmann) and Adelges laricis (Vall) were obtained. Comparing with other published mitochondrial genomes of Hemiptera species, the following conclusions were drawn.1. All the three genomes contain the general genes in metazoan mitochondrial genome. The A. glycines mitochondrial genome is closed circular double-strand DNA molecules, containing 13 protein coding genes, 2 ribosomal RNA genes, and 15 transfer RNA genes.2. Gene arrangements of the A. glycines mitochondrial genome is consistent with that of the putative arthropoda ancestor; however, local or remote inversion for COⅢ-G-ND3-A may occur in E. lanigerum, and local or remote inversions for ATP8-ATP6, ND3-A-R may occur in A. laricis. Comparing the gene arrangements of Hemiptera, inversion for COⅢ-G-ND3-A, is found in E. lanigerum and Aleyrodidae species, and local inversion for T-P-ND6, exchanging position for tRNA-W and tRNA-C are found in Delphacidae.3. Gene overlap (TTAACAT) between ND4 and ND4L is found in the A. glycines mitochondrial genome, but the overlapping sequence is different from other insects. The number of gene overlap of ATP8/ATP6 is 17 in the A. laricis mitochondrial genome.4. Fifteen tRNAs except tRNA-W of the A. glycines mitochondrial genome fold into clover-leaf structure. The secondary structure of some tRNA genes contains unmatched base pairs (G=U, A=A, U=C, U=U, C=A), small loop and short arm. For example, small loop is found in the secondary structure of tRNA-L, tRNA-D and tRNA-I, the lost stem of TψC arm is found in tRNA-W. The absent stem of DHU arm is found in tRNA-S of E. lanigerum. The above characters are generally found in Hemiptera.5. The A. glycines mitochondrial genome contains two tRNA-L, anticodons are UAA and UAG; the E. lanigerum mitochondrial genome contains two tRNA-S, anticodons are GGA and UGA.6. All protein coding genes of the A. glycines mitochondrial genome start with a typical ATN codon. The usual TAA termination codon is found in eight protein coding genes. However, the COI, ND4, CYTB, ND2 genes have an incomplete termination codon (T).7. In the A. glycines mitochondrial genome, the most frequently used codon is AAA, which code the amino acids Leu.8. The most frequently used codon do not always correspond with their cognates in the mitochondrial tRNAs.9. The 16S rRNA with 1262bp in length locates between tRNA-L and tRNA-V, 12S rRNA of 611bp locats between tRNA-V and control region, and the AT content respectively is 84.9% and 82.7%.