Evolutionary Patterns Of The Mitochondrial Genome In Three Kinds Of Mites

Mitochondrion is a ubiquitous organelle in eukaryotic cells,aerobic mitochondria serve as the power sources of eukaryotes by producing ATP through oxidative phosphorylation(OXPHOS).Mitochondrial DNA(mtDNA)has extensively been used as a tool to study molecular ecology?population genetics?and phylogeography of organisms for over three decades,because of three advantages of mtDNA:maternal inheritance,approximate molecular clock with high rate variability and near neutral evolution.With the extensive application of mitochondrial molecular markers in various taxa and extensive research on mitochondrial function,researchers question the accuracy of these three features.Especially the neutral evolution theory of mitochondria,more and more researchs find that the mitochondrial genome,while universally strong negative selection,but also by some positive selection occasionally.Currently,the mechanism of mitochondrial evolutionary selection is not clear,we suspect that different climate of distribution area may have a great influence on the evolution pattern of mitochondrial genome.In order to reveal whether climate have an influence on mitochondria evolutionary patterns,in this study,we choose three species which distributed in different areas as experimental material.Through genome sequencing and whole mitochondrial stress analysis,we compare the diversity of three kinds of spider mites mitochondral genome and evolutionary patterns.The main results are as follows:1.We have sequenced 29 haplotypes of Teranychus truncates,16 haplotypes of Tetranychus pueraricola and 15 haplotypes of Panonychus citri using the second generation sequencing.We contrast the pattern of sequence diversity within three species,using data from all 13 coding genes.The ratio of synonymous non-synonymous changes of P.citri is always higher than that of T.pueraricola and T.truncates.Distribution pattern of synonymous mutation rate on 13 protein-coding genes in three kinds of spider mites is similar.There is a big difference existing in synonymous mutation rate distribution pattern of three spider mites,suggesting that the pattern of mitochondria selection may have connection with climate and environment.2.Correlation analysis indicate that the number of synonymous and nonsynonymous changes show significant linear relationship with the length of the gene;The number of non-synonymous changes is also significantly correlated with the number of synonymous changes.We analyze the linear relationship of nonsynonymous and synonymous changes,discovering that the slope coefficient is T.truncates>T.pueraricola>P.citri.These results imply that the nonsynonymous changes occur in P.citri is too much,which may lead to the dysfunction of mitochondria.T.truncates may suffer stronger negative selection than the other two species.3.The analysis basing on codon-substitution models indicate that there is a strong and wide-spreading signature of purifying selection across the 13 protein coding genes,mainly in the Complex ?(CO??CO??CO?).The key is that evidence of positive selection in genes is involved in OXPHOS complexes NADH dehydrogenate(Complex ?:ND1,ND4,ND6)against a background of strong purifying selection.The number of purifying selection sites is significantly higher than the other two species,but the number of positive selection sites is lower.In conclusion,these results suggest that climate have a significant influence on the evolutionary pattern of mitochondrial genome.