Quantification and evolution of mitochondrial genome rearrangement in Amphibians.

BACKGROUND: Rearrangement is an important topic in the research of amphibian mitochondrial genomes ("mitogenomes" hereafter), whose causes and mechanisms remain enigmatic. Globally examining mitogenome rearrangements and uncovering their characteristics can contribute to a better understanding of mitogenome evolution. RESULTS: Here we systematically investigated mitogenome arrangements of 232 amphibians including four newly sequenced Dicroglossidae mitogenomes. The results showed that our new sequenced mitogenomes all possessed a trnM tandem duplication, which was not exclusive to Dicroglossidae. By merging the same arrangements, the mitogenomes of ~ 80% species belonged to the four major patterns, the major two of which were typical vertebrate arrangement and typical neobatrachian arrangement. Using qMGR for calculating rearrangement frequency (RF) (%), we found that the control region (CR) (RF = 45.04) and trnL2 (RF = 38.79) were the two most frequently rearranged components. Forty-seven point eight percentage of amphibians possessed rearranged mitogenomes including all neobatrachians and their distribution was significantly clustered in the phylogenetic trees (p < 0.001). In addition, we argued that the typical neobatrachian arrangement may have appeared in the Late Jurassic according to possible occurrence time estimation. CONCLUSION: It was the first global census of amphibian mitogenome arrangements from the perspective of quantity statistics, which helped us to systematically understand the type, distribution, frequency and phylogenetic characteristics of these rearrangements.

qMGR: A new approach for quantifying mitochondrial genome rearrangement.

Rearrangement is one of the most studied features in the animal mitochondrial genomes. The progress in high-throughput sequencing and comparative genomics has brought opportunities for systematic studies of mitochondrial genome rearrangements. However, there are few reports on globally examining mitogenome rearrangement and distinguishing the rearrangement frequency of each gene, which could contribute to a better understanding of its models and evolution. We presented qMGR, a new approach for large-scale quantifying mitogenome rearrangements considering a single gene as a structural unit. Compared to a reference arrangement, qMGR accumulates the changes of two nearest neighbor genes to calculate rearrangement score (RS) and rearrangement frequency (RF) of each single gene in the mitogenomes of a given taxonomic group. By accumulating RS of all genes in one genome, qMGR was developed to calculate each mitogenome rearrangement score, which can be used as a quantitative feature of the mitogenome rearrangement. Based on the frequency of rearrangement of each gene, qMGR can further detect the conserved gene set and high frequency rearrangement segments within the taxon. They may facilitate the assessment of rearrangement distances and understanding rearrangement mechanisms. qMGR web service is freely available at http://qmgr.hnnu.edu.cn/. The source code is available under GNU GPL at https://github.com/zhanglab2019/qMGR.