Complete mitogenome sequences of four flatfishes (Pleuronectiformes) reveal a novel gene arrangement of L-strand coding genes
1 CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, PR China
2 Heilongjiang River Fisheries Research Institute, Chinese Academy of Fishery Science, 232 Hesong Street, Harbin 150070, PR China
3 Key Laboratory of Sustainable Utilization of Technology Research for Fishery Resource of Zhejiang Province, Marine Fisheries Research Institute of Zhejiang, Zhoushan 316100, China
BMC Evolutionary Biology 2013, 13:173 doi:10.1186/1471-2148-13-173Published: 20 August 2013
Few mitochondrial gene rearrangements are found in vertebrates and large-scale changes in these genomes occur even less frequently. It is difficult, therefore, to propose a mechanism to account for observed changes in mitogenome structure. Mitochondrial gene rearrangements are usually explained by the recombination model or tandem duplication and random loss model.
In this study, the complete mitochondrial genomes of four flatfishes, Crossorhombus azureus (blue flounder), Grammatobothus krempfi, Pleuronichthys cornutus, and Platichthys stellatus were determined. A striking finding is that eight genes in the C. azureus mitogenome are located in a novel position, differing from that of available vertebrate mitogenomes. Specifically, the ND6 and seven tRNA genes (the Q, A, C, Y, S1, E, P genes) encoded by the L-strand have been translocated to a position between tRNA-T and tRNA-F though the original order of the genes is maintained.
These special features are used to suggest a mechanism for C. azureus mitogenome rearrangement. First, a dimeric molecule was formed by two monomers linked head-to-tail, then one of the two sets of promoters lost function and the genes controlled by the disabled promoters became pseudogenes, non-coding sequences, and even were lost from the genome. This study provides a new gene-rearrangement model that accounts for the events of gene-rearrangement in a vertebrate mitogenome.