Molecular Diversity and Phylogeny Reconstruction of Genus Colobanthus (Caryophyllaceae) Based on Mitochondrial Gene Sequences

Mitochondrial genomes have become an interesting object of evolutionary and systematic study both for animals and plants, including angiosperms. Although the framework of the angiosperm phylogeny was built on the information derived from chloroplast and nuclear genes, mitochondrial sequences also revealed their usefulness in solving the phylogenetic issues at different levels of plant systematics. Here, we report for the first time the complete sequences of 26 protein-coding genes of eight Colobanthus species (Caryophyllaceae). Of these, 23 of them represented core mitochondrial genes, which are directly associated with the primary function of that organelle, and the remaining three genes represented a facultative set of mitochondrial genes. Comparative analysis of the identified genes revealed a generally high degree of sequence conservation. The Ka/Ks ratio was <1 for most of the genes, which indicated purifying selection. Only for rps12 was Ka/Ks > 1 in all studied species, suggesting positive selection. We identified 146-165 potential RNA editing sites in genes of the studied species, which is lower than in most angiosperms. The reconstructed phylogeny based on mitochondrial genes was consistent with the taxonomic position of the studied species, showing the separate character of the family Caryophyllaceae and close relationships between all studied Colobanthus species, with C. lycopodioides sharing less similarity.