Comparative analysis of mitochondrial genomes in the Ceratocystidaceae reveals highly conserved gene organization despite substantial genome size variation

Abstract

BACKGROUND : Comparative studies of mitochondrial genomes can assist in determining evolutionary and phylogenetic relationships. In the Ceratocystidaceae fungal family, mitochondrial genomes from only two genera are publicly available. In this study, mitochondrial genomes from 10 genera in Ceratocystidaceae were characterised and comparatively analysed. RESULTS : Mitochondrial (mt) genomes were fully assembled and characterized for 18 species and 10 genera of the Ceratocystidaceae. These mt genomes displayed a remarkable level of diversity owing to the variation in the intergenic regions and intron, both in size and number. Despite large variation in size, these mt genomes displayed high levels of synteny and sequence conservation in the oxidative phosphorylation (OXPHOS) genes and the ribosomal RNA and tRNA genes. The genes are found in identical order and orientation in all mt genomes characterized and the coding sequence of all the OXPHOS genes are highly conserved. Phylogenetic analysis of mitochondrial and nuclear DNA sequences reveals significant differences in evolutionary relationships among species and genera of Ceratocystidaceae. CONCLUSION : The remarkable variation in mt genome sizes in species of the Ceratocystidaceae is due to the variation observed in the intergenic regions and intron size and number in the conserved protein-coding genes. The gene order and content are identical across all species investigated.