General features and evolution of mitochondrial genomes in Dictyostelia (Amoebozoa)

Dictyostelia exhibits high diversity; however, mitochondrial genome data remain scarce for many genera. Although key features of some dictyostelid mitogenomes have been identified, several aspects remain unclear, including core gene content, segmental arrangement, and differences between 18S rRNA and mitochondrial gene phylogenies. To address these gaps, we reconstructed two complete mitogenomes-from Cavenderia subdiscoidea and Dictyostelium sp. (TH18CC)-and analyzed mitochondrial genes from ten genera and six additional complete mitogenomes from public databases. A comparison of eight complete mitogenomes revealed a conserved core of 39 protein-coding genes, 17 tRNA genes, and three rRNA genes. Two distinct segmental arrangements were identified: Dictyostelium (except D. purpureum) exhibits an A-C-B pattern, while other genera display an A-B-C pattern defined by the clusters nad9-atp1, trnC(GCA)-atp9, and rnl-nad3. Phylogenetic analyses based on 18S rDNA and mitochondrial rns suggest the transposition between segments B and C occurred after D. purpureum diverged from other Dictyostelium species, potentially involving tRNA gene displacement. In contrast, the mitochondrial protein-coding gene phylogeny differs from the rRNA trees, indicating that these gene sets may have evolved independently. These findings advance our understanding of dictyostelid mitogenome structure and evolution.