Alveolate and chlorophycean mitochondrial cox2 genes split twice independently.

Area of Science:

• Evolutionary Biology
• Genomics
• Molecular Biology

Background:

• The mitochondrial gene for cytochrome c oxidase subunit II (COXII) is typically encoded in the organelle genome.
• In Apicomplexa and Chlorophyceae, cox2 is split into two genes, encoded in the nucleus, a rare genomic change (RGC) used in phylogenetic studies.
• Interpreting RGCs requires accurate sampling, and dinoflagellates, as sister taxa to Apicomplexa, are crucial for understanding the cox2 rearrangement.

Purpose of the Study:

• To present the first complete cox2 data from dinoflagellates.
• To clarify the evolutionary history of the split cox2 gene.
• To reassess the proposed lateral gene transfer event.

Main Methods:

• Phylogenetic analysis of cox2 gene sequences.
• Comparative genomics of organelle and nuclear genomes.
• Bioinformatic analysis of gene structure and organization.

Main Results:

• Complete cox2 data from dinoflagellates were obtained.
• The cox2 gene in dinoflagellates exhibits a split structure similar to Apicomplexa and Chlorophyceae.
• Phylogenetic analysis indicates the gene reorganization arose independently in these lineages.

Conclusions:

• The split cox2 gene in dinoflagellates is not indicative of a shared lateral gene transfer event with Apicomplexa.
• The independent evolution of the split cox2 gene in different eukaryotic lineages highlights the plasticity of organelle genomes.
• This finding has implications for understanding the evolution of the apicomplexan apicoplast.