Mitochondrial Genomes in Perkinsus Decode Conserved Frameshifts in All Genes

Area of Science:

• Mitochondrial genomics
• Organelle evolution
• Molecular biology

Background:

• Myzozoa (apicomplexans, dinoflagellates, chrompodellids) have reduced mitochondrial genomes with unique features.
• The mitochondrial genome of early-diverging Perkinsozoa remained poorly characterized, with prior gene studies suggesting novel traits like frameshifts.

Purpose of the Study:

• To characterize the mitochondrial genomes of four Perkinsus species.
• To identify ancestral myzozoan and novel perkinsozoan mitochondrial genome features.
• To investigate the role and mechanism of frameshifts in Perkinsus mitochondrial gene expression.

Main Methods:

• Sequencing and assembly of four Perkinsus species' mitochondrial genomes.
• Bioinformatic analysis to identify gene content, frameshifts, and codon usage.
• Comparative genomic analysis to infer evolutionary trajectories.

Main Results:

• Characterized simple ancestral mitochondrial genomes with reduced coding capacity and propensity for rearrangement.
• Identified 75 conserved frameshifts across species, with a decoding mechanism using unused codons to advance translation.
• Observed a lack of cysteine codons, reducing the amino acid repertoire to 19, and incomplete mitochondrial rRNAs, with some potentially imported from the nucleus.

Conclusions:

• Perkinsus mitochondrial genomes exhibit unique evolutionary paths, including extensive use of frameshift translation for gene expression.
• Frameshifts appear strategically located to regulate nascent protein folding.
• Organelle genome evolution in Myzozoa is diverse, with Perkinsus showcasing remarkable adaptations.