Red Algal Mitochondrial Genomes Are More Complete than Previously Reported

Area of Science:

• Evolutionary biology
• Genomics
• Molecular biology

Background:

• Mitochondrial genomes evolved from endosymbiotic alpha-proteobacteria, undergoing gene transfer and reduction.
• Most mitochondrial gene loss occurred early in eukaryotic evolution, but later modifications are phylogenetically informative.
• Previous studies reported significant gene loss or pseudogenes in Florideophyceae mitochondrial genomes.

Purpose of the Study:

• To investigate reported gene losses in Florideophyceae mitochondrial genomes.
• To re-examine mitochondrial genome completeness in red algal parasites and their hosts.
• To clarify the evolutionary history of mitochondrial gene content in red algae.

Main Methods:

• Sequencing of mitochondrial genomes from Choreocolax polysiphoniae and Vertebrata lanosa.
• Resequencing of Gracilariophila oryzoides and Gracilariopsis andersonii.
• Reannotation of published Florideophyceae mitochondrial genome data.

Main Results:

• Mitochondrial genomes of Choreocolax polysiphoniae and Vertebrata lanosa were found to be complete and conserved.
• Reannotation and resequencing identified the majority of previously reported lost or pseudogene genes in Florideophyceae mitochondria.
• Multiple independent losses of rpl20 and a single loss of rps11 were confirmed, but overall gene loss was overestimated.

Conclusions:

• The extent of gene loss in Florideophyceae mitochondrial genomes has been previously overestimated.
• Mitochondrial genomes in red algae are more conserved than previously thought.
• This study refines our understanding of mitochondrial genome evolution and gene loss dynamics in eukaryotes.