title: Spontaneous Mutation Rate in the Smallest Photosynthetic Eukaryotes.
abstract: Mutation is the ultimate source of genetic variation, and knowledge of mutation rates is fundamental for our understanding of all evolutionary processes. High throughput sequencing of mutation accumulation lines has provided genome wide spontaneous mutation rates in a dozen model species, but estimates from nonmodel organisms from much of the diversity of life are very limited. Here, we report mutation rates in four haploid marine bacterial-sized photosynthetic eukaryotic algae; Bathycoccus prasinos, Ostreococcus tauri, Ostreococcus mediterraneus, and Micromonas pusilla. The spontaneous mutation rate between species varies from μ = 4.4 × 10-10 to 9.8 × 10-10 mutations per nucleotide per generation. Within genomes, there is a two-fold increase of the mutation rate in intergenic regions, consistent with an optimization of mismatch and transcription-coupled DNA repair in coding sequences. Additionally, we show that deviation from the equilibrium GC content increases the mutation rate by ∼2% to ∼12% because of a GC bias in coding sequences. More generally, the difference between the observed and equilibrium GC content of genomes explains some of the inter-specific variation in mutation rates.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, Banyuls/Mer, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Krasovec
authors.affiliation: Evolution, behaviour and environment, School of Life Sciences, University of Sussex, Brighton, United Kingdom.
authors.forename: Adam
authors.initials: A
authors.lastname: Eyre-Walker
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, Banyuls/Mer, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Sanchez-Ferandin
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, Banyuls/Mer, France.
authors.forename: Gwenael
authors.initials: G
authors.lastname: Piganeau
mesh_terms: D001482:Base Composition / Q000235:genetics; D000460:Chlorophyta / Q000235:genetics*; D021901:DNA, Intergenic / Q000235:genetics; D056890:Eukaryota / Q000235:genetics; D019143:Evolution, Molecular; D014644:Genetic Variation; D016678:Genome / Q000235:genetics; D009154:Mutation; D059645:Mutation Rate; D010788:Photosynthesis / Q000235:genetics*
chemical_list: D021901:DNA, Intergenic
keywords: GC bias; GC content; Mamiellophyceae; deletion bias; mutation accumulation; phytoplankton; spontaneous mutation rate; transcription-coupled DNA repair