Similar relative mutation rates in the three genetic compartments of Mesostigma and Chlamydomonas |
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Authors: | Hua Jimeng Smith David Roy Borza Tudor Lee Robert W |
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Affiliation: | a Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada b Current address: Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada |
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Abstract: | Levels of nucleotide substitution at silent sites in organelle versus nuclear DNAs have been used to estimate relative mutation rates among these compartments and explain lineage-specific features of genome evolution. Synonymous substitution divergence values in animals suggest that the rate of mutation in the mitochondrial DNA is 10-50 times higher than that of the nuclear DNA, whereas overall data for most seed plants support relative mutation rates in mitochondrial, plastid, and nuclear DNAs of 1:3:10. Little is known about relative mutation rates in green algae, as substitution rate data is limited to only the mitochondrial and nuclear genomes of the chlorophyte Chlamydomonas. Here, we measure silent-site substitution rates in the plastid DNA of Chlamydomonas and the three genetic compartments of the streptophyte green alga Mesostigma. In contrast to the situation in animals and land plants, our results support similar relative mutation rates among the three genetic compartments of both Chlamydomonas and Mesostigma. These data are discussed in relation to published intra-species genetic diversity data for the three genetic compartments of Chlamydomonas and are ultimately used to address contemporary hypotheses on the organelle genome evolution. To guide future work, we describe evolutionary divergence data of all publically available Mesostigma viride strains and identify, for the first time, three distinct lineages of Mesostigma. |
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Keywords: | Chlamydomonas genome architecture Mesostigma mutation rate silent substitution rate |
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