Similar Mutation Rates but Highly Diverse Mutation Spectra in Ascomycete and Basidiomycete Yeasts
Journal Article - Open Access
Department of Biology, Indiana University Bloomington United States
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Yeast species are extremely diverse and not monophyletic. Because the majority of yeast research focuses on ascomycetes, the mutational determinants of genetic diversity across yeast species are not well understood. By combining mutation-accumulation techniques with whole-genome sequencing, we resolved the genomic mutation rate and spectrum of the oleaginous oil-producingred yeast Rhodotorula toruloides, the first such study in the fungal phylum Basidiomycota. We find that the mutation spectrum is quite different from what has been observed in all other studied unicellular eukaryotes, but similar to that in most bacteria predominance of transitions relative to transversions. Rhodotorula toruloides has a significantly higher ATGC transition rate possibly elevated by the abundant flanking GC nucleotides in the GC-rich genome, as well as a much lower GCTA transversionrate. In spite of these striking differences, there are substantial consistencies between R. toruloides and the ascomycete model yeasts a spontaneous base-substitution mutation rate of 1.9010 10 per site per cell division as well as an elevated mutation rate at nonmethylated5CpG3 sites. These results imply the evolution of variable mutation spectra in the face of similar mutation rates in yeasts.