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Abstract:
Mutations are the source of genetic variation and the substrate for evolution. Genome-widemutation rates appear to be affected by selection and are probably adaptive. Mutation ratesare also known to vary along genomes, possibly in response to epigenetic modifications, butcausality is only assumed. In this study we determine the direct impact of epigenetic mod-ifications and temperature stress on mitotic mutation rates in a fungal pathogen using amutation accumulation approach. Deletion mutants lacking epigenetic modifications confirmthat histone mark H3K27me3 increases whereas H3K9me3 decreases the mutation rate.Furthermore, cytosine methylation in transposable elements (TE) increases the mutation rate15-fold resulting in significantly less TE mobilization. Also accessory chromosomes havesignificantly higher mutation rates. Finally, wefind that temperature stress substantiallyelevates the mutation rate. Taken together, wefind that epigenetic modifications andenvironmental conditions modify the rate and the location of spontaneous mutations in thegenome and alter its evolutionary trajectory.
