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RESEARCH PRODUCT

Roles of adenosine and cytosine methylation changes and genetic mutations in adaptation to different temperatures

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Abstract Epigenetic modifications have been found to be involved in evolution, but the relative contributions of genetic and epigenetic variation in adaptation are unknown. Furthermore, previous studies on the role of epigenetic changes in adaptation have nearly exclusively focused on cytosine methylation in eukaryotes. We collected phenotypic, genetic, and epigenetic data from populations of the bacterium Serratia marcescens that had undergone experimental evolution in contrasting temperatures to investigate the relationship between environment, genetics, epigenetic, and phenotypic traits. The genomic distribution of methylated adenosines (m6A) pointed to their role in regulation of gene expression, while cytosine methylation (m4C) likely has a different role in S. marcescens . We found both environmentally induced and likely spontaneous methylation changes. There was very little indication that methylation changes were under genetic control. Decomposition of phenotypic variance suggested that both genetic and epigenetic changes contributed to phenotypic variance with slightly higher contribution from genetic changes. Overall, our results suggest that while genetic changes likely are responsible for the majority of adaptation, adenosine methylation changes have potential to contribute to adaptation as well.