09 June 2010
Current strategies in complex trait analysis correlate phenotypic variation to DNA sequence variation. Such an analysis can detect genomic regions causal for phenotypic variation. Unfortunately, detected genomic regions almost never explain the observed phenotypic variation completely. It is therefore an open and compelling question where the missing (unexplained) portion of the heritability originates from. In plants, variation in methylation of the DNA can have an impact on gene expression and downstream phenotypes, an effect that can be stably inherited over at least eight generations. The extent to which this source of epigenetic variation is important for phenotypic variation in ecological settings remains largely unknown. To address this, we present the first open-field study involving a large population of so-called epigenetic Recombinant Inbred Lines (epiRILs). By construction, the epiRIL are expected to be isogenic on the level of the DNA sequence but to differ in their genome-wide mehtylation patterns. Phenotypic analysis of a number of phenological, dispersal related traits, morphological, and branching pattern traits revealed substantial influence of epigenetic variation on phenotypic variation, with heritability values ranging from 0% to 28.8%. Our results suggest that epigenetic variation can cause phenotypic variation and further studies on epiRILs may be particularly helpful in gaining a more fundamental understanding of epigenetic processes and may eventually facilitate a generalization to other populations of plants or even mammals.