DNA methylation variation in asexual dandelion lineages

DNA methylation variation in asexual dandelion lineages Koen J.F. Verhoeven1,2, Peter J. van Dijk3 and Arjen Biere1 1 Department of Multitrophic Interactions, Netherlands Institute of Ecology (NIOO-KNAW), Heteren, The Netherlands. 2 Laboratory of Nematology, Wageningen University and Research Centre, Wageningen, The Netherlands. 3 KeyGene NV, Wageningen, The Netherlands DNA methylation is an epigenetic mechanism that plays an important role in transposon silencing and gene activity regulation in plants. Methylation patterns can be stably inherited from one generation to the next, but some genomic methylation re-patterning can occur due to genomic and environmental stresses. It has been speculated that stress-induced methylation changes are a source of heritable phenotypic variation that is generated during times of stress. However, to date there is limited insight in how flexible the methylation code is and to what degree stress-induced methylation changes are heritable. Using methylation-sensitive AFLP markers we studied stress-induced re-patterning and heritability of genomic methylation patterns in apomictic dandelions (that produce clonal seeds without fertilization). Lacking genetic variation, epigenetic variation could be a relevant source of heritable variation within asexuals. We exposed genetically identical plants from a single apomictic lineage to different experimental environments, and we asked if environment effects on methylation patterns are visible in offspring of these plants that are grown in a common control environment. While some background-level methylation change was observed also under control conditions, more methylation changes were observed in stress environments than in controls and the majority of stress-induced methylation changes were transmitted to offspring. In addition many transgenerational effects of stress on offspring phenotypes were observed. This study indicates that heritable epigenetic variation is readily generated during times of stress. Follow-up studies are planned to evaluate phenotypic consequences of this epigenetic variation, and to explore if epigenetic mechanisms mediate maternal phenotypic effects.