Spontaneous epimutations in plants

Contents Summary 1253 I. Introduction 1253 II. What is the rate and molecular spectrum of spontaneous epimutations? 1254 III. Do spontaneous epimutations have phenotypic consequences? 1257 IV. Conclusion and discussion 1258 Acknowledgements 1258 References 1258 SUMMARY: Heritable gains or losses of cytosine methylation can arise stochastically in plant genomes independently of DNA sequence changes. These so-called 'spontaneous epimutations' appear to be a byproduct of imperfect DNA methylation maintenance and epigenome reinforcement events that occur in specialized cell types. There is continued interest in the plant epigenetics community in trying to understand the broader implications of these stochastic events, as some have been shown to induce heritable gene expression changes, shape patterns of methylation diversity within and among plant populations, and appear to be responsive to multi-generational environmental stressors. In this paper we synthesized our current knowledge of the molecular basis and functional consequences of spontaneous epimutations in plants, discuss technical and conceptual challenges, and highlight emerging research directions.