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Open Access Research article

Vernalization treatment induces site-specific DNA hypermethylation at the VERNALIZATION-A1 (VRN-A1) locus in hexaploid winter wheat

Abdul Rehman Khan1, Jérôme Enjalbert1, Anne-Charlotte Marsollier1, Agnès Rousselet1, Isabelle Goldringer1 and Clémentine Vitte2*

Author Affiliations

1 INRA, UMR de Génétique Végétale, Gif sur Yvette F-91190, France

2 CNRS, UMR de Génétique Végétale, Gif sur Yvette F-91190, France

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BMC Plant Biology 2013, 13:209  doi:10.1186/1471-2229-13-209

Published: 11 December 2013

Abstract

Background

Certain temperate species require prolonged exposure to low temperature to initiate transition from vegetative growth to flowering, a process known as vernalization. In wheat, winter cultivars require vernalization to initiate flowering, making vernalization requirement a trait of key importance in wheat agronomy. The genetic bases of vernalization response have been largely studied in wheat, leading to the characterization of a regulation pathway that involves the key gene VERNALIZATION1 (VRN1). While previous studies in wheat and barley have revealed the functional role of histone modification in setting VRN1 expression, other mechanisms might also be involved. Here, we were interested in determining whether the cold-induced expression of the wheat VRN-A1 gene is associated with a change in DNA methylation.

Results

We provide the first DNA methylation analysis of the VRN-A1 gene, and describe the existence of methylation at CG but also at non CG sites. While CG sites show a bell-shape profile typical of gene-body methylation, non CG methylation is restricted to the large (8.5 kb) intron 1, in a region harboring fragments of transposable elements (TEs). Interestingly, cold induces a site-specific hypermethylation at these non CG sites. This increase in DNA methylation is transmitted through mitosis, and is reset to its original level after sexual reproduction.

Conclusions

These results demonstrate that VRN-A1 has a particular DNA methylation pattern, exhibiting rapid shift within the life cycle of a winter wheat plant following exposure to particular environmental conditions. The finding that this shift occurs at non CG sites in a TE-rich region opens interesting questions onto the possible consequences of this type of methylation in gene expression.

Keywords:
VRN1; Vernalization; DNA methylation; Non CG methylation; Winter wheat; Transposable element; Triticum aestivum; Cold; Intron; Jorge; Sumaya