title: Identification of differentially methylated regions during vernalization revealed a role for RNA methyltransferases in bolting.
abstract: Sugar beet (Beta vulgaris altissima) is a biennial root crop with an absolute requirement for cold exposure to bolt and flower, a process called vernalization. Global DNA methylation variations have been reported during vernalization in several plants. However, few genes targeted by DNA methylation during vernalization have been described. The objectives of this study were to identify differentially methylated regions and to study their involvement in bolting induction and tolerance. Restriction landmark genome scanning was applied to DNA from shoot apical meristems of sugar beet genotypes, providing a direct quantitative epigenetic assessment of several CG methylated genes without prior knowledge of gene sequence. Several differentially methylated regions exhibiting variations of gene-body DNA methylation and expression during cold exposure and/or between genotypes were identified, including an AROGENATE DEHYDRATASE and two RNA METHYLCYTOSINE TRANSFERASE sequences. One RNA METHYLCYTOSINE TRANSFERASE sequence displayed gene-body hypermethylation and activation of expression, while the other was hypomethylated and inhibited by cold exposure. Global RNA methylation and phenolic compound levels changed during cold exposure in a genotype-dependent way. The use of methyl RNA immunoprecipitation of total RNA and reverse transcription-PCR analysis revealed mRNA methylation in a vernalized bolting-resistant genotype for the FLOWERING LOCUS 1 gene, a repressor of flowering. Finally, Arabidopsis mutants for RNA METHYLCYTOSINE TRANSFERASE and AROGENATE DEHYDRATASE were shown to exhibit, under different environmental conditions, early or late bolting phenotypes, respectively. Overall, the data identified functional targets of DNA methylation during vernalization in sugar beet, and it is proposed that RNA methylation and phenolic compounds play a role in the floral transition.
authors: Université d'Orléans, UFR/Faculté des Sciences, UPRES EA 1207 Laboratoire de Biologie des Ligneux et des Grandes Cultures, INRA USC1328 ARCHE, rue de Chartres, BP6759, 45067 Orléans cedex 2,  France.
authors: Claire
authors: C
authors: Hébrard
authors: Marie-Véronique
authors: MV
authors: Trap-Gentil
authors: Clément
authors: C
authors: Lafon-Placette
authors: Alain
authors: A
authors: Delaunay
authors: Claude
authors: C
authors: Joseph
authors: Marc
authors: M
authors: Lefèbvre
authors: Steve
authors: S
authors: Barnes
authors: Stéphane
authors: S
authors: Maury
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D027461:Beta vulgaris / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D035264:Flowers / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D018749:RNA, Plant; D008780:Methyltransferases