Epigenetic characterization of the vegetative and floral stages of azalea buds: dynamics of DNA methylation and histone H4 acetylation.

Floral induction in plants is achieved through a complex genetic network and regulated by multiple environmental and endogenous cues. Epigenetic control is determinative in plants for coordinating the switch to flowering under favorable environmental conditions and achieving reproductive success. Global DNA methylation, whose increase is associated with heterochromatinization-cell differentiation, and histone H4 acetylation, which is linked to euchromatin, were analyzed in vegetative and floral buds of azalea in order to study the involvement of epigenetic mechanisms in the floral development of woody plants. The results showed an increase of DNA methylation in floral buds in contrast to the decrease observed for acetylated H4 (AcH4) levels. In addition, when the distributions of 5-mdC and AcH4 in vegetative and floral buds of azalea were analyzed by immunodetection, opposite patterns in their distribution were revealed and confirmed the existence of different cell types in the shoot apical meristem with varying degrees of differentiation.