The 5-methyl-deoxy-cytidine (5mdC) localization to reveal in situ the dynamics of DNA methylation chromatin pattern in a variety of plant organ and tissue cells during development

DNA methylation of cytosine residues constitutes a prominent epigenetic modification of the chromatin fiber which is locked in a transcriptionally inactive conformation leading to gene silencing. Plant developmental processes, as differentiation and proliferation, are accompanied by chromatin remodeling and epigenetic reprogramming. Despite the increasing knowledge gained on the epigenetic mechanisms controlling plant developmental processes, the knowledge of the DNA methylation regulation during relevant developmental programs in flowering Plants, such as gametogenesis or embryogenesis, is very limited. The analysis of global DNA methylation levels has been frequently conducted by high performance capillary electrophoresis, and more recently also by ELISA-based assays, which provided quantitative data of whole organs and tissues. Nevertheless, to investigate the DNA methylation dynamics during plant development in different cell types of the same organ, the analysis of spatial and temporal pattern of nuclear distribution of 5-methyl-deoxy-cytidine (5mdC) constitutes a potent approach. In this work, immunolocalization of 5mdC on sections and subsequent confocal laser microscopy analysis have been applied for in situ cellular analysis of a variety of plant cells, tissues and organs with different characteristics, e.g. hardness, heterogeneity, cell accessibility, tissue compactness, etc.; the results demonstrated the versatility and feasibility of the approach for different plant samples, and revealed defined DNA methylation nuclear patterns associated with differentiation and proliferation events of various plant cell types and developmental programs. Quantification of 5mdC immunofluorescence intensity by image analysis software also permitted to estimate differences in global DNA methylation levels among different cells types of the same organ during development.