Differential methylation patterns in apomictic vs sexual genotypes of the diplosporous grass Eragrostis curvula

Methylation is an epigenetic mechanism where a methyl group take place over the C5 of cytosine or C6 of adenine repressing or de-repressing genes depending on the context, position (coding or non-coding) and species. Eragrostis curvula is a forage grass that reproduces by apomixis. Increases of the frequency of sexual pistils in facultative genotypes of this grass has been associated to epigenetic changes triggered by different biotic and abiotic stresses. The aim of the present study was to associate differences in the reproductive mode with specific methylated regions and genes contrasting full apomictic, facultative and sexual genotypes using the methylation sensitive technique MCSeEd. The distribution of the differentially methylated positions over the genes shows a peak around the start and stop codon boundaries, hence regulating gene expression mainly through the incorporation of methyl groups on these positions. The main pathways being regulated were ubiquitin and auxins. The methylation pathway itself was also found to be self-regulated since ROS1 and ROS4, the main demethylating genes were found differentially methylated among the different genotypes. Even more, this work allowed us to detect genes regulated by methylation that were previously found differentially expressed in the comparisons between apomictic and sexual genotypes.