Epigenetic Marks Associated with Apospory Expressivity during Floral Development of Diploid Paspalum Rufum Cytotype

PODIO, MARICEL; ORTIZ, JUAN PABLO A; DELGADO, LUCIANA; MARCONI, GIANPIERO; ALBERTINI, EMIDIO; SOLIMAN, MARIANO; DI MARSICO, MARCO

Workshop; Proceedings of the 7th Series of Seminars on Advances in Apomixis Research; 2020

Apomixis is an asexual reproduction pathway through seeds that generates clonalprogenies. It was proposed to derive from the deregulation of genes involved in sexualityby genetic/epigenetic mechanisms. Paspalum rufum grass forms a multiploid complexwith self-sterile sexual diploid and self-fertile apomictic tetraploid cytotypes but somediploid genotypes produce aposporous embryo sacs and clonal seeds. Moreover, variationin apospory expressivity was detected within experimentally obtained diploid families.Here we compare the relative methylation levels between floral libraries of full-sib diploidP. rufum genotypes exhibiting low and high apospory expressivity. Methylation ContentSensitive Enzyme ddRAD (or MCSeEd) strategy, without reference genome, was appliedin two developmental stages, pre-meiosis/meiosis and post-meiosis and at three differentcontexts (CG, CHG and CHH). Heatmaps and principal component analysis of the relativemethylation changes clearly discriminated between reproductive behavior at both developmentalstages and for almost all the methylation contexts. P. notatum floral transcriptomewas queried by differential methylated contigs (DMCs), revealing 14% of homology, almosthalf of which were differentially expressed between apomictic and sexual samplesof P. notatum. BLAST searches over public databases allowed the identifications of DMCshomologous to genes involved in flower growth, development and also to many genesand genomic regions previously associated to apomictic development. In silico mappingon Setaria italica genome showed a high proportion of DMCs aligning on genomic regionspreviously associated with apomixis. This work provides evidence of the presence of differentialmethylation levels associated with variation in apospory expressivity in a diploidgrass species.