Is apomictic seed development influenced/controlled by epigenetic factors?

Abstract

Several lines of evidence suggest that transitions during reproduction and early seeddevelopment are epigenetically regulated by dynamic changes in chromatin state. Moreover,deregulation of key developmental steps in sexual processes are thought to causeapomixis, and supporters of this hypothesis justify it based on the coexistence of sex andapomixis in the same individual. For example, some authors found that DNA methylationderegulation in reproductive cells induce apomeiosis-like phenotypes suggesting thatspecialization of a DNA methylation pathway acts upon germline or germline associatedcells. With this aim in mind, we decided to investigate DNA methylation differencesbetween apomictic and sexual genotypes of two species, Paspalum rufum and Eragrostis curvula. High-throughput DNA sequencing technologies have enabled the measurementof cytosine methylation on a genome-wide scale. Many technologies have been developedover the past decade to measure DNA methylation. MCSeEd (Methylation ContentSensitive Enzyme ddRAD) is a reduced-representation, reference-free, cost-effective approachfor characterizing whole genome methylation patterns across different methylationcontexts (CG, CHG, CHH, 6 mA) that we have recently developed at the University ofPerugia. DNA from triplicate panicle samples of contrasting reproductive mode materialswere digested with enzymes sensitive to DNA methylation (AciI, PstI, EcoT22I, and DpnII,for the CG, CHG, CHH and 6 mA contexts, respectively), and libraries were generated andsequenced in Illumina platform. Several differentially methylated genomic regions werefound and associated to annotated genes that were classified with the BLAST2GO software.Several genes already linked to apomixis (i.e., SERK, APOSTART) were found to be bothdifferentially methylated and differentially expressed.