DNA Methylation Events Specific of Apomictic Lineages in the Boechera Genus

Apomixis (asexual seed formation) could reproductively-stabilize hybrid vigor, but despite many efforts it has not been successfully transferred to crops. Genes controlling apomixis in wild species are still under investigation, and the existence of an epigenetic model has been postulated. Some studies have demonstrated that during sexual reproduction a genome-wide decrease of DNA methylation takes place and is compensated by de novo methylation. In the present study, we investigated DNA methylation in pre-meiotic flower buds of four diploid sexual species, B. retrofracta (Utah), B. stricta (Utah), and eastern (Cody, Wyoming) and western (Imnaha, Oregon) sexual genotypes of B. microphylla, and four diploid apomictic Boechera species or species hybrids, B. lignifera (Wyoming), B. retrofracta x stricta (Colorado), B. retrofracta x exilis (Utah) and B. microphylla (Utah). Cytological analyses revealed diplospory in the apomictic genotypes except for B. microphylla, which was aposporous. Our aim was to identify epigenetic differences in flower buds between sexual and apomictic species by analyzing DNA methylation. A total of 1203 clear and reproducible bands were amplified. The extent of DNA methylation ranged from 70.55% in apomictic B. retrofracta to 83.54% in B. yellowstonensis. In particular DNA methylation averaged 77.53% in apomictic species and 81.12% in sexual species. We then checked the entire collection for polymorphisms and found 10 that were absent in all sexual species and present in all apomictic species or vice versa. Amplicons were sequenced. The results will be presented and discussed.