DNA hypomethylation bypasses the interploidy hybridization barrier in Arabidopsis. Arabidopsis thaliana

Plants of different ploidy levels are separated by a strong postzygotic hybridization barrier that is established in the endosperm. Deregulated parent-of-origin specific genes are causal for the response to interploidy hybridizations, revealing an epigenetic basis of this phenomenon. In this study we present evidence that paternal hypomethylation can bypass the interploidy hybridization barrier by alleviating the requirement of the epigenetic Polycomb Repressive Complex 2 (PRC2) in the endosperm. Bypass of the barrier is mediated by suppressed expression of imprinted genes. We show that hypomethylated pollen causes redistribution of CHG methylation to PRC2 target genes, revealing that different epigenetic modifications can functionally substitute for each other. Our work presents a method and the underlying mechanism for the generation of viable triploids, providing an impressive example for the potential of epigenome manipulations for plant breeding. Overall design: Examination of DNA methylation in Arabidopsis endosperm, embryo, and pollen, and gene expresion in seeds