Hybrid incompatibility caused by an epiallele.

Hybrid incompatibility resulting from deleterious gene combinations is thought to be an important step toward reproductive isolation and speciation. Here, we demonstrate involvement of a silent epiallele in hybrid incompatibility. In accession Cvi-0, one of the two copies of a duplicated histidine biosynthesis gene, , is mutated, making essential. In contrast, in accession Col-0, is essential because is not expressed. Owing to these differences, Cvi-0 × Col-0 hybrid progeny that are homozygous for both Cvi-0 and Col-0 do not survive. We show that of Col-0 is not a defective pseudogene, but a stably silenced epiallele. Mutating (), or the cytosine methyltransferase genes or erases silent locus identity, reanimating the gene to circumvent lethality and hybrid incompatibility. These results show that -dependent hybrid lethality is a revertible epigenetic phenomenon and provide additional evidence that epigenetic variation has the potential to limit gene flow between diverging populations of a species.