Hybrid incompatibility caused by an epiallele

Todd Blevins, Jing Wang, Frédéric Pontvianne , Craig Pikaard
Publication Date
April 2017
Website
View more

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 Arabidopsis thaliana accession Cvi-0, one of the two copies of a duplicated histidine biosynthesis gene, HISN6A, is mutated, making HISN6B essential. In contrast, in accession Col-0, HISN6A is essential because HISN6B is not expressed. Owing to these differences, Cvi-0 × Col-0 hybrid progeny that are homozygous for both Cvi-0 HISN6A and Col-0 HISN6B do not survive. We show that HISN6B of Col-0 is not a defective pseudogene, but a stably silenced epiallele. Mutating HISTONE DEACETYLASE 6 (HDA6), or the cytosine methyltransferase genes MET1 or CMT3, erases HISN6B's silent locus identity, reanimating the gene to circumvent hisn6a lethality and hybrid incompatibility. These results show that HISN6-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.

Citation

Todd Blevins, Jing Wang, Frédéric Pontvianne and Craig S. Pikaard (2017). Hybrid incompatibility caused by an epiallele. Proc. Natl. Acad. Sci. 114:3702-3707

            **This paper was highlighted in a perspectives article:  Bente, H. and O. Mittelsten-Scheid (2017). Epigenetic contribution to diversification. Proc.  Natl. Acad. Sci. 114:3558-3560