Plant speciation mechanisms
Polyploidization is a widespread phenomenon among plants and is considered a major speciation mechanism. Polyploids have a high degree of immediate post-zygotic reproductive isolation from their progenitors, as backcrossing to either parent will produce mainly nonviable progeny. This reproductive barrier is called triploid block and is caused by malfunction of the endosperm. Nevertheless, the main route to polyploid formation is via unreduced gametes and unstable triploid progeny, suggesting that there are ways to overcome the triploid block. Until recently, neither the formation of unreduced gametes nor the triploid block were understood mechanistically. We aim at elucidating the mechanisms contributing to polyploid formation and their impact on plant speciation.
We are furthermore interested in testing whether similar mechanisms underpinning polyploidy-mediated hybridization barriers also account for interspecies hybridization barriers. To test this hypothesis we investigate interspecies hybridizations and test the effect on endosperm development with the ultimate goal to identify the molecular mechanisms causing endosperm failure after interspecies hybridizations. Our current model organisms in this project are Arabidopsis lyrata, Capsella and Primula.
Kradolfer D, Wolff P, Jiang H, Siretskiy A, Köhler C. (2013) An imprinted gene underlies postzygotic reproductive isolation in Arabidopsis thaliana. Dev Cell. 26: 525-35. (Medline)
Hehenberger E, Kradolfer D, Köhler C (2012) Endosperm cellularization defines an important developmental transition for embryo development. Development, 139: 2031-203 (Medline )
Brownfield, L., Köhler, C. (2010) Unreduced gamete formation in plants: mechanisms and prospects. J Exp Bot. 62:1659-1668 (Medline)
Köhler C, Kradolfer D. (2011) Epigenetic mechanisms in the endosperm and their consequences for the evolution of flowering plants. Biochim Biophys Acta. 1809: 438-43. (Medline )
Erilova, E., Brownfield, L., Exner, V., Rosa, M., Twell, D., Mittelsten Scheid, O., Hennig, L., Köhler, C. (2009) Imprinting of the Polycomb Group Gene MEDEA Serves as a Ploidy Sensor in Arabidopsis. PLoS Genet. 5:e1000663. (Medline)