Epigenetic contributions to hybrid vigor in apomictic offspring (Syngenta)

PIs: Bernhard Schmid, Ueli Grossniklaus
PhD: Anja Herrmann

In the 1930es it was proposed that fixation of hybrid vigor through apomixis would have a tremendous impact on agriculture. Apomixis, the asexual propagation through seeds, completely preserves the genotype of the mother, resulting in clonal offspring (1). Unfortunately, progress in apomixis research has been slow and the transfer of apomixis to crops has not been achieved so far (2). However, the clonal fixation of heterosis will only be possible if there is no major epigenetic contribution to the hybrid phenotype. In fact, it was never tested whether phenotypes are faithfully conserved during apomictic reproduction. This, it is not clear whether heterosis could indeed be fixed through apomixis. In mammals, the lack of epigenetic reprogramming during reproduction is the major cause for developmental abnormalities in clones derived from somatic nuclear transfer (3). Similarly, the absence of such reprogramming events during apomixis could also results in phenotypic variability. Furthermore, epigenetic changes occur upon hybridization (4) and if these are inherited to some extent, they may lead to variation in the offspring, even if clonal in nature. It is currently unclear to what extent epigenetic information is inherited from one generation to the next in plants. However, a better understanding of transgenerational inheritance in plants is central to plant development, ecology, and agriculture.
In this project, we propose to compare phenotypic and epigenetic changes that occur in hybrid progeny that was either produced sexually or clonally. Sexually produced seeds undergo normal reprogramming events during gametogenesis and early seed development (5-7), while asexually produced, clonal seeds short-circuit gametogenesis (1) and thus fail to be reprogrammed. A comparison of genetically identical populations, created sexually or clonally, will allow us to investigate the importance of epigenetic reprogramming. By combining ecological with genome-wide molecular approaches we will be able to determine not only the nature of inherited epigenetic information but also its relevance for phenotypic variation and its interaction with the environment.