Genetic Hybridization barriers

The question of what is a species, though discussed since decades, has still not been fully answered. However, beyond controversy is the fact that in order for a new species to arise reproductive isolation must occur. Two different broad categories of reproductive isolation barriers have been classified acting either prezygotically or postzygotically. Whereas prezygotic barriers prevent fertilization to occur, postzygotic barriers act after fertilization and include hybrid inviability and sterility and are strongly correlated with the genetic distance between taxa. In the proposed research I aim investigating postzygotic hybridizations barriers that cause endosperm breakdown leading to hybrid seed abortion. The endosperm is a terminal nutritive tissue supporting embryo growth and it is essential for viable seed formation; therefore, malfunction of endosperm development will result in embryo arrest and seed abortion. My initial experiments revealed that there are strong postzygotic barriers in two different species pairs of the Brassica family: Capsella (C. rubella and C. grandiflora) and Arabidopsis (A. lyrata and A. arenosa), establishing these species pairs as model systems to investigate the basis for postzygotic hybridization barriers in plants. Specifically, the main aims of this proposal are to (i) morphologically characterize hybrid seed failure in Capsella rubella and C. grandiflora and Arabidopsis lyrata and A. arenosa, (ii)identify the underlying genetic basis of postzygotic hybridization barriers in Capsella, (iii) characterize the molecular mechanisms underlying hybrid seed failure in Capsella. I anticipate that the results of this research will strongly advance our understanding of the underlying molecular mechanisms of reproductive isolation and plant speciation and will be of interest to a broad scientific community.

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