The shift to self-pollination (or selfing) is one of the most prevalent evolutionary transitions in flowering plants. Charles Darwin (1876) studied selfing using extensive ecological experiments. He proposed the reproductive assurance model to explain the prevalence of self-pollination in plants, suggesting that selfing can be evolutionarily advantageous when pollinators or mates are scarce, despite the negative consequences typically associated with selfing (inbreeding depression).
Within the Brassicaceae, the family that contains the vast majority of the green vegetables we consume, a common mechanism for maintaining outcrossing is self-incompatibility (SI). This system functions by recognition and rejection of self-pollen through male and female specificity components, encoded at the S-locus. If mutations that cause loss of function occur at one or both of these components, it can lead to the transition to selfing. Due to the nature of these components, particularly the fact the locus is under long-term balancing selection, typical methods employed to resolved key genomic information, including recent advances in next generation sequencing (NGS) technologies have largely failed to deal with areas of complex architecture. As part of our recent work, we have been developing sequencing and bioinformatic methods to overcome these issues. See: http://www.g3journal.org/content/8/4/1327
Arabidopsis lyrata is an ecologically relevant, non-model organism that lends itself well to the study of the transition from outcrossing to selfing. In North America, its current population structure has been clearly influenced by post-glacial colonisation after the retreat of the last glacial maxima, and so it presents an excellent opportunity with which to study recent transitions to selfing (less than 20,000 years). Particularly interesting in this system, is it appears that there have been multiple incidences of this transition, and that these switches have likely involved different mechanisms (mutations in different components at the S-locus). To assess this, we will use a combination of bacterial artificial chromosome (BAC) technology, and single-molecule, real-time sequencing (SMRT) to sequence entire S-locus regions from both selfing and outcrossing individuals from multiple populations.
The project will introduce the student to the broader areas of population genetics, evolutionary ecology, and bioinformatics. The research activities will be undertaken at the School of Chemistry and Biosciences, University of Bradford. The research sits in the context of a highly active research environment at the University of Bradford.