Emily Gleason
Graduate Student
Evolution of Epigenetic Factors and their Roles in Flowering Time in Aquilegia
Precise control over the transition to flowering is essential for a plant’s reproductive success. Thus, flowering time is tightly regulated by both internal signaling pathways (the autonomous and gibberellin pathways) and environmental cues such as day length, ambient temperature, and over-wintering. Many temperate plant species require a period of cold, called vernalization, before they are able to flower. The genetic basis of the vernalization response has been well studied in Arabidopsis as well as the monocots, wheat and barley. However there seems to be little conservation between the loci involved in vernalization in these systems and those that function analogously in Arabidopsis. Thus it is thought that the vernalization response evolved independently in these two systems. Despite this fact, epigenetic mechanisms (specifically regulation by a deeply conserved group of proteins known as the Polycomb group) have been implicated in both cases, raising questions as to whether this kind of regulation may be a common theme in vernalization response pathways. In order to explore this possibility, I hope to determine the genetic basis of vernalization response in the emerging model system Aquilegia. This early diverging eudicot arose before the radiation of the core eudicot clade and represents what is likely to be an independent derivation of vernalization response relative to Arabidopsis and the grasses, thereby providing a critical third data point.
My thesis will lay the foundation for studies of epigenetic regulation in general and vernalization response in particular by globally annotating all of the major epigenetic factors in the genome of the emerging model system Aquilegia. Once this is completed, I plan to focus specifically on the homologs of the Polycomb Repressive Complex 2 (PRC2), examining their general expression patterns, including parent-of-origin effects. This will be complemented by targeted gene knockdowns of particular loci of interest. Lastly, I will attempt identify genes that play a role in the vernalization response in Aquilegia using high-throughput sequencing to characterize the mRNA transcriptome in the shoot apex of Aquilegia vulgaris before, during, and after vernalization. This approach will hopefully identify new candidates for the repression or induction of flowering, which will in turn be examined using chromatin immunoprecipitation to determine whether they are the targets of epigenetic remodeling during vernalization.