The effect of cytokinin on the chromatin landscape of arabidopsis

Cytokinin, a N⁶ substituted adenine, is a phytohormone with pleiotropic effects, including shoot activation, root inhibition, delay of leaf senescence, and tissue regeneration. Cytokinin is perceived by a histidine kinase and ultimately results in the activation of a response regulator that controls transcription of cytokinin-dependent genes. How a single signaling molecule is involved in numerous distinct developmental processes and how it integrates with other signaling pathways remain fundamental questions in plant biology. Formaldehyde-assisted isolation of regulatory elements (FAIRE) is a technique used to isolate nucleosome-depleted regions of the genome. Nucleosome depletion is characteristic of open chromatin and such sites often contain regulatory elements that control the expression of nearby genes. In this thesis, I demonstrate that FAIRE can be used to isolate cytokinin-induced open chromatin in Arabidopsis seedlings. After sequencing and peak calling, the called peaks identified in the cytokinin treated samples were found to be enriched for the motif TAGATT, which contains the known type-B RR binding motif AGAT. These peaks were additionally enriched for binding motifs of other transcription factors, suggesting that the cytokinin response can be moderated by other signals and likely act differently in different cellular contexts. Thus, the work described in this thesis has helped refine the transcriptional model of the cytokinin response in plants and provides the foundation and tools to investigate and dissect the dynamics of the cytokinin response and how it integrates with other signaling pathways.Master of Scienc