Transcriptional Regulation of the Cytokinin Signaling Network

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The plant hormone cytokinin regulates many agronomically important traits, including grain yield, biomass, shoot and root architecture, senescence, and disease resistance. How a hormone regulates such a diverse array of traits remains a central question in biology. The goal of this project is to uncover how cytokinins regulate plant growth and development, with a particular focus on differences in regulation that occur in the shoot and root. Investigators use interdisciplinary methods to experimentally quantify and mathematically model gene regulatory networks underlying cytokinin signaling. The understanding gained by their work will facilitate predictions for how perturbation of cytokinin function alters plant development. Outcomes of this work will ultimately enable precise manipulation of plants to optimize performance in various agricultural settings. Broader impacts of the project will provide interdisciplinary training opportunities for undergraduate students, graduate students and postdoctoral fellows. In addition, through local partnerships, programs will be developed that aim to encourage education and science awareness among elementary and middle school students through participatory activities.Cytokinin modulates plant growth and development in a potentially tissue specific manner, stimulating cell proliferation in the shoot but inhibiting it in the root. Focusing on transcriptional networks initiated by type-B ARR transcription factors, which act at the top of a transcriptional cascade to mediate the cytokinin response, investigators use an integrated set of experimental methods to dissect the mechanisms by which cytokinin regulation occurs. A dynamic Bayesian network approach will be used to mathematically infer gene regulatory networks that mediate the cytokinin response in roots and shoots and identify unique regulatory aspects that correlate with the tissue specific effects of cytokinin. Using genetic approaches the transcriptional networks will be perturbed to determine the role that various mechanisms play in mediating signaling output, with perturbations focused on key elements that regulate cytokinin signaling sensitivity and downstream transcription factors associated with the signaling network. RNA-Seq will be used to globally characterize gene expression and ChIP-Seq to identify targets of the transcription factors. By iteratively using network modeling to guide experimental investigations, which in turn further inform the model, this project will result in a systems level understanding of cytokinin signaling and the mechanism by which various transcriptional factors enable cytokinin to mediate development associated phenotypes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.