Cytokinins are plant hormones that regulate many agronomically important traits, including plant architecture, biomass, senescence, disease resistance, drought resistance, and grain yield. A better understanding of cytokinin signaling will enable optimization of crops to improve their performance in various agricultural settings. The goal of this project is to uncover how the cytokinin hormone signal regulates gene expression in plants, and thereby controls plant growth and development. State-of-the art mass spectrometry approaches will be used to identify regulatory modifications on proteins and how these modifications change during the cytokinin response. The proposed research will provide excellent training opportunities for graduate students and postdoctoral fellows. In addition, through a local partnership, the project will establish a summer program aimed at developing education and science awareness through participatory activities that integrate science with art.
The current paradigm for cytokinin signaling involves a two-component His-Asp phosphorelay similar to that found in prokaryotes. In this model, phosphorylation of the type-B response regulators (RRs) on a conserved Asp residue regulates their transcriptional activity, thereby controlling the transcriptional response to cytokinin. The goal of this project is to test the hypothesis that Ser/Thr phosphorylation of the type-B RRs also serves to regulate their activity. The prediction is that rapid cytokinin-dependent changes in Ser/Thr phosphorylation will occur, and that these will activate the type-B response regulators independently of Asp phosphorylation. Phosphoproteomic approaches will be employed to identify in vivo phosphorylation sites of the type-B response regulators and to characterize their phosphorylation dynamics in response to cytokinin. The regulatory significance of Ser/Thr phosphorylation sites will be tested by mutating the residues to phosphomimic (Glu) and non-phosphorylatable (Ala) versions of the residues, and their activity examined in a reporter system. Uncovering a Ser/Thr regulatory mechanism for the type-B RRs will fundamentally alter our model as to how cytokinin signal transduction occurs in plants, and also yield novel information on how the evolutionarily ancient two-component signaling pathway has been adapted to the needs of a eukaryote.
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.
