Poster: Hormones

Abs # 632: Characterization of AtMYB50 expression in relation to cytokinin

Presenter:	McCasland, Michael R., mccaslan@email.unc.edu
Authors	McCasland, Michael R. (A)   Rashotte, Aaron M. (A)   Kieber, Joseph J. (A)
Affiliations:	(A): University of North Carolina at Chapel HIll

Cytokinins are hormones that have been shown to affect many vital processes in plants, including the cell cycle and plant development. We conducted genome-wide analysis of Arabidopsis seedlings treated with cytokinin at multiple time points using Affymetrix ~8,300 element Arabidopsis GeneChips experiments. One of genes we identified in this analysis was the R2-R3 MYB transcription factor AtMYB50, that showed induction at multiple time points. The focus of this research project is to identify the possible role MYB50 has in cytokinin signaling and plant development, using two approaches. In the first approach, we have identified a T-DNA knockout for MYB50 and are characterizing its phenotype in the presence and absence of cytokinin. We conducted shoot initiation assays to assess the sensitivity of myb50 to cytokinin and auxin concentrations. We found that myb50 displays reduced sensitivity to cytokinin, suggesting a role of the gene in cytokinin responsiveness. Physiological measurements of myb50 mutant plants have revealed several phenotypic alterations including smaller leaves, delayed bolting, abnormal venation, and a pale-green color. MYB50 mutants contain about half the amount of chlorophyll as compared to wildtype plants. Our second approach is to analyze the transcriptional regulation of MYB50 using an overexpression construct and promoter GUS fusion. These constructs in conjunction with cytokinin dose response assays will allow us to assess temporal and spatial regulation of this gene in relation to cytokinin signaling.