Plant post-embryonic development takes place in the meristems, zones of actively dividing cells. Meristems contain populations of stem cells that self-renew and produce daughter cells that differentiate giving rise to different organ structures. Using mainly molecular genetic approaches plant stem cell and meristem maintenance research has identified the major players in the underlying developmental pathways, encoding a variety of proteins involved is signal transduction. However, their regulation at the protein level is largely unknown and requires the analysis of in vivo post translational modification (PTM). Knowing and understanding the PTM of the proteins involved will provide a higher level of understanding on the gene/protein networks that are at the heart of growth and development. Recent advances in selective phospho-peptide purification and mass spectrometry now allow a proteome wide analysis of in vivo protein phosphorylation 1. Here, we propose to combine quantitative phospho-proteomics with cell type specific responses. Specifically, we will quantitate in selected cell types the phosphorylation states of proteins involved in stem cell and meristem maintenance in the Arabidopsis root, which can also identify downstream targets. Together with targeted and functional PTM analysis of the known factors involved this will provide unprecedented detail on proteome regulation during stem cell and meristem maintenance. The establishment of a protein phosphorylation database will provide the community with an extensive resource useful for plant signal transduction research as a whole.  Furthermore, the knowledge generated can be applied towards plant architecture and developing crops that can grow under adverse environmental conditions.

Keywords: Stem Cells, Quantitative Proteomics, Phosphorylation, Signal Transduction, Arabidopsis.