Signalling and cell walls

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My research program focuses on two aspects of plant biology: how plants use specific signaling modules to detect and respond to environmental and developmental cues, how plants build their complex polysaccharide cell walls, and how these two phenomena are connected. The cellular mechanisms by which plants successfully respond to environmental challenges are controlled by signal switching mechanisms such as protein phosphorylation/de-phosphorylation cycles, catalyzed by protein kinases. The mitogen-activated protein kinase (MAPK) family of enzymes plays a central role in these switching systems, but we know little about the biological functions of the Group D sub-family of MAPKs. We will use a combination of genetics, cell biology, genomics and biochemistry to identify the full range of cellular processes that Group D MPKs are controlling in Arabidopsis. The down-regulation of MPK signaling activity is dependent on removal of phosphate groups, catalyzed by protein phosphatases. We will dissect the kinase-phosphatase regulatory relationship for Arabidopsis MPK6, a MAPK that can be de-activated by at least four different phosphatases. Plant cells have the ability to cloak themselves in a rigid polysaccharide envelope, the cell wall. Many questions remain about the identity of the enzymes involved, and how the biosynthetic process is organized. We will exploit the ability of in vitro cultured wall-less plant cells (protoplast) to rapidly regenerate a new cell wall, and carry out a global profiling analysis (gene expression, protein accumulation, protein modification, wall immunochemistry) of protoplasts as they make the transition to a fully constructed new wall. Since protoplasts can be produced from a range of genetic backgrounds, including mutants, this protoplast regeneration platform will ultimately enable us to pinpoint what stage in cell wall formation is being affected by loss of function in uncharacterized genes previously identified as being associated genetically with cell wall formation.