Functional genomics of intracellular membrane trafficking in Arabidopsis thaliana

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The intracellular membrane trafficking pathways connect the organelles of the eukaryotic endomembrane system.  In plants, these pathways play important roles in the biosynthesis and accumulation of proteins, lipids and polysaccharides that literally feed, clothe and house the world. Beyond this, they have also been recognized as central to wider aspects of plant cell development and cellular adaptation to environmental stresses.       The overall goal of my research is to understand how plant genes control intracellular membrane trafficking as cell morphology changes during plant development and in cellular responses to environmental stresses. Small Rab GTPases are key membrane trafficking regulators. In Arabidopsis, 57 putative Rabs are identified and clarified into 18 structural subclasses, yet only few have been functionally studied. Following our recent characterization of the Rab-D2 and Rab-E1 subclasses, we propose to investigate the function of the Rab-A1 subclass in membrane trafficking, cell signaling, cell morphogenesis, and stress adapation. We will test the roles of Rab-A1s in membrane trafficking using a dominant negative mutant approach combined with in vivo imaging of fluorescent markers co-expressed in plant cells. We will also determine the tissue specificity and subcellular localization of each Rab-A1 members, and generate knockout mutants for loss-of-function studies. A split ubiquitin-based cDNA library will be constructed and screened for Rab-A1 and Rab-E1 interacters in order to dissect Rab-mediated signaling pathways. In addition, we also plan on characterizing and cloning three novel membrane trafficking mutants identified in a genetic screen based on the intracellular accumulation of a secretory GFP in an EMS-mutagenized population.       Our work will 1) give molecular and cellular details on how plants, as multicellular organisms are developed, 2) provide fresh insight into how plants deal with prevailing environment, and 3) shed light on how valuable proteins, lipids, and polysaccharides are accumulated in the plant endomembrane system. This knowledge can be used to develop technologies of benefit to agriculture and biotechnology.