Plastid protein transport mechanisms and organelle biogenesis

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Plants form the pillars of the Earth's life-supporting activities like photosynthesis, starch and oil production, and respiration. These activities are governed by dynamic cellular processes, requiring interaction of countless molecular participants and take place in specialized spaces inside plant cells. One such space is the plastid, an organelle designed for capturing and producing energy for plants. Plastids must also adjust their activities during development and when adapting to the ever-changing environment. Such adjustments are accompanied by dramatic shifts to the diversity of proteins being transported into plastids. It is thus important for plastids to maintain a responsive and efficient protein transport process that can address all situations. Recent findings indicate that the co-chaperone Tic40, a dynamic component of the plastid protein transport machinery, may be involved in the adjusting mechanisms and that Tic40's role(s) may be influenced or modulated by the activities of organellar rhomboid proteases. This proposal thus outlines projects aimed at elucidating the role of Tic40 and rhomboid proteases in plastid protein transport. Since rhomboid proteases belong to a group of highly conserved proteins involved in signaling and development, the long-term goals will be to define the Tic40-rhomboid protease link and the meaning of this relationship to plastid protein delivery, organelle biogenesis, cell structure, and development. For the related short-term goals, we will employ established and modern proteomic approaches to characterize specifically : 1) Tic40's structure, its capabilities and its rhomboid cleavage site(s); 2) The functional features of plant organellar rhomboid proteases such as location, targeting, and enzymatic activities; and 3) The functional relationship between Tic40's importation and plastid rhomboid proteases. The work will also contribute to the development of techniques and strategies for functional proteomics, whole cell research, and commercial applications. Equally important, students going through the proposed 5-year NSERC program will receive intensive training in discoveries research applicable to their careers (for at least 3 Ph.D., 6 M.Sc., and 10 B.Sc.).