Most of the energy on earth comes ultimately from the sun, and plant chloroplasts are critical cellular organelles because they allow plants to capture solar energy and convert this energy to sugars through the process of photosynthesis. Most of the proteins that perform these important tasks in chloroplasts are synthesized in the cytosol of the plant cell, are taken up into the chloroplast stromal compartment, and then have to be specifically targeted to one of five additional chloroplast compartments by translocases, enzymes that transport proteins across or into membrane bilayers. A central unanswered question regarding this intricate protein localization network is: What system(s) are responsible for targeting and integration of the translocase proteins? A Sec translocase was recently discovered that is localized to the inner envelope of the chloroplast. Mutations that disrupt this translocase result in death, suggesting a critically important role in chloroplast function. Preliminary results suggest that this system, designated Sec2, is the master translocase, responsible for the placement of all other translocase proteins into their correct chloroplast compartment. Sec2 will be further characterized through this project. Specific aims include identification of all the components of the system, characterization of the proteins targeted and translocated/integrated by Sec2, and the establishment of an assay system to investigate the requirements for energy, accessory factors, and targeting information for this translocase system. Successful completion of the research will result in increased insight into the pivotal role that this novel translocase may play in the biogenesis of the chloroplast.
BROADER IMPACTS This project will provide cross-training opportunities in genetics and biochemistry for young scientists at the undergraduate, graduate, and postgraduate level. Project personnel will also learn valuable teaching and mentoring skills by supervising undergraduate students in hands-on research experiences. The plant lines that will be generated in this project will be valuable research tools and will be distributed to other laboratories interested in chloroplasts. Finally, because many vital metabolic and biosynthetic functions, including photosynthesis and synthesis of fatty acids, essential amino acids and vitamins, are centered in chloroplasts, the work may have practical applications as people seek to modify, optimize, or otherwise control these capacities.
