Functional and evolutionary analysis of chloroplast metabolite transporters in the C4 plant maize

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Due to a biochemical inorganic carbon-concentrating mechanism, C4-photosynthesis is advantageous to C3-photosynthesis under conditions where photosynthesis becomes carbon dioxide-limited, such as high temperature, drought, and saline conditions. The enzymatic steps involved in the C4 inorganic carbon pump have been identified, and the enzymes and genes and their regulation have been characterized in great detail. However, most of the metabolite transporters involved in this biochemical inorganic carbon pump, in particular those of the chloroplast envelope membrane, are unknown. The hypothesis to be tested in this award is that plastid envelope membrane transporters involved in the C4-photosynthetic pathway can be identified based on their abundance in C4 chloroplast envelope membranes and their temporal, developmental, and spatial expression pattern. The investigator proposes to use comparative and quantitative proteomics and transcript profiling to identify candidate genes for these transporters, and reconstitution of purified recombinant transporter proteins into liposomes to functionally characterize the corresponding proteins.These studies are expected to significantly increase understanding of the fundamental physiological process of C4 photosynthesis. The project will lead to in-depth understanding of how a complex biochemical pathway is connected and coordinated by transport proteins in the plastid envelope membrane.Broader impacts resulting from the proposed activityUndergraduate and graduate students will participate in the project. They will receive cross disciplinary training so they can think beyond their individual field of expertise towards an integrative view of plant biology. Research activities will be integrated into teaching by training junior scientists in the handling of membrane transporters, a field currently not represented at this institution. Graduate students and senior researchers will be involved in undergraduate teaching in the field of plant membrane transport. Plant material generated in this project will be used to introduce K-12 teachers into genetic engineering of plants and to train K-12 teachers in modern molecular techniques in summer courses. A public project database will provide the plant research community with information on maize chloroplast envelope membrane proteome.