Arabidopsis 2010: Functional Genomics of Arabidopsis Starch Granule Metabolism

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The molecular and physiological functions of the Arabidopsis starch metabolism gene network will be determined. The glucose polymers that make up starch, despite their simple chemical structures, display a complex molecular architecture that is essential for starch function. The Arabidopsis genome sequence allows identification of all the genes involved in starch biosynthesis or mobilization, and determination of the function of each gene product individually and within the metabolic network. This aspect of metabolism is a distinguishing feature of all plant life, by which the metabolic gains of photosynthesis are stored and used later when light is not available as the energy source. Understanding starch assembly and disassembly as a comprehensive chemical system, therefore, is required for a complete functional description of how the sequence information in the Arabidopsis genome is translated into the plant life form. In this project, "determination of function" implies that the role of each protein in the assembly or disassembly of starch polymers will be understood at the level of specific molecular interactions. The project focuses on 28 genes that are likely to be involved in starch metabolism after the production of the glucosyl unit donor. The gene set includes starch synthases, branching enzymes, debranching enzymes, a-amylases, b-amylases, disproportionating enzymes, and starch phosphorylases. In each instance the genome sequence predicts multiple isoforms. The two organizing hypotheses of the project are that most isoforms have specific, non-overlapping roles in creating or dismantling the molecular architecture of starch, and that many components of the network act via direct functional interactions rather than in a series of independent enzymatic steps. Results will be shared through scientific publication, regular web postings (www.starchmetnet.com), and via scientific conferences. Resources that will be developed and made available to the scientific community include mutant lines, isoform-specific antibodies, and purified recombinant enzymes. The project will have broader impacts in the training of scientists at all levels in areas such as mRNA profiling, biochemistry, and bioinformatics. The project will strive to involve members of under-represented groups in this activity at the undergraduate level, through established partnerships with universities that traditionally serve such students. Starch provides the majority of calories in the human diet, and is also a renewable resource for energy production and industrial raw materials. Comprehensive understanding of this energy storage system will provide a greater ability to exploit renewable plant resources to meet the continually increasing demands of our changing society and environment.