Arabidopsis Seed Coats as a Model System for Molecular Genetic Analysis of Plant Cell Wall Biosynthesis and Modification

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Plant cell walls are typically composed of the polysaccharides cellulose and hemicellulose, embedded in a hydrophilic, carbohydrate gel called pectin. These cell wall components interact with one another to create an environmental barrier that meets the needs of the cell during growth and differentiation. In addition the wall provides an extracellular matrix through which adjacent cells are connected to each other. Consequently, information concerning plant cell wall structure and how it can be modified as cells develop and adapt to a changing environment is valuable and has many applications in agriculture and forestry. We study a specialized cell type of the Arabidopsis thaliana seed coat that makes large quantities of cell wall polysaccharides. Mutants unable to synthesize these polysaccharides correctly are identified and used to isolate the corresponding genes encoding proteins needed for cell wall biosynthesis and modification. These genes and their protein products can then be used as tools to understand cell wall structure and function. Using this approach we propose to study how: 1. polysaccharides can be modified to make the cell wall more or less cohesive, 2. cells target proteins to the cell wall, 3. specific cell-wall carbohydrates are required for cell wall properties, 4. Cell wall proteins are degraded, and 5. the cell wall is structured at the molecular level. We believe that answers to these questions will help us to understand and manipulate physical properties of the cell wall for the purposes of influencing plant growth and development.