Expression & Function of the Tomato B-Subunit During Growth and Development

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9408826 DellaPenna A long-term goal of this research is understanding the functional significance of developmentally regulated, polyuronide modifications in plants. As part of prior NSF funding, the Beta- subunit of polygalacturonase (PG1) was purified; cDNAs encoding the protein were isolated and characterized. Beta-subunit mRNA accumulates to high levels in developing fruit and is to a large degree temporally separated from catalytic PG2 expression. Homologous sequences have been identified in a wide variety of plant species suggesting a broad functional role for the protein in plants. The current working theory is that the Beta-subunit defines a new class of bifunctional plant cell wall proteins that interact both with structural components of the wall and catalytic proteins, to localize and/or regulate metabolic activities within the cell wall. This hypothesis can now be tested in transgenic tomoto fruit in which Beta-subunit expression is inhibited by antisense RNA. The proposed research will further address long- standing questions of how pectin-degrading enzymes are targeted and regulated in plants and what the functional significance of pectin degradation is in various tissues and cell types. ***