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

9408826德拉佩纳这项研究的一个长期目标是了解植物中发育调节的多糖醛酸类修饰的功能意义。作为之前NSF资助的一部分，多聚半乳糖醛酸酶(PG1)的β-亚基被提纯；编码该蛋白的cDNA被分离和鉴定。β-亚基mRNA在果实发育过程中积累到较高水平，并在很大程度上与催化的pg2表达分离。在多种植物中已经发现了同源序列，这表明该蛋白在植物中具有广泛的功能作用。目前的工作理论是，Beta亚基定义了一类新的双功能植物细胞壁蛋白，它既能与细胞壁的结构成分相互作用，又能与催化蛋白相互作用，定位和/或调节细胞壁内的代谢活动。这一假说现在可以在转基因番茄果实中得到验证，在转基因番茄中，Beta亚基的表达被反义RNA抑制。这项拟议的研究将进一步解决长期存在的问题，即果胶降解酶在植物中是如何定位和调节的，以及果胶降解在各种组织和细胞类型中的功能意义是什么。***

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. ***