The urease isozymes of soybean are relatively well-characterized genetically, biochemically and at the molecular level. From previous work, several promising areas for advancing our understanding of plant biology have emerged, and they have lead to three hypotheses which form the bases of our reserch plan. Accessory genes Eu2 and Eu3, which are necessary for the maturation of the soybean urease apoenzymes, and involved in plant (and commensal bacterial) nickel metabolism. We aim to clone these genes and to characterize their products with a goal of understanding metal utilization in plants and an aspect of plant- microbe interaction. The central physiological role of urease in plants is in the mobilization and turnover of stored protein reserves which occurs during seed germination. We will test germination signals on urease expression and will thus also address the paradox of the tissue-ubiquitous distribution of urease and its apparent non-essentiality. The seed urease-null mutation, eu1-sun, is caused by a movable genetic element in soybean. While genetic data suggest that this is so wel will work at the molecular level to confirm this hypothesis. Goals are two-fold; to elucidate the molecular basis of the mutation, and to isolate a mobile DNA element for soybean.
