The research planned is directed toward increasing understanding of regulation of nitrate reductase activity in higher plants. The specific objective of this project is to analyze, at the molecular level, the flavin domain of corn leaf nitrate reductase. The recombinant form of this enzyme is produced in a bacterium. An aspect of this analysis is to generate a vector with an appropriate gene insert so that both the flavin and cytochrome domains of the enzyme will be expressed in the bacterium, thus making possible easy production of large amounts of the enzyme. Plants assimilate the nitrate-nitrogen of soil and water into their cell materials initially be means of the enzyme nitrate-reductase. The details of the regulation of the formation of this enzyme are incomplete, and the aim of this project is to enlarge our understanding of this significant process.