MOLECULAR-GENETICS OF NITRATE REDUCTASE IN HIGHER-PLANTS

This chapter discusses the biochemical characteristics of nitrate reductase in higher plants. The chapter focuses on the structure and regulation of the apoenzyme genes such as the identification of the loci involved in nitrate reduction in Arabidopsis thaliana and Nicotiana plumbaginifolia. The chapter discusses the genetic aspects of nitrate reduction by considering plant mutants deficient for this activity. Nitrate is the main nitrogen source assimilated by plants but ammonium or other nitrogen-containing organic molecules can also be used. In higher plants, nitrate is reduced in two steps by nitrate reductase and nitrite reductase that successively catalyze the reduction of nitrate to nitrite and then to the ammonium ion in an eight-electron reduction process. Nitrate reductases from fungi, algae, or higher plants are typical examples of multicenter redox enzymes that catalyze the two-electron reduction of nitrate to nitrite using pyridine dinucleotides as electron donors. It is now well established that the nitrate reductase gene is a powerful tool for plant cell genetics as a marker that can be selected or counter selected. © 1992, Academic Press Inc.