CONTROL OF NITRATE REDUCTION IN PLANTS

The reduction of nitrate to nitrite is a critical step in the assimilation of nitrogen for most terrestrial plants. This reaction is catalysed by the enzyme nitrate reductase. Much has been learned about this enzyme over the past 40 years. Biochemical and molecular studies have provided insights into the structure of the enzyme and its prosthetic groups and molybdenum cofactor. Analysis of mutants that are defective in nitrate reduction has shed light on the nature and number of genes required for the synthesis of the nitrate reductase holoenzyme. Physiological studies have revealed an intricate and complex regulatory system that controls the expression of the nitrate reductase gene in response to environmental signals such as nitrate, light and carbon dioxide. In this paper we review what is known about the properties of nitrate reductase and its regulation in angiosperms with special emphasis on Arabidopsis thaliana.