Metabolite Control of Nitrate Reductase Activity in Cultured Soybean Cells

Abstract

Summary Nitrogen nutritional conditions were investigated as regulators of nitrate reductase (E.C. 1.6.6.1) activity in cell cultures initiated from soybean leaves ( Glycine max var. Williams 82). Nitrate in the presence of reduced nitrogen was required for maximal cell growth and nitrate reductase activity. Cells grown with nitrate as the sole nitrogen source died after two weeks in culture, while the addition of 2 mM ammonium to the media resulted in sustained growth. When cells grown with glutamine as the sole nitrogen source were transferred to media containing nitrate, a dramatic increase in nitrate reductase activity was observed. Conversely, when cells grown with nitrate in the medium were transferred to media containing glutamine, a dramatic decay in nitrate reductase activity was observed. Finally, unlike normal leaf tissue, soybean cells in culture failed to manifest the constitutive NADPH-linked nitrate reductase activity.