Effects of Glutamine on the Induction of Nitrate Reductase and Nitrite Reductase in Cultured Spinach Cells

Abstract

Summary Regulation by glutamine of the expression of nitrate reductase (NR) and nitrite reductase (NiR) was investigated in cultured spinach cells. After addition of glutamine to nitrate-containing medium, NR activity was repressed but NiR activity was not affected. Low levels of NiR protein and activity were observed in cells cultured in medium that contained glutamine as the only source of nitrogen. Changes in levels of mRNA for NR and NiR showed patterns similar to those of changes in levels of activities and proteins in glutamine-containing medium. The results suggest that genes for NR and NiR might be co-regulated by nitrate but not by glutamine and, moreover, that expression of genes for NR and NiR might be regulated by different mechanisms in cultured spinach cells.