EXPRESSION OF NITROGEN ASSIMILATING ENZYMES IN GERMINATING RICE UNDERANOXIA

This paper describes the synthesis and the expression of the enzymes a ssimilating nitrogen and their regulation by exogenous nitrate in the anaerobic rice (Oryza sativa L.) coleoptile. Two nitrate reductases (N R, EC 1.6.6.1), nitrite reductase (NiR, EC 1.7.7.1), cytosolic and pla stidic glutamine synthetase (GS, EC 6.3.1.2) and ferredoxin-dependent glutamate synthase (Fd-GOGAT, EC 1.4.7.1) were detected after immunopr ecipitation with specific antibodies followed by SDS-PAGE. The Norther n blot analysis revealed the presence of mRNA for NIR, cytosolic GS an d Fd-GOGAT. The addition of exogenous nitrate increased the synthesis and the expression of all these proteins with the exception of the GS polypeptides. The role of these proteins in the rice coleoptile during the anaerobic germination is discussed.