COMPARISON OF CONTENTS FOR CYTOSOLIC-GLUTAMINE SYNTHETASE AND NADH-DEPENDENT GLUTAMATE SYNTHASE PROTEINS IN LEAVES OF JAPONICA, INDICA, ANDJAVANICA RICE PLANTS (REPRINTED FROM PLANT NUTRITION FOR SUSTAINABLE FOOD-PRODUCTION AND ENVIRONMENT, 1997)

As reported previously with a Japonica-type rice, Sasanishki, cytosoli c glutamine synthetase (GS1; EC 6.3.1.2) was detected in companion cel ls as well as vascular-parenchyma cells of vascular bundles of senesci ng blades (Sakurai et al., 1996), while NADH-dependent glutamate synth ase (NADH-GOGAT; EC 1.4.1.14) in the developing young tissues was loca ted in cell types where the solutes are transported from phloem and xy lem (Hayakawa et al., 1994). These results suggest that GS1 is importa nt for the export of leaf nitrogen from senescing leaves, whereas NADH -GOGAT is involved in the synthesis of glutamate from the glutamine th at is transported through the vascular system. To evaluate their funct ions further in the nitrogen remobilization and reutilization in rice, several cultivars of indica and javanica rice were tested to estimate the contents for GS1 and NADH-GOGAT protein in senescing and developi ng leaf blades, respectively. Chinsurah Boro I and Blue Stick, indica cultivars tested in the current study, contained more GS1 protein than Sasanishiki, a japonica, in the senescing leaf blades, when the conte nt was compared on an unit of g fresh weight basis. On the other hand, NADH-GOGAT content in the young leaf blades of Sasanishiki was the hi ghest.