CELLULAR-LOCALIZATION OF NADH-DEPENDENT GLUTAMATE-SYNTHASE PROTEIN INVASCULAR BUNDLES OF UNEXPANDED LEAF BLADES AND YOUNG GRAINS OF RICE PLANTS

Tissue and cellular localization of NADH-dependent glutamate synthase (NADH-GOGAT, EC 1.4.1.14) in the unexpanced leaf blades and young grai ns of rice (Oryza sativa L.) was investigated using tissue-print immun oblot and immunocytological methods with an affinity-purified anti-NAD H-GOGAT immunoglobulin G. Tissue-print immunoblots showed that the NAD H-GOGAT protein was mostly located in large and small vascular bundles of the unexpanded blades. When the cross-sections (10 mum in thicknes s) prepared from the paraffin-embedded blades were stained with the an tibody, the NADH-GOGAT protein was detected in vascular-parenchyma cel ls and mestome-sheath cells. In developing grains, the NADH-GOGAT prot ein was detected in both phloem- and xylem-parenchyma cells of dorsal and lateral vascular bundles, and in the nucellar projection, nucellar epidermis, and aleurone cells. On the other hand, ferredoxin (Fd)-dep endent GOGAT (EC 1.4.7.1) was located mainly in mesophyll cells of the leaf blade and in chloroplast-containing cross-cells of the pericarp of the grains. The spatial expression of these GOGAT proteins indicate s distinct and non-overlapping roles in rice plants. In the leaf blade s and young grains, NADH-GOGAT could be involved in the synthesis of g lutamate from the glutamine that is transported through the vascular s ystem from roots and senescing tissues.