Abstract
NADH-dependent glutamate synthase (NADH-GOGAT) is a key enzyme in nitrogen metabolism. It catalyses the transfer of the amido-residue of glutamine to 2-oxogulutalate and generates two glutamate molecules. There are two genes encode two isoenzymes of NADH-GOGAT, i.e. NADH-GOGAT1 and 2 in rice. Immunohistochemical analysis showed that NADH-GOGAT1 protein accumulated in vascular tissues of developing organs, such as unexpanded leaves and young grains. This localization suggests that NADH-GOGAT1 re-utilizes the remobilized glutamine from senescing organs. On the other hand, NADH-GOGAT2 mRNA was mainly detected in mature senescing leaves. However, its physiological function is unknown. We recently isolated Tos17-insertion mutants of NADH-GOGAT. The phenotype of nadh-gogat1, nadh-gogat2 and their background (Nipponbare) were investigated at harvesting stage in paddy field. Top dry weight and panicle number were decreased in nadh-gogat1, whereas panicle weight and grain number were decreased in nadh-gogat2, when these were compared with Nipponbare. Different phenotypic characteristics suggest that NADH-GOGAT1 and 2 probably contribute to the yield of rice plants with different manner.
