Studies On Three Key Enzymes Involved In Ammonium Assimilation And Carbon Metabolisom During Germination And Cotyledon Development Of Luffa Cylindrical

The activities of glutamine synthetase (GS) , NAD (H) -dependent glutamate dehydrogenase (NAD (H) -GDH), NADP-dependent isocitrate dehydrogenases (NADP-ICDH) ,the level of tatol soluble protein and soluble sugar were determined during germination and cotyledon development in Luffa cylindrical. The total GS activities of cotyledons increased when cotyledons turned green. Native-PAGE analysis, together with activity staining and western blot assays, showed there were two GS isoforms in both green and etiolated cotyledons.The two isoforms expressed individually and could both be recognized by antibodies against rice GSrb. And both isoforms could be induced by light or nitrogen. The activities of NAD(H)-GDH reached the max at the end of germination and kept decreasing after cotyledon turned green. NADP-ICDH activities changed a little similar like GDH's, increasing during germination and decreasing later. NADP-ICDH activities could hardly be detected in green cotyledons, but still remained in etiolated ones. The results declared that GSwas the real key enzyme in ammonium assimilation during germination and cotyledon development, besides, GDH might play an alternative role in C/N flows. NADP-ICDH showed a similar pattern as GS during germination, but its dramatic decline in green cotyledon implies its other functions in vivo.