Role of glutamate availability on cadmium induced changes of nitrogen and glutamate in tomato plants (Solanum lycopersicon)

Maximal glutamine synthetase (GS, EC 6.3.1.2) activity and free aminoacid accumulation occur together in the leaves and roots. GS and specific GS activities although declining in the stressed leaves. In the other hand, the decrease of GS activity in the roots is contrarily accompanied by an increase in specific GS activity in roots in treated plants. Maximal GS activity is correlated with the peak degradation of the free aminoacid and protein in the two organs. Western blots analysis from Cd treated plants shows a decrease in chloroplastic GS (GS2) and an increase in cytosolic GS (GS1) proteins. In the roots, free aminoacids accumulated as NADH-dependent glutamate synthase (NADH-GOGAT, EC 2.6.1.5.3) and specific activities increase. Maximal leaf NADH-GOGAT activity occurs simultaneously with maximal leaf aminating glutamate dehydrogenase (NADH-GDH, EC 1.4.1.2) activity.