Glutamate metabolism on Solanum lycopersicon grown under cadmium stress conditions

Glutamate occupies a central position in aminoacid metabolism in plants. However, it is also the substrate for the synthesis of glutamine from ammonia, catalysed by glutamine synthetase. The a-amino group of glutamate may be transferred to other aminoacids. In addition, both the carbon skeleton and a-amino group of glutamate form the basis for the synthesis of gamma-aminobutyric acid, arginine and proline. Finally, glutamate may be deaminated by glutamate dehydrogenase to form ammonia and 2-oxoglutarate. The concentrations of glutamate within the plant are homeostatically regulated by the combined action of these pathways is examined. Glutamine represented the major aminoacid transported through xylem sap of cadmium treated and control plants. Cadmium treatment increased the total aminoacid content in the phloem, maintaining Gln/Glu ratios. Glutamate signalling is examined from an evolutionary perspective, and the roles it might play in plants.