Changes in Distribution of Fixed Nitrogen by Timing the Ammonium Assimilation and the Overproduction of Nitrogenase in Rhizobium etli

The first product of nitrogen fixation in legume nodules is ammonium. This compound is excreted from the bacteroid into the infected cell cytoplasm and is quickly assimilated by the enzymes glutamine synthetase (GS) and glutamate synthase (GOGAT). We have previously communicated mat the constitutive production of an exogenous GDH protein prevents nodulation of Phaseolus vulgaris roots (Mendoza, A. et. al. 1995. MPMI 8:584).