NADH-glutamate synthase in alfalfa root nodules. Immunocytochemical localization

Gian B. Trepp, David W. Plank, Steve Gantt, Carroll P. Vance

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34 Scopus citations


In root nodules of alfalfa (Medicago sativa L.), N2 is reduced to NH4+ in the bacteroid by the nitrogenase enzyme and then released into the plant cytosol. The NH4+ is then assimilated by the combined action of glutamine synthetase (EC and NADH-dependent Glu synthase (NADH-GOGAT; EC into glutamine and Glu. The alfalfa nodule NADH-GOGAT protein has a 101-amino acid presequence, but the subcellular location of the protein is unknown. Using immunocytochemical localization, we determined first that the NADH-GOGAT protein is found throughout the infected cell region of both 19- and 33-d-old nodules. Second, in alfalfa root nodules NADH-GOGAT is localized predominantly to the amyloplast of infected cells. This finding, together with earlier localization and fractionation studies, indicates that in alfalfa the infected cells are the main location for the initial assimilation of fixed N2.

Original languageEnglish (US)
Pages (from-to)829-837
Number of pages9
JournalPlant physiology
Issue number3
StatePublished - Mar 1999


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