title: Expression and regulation of the Escherichia coli glutamate dehydrogenase gene (gdh) in Rhizobium japonicum.
abstract: The glutamate dehydrogenase (gdh) gene of Escherichia coli was transferred into an ammonium assimilation deficient mutant (Asm-) of Rhizobium japonicum (CJ9) using plasmid pRP301, a broad host range derivative of RP4. Exconjugants capable of growth on ammonia as sole N-source occurred at a frequency of 6.8 X 10(-6). Assimilatory GDH (NADP+) activity was detected in the strain carrying the E. coli gdh gene and the pattern of ammonia assimilation via GDH was similar to that of the Asm+ wild type strain. However, GDH mediated ammonia assimilation was not subject to regulation by L-glutamate. Nitrogenase activity was expressed ex planta in R. japonicum CJ9 harbouring the gdh gene, however, the presence of the gdh gene did not restore symbiotic effectiveness to the CJ9 Asm- strain in nodules. The gdh plasmid was maintained in approximately 90% of the isolates recovered from soybean nodules.
mesh_terms: D000641:Ammonia / Q000378:metabolism; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000032:analysis; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005786:Gene Expression Regulation; D005969:Glutamate Dehydrogenase / Q000235:genetics*; D009154:Mutation; D009586:Nitrogen Fixation; D010957:Plasmids; D012231:Rhizobium / Q000201:enzymology / Q000235:genetics*; D013025:Glycine max; D013559:Symbiosis
chemical_list: D004269:DNA, Bacterial; D000641:Ammonia; D005969:Glutamate Dehydrogenase