title: Nodule-specific glutamine synthetase is expressed before the onset of nitrogen fixation in Phaseolus vulgaris L.
abstract: Glutamine synthetase expression was studied in developing root-nodules of common bean with regard to the time-course of specific activity, antigen accumulation, polypeptide composition and in vitro translation products. This analysis shows that the nodule-specific GS polypeptide (GS-gamma) is detected prior to the nitrogenase acetylene-reducing activity, and that its accumulation together with that of the GS-alpha and GS-beta polypeptides vary with nodule age. GS-gamma is present in ineffective nodules, although in a lower ratio to GS-beta than in wild-type nodules. Comparisons of in vitro translated and in vivo synthesized GS polypeptides suggest no post-translational modifications. The possible factors and mechanisms involved in the regulation of expression of GS polypeptides are discussed.
authors.affiliation: Departmento de Biología Molecular de Plantas, Centro de Investigación sobre Fijación de Nitrógeno, U.N.A.M., Apartado Postal 565-A, Cuernavaca, Mor., México.
authors.forename: J E
authors.initials: JE
authors.lastname: Padilla
authors.forename: F
authors.initials: F
authors.lastname: Campos
authors.forename: V
authors.initials: V
authors.lastname: Conde
authors.forename: M
authors.initials: M
authors.lastname: Lara
authors.forename: F
authors.initials: F
authors.lastname: Sánchez