title: Evidence for a cytosolic-dependent light induction of chloroplastic glutamine synthetase during greening of etiolated rice leaves.
abstract: During the greening of etiolated rice leaves, total glutamine synthetase activity increases about twofold, and after 48 h the level of activity usually observed in green leaves is obtained. A density-labeling experiment with deuterium demonstrates that the increase in enzyme activity is due to a synthesis of the enzyme. The enhanced activity obtained upon greening is the result of two different phenomena: there is a fivefold increase of chloroplastic glutamine synthetase content accompanied by a concommitant decrease (twofold) of the cytosolic glutamine synthetase. The increase of chloroplastic glutamine synthetase (GS2) is only inhibited by cycloheximide and not by lincomycin. This result indicates a cytosolic synthesis of GS2. The synthesis of GS2 was confirmed by a quantification of the protein by an immunochemical method. It was demonstrated that GS2 protein content in green leaves is fivefold higher than in etiolated leaves.
authors.affiliation: Laboratoire de Physiologie Végétale Métabolique, ERA CNRS no 799, Bâtiment 430, Université de Paris Sud, Centre d'Orsay, F-91405, Orsay-Cedex, France.
authors.forename: B
authors.initials: B
authors.lastname: Hirel
authors.forename: J
authors.initials: J
authors.lastname: Vidal
authors.forename: P
authors.initials: P
authors.lastname: Gadal