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Molecular cloning and characterization of cDNAs coding for ferredoxin‐dependent glutamate synthase from Vitis vinifera
Author(s) -
Loulakakis Konstantinos A.,
RoubelakisAngelakis Kalliopi A.
Publication year - 1997
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1997.tb01840.x
Subject(s) - glutamate synthase , biology , biochemistry , southern blot , microbiology and biotechnology , gene , ferredoxin , enzyme , amino acid , glutamine synthetase , glutamine
Activity of ferredoxin‐dependent glutamate synthase (Fd‐GOGAT, EC 1.4.7.1), an enzyme with a central role in the assimilation of ammonia in higher plants, was detected in all grapevine ( Vitis vinifera L.) tissues examined. Two cDNA clones, encoding the carboxy‐ and near to amino‐terminal sequences of the Fd‐GOGAT, respectively, were isolated from a grapevine cell suspension library. The deduced amino acid sequence of the grapevine enzyme is significantly identical to the respective sequences of other known plant Fd‐GOGATs and shows homology to the alfalfa nodule NADH‐dependent GOGAT and to the large subunit of the Escherichia coli NADPH‐dependent GOGAT. DNA blot analysis suggested the existence of two Fd‐GOGAT genes in grapevine. In northern blots both clones hybridized to a 5.7‐kb transcript which was abundant in leaf and root tissues. Both, the Fd‐GOGAT mRNA and the enzymic activity increased upon illumination of leaves of dark‐grown plants suggesting that grapevine Fd‐GOGAT gene expression is regulated by light. In cell cultures, Fd‐GOGAT transcript level responded differently to the external nitrogen source, showing higher levels in the presence of nitrate and lower levels in the presence of ammonium.