title: Over-expression of bacterial gamma-glutamylcysteine synthetase (GSH1) in plastids affects photosynthesis, growth and sulphur metabolism in poplar (Populus tremula x Populus alba) dependent on the resulting gamma-glutamylcysteine and glutathione levels.
abstract: We compared three transgenic poplar lines over-expressing the bacterial gamma-glutamylcysteine synthetase (GSH1) targeted to plastids. Lines Lggs6 and Lggs12 have two copies, while line Lggs20 has three copies of the transgene. The three lines differ in their expression levels of the transgene and in the accumulation of gamma-glutamylcysteine (gamma-EC) and glutathione (GSH) in leaves, roots and phloem exudates. The lowest transgene expression level was observed in line Lggs6 which showed an increased growth, an enhanced rate of photosynthesis and a decreased excitation pressure (1-qP). The latter typically represents a lower reduction state of the plastoquinone pool, and thereby facilitates electron flow along the electron transport chain. Line Lggs12 showed the highest transgene expression level, highest gamma-EC accumulation in leaves and highest GSH enrichment in phloem exudates and roots. This line also exhibited a reduced growth, and after a prolonged growth of 4.5 months, symptoms of leaf injury. Decreased maximum quantum yield (F(v)/F(m)) indicated down-regulation of photosystem II reaction centre (PSII RC), which correlates with decreased PSII RC protein D1 (PsbA) and diminished light-harvesting complex (Lhcb1). Potential effects of changes in chloroplastic and cytosolic GSH contents on photosynthesis, growth and the whole-plant sulphur nutrition are discussed for each line.
authors.affiliation: Institut für Forstbotanik und Baumphysiologie, Professur für Baumphysiologie, Albert-Ludwigs-Universität Freiburg, Georges-Köhler-Allee 053/054, D-79110 Freiburg i.B., Germany. cornelia.herschbach@ctp.uni-freiburg.de
authors.forename: Cornelia
authors.initials: C
authors.lastname: Herschbach
authors.forename: Luca
authors.initials: L
authors.lastname: Rizzini
authors.forename: Susanne
authors.initials: S
authors.lastname: Mult
authors.forename: Tanja
authors.initials: T
authors.lastname: Hartmann
authors.forename: Florian
authors.initials: F
authors.lastname: Busch
authors.forename: Andreas D
authors.initials: AD
authors.lastname: Peuke
authors.forename: Stanislav
authors.initials: S
authors.lastname: Kopriva
authors.forename: Ingo
authors.initials: I
authors.lastname: Ensminger
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004151:Dipeptides / Q000032:analysis; D004926:Escherichia coli / Q000201:enzymology; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism*; D005978:Glutathione / Q000032:analysis; D052585:Phloem / Q000737:chemistry; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018087:Plastids / Q000235:genetics / Q000378:metabolism; D032107:Populus / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D013457:Sulfur Compounds / Q000378:metabolism*; D019076:Transgenes
chemical_list: D001426:Bacterial Proteins; D004151:Dipeptides; D045332:Photosystem II Protein Complex; D013457:Sulfur Compounds; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; C017341:gamma-glutamylcysteine