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Over‐expression of bacterial γ ‐glutamylcysteine synthetase ( GSH1 ) in plastids affects photosynthesis, growth and sulphur metabolism in poplar ( Populus tremula × Populus alba ) dependent on the resulting γ ‐glutamylcysteine and glutathione levels
Author(s) -
HERSCHBACH CORNELIA,
RIZZINI LUCA,
MULT SUSANNE,
HARTMANN TANJA,
BUSCH FLORIAN,
PEUKE ANDREAS D.,
KOPRIVA STANISLAV,
ENSMINGER INGO
Publication year - 2010
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2010.02135.x
Subject(s) - glutathione , photosynthesis , phloem , biology , transgene , photosystem ii , plastid , biochemistry , photosystem i , plastoquinone , botany , chloroplast , thylakoid , gene , enzyme
ABSTRACT We compared three transgenic poplar lines over‐expressing the bacterial γ ‐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 γ ‐glutamylcysteine ( γ ‐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 γ ‐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.