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 |
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| Authors: | CORNELIA HERSCHBACH LUCA RIZZINI SUSANNE MULT TANJA HARTMANN FLORIAN BUSCH ANDREAS D. PEUKE STANISLAV KOPRIVA INGO ENSMINGER |
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| Affiliation: | 1. Institut für Forstbotanik und Baumphysiologie, Professur für Baumphysiologie, Albert‐Ludwigs‐Universit?t Freiburg, Georges‐K?hler‐Allee 053/054, D‐79110 Freiburg i.B., Germany,;2. Department of Biology and The BIOTRON, University of Western Ontario, London, ON, Canada N6A 5B7 and;3. Present address: Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada M5S 3B2.;4. Present address: ADP International Plant Science Consulting, Talstrasse 8, 79194 Gundelfingen‐Wildtal, Germany.;5. Present address: John Innes Centre, Norwich NR4 7UH, UK.;6. Department of Biology, University of Toronto, Mississauga, ON, Canada L5L 1C6 |
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| 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 (Fv/Fm) 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. |
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| Keywords: | APS reductase ATP sulphurylase chlorophyll fluorescence glutathione long‐distance transport maximum quantum yield phloem photosystem II sulphate assimilation transgenic poplar |
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