AOBPreview originally published online on July 18, 2005
Annals of Botany 2005 96(4):717-726; doi:10.1093/aob/mci223
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Low Levels of Pyrophosphate in Transgenic Potato Plants Expressing E. coli Pyrophosphatase Lead to Decreased Vitality Under Oxygen Deficiency
1 Humboldt-Universität zu Berlin, Institut für Biologie, AG Pflanzenphysiologie, Philippstrasse 13, D-10115 Berlin, 2 Humboldt-Universität zu Berlin, Institut für Biologie, AG Botanik, Spaethstrasse 80/81, D-12437 Berlin and 3 Institut für Pflanzengenetik und Kulturpflanzenforschung Gatersleben, Correnstrasse 3, D-06466 Gatersleben, Germany
* For correspondence. E-mail angelika.mustroph{at}rz.hu-berlin.de
Received: 25 October 2004 Returned for revision: 12 January 2005 Accepted: 14 February 2005 Published electronically: 18 July 2005
• Background and Aims The aim of this study was to investigate the importance of pyrophosphate (PPi) for plant metabolism and survival under low oxygen stress. Responses of roots of wild-type potato plants were compared with roots of transgenic plants containing decreased amounts of PPi as a result of the constitutive expression of Escherichia coli pyrophosphatase in the cytosol.
• Methods For the experiments, roots of young wild-type and transgenic potato plants growing in nutrient solution were flushed for 4 d with nitrogen, and subsequently metabolite contents as well as enzyme activities of the glycolytic pathway were determined.
• Key Results and Conclusions In roots of transgenic plants containing 40 % less PPi, UDPglucose accumulated while the concentrations of hexose-6-phosphate, other glycolytic intermediates and ATP were decreased, leading to a growth retardation in aerated conditions. Apart from metabolic alterations, the activity of sucrose synthase was increased to a lower extent in the transgenic line than in wild type during hypoxia. These data suggest that sucrose cleavage was inhibited due to PPi deficiency already under aerated conditions, which has severe consequences for plant vitality under low oxygen. This is indicated by a reduction in the glycolytic activity, lower ATP levels and an impaired ability to resume growth after 4 d of hypoxia. Interestingly, the phosphorylation of fructose-6-phosphate via PPi-dependent phosphofructokinase was not altered in roots of transgenic plants. Nevertheless, our data provide some evidence for the importance of PPi to maintain plant growth and metabolism under oxygen deprivation.
Key words: Fermentation, glycolysis, hypoxia, pyrophosphate, Solanum tuberosum, sucrose synthase
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