TY  - JOUR
A1  - Zabalza, Ana
A1  - van Dongen, Joost T.
A1  - Fröhlich, Anja
A1  - Oliver, Sandra N.
A1  - Faix, Benjamin
A1  - Gupta, Kapuganti Jagadis
A1  - Schmalzlin, Elmar
A1  - Igal, Maria
A1  - Orcaray, Luis
A1  - Royuela, Mercedes
A1  - Geigenberger, Peter
T1  - Regulation of respiration and fermentation to control the plant internal oxygen concentration
N2  - Plant internal oxygen concentrations can drop well below ambient even when the plant grows under optimal conditions. Using pea (Pisum sativum) roots, we show how amenable respiration adapts to hypoxia to save oxygen when the oxygen availability decreases. The data cannot simply be explained by oxygen being limiting as substrate but indicate the existence of a regulatory mechanism, because the oxygen concentration at which the adaptive response is initiated is independent of the actual respiratory rate. Two phases can be discerned during the adaptive reaction: an initial linear decline of respiration is followed by a nonlinear inhibition in which the respiratory rate decreased progressively faster upon decreasing oxygen availability. In contrast to the cytochrome c pathway, the inhibition of the alternative oxidase pathway shows only the linear component of the adaptive response. Feeding pyruvate to the roots led to an increase of the oxygen consumption rate, which ultimately led to anoxia. The importance of balancing the in vivo pyruvate availability in the tissue was further investigated. Using various alcohol dehydrogenase knockout lines of Arabidopsis (Arabidopsis thaliana), it was shown that even under aerobic conditions, alcohol fermentation plays an important role in the control of the level of pyruvate in the tissue. Interestingly, alcohol fermentation appeared to be primarily induced by a drop in the energy status of the tissue rather than by a low oxygen concentration, indicating that sensing the energy status is an important component of optimizing plant metabolism to changes in the oxygen availability.
Y1  - 2009
UR  - http://www.plantphysiol.org/
U6  - https://doi.org/10.1104/pp.108.129288
SN  - 0032-0889
ER  - 
TY  - JOUR
A1  - Oliver, Sandra N.
A1  - Lunn, John Edward
A1  - Urbanczyk-Wochniak, Ewa
A1  - Lytovchenko, Anna
A1  - van Dongen, Joost T.
A1  - Faix, Benjamin
A1  - Schmälzlin, Elmar
A1  - Fernie, Alisdair R.
A1  - Schmäelzlin, E.
A1  - Geigenberger, Peter
T1  - Decreased expression of cytosolic pyruvate kinase in potato tubers leads to a decline in pyruvate resulting in an in vivo repression of the alternative oxidase
N2  - The aim of this work was to investigate the effect of decreased cytosolic pyruvate kinase (PKc) on potato (Solanum tuberosum) tuber metabolism. Transgenic potato plants with strongly reduced levels of PKc were generated by RNA interference gene silencing under the control of a tuber-specific promoter. Metabolite profiling showed that decreased PKc activity led to a decrease in the levels of pyruvate and some other organic acids involved in the tricarboxylic acid cycle. Flux analysis showed that this was accompanied by changes in carbon partitioning, with carbon flux being diverted from glycolysis toward starch synthesis. However, this metabolic shift was relatively small and hence did not result in enhanced starch levels in the tubers. Although total respiration rates and the ATP to ADP ratio were largely unchanged, transgenic tubers showed a strong decrease in the levels of alternative oxidase (AOX) protein and a corresponding decrease in the capacity of the alternative pathway of respiration. External feeding of pyruvate to tuber tissue or isolated mitochondria resulted in activation of the AOX pathway, both in the wild type and the PKc transgenic lines, providing direct evidence for the regulation of AOX by changes in pyruvate levels. Overall, these results provide evidence for a crucial role of PKc in the regulation of pyruvate levels as well as the level of the AOX in heterotrophic plant tissue, and furthermore reveal that these parameters are interlinked in vivo.
Y1  - 2008
UR  - http://www.plantphysiol.org/content/148/3/1640.full
U6  - https://doi.org/10.1104/pp.108.126516
ER  -