@misc{SchmaelzlinDongenKlimantetal.2005,
  author    = {Schm{\"a}lzlin, Elmar and Dongen, Joost T. van and Klimant, Ingo and Marmod{\´e}e, Bettina and Steup, Martin and Fishahn, Joachim and Geigenberger, Peter and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {An optical multifrequency phase-modulation method using microbeads for measuring intracellular oxygen concentrations in plants},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-12232},
  year      = {2005},
  abstract  = {A technique has been developed to measure absolute intracellular oxygen concentrations in green plants. Oxygen-sensitive phosphorescent microbeads were injected into the cells and an optical multifrequency phase-modulation technique was used to discriminate the sensor signal from the strong autofluorescence of the plant tissue. The method was established using photosynthesis-competent cells of the giant algae Chara corallina L., and was validated by application to various cell types of other plant species.},
  language  = {en}
}
@article{OliverLunnUrbanczykWochniaketal.2008,
  author    = {Oliver, Sandra N. and Lunn, John Edward and Urbanczyk-Wochniak, Ewa and Lytovchenko, Anna and van Dongen, Joost T. and Faix, Benjamin and Schm{\"a}lzlin, Elmar and Fernie, Alisdair R. and Schm{\"a}elzlin, E. and Geigenberger, Peter},
  title     = {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},
  doi       = {10.1104/pp.108.126516},
  year      = {2008},
  abstract  = {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.},
  language  = {en}
}
@article{LicausiGiorgiSchmaelzlinetal.2011,
  author    = {Licausi, Francesco and Giorgi, Federico Manuel and Schmaelzlin, Elmar and Usadel, Bj{\"o}rn and Perata, Pierdomenico and van Dongen, Joost Thomas and Geigenberger, Peter},
  title     = {HRE-Type Genes are regulated by Growth-Related Changes in internal Oxygen Concentrations During the normal development of Potato (Solanum tuberosum) Tubers},
  series = {Plant \& cell physiology},
  volume    = {52},
  journal   = {Plant \& cell physiology},
  number    = {11},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0032-0781},
  doi       = {10.1093/pcp/pcr128},
  pages     = {1957 -- 1972},
  year      = {2011},
  abstract  = {The occurrence of hypoxic conditions in plants not only represents a stress condition but is also associated with the normal development and growth of many organs, leading to adaptive changes in metabolism and growth to prevent internal anoxia. Internal oxygen concentrations decrease inside growing potato tubers, due to their active metabolism and increased resistance to gas diffusion as tubers grow. In the present work, we identified three hypoxia-responsive ERF (StHRE) genes whose expression is regulated by the gradual decrease in oxygen tensions that occur when potato tubers grow larger. Increasing the external oxygen concentration counteracted the modification of StHRE expression during tuber growth, supporting the idea that the actual oxygen levels inside the organs, rather than development itself, are responsible for the regulation of StHRE genes. We identified several sugar metabolism-related genes co-regulated with StHRE genes during tuber development and possibly involved in starch accumulation. All together, our data suggest a possible role for low oxygen in the regulation of sugar metabolism in the potato tuber, similar to what happens in storage tissues during seed development.},
  language  = {en}
}
@article{ZabalzavanDongenFroehlichetal.2009,
  author    = {Zabalza, Ana and van Dongen, Joost T. and Fr{\"o}hlich, Anja and Oliver, Sandra N. and Faix, Benjamin and Gupta, Kapuganti Jagadis and Schmalzlin, Elmar and Igal, Maria and Orcaray, Luis and Royuela, Mercedes and Geigenberger, Peter},
  title     = {Regulation of respiration and fermentation to control the plant internal oxygen concentration},
  issn      = {0032-0889},
  doi       = {10.1104/pp.108.129288},
  year      = {2009},
  abstract  = {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.},
  language  = {en}
}