@article{JunemannWinterhoffNordholzetal.2013,
  author    = {Junemann, Alexander and Winterhoff, Moritz and Nordholz, Benjamin and Rottner, Klemens and Eichinger, Ludwig and Gr{\"a}f, Ralph and Faix, Jan},
  title     = {ForC lacks canonical formin activity but bundles actin filaments and is required for multicellular development of Dictyostelium cells},
  series = {European journal of cell biology},
  volume    = {92},
  journal   = {European journal of cell biology},
  number    = {6-7},
  publisher = {Elsevier},
  address   = {Jena},
  issn      = {0171-9335},
  doi       = {10.1016/j.ejcb.2013.07.001},
  pages     = {201 -- 212},
  year      = {2013},
  abstract  = {Diaphanous-related formins (DRFs) drive the nucleation and elongation of linear actin filaments downstream of Rho GTPase signalling pathways. Dictyostelium formin C (ForC) resembles a DRF, except that it lacks a genuine formin homology domain 1 (FH1), raising the questions whether or not ForC can nucleate and elongate actin filaments. We found that a recombinant ForC-FH2 fragment does not nucleate actin polymerization, but moderately decreases the rate of spontaneous actin assembly and disassembly, although the barbed-end elongation rate in the presence of the formin was not markedly changed. However, the protein bound to and crosslinked actin filaments into loose bundles of mixed polarity. Furthermore, ForC is an important regulator of morphogenesis since ForC-null cells are severely impaired in development resulting in the formation of aberrant fruiting bodies. Immunoblotting revealed that ForC is absent during growth, but becomes detectable at the onset of early aggregation when cells chemotactically stream together to form a multicellular organism, and peaks around the culmination stage. Fluorescence microscopy of cells ectopically expressing a GFP-tagged, N-terminal ForC fragment showed its prominent accumulation in the leading edge, suggesting that ForC may play a role in cell migration. In agreement with its expression profile, no defects were observed in random migration of vegetative mutant cells. Notably, chemotaxis of starved cells towards a source of cAMP was severely impaired as opposed to control. This was, however, largely due to a marked developmental delay of the mutant, as evidenced by the expression profile of the early developmental marker csA. In line with this, chemotaxis was almost restored to wild type levels after prolonged starvation. Finally, we observed a complete failure of phototaxis due to abolished slug formation and a massive reduction of spores consistent with forC promoter-driven expression of beta-galactosidase in prespore cells. Together, these findings demonstrate ForC to be critically involved in signalling of the cytoskeleton during various stages of 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}
}
@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}
}