1887

Abstract

The internal hydrostatic pressure (turgor) of fungal cells is maintained at 400–500 kPa. The turgor is regulated by changes in ion flux and by production of the osmotically active metabolite glycerol. In , there are at least two genetically distinct pathways that function in adaptation to hyperosmotic shock. One involves a mitogen-activated protein (MAP) kinase cascade (kinases OS-4, OS-5 and OS-2 downstream of the osmosensing OS-1); the other is less understood, but involves the gene, which encodes a putative phosphatase. This study examined turgor regulation, electrical responses, ion fluxes and glycerol accumulation in the mutant. Turgor recovery after hyperosmotic treatment was similar to that in the wild-type, for both time-course (∼40 min) and magnitude. Prior to turgor recovery, the hyperosmotic shock caused a rapid transient depolarization of the membrane potential, followed by a sustained hyperpolarization that occurred concomitant with increased H efflux, indicating that the plasma membrane H-ATPase was being activated. These changes also occurred in the wild-type. Net fluxes of Ca and Cl during turgor recovery were similar to those in the wild-type, but K influx was attenuated in the mutant. The similar turgor recovery can be explained by the ion uptake, since glycerol did not accumulate in the mutant within the time frame of turgor recovery (but did accumulate in the wild-type). The results suggest that turgor regulation involves multi-faceted coordination of both ion flux and glycerol accumulation. Ion uptake is activated by a MAP kinase cascade, while CUT is required for glycerol accumulation.

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2007-05-01
2019-11-20
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References

  1. Alex, L. A., Borkovich, K. A. & Simon, M. I. ( 1996; ). Hyphal development in Neurospora crassa: involvement of a two-component histidine kinase. Proc Natl Acad Sci U S A 93, 3416–3421.[CrossRef]
    [Google Scholar]
  2. Beever, R. E. & Laracy, E. P. ( 1986; ). Osmotic adjustment in the filamentous fungus Aspergillus nidulans. J Bacteriol 168, 1358–1365.
    [Google Scholar]
  3. Bohnert, H. J. & Jensen, R. G. ( 1996; ). Strategies for engineering water-stress tolerance in plants. Trends Biotechnol 14, 89–97.[CrossRef]
    [Google Scholar]
  4. Bradford, M. M. ( 1976; ). A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem 72, 248–254.[CrossRef]
    [Google Scholar]
  5. Ellis, S. W., Grindle, M. & Lewis, D. H. ( 1991; ). Effect of osmotic stress on yield and polyol content of dicarboximide-sensitive and -resistant strains of Neurospora crassa. Mycol Res 95, 457–464.[CrossRef]
    [Google Scholar]
  6. Fujimura, M., Ochiai, N., Ichiishi, A., Usami, R. & Yamaguchi, I. ( 2000; ). Sensitivity to phenylpyrrole fungicides and abnormal glycerol accumulation in os and cut mutant strains of Neurospora crassa. J Pestic Sci (Nihon Noyaku Gakkai shi) 25, 31–36.[CrossRef]
    [Google Scholar]
  7. Fujimura, M., Ochiai, N., Oshima, M., Motoyama, T., Ichiishi, A., Usami, R., Horikoshi, K. & Yamaguchi, I. ( 2003; ). Putative homologs of SSK22 MAPKK kinase and PBS2 MAPK kinase of Saccharomyces cerevisiae encoded by os-4 and os-5 genes for osmotic sensitivity and fungicide resistance in Neurospora crassa. Biosci Biotechnol Biochem 67, 186–191.[CrossRef]
    [Google Scholar]
  8. Grindle, M. & Temple, W. ( 1982; ). Fungicide-resistance of os mutants of Neurospora crassa. Neurospora Newsl 29, 16–17.
    [Google Scholar]
  9. Grindle, M. & Temple, W. ( 1983; ). Fungicide resistance of smco mutants of Neurospora crassa. Neurospora Newsl 30, 7–8.
    [Google Scholar]
  10. Henriksen, G. H., Raj Raman, D., Walker, L. P. & Spanswick, R. M. ( 1992; ). Measurement of net fluxes of ammonium and nitrate at the surface of barley roots using ion-selective microelectrodes. II. Patterns of uptake along the root axis and evaluation of the microelectrode flux estimation technique. Plant Physiol 99, 734–747.[CrossRef]
    [Google Scholar]
  11. Jennings, D. H. ( 1995; ). Water relations and salinity. In The Physiology of Fungal Nutrition, pp. 398–446. Cambridge: Cambridge University Press.
  12. Kijima, K., Bahn, Y.-S. & Heitman, J. ( 2006; ). Calcineurin, Mpk1 and Hog1 MAPK pathways independently control fludioxonil antifungal sensitivity in Cryptococcus neoformans. Microbiology 152, 591–604.[CrossRef]
    [Google Scholar]
  13. Klipp, E., Nordlander, B., Kruger, R., Gennemark, P. & Hoffmann, S. ( 2005; ). Integrative model of the response of yeast to osmotic shock. Nat Biotechnol 23, 975–982.[CrossRef]
    [Google Scholar]
  14. Krantz, M. E., Becit, E. & Hoffmann, S. ( 2006; ). Comparative genomics of the HOG-signaling system in fungi. Curr Genet 49, 137–151.[CrossRef]
    [Google Scholar]
  15. Kuwana, H. ( 1953; ). Studies on the morphological mutant “cut” in Neurospora crassa. Cytologia 18, 235–239.[CrossRef]
    [Google Scholar]
  16. Lew, R. R. ( 1996; ). Pressure regulation of the electrical properties of growing Arabidopsis thaliana L. roothairs. Plant Physiol 112, 1089–1100.[CrossRef]
    [Google Scholar]
  17. Lew, R. R. ( 1999; ). Comparative analysis of Ca2+ and H+ flux magnitude and location along growing hyphae of Saprolegnia ferax and Neurospora crassa. Eur J Cell Biol 78, 892–902.[CrossRef]
    [Google Scholar]
  18. Lew, R. R. ( 2006; ). Use of double barrel micropipettes to voltage-clamp plant and fungal cells. In Plant Electrophysiology – Theory and Methods, pp. 139–154. Edited by A. G. Volkov. Berlin & New York: Springer.
  19. Lew, R. R., Levina, N. N., Walker, S. K. & Garrill, A. ( 2004; ). Turgor regulation of hyphal organisms. Fungal Genet Biol 41, 1007–1015.[CrossRef]
    [Google Scholar]
  20. Lew, R. R., Levina, N. N., Shabala, L., Anderca, M. I. & Shabala, S. N. ( 2006; ). Role of a mitogen-activated protein kinase cascade in ion flux-mediated turgor regulation in fungi. Eukaryot Cell 5, 480–487.[CrossRef]
    [Google Scholar]
  21. McCluskey, K. ( 2003; ). The Fungal Genetics Stock Center: from molds to molecules. Adv Appl Microbiol 52, 245–262.
    [Google Scholar]
  22. Miller, T. K., Renault, S. & Selitrennikoff, C. P. ( 2002; ). Molecular dissection of alleles of the osmotic-1 locus of Neurospora crassa. Fungal Genet Biol 35, 147–155.[CrossRef]
    [Google Scholar]
  23. Motoyama, T., Ohira, T., Kadokura, K., Ichiishi, A., Fujimura, M., Yamaguchi, I. & Kudo, T. ( 2005; ). An Os-1 family histidine kinase from a filamentous fungus confers fungicide-sensitivity to yeast. Curr Genet 47, 298–306.[CrossRef]
    [Google Scholar]
  24. Newman, I. A. ( 2001; ). Ion transport in roots: measurement of fluxes using ion-selective microelectrodes to characterize transporter function. Plant Cell Environ 24, 1–14.[CrossRef]
    [Google Scholar]
  25. Noguchi, R., Banno, S., Ichikawa, R., Fukumori, F., Ichiishi, A., Kimura, M., Yamaguchi, I. & Fujimura, M. ( 2007; ). Identification of OS-2 MAP kinase-dependent genes induced in response to osmotic stress, antifungal agent fludioxinil, and heat shock in Neurospora crassa. Fungal Genet Biol 44, 208–218.[CrossRef]
    [Google Scholar]
  26. Panadero, J., Pallotti, C., Rodríguez-Vargas, S., Randez-Gil, F. & Prieto, J. A. ( 2006; ). A downshift in temperature activates the high osmolarity glycerol (HOG) pathway, which determines freeze tolerance in Saccharomyces cerevisiae. J Biol Chem 281, 4638–4645.[CrossRef]
    [Google Scholar]
  27. Perkins, D. D., Radford, A. & Sachs, M. S. ( 2001; ). The Neurospora Compendium: Chromosomal Loci. San Diego: Academic Press.
  28. Schumacher, M. M. C. S., Enderlin, C. S. & Selitrennikoff, C. P. ( 1997; ). The osmotic-1 locus of Neurospora crassa encodes a putative histidine kinase similar to osmosensors of bacteria and yeast. Curr Microbiol 34, 340–347.[CrossRef]
    [Google Scholar]
  29. Shabala, S. & Lew, R. R. ( 2002; ). Turgor regulation in osmotically stressed Arabidopsis thaliana epidermal root cells: direct support for the role of inorganic ion uptake as revealed by concurrent flux and cell turgor measurements. Plant Physiol 129, 290–299.[CrossRef]
    [Google Scholar]
  30. Smith, P. J. S., Hammar, K., Porterfield, D. M., Sanger, R. H. & Trimarchi, J. R. ( 1999; ). Self-referencing, non-invasive, ion selective electrode for single cell detection of trans-plasma membrane calcium flux. Microsc Res Tech 48, 398–417.
    [Google Scholar]
  31. Vogel, H. J. ( 1956; ). A convenient growth medium for Neurospora. Microb Genet Bull 13, 42–46.
    [Google Scholar]
  32. Youssar, L. & Avalos, J. ( 2006; ). Light-dependent regulation of the gene cut-1 of Neurospora, involved in the osmotic stress response. Fungal Genet Biol 43, 752–763.[CrossRef]
    [Google Scholar]
  33. Youssar, L., Schmidhauser, T. J. & Avalos, J. ( 2005; ). The Neurospora crassa gene responsible for the cut and ovc phenotypes encodes a protein of the haloacid dehalogenase family. Mol Microbiol 55, 828–838.
    [Google Scholar]
  34. Zhang, Y., Lamm, R., Pillonel, C., Lam, S. & Xu, J.-R. ( 2002; ). Osmoregulation and fungicide resistance: the Neurospora crassa os-2 gene encodes a HOG1 mitogen-activated protein kinase homologue. Appl Environ Microbiol 68, 532–538.[CrossRef]
    [Google Scholar]
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