Skip to main content
PMC home page
The Plant Cell logoLink to The Plant Cell
. 1999 Oct;11(10):2045–2058. doi: 10.1105/tpc.11.10.2045

Independent signaling pathways regulate cellular turgor during hyperosmotic stress and appressorium-mediated plant infection by Magnaporthe grisea.

K P Dixon 1, J R Xu 1, N Smirnoff 1, N J Talbot 1
PMCID: PMC144108  PMID: 10521531

Abstract

The phytopathogenic fungus Magnaporthe grisea elaborates a specialized infection cell called an appressorium with which it mechanically ruptures the plant cuticle. To generate mechanical force, appressoria produce enormous hydrostatic turgor by accumulating molar concentrations of glycerol. To investigate the genetic control of cellular turgor, we analyzed the response of M. grisea to hyperosmotic stress. During acute and chronic hyperosmotic stress adaptation, M. grisea accumulates arabitol as its major compatible solute in addition to smaller quantities of glycerol. A mitogen-activated protein kinase-encoding gene OSM1 was isolated from M. grisea and shown to encode a functional homolog of HIGH-OSMOLARITY GLYCEROL1 (HOG1), which encodes a mitogen-activated protein kinase that regulates cellular turgor in yeast. A null mutation of OSM1 was generated in M. grisea by targeted gene replacement, and the resulting mutants were sensitive to osmotic stress and showed morphological defects when grown under hyperosmotic conditions. M. grisea deltaosm1 mutants showed a dramatically reduced ability to accumulate arabitol in the mycelium. Surprisingly, glycerol accumulation and turgor generation in appressoria were unaltered by the Deltaosm1 null mutation, and the mutants were fully pathogenic. This result indicates that independent signal transduction pathways regulate cellular turgor during hyperosmotic stress and appressorium-mediated plant infection. Consistent with this, exposure of M. grisea appressoria to external hyperosmotic stress induced OSM1-dependent production of arabitol.

Full Text

The Full Text of this article is available as a PDF (620.6 KB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Adachi K., Hamer J. E. Divergent cAMP signaling pathways regulate growth and pathogenesis in the rice blast fungus Magnaporthe grisea. Plant Cell. 1998 Aug;10(8):1361–1374. doi: 10.1105/tpc.10.8.1361. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Albertyn J., Hohmann S., Thevelein J. M., Prior B. A. GPD1, which encodes glycerol-3-phosphate dehydrogenase, is essential for growth under osmotic stress in Saccharomyces cerevisiae, and its expression is regulated by the high-osmolarity glycerol response pathway. Mol Cell Biol. 1994 Jun;14(6):4135–4144. doi: 10.1128/mcb.14.6.4135. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Alspaugh J. A., Perfect J. R., Heitman J. Cryptococcus neoformans mating and virulence are regulated by the G-protein alpha subunit GPA1 and cAMP. Genes Dev. 1997 Dec 1;11(23):3206–3217. doi: 10.1101/gad.11.23.3206. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Altschul S. F., Gish W., Miller W., Myers E. W., Lipman D. J. Basic local alignment search tool. J Mol Biol. 1990 Oct 5;215(3):403–410. doi: 10.1016/S0022-2836(05)80360-2. [DOI] [PubMed] [Google Scholar]
  5. Banuett F., Herskowitz I. Discrete developmental stages during teliospore formation in the corn smut fungus, Ustilago maydis. Development. 1996 Oct;122(10):2965–2976. doi: 10.1242/dev.122.10.2965. [DOI] [PubMed] [Google Scholar]
  6. Banuett F. Signalling in the yeasts: an informational cascade with links to the filamentous fungi. Microbiol Mol Biol Rev. 1998 Jun;62(2):249–274. doi: 10.1128/mmbr.62.2.249-274.1998. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Beckerman J. L., Naider F., Ebbole D. J. Inhibition of pathogenicity of the rice blast fungus by Saccharomyces cerevisiae alpha-factor. Science. 1997 May 16;276(5315):1116–1119. doi: 10.1126/science.276.5315.1116. [DOI] [PubMed] [Google Scholar]
  8. Blomberg A., Adler L. Physiology of osmotolerance in fungi. Adv Microb Physiol. 1992;33:145–212. doi: 10.1016/s0065-2911(08)60217-9. [DOI] [PubMed] [Google Scholar]
  9. Brewster J. L., Gustin M. C. Positioning of cell growth and division after osmotic stress requires a MAP kinase pathway. Yeast. 1994 Apr;10(4):425–439. doi: 10.1002/yea.320100402. [DOI] [PubMed] [Google Scholar]
  10. Brewster J. L., de Valoir T., Dwyer N. D., Winter E., Gustin M. C. An osmosensing signal transduction pathway in yeast. Science. 1993 Mar 19;259(5102):1760–1763. doi: 10.1126/science.7681220. [DOI] [PubMed] [Google Scholar]
  11. Choi W., Dean R. A. The adenylate cyclase gene MAC1 of Magnaporthe grisea controls appressorium formation and other aspects of growth and development. Plant Cell. 1997 Nov;9(11):1973–1983. doi: 10.1105/tpc.9.11.1973. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Crawford M. S., Chumley F. G., Weaver C. G., Valent B. Characterization of the Heterokaryotic and Vegetative Diploid Phases of MAGNAPORTHE GRISEA. Genetics. 1986 Dec;114(4):1111–1129. doi: 10.1093/genetics/114.4.1111. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Feinberg A. P., Vogelstein B. A technique for radiolabeling DNA restriction endonuclease fragments to high specific activity. Anal Biochem. 1983 Jul 1;132(1):6–13. doi: 10.1016/0003-2697(83)90418-9. [DOI] [PubMed] [Google Scholar]
  14. Gao S., Nuss D. L. Distinct roles for two G protein alpha subunits in fungal virulence, morphology, and reproduction revealed by targeted gene disruption. Proc Natl Acad Sci U S A. 1996 Nov 26;93(24):14122–14127. doi: 10.1073/pnas.93.24.14122. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Gold S., Duncan G., Barrett K., Kronstad J. cAMP regulates morphogenesis in the fungal pathogen Ustilago maydis. Genes Dev. 1994 Dec 1;8(23):2805–2816. doi: 10.1101/gad.8.23.2805. [DOI] [PubMed] [Google Scholar]
  16. Gustin M. C., Albertyn J., Alexander M., Davenport K. MAP kinase pathways in the yeast Saccharomyces cerevisiae. Microbiol Mol Biol Rev. 1998 Dec;62(4):1264–1300. doi: 10.1128/mmbr.62.4.1264-1300.1998. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Hall J. P., Cherkasova V., Elion E., Gustin M. C., Winter E. The osmoregulatory pathway represses mating pathway activity in Saccharomyces cerevisiae: isolation of a FUS3 mutant that is insensitive to the repression mechanism. Mol Cell Biol. 1996 Dec;16(12):6715–6723. doi: 10.1128/mcb.16.12.6715. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Hamer J. E., Howard R. J., Chumley F. G., Valent B. A mechanism for surface attachment in spores of a plant pathogenic fungus. Science. 1988 Jan 15;239(4837):288–290. doi: 10.1126/science.239.4837.288. [DOI] [PubMed] [Google Scholar]
  19. Han S. J., Choi K. Y., Brey P. T., Lee W. J. Molecular cloning and characterization of a Drosophila p38 mitogen-activated protein kinase. J Biol Chem. 1998 Jan 2;273(1):369–374. doi: 10.1074/jbc.273.1.369. [DOI] [PubMed] [Google Scholar]
  20. Herskowitz I. MAP kinase pathways in yeast: for mating and more. Cell. 1995 Jan 27;80(2):187–197. doi: 10.1016/0092-8674(95)90402-6. [DOI] [PubMed] [Google Scholar]
  21. Hirayama T., Maeda T., Saito H., Shinozaki K. Cloning and characterization of seven cDNAs for hyperosmolarity-responsive (HOR) genes of Saccharomyces cerevisiae. Mol Gen Genet. 1995 Nov 15;249(2):127–138. doi: 10.1007/BF00290358. [DOI] [PubMed] [Google Scholar]
  22. Howard R. J., Ferrari M. A., Roach D. H., Money N. P. Penetration of hard substrates by a fungus employing enormous turgor pressures. Proc Natl Acad Sci U S A. 1991 Dec 15;88(24):11281–11284. doi: 10.1073/pnas.88.24.11281. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Howard R. J., Valent B. Breaking and entering: host penetration by the fungal rice blast pathogen Magnaporthe grisea. Annu Rev Microbiol. 1996;50:491–512. doi: 10.1146/annurev.micro.50.1.491. [DOI] [PubMed] [Google Scholar]
  24. Johnson L. N., Noble M. E., Owen D. J. Active and inactive protein kinases: structural basis for regulation. Cell. 1996 Apr 19;85(2):149–158. doi: 10.1016/s0092-8674(00)81092-2. [DOI] [PubMed] [Google Scholar]
  25. Kumar S., McLaughlin M. M., McDonnell P. C., Lee J. C., Livi G. P., Young P. R. Human mitogen-activated protein kinase CSBP1, but not CSBP2, complements a hog1 deletion in yeast. J Biol Chem. 1995 Dec 8;270(49):29043–29046. doi: 10.1074/jbc.270.49.29043. [DOI] [PubMed] [Google Scholar]
  26. Lee Y. H., Dean R. A. cAMP Regulates Infection Structure Formation in the Plant Pathogenic Fungus Magnaporthe grisea. Plant Cell. 1993 Jun;5(6):693–700. doi: 10.1105/tpc.5.6.693. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Liu S., Dean R. A. G protein alpha subunit genes control growth, development, and pathogenicity of Magnaporthe grisea. Mol Plant Microbe Interact. 1997 Dec;10(9):1075–1086. doi: 10.1094/MPMI.1997.10.9.1075. [DOI] [PubMed] [Google Scholar]
  28. Maeda T., Takekawa M., Saito H. Activation of yeast PBS2 MAPKK by MAPKKKs or by binding of an SH3-containing osmosensor. Science. 1995 Jul 28;269(5223):554–558. doi: 10.1126/science.7624781. [DOI] [PubMed] [Google Scholar]
  29. Maeda T., Wurgler-Murphy S. M., Saito H. A two-component system that regulates an osmosensing MAP kinase cascade in yeast. Nature. 1994 May 19;369(6477):242–245. doi: 10.1038/369242a0. [DOI] [PubMed] [Google Scholar]
  30. Millar J. B., Buck V., Wilkinson M. G. Pyp1 and Pyp2 PTPases dephosphorylate an osmosensing MAP kinase controlling cell size at division in fission yeast. Genes Dev. 1995 Sep 1;9(17):2117–2130. doi: 10.1101/gad.9.17.2117. [DOI] [PubMed] [Google Scholar]
  31. Mitchell T. K., Dean R. A. The cAMP-dependent protein kinase catalytic subunit is required for appressorium formation and pathogenesis by the rice blast pathogen Magnaporthe grisea. Plant Cell. 1995 Nov;7(11):1869–1878. doi: 10.1105/tpc.7.11.1869. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Money NP. Mechanism linking cellular pigmentation and pathogenicity in rice blast disease . Fungal Genet Biol. 1997 Dec;22(3):151–152. doi: 10.1006/fgbi.1997.1017. [DOI] [PubMed] [Google Scholar]
  33. Norbeck J., Pâhlman A. K., Akhtar N., Blomberg A., Adler L. Purification and characterization of two isoenzymes of DL-glycerol-3-phosphatase from Saccharomyces cerevisiae. Identification of the corresponding GPP1 and GPP2 genes and evidence for osmotic regulation of Gpp2p expression by the osmosensing mitogen-activated protein kinase signal transduction pathway. J Biol Chem. 1996 Jun 7;271(23):13875–13881. doi: 10.1074/jbc.271.23.13875. [DOI] [PubMed] [Google Scholar]
  34. O'Rourke S. M., Herskowitz I. The Hog1 MAPK prevents cross talk between the HOG and pheromone response MAPK pathways in Saccharomyces cerevisiae. Genes Dev. 1998 Sep 15;12(18):2874–2886. doi: 10.1101/gad.12.18.2874. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Posas F., Saito H. Activation of the yeast SSK2 MAP kinase kinase kinase by the SSK1 two-component response regulator. EMBO J. 1998 Mar 2;17(5):1385–1394. doi: 10.1093/emboj/17.5.1385. [DOI] [PMC free article] [PubMed] [Google Scholar]
  36. Posas F., Wurgler-Murphy S. M., Maeda T., Witten E. A., Thai T. C., Saito H. Yeast HOG1 MAP kinase cascade is regulated by a multistep phosphorelay mechanism in the SLN1-YPD1-SSK1 "two-component" osmosensor. Cell. 1996 Sep 20;86(6):865–875. doi: 10.1016/s0092-8674(00)80162-2. [DOI] [PubMed] [Google Scholar]
  37. Pöpping B., Gibbons T., Watson M. D. The Pisum sativum MAP kinase homologue (PsMAPK) rescues the Saccharomyces cerevisiae hog1 deletion mutant under conditions of high osmotic stress. Plant Mol Biol. 1996 May;31(2):355–363. doi: 10.1007/BF00021795. [DOI] [PubMed] [Google Scholar]
  38. Robinson M. J., Cobb M. H. Mitogen-activated protein kinase pathways. Curr Opin Cell Biol. 1997 Apr;9(2):180–186. doi: 10.1016/s0955-0674(97)80061-0. [DOI] [PubMed] [Google Scholar]
  39. Sheikh-Hamad D., Di Mari J., Suki W. N., Safirstein R., Watts B. A., 3rd, Rouse D. p38 kinase activity is essential for osmotic induction of mRNAs for HSP70 and transporter for organic solute betaine in Madin-Darby canine kidney cells. J Biol Chem. 1998 Jan 16;273(3):1832–1837. doi: 10.1074/jbc.273.3.1832. [DOI] [PubMed] [Google Scholar]
  40. Talbot N. J., Ebbole D. J., Hamer J. E. Identification and characterization of MPG1, a gene involved in pathogenicity from the rice blast fungus Magnaporthe grisea. Plant Cell. 1993 Nov;5(11):1575–1590. doi: 10.1105/tpc.5.11.1575. [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. Talbot N. J. Having a blast: exploring the pathogenicity of Magnaporthe grisea. Trends Microbiol. 1995 Jan;3(1):9–16. doi: 10.1016/s0966-842x(00)88862-9. [DOI] [PubMed] [Google Scholar]
  42. Thompson J. D., Higgins D. G., Gibson T. J. CLUSTAL W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight matrix choice. Nucleic Acids Res. 1994 Nov 11;22(22):4673–4680. doi: 10.1093/nar/22.22.4673. [DOI] [PMC free article] [PubMed] [Google Scholar]
  43. Valent B., Farrall L., Chumley F. G. Magnaporthe grisea genes for pathogenicity and virulence identified through a series of backcrosses. Genetics. 1991 Jan;127(1):87–101. doi: 10.1093/genetics/127.1.87. [DOI] [PMC free article] [PubMed] [Google Scholar]
  44. Wong B., Murray J. S., Castellanos M., Croen K. D. D-arabitol metabolism in Candida albicans: studies of the biosynthetic pathway and the gene that encodes NAD-dependent D-arabitol dehydrogenase. J Bacteriol. 1993 Oct;175(19):6314–6320. doi: 10.1128/jb.175.19.6314-6320.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  45. Xu J. R., Hamer J. E. MAP kinase and cAMP signaling regulate infection structure formation and pathogenic growth in the rice blast fungus Magnaporthe grisea. Genes Dev. 1996 Nov 1;10(21):2696–2706. doi: 10.1101/gad.10.21.2696. [DOI] [PubMed] [Google Scholar]
  46. Xu J. R., Staiger C. J., Hamer J. E. Inactivation of the mitogen-activated protein kinase Mps1 from the rice blast fungus prevents penetration of host cells but allows activation of plant defense responses. Proc Natl Acad Sci U S A. 1998 Oct 13;95(21):12713–12718. doi: 10.1073/pnas.95.21.12713. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from The Plant Cell are provided here courtesy of Oxford University Press

RESOURCES