Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

MAP Kinase and Protein Kinase A: Dependent Mobilization of Triacylglycerol and Glycogen during Appressorium Turgor Generation by Magnaporthe grisea

Eckhard Thines, Roland W. S. Weber and Nicholas J. Talbot
The Plant Cell
Vol. 12, No. 9 (Sep., 2000), pp. 1703-1718
DOI: 10.2307/3871184
Stable URL: http://www.jstor.org/stable/3871184
Page Count: 16
  • Read Online (Free)
  • Subscribe ($19.50)
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
MAP Kinase and Protein Kinase A: Dependent Mobilization of Triacylglycerol and Glycogen during Appressorium Turgor Generation by Magnaporthe grisea
Preview not available

Abstract

Magnaporthe grisea produces an infection structure called an appressorium, which is used to breach the plant cuticle by mechanical force. Appressoria generate hydrostatic turgor by accumulating molar concentrations of glycerol. To investigate the genetic control and biochemical mechanism for turgor generation, we assayed glycerol biosynthetic enzymes during appressorium development, and the movement of storage reserves was monitored in developmental mutants. Enzymatic activities for glycerol generation from carbohydrate sources were present in appressoria but did not increase during development. In contrast, triacylglycerol lipase activity increased during appressorium maturation. Rapid glycogen degradation occurred during conidial germination, followed by accumulation in incipient appressoria and dissolution before turgor generation. Lipid droplets also moved to the incipient appressorium and coalesced into a central vacuole before degrading at the onset of turgor generation. Glycogen and lipid mobilization did not occur in a Δpmk1 mutant, which lacked the mitogen-activated protein kinase (MAPK) required for appressorium differentiation, and was retarded markedly in a ΔcpkA mutant, which lacks the catalytic subunit of cAMP-dependent protein kinase A (PKA). Glycogen and lipid degradation were very rapid in a Δmac1 sum1-99 mutant, which carries a mutation in the regulatory subunit of PKA, occurring before appressorium morphogenesis was complete. Mass transfer of storage carbohydrate and lipid reserves to the appressorium therefore occurs under control of the PMK1 MAPK pathway. Turgor generation then proceeds by compartmentalization and rapid degradation of lipid and glycogen reserves under control of the CPKA/SUM1-encoded PKA holoenzyme.

Page Thumbnails

  • Thumbnail: Page 
[1703]
    [1703]
  • Thumbnail: Page 
1704
    1704
  • Thumbnail: Page 
1705
    1705
  • Thumbnail: Page 
1706
    1706
  • Thumbnail: Page 
1707
    1707
  • Thumbnail: Page 
1708
    1708
  • Thumbnail: Page 
1709
    1709
  • Thumbnail: Page 
1710
    1710
  • Thumbnail: Page 
1711
    1711
  • Thumbnail: Page 
1712
    1712
  • Thumbnail: Page 
1713
    1713
  • Thumbnail: Page 
1714
    1714
  • Thumbnail: Page 
1715
    1715
  • Thumbnail: Page 
1716
    1716
  • Thumbnail: Page 
1717
    1717
  • Thumbnail: Page 
1718
    1718