, Volume 168, Issue 1–2, pp 20–26 | Cite as

Actin in penetration pegs of the fungal rice blast pathogen,Magnaporthe grisea

  • T. M. Bourett
  • R. J. Howard


The penetration peg is the structure used byMagnaporthe grisea to pierce the surface of rice leaves or very hard nonbiodegradable substrates. Penetration pegs produced by appressoria in vitro were examined by electron microscopy and immunofluorescence microscopy using various fluorophore labeled anti-actins. Freeze-substitution preparation of appressoria at early stages of substrate penetration showed that peg cytoplasm consisted primarily of a zone of exclusion, excluding even ribosomes, and was continuous with a similar region in the appressorium. Apical vesicles were, however, observed in short, presumably elongating pegs. Immunofluorescence microscopy was used to demonstrate binding of a monoclonal anti-actin to penetration peg cytoplasm, following “permeabilization” of appressoria by means of a brief sonication. Occasional filaments and ca. 300 nm diameter plaques were labeled in appressorial cytoplasm. Western blot analysis of germ tube extracts showed that the monoclonal probe bound predominantly to a single band with a molecular weight similar to that of rabbit muscle actin. Preincubation of the antibody with actin virtually eliminated peg labeling. We conclude that the penetration peg contains actin which may play a role in the formation of the zone of exclusion.


Appressoria Freeze substitution Immunofluorescence Plant disease Phalloidin Pyricularia 







Tris-buffered saline


Tris buffered saline plus 3% bovine serum albumin


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Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • T. M. Bourett
    • 1
  • R. J. Howard
    • 1
  1. 1.Central R&DE. I. DuPont de Nemours CompanyWilmingtonUSA

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