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AOBPreview published online on October 20, 2006
Annals of Botany, doi:10.1093/aob/mcl205
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© The Author 2006. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Received June 15, 2006
Revised July 27, 2006
Accepted August 24, 2006

Article

Antifungal Properties of Haem Peroxidase from Acorus calamus

MODHUMITA GHOSH 1 *

1 Division of Plant Biotechnology, Institute of Forest Genetics and Tree Breeding, Forest Campus, R.S. Puram, Coimbatore--641 002, India

* To whom correspondence should be addressed.
MODHUMITA GHOSH, E-mail: ghoshm{at}ifgtb.res.in


  Abstract

• Background and Aims Plants have evolved a number of inducible defence mechanisms against pathogen attack, including synthesis of pathogenesis-related proteins. The aim of the study was to purify and characterize antifungal protein from leaves of Acorus calamus.

• Methods Leaf proteins from A. calamus were fractionated by cation exchange chromatography and gel filtration and the fraction inhibiting the hyphal extension of phytopathogens was characterized. The temperature stability and pH optima of the protein were determined and its presence was localized in the leaf tissues.

• Key Results The purified protein was identified as a class III haem peroxidase with a molecular weight of approx. 32 kDa and pI of 7·93. The temperature stability of the enzyme was observed from 5 °C to 60 °C with a temperature optimum of 36 °C. Maximum enzyme activity was registered at pH 5·5. The pH and temperature optima were corroborated with the antifungal activity of the enzyme. The enzyme was localized in the leaf epidermal cells and lumen tissues of xylem, characteristic of class III peroxidases. The toxic nature of the enzyme which inhibited hyphal growth was demonstrated against phytopathogens such as Macrophomina phaseolina, Fusarium moniliforme and Trichosporium vesiculosum. Microscopic observations revealed distortion in the hyphal structure with stunted growth, increased volume and extensive hyphal branching.

• Conclusions This study indicates that peroxidases may have a role to play in host defence by inhibiting the hyphal extension of invading pathogens.

Keywords: Acorus calamus, haem peroxidase, antifungal, hyphal inhibition, thermal stability, localization, epidermal cells, xylem lumen.
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