The Secondary Metabolite Toxin, Sirodesmin PL, and Its Role in Virulence of the Blackleg Fungus

  • Barbara J. Howlett
  • Ellen M. Fox
  • Anton J. Cozijnsen
  • Angela P. Van de Wouw
  • Candace E. Elliott
Chapter
Part of the Plant Pathology in the 21st Century book series (ICPP, volume 3)

Abstract

Sirodesmin PL is a secondary metabolite toxin produced by Leptosphaeria maculans, a fungus that causes blackleg disease of oilseed rape (Brassica napus). Biosynthesis of this epipolythiodioxopiperazine (ETP) toxin involves a cluster of 18 co-regulated genes. Putative ETP gene clusters have been found in 14 taxa discontinuously distributed amongst ascomycetes. Movement of entire clusters by horizontal gene transfer is the most parsimonious hypothesis to explain this discontinuous distribution. A mutant of L. maculans that does not produce sirodesmin PL forms similar sized lesions on cotyledons of B. napus to those formed by the wild type. However, it is half as effective in colonising stems, as indicated by reduced lesion size and reduced fungal biomass. This implicates sirodesmin PL as a virulence factor in B. napus stems. Expression patterns of two of the cluster genes is consistent with the distribution of sirodesmin PL in planta, as revealed by mass spectrometry experiments. The sirodesmin-deficient mutant has less antibacterial and antifungal activity than the wild type, suggesting that sirodesmin PL may play a role in protecting L.maculans against competition from other micro-organisms.

Keywords

Horizontal gene transfer mycotoxin secondary metabolite sirodesmin 

Notes

Acknowledgements

We thank the Australian Research Council and the Grains Research and Development Corporation for funding our research.

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Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  • Barbara J. Howlett
    • 1
  • Ellen M. Fox
    • 1
  • Anton J. Cozijnsen
    • 1
  • Angela P. Van de Wouw
    • 1
  • Candace E. Elliott
    • 1
  1. 1.School of BotanyThe University of MelbourneMelbourneAustralia

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