AEM Accepts, published online ahead of print on 30 October 2009

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Appl. Environ. Microbiol. doi:10.1128/AEM.02017-09
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

CLM1 in Fusarium graminearum encodes a longiborneol synthase that is required for culmorin production

S. P. McCormick^*, N. J. Alexander, and L. J. Harris

Mycotoxin Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, Peoria Illinois 61604; and Eastern Cereal and Oilseed Research Centre, Agriculture & Agri-Food Canada, Ottawa, Ontario, Canada K1A 0C6

^* To whom correspondence should be addressed. Email: Susan.McCormick{at}ars.usda.gov.

Fusarium graminearum is a fungal pathogen of cereal crops (e.g. wheat, barley, maize) and produces a number of mycotoxins including 15-acetyldeoxynivalenol, butenolide, zearalenone, and culmorin. To identify a biosynthetic gene for the culmorin pathway, an EST database was examined for terpene cyclase genes. A gene designated CLM1 was expressed under trichothecene-inducing conditions. Expression of CLM1 in yeast (Saccharomyces cerevisiae) resulted in the production of a sesquiterpene alcohol, longiborneol, which has the same ring structure as culmorin. Gene disruption and add-back experiments in F. graminearum showed that CLM1 was required for culmorin biosynthesis. CLM1 gene disruptants were able to convert exogenously-added longiborneol to culmorin. Longiborneol accumulated transiently in culmorin-producing strains. The results indicate that CLM1 encodes a longiborneol synthase and is required for culmorin biosynthesis in F. graminearum.