Submitted to: Applied and Environmental Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/22/2009
Publication Date: 1/1/2010
Publication URL: doi:10.1128/AEM.02017-09
Citation: Mccormick, S.P., Alexander, N.J., Harris, L.J. 2010. CLM1 of Fusarium graminearum Encodes a Longiborneol Synthase Required for Culmorin Production. Applied and Environmental Microbiology. 76(1):136-141. doi:10.1128/AEM.02017-09. Interpretive Summary: We identified a gene that controls the first step in making the mycotoxin culmorin. Culmorin is an antifungal and phytotoxic natural product of Fusarium. Previous work suggested that it is synergistic with another mycotoxin produced by Fusarium, deoxynivalenol, and that together they inhibit growth and cause mortality in insects. Inactivating this mycotoxin biosynthetic gene provides a tool to assess how culmorin acts and interacts with other mycotoxins in causing plant diseases like wheat head scab.
Technical Abstract: Fusarium graminearum is a serious 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.