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Transcriptome and genome analyses of the biocontrol fungus Clonostachys rosea highlights toxin tolerance as a key biocontrol trait

Magnus Karlsson: Dept. Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences

<div>The biological control fungus <em>Clonostachys rosea</em> is able to detoxify the antifungal <em>Fusarium</em> mycotoxin zearalenone, and is tolerant towards a wide range of microbial secondary metabolites. We hypothesize that the mycoparasitic lifestyle of <em>C. rosea</em> have resulted in evolution of tolerance mechanisms against toxic secondary metabolites produced by the fungal prey, <em>C. rosea</em> itself and the surrounding soil microbiota. A transcriptomic study of <em>C. rosea</em> interacting with the fungal plant pathogens <em>F. graminearum</em> and <em>Botrytis cinerea</em> showed that 61% of all induced genes were predicted to encode ATP-binding cassette (ABC) and major facilitator superfamily (MFS) membrane transporters, while 12% were predicted to encode proteins involved in biosynthesis of secondary metabolites. Detailed evolutionary analyses showed that a majority of the membrane transporter genes belonged to families evolving under selection for increased paralog numbers, with predicted functions in multidrug resistance. Deletion of the MFS transporter gene <em>mfs464</em> resulted in mutants with increased (<em>P</em>=0.001) growth inhibitory activity against <em>F. graminearum</em>, providing evidence for a function in interspecific fungal interactions. Deletion of the ABC transporter genes <em>abcG5</em> and <em>abcG29</em> resulted in mutants that failed (<em>P</em>=0.001) to protect barley seedlings against fusarium foot rot disease in growth chamber tests. In summary, our data suggest that membrane transporters play an important role in the biology of <em>C. rosea</em>, by providing tolerance towards secondary metabolites produced by the fungal prey or <em>C. rosea</em> itself.</div>

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