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Appl. Environ. Microbiol. doi:10.1128/AEM.01607-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Tv-bgn3, a -1,6-Glucanase from the Biocontrol Fungus Trichoderma virens is Involved in Mycoparasitism and Control of Pythium ultimum

Slavica Djonovi, Maria J. Pozo, and Charles M. Kenerley^*

Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843; Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain

^* To whom correspondence should be addressed. Email: kenerley{at}neo.tamu.edu.

	Abstract

Even though -1,6-glucanases have been purified from several filamentous fungi, the physiological function has not been conclusively established in any species. In the present study, the role of Tv-bgn3, a -1,6-glucanase from T. virens was examined by comparison of wild-type (WT) and transformant strains in which tv-bgn3 was disrupted (GKO) or constitutively over-expressed (GOE). Gene expression analysis revealed induction of tv-bgn3 in the presence of host fungal cell walls indicating regulation during mycoparasitism. Indeed, while deletion or over-expression of tv-bgn3 had no evident effect on growth and development, GOEs and GKOs showed enhanced and reduced ability, respectively, to inhibit the growth of the plant pathogen Pythium ultimum as compared to the WT. The relevance of this activity in the biocontrol ability of T. virens was confirmed in plant bioassays. Deletion of the gene resulted in significantly reduced levels of disease protection compared to the WT while GOE strains showed a significantly increased biocontrol capability. These results demonstrate the involvement of -1,6-glucanase in mycoparasitism and its relevance in the biocontrol activity of T. virens, opening a new avenue for biotechnological applications.

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