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The Mycoparasite Ampelomyces quisqualis Expresses exgA Encoding an exo-β-1,3-Glucanase in Culture and During Mycoparasitism

August 1999 , Volume 89 , Number  8
Pages  631 - 638

Yaniv Rotem , Oded Yarden , Abraham Sztejnberg

First, second, and third authors: Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel; second author: The Otto Warburg Center for Agricultural Biotechnology, The Hebrew University of Jerusalem, Rehovot 76100, Israel

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Accepted for publication 11 May 1999.

Ampelomyces quisqualis, a mycoparasite of fungi causing powdery mildews, exhibited high levels of extracellular exo-β-1,3-glucanase activity in culture compared with Neurospora crassa and Gliocladium roseum. A. quisqualis culture filtrates affected powdery mildew caused by Sphaerotheca fusca in a manner indicative of cell wall degradation, as determined by microscopic examination. A gene encoding an exo-β-1,3-glucanase in A. quisqualis, designated exgA, was isolated and sequenced. The predicted polypeptide deduced from exgA had 46, 42, and 30% identity with amino acid sequences of Trichoderma harzianum exo-β-1,3-glucanase and Cochliobolus carbonum EXG1 (both encoding exo-β-1,3-glucanase) and T. harzianum bng13.1 (encoding an endo-β-1,3-glucanase), respectively. The exgA gene had a predicted molecular mass of 84 kDa and a pI of 4.79. The gene was expressed during the late stages of growth in culture, and transcription was induced by fungal cell wall components. Transcript levels for exgA were present during late stages of hyperpar-asitism and were abundant along A. quisqualis mycelium and were slightly less abundant in A. quisqualis pycnidia.

Additional keywords: lytic enzymes.

© 1999 The American Phytopathological Society