Phytopathology. 1999 Aug;89(8):631-8. doi: 10.1094/PHYTO.1999.89.8.631.
ABSTRACT Ampelomyces quisqualis, a mycoparasite of fungi causing powdery mildews, exhibited high levels of extracellular exo-beta-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-beta-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-beta-1,3-glucanase and Cochliobolus carbonum EXG1 (both encoding exo-beta-1,3-glucanase) and T. harzianum bng13.1 (encoding an endo-beta-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.
摘要白粉寄生真菌（Ampelomyces quisqualis）在培养过程中表现出比粗糙脉孢菌（Neurospora crassa）和拟茎点霉（Gliocladium roseum）更高水平的细胞外外切-β-1,3-葡聚糖酶活性。A. quisqualis 培养滤液以指示细胞壁降解的方式影响由 Sphaerotheca fusca 引起的白粉病，这可通过显微镜检查来确定。从 A. quisqualis 中分离并测序了一个编码外切-β-1,3-葡聚糖酶的基因，命名为 exgA。从 exgA 推断出的预测多肽与哈茨木霉外切-β-1,3-葡聚糖酶和 Cochliobolus carbonum EXG1（均编码外切-β-1,3-葡聚糖酶）以及哈茨木霉 bng13.1（编码内切-β-1,3-葡聚糖酶）的氨基酸序列具有 46%、42%和 30%的同源性。exgA 基因具有预测的 84 kDa 分子量和 4.79 的 pI。该基因在培养物的生长后期表达，并且转录被真菌细胞壁成分诱导。exgA 的转录本水平在高度寄生的后期存在，在 A. quisqualis 菌丝中丰富，在 A. quisqualis 分生孢子囊中略少。
