Cohen-Kupiec R, Broglie K E, Friesem D, Broglie R M, Chet I
Otto-Warburg-Center for Agricultural Biotechnology, The Hebrew University of Jerusalem, Faculty of Agriculture, PO Box 12, Rehovot 76100,
Gene. 1999 Jan 21;226(2):147-54. doi: 10.1016/s0378-1119(98)00583-6.
Trichoderma harzianum, a soil-borne filamentous fungus, is capable of parasitizing several plant pathogenic fungi. Secretion of lytic enzymes, mainly glucanases and chitinases, is considered the most crucial step of the mycoparasitic process. The lytic enzymes degrade the cell walls of the pathogenic fungi, enabling Trichoderma to utilize both their cell walls and cellular contents for nutrition. We have purified a 110kDa novel extracellular beta-1,3-exoglucanase from T. harzianum, grown with laminarin or in dual cultures with host fungi. The corresponding gene, lam1.3, and its cDNA were isolated and their nucleotide sequences determined. The deduced amino-acid sequence predicted a molecular mass of 110.7kDa of a mature protein excluding a signal peptide. LAM1.3 showed high homology to EXG1, a beta-1,3-exoglucanase of the phytopathogenic fungus Cochliobolus carbonum, and a lower homology to BGN13.1, a beta-1,3-endoglucanase isolated from T. harzianum. However, it contains a unique C-terminal embodying cysteine motifs. The expression of lam1.3 in growth with laminarin, but not with glucose, was found to be a result of differential accumulation of the corresponding mRNA.
哈茨木霉是一种土壤传播的丝状真菌，能够寄生于多种植物病原真菌。分泌裂解酶，主要是葡聚糖酶和几丁质酶，被认为是真菌寄生过程中最关键的步骤。这些裂解酶可降解病原真菌的细胞壁，使哈茨木霉能够利用它们的细胞壁和细胞内含物作为营养来源。我们从在海带多糖上生长或与寄主真菌进行双重培养的哈茨木霉中纯化出了一种110 kDa的新型细胞外β-1,3-外切葡聚糖酶。分离出了相应的基因lam1.3及其cDNA，并测定了它们的核苷酸序列。推导的氨基酸序列预测成熟蛋白的分子量为110.7 kDa，不包括信号肽。LAM1.3与植物病原真菌玉米炭疽菌的β-1,3-外切葡聚糖酶EXG1具有高度同源性，与从哈茨木霉中分离出的β-1,3-内切葡聚糖酶BGN13.1同源性较低。然而，它含有一个独特的包含半胱氨酸基序的C末端。发现lam1.3在以海带多糖生长而非葡萄糖生长时的表达是相应mRNA差异积累的结果。
