Molecular characterization of a novel beta-1,3-exoglucanase related to mycoparasitism of Trichoderma harzianum.
Molecular characterization of a novel beta-1,3-exoglucanase related to mycoparasitism of Trichoderma harzianum.
复制标题
与哈茨木霉真菌寄生相关的新型 β-1,3-外切葡聚糖酶的分子特征。
作者：
R. Cohen;K. Broglie;D. Friesem;R. Broglie;I. Chet
哈茨木霉是一种土传丝状真菌，能寄生多种植物病原真菌。溶解酶的分泌，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。裂解酶降解病原真菌的细胞壁，使木霉能够利用它们的细胞壁和细胞内容物作为营养。我们从T. harzianum，与海带多糖一起生长或与宿主真菌在双重培养中生长。相应的基因，lam1.3，其cDNA的分离和核苷酸序列测定。推导的氨基酸序列预测成熟蛋白的分子量为110.7kDa，不包括信号肽。LAM1.3与植物病原真菌Cochliobolus carbonum的β-1，3-外切葡聚糖酶EXG 1具有很高的同源性，而与T.哈茨木然而，它含有一个独特的C-末端体现半胱氨酸基序。lam1.3的表达在海带多糖的生长，但不与葡萄糖，被认为是相应的mRNA的差异积累的结果。
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.