Molecular characterization of a novel β-1,3-exoglucanase related to mycoparasitism of Trichoderma harzianum

• Published in: Gene 1999-01, Vol.226 (2), p.147-154
• Main Authors: Cohen-Kupiec, Rachel, Broglie, Karen E., Friesem, Dana, Broglie, Richard M., Chet, Ilan
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; amino acid sequences; Antagonism; b-1,3-exoglucanase; Base Sequence; beta-glucanase; beta-glucans; biological control agents; Blotting, Northern; Cell wall; Cloning, Molecular; Cochliobolus carbonum; complementary DNA; Corticium rolfsii; DNA, Complementary; genbank/aj002397; gene expression; Genes, Fungal; genetic regulation; Glucan 1,3-beta-Glucosidase; glucose; Glycoside Hydrolases - genetics; Hypocrea lixii; introns; lam 1.3 gene; Laminarin; Lytic enzymes; messenger RNA; Molecular Sequence Data; molecular weight; nucleotide sequences; parasitism; Plants - parasitology; promoter regions; Promoter Regions, Genetic; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; RNA, Messenger - metabolism; Sequence Homology, Amino Acid; structural genes; Thanatephorus cucumeris; Trichoderma - enzymology; Trichoderma - genetics; Trichoderma - physiology; Trichoderma harzianum
• ISSN: 0378-1119; 1879-0038
• 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 110 kDa novel extracellular β-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 110.7 kDa of a mature protein excluding a signal peptide. LAM1.3 showed high homology to EXG1, a β-1,3-exoglucanase of the phytopathogenic fungus Cochliobolus carbonum, and a lower homology to BGN13.1, a β-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.