PRIMARY STRUCTURE AND EXPRESSION PATTERN OF THE 33-KDA CHITINASE GENEFROM THE MYCOPARASITIC FUNGUS TRICHODERMA-HARZIANUM

A gene (chit33) from the mycoparasitic fungus Trichoderma harzianum, c oding for a chitinase of 33 kDa, has been isolated and characterized. Partial amino-acid sequences from the purified 33-kDa chitinase were o btained. The amino-terminal peptide sequence was employed to design an oligonucleotide probe and was used as a primer to isolate a 1.2-kb cD NA, The cDNA codes for a protein of 321 amino acids, which includes a putative signal peptide of 19 amino acids. All microsequenced peptides found in this sequence, indicate that this cDNA codes for the 33-kDa chitinase. A high homology (approximately 43% identity) was found with fungal and plant chitinases, including yeast chitinases. However enzy me characteristics suggest a nutritional (saprophytic or mycoparasitic ), rather than a morphogenetic, role for this chitinase. The chit33 ge ne appears as a single copy in the T. harzianum genome, is strongly su ppressed by glucose, and de-repressed under starvation conditions as w ell as in the presence of autoclaved mycelia and/or fungal cell walls. The 33-kDa chitinase seems to be very stable except under starvation conditions. The independent regulation of each of the chitinases in T. harzianum indicates different specific roles.