CLONING AND CHARACTERIZATION OF A CHITINASE (CHIT42) CDNA FROM THE MYCOPARASITIC FUNGUS TRICHODERMA-HARZIANUM

A cDNA of Trichoderma harzianum (chit42), coding for an endochitinase of 42 kDa, has been cloned using synthetic oligonucleotides correspond ing to aminoacid sequences of the purified chitinase. The cDNA codes f or a protein of 423 amino acids. Analysis of the N-terminal amino-acid sequence of the chitinase, and comparison with that deduced from the nucleotide sequence, revealed post-translational processing of a putat ive signal peptide of 22 amino acids and a second peptide of 12 amino acids. The chit42 sequence presents overall similarities with filament ous fungal and bacterial chitinases and to a lesser extent with yeast and plant chitinases. The deduced aminoacid sequence has putative cata lytic, phosphorylation and glycosylation domains. Expression of chit42 mRNA is strongly induced by chitin and chitin-containing cell walls a nd is subjected to catabolite repression. Southern analysis shows that it is present as a single-copy gene in T. harzianum. chit42 is also d etected in several tested mycoparasitic and non-mycoparasitic fungal s trains.