Expression regulation of the endochitinase chit36 from Trichoderma asperellum (T. harzianum T-203)

The presence of the endochitinase CHIT36 from Trichoderma harzianum TM was assessed in several antagonistic Trichoderma strains belonging to different molecular taxonomic groups. CHIT37 from T. harzianum CECT 2413 was sequenced and found to display 89% homology with CHIT36 at the amino acid level. Northern analysis showed that chit36Y from T. asperellum is regulated both by glucose and nitrogen levels. Stress conditions, colloidal chitin and N-acetyl-glucosamine are effective inducers of this gene. The promoter of chit36Y was cloned and was used to direct expression of a gfp reporter gene in Trichoderma transformants. Confrontation experiments with the plant pathogen Rhizoctonia solani revealed that direct contact between the fungi is not necessary for gfp expression. The R. solani-inducing factor appears to be a soluble molecule capable of diffusing through a dialysis membrane (<12 kDa). CHIT36 recombinant protein from the yeast Pichia pastoris was active against different phytopathogens, confirming the importance of this endochitinase in the mycoparasitic activity of Trichoderma antagonistic strains.