Cloning and characterization of the Thcut1 gene encoding a cutinase of Trichoderma harzianum T34

The cloning and characterization of the Thcut1 gene, which encodes a cutinase protein of the biocontrol fungus Trichoderma harzianum T34, is reported. Cutinases, which are secreted enzymes that hydrolyse cutin, belong to a class of serine esterases able to hydrolyze fatty acid esters and emulsified triglycerides. The Thcut1 gene was isolated by screening of a genomic DNA library from EST 2104, generated from a T. harzianum T34 cDNA library constructed under mycoparasitic and nutrient stress conditions, as a probe. Thcut1 shows similarity with fungal cutinase genes and is present as a single copy in the genome of T. harzianum. RNA blot analyses revealed that Thcut1 mRNA is strongly induced in vitro by olive oil and the cutin monomer 16-hydroxy-hexadecanoic acid and that it is repressed by glucose. Significant transcript levels were also detected when strawberry plants or pectin were present in the media and in the absence of glucose. Expression of the Thcut1 gene in Pichia pastoris gave rise to transformants with high esterase activity and a high level of secretion of the THCUT1 protein. Recombinant cutinase secretion at flask level indicated that P. pastoris transformants could be applied to set up the production of this enzyme at industrial scale.