Biotechnological applications of the gene transfer from the beneficial fungus Trichoderma harzianum spp. to plants.

Alternative and ecological strategies are necessary and demanded for disease management in order to reduce the use of pesticides in agriculture. Thus, the use of biological control agents such as plant growth-promoting rhizobacteria (PGPR) or several strains of the beneficial fungus Trichoderma spp. to combat plant diseases is the basis of biocontrol of plant pathogens and is a good approach to reach this healthy and environmentally adequate objective.

The overexpression in Arabidopsis thaliana of a Trichoderma harzianum gene that modulates glucosidase activity, and enhances tolerance to salt and osmotic stresses.

Using the TrichoEST database, generated in a previous functional genomics project from the beneficial filamentous fungus Trichoderma harzianum, a gene named Thkel1, which codes for a putative kelch-repeat protein, was isolated and characterized. Silencing of this gene in T. harzianum leads to a reduction of glucosidase activity and mycelial growth under abiotic stress conditions.

Functional analysis of the Trichoderma harzianum nox1 gene, encoding an NADPH oxidase, relates production of reactive oxygen species to specific biocontrol activity against Pythium ultimum.

The synthesis of reactive oxygen species (ROS) is one of the first events following pathogenic interactions in eukaryotic cells, and NADPH oxidases are involved in the formation of such ROS. The nox1 gene of Trichoderma harzianum was cloned, and its role in antagonism against phytopathogens was analyzed in nox1-overexpressed transformants. The increased levels of nox1 expression in these transformants were accompanied by an increase in ROS production during their direct confrontation with Pythium ultimum.

Transgenic expression of the Trichoderma harzianum hsp70 gene increases Arabidopsis resistance to heat and other abiotic stresses.

The ability of some Trichoderma strains, a biological control agent, to overcome extreme environmental conditions has previously been reported and related to heat-shock proteins (HSPs). These proteins are induced environmentally and are involved in important processes, acting as molecular chaperones in all organisms. In a previous study, we demonstrated, by overexpression, that the Trichoderma harzianum hsp70 gene conferred tolerance to heat and other abiotic stresses to this fungus.

Overexpression of a Trichoderma HSP70 gene increases fungal resistance to heat and other abiotic stresses.

All organisms share similar mechanisms in the heat shock response, such as synthesis of conserved heat shock proteins. Here, we report on the cloning, characterization and functional analysis of a Trichoderma harzianum T34 hsp70 gene. The expression of this gene was evaluated in cultures grown in abiotic stress conditions.