Trichoderma spp.are important biocontrol filamentous fungi which are widely used for their characteristics of various adaptability, broad anti-microbial spectrum and a variety of antagonistic mechanisms.The expression of genes associated with biocontrol appears to be regulated by intracellular signal transduction pathway.G protein-mediated signal transduct-ion system is an important class of transmembrane signaling system in eukaryotic cell and plays a key role in the regulation of cellular reactions and the transmission of extracellular signals to the cells.Heterotrimetric G protein is composed of α, β, and γ subunits and each subunit is encoded by independent gene.Gα subunit is considered to be a functional subunit of G protein.