Enzyme diffusion from Trichoderma atroviride (= T-harzianum P1) to Rhizoctonia solani is a prerequisite for triggering of Trichoderma ech42 gene expression before mycoparasitic contact

A plate confrontation experiment is commonly used to study the mechanism by which Trichoderma spp. antagonize and parasitize other fungi. Previous wor k with chitinase gene expression (ech42) during the precontact period of th is process in which cellophane and dialysis membranes separated Trichoderma harzianum and its host Rhizoctonia solani resulted in essentially opposite results. Here, we show that cellophane membranes are permeable to proteins up to at least 90 kDa in size but that dialysis membranes are not. ech142 was expressed during the precontact stage of the confrontation between Tric hoderma atroviride and its host only if the cellophane was placed between t he two fungi. These results are consistent with enzyme diffusion from T. at roviride to R. solani generating the trigger of ech42 gene expression.