SCREENING OF FUNGI FOR THE PRESENCE OF THE TRICHODIENE SYNTHASE ENCODING SEQUENCE BY HYBRIDIZATION TO THE TRI5 GENE CLONED FROM FUSARIUM-POAE

A trichodiene synthase gene (Tri5) was amplified from F. poae by polym erase chain reaction using synthetic primers constructed on the basis of the coding portion of the same gene from F. sporotrichioides. Seque nce analysis showed a high degree of similarity with other trichodiene synthase genes. A 378 bp HindlII fragment of the gene that contains t he genetic information for the putative active site of the trichodiene synthase enzyme was radiolabelled and used for dot blot analysis. Thi s probe could detect Tri5 hybridization in 1-10 ng DNA of fusaria that have the genetic potentiality to synthesize toxic trichothecene compo unds, but gave no reaction with trichothecene nonproducing members of the genus. When other fungi reported to produce trichothecenes (Myroth ecium, Stachybotrys, Trichoderma, Trichothecium spp.) were tested, onl y strains of Myrothecium and Stachybotrys gave strong positive reactio n. Faint but consistent hybridization signals were obtained in four sp ecies (F. semitectum, F. tricinctum, Trichoderma viride and Trichothec ium roseum) indicating the presence of nonhomologous evolutionary vari ants or inactive remnants of the Tri5 gene in these fungi.