GENETIC-TRANSFORMATION OF THE ECTOMYCORRHIZAL FUNGUS PAXILLUS-INVOLUTUS BY PARTICLE BOMBARDMENT

Paxillus involvutus was transformed using gold particle mediated gene transfer. Transformation was determined using the hygromycin B phospho transferase gene (hph) as the selectable marker and the beta-glucuroni dase gene (GUS) as a reporter gene. Southern blot analysis confirmed t hat the vector DNA for both hph and GUS genes was integrated into the fungal genome. Variations in the number of multiple gene copies and in sertions were found in the transformants. The hygromycin resistant tra nsformants were mitotically stable maintaining both the hph and GUS ge nes in the fungal genome six months following transformation Western b lot analysis determined that the GUS gene was capable of transcribing and translating its protein product in the transformed fungus. Enzyme assays of GUS extracts determined that beta-glucuronidase was active i n the transformed fungi. Pure culture synthesis experiments showed tha t the ability of P. involutus to form ectomychorrhizae with Pinus resi nosa was not altered by transformation. These results provide the firs t report of a successful transformation of an ectomycorrhizal fungus u sing particle bombardment.