Transformation of Acremonium coenophialum, a protective fungal symbiont of the grass Festuca arundinacea

Acremonium coenophialum is a mutualistic mycosymbiont and natural agent of biological protection of the widely distributed grass Festuca arundinacea (tall fescue). An electroporative transformation system was developed for A. coenophialum. Segments of DNA 5′ to the β-tubulin gene (tub2) of the closely related ascomycete Epichloë typhina, fused to the Escherichia coli hph gene encoding hygromycin B phosphotransferase, conferred hygromycin resistance when introduced into A. coenophialum by electroporation. The incorporation of the Emericella nidulans trpC terminator greatly increased protoplast germination on selective medium and improved transformation efficiencies 30-200% depending on the plasmid construct. Plasmid pCSN43, which incorporates the trpC controlling elements for hph expression, was also used to transform A. coenophialum. Southern blot analysis of ten pCSN43 transformants indicated the possibility of random integration of this vector into the genome.