TRANSIENT EXPRESSION OF GENES IN THE OOMYCETE PHYTOPHTHORA-INFESTANS USING BREMIA-LACTUCAE REGULATORY SEQUENCES

Vectors containing fusions between the reporter gene beta-glucuronidase (GUS) and transcriptional regulatory signals from the ham34 and hsp70 genes of the oomycete pathogen, Bremia lactucae, were introduced into protoplasts of the related fungus Phytophthora infestans. Transient expression of the GUS gene was detected when DNA was introduced into protoplasts of P. infestans by treatments with polyethylene glycol and CaCl2, with cationic liposomes, or by electroporation. After optimization of each procedure, using the transient expression assays, cationic liposomes were identified as the superior method for DNA uptake. Vectors containing the 5'hsp70 sequences and 3'ham34 sequences resulted in the maximum level of GUS activity. The identification of functional vectors for transformation, and of optimal methods for introducing DNA, should assist in achieving stable transformation of P. infestans and other oomycete the fungi.