Green fluorescent protein (GFP) as a reporter gene for the plant pathogenic oomycete Phytophthora palmivora

Transgenic Phytophthora palmivora strains that produce green fluorescent protein (GFP) or β-glucuronidase (GUS) constitutively were obtained after stable DNA integration using a polyethylene-glycol and CaCl 2-based transformation protocol. GFP and GUS production were monitored during several stages of the life cycle of P. palmivora to evaluate their use in molecular and physiological studies. 40% of the GFP transformants produced the GFP to a level detectable by a confocal laser scanning microscope, whereas 75% of the GUS transformants produced GUS. GFP could be visualised readily in swimming zoospores and other developmental stages of P. palmivora cells. For high magnification microscopic studies, GFP is better visualised and was superior to GUS. In contrast, for macroscopic examination, GUS was superior. Our findings indicate that both GFP and GUS can be used successfully as reporter genes in P. palmivora.