Use of the Green Fluorescent Protein for Investigations of Paecilomyces fumosoroseus in Insect Hosts

The green fluorescent protein (GFP) from the jellyfish Aequorea victoria has been expressed in a variety of prokaryotic and eukaryotic organisms and has been used extensively as a marker in the study of host–pathogen interactions. We have expressed GFP in the entomopathogenic fungus Paecilomyces fumosoroseus through co-transformation with a vector that confers resistance to glufosinate ammonium. All cell types express GFP and were readily detected by fluorescence microscopy. No correlation was observed between the amount of fluorescence and the pattern of vector integration as observed by Southern analysis. Fluorescent hyphae and conidia were easily distinguished on two insect hosts, the Russian wheat aphid, Diuraphis noxia, and the diamondback moth, Plutella xylostella, and blastospores were also detected in the hemolymph of the diamondback moth. GFP-tagged strains of P. fumosoroseus can be used to study the developmental fate of the fungus within its insect hosts.