Versatile EGFP reporter plasmids for cellular localization of recombinant gene products in filamentous fungi

The recent development of variants of the green fluorescent protein (GFP) with altered codon composition facilitated the efficient expression of this reporter protein in a number of fungal species. In this report, we describe the construction and application of a series of plasmids, which support the expression of an enhanced gfp (egfp) gene in filamentous fungi and assist the study of diverse developmental processes. Included were a promoterless egfp vector for monitoring the expression of cloned promoters/enhancers in fungal cells and vectors for creating translation fusions to the N-terminus of EGFP. The vectors were further modified by introducing a variant hygromycin B phosphotransferase (hph) gene, lacking the commonly found NeoI site. Instead, this site, which contained an ATG start codon, was placed in front of the egfp gene and thus was made suitable for the cloning of translational fusions. The applicability of these vectors is demonstrated by analyzing transcription regulation and protein localization and secretion in two ascomycetes, Acremonium chrysogenum and Sordaria macrospora. In the latter, the heterologous egfp gene is stably inherited during meiotic divisions, as can easily be seen from fluorescent ascospores.