Green fluorescent protein as a reporter for gene expression in the mucoralean fungus Absidia glauca

Mucoralean fungi (Zygomycota) are used for many industrial processes and also as important model organisms for investigating basic biological problems. Their genetic analysis is severely hampered by low transformation frequencies, by their strong tendency towards autonomous replication of plasmids instead of stable integration, and by the lack of reliable genetic reporter systems. We constructed plasmids for transforming the model zygomycete Absidia glauca that carry the versatile reporter gene coding for green fluorescent protein (GFP). gfp expression is controlled either by the homologous actin promoter or the promoter for the elongation factor of translation, EF1α. These plasmids also confer neomycin resistance and carry one of two genetic elements (rag1, seg1) that improve mitotic stability of the plasmid. The gfp constructs were replicated extrachromosomally and could be recovered from retransformed Escherichia coli cells. gfp expression was monitored by epifluorescence microscopy. The gfp reporter gene plasmids presented here for the model zygomycete A. glauca constitute the first reliable system that allows the monitoring of gene expression in this important group of fungi.