Amanda Gálvez Mariscal

A binuclear zinc transcription factor binds the host isoflavonoid‐responsive element in a fungal cytochrome p450 gene responsible for detoxification

The PDA1 gene of the filamentous fungus Nectria haematococca MPVI (anamorph: Fusarium solani) encodes pisatin demethylase, a cytochrome P450. Pisatin is a fungistatic isoflavonoid produced by garden pea (Pisum sativum), a host for this fungus. Pisatin demethylase detoxifies pisatin and functions as a virulence factor for this fungus. Pisatin induces PDA1 expression both in cultured mycelia as well as during pathogenesis on pea. The regulatory element within PDA1 that provides pisatin‐responsive expression was identified using a combination of in vivo functional analysis and in vitro binding analysis. The 40 bp pisatin‐responsive element is located 635 bp upstream of the PDA1 transcription start site. This element was sufficient to provide strong pisatin‐induced expression to a minimal promoter in vivo and was required for pisatin regulation of the PDA1 promoter. A gene encoding a DNA‐binding protein specific to this 40 bp element was isolated from a N. haematococca cDNA library using the yeast one‐hybrid screen. The cloned gene possesses sequence motifs found in the binuclear zinc (Cys 6‐Zn 2) family of transcription factors unique to fungi. The results suggest that it is a regulator of this fungal cytochrome P450 gene and may provide pisatin‐responsive regulation.