In vitro transcription from the Nectria haematococca PDA1 promoter in an homologous extract reflects in vivo pisatin-responsive regulation.

The PDA1 gene of Nectria haematococca MP VI (anamorph: Fusarium solani) encodes pisatin demethylase. This enzyme detoxifies the isoflavanoid phytoalexin pisatin produced by the plant on which this fungus is pathogenic. Expression of pisatin demethylase activity is induced in a mycelium by pretreatment with pisatin. We have developed homologous in vitro system which accurately initiates transcription from the PDA1 promoter. Transcription levels in vitro reflect the same pisatin-responsive stimulation as measured for PDA1 mRNA in vivo, and are dependent upon sequences in the 5' upstream region of PDA1. Pisatin-responsive transcription from the PDA1 promoter indicates that initiation of transcription is a major regulatory step in the pisatin induction of pisatin demethylase expression.