Regulated gene silencing in the fungal pathogen Ophiostoma novo-ulmi

Abstract Ophiostoma novo-ulmi is the third most devastating fungal pathogen in Canada, affecting native Ulmus spp. Control efforts are pursuing a gene regulation approach, using RNAi cassettes driven by constitutive heterologous promoters to evaluate virulence-related genes. A homologous carbon-catabolite regulated promoter ( alc A) was developed for a cassette that regulates endopolygalacturonase (EPG) expression. Using the YFP reporter to assess promoter functionality, expression was repressed under glucose, released with its depletion and not repressed under glycerol. The EPG- alc A-RNAi cassette was similarly inactive under glucose, but highly expressed following glucose depletion, reducing EPG expression by 80–100%. Transfer to glucose medium restored native EPG expression as RNAi was down-regulated. This demonstration of RNAi regulation by carbon source offers a promising tool to evaluate gene functionality.