The Neurospora crassa cfp promoter drives a carbon source-dependent expression of transgenes in filamentous fungi.

Abstract

The objective of the present study was to determine the potential of promoter sequences from the cfp gene of Neurospora crassa to drive the expression of transgenes in filamentous fungi. Northern blot analyses showed that the mRNA levels of cfp were rapidly modified in response to either inducing or repressing culture conditions. The hygromycin phosphotransferase (hph) and S-adenosylmethionine synthetase (eth-1) genes were fused to a minimal cfp promoter fragment (Pcfp) and used as reporter genes. These constructs were highly expressed in transformant N. crassa strains grown in media containing glucose or sucrose and repressed in media containing ethanol or ethanol plus glucose. A gene fusion of the cfp promoter to the beta-glucuronidase gene (cfp-uidA) showed identical patterns of expression in the heterologous filamentous fungus Aspergillus nidulans. Our results show that the levels of expression of the native cfp gene, as well as reporter genes driven by cfp promoter sequences, can be rapidly modified in response to different carbon sources. These modified levels of expression are maintained by continuous growth in the presence of the corresponding carbon source. We propose that the cfp promoter can be used to control the expression of transgenes in filamentous fungi in a carbon source-dependent fashion.