Evidence for Dicer-dependent RNA interference in the industrial penicillin producer Penicillium chrysogenum

RNA interference (RNAi) is a sequence-specific post-transcriptional gene silencing system downregulates target gene expression. Here, we provide several lines of evidence for RNA silencing in the industrial beta-lactam antibiotic producer Penicillium chrysogenum using the reporter gene under the control of the constitutive trpC promoter or the inducible xylP The functional RNAi system was verified by detection of siRNAs that hybridized exclusively gene-specific P-32-labelled RNA probes. Moreover, when RNAi was used to silence the endogenous PcbrlA morphogene that controls conidiophore development, a dramatic reduction the formation of conidiospores was observed in 47% of the corresponding transformants. Evidence that RNAi in P. chrysogenum is dependent on a Dicer peptide was provided with a strain lacking Pcdcl2. In the Delta Pcdcl2 background, silencing of the PcbrlA gene was tested. of the transformants analysed showed a developmental defect. The applicability of the RNAi system in P. chrysogenum was finally demonstrated by silencing the Pcku70 gene to increase homologous recombination frequency. This led to the generation of single and double mutants.