FlbA-Regulated Gene Is Involved in Stress Resistance and Impacts Protein Secretion when Is Grown on Xylose.

Proteins are secreted throughout the mycelium of except for the sporulating zone. A link between sporulation and repression of protein secretion was underlined by the finding that inactivation of the sporulation gene results in mycelial colonies that secrete proteins throughout the colony. However, Δ strain hyphae also lyse and have thinner cell walls. This pleiotropic phenotype is associated with differential expression of 36 predicted transcription factor genes, one of which, , was inactivated in this study. Sporulation, biomass, and secretome complexity were not affected in the Δ deletion strain of the fungus. In contrast, ribosomal subunit expression and protein secretion into the medium were reduced when was grown on xylose. Moreover, the Δ strain showed decreased resistance to HO and the proteotoxic stress-inducing agent dithiothreitol. Taking the data together, RpnR is involved in proteotoxic stress resistance and impacts protein secretion when is grown on xylose. secretes a large amount and diversity of industrially relevant enzymes into the culture medium. This makes the fungus a widely used industrial cell factory. For instance, carbohydrate-active enzymes of are used in biofuel production from lignocellulosic feedstock. These enzymes represent a major cost factor in this process. Higher production yields could substantially reduce these costs and therefore contribute to a more sustainable economy and less dependence on fossil fuels. Enzyme secretion is inhibited in by asexual reproduction. The sporulation protein FlbA is involved in this process by impacting the expression of 36 predicted transcription factor genes. Here, we show that one of these predicted transcriptional regulators, RpnR, regulates protein secretion and proteotoxic stress resistance. The gene is thus an interesting target to improve enzyme production in .