Project description:In filamentous fungi, secondary metabolism is often linked with developmental processes such as conidiation. In this study we analyzed the link between secondary metabolism and conidiation in the main industrial producer of the β-lactam antibiotic penicillin, the ascomycete Penicillium chrysogenum. Therefore, we generated mutants defective in two central regulators of conidiation, the transcription factors BrlA and StuA, respectively. Inactivation of both BrlA and StuA blocked conidiation and altered hyphal morphology during growth on solid media, as shown by light and scanning electron microscopy, but did not affect biomass production during liquid submerged growth. Genome-wide transcriptional profiling identified a complex StuA- and BrlA-dependent regulatory network, including genes previously shown to be involved in development and secondary metabolism. Remarkably, inactivation of StuA, but not BrlA, drastically down-regulated expression of the penicillin biosynthetic gene cluster during solid and liquid submerged growth. In agreement, penicillin V production was wild type-like in BrlA-deficient strains but 99 % decreased in StuA-deficient strains during liquid submerged growth as shown by HPLC analysis. Thus, among identified regulators of penicillin V production StuA has the most severe influence. Over-expression of StuA increased the transcript levels of BrlA and AbaA (another developmental regulator), de-repressed conidiation during liquid submerged growth, but did not affect penicillin V productivity. Taken together, these data demonstrate an intimate but not exclusive link between regulation of development and secondary metabolism in P. chrysogenum. Transcriptomes of PcbrlA- and PcstuA- deletion mutants were compared with expression data from recipient strain deltaPcku70 as a control Mycelia from the transformants and the reference strain were harvested at successive stages of development for RNA extraction and hybridization on Affymetrix microarrays.

Project description:Filamentous fungi are important producers of enzymes and secondary metabolites in the biotech industry. A relatively new but highly promising fungus for industrial production is Thermothelomyces thermophilus, which is closely related to the model fungus Neurospora crassa. Nevertheless, to fully exploit the potential of T. thermophilus, a deeper understanding of its biology is necessary. A critical aspect of the filamentous fungal life cycle is the production of asexual spores (conidia), regulated by various stimuli, including nutrient availability. Under certain submerged fermentation conditions, several filamentous fungi produce conidia, which can be detrimental to product expression. In this study, we utilized RNA-seq to map transcriptomic changes during conidia production under submerged conditions in T. thermophilus. We found that the essential genes for conidiation in Aspergillus sp. and N. crassa, fluG and fluffy (fl), are not essential for conidiation in T. thermophilus. However, we identified a transcription factor, res1, whose deletion resulted in a complete loss of conidia production under fermentation conditions. This deletion also led to increased biomass production without increasing enzyme secretion. Notably, the deletion of res1 did not affect spore production on solid media. Differential gene expression analysis between the wild type and the res1 deletion mutant revealed that res1 regulates a broad range of cellular and metabolic processes, including MAPK and spore production pathways. Overexpression of res1 caused a severe growth defect and early conidia production compared to the wild type. Using ChIP-seq, we identified 35 potential target genes of res1, including known conidiation-related genes such as acon3, MAPK genes, and transcription factors like cpc1, as well as genes with unknown functions. Overall, we identified res1 to be obligatory for submerged conidia production and lay the foundation for further work on the T. thermophilus conidiation pathway and its applications.

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Reducing Aspergillus fumigatus virulence through targeted dysregulation of the conidiation pathway

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