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Conservation and divergence in the asexual development gene regulatory network across a genus of filamentous fungi [RNA-seq]

ABSTRACT: Asexual development is fundamental to the ecology and lifestyle of filamentous fungi and can facilitate both plant and human infection. In the filamentous fungal genus Aspergillus, the production of asexual spores is primarily governed by the BrlA-AbaA-WetA central regulatory cascade. The final step in this cascade, which is controlled by the WetA protein, not only governs cellular development (i.e., the morphological differentiation of spores) but also ensures its coupling with chemical development (i.e., the coordinated production and deposition of diverse secondary metabolites, such as aflatoxins, into spores). While the wetA gene is conserved across the genus Aspergillus, the structure and degree of conservation of the BrlA-AbaA-WetA regulatory cascade and the broader wetA gene regulatory network (GRN) remain largely unknown. We carried out comparative transcriptome analyses between wetA null mutant and wild type (WT) asexual spores in three representative species spanning the diversity of the genus Aspergillus: the genetic model A. nidulans, the agricultural pest A. flavus, and the human pathogen A. fumigatus. We discovered that WetA regulates asexual sporulation in all three species via a negative feedback loop that represses BrlA, the cascade’s first step. Furthermore, ChIP-seq experiments in A. nidulans asexual spores suggest that WetA is a DNA-binding protein that interacts with a novel regulatory element, which we term the WetA Response Element (WRE). Interestingly, the WRE is found completely conserved in the non-coding region upstream of the wetA translation start site of many diverse Aspergillus genomes. In contrast, several global transcriptional regulators, most notably those in the velvet complex (veA, velB, and laeA) known to regulate the coupling between asexual development and production of secondary metabolites, show species-specific regulatory patterns. These results suggest that the BrlA-AbaA-WetA cascade’s regulatory role in cellular and chemical development of asexual spores is functionally conserved, but that the WetA-associated GRN has diverged during Aspergillus evolution. This entry is for the RNA-seq data.

ORGANISM(S): Aspergillus fumigatus Aspergillus nidulans

PROVIDER: GSE114143 | GEO | 2018/07/24

REPOSITORIES: GEO

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Project description:Asexual development is fundamental to the ecology and lifestyle of filamentous fungi and can facilitate both plant and human infection. In the filamentous fungal genus Aspergillus, the production of asexual spores is primarily governed by the BrlA-AbaA-WetA central regulatory cascade. The final step in this cascade, which is controlled by the WetA protein, not only governs cellular development (i.e., the morphological differentiation of spores) but also ensures its coupling with chemical development (i.e., the coordinated production and deposition of diverse secondary metabolites, such as aflatoxins, into spores). While the wetA gene is conserved across the genus Aspergillus, the structure and degree of conservation of the BrlA-AbaA-WetA regulatory cascade and the broader wetA gene regulatory network (GRN) remain largely unknown. We carried out comparative transcriptome analyses between wetA null mutant and wild type (WT) asexual spores in three representative species spanning the diversity of the genus Aspergillus: the genetic model A. nidulans, the agricultural pest A. flavus, and the human pathogen A. fumigatus. We discovered that WetA regulates asexual sporulation in all three species via a negative feedback loop that represses BrlA, the cascade’s first step. Furthermore, ChIP-seq experiments in A. nidulans asexual spores suggest that WetA is a DNA-binding protein that interacts with a novel regulatory element, which we term the WetA Response Element (WRE). Interestingly, the WRE is found completely conserved in the non-coding region upstream of the wetA translation start site of many diverse Aspergillus genomes. In contrast, several global transcriptional regulators, most notably those in the velvet complex (veA, velB, and laeA) known to regulate the coupling between asexual development and production of secondary metabolites, show species-specific regulatory patterns. These results suggest that the BrlA-AbaA-WetA cascade’s regulatory role in cellular and chemical development of asexual spores is functionally conserved, but that the WetA-associated GRN has diverged during Aspergillus evolution. This entry is for the ChIP-seq data.

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.

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Conservation and divergence in the asexual development gene regulatory network across a genus of filamentous fungi [RNA-seq]

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