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.
Overall design: For the A. fumigatus experiments, 3 technical replicates of each genotype (wild type and deletion mutant) were sequenced. For the A. nidulans experiments, 4 technical replicates of each genotype (wild type and deletion mutant) were sequenced. The A. nidulans RNA samples were paired-end in nature, making 8 total samples.
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