The novel spore-specific regulator SscA controls Aspergillus conidiogenesis

Abstract

ABSTRACT A major group of fungi produces asexual spores (conidia) for dissemination and propagation and, in pathogenic fungi, for infection. Despite the critical role of conidia, the underlying mechanism of spore formation, integrity, and viability is not fully elucidated. In this study, we have identified and investigated the roles of the spore-specific transcription factor (TF) SscA in three Aspergillus species, including A. nidulans , A. flavus , and A. fumigatus, which is a model system, toxin producer, or a prevalent human pathogen, respectively. Comparative transcriptomic analyses have revealed that 25 TF encoding genes showed higher mRNA levels in conidia than in hyphae in three species. Functional analyses of the 25 genes have identified SscA as a key TF for conidial formation, maturation, germination, integrity, amino acid production, and secondary metabolism in Aspergillus nidulans conidia. Importantly, the roles of SscA are conserved in other Aspergillus species. Altogether, our study demonstrates that SscA is a spore-specific TF that governs the production of intact and functional conidial formation in Aspergillus species. IMPORTANCE Filamentous fungi produce myriads of asexual spores, which are the main reproductive particles that act as infectious or allergenic agents. Although the serial of asexual sporogenesis is coordinated by various genetic regulators, there remain uncharacterized transcription factors in Aspergillus . To understand the underlying mechanism of spore formation, integrity, and viability, we have performed comparative transcriptomic analyses on three Aspergillus species and found a spore-specific transcription factor, SscA. SscA has a major role in conidial formation, maturation and dormancy, and germination in Aspergillus nidulans . Functional studies indicate that SscA coordinates conidial wall integrity, amino acid production, and secondary metabolism in A. nidulans conidia. Furthermore, the roles of SscA are conserved in other Aspergillus species. Our findings that the SscA has broad functions in Aspergillus conidia will help to understand the conidiogenesis of Aspergillus species.