Abstract
Homeobox transcription factors are conserved in eukaryotes and act as multi-functional transcription factors in filamentous fungi. Previously, it was demonstrated that HbxB governs fungal development and spore viability in Aspergillus nidulans. Here, the role of HbxB in A. nidulans was further characterized. RNA-sequencing revealed that HbxB affects the transcriptomic levels of genes associated with trehalose biosynthesis and response to thermal, oxidative, and radiation stresses in asexual spores called conidia. A phenotypic analysis found that hbxB deletion mutant conidia were more sensitive to ultraviolet stress. The loss of hbxB increased the mRNA expression of genes associated with β-glucan degradation and decreased the amount of β-glucan in conidia. In addition, hbxB deletion affected the expression of the sterigmatocystin gene cluster and the amount of sterigmatocystin. Overall, these results indicated that HbxB is a key transcription factor regulating trehalose biosynthesis, stress tolerance, β-glucan degradation, and sterigmatocystin production in A. nidulans conidia.
Highlights
Asexual spores are the main reproductive cells in most filamentous fungi [1,2]
A. nidulans reproduces primarily through asexual development and produces an asexual-specific structure called conidiophore bearing long chains of asexual spores termed as conidia [1]
A previous study demonstrated that HbxB governs conidial viability, conidial trehalose biosynthesis, and stress response in conidia [34]
Summary
Asexual spores are the main reproductive cells in most filamentous fungi [1,2]. Asexual spores are widespread in environmental niches, survive in harsh conditions, and germinate until appropriate conditions [1]. For conidia formation and maturation, three transcription factors—WetA, VosA, and VelB—mainly regulate the mRNA expression of spore-specific and developmental genes [9,10,11,12,13,14] These regulators coordinate the biosynthesis of trehalose, a key component for environmental stress tolerance, and β-glucan, a key polysaccharide for cell wall integrity [11,13,15]. With these transcription factors, several regulators, such as AtfA, VadA, and CatA, are involved in the process of spore tolerance against environmental stresses, maturation, dormancy, and germination [16,17,18,19,20]
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