Abstract
The homeobox domain-containing transcription factors play an important role in the growth, development, and secondary metabolism in fungi and other eukaryotes. In this study, we characterized the roles of the genes coding for homeobox-type proteins in the model organism Aspergillus nidulans. To examine their roles in A. nidulans, the deletion mutant strains for each gene coding for homeobox-type protein were generated, and their phenotypes were examined. Phenotypic analyses revealed that two homeobox proteins, HbxA and HbxB, were required for conidia production. Deletion of hbxA caused abnormal conidiophore production, decreased the number of conidia in both light and dark conditions, and decreased the size of cleistothecia structures. Overexpressing hbxA enhanced the production of asexual spores and formation of conidiophore under the liquid submerged conditions. The hbxB deletion mutant strains exhibited decreased asexual spore production but increased cleistothecia production. The absence of hbxB decreased the trehalose content in asexual spores and increased their sensitivity against thermal and oxidative stresses. The ΔhbxA strains produced more sterigmatocystin, which was decreased in the ΔhbxB strain. Overall, our results show that HbxA and HbxB play crucial roles in the differentiation and secondary metabolism of the fungus A. nidulans.
Highlights
Aspergillus nidulans is a model filamentous fungus commonly used for the understanding of the genetics and molecular biology of fungal development and secondary metabolism[1,2,3]
Their predicted protein sequences were aligned with the sequences of A. fumigatus and A. flavus homeobox proteins using Clustal Omega, and the aligned sequences were input to MEGA software
Genes coding for homeobox-type proteins are associated with various fungal processes, including conidiation, virulence, and secondary metabolisms
Summary
Aspergillus nidulans is a model filamentous fungus commonly used for the understanding of the genetics and molecular biology of fungal development and secondary metabolism[1,2,3]. Homeobox proteins are highly conserved transcription factors that act as master developmental regulators in most multicellular organisms[32,33,34] These proteins contain a 60–amino-acid–long homeodomain that contains the DNA-binding helix-turn-helix motif[35], whereby they bind to their target genes involved in fungal differentiation[36]. In the rice blast fungus Magnaporthe oryzae, eight genes coding for homeobox-type proteins have been characterized Several of them, such as MoHOX2 and MoHOX7, are required for asexual reproduction, appressorium development, and pathogenesis[40,41]. The two homeobox transcription factors HbxA and HbxB were further functionally characterized We found that these two proteins were required for the reproduction and ST metabolism of A. nidulans. HbxB governs the trehalose biosynthesis and stress tolerance in A. nidulans conidia
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