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The transcriptional repressor TupA in Aspergillus niger is involved in controlling gene expression related to cell wall biosynthesis, development, and nitrogen source availability

ABSTRACT: The Tup1-Cyc8 (Ssn6) complex is a well characterized and conserved general transcriptional repressor complex in eukaryotic cells. Here, we report the identification of the Tup1 (TupA) homolog in the filamentous fungus Aspergillus niger in a genetic screen for mutants with a constitutive expression of the agsA gene. The agsA gene encodes a putative alpha-glucan synthase, which is induced in response to cell wall stress in A niger. Apart from the constitutive expression of agsA, the selected mutant was also found to produce an unknown pigment at high temperatures. Complementation analysis with a genomic library showed that the tupA gene could complement the phenotypes of the mutant. Screening of a collection of 240 mutants with constitutive expression of agsA identified sixteen additional pigment-secreting mutants, which were all mutated in the tupA gene. The phenotypes of the tupA mutants were very similar to the phenotypes of a tupA deletion strain. Further analysis of the tupA-17 mutant and the ΔtupA mutant revealed that TupA is also required for normal growth and morphogenesis. The production of the pigment at 37ºC is nitrogen source-dependent and repressed by ammonium. Genome-wide expression analysis of the tupA mutant during exponential growth revealed derepression of a large group of diverse genes, including genes related to development and cell wall biosynthesis, and also protease-encoding genes that are normally repressed by ammonium. Comparison of the transcriptome of up-regulated genes in the tupA mutant showed limited overlap with the transcriptome of caspofungin-induced cell wall stress-related genes, suggesting that TupA is not a general suppressor of cell wall stress-induced genes. We propose that TupA is an important repressor of genes related to development and nitrogen metabolism.

ORGANISM(S): Aspergillus niger Aspergillus niger CBS 513.88

PROVIDER: GSE50523 | GEO | 2013/12/31

SECONDARY ACCESSION(S): PRJNA217856

REPOSITORIES: GEO

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Project description:Plant growth and development is continuous and modular, a combination that allows morphogenesis by controlled cell division and elongation and serves to facilitate plantsM-bM-^@M-^Y adaptations to changing environments. Plasticity is achieved through integration of external and internal signals to regulate meristem activities. We previously characterized the pleiotropic phenotypes of the harlequin (hlq) mutant, isolated on the basis of ectopic expression of ABA- and auxin-inducible proDc3:GUS in roots and hypocotyls. Mutants are skotomorphogenic (dark development of true leaves and chlorophyll accumulation), have deformed and collapsed epidermal cells that accumulate callose and starch and stain strongly with the vital dye fluorescein diacetate, brittle stems and leaves, cell walls with a relative abundance of pectins and cell wall proteins, and abnormal and reduced root hairs and leaf trichomes. We cloned hlq and show it is an allele of brassinosteroid-insensitive3/hypocotyl6/root hairless3/Topoisomerase6B. Mutants affecting the cell wall and inhibitors of cellulose synthesis and N-glycosylation phenocopy several of the traits of hlq such as ectopic proDc3:GUS expression, lignin accumulation, and bulging root tips and epidermal cells. We performed a microarray analysis of genes differentially expressed in hlq mutants and observed coordinated expression of adjacent pairs/sets of genes suggesting a direct effect on chromatin remodeling, and significantly mis-regulated genes for histones, WRKY and IAA/AUX transcription factors, aquaporins, ubiquin E3-ligase mediated proteolysis and autophagy, biotic stress response markers, as well as numerous other cellular and metabolic processes affecting carbon partitioning into secondary metabolites lignin and anthocyanin. Our results shed light on the molecular mechanisms underlying the det/cop/fus-like pleiotropic phenotypes of hlq and support a broader role for TopoVI regulation of chromatin remodeling that mediates cell wall metabolism, growth, and development in response to environmental and hormonal signals. Seven samples; four mutant, three wild type in a dual color competitive hybridization to four microarray slides. One 'quasi-technical' replicate slide made up of pools of the three biological replicates plus a fourth mutant replicate.

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The transcriptional repressor TupA in Aspergillus niger is involved in controlling gene expression related to cell wall biosynthesis, development, and nitrogen source availability

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