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Mutations in genes encoding sorting nexins alter production of intracellular and extracellular proteases in Aspergillus nidulans.

ABSTRACT: XprG, a putative p53-like transcriptional activator, regulates production of extracellular proteases in response to nutrient limitation and may also have a role in programmed cell death. To identify genes that may be involved in the XprG regulatory pathway, xprG2 revertants were isolated and shown to carry mutations in genes which we have named sogA-C (suppressors of xprG). The translocation breakpoint in the sogA1 mutant was localized to a homolog of Saccharomyces cerevisiae VPS5 and mapping data indicated that sogB was tightly linked to a VPS17 homolog. Complementation of the sogA1 and sogB1 mutations and identification of nonsense mutations in the sogA2 and sogB1 alleles confirmed the identification. Vps17p and Vps5p are part of a complex involved in sorting of vacuolar proteins in yeast and regulation of cell-surface receptors in mammals. Protease zymograms indicate that mutations in sogA-C permit secretion of intracellular proteases, as in S. cerevisiae vps5 and vps17 mutants. In contrast to S. cerevisiae, the production of intracellular protease was much higher in the mutants. Analysis of serine protease gene expression suggests that an XprG-independent mechanism for regulation of extracellular protease gene expression in response to carbon starvation exists and is activated in the pseudorevertants.

SUBMITTER: Katz ME

PROVIDER: S-EPMC2666495 | biostudies-literature | 2009 Apr

REPOSITORIES: biostudies-literature

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Mutations in genes encoding sorting nexins alter production of intracellular and extracellular proteases in Aspergillus nidulans.

Katz Margaret E ME Evans Cara J CJ Heagney Emma E EE vanKuyk Patricia A PA Kelly Joan M JM Cheetham Brian F BF

Genetics 20090209 4

XprG, a putative p53-like transcriptional activator, regulates production of extracellular proteases in response to nutrient limitation and may also have a role in programmed cell death. To identify genes that may be involved in the XprG regulatory pathway, xprG2 revertants were isolated and shown to carry mutations in genes which we have named sogA-C (suppressors of xprG). The translocation breakpoint in the sogA1 mutant was localized to a homolog of Saccharomyces cerevisiae VPS5 and mapping da ...[more]

PMID: 19204378

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Project description:Glutathione (GSH) is an abundant tripeptide that plays a crucial role in shielding cellular macromolecules from various reactive oxygen and nitrogen species in fungi. Understanding GSH metabolism is of vital importance for deciphering redox regulation in these microorganisms. In the present study, to better understand the GSH metabolism in filamentous fungi, we investigated functions of the dugB and dugC genes in the model fungus Aspergillus nidulans These genes are orthologues of dug2 and dug3, which are involved in cytosolic GSH degradation in Saccharomyces cerevisiae The deletion of dugB, dugC, or both resulted in a moderate increase in the GSH content in mycelia grown on glucose, reduced conidium production, and disturbed sexual development. In agreement with these observations, transcriptome data showed that genes encoding mitogen-activated protein (MAP) kinase pathway elements (e.g., steC, sskB, hogA, and mkkA) or regulatory proteins of conidiogenesis and sexual differentiation (e.g., flbA, flbC, flbE, nosA, rosA, nsdC, and nsdD) were downregulated in the ΔdugB ΔdugC mutant. Deletion of dugB and/or dugC slowed the depletion of GSH pools during carbon starvation. It also reduced accumulation of reactive oxygen species and decreased autolytic cell wall degradation and enzyme secretion but increased sterigmatocystin formation. Transcriptome data demonstrated that enzyme secretions-in contrast to mycotoxin production-were controlled at the posttranscriptional level. We suggest that GSH connects starvation and redox regulation to each other: cells utilize GSH as a stored carbon source during starvation. The reduction of GSH content alters the redox state, activating regulatory pathways responsible for carbon starvation stress responses.IMPORTANCE Glutathione (GSH) is a widely distributed tripeptide in both eukaryotes and prokaryotes. Owing to its very low redox potential, antioxidative character, and high intracellular concentration, GSH profoundly shapes the redox status of cells. Our observations suggest that GSH metabolism and/or the redox status of cells plays a determinative role in several important aspects of fungal life, including oxidative stress defense, protein secretion, and secondary metabolite production (including mycotoxin formation), as well as sexual and asexual differentiations. We demonstrated that even a slightly elevated GSH level can substantially disturb the homeostasis of fungi. This information could be important for development of new GSH-producing strains or for any biotechnologically relevant processes where the GSH content, antioxidant capacity, or oxidative stress tolerance of a fungal strain is manipulated.

Dataset Information

Mutations in genes encoding sorting nexins alter production of intracellular and extracellular proteases in Aspergillus nidulans.

Publications

Mutations in genes encoding sorting nexins alter production of intracellular and extracellular proteases in Aspergillus nidulans.

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