Limits...
Genome-wide expression analysis upon constitutive activation of the HacA bZIP transcription factor in Aspergillus niger reveals a coordinated cellular response to counteract ER stress.

Carvalho ND, Jørgensen TR, Arentshorst M, Nitsche BM, van den Hondel CA, Archer DB, Ram AF - BMC Genomics (2012)

Bottom Line: In addition to the well known HacA targets such as the ER resident foldases and chaperones, GO enrichment analysis revealed up-regulation of genes involved in protein glycosylation, phospholipid biosynthesis, intracellular protein transport, exocytosis and protein complex assembly in the HacACA mutant.Biological processes over-represented in the down-regulated genes include those belonging to central metabolic pathways, translation and transcription.The results indicate that the constitutive activation of the HacA leads to a coordinated regulation of the folding and secretion capacity of the cell, but with consequences on growth and fungal physiology to reduce secretion stress.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Biology Leiden, Leiden University, Molecular Microbiology and Biotechnology, BE Leiden, The Netherlands.

ABSTRACT

Background: HacA/Xbp1 is a conserved bZIP transcription factor in eukaryotic cells which regulates gene expression in response to various forms of secretion stress and as part of secretory cell differentiation. In the present study, we replaced the endogenous hacA gene of an Aspergillus niger strain with a gene encoding a constitutively active form of the HacA transcription factor (HacACA). The impact of constitutive HacA activity during exponential growth was explored in bioreactor controlled cultures using transcriptomic analysis to identify affected genes and processes.

Results: Transcription profiles for the wild-type strain (HacAWT) and the HacACA strain were obtained using Affymetrix GeneChip analysis of three replicate batch cultures of each strain. In addition to the well known HacA targets such as the ER resident foldases and chaperones, GO enrichment analysis revealed up-regulation of genes involved in protein glycosylation, phospholipid biosynthesis, intracellular protein transport, exocytosis and protein complex assembly in the HacACA mutant. Biological processes over-represented in the down-regulated genes include those belonging to central metabolic pathways, translation and transcription. A remarkable transcriptional response in the HacACA strain was the down-regulation of the AmyR transcription factor and its target genes.

Conclusions: The results indicate that the constitutive activation of the HacA leads to a coordinated regulation of the folding and secretion capacity of the cell, but with consequences on growth and fungal physiology to reduce secretion stress.

Show MeSH

Related in: MedlinePlus

Effects of the constitutive activation of the UPR on the utilization of different polimeric and monomeric carbon sources. The wild-type strain (HacAWT), the strain containing a constitutive active form of hacA (HacACA) the amyR disruptant (ΔamyR) and inuR disruptant (ΔinuR) strains were grown on MM containing 1% of the different carbon sources or 1% dried skim milk at 30 °C for 4 days.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3472299&req=5

Figure 7: Effects of the constitutive activation of the UPR on the utilization of different polimeric and monomeric carbon sources. The wild-type strain (HacAWT), the strain containing a constitutive active form of hacA (HacACA) the amyR disruptant (ΔamyR) and inuR disruptant (ΔinuR) strains were grown on MM containing 1% of the different carbon sources or 1% dried skim milk at 30 °C for 4 days.

Mentions: As predicted from the transcriptomic data and similar to the ΔamyR strain, HacACA was unable to grow on the plate containing starch as sole carbon source. With the aim of testing if this reduced growth was specific for growth on starch or if it would apply to other complex carbohydrates, we performed a similar test on other polymers, inulin, xylan and pectin and respective monomeric substrates, fructose, xylose and galacturonic acid (Figure 7). In addition, growth of the HacACA strain was analysed on milk-plates (Figure 7). These results show that the HacACA strain is growth impaired when challenged to assimilate nutrients from complex substrates. Although this was not so evident when grown on inulin, growth of the HacACA strain was clearly further reduced on xylan, pectin and milk-plates suggesting that the down-regulation of extracellular enzyme expression is not limited to the amylolytic genes, but also for xylanolytic, pectinolytic and proteolytic genes.


Genome-wide expression analysis upon constitutive activation of the HacA bZIP transcription factor in Aspergillus niger reveals a coordinated cellular response to counteract ER stress.

Carvalho ND, Jørgensen TR, Arentshorst M, Nitsche BM, van den Hondel CA, Archer DB, Ram AF - BMC Genomics (2012)

Effects of the constitutive activation of the UPR on the utilization of different polimeric and monomeric carbon sources. The wild-type strain (HacAWT), the strain containing a constitutive active form of hacA (HacACA) the amyR disruptant (ΔamyR) and inuR disruptant (ΔinuR) strains were grown on MM containing 1% of the different carbon sources or 1% dried skim milk at 30 °C for 4 days.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472299&req=5

Figure 7: Effects of the constitutive activation of the UPR on the utilization of different polimeric and monomeric carbon sources. The wild-type strain (HacAWT), the strain containing a constitutive active form of hacA (HacACA) the amyR disruptant (ΔamyR) and inuR disruptant (ΔinuR) strains were grown on MM containing 1% of the different carbon sources or 1% dried skim milk at 30 °C for 4 days.
Mentions: As predicted from the transcriptomic data and similar to the ΔamyR strain, HacACA was unable to grow on the plate containing starch as sole carbon source. With the aim of testing if this reduced growth was specific for growth on starch or if it would apply to other complex carbohydrates, we performed a similar test on other polymers, inulin, xylan and pectin and respective monomeric substrates, fructose, xylose and galacturonic acid (Figure 7). In addition, growth of the HacACA strain was analysed on milk-plates (Figure 7). These results show that the HacACA strain is growth impaired when challenged to assimilate nutrients from complex substrates. Although this was not so evident when grown on inulin, growth of the HacACA strain was clearly further reduced on xylan, pectin and milk-plates suggesting that the down-regulation of extracellular enzyme expression is not limited to the amylolytic genes, but also for xylanolytic, pectinolytic and proteolytic genes.

Bottom Line: In addition to the well known HacA targets such as the ER resident foldases and chaperones, GO enrichment analysis revealed up-regulation of genes involved in protein glycosylation, phospholipid biosynthesis, intracellular protein transport, exocytosis and protein complex assembly in the HacACA mutant.Biological processes over-represented in the down-regulated genes include those belonging to central metabolic pathways, translation and transcription.The results indicate that the constitutive activation of the HacA leads to a coordinated regulation of the folding and secretion capacity of the cell, but with consequences on growth and fungal physiology to reduce secretion stress.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Biology Leiden, Leiden University, Molecular Microbiology and Biotechnology, BE Leiden, The Netherlands.

ABSTRACT

Background: HacA/Xbp1 is a conserved bZIP transcription factor in eukaryotic cells which regulates gene expression in response to various forms of secretion stress and as part of secretory cell differentiation. In the present study, we replaced the endogenous hacA gene of an Aspergillus niger strain with a gene encoding a constitutively active form of the HacA transcription factor (HacACA). The impact of constitutive HacA activity during exponential growth was explored in bioreactor controlled cultures using transcriptomic analysis to identify affected genes and processes.

Results: Transcription profiles for the wild-type strain (HacAWT) and the HacACA strain were obtained using Affymetrix GeneChip analysis of three replicate batch cultures of each strain. In addition to the well known HacA targets such as the ER resident foldases and chaperones, GO enrichment analysis revealed up-regulation of genes involved in protein glycosylation, phospholipid biosynthesis, intracellular protein transport, exocytosis and protein complex assembly in the HacACA mutant. Biological processes over-represented in the down-regulated genes include those belonging to central metabolic pathways, translation and transcription. A remarkable transcriptional response in the HacACA strain was the down-regulation of the AmyR transcription factor and its target genes.

Conclusions: The results indicate that the constitutive activation of the HacA leads to a coordinated regulation of the folding and secretion capacity of the cell, but with consequences on growth and fungal physiology to reduce secretion stress.

Show MeSH
Related in: MedlinePlus