Limits...
Core oxidative stress response in Aspergillus nidulans.

Emri T, Szarvas V, Orosz E, Antal K, Park H, Han KH, Yu JH, Pócsi I - BMC Genomics (2015)

Bottom Line: We also found that both oxidative and salt stresses induced expression of some secondary metabolite gene clusters and the deletion of atfA enhanced the stress responsiveness of additional clusters.Our data suggest that the observed co-regulations were most likely consequences of the overlapping physiological effects of the stressors and not of the existence of a general environmental stress response.Both stress inducible and stress repressive regulations of secondary metabolism seem to be frequent features in A. nidulans.

View Article: PubMed Central - PubMed

Affiliation: Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, P.O. Box 63, H-4032, Debrecen, Hungary. emri.tamas@science.unideb.hu.

ABSTRACT

Background: The b-Zip transcription factor AtfA plays a key role in regulating stress responses in the filamentous fungus Aspergillus nidulans. To identify the core regulons of AtfA, we examined genome-wide expression changes caused by various stresses in the presence/absence of AtfA using A. nidulans microarrays. We also intended to address the intriguing question regarding the existence of core environmental stress response in this important model eukaryote.

Results: Examination of the genome wide expression changes caused by five different oxidative stress conditions in wild type and the atfA mutant has identified a significant number of stereotypically regulated genes (Core Oxidative Stress Response genes). The deletion of atfA increased the oxidative stress sensitivity of A. nidulans and affected mRNA accumulation of several genes under both unstressed and stressed conditions. The numbers of genes under the AtfA control appear to be specific to a stress-type. We also found that both oxidative and salt stresses induced expression of some secondary metabolite gene clusters and the deletion of atfA enhanced the stress responsiveness of additional clusters. Moreover, certain clusters were down-regulated by the stresses tested.

Conclusion: Our data suggest that the observed co-regulations were most likely consequences of the overlapping physiological effects of the stressors and not of the existence of a general environmental stress response. The function of AtfA in governing various stress responses is much smaller than anticipated and/or other regulators may play a redundant or overlapping role with AtfA. Both stress inducible and stress repressive regulations of secondary metabolism seem to be frequent features in A. nidulans.

No MeSH data available.


Related in: MedlinePlus

Cross adaptations observed in the control and ΔatfA strains. The control (white columns) and ΔatfA (grey columns) strains were pre-cultured for 0.5 h in the presence of various stress initiating agents as indicated. Following pre-treatments, fungi were exposed to 0.18 mM MSB (Part a) or 1.0 M NaCl (Part b) in fresh culture media. All cultures were incubated for 18 h, and increases in the dry cell mass (DCM) values were determined, which are presented here as means ± S.D. values (n = 3). Untreated cultures were not subjected to stress treatments at all meanwhile control cultures were exposed to MSB and NaCl without stress pre-treatments. *Significant differences in comparison to control cultures calculated by Student’s t-test (p < 0.05, n = 3)
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4482186&req=5

Fig3: Cross adaptations observed in the control and ΔatfA strains. The control (white columns) and ΔatfA (grey columns) strains were pre-cultured for 0.5 h in the presence of various stress initiating agents as indicated. Following pre-treatments, fungi were exposed to 0.18 mM MSB (Part a) or 1.0 M NaCl (Part b) in fresh culture media. All cultures were incubated for 18 h, and increases in the dry cell mass (DCM) values were determined, which are presented here as means ± S.D. values (n = 3). Untreated cultures were not subjected to stress treatments at all meanwhile control cultures were exposed to MSB and NaCl without stress pre-treatments. *Significant differences in comparison to control cultures calculated by Student’s t-test (p < 0.05, n = 3)

Mentions: Although only few core stress response genes (Table 3) were found in both the control and the ΔatfA strains the stress responses still shared some common motives when the physiological functions of the up-regulated and down-regulated genes were compared. Among the significant shared GO terms “sterol metabolic process” (MSB, l-H2O2, h- H2O2, tBOOH and diamide) and “ribosome biogenesis” (MSB, h- H2O2, tBOOH, diamide and NaCl) were characteristic for down regulated gene, meanwhile “branched-chain amino acid biosynthetic process” (MSB, h- H2O2, tBOOH) and “fatty acid catabolic process” (tBOOH, diamide and NaCl) for up-regulated genes under stress treatments indicated in parentheses (data not shown). Cross-stress adaptation experiments demonstrated that pre-treatments of the cultures with low concentrations of H2O2 or diamide decreased the growth inhibitory effects of MSB and pre-treatments with a low concentration of MSB decreased the growth inhibitory effect of NaCl in both the control and the ΔatfA strains (Fig. 3).Fig. 3


Core oxidative stress response in Aspergillus nidulans.

Emri T, Szarvas V, Orosz E, Antal K, Park H, Han KH, Yu JH, Pócsi I - BMC Genomics (2015)

Cross adaptations observed in the control and ΔatfA strains. The control (white columns) and ΔatfA (grey columns) strains were pre-cultured for 0.5 h in the presence of various stress initiating agents as indicated. Following pre-treatments, fungi were exposed to 0.18 mM MSB (Part a) or 1.0 M NaCl (Part b) in fresh culture media. All cultures were incubated for 18 h, and increases in the dry cell mass (DCM) values were determined, which are presented here as means ± S.D. values (n = 3). Untreated cultures were not subjected to stress treatments at all meanwhile control cultures were exposed to MSB and NaCl without stress pre-treatments. *Significant differences in comparison to control cultures calculated by Student’s t-test (p < 0.05, n = 3)
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4482186&req=5

Fig3: Cross adaptations observed in the control and ΔatfA strains. The control (white columns) and ΔatfA (grey columns) strains were pre-cultured for 0.5 h in the presence of various stress initiating agents as indicated. Following pre-treatments, fungi were exposed to 0.18 mM MSB (Part a) or 1.0 M NaCl (Part b) in fresh culture media. All cultures were incubated for 18 h, and increases in the dry cell mass (DCM) values were determined, which are presented here as means ± S.D. values (n = 3). Untreated cultures were not subjected to stress treatments at all meanwhile control cultures were exposed to MSB and NaCl without stress pre-treatments. *Significant differences in comparison to control cultures calculated by Student’s t-test (p < 0.05, n = 3)
Mentions: Although only few core stress response genes (Table 3) were found in both the control and the ΔatfA strains the stress responses still shared some common motives when the physiological functions of the up-regulated and down-regulated genes were compared. Among the significant shared GO terms “sterol metabolic process” (MSB, l-H2O2, h- H2O2, tBOOH and diamide) and “ribosome biogenesis” (MSB, h- H2O2, tBOOH, diamide and NaCl) were characteristic for down regulated gene, meanwhile “branched-chain amino acid biosynthetic process” (MSB, h- H2O2, tBOOH) and “fatty acid catabolic process” (tBOOH, diamide and NaCl) for up-regulated genes under stress treatments indicated in parentheses (data not shown). Cross-stress adaptation experiments demonstrated that pre-treatments of the cultures with low concentrations of H2O2 or diamide decreased the growth inhibitory effects of MSB and pre-treatments with a low concentration of MSB decreased the growth inhibitory effect of NaCl in both the control and the ΔatfA strains (Fig. 3).Fig. 3

Bottom Line: We also found that both oxidative and salt stresses induced expression of some secondary metabolite gene clusters and the deletion of atfA enhanced the stress responsiveness of additional clusters.Our data suggest that the observed co-regulations were most likely consequences of the overlapping physiological effects of the stressors and not of the existence of a general environmental stress response.Both stress inducible and stress repressive regulations of secondary metabolism seem to be frequent features in A. nidulans.

View Article: PubMed Central - PubMed

Affiliation: Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, P.O. Box 63, H-4032, Debrecen, Hungary. emri.tamas@science.unideb.hu.

ABSTRACT

Background: The b-Zip transcription factor AtfA plays a key role in regulating stress responses in the filamentous fungus Aspergillus nidulans. To identify the core regulons of AtfA, we examined genome-wide expression changes caused by various stresses in the presence/absence of AtfA using A. nidulans microarrays. We also intended to address the intriguing question regarding the existence of core environmental stress response in this important model eukaryote.

Results: Examination of the genome wide expression changes caused by five different oxidative stress conditions in wild type and the atfA mutant has identified a significant number of stereotypically regulated genes (Core Oxidative Stress Response genes). The deletion of atfA increased the oxidative stress sensitivity of A. nidulans and affected mRNA accumulation of several genes under both unstressed and stressed conditions. The numbers of genes under the AtfA control appear to be specific to a stress-type. We also found that both oxidative and salt stresses induced expression of some secondary metabolite gene clusters and the deletion of atfA enhanced the stress responsiveness of additional clusters. Moreover, certain clusters were down-regulated by the stresses tested.

Conclusion: Our data suggest that the observed co-regulations were most likely consequences of the overlapping physiological effects of the stressors and not of the existence of a general environmental stress response. The function of AtfA in governing various stress responses is much smaller than anticipated and/or other regulators may play a redundant or overlapping role with AtfA. Both stress inducible and stress repressive regulations of secondary metabolism seem to be frequent features in A. nidulans.

No MeSH data available.


Related in: MedlinePlus