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Hou L, Zhao M, Huang C, He Q, Zhang L, Zhang J. Alternative oxidase gene induced by nitric oxide is involved in the regulation of ROS and enhances the resistance of Pleurotus ostreatus to heat stress. Microb Cell Fact 2021; 20:137. [PMID: 34281563 PMCID: PMC8287771 DOI: 10.1186/s12934-021-01626-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 07/04/2021] [Indexed: 12/13/2022] Open
Abstract
Background In China, during the cultivation process of Pleurotus ostreatus, the yield and quality of fruiting bodies are easily affected by high temperatures in summer. Nitric oxide (NO) plays an important regulatory role in the response to abiotic stress, and previous studies have found that NO can induce alternative oxidase (aox) experssion in response to heat stress (HS) by regulating aconitase. However, the regulatory pathway of NO is complex, and the function and regulation of the aox gene in the response to HS remain unclear. Results In this study, we found that NO affected nicotinamide adenine dinucleotide (NADH) and adenosine triphosphate (ATP) levels, reduced hydrogen peroxide (H2O2) and superoxide anion (O2−) contents, and slowed O2− production. Further RNA-Seq results showed that NO regulated the oxidation-reduction process and oxidoreductase activity, affected the cellular respiration pathway and activated aox gene expression. The function of aox was determined by constructing overexpression (OE) and RNA interference (RNAi) strains. The results showed that the OE-aox strains exhibited obviously improved growth recovery after exposure to HS. During exposure to HS, the OE-aox strains exhibited reduced levels of NADH, the product of the tricarboxylic acid (TCA) cycle, and decreased synthesis of ATP, which reduced the production and accumulation of reactive oxygen species (ROS), whereas the RNAi-aox strains exhibited the opposite result. In addition, aox mediated the expression of antioxidant enzyme genes in the mycelia of P. ostreatus under HS through the retrograde signaling pathway. Conclusions This study shows that the expression of the aox gene in P. ostreatus mycelia can be induced by NO under HS, that it regulates the TCA cycle and cell respiration to reduce the production of ROS, and that it can mediate the retrograde signaling pathway involved in the mycelial response to HS. Graphical abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s12934-021-01626-y.
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Affiliation(s)
- Ludan Hou
- Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, 10081, Beijing, China.,Key Laboratory of Microbial Resources, Ministry of Agriculture and Rural Affairs, 10081, Beijing, China
| | - Mengran Zhao
- Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, 10081, Beijing, China.,Key Laboratory of Microbial Resources, Ministry of Agriculture and Rural Affairs, 10081, Beijing, China
| | - Chenyang Huang
- Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, 10081, Beijing, China.,Key Laboratory of Microbial Resources, Ministry of Agriculture and Rural Affairs, 10081, Beijing, China
| | - Qi He
- Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, 10081, Beijing, China.,Key Laboratory of Microbial Resources, Ministry of Agriculture and Rural Affairs, 10081, Beijing, China.,Jilin Agricultural University, 130118, Jilin, China
| | - Lijiao Zhang
- Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, 10081, Beijing, China.,Key Laboratory of Microbial Resources, Ministry of Agriculture and Rural Affairs, 10081, Beijing, China
| | - Jinxia Zhang
- Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, 10081, Beijing, China. .,Key Laboratory of Microbial Resources, Ministry of Agriculture and Rural Affairs, 10081, Beijing, China.
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Zhang J, Hao H, Liu H, Wang Q, Chen M, Feng Z, Chen H. Genetic and functional analysis of the Zn(II) 2Cys 6 transcription factor HADA-1 in Hypsizygus marmoreus. Appl Microbiol Biotechnol 2021; 105:2815-2829. [PMID: 33675375 DOI: 10.1007/s00253-021-11175-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 02/02/2021] [Accepted: 02/10/2021] [Indexed: 10/22/2022]
Abstract
Zn(II)2Cys6 transcription factors are critical for the reproductive growth and sexual development of fungi, but their roles in Basidiomycota remain unclear. In this study, the Hypsizygus marmoreus gene hada-1 was shown to encode a Zn(II)2Cys6 transcription factor, the growth rate of mycelia was decreased, hyphae were angulated, and fruiting body development was hindered in the hada-1-silenced strains. In addition, mitochondrial stability was lost, and the mitochondria morphologies changed from oval shaped to dumbbell or linear shaped in the silenced strains. Regarding mitochondrial instability, the mitochondrial complex II, III, and V activities and adenosine triphosphate content were significantly decreased. At the same time, the activities of the carbohydrate metabolism-related enzymes glucose-6-plosphatase, glucose dehydrogenase, and laccase were significantly decreased, which might have resulted in the reduction of carbon metabolism. Furthermore, hada-1 was shown to regulate the reactive oxygen species (ROS) level; compared with the wild-type (WT) strain, the silenced mycelia exhibited higher ROS contents and were more sensitive to oxidative stress. Taken together, these results indicate that, as a global regulator, hada-1 plays crucial roles in mycelial growth, fruiting body development, carbon metabolism, mitochondrial stability, and oxidative stress in the basidiomycete H. marmoreus. KEY POINTS: • Zn(II)2Cys6 transcription factor, mitochondrial stability, fruiting body development.
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Affiliation(s)
- Jinjing Zhang
- National Research Center for Edible Fungi Biotechnology and Engineering, Key Laboratory of Applied Mycological Resources and Utilization, Ministry of Agriculture; Shanghai Key Laboratory of Agricultural Genetics and Breeding, Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, No. 1000, Jinqi Road, Shanghai, 201403, China
| | - Haibo Hao
- National Research Center for Edible Fungi Biotechnology and Engineering, Key Laboratory of Applied Mycological Resources and Utilization, Ministry of Agriculture; Shanghai Key Laboratory of Agricultural Genetics and Breeding, Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, No. 1000, Jinqi Road, Shanghai, 201403, China
| | - Hong Liu
- National Research Center for Edible Fungi Biotechnology and Engineering, Key Laboratory of Applied Mycological Resources and Utilization, Ministry of Agriculture; Shanghai Key Laboratory of Agricultural Genetics and Breeding, Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, No. 1000, Jinqi Road, Shanghai, 201403, China
| | - Qian Wang
- National Research Center for Edible Fungi Biotechnology and Engineering, Key Laboratory of Applied Mycological Resources and Utilization, Ministry of Agriculture; Shanghai Key Laboratory of Agricultural Genetics and Breeding, Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, No. 1000, Jinqi Road, Shanghai, 201403, China
| | - Mingjie Chen
- National Research Center for Edible Fungi Biotechnology and Engineering, Key Laboratory of Applied Mycological Resources and Utilization, Ministry of Agriculture; Shanghai Key Laboratory of Agricultural Genetics and Breeding, Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, No. 1000, Jinqi Road, Shanghai, 201403, China
| | - Zhiyong Feng
- National Research Center for Edible Fungi Biotechnology and Engineering, Key Laboratory of Applied Mycological Resources and Utilization, Ministry of Agriculture; Shanghai Key Laboratory of Agricultural Genetics and Breeding, Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, No. 1000, Jinqi Road, Shanghai, 201403, China.,College of Life Science, Nanjing Agricultural University, No. 1, Weigang Road, Xuanwu District, Nanjing, 210095, China
| | - Hui Chen
- National Research Center for Edible Fungi Biotechnology and Engineering, Key Laboratory of Applied Mycological Resources and Utilization, Ministry of Agriculture; Shanghai Key Laboratory of Agricultural Genetics and Breeding, Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, No. 1000, Jinqi Road, Shanghai, 201403, China.
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3
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Characterization of Single Gene Deletion Mutants Affecting Alternative Oxidase Production in Neurospora crassa: Role of the yvh1 Gene. Microorganisms 2020; 8:microorganisms8081186. [PMID: 32759834 PMCID: PMC7463738 DOI: 10.3390/microorganisms8081186] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/29/2020] [Accepted: 07/31/2020] [Indexed: 01/21/2023] Open
Abstract
The Neurospora crassa AOD1 protein is a mitochondrial alternative oxidase that passes electrons directly from ubiquinol to oxygen. The enzyme is encoded by the nuclear aod-1 gene and is produced when the standard electron transport chain is inhibited. We previously identified eleven strains in the N. crassa single gene deletion library that were severely deficient in their ability to produce AOD1 when grown in the presence of chloramphenicol, an inhibitor of mitochondrial translation that is known to induce the enzyme. Three mutants affected previously characterized genes. In this report we examined the remaining mutants and found that the deficiency of AOD1 was due to secondary mutations in all but two of the strains. One of the authentic mutants contained a deletion of the yvh1 gene and was found to have a deficiency of aod-1 transcripts. The YVH1 protein localized to the nucleus and a post mitochondrial pellet from the cytoplasm. A zinc binding domain in the protein was required for rescue of the AOD1 deficiency. In other organisms YVH1 is required for ribosome assembly and mutants have multiple phenotypes. Lack of YVH1 in N. crassa likely also affects ribosome assembly leading to phenotypes that include altered regulation of AOD1 production.
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Bosnjak N, Smith KM, Asaria I, Lahola-Chomiak A, Kishore N, Todd AT, Freitag M, Nargang FE. Involvement of a G Protein Regulatory Circuit in Alternative Oxidase Production in Neurospora crassa. G3 (BETHESDA, MD.) 2019; 9:3453-3465. [PMID: 31444295 PMCID: PMC6778808 DOI: 10.1534/g3.119.400522] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 08/19/2019] [Indexed: 12/12/2022]
Abstract
The Neurospora crassa nuclear aod-1 gene encodes an alternative oxidase that functions in mitochondria. The enzyme provides a branch from the standard electron transport chain by transferring electrons directly from ubiquinol to oxygen. In standard laboratory strains, aod-1 is transcribed at very low levels under normal growth conditions. However, if the standard electron transport chain is disrupted, aod-1 mRNA expression is induced and the AOD1 protein is produced. We previously identified a strain of N. crassa, that produces high levels of aod-1 transcript under non-inducing conditions. Here we have crossed this strain to a standard lab strain and determined the genomic sequences of the parents and several progeny. Analysis of the sequence data and the levels of aod-1 mRNA in uninduced cultures revealed that a frameshift mutation in the flbA gene results in the high uninduced expression of aod-1 The flbA gene encodes a regulator of G protein signaling that decreases the activity of the Gα subunit of heterotrimeric G proteins. Our data suggest that strains with a functional flbA gene prevent uninduced expression of aod-1 by inactivating a G protein signaling pathway, and that this pathway is activated in cells grown under conditions that induce aod-1 Induced cells with a deletion of the gene encoding the Gα protein still have a partial increase in aod-1 mRNA levels, suggesting a second pathway for inducing transcription of the gene in N. crassa We also present evidence that a translational control mechanism prevents production of AOD1 protein in uninduced cultures.
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Affiliation(s)
- Natasa Bosnjak
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9 and
| | - Kristina M Smith
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331-4003
| | - Iman Asaria
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9 and
| | - Adrian Lahola-Chomiak
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9 and
| | - Nishka Kishore
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9 and
| | - Andrea T Todd
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9 and
| | - Michael Freitag
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331-4003
| | - Frank E Nargang
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9 and
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5
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Sellem CH, Humbert A, Sainsard-Chanet A. Mutations in the phosphatase domain of the 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase result in the transcriptional activation of the alternative oxidase and gluconeogenic pathways in Podospora anserina. Fungal Genet Biol 2019; 130:1-10. [PMID: 30980907 DOI: 10.1016/j.fgb.2019.04.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 03/01/2019] [Accepted: 04/03/2019] [Indexed: 11/29/2022]
Abstract
By screening suppressors of a respiratory mutant lacking a functional cytochrome pathway in the filamentous fungus Podospora anserina, we isolated a mutation located in the phosphatase domain of the bi-functional enzyme 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase (PFK-2/FBPase-2). We show that the inactivation of the phosphatase but not of the kinase domain is responsible for the suppressor effect that results from the activation of the RSEs transcription factors that control expression of AOX, an alternative oxidase able to bypass the mitochondria cytochrome pathway of respiration. Remarkably, activation of the RSEs also stimulates the expression of the gluconeogenic enzymes, fructose-1,6 bi-phosphatase (FBPase-1) and phosphoenolpyruvate carboxykinase (PCK-1). We thus reveal in P. anserina an apparently paradoxical situation where the inactivation of the phosphatase domain of PFK-2/FBPase-2, supposed to stimulate glycolysis, is correlated with the transcriptional induction of the gluconeogenic enzymes. Phylogenic analysis revealed the presence of multiple presumed PFK-2/FBPase-2 isoforms in all the species of tested Ascomycetes.
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Affiliation(s)
- Carole H Sellem
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France.
| | - Adeline Humbert
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France
| | - Annie Sainsard-Chanet
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France
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6
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Liu M, Guo X. A novel and stress adaptive alternative oxidase derived from alternative splicing of duplicated exon in oyster Crassostrea virginica. Sci Rep 2017; 7:10785. [PMID: 28883650 PMCID: PMC5589949 DOI: 10.1038/s41598-017-10976-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 08/17/2017] [Indexed: 12/25/2022] Open
Abstract
Alternative oxidase (AOX) is a mitochondrial inner-membrane oxidase that accepts electrons directly from ubiquinol and reduces oxygen to water without involving cytochrome-linked electron transport chain. It is highly conserved in many non-vertebrate taxa and may protect cells against hypoxia and oxidative stress. We identified two AOX mRNAs in eastern oyster Crassostrea virginica, CvAOXA and CvAOXB, which differ by 170 bp but encode AOXs of the same size. Sequence analyses indicate that CvAOX has 10 exons with a tandem duplication of exon 10, and 3' alternative splicing using either the first or second exon 10 produces the two variants CvAOXB or CvAOXA, respectively. The second exon 10 in CvAOXA is more conserved across taxa, while the first exon 10 in CvAOXB contains novel mutations surrounding key functional sites. Both variants are expressed in all organs with the expression of CvAOXA higher than that of CvAOXB under normal condition. Under stress by air exposure, CvAOXB showed significantly higher expression than CvAOXA and became the dominant variant. This is the first case of alternative splicing of duplicated exon in a mollusc that produces a novel variant adaptive to stress, highlighting genome's versatility in generating diversity and phenotypic plasticity.
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Affiliation(s)
- Ming Liu
- Haskin Shellfish Research Laboratory, Department of Marine and Coastal Sciences, Rutgers University, 6959 Miller Avenue, Port Norris, NJ, 08349, USA
| | - Ximing Guo
- Haskin Shellfish Research Laboratory, Department of Marine and Coastal Sciences, Rutgers University, 6959 Miller Avenue, Port Norris, NJ, 08349, USA.
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7
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Qi Z, Smith KM, Bredeweg EL, Bosnjak N, Freitag M, Nargang FE. Alternative Oxidase Transcription Factors AOD2 and AOD5 of Neurospora crassa Control the Expression of Genes Involved in Energy Production and Metabolism. G3 (BETHESDA, MD.) 2017; 7:449-466. [PMID: 27986792 PMCID: PMC5295593 DOI: 10.1534/g3.116.035402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Accepted: 11/22/2016] [Indexed: 01/16/2023]
Abstract
In Neurospora crassa, blocking the function of the standard mitochondrial electron transport chain results in the induction of an alternative oxidase (AOX). AOX transfers electrons directly from ubiquinol to molecular oxygen. AOX serves as a model of retrograde regulation since it is encoded by a nuclear gene that is regulated in response to signals from mitochondria. The N. crassa transcription factors AOD2 and AOD5 are necessary for the expression of the AOX gene. To gain insight into the mechanism by which these factors function, and to determine if they have roles in the expression of additional genes in N. crassa, we constructed strains expressing only tagged versions of the proteins. Cell fractionation experiments showed that both proteins are localized to the nucleus under both AOX inducing and noninducing conditions. Furthermore, chromatin immunoprecipitation and high throughput sequencing (ChIP-seq) analysis revealed that the proteins are bound to the promoter region of the AOX gene under both conditions. ChIP-seq also showed that the transcription factors bind to the upstream regions of a number of genes that are involved in energy production and metabolism. Dependence on AOD2 and AOD5 for the expression of several of these genes was verified by quantitative PCR. The majority of ChIP-seq peaks observed were enriched for both AOD2 and AOD5. However, we also observed occasional sites where one factor appeared to bind preferentially. The most striking of these was a conserved sequence that bound large amounts of AOD2 but little AOD5. This sequence was found within a 310 bp repeat unit that occurs at several locations in the genome.
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Affiliation(s)
- Zhigang Qi
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
| | - Kristina M Smith
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331-4003
| | - Erin L Bredeweg
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331-4003
| | - Natasa Bosnjak
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
| | - Michael Freitag
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331-4003
| | - Frank E Nargang
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
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Rogov AG, Sukhanova EI, Uralskaya LA, Aliverdieva DA, Zvyagilskaya RA. Alternative oxidase: distribution, induction, properties, structure, regulation, and functions. BIOCHEMISTRY (MOSCOW) 2015; 79:1615-34. [PMID: 25749168 DOI: 10.1134/s0006297914130112] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The respiratory chain in the majority of organisms with aerobic type metabolism features the concomitant existence of the phosphorylating cytochrome pathway and the cyanide- and antimycin A-insensitive oxidative route comprising a so-called alternative oxidase (AOX) as a terminal oxidase. In this review, the history of AOX discovery is described. Considerable evidence is presented that AOX occurs widely in organisms at various levels of organization and is not confined to the plant kingdom. This enzyme has not been found only in Archaea, mammals, some yeasts and protists. Bioinformatics research revealed the sequences characteristic of AOX in representatives of various taxonomic groups. Based on multiple alignments of these sequences, a phylogenetic tree was constructed to infer their possible evolution. The ways of AOX activation, as well as regulatory interactions between AOX and the main respiratory chain are described. Data are summarized concerning the properties of AOX and the AOX-encoding genes whose expression is either constitutive or induced by various factors. Information is presented on the structure of AOX, its active center, and the ubiquinone-binding site. The principal functions of AOX are analyzed, including the cases of cell survival, optimization of respiratory metabolism, protection against excess of reactive oxygen species, and adaptation to variable nutrition sources and to biotic and abiotic stress factors. It is emphasized that different AOX functions complement each other in many instances and are not mutually exclusive. Examples are given to demonstrate that AOX is an important tool to overcome the adverse aftereffects of restricted activity of the main respiratory chain in cells and whole animals. This is the first comprehensive review on alternative oxidases of various organisms ranging from yeasts and protists to vascular plants.
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Affiliation(s)
- A G Rogov
- Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, 119071, Russia.
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Genetic and functional investigation of Zn(2)Cys(6) transcription factors RSE2 and RSE3 in Podospora anserina. EUKARYOTIC CELL 2013; 13:53-65. [PMID: 24186951 DOI: 10.1128/ec.00172-13] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In Podospora anserina, the two zinc cluster proteins RSE2 and RSE3 are essential for the expression of the gene encoding the alternative oxidase (aox) when the mitochondrial electron transport chain is impaired. In parallel, they activated the expression of gluconeogenic genes encoding phosphoenolpyruvate carboxykinase (pck) and fructose-1,6-biphosphatase (fbp). Orthologues of these transcription factors are present in a wide range of filamentous fungi, and no other role than the regulation of these three genes has been evidenced so far. In order to better understand the function and the organization of RSE2 and RSE3, we conducted a saturated genetic screen based on the constitutive expression of the aox gene. We identified 10 independent mutations in 9 positions in rse2 and 11 mutations in 5 positions in rse3. Deletions were generated at some of these positions and the effects analyzed. This analysis suggests the presence of central regulatory domains and a C-terminal activation domain in both proteins. Microarray analysis revealed 598 genes that were differentially expressed in the strains containing gain- or loss-of-function mutations in rse2 or rse3. It showed that in addition to aox, fbp, and pck, RSE2 and RSE3 regulate the expression of genes encoding the alternative NADH dehydrogenase, a Zn2Cys6 transcription factor, a flavohemoglobin, and various hydrolases. As a complement to expression data, a metabolome profiling approach revealed that both an rse2 gain-of-function mutation and growth on antimycin result in similar metabolic alterations in amino acids, fatty acids, and α-ketoglutarate pools.
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Nargang FE, Adames K, Rüb C, Cheung S, Easton N, Nargang CE, Chae MS. Identification of genes required for alternative oxidase production in the Neurospora crassa gene knockout library. G3 (BETHESDA, MD.) 2012; 2:1345-56. [PMID: 23173086 PMCID: PMC3484665 DOI: 10.1534/g3.112.004218] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2012] [Accepted: 09/04/2012] [Indexed: 01/22/2023]
Abstract
The alternative oxidase (AOX) of Neurospora crassa transfers electrons from ubiquinol to oxygen. The enzyme is not expressed under normal conditions. However, when the function of the standard electron transport chain is compromised, AOX is induced, providing cells with a means to continue respiration and growth. Induction of the enzyme represents a form of retrograde regulation because AOX is encoded by a nuclear gene that responds to signals produced from inefficiently functioning mitochondria. To identify genes required for AOX expression, we have screened the N. crassa gene knockout library for strains that are unable to grow in the presence of antimycin A, an inhibitor of complex III of the standard electron transport chain. From the 7800 strains containing knockouts of different genes, we identified 62 strains that have reduced levels of AOX when grown under conditions known to induce the enzyme. Some strains have virtually no AOX, whereas others have only a slight reduction of the protein. A broad range of seemingly unrelated functions are represented in the knockouts. For example, we identified transcription factors, kinases, the mitochondrial import receptor Tom70, three subunits of the COP9 signalosome, a monothiol glutaredoxin, and several hypothetical proteins as being required for wild-type levels of AOX production. Our results suggest that defects in many signaling or metabolic pathways have a negative effect on AOX expression and imply that complex systems control production of the enzyme.
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Affiliation(s)
- Frank E Nargang
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada.
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11
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Chae MS, Nargang FE. Investigation of regulatory factors required for alternative oxidase production in Neurospora crassa. PHYSIOLOGIA PLANTARUM 2009; 137:407-418. [PMID: 19493307 DOI: 10.1111/j.1399-3054.2009.01239.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Alternative oxidase (AOX) has been found in a large number of filamentous fungi and yeasts with the notable exceptions of Saccharomyces cerevisiae and Schizosaccharomyces pombe. In virtually all of these fungi, AOX is induced by stresses on the cell that compromise the efficiency of the standard mitochondrial electron transport chain. As AOX is encoded in the nucleus and the signals that induce its expression originate in mitochondria, induction of the enzyme provides a classic example of retrograde regulation where signals from mitochondria influence the expression of nuclear genes. We have previously isolated mutants in Neurospora crassa that are incapable of inducing AOX. The genes affected in two of these mutants, aod-2 and aod-5, encode zinc cluster transcription factors that act to control expression of the AOX by binding to an alternative oxidase induction motif (AIM) found in the promoter of the AOX structural gene. We have now used pull-down assays and size-exclusion chromatography to demonstrate that the AOD2 and AOD5 proteins physically interact in vitro. In addition, we have shown that a homolog of the RTG2 protein, which is part of a classic retrograde signaling pathway in S. cerevisiae, is not required for AOX regulation in N. crassa.
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Affiliation(s)
- Michael S Chae
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G2E9
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12
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Mutations in two zinc-cluster proteins activate alternative respiratory and gluconeogenic pathways and restore senescence in long-lived respiratory mutants of Podospora anserina. Genetics 2009; 182:69-78. [PMID: 19255367 DOI: 10.1534/genetics.109.100834] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In Podospora anserina, inactivation of the respiratory chain results in a spectacular life-span extension. This inactivation is accompanied by the induction of the alternative oxidase. Although the functional value of this response is evident, the mechanism behind it is far from understood. By screening suppressors able to reduce the life-span extension of cytochrome-deficient mutants, we identified mutations in two zinc-cluster proteins, RSE2 and RSE3, which are conserved in other ascomycetes. These mutations led to the overexpression of the genes encoding the alternative oxidase and the gluconeogenic enzymes, fructose-1, 6 biphosphatase, and pyruvate carboxykinase. Both RSE2 and RSE3 are required for the expression of these genes. We also show that, even in the absence of a respiratory deficiency, the wild-type RSE2 and RSE3 transcription factors are involved in life-span control and their inactivation retards aging. These data are discussed with respect to aging, the regulation of the alternative oxidase, and carbon metabolism.
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13
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McDonald AE. Alternative oxidase: an inter-kingdom perspective on the function and regulation of this broadly distributed 'cyanide-resistant' terminal oxidase. FUNCTIONAL PLANT BIOLOGY : FPB 2008; 35:535-552. [PMID: 32688810 DOI: 10.1071/fp08025] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2008] [Accepted: 07/11/2008] [Indexed: 06/11/2023]
Abstract
Alternative oxidase (AOX) is a terminal quinol oxidase located in the respiratory electron transport chain that catalyses the oxidation of quinol and the reduction of oxygen to water. However, unlike the cytochrome c oxidase respiratory pathway, the AOX pathway moves fewer protons across the inner mitochondrial membrane to generate a proton motive force that can be used to synthesise ATP. The energy passed to AOX is dissipated as heat. This appears to be very wasteful from an energetic perspective and it is likely that AOX fulfils some physiological function(s) that makes up for its apparent energetic shortcomings. An examination of the known taxonomic distribution of AOX and the specific organisms in which AOX has been studied has been used to explore themes pertaining to AOX function and regulation. A comparative approach was used to examine AOX function as it relates to the biochemical function of the enzyme as a quinol oxidase and associated topics, such as enzyme structure, catalysis and transcriptional expression and post-translational regulation. Hypotheses that have been put forward about the physiological function(s) of AOX were explored in light of some recent discoveries made with regard to species that contain AOX. Fruitful areas of research for the AOX community in the future have been highlighted.
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Affiliation(s)
- Allison E McDonald
- Department of Biology, The University of Western Ontario, Biological and Geological Sciences Building, London, Ontario N6A 5B7, Canada. Email
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Two zinc-cluster transcription factors control induction of alternative oxidase in Neurospora crassa. Genetics 2008; 177:1997-2006. [PMID: 18073419 DOI: 10.1534/genetics.107.078212] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The alternative oxidase transfers electrons from ubiquinol to molecular oxygen, providing a mechanism for bypassing the later steps of the standard cytochrome-mediated electron transport chain. The enzyme is found in an array of organisms and in many cases is known to be produced in response to perturbations of the standard chain. Alternative oxidase is encoded in the nucleus but functions in the inner mitochondrial membrane. This implies the existence of a retrograde regulation pathway for communicating from the mitochondrion to the nucleus to induce alternative oxidase expression. Previous studies on alternative oxidase in fungi and plants have shown that a number of genes are required for expression of the enzyme, but the identity of these genes has remained elusive. By gene rescue we have now shown that the aod-2 and aod-5 genes of Neurospora crassa encode transcription factors of the zinc-cluster family. Electrophoretic mobility shift assays show that the DNA-binding domains of the AOD2 and AOD5 proteins act in tandem to bind a sequence element in the alternative oxidase gene promoter that is required for expression. Both proteins contain potential PAS domains near their C terminus, which are found primarily in proteins involved in signal transduction.
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