1
|
Weaver RJ, McDonald AE. Mitochondrial alternative oxidase across the tree of life: Presence, absence, and putative cases of lateral gene transfer. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:149003. [PMID: 37557975 DOI: 10.1016/j.bbabio.2023.149003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 07/27/2023] [Accepted: 08/02/2023] [Indexed: 08/11/2023]
Abstract
The alternative oxidase (AOX) is a terminal oxidase in the electron transport system that plays a role in mitochondrial bioenergetics. The past 20 years of research shows AOX has a wide yet patchy distribution across the tree of life. AOX has been suggested to have a role in stress tolerance, growth, and development in plants, but less is known about its function in other groups, including animals. In this study, we analyzed the taxonomic distribution of AOX across >2800 species representatives from prokaryotes and eukaryotes and developed a standardized workflow for finding and verifying the authenticity of AOX sequences. We found that AOX is limited to proteobacteria among prokaryotes, but is widely distributed in eukaryotes, with the highest prevalence in plants, fungi, and protists. AOX is present in many invertebrates, but is absent in others including most arthropods, and is absent from vertebrates. We found aberrant AOX sequences associated with some animal groups. Some of these aberrant AOXs were contaminants, but we also found putative cases of lateral gene transfer of AOX from fungi and protists to nematodes, springtails, fungus gnats, and rotifers. Our findings provide a robust and detailed analysis of the distribution of AOX and a method for identifying and verifying putative AOX sequences, which will be useful as more sequence data becomes available on public repositories.
Collapse
Affiliation(s)
- Ryan J Weaver
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, USA.
| | - Allison E McDonald
- Department of Biology, Wilfrid Laurier University, Waterloo, Ontario, Canada.
| |
Collapse
|
2
|
Santana‐Sánchez A, Nikkanen L, Werner E, Tóth G, Ermakova M, Kosourov S, Walter J, He M, Aro E, Allahverdiyeva Y. Flv3A facilitates O 2 photoreduction and affects H 2 photoproduction independently of Flv1A in diazotrophic Anabaena filaments. THE NEW PHYTOLOGIST 2023; 237:126-139. [PMID: 36128660 PMCID: PMC10092803 DOI: 10.1111/nph.18506] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Accepted: 09/10/2022] [Indexed: 05/23/2023]
Abstract
The model heterocyst-forming filamentous cyanobacterium Anabaena sp. PCC 7120 (Anabaena) is a typical example of a multicellular organism capable of simultaneously performing oxygenic photosynthesis in vegetative cells and O2 -sensitive N2 -fixation inside heterocysts. The flavodiiron proteins have been shown to participate in photoprotection of photosynthesis by driving excess electrons to O2 (a Mehler-like reaction). Here, we performed a phenotypic and biophysical characterization of Anabaena mutants impaired in vegetative-specific Flv1A and Flv3A in order to address their physiological relevance in the bioenergetic processes occurring in diazotrophic Anabaena under variable CO2 conditions. We demonstrate that both Flv1A and Flv3A are required for proper induction of the Mehler-like reaction upon a sudden increase in light intensity, which is likely important for the activation of carbon-concentrating mechanisms and CO2 fixation. Under ambient CO2 diazotrophic conditions, Flv3A is responsible for moderate O2 photoreduction, independently of Flv1A, but only in the presence of Flv2 and Flv4. Strikingly, the lack of Flv3A resulted in strong downregulation of the heterocyst-specific uptake hydrogenase, which led to enhanced H2 photoproduction under both oxic and micro-oxic conditions. These results reveal a novel regulatory network between the Mehler-like reaction and the diazotrophic metabolism, which is of great interest for future biotechnological applications.
Collapse
Affiliation(s)
- Anita Santana‐Sánchez
- Molecular Plant Biology, Department of Life TechnologiesUniversity of TurkuTurkuFI‐20014Finland
| | - Lauri Nikkanen
- Molecular Plant Biology, Department of Life TechnologiesUniversity of TurkuTurkuFI‐20014Finland
| | - Elisa Werner
- Molecular Plant Biology, Department of Life TechnologiesUniversity of TurkuTurkuFI‐20014Finland
| | - Gábor Tóth
- Molecular Plant Biology, Department of Life TechnologiesUniversity of TurkuTurkuFI‐20014Finland
| | - Maria Ermakova
- Molecular Plant Biology, Department of Life TechnologiesUniversity of TurkuTurkuFI‐20014Finland
| | - Sergey Kosourov
- Molecular Plant Biology, Department of Life TechnologiesUniversity of TurkuTurkuFI‐20014Finland
| | - Julia Walter
- Molecular Plant Biology, Department of Life TechnologiesUniversity of TurkuTurkuFI‐20014Finland
| | - Meilin He
- Molecular Plant Biology, Department of Life TechnologiesUniversity of TurkuTurkuFI‐20014Finland
| | - Eva‐Mari Aro
- Molecular Plant Biology, Department of Life TechnologiesUniversity of TurkuTurkuFI‐20014Finland
| | - Yagut Allahverdiyeva
- Molecular Plant Biology, Department of Life TechnologiesUniversity of TurkuTurkuFI‐20014Finland
| |
Collapse
|
3
|
Dunn AK. Alternative oxidase in bacteria. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148929. [PMID: 36265564 DOI: 10.1016/j.bbabio.2022.148929] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 09/20/2022] [Accepted: 10/12/2022] [Indexed: 11/06/2022]
Abstract
While alternative oxidase (AOX) was discovered in bacteria in 2003, the expression, function, and evolutionary history of this protein in these important organisms is largely unexplored. To date, expression and functional analysis is limited to studies in the Proteobacteria Novosphingobium aromaticivorans and Vibrio fischeri, where AOX likely plays roles in maintenance of cellular energy homeostasis and supporting responses to cellular stress. This review describes the history of the study of AOX in bacteria, details current knowledge of the predicted biochemical and structural characteristics, distribution, and function of bacterial AOX, and highlights interesting areas for the future study of AOX in bacteria.
Collapse
Affiliation(s)
- Anne K Dunn
- Department of Microbiology and Plant Biology, University of Oklahoma, 770 Van Vleet Oval, Norman, OK 73019, USA.
| |
Collapse
|
4
|
Rog I, Chaturvedi AK, Tiwari V, Danon A. Low light-regulated intramolecular disulfide fine-tunes the role of PTOX in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 109:585-597. [PMID: 34767654 DOI: 10.1111/tpj.15579] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 11/01/2021] [Accepted: 11/08/2021] [Indexed: 06/13/2023]
Abstract
Disulfide-based regulation links the activity of numerous chloroplast proteins with photosynthesis-derived redox signals. The plastid terminal oxidase (PTOX) is a thylakoid-bound plastoquinol oxidase that has been implicated in multiple roles in the light and in the dark, which could require different levels of PTOX activity. Here we show that Arabidopsis PTOX contains a conserved C-terminus domain (CTD) with cysteines that evolved progressively following the colonization of the land by plants. Furthermore, the CTD contains a regulatory disulfide that is in the oxidized state in the dark and is rapidly reduced, within 5 min, in low light intensity (1-5 µE m-2 sec-1 ). The reduced PTOX form in the light was reoxidized within 15 min after transition to the dark. Mutation of the cysteines in the CTD prevented the formation of the oxidized form. This resulted in higher levels of reduced plastoquinone when measured at transition to the onset of low light. This is consistent with the reduced state of PTOX exhibiting diminished PTOX oxidase activity under conditions of limiting PQH2 substrate. Our findings suggest that AtPTOX-CTD evolved to provide light-dependent regulation of PTOX activity for the adaptation of plants to terrestrial conditions.
Collapse
Affiliation(s)
- Ido Rog
- Department of Plant & Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Amit Kumar Chaturvedi
- Department of Plant & Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Vivekanand Tiwari
- Department of Plant & Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Avihai Danon
- Department of Plant & Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
| |
Collapse
|
5
|
Arnholdt-Schmitt B, Mohanapriya G, Bharadwaj R, Noceda C, Macedo ES, Sathishkumar R, Gupta KJ, Sircar D, Kumar SR, Srivastava S, Adholeya A, Thiers KL, Aziz S, Velada I, Oliveira M, Quaresma P, Achra A, Gupta N, Kumar A, Costa JH. From Plant Survival Under Severe Stress to Anti-Viral Human Defense - A Perspective That Calls for Common Efforts. Front Immunol 2021; 12:673723. [PMID: 34211468 PMCID: PMC8240590 DOI: 10.3389/fimmu.2021.673723] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 05/13/2021] [Indexed: 12/11/2022] Open
Abstract
Reprogramming of primary virus-infected cells is the critical step that turns viral attacks harmful to humans by initiating super-spreading at cell, organism and population levels. To develop early anti-viral therapies and proactive administration, it is important to understand the very first steps of this process. Plant somatic embryogenesis (SE) is the earliest and most studied model for de novo programming upon severe stress that, in contrast to virus attacks, promotes individual cell and organism survival. We argued that transcript level profiles of target genes established from in vitro SE induction as reference compared to virus-induced profiles can identify differential virus traits that link to harmful reprogramming. To validate this hypothesis, we selected a standard set of genes named 'ReprogVirus'. This approach was recently applied and published. It resulted in identifying 'CoV-MAC-TED', a complex trait that is promising to support combating SARS-CoV-2-induced cell reprogramming in primary infected nose and mouth cells. In this perspective, we aim to explain the rationale of our scientific approach. We are highlighting relevant background knowledge on SE, emphasize the role of alternative oxidase in plant reprogramming and resilience as a learning tool for designing human virus-defense strategies and, present the list of selected genes. As an outlook, we announce wider data collection in a 'ReprogVirus Platform' to support anti-viral strategy design through common efforts.
Collapse
Affiliation(s)
- Birgit Arnholdt-Schmitt
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Functional Genomics and Bioinformatics Group, Department of Biochemistry and Molecular Biology, Federal University of Ceará, Fortaleza, Brazil
| | - Gunasekaran Mohanapriya
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Plant Genetic Engineering Laboratory, Department of Biotechnology, Bharathiar University, Coimbatore, India
| | - Revuru Bharadwaj
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Plant Genetic Engineering Laboratory, Department of Biotechnology, Bharathiar University, Coimbatore, India
| | - Carlos Noceda
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Cell and Molecular Biotechnology of Plants (BIOCEMP)/Industrial Biotechnology and Bioproducts, Departamento de Ciencias de la Vida y de la Agricultura, Universidad de las Fuerzas Armadas-ESPE, Sangolquí, Ecuador
| | - Elisete Santos Macedo
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
| | - Ramalingam Sathishkumar
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Plant Genetic Engineering Laboratory, Department of Biotechnology, Bharathiar University, Coimbatore, India
| | - Kapuganti Jagadis Gupta
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, India
| | - Debabrata Sircar
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Department of Biotechnology, Indian Institute of Technology, Roorkee, Uttarakhand, India
| | - Sarma Rajeev Kumar
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Plant Genetic Engineering Laboratory, Department of Biotechnology, Bharathiar University, Coimbatore, India
| | - Shivani Srivastava
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Centre for Mycorrhizal Research, Sustainable Agriculture Division, The Energy and Resources Institute (TERI), TERI Gram, Gual Pahari, Gurugram, India
| | - Alok Adholeya
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Centre for Mycorrhizal Research, Sustainable Agriculture Division, The Energy and Resources Institute (TERI), TERI Gram, Gual Pahari, Gurugram, India
| | - KarineLeitão Lima Thiers
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Functional Genomics and Bioinformatics Group, Department of Biochemistry and Molecular Biology, Federal University of Ceará, Fortaleza, Brazil
| | - Shahid Aziz
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Functional Genomics and Bioinformatics Group, Department of Biochemistry and Molecular Biology, Federal University of Ceará, Fortaleza, Brazil
| | - Isabel Velada
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- MED—Mediterranean Institute for Agriculture, Environment and Development, Instituto de Investigação e Formação Avançada, Universidade de Évora, Évora, Portugal
| | - Manuela Oliveira
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Department of Mathematics and CIMA - Center for Research on Mathematics and its Applications, Universidade de Évora, Évora, Portugal
| | - Paulo Quaresma
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- NOVA LINCS – Laboratory for Informatics and Computer Science, University of Évora, Évora, Portugal
| | - Arvind Achra
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Department of Microbiology, Atal Bihari Vajpayee Institute of Medical Sciences & Dr Ram Manohar Lohia Hospital, New Delhi, India
| | - Nidhi Gupta
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
| | - Ashwani Kumar
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Hargovind Khorana Chair, Jayoti Vidyapeeth Womens University, Jaipur, India
| | - José Hélio Costa
- Non-Institutional Competence Focus (NICFocus) ‘Functional Cell Reprogramming and Organism Plasticity’ (FunCROP), Coordinated from Foros de Vale de Figueira, Alentejo, Portugal
- Functional Genomics and Bioinformatics Group, Department of Biochemistry and Molecular Biology, Federal University of Ceará, Fortaleza, Brazil
| |
Collapse
|
6
|
Messant M, Shimakawa G, Perreau F, Miyake C, Krieger-Liszkay A. Evolutive differentiation between alga- and plant-type plastid terminal oxidase: Study of plastid terminal oxidase PTOX isoforms in Marchantia polymorpha. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1862:148309. [PMID: 32956677 DOI: 10.1016/j.bbabio.2020.148309] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 09/02/2020] [Accepted: 09/14/2020] [Indexed: 10/23/2022]
Abstract
The liverwort Marchantia polymorpha contains two isoforms of the plastid terminal oxidase (PTOX), an enzyme that catalyzes the reduction of oxygen to water using plastoquinol as substrate. Phylogenetic analyses showed that one isoform, here called MpPTOXa, is closely related to isoforms occurring in plants and some algae, while the other isoform, here called MpPTOXb, is closely related to the two isoforms occurring in Chlamydomonas reinhardtii. Mutants of each isoform were created in Marchantia polymorpha using CRISPR/Cas9 technology. While no obvious phenotype was found for these mutants, chlorophyll fluorescence analyses demonstrated that the plastoquinone pool was in a higher reduction state in both mutants. This was visible at the level of fluorescence measured in dark-adapted material and by post illumination fluorescence rise. These results suggest that both isoforms have a redundant function. However, when P700 oxidation and re-reduction was studied, differences between these two isoforms were observed. Furthermore, the mutant affected in MpPTOXb showed a slight alteration in the pigment composition, a higher non-photochemical quenching and a slightly lower electron transport rate through photosystem II. These differences may be explained either by differences in the enzymatic activities or by different activities attributed to preferential involvement of the two PTOX isoforms to either linear or cyclic electron flow.
Collapse
Affiliation(s)
- Marine Messant
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Ginga Shimakawa
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - François Perreau
- Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, 78000 Versailles, France
| | - Chikahiro Miyake
- Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
| | - Anja Krieger-Liszkay
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France.
| |
Collapse
|
7
|
Weaver RJ. Hypothesized Evolutionary Consequences of the Alternative Oxidase (AOX) in Animal Mitochondria. Integr Comp Biol 2020; 59:994-1004. [PMID: 30912813 DOI: 10.1093/icb/icz015] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The environment in which eukaryotes first evolved was drastically different from what they experience today, and one of the key limiting factors was the availability of oxygen for mitochondrial respiration. During the transition to a fully oxygenated Earth, other compounds such as sulfide posed a considerable constraint on using mitochondrial aerobic respiration for energy production. The ancestors of animals, and those that first evolved from the simpler eukaryotes have mitochondrial respiratory components that are absent from later-evolving animals. Specifically, mitochondria of most basal metazoans have a sulfide-resistant alternative oxidase (AOX), which provides a secondary oxidative pathway to the classical cytochrome pathway. In this essay, I argue that because of its resistance to sulfide, AOX respiration was critical to the evolution of animals by enabling oxidative metabolism under otherwise inhibitory conditions. I hypothesize that AOX allowed for metabolic flexibility during the stochastic oxygen environment of early Earth which shaped the evolution of basal metazoans. I briefly describe the known functions of AOX, with a particular focus on the decreased production of reactive oxygen species (ROS) during stress conditions. Then, I propose three evolutionary consequences of AOX-mediated protection from ROS observed in basal metazoans: 1) adaptation to stressful environments, 2) the persistence of facultative sexual reproduction, and 3) decreased mitochondrial DNA mutation rates. Recognizing the diversity of mitochondrial respiratory systems present in animals may help resolve the mechanisms involved in major evolutionary processes such as adaptation and speciation.
Collapse
Affiliation(s)
- Ryan J Weaver
- Department of Biological Sciences, Auburn University, 331 Funchess Hall, Auburn, AL 36849, USA
| |
Collapse
|
8
|
Raven JA, Beardall J, Quigg A. Light-Driven Oxygen Consumption in the Water-Water Cycles and Photorespiration, and Light Stimulated Mitochondrial Respiration. PHOTOSYNTHESIS IN ALGAE: BIOCHEMICAL AND PHYSIOLOGICAL MECHANISMS 2020. [DOI: 10.1007/978-3-030-33397-3_8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
|
9
|
Alternative Oxidase Activity Reduces Stress in Vibrio fischeri Cells Exposed to Nitric Oxide. J Bacteriol 2018; 200:JB.00797-17. [PMID: 29760206 DOI: 10.1128/jb.00797-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Accepted: 05/07/2018] [Indexed: 11/20/2022] Open
Abstract
Alternative oxidase (Aox) is a non-energy-conserving respiratory oxidase found in certain eukaryotes and bacteria, whose role in physiology is not entirely clear. Using the genetically tractable bacterium Vibrio fischeri as a model organism, I have identified a role for Aox to reduce levels of stress in cells exposed to oxygen and nitric oxide (NO). In V. fischeri lacking the NO-detoxifying enzyme flavohemoglobin (Hmp), deletion of aox in cells grown in the presence of oxygen and NO results in alterations to the transcriptome that include increases in transcripts mapping to stress-related genes. Using fluorescence-based reporters, I identified corresponding increases in intracellular reactive oxygen species and decreases in membrane integrity in cells lacking aox Under these growth conditions, activity of Aox is linked to a decrease in NADH levels, indicating coupling of Aox activity with NADH dehydrogenase activity. Taken together, these results suggest that Aox functions to indirectly limit production of ferrous iron and damaging hydroxyl radicals, effectively reducing cellular stress during NO exposure.IMPORTANCE Unlike typical respiratory oxidases, alternative oxidase (Aox) does not directly contribute to energy conservation, and its activity would presumably reduce the efficiency of respiration and associated ATP production. Aox has been identified in certain bacteria, a majority of which are marine associated. The presence of Aox in these bacteria poses the interesting question of how Aox function benefits bacterial growth and survival in the ocean. Using the genetically tractable marine bacterium Vibrio fischeri, I have identified a role for Aox in reduction of stress under conditions where electron flux through the aerobic respiratory pathway is inhibited. These results suggest that Aox activity could positively impact longer-term bacterial fitness and survival under stressful environmental conditions.
Collapse
|
10
|
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.
Collapse
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
| |
Collapse
|
11
|
Wang D, Fu A. The Plastid Terminal Oxidase is a Key Factor Balancing the Redox State of Thylakoid Membrane. Enzymes 2016; 40:143-171. [PMID: 27776780 DOI: 10.1016/bs.enz.2016.09.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Abstract
Mitochondria possess oxygen-consuming respiratory electron transfer chains (RETCs), and the oxygen-evolving photosynthetic electron transfer chain (PETC) resides in chloroplasts. Evolutionarily mitochondria and chloroplasts are derived from ancient α-proteobacteria and cyanobacteria, respectively. However, cyanobacteria harbor both RETC and PETC on their thylakoid membranes. It is proposed that chloroplasts could possess a RETC on the thylakoid membrane, in addition to PETC. Identification of a plastid terminal oxidase (PTOX) in the chloroplast from the Arabidopsis variegation mutant immutans (im) demonstrated the presence of a RETC in chloroplasts, and the PTOX is the committed oxidase. PTOX is distantly related to the mitochondrial alternative oxidase (AOX), which is responsible for the CN-insensitive alternative RETC. Similar to AOX, an ubiquinol (UQH2) oxidase, PTOX is a plastoquinol (PQH2) oxidase on the chloroplast thylakoid membrane. Lack of PTOX, Arabidopsis im showed a light-dependent variegation phenotype; and mutant plants will not survive the mediocre light intensity during its early development stage. PTOX is very important for carotenoid biosynthesis, since the phytoene desaturation, a key step in the carotenoid biosynthesis, is blocked in the white sectors of Arabidopsis im mutant. PTOX is found to be a stress-related protein in numerous research instances. It is generally believed that PTOX can protect plants from various environmental stresses, especially high light stress. PTOX also plays significant roles in chloroplast development and plant morphogenesis. Global physiological roles played by PTOX could be a direct or indirect consequence of its PQH2 oxidase activity to maintain the PQ pool redox state on the thylakoid membrane. The PTOX-dependent chloroplast RETC (so-called chlororespiration) does not contribute significantly when chloroplast PETC is normally developed and functions well. However, PTOX-mediated RETC could be the major force to regulate the PQ pool redox balance in the darkness, under conditions of stress, in nonphotosynthetic plastids, especially in the early development from proplastids to chloroplasts.
Collapse
Affiliation(s)
- D Wang
- The Key Laboratory of Western Resources Biology and Biological Technology, College of Life Sciences, Northwest University, Xian, China; Shaanxi Province Key Laboratory of Biotechnology, College of Life Sciences, Northwest University, Xian, China
| | - A Fu
- The Key Laboratory of Western Resources Biology and Biological Technology, College of Life Sciences, Northwest University, Xian, China; Shaanxi Province Key Laboratory of Biotechnology, College of Life Sciences, Northwest University, Xian, China.
| |
Collapse
|
12
|
Surve SV, Jensen BC, Heestand M, Mazet M, Smith TK, Bringaud F, Parsons M, Schnaufer A. NADH dehydrogenase of Trypanosoma brucei is important for efficient acetate production in bloodstream forms. Mol Biochem Parasitol 2016; 211:57-61. [PMID: 27717801 PMCID: PMC5225879 DOI: 10.1016/j.molbiopara.2016.10.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 09/29/2016] [Accepted: 10/03/2016] [Indexed: 11/29/2022]
Abstract
Various genetic mutants of NDH2 were created in bloodstream form Trypanosoma brucei. NDH2 null mutants showed a substantial reduction in growth. NDH2 ablation in a complex I deficient background led to severe growth restriction. Upon prolonged culture, parasites partially compensated for NDH2 deficiency. Loss of NDH2 led to reduced acetate, potentially contributing to the growth defect.
In the slender bloodstream form, Trypanosoma brucei mitochondria are repressed for many functions. Multiple components of mitochondrial complex I, NADH:ubiquinone oxidoreductase, are expressed in this stage, but electron transfer through complex I is not essential. Here we investigate the role of the parasite’s second NADH:ubiquinone oxidoreductase, NDH2, which is composed of a single subunit that also localizes to the mitochondrion. While inducible knockdown of NDH2 had a modest growth effect in bloodstream forms, NDH2 null mutants, as well as inducible knockdowns in a complex I deficient background, showed a greater reduction in growth. Altering the NAD+/NADH balance would affect numerous processes directly and indirectly, including acetate production. Indeed, loss of NDH2 led to reduced levels of acetate, which is required for several essential pathways in bloodstream form T. brucei and which may have contributed to the observed growth defect. In conclusion our study shows that NDH2 is important, but not essential, in proliferating bloodstream forms of T. brucei, arguing that the mitochondrial NAD+/NADH balance is important in this stage, even though the mitochondrion itself is not actively engaged in the generation of ATP.
Collapse
Affiliation(s)
- Sachin V Surve
- Center for Infectious Disease Research (Formerly Seattle Biomedical Research Institute), 307 Westlake Ave. N., Seattle, WA, 98109, USA
| | - Bryan C Jensen
- Center for Infectious Disease Research (Formerly Seattle Biomedical Research Institute), 307 Westlake Ave. N., Seattle, WA, 98109, USA
| | - Meredith Heestand
- Center for Infectious Disease Research (Formerly Seattle Biomedical Research Institute), 307 Westlake Ave. N., Seattle, WA, 98109, USA
| | - Muriel Mazet
- Centre de Résonance Magnétique des Systèmes Biologiques (RMSB), UMR5536, Université de Bordeaux, CNRS, Bordeaux, France
| | - Terry K Smith
- Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St. Andrews KY16 9ST, United Kingdom
| | - Frédéric Bringaud
- Centre de Résonance Magnétique des Systèmes Biologiques (RMSB), UMR5536, Université de Bordeaux, CNRS, Bordeaux, France
| | - Marilyn Parsons
- Center for Infectious Disease Research (Formerly Seattle Biomedical Research Institute), 307 Westlake Ave. N., Seattle, WA, 98109, USA; Dept. of Global Health, University of Washington, Seattle, WA, 98195, USA.
| | - Achim Schnaufer
- Institute of Immunology & Infection Research and Centre of Immunity, Infection & Evolution, The University of Edinburgh, Edinburgh, EH9 3FL, United Kingdom.
| |
Collapse
|
13
|
|
14
|
Puxty RJ, Millard AD, Evans DJ, Scanlan DJ. Shedding new light on viral photosynthesis. PHOTOSYNTHESIS RESEARCH 2015; 126:71-97. [PMID: 25381655 DOI: 10.1007/s11120-014-0057-x] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 10/29/2014] [Indexed: 06/04/2023]
Abstract
Viruses infecting the environmentally important marine cyanobacteria Prochlorococcus and Synechococcus encode 'auxiliary metabolic genes' (AMGs) involved in the light and dark reactions of photosynthesis. Here, we discuss progress on the inventory of such AMGs in the ever-increasing number of viral genome sequences as well as in metagenomic datasets. We contextualise these gene acquisitions with reference to a hypothesised fitness gain to the phage. We also report new evidence with regard to the sequence and predicted structural properties of viral petE genes encoding the soluble electron carrier plastocyanin. Viral copies of PetE exhibit extensive modifications to the N-terminal signal peptide and possess several novel residues in a region responsible for interaction with redox partners. We also highlight potential knowledge gaps in this field and discuss future opportunities to discover novel phage-host interactions involved in the photosynthetic process.
Collapse
Affiliation(s)
- Richard J Puxty
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
- School of Biological Sciences, University of California, Irvine, CA 92697, USA
| | - Andrew D Millard
- Warwick Medical School, University of Warwick, Coventry, CV4 7AL, UK
| | - David J Evans
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - David J Scanlan
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK.
| |
Collapse
|
15
|
Costa JH, McDonald AE, Arnholdt-Schmitt B, Fernandes de Melo D. A classification scheme for alternative oxidases reveals the taxonomic distribution and evolutionary history of the enzyme in angiosperms. Mitochondrion 2014; 19 Pt B:172-83. [DOI: 10.1016/j.mito.2014.04.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Revised: 03/23/2014] [Accepted: 04/11/2014] [Indexed: 10/25/2022]
|
16
|
Naydenov N, Takumi S, Sugie A, Ogihara Y, Atanassov A, Nakamura C. Structural Diversity of the Wheat Nuclear GeneWaox1aEncoding Mitochondrial Alternative Oxidase, A Single Unique Enzyme In The Cyanide-Resistant Alternative Pathway. BIOTECHNOL BIOTEC EQ 2014. [DOI: 10.1080/13102818.2005.10817153] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
|
17
|
|
18
|
Neimanis K, Staples JF, Hüner NP, McDonald AE. Identification, expression, and taxonomic distribution of alternative oxidases in non-angiosperm plants. Gene 2013; 526:275-86. [DOI: 10.1016/j.gene.2013.04.072] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 04/23/2013] [Accepted: 04/24/2013] [Indexed: 10/26/2022]
|
19
|
Ahmad N, Michoux F, Nixon PJ. Investigating the production of foreign membrane proteins in tobacco chloroplasts: expression of an algal plastid terminal oxidase. PLoS One 2012; 7:e41722. [PMID: 22848578 PMCID: PMC3404998 DOI: 10.1371/journal.pone.0041722] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Accepted: 06/28/2012] [Indexed: 12/29/2022] Open
Abstract
Chloroplast transformation provides an inexpensive, easily scalable production platform for expression of recombinant proteins in plants. However, this technology has been largely limited to the production of soluble proteins. Here we have tested the ability of tobacco chloroplasts to express a membrane protein, namely plastid terminal oxidase 1 from the green alga Chlamydomonas reinhardtii (Cr-PTOX1), which is predicted to function as a plastoquinol oxidase. A homoplastomic plant containing a codon-optimised version of the nuclear gene encoding PTOX1, driven by the 16S rRNA promoter and 5'UTR of gene 10 from phage T7, was generated using a particle delivery system. Accumulation of Cr-PTOX1 was shown by immunoblotting and expression in an enzymatically active form was confirmed by using chlorophyll fluorescence to measure changes in the redox state of the plastoquinone pool in leaves. Growth of Cr-PTOX1 expressing plants was, however, more sensitive to high light than WT. Overall our results confirm the feasibility of using plastid transformation as a means of expressing foreign membrane proteins in the chloroplast.
Collapse
Affiliation(s)
- Niaz Ahmad
- Division of Molecular Biosciences, Imperial College London, London, United Kingdom.
| | | | | |
Collapse
|
20
|
McDonald AE, Ivanov AG, Bode R, Maxwell DP, Rodermel SR, Hüner NPA. Flexibility in photosynthetic electron transport: the physiological role of plastoquinol terminal oxidase (PTOX). BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1807:954-67. [PMID: 21056542 DOI: 10.1016/j.bbabio.2010.10.024] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 10/27/2010] [Accepted: 10/29/2010] [Indexed: 11/27/2022]
Abstract
Oxygenic photosynthesis depends on a highly conserved electron transport system, which must be particularly dynamic in its response to environmental and physiological changes, in order to avoid an excess of excitation energy and subsequent oxidative damage. Apart from cyclic electron flow around PSII and around PSI, several alternative electron transport pathways exist including a plastoquinol terminal oxidase (PTOX) that mediates electron flow from plastoquinol to O(2). The existence of PTOX was first hypothesized in 1982 and this was verified years later based on the discovery of a non-heme, di-iron carboxylate protein localized to thylakoid membranes that displayed sequence similarity to the mitochondrial alternative oxidase. The absence of this protein renders higher plants susceptible to excitation pressure dependant variegation combined with impaired carotenoid synthesis. Chloroplasts, as well as other plastids (i.e. etioplasts, amyloplasts and chromoplasts), fail to assemble organized internal membrane structures correctly, when exposed to high excitation pressure early in development. While the role of PTOX in plastid development is established, its physiological role under stress conditions remains equivocal and we postulate that it serves as an alternative electron sink under conditions where the acceptor side of PSI is limited. The aim of this review is to provide an overview of the past achievements in this field and to offer directions for future investigative efforts. Plastoquinol terminal oxidase (PTOX) is involved in an alternative electron transport pathway that mediates electron flow from plastoquinol to O(2). This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts.
Collapse
Affiliation(s)
- Allison E McDonald
- Department of Biology, Wilfrid Laurier University, Science Building, 75 University Avenue West, Waterloo, Ontario, Canada N2L 3C5.
| | | | | | | | | | | |
Collapse
|
21
|
Peltier G, Tolleter D, Billon E, Cournac L. Auxiliary electron transport pathways in chloroplasts of microalgae. PHOTOSYNTHESIS RESEARCH 2010; 106:19-31. [PMID: 20607407 DOI: 10.1007/s11120-010-9575-3] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Accepted: 06/16/2010] [Indexed: 05/11/2023]
Abstract
Microalgae are photosynthetic organisms which cover an extraordinary phylogenic diversity and have colonized extremely diverse habitats. Adaptation to contrasted environments in terms of light and nutrient's availabilities has been possible through a high flexibility of the photosynthetic machinery. Indeed, optimal functioning of photosynthesis in changing environments requires a fine tuning between the conversion of light energy by photosystems and its use by metabolic reaction, a particularly important parameter being the balance between phosphorylating (ATP) and reducing (NADPH) power supplies. In addition to the main route of electrons operating during oxygenic photosynthesis, called linear electron flow or Z scheme, auxiliary routes of electron transfer in interaction with the main pathway have been described. These reactions which include non-photochemical reduction of intersystem electron carriers, cyclic electron flow around PSI, oxidation by molecular O(2) of the PQ pool or of the PSI electron acceptors, participate in the flexibility of photosynthesis by avoiding over-reduction of electron carriers and modulating the NADPH/ATP ratio depending on the metabolic demand. Forward or reverse genetic approaches performed in model organisms such as Arabidopsis thaliana for higher plants, Chlamydomonas reinhardtii for green algae and Synechocystis for cyanobacteria allowed identifying molecular components involved in these auxiliary electron transport pathways, including Ndh-1, Ndh-2, PGR5, PGRL1, PTOX and flavodiiron proteins. In this article, we discuss the diversity of auxiliary routes of electron transport in microalgae, with particular focus in the presence of these components in the microalgal genomes recently sequenced. We discuss how these auxiliary mechanisms of electron transport may have contributed to the adaptation of microalgal photosynthesis to diverse and changing environments.
Collapse
Affiliation(s)
- Gilles Peltier
- CEA, Direction des Sciences du Vivant, Institut de Biologie Environnementale et de Biotechnologie, Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues, CEA Cadarache, Saint-Paul-lez-Durance 13108, France.
| | | | | | | |
Collapse
|
22
|
Albury MS, Elliott C, Moore AL. Towards a structural elucidation of the alternative oxidase in plants. PHYSIOLOGIA PLANTARUM 2009; 137:316-27. [PMID: 19719482 DOI: 10.1111/j.1399-3054.2009.01270.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
In addition to the conventional cytochrome c oxidase, mitochondria of all plants studied to date contain a second cyanide-resistant terminal oxidase or alternative oxidase (AOX). The AOX is located in the inner mitochondrial membrane and branches from the cytochrome pathway at the level of the quinone pool. It is non-protonmotive and couples the oxidation of ubiquinone to the reduction of oxygen to water. For many years, the AOX was considered to be confined to plants, fungi and a small number of protists. Recently, it has become apparent that the AOX occurs in wide range of organisms including prokaryotes and a moderate number of animal species. In this paper, we provide an overview of general features and current knowledge available about the AOX with emphasis on structure, the active site and quinone-binding site. Characterisation of the AOX has advanced considerably over recent years with information emerging about the role of the protein, regulatory regions and functional sites. The large number of sequences available is now enabling us to obtain a clearer picture of evolutionary origins and diversity.
Collapse
Affiliation(s)
- Mary S Albury
- Division of Biochemistry and Biomedical Sciences, School of Life Sciences, University of Sussex, Falmer, Brighton BN19QG, UK
| | | | | |
Collapse
|
23
|
McDonald AE. Alternative oxidase: what information can protein sequence comparisons give us? PHYSIOLOGIA PLANTARUM 2009; 137:328-341. [PMID: 19493309 DOI: 10.1111/j.1399-3054.2009.01242.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The finding that alternative oxidase (AOX) is present in most kingdoms of life has resulted in a large number of AOX sequences that are available for analyses. Multiple sequence alignments of AOX proteins from evolutionarily divergent organisms represent a valuable tool and can be used to identify amino acids and domains that may play a role in catalysis, membrane association and post-translational regulation, especially when these data are coupled with the structural model for the enzyme. I validate the use of this approach by demonstrating that it detects the conserved glutamate and histidine residues in AOX that initially led to its identification as a di-iron carboxylate protein and the generation of a structural model for the protein. A comparative analysis using a larger dataset identified 35 additional amino acids that are conserved in all AOXs examined, 30 of which have not been investigated to date. I hypothesize that these residues will be involved in the quinol terminal oxidase activity or membrane association of AOX. Major differences in AOX protein sequences between kingdoms are revealed, and it is hypothesized that two angiosperm-specific domains may be responsible for the non-covalent dimerization of AOX, whereas two indels in the aplastidic AOXs may play a role in their post-translational regulation. A scheme for predicting whether a particular AOX protein will be recognized by the alternative oxidase monoclonal antibody generated against the AOX of Sauromatum guttatum (Voodoo lily) is presented. The number of functional sites in AOX is greater than expected, and determining the structure of AOX will prove extremely valuable to future research.
Collapse
Affiliation(s)
- Allison E McDonald
- Department of Biology, The University of Western Ontario, 1151 Richmond St. N., London, Ontario N6A5B7, Canada.
| |
Collapse
|
24
|
Hansen LD, Thomas NR, Arnholdt-Schmitt B. Temperature responses of substrate carbon conversion efficiencies and growth rates of plant tissues. PHYSIOLOGIA PLANTARUM 2009; 137:446-58. [PMID: 19843241 DOI: 10.1111/j.1399-3054.2009.01287.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Growth rates of plant tissues depend on both the respiration rate and the efficiency with which carbon is incorporated into new structural biomass. Calorespirometric measurement of respiratory heat and CO2 rates, from which both efficiency and growth rate can be calculated, is a well established method for determining the effects of rapid temperature changes on the respiratory and growth properties of plant tissues. The effect of the alternative oxidase/cytochrome oxidase activity ratio on efficiency is calculated from first principles. Data on the temperature dependence of the substrate carbon conversion efficiency are tabulated. These data show that epsilon is maximum and approximately constant through the optimum growth temperature range and decreases rapidly as temperatures approach temperature limits to growth. The width of the maximum and the slopes of decreasing epsilon at high and low temperatures vary greatly with species, cultivars and accessions.
Collapse
Affiliation(s)
- Lee D Hansen
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA. Lee
| | | | | |
Collapse
|
25
|
McDonald AE, Vanlerberghe GC, Staples JF. Alternative oxidase in animals: unique characteristics and taxonomic distribution. ACTA ACUST UNITED AC 2009; 212:2627-34. [PMID: 19648408 DOI: 10.1242/jeb.032151] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Alternative oxidase (AOX), a ubiquinol oxidase, introduces a branch point into the respiratory electron transport chain, bypassing complexes III and IV and resulting in cyanide-resistant respiration. Previously, AOX was thought to be limited to plants and some fungi and protists but recent work has demonstrated the presence of AOX in most kingdoms of life, including animals. In the present study we identified AOX in 28 animal species representing nine phyla. This expands the known taxonomic distribution of AOX in animals by 10 species and two phyla. Using bioinformatics we found AOX gene sequences in members of the animal phyla Porifera, Placozoa, Cnidaria, Mollusca, Annelida, Nematoda, Echinodermata, Hemichordata and Chordata. Using reverse-transcriptase polymerase chain reaction (RT-PCR) with degenerate primers designed to recognize conserved regions of animal AOX, we demonstrated that AOX genes are transcribed in several animals from different phyla. An analysis of full-length AOX sequences revealed an amino acid motif in the C-terminal region of the protein that is unique to animal AOXs. Animal AOX also lacks an N-terminal cysteine residue that is known to be important for AOX enzyme regulation in plants. We conclude that the presence of AOX is the ancestral state in animals and hypothesize that its absence in some lineages, including vertebrates, is due to gene loss events.
Collapse
Affiliation(s)
- Allison E McDonald
- Department of Biology, The University of Western Ontario, London, Ontario, Canada N6A 5B7.
| | | | | |
Collapse
|
26
|
Characterization of Citrus sinensis type 1 mitochondrial alternative oxidase and expression analysis in biotic stress. Biosci Rep 2009; 30:59-71, 1 p following 71. [DOI: 10.1042/bsr20080180] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The higher plant mitochondrial electron transport chain contains an alternative pathway that ends with the AOX (alternative oxidase). The AOX proteins are encoded by a small gene family composed of two discrete gene subfamilies. Aox1 is present in both monocot and eudicot plants, whereas Aox2 is only present in eudicot plants. We isolated a genomic clone from Citrus sinensis containing the Aox1a gene. The orange Aox1a consists of four exons interrupted by three introns and its promoter harbours diverse putative stress-specific regulatory motifs including pathogen response elements. The role of the Aox1a gene was evaluated during the compatible interaction between C. sinensis and Xanthomonas axonopodis pv. citri and no induction of the Aox1a at the transcriptional level was observed. On the other hand, Aox1a was studied in orange plants during non-host interactions with Pseudomonas syringae pv. tomato and Xanthomonas campestris pv. vesicatoria, which result in hypersensitive response. Both phytopathogens produced a strong induction of Aox1a, reaching a maximum at 8 h post-infiltration. Exogenous application of salicylic acid produced a slight increase in the steady-state level of Aox1a, whereas the application of fungi elicitors showed the highest induction. These results suggest that AOX1a plays a role during biotic stress in non-host plant pathogen interaction.
Collapse
|
27
|
Fu A, Aluru M, Rodermel SR. Conserved active site sequences in Arabidopsis plastid terminal oxidase (PTOX): in vitro and in planta mutagenesis studies. J Biol Chem 2009; 284:22625-32. [PMID: 19542226 PMCID: PMC2755669 DOI: 10.1074/jbc.m109.017905] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 06/16/2009] [Indexed: 11/06/2022] Open
Abstract
The plastid terminal oxidase (PTOX) is distantly related to the mitochondrial alternative oxidase (AOX). Both are members of the diiron carboxylate quinol oxidase (DOX) class of proteins. PTOX and AOX contain 20 highly conserved amino acids, six of which are Fe-binding ligands. We have previously used in vitro and in planta activity assays to examine the functional importance of the Fe-binding sites. In this report, we conduct alanine-scanning mutagenesis on the 14 other conserved sites using our in vitro and in planta assay procedures. We found that the 14 sites fall into three classes: (i) Ala-139, Pro-142, Glu-171, Asn-174, Leu-179, Pro-216, Ala-230, Asp-287, and Arg-293 are dispensable for activity; (ii) Tyr-234 and Asp-295 are essential for activity; and (iii) Leu-135, His-151, and Tyr-212 are important but not essential for activity. Our data are consistent with the proposed role of some of these residues in active site conformation, substrate binding, and/or catalysis. Titration experiments showed that down-regulation of PTOX to approximately 3% of wild-type levels did not compromise plant growth, at least under ambient growth conditions. This suggests that PTOX is normally in excess, especially early in thylakoid membrane biogenesis.
Collapse
Affiliation(s)
- Aigen Fu
- From the Department of Genetics, Development and Cell Biology, Iowa State University, Ames, Iowa 50011
| | - Maneesha Aluru
- From the Department of Genetics, Development and Cell Biology, Iowa State University, Ames, Iowa 50011
| | - Steven R. Rodermel
- From the Department of Genetics, Development and Cell Biology, Iowa State University, Ames, Iowa 50011
| |
Collapse
|
28
|
Wang J, Sommerfeld M, Hu Q. Occurrence and environmental stress responses of two plastid terminal oxidases in Haematococcus pluvialis (Chlorophyceae). PLANTA 2009; 230:191-203. [PMID: 19408010 DOI: 10.1007/s00425-009-0932-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Accepted: 04/13/2009] [Indexed: 05/06/2023]
Abstract
The plastid terminal oxidase (PTOX) is a plastoquinol oxidase involved in carotenoid biosynthesis in higher plants, and may also represent the elusive oxidase in chlororespiration. Haematococcus pluvialis is a green alga that has the ability to synthesize and accumulate large amounts of the red carotenoid astaxanthin (ca. 2% of dry weight) under various stress conditions. However, the occurrence and function of PTOX in astaxanthin synthesis and the stress response in this organism is unknown. In this study, two ptox cDNAs were cloned and sequenced from H. pluvialis and were designated as ptox1 and ptox2. Genome sequence analysis and database searching revealed that duplication of PTOX gene occurred in certain eukaryotic algae, but not in cyanobacteria and higher plants. The physiological and biochemical evidence indicated that PTOX is involved in astaxanthin synthesis and plays a critical protective role against stress. Analysis of the transcriptional expression of the PTOXs and phytoene desaturase gene further suggests that it may be PTOX1 rather than PTOX2 that is co-regulated with astaxanthin synthesis. The fact that the changes in transcripts of ptoxs in response to high light and other stressors and the differential expression of ptox1 and ptox2, suggests that PTOX, coupled with astaxanthin synthesis pathway, exerts broad, yet undefined functions in addition to those identified in higher plants.
Collapse
Affiliation(s)
- Jiangxin Wang
- Department of Applied Biological Sciences, Arizona State University, Polytechnic Campus, 7001 E. Williams Field Road, Mesa, AZ 85212, USA
| | | | | |
Collapse
|
29
|
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.
Collapse
Affiliation(s)
- Allison E McDonald
- Department of Biology, The University of Western Ontario, Biological and Geological Sciences Building, London, Ontario N6A 5B7, Canada. Email
| |
Collapse
|
30
|
Bailey S, Melis A, Mackey KRM, Cardol P, Finazzi G, van Dijken G, Berg GM, Arrigo K, Shrager J, Grossman A. Alternative photosynthetic electron flow to oxygen in marine Synechococcus. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:269-76. [PMID: 18241667 DOI: 10.1016/j.bbabio.2008.01.002] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Revised: 12/18/2007] [Accepted: 01/10/2008] [Indexed: 11/17/2022]
Abstract
Cyanobacteria dominate the world's oceans where iron is often barely detectable. One manifestation of low iron adaptation in the oligotrophic marine environment is a decrease in levels of iron-rich photosynthetic components, including the reaction center of photosystem I and the cytochrome b6f complex [R.F. Strzepek and P.J. Harrison, Photosynthetic architecture differs in coastal and oceanic diatoms, Nature 431 (2004) 689-692.]. These thylakoid membrane components have well characterised roles in linear and cyclic photosynthetic electron transport and their low abundance creates potential impediments to photosynthetic function. Here we show that the marine cyanobacterium Synechococcus WH8102 exhibits significant alternative electron flow to O2, a potential adaptation to the low iron environment in oligotrophic oceans. This alternative electron flow appears to extract electrons from the intersystem electron transport chain, prior to photosystem I. Inhibitor studies demonstrate that a propyl gallate-sensitive oxidase mediates this flow of electrons to oxygen, which in turn alleviates excessive photosystem II excitation pressure that can often occur even at relatively low irradiance. These findings are also discussed in the context of satisfying the energetic requirements of the cell when photosystem I abundance is low.
Collapse
Affiliation(s)
- Shaun Bailey
- The Carnegie Institution, Department of Plant Biology, 260 Panama Street, Stanford, CA 94305, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Juárez O, Guerra G, Velázquez I, Flores-Herrera O, Rivera-Pérez RE, Pardo JP. The physiologic role of alternative oxidase in Ustilago maydis. FEBS J 2006; 273:4603-15. [PMID: 16965537 DOI: 10.1111/j.1742-4658.2006.05463.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Alternative oxidase (AOX) is a ubiquitous respiratory enzyme found in plants, fungi, protists and some bacterial species. One of the major questions about this enzyme is related to its metabolic role(s) in cellular physiology, due to its capacity to bypass the proton-pumping cytochrome pathway, and as a consequence it has great energy-wasting potential. In this study, the physiological role and regulatory mechanisms of AOX in the fungal phytopathogen Ustilago maydis were studied. We found evidence for at least two metabolic functions for AOX in this organism, as a major part of the oxidative stress-handling machinery, a well-described issue, and as part of the mechanisms that increase the metabolic plasticity of the cell, a role that might be valuable for organisms exposed to variations in temperature, nutrient source and availability, and biotic or abiotic factors that limit the activity of the cytochrome pathway. Experiments under different culture conditions of ecological significance for this organism revealed that AOX activity is modified by the growth stage of the culture, amino acid availability and growth temperature. In addition, nucleotide content, stimulation of AOX by AMP and respiratory rates obtained after inhibition of the cytochrome pathway showed that fungal/protist AOX is activated under low-energy conditions, in contrast to plant AOX, which is activated under high-energy conditions. An estimation of the contribution of AOX to cell respiration was performed by comparing the steady-state concentration of adenine nucleotides, the mitochondrial membrane potential, and the respiratory rate.
Collapse
Affiliation(s)
- Oscar Juárez
- Departamento de Bioquímica, Edificio D, Facultad de Medicina, Universidad Nacional Autónoma de México, México
| | | | | | | | | | | |
Collapse
|
32
|
McDonald AE, Vanlerberghe GC. Origins, evolutionary history, and taxonomic distribution of alternative oxidase and plastoquinol terminal oxidase. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2006; 1:357-64. [PMID: 20483267 DOI: 10.1016/j.cbd.2006.08.001] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2006] [Revised: 08/01/2006] [Accepted: 08/05/2006] [Indexed: 10/24/2022]
Abstract
Alternative oxidase (AOX) and plastoquinol terminal oxidase (PTOX) are related quinol oxidases associated with respiratory and photosynthetic electron transport chains, respectively. Contrary to previous belief, AOX is present in numerous animal phyla, as well as heterotrophic and marine phototrophic proteobacteria. PTOX appears limited to organisms capable of oxygenic photosynthesis, including cyanobacteria, algae and plants. We propose that both oxidases originated in prokaryotes from a common ancestral di-iron carboxylate protein that diversified to AOX within ancient proteobacteria and PTOX within ancient cyanobacteria. Each then entered the eukaryotic lineage separately; AOX by the endosymbiotic event that gave rise to mitochondria and later PTOX by the endosymbiotic event that gave rise to chloroplasts. Both oxidases then spread through the eukaryotic domain by vertical inheritance, as well as by secondary and potentially tertiary endosymbiotic events.
Collapse
Affiliation(s)
- Allison E McDonald
- Department of Life Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, Toronto, Canada
| | | |
Collapse
|
33
|
Umbach AL, Ng VS, Siedow JN. Regulation of plant alternative oxidase activity: A tale of two cysteines. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:135-42. [PMID: 16457775 DOI: 10.1016/j.bbabio.2005.12.005] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2005] [Revised: 12/14/2005] [Accepted: 12/19/2005] [Indexed: 11/21/2022]
Abstract
Two Cys residues, Cys(I) and Cys(II), are present in most plant alternative oxidases (AOXs). Cys(I) inactivates AOX by forming a disulfide bond with the corresponding Cys(I) residue on the adjacent subunit of the AOX homodimer. When reduced, Cys(I) associates with alpha-keto acids, such as pyruvate, to activate AOX, an effect mimicked by charged amino acid substitutions at the Cys(I) site. Cys(II) may also be a site of AOX activity regulation, through interaction with the small alpha-keto acid, glyoxylate. Comparison of Arabidopsis AOX1a (AtAOX1a) mutants with single or double substitutions at Cys(I) and Cys(II) confirmed that glyoxylate interacted with either Cys, while the effect of pyruvate (or succinate for AtAOX1a substituted with Ala at Cys(I)) was limited to Cys(I). A variety of Cys(II) substitutions constitutively activated AtAOX1a, indicating that neither the catalytic site nor, unlike at Cys(I), charge repulsion is involved. Independent effects at each Cys were suggested by lack of Cys(II) substitution interference with pyruvate stimulation at Cys(I), and close to additive activation at the two sites. However, results obtained using diamide treatment to covalently link the AtAOX1a subunits by the disulfide bond indicated that Cys(I) must be in the reduced state for activation at Cys(II) to occur.
Collapse
Affiliation(s)
- Ann L Umbach
- DCMB Group/Biology Department, Box 91000, Duke University, Durham, NC 27708-1000, USA.
| | | | | |
Collapse
|
34
|
Suzuki T, Hashimoto T, Yabu Y, Majiwa PAO, Ohshima S, Suzuki M, Lu S, Hato M, Kido Y, Sakamoto K, Nakamura K, Kita K, Ohta N. Alternative oxidase (AOX) genes of African trypanosomes: phylogeny and evolution of AOX and plastid terminal oxidase families. J Eukaryot Microbiol 2005; 52:374-81. [PMID: 16014016 DOI: 10.1111/j.1550-7408.2005.00050.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To clarify evolution and phylogenetic relationships of trypanosome alternative oxidase (AOX) molecules, AOX genes (cDNAs) of the African trypanosomes, Trypanosoma congolense and Trypanosoma evansi, were cloned by PCR. Both AOXs possess conserved consensus motifs (-E-, -EXXH-). The putative amino acid sequence of the AOX of T. evansi was exactly the same as that of T. brucei. A protein phylogeny of trypanosome AOXs revealed that three genetically and pathogenically distinct strains of T. congolense are closely related to each other. When all known AOX sequences collected from current databases were analyzed, the common ancestor of these three Trypanosoma species shared a sister-group position to T. brucei/T. evansi. Monophyly of Trypanosoma spp. was clearly supported (100% bootstrap value) with Trypanosoma vivax placed at the most basal position of the Trypanosoma clade. Monophyly of other eukaryotic lineages, terrestrial plants + red algae, Metazoa, diatoms, Alveolata, oomycetes, green algae, and Fungi, was reconstructed in the best AOX tree obtained from maximum likelihood analysis, although some of these clades were not strongly supported. The terrestrial plants + red algae clade showed the closest affinity with an alpha-proteobacterium, Novosphingobium aromaticivorans, and the common ancestor of these lineages, was separated from other eukaryotes. Although the root of the AOX subtree was not clearly determined, subsequent phylogenetic analysis of the composite tree for AOX and plastid terminal oxidase (PTOX) demonstrated that PTOX and related cyanobacterial sequences are of a monophyletic origin and their common ancestor is linked to AOX sequences.
Collapse
Affiliation(s)
- Takashi Suzuki
- Department of Molecular Parasitology, Nagoya City University, Graduate School of Medical Sciences, Kawasumi, Mizuho 467-8601 Nagoya, Japan.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
35
|
Nakamura K, Sakamoto K, Kido Y, Fujimoto Y, Suzuki T, Suzuki M, Yabu Y, Ohta N, Tsuda A, Onuma M, Kita K. Mutational analysis of the Trypanosoma vivax alternative oxidase: The E(X)6Y motif is conserved in both mitochondrial alternative oxidase and plastid terminal oxidase and is indispensable for enzyme activity. Biochem Biophys Res Commun 2005; 334:593-600. [PMID: 16009344 DOI: 10.1016/j.bbrc.2005.06.131] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 06/23/2005] [Indexed: 11/16/2022]
Abstract
Based on amino acid sequence similarity and the ability to catalyze the four-electron reduction of oxygen to water using a quinol substrate, mitochondrial alternative oxidase (AOX) and plastid terminal oxidase (PTOX) appear to be two closely related members of the membrane-bound diiron carboxylate group of proteins. In the current studies, we took advantage of the high activity of Trypanosoma vivax AOX (TvAOX) to examine the importance of the conserved Glu and the Tyr residues around the predicted third helix region of AOXs and PTOXs. We first compared the amino acid sequences of TvAOX with AOXs and PTOXs from various taxa and then performed alanine-scanning mutagenesis of TvAOX between amino acids Y(199) and Y(247). We found that the ubiquinol oxidase activity of TvAOX is completely lost in the E214A mutant, whereas mutants E215A and E216A retained more than 30% of the wild-type activity. Among the Tyr mutants, a complete loss of activity was also observed for the Y221A mutant, whereas the activities were equivalent to wild-type for the Y199A, Y212A, and Y247A mutants. Finally, residues Glu(214) and Tyr(221) were found to be strictly conserved among AOXs and PTOXs. Based on these findings, it appears that AOXs and PTOXs are a novel subclass of diiron carboxylate proteins that require the conserved motif E(X)(6)Y for enzyme activity.
Collapse
Affiliation(s)
- Kosuke Nakamura
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Henriquez FL, Richards TA, Roberts F, McLeod R, Roberts CW. The unusual mitochondrial compartment of Cryptosporidium parvum. Trends Parasitol 2005; 21:68-74. [PMID: 15664529 DOI: 10.1016/j.pt.2004.11.010] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Recent studies, including the Cryptosporidium parvum Genome Project, have provided evidence for a mitochondrial-derived compartment in this parasite. This organelle appears to lack a genome, and thus must be entirely dependent on nuclear-encoded proteins. Here, we review the evidence for such an organelle in C. parvum and its probable function. There is no adequate treatment for infection by this parasite and so the elucidation of the role of this organelle and the effective targeting of its functions by antimicrobial agents might provide new treatments for infection by C. parvum.
Collapse
Affiliation(s)
- Fiona L Henriquez
- Department of Immunology, Strathclyde Institute for Biomedical Sciences, University of Strathclyde, 27 Taylor St, Glasgow, UK, G4 0NR
| | | | | | | | | |
Collapse
|
37
|
McDonald AE, Vanlerberghe GC. Alternative oxidase and plastoquinol terminal oxidase in marine prokaryotes of the Sargasso Sea. Gene 2005; 349:15-24. [PMID: 15777727 DOI: 10.1016/j.gene.2004.12.049] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2004] [Revised: 12/06/2004] [Accepted: 12/22/2004] [Indexed: 11/29/2022]
Abstract
Alternative oxidase (AOX) represents a non-energy conserving branch in mitochondrial electron transport while plastoquinol terminal oxidase (PTOX) represents a potential branch in photosynthetic electron transport. Using a metagenomics dataset, we have uncovered numerous and diverse AOX and PTOX genes from the Sargasso Sea. Sequence similarity, synteny and phylogenetic analyses indicate that the large majority of these genes are from prokaryotes. AOX appears to be widely distributed among marine Eubacteria while PTOX is widespread among strains of cyanobacteria closely related to the high-light adapted Prochlorococcus marinus MED4, as well as Synechococcus. The wide distribution of AOX and PTOX in marine prokaryotes may have important implications for productivity in the world's oceans.
Collapse
Affiliation(s)
- Allison E McDonald
- Department of Life Sciences, University of Toronto at Scarborough, 1265 Military Trail, Scarborough, ON Canada M1C 1A4
| | | |
Collapse
|
38
|
Finnegan PM, Soole KL, Umbach AL. Alternative Mitochondrial Electron Transport Proteins in Higher Plants. PLANT MITOCHONDRIA: FROM GENOME TO FUNCTION 2004. [DOI: 10.1007/978-1-4020-2400-9_9] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|