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Skubatz H. Nonsteroidal anti-inflammatory drugs as antipyretics and modulators of a molecular clock(s) in the appendix of Sauromatum venosum inflorescence. PLANT BIOLOGY (STUTTGART, GERMANY) 2023; 25:152-160. [PMID: 36074072 DOI: 10.1111/plb.13466] [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: 03/21/2022] [Accepted: 08/17/2022] [Indexed: 06/15/2023]
Abstract
The appendix of the Sauromatum senosum inflorescence is a striking example of thermogenesis in plants. On the day of opening, the Sauromatum appendix becomes hot, reaching up to 32 °C. Aspirin, salicylic acid and 2,6-dihydroxybenzoic acid, a subclass of NSAIDs, induce a temperature rise from three mitochondrial sources: alternative oxidase, F1 FO -ATP synthase and adenine nucleotide translocator. This temperature rise is synchronized and compounded under various light/dark regimes. We studied the effect of different subgroups of NSAIDs on the temperature rise. Tissue slices of appendix of Sauromatum and Arum italicum inflorescences at a pre-mature stage were treated with the three inducers in combination with one NSAID under constant light or darkness and under different photoperiods. Temperature rise generated by the three heat sources in the presence of inducers and different non-selective NSAIDs were not compounded and occurred at three different times. Under constant light, DuP-697, ibuprofen, flurbiprofen, acetaminophen and diclofenac suppressed the temperature rise induced by the three salicylates. Desynchronization and delayed temperature rise were detected with 6/42-h light/ dark and 15/33-h light/dark regimes in the presence of celecoxib and ibuprofen. With a 24/24-h light/dark regime, temperature rise was suppressed in the presence of ibuprofen. There were differences in response to individual NSAIDs between appendix tissue of A. italicum and S. venosum. Mitochondrial energy balance is affected by NSAIDs. There is an interaction between light/dark regime and temperature rise and a relationship between timing mechanism and temperature rise.
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El-Khoury R, Rak M, Bénit P, Jacobs HT, Rustin P. Cyanide resistant respiration and the alternative oxidase pathway: A journey from plants to mammals. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148567. [PMID: 35500614 DOI: 10.1016/j.bbabio.2022.148567] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 04/06/2022] [Accepted: 04/18/2022] [Indexed: 12/19/2022]
Abstract
In a large number of organisms covering all phyla, the mitochondrial respiratory chain harbors, in addition to the conventional elements, auxiliary proteins that confer adaptive metabolic plasticity. The alternative oxidase (AOX) represents one of the most studied auxiliary proteins, initially identified in plants. In contrast to the standard respiratory chain, the AOX mediates a thermogenic cyanide-resistant respiration; a phenomenon that has been of great interest for over 2 centuries in that energy is not conserved when electrons flow through it. Here we summarize centuries of studies starting from the early observations of thermogenicity in plants and the identification of cyanide resistant respiration, to the fascinating discovery of the AOX and its current applications in animals under normal and pathological conditions.
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Affiliation(s)
- Riyad El-Khoury
- American University of Beirut Medical Center, Pathology and Laboratory Medicine Department, Cairo Street, Hamra, Beirut, Lebanon
| | - Malgorzata Rak
- Université Paris Cité, Inserm, Maladies neurodéveloppementales et neurovasculaires, F-75019 Paris, France
| | - Paule Bénit
- Université Paris Cité, Inserm, Maladies neurodéveloppementales et neurovasculaires, F-75019 Paris, France
| | - Howard T Jacobs
- Faculty of Medicine and Health Technology, FI-33014, Tampere University, Finland; Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
| | - Pierre Rustin
- Université Paris Cité, Inserm, Maladies neurodéveloppementales et neurovasculaires, F-75019 Paris, France.
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Sweetman C, Selinski J, Miller TK, Whelan J, Day DA. Legume Alternative Oxidase Isoforms Show Differential Sensitivity to Pyruvate Activation. FRONTIERS IN PLANT SCIENCE 2022; 12:813691. [PMID: 35111186 PMCID: PMC8801435 DOI: 10.3389/fpls.2021.813691] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 12/27/2021] [Indexed: 05/29/2023]
Abstract
Alternative oxidase (AOX) is an important component of the plant respiratory pathway, enabling a route for electrons that bypasses the energy-conserving, ROS-producing complexes of the mitochondrial electron transport chain. Plants contain numerous isoforms of AOX, classified as either AOX1 or AOX2. AOX1 isoforms have received the most attention due to their importance in stress responses across a wide range of species. However, the propensity for at least one isoform of AOX2 to accumulate to very high levels in photosynthetic tissues of all legumes studied to date, suggests that this isoform has specialized roles, but we know little of its properties. Previous studies with sub-mitochondrial particles of soybean cotyledons and roots indicated that differential expression of GmAOX1, GmAOX2A, and GmAOX2D across tissues might confer different activation kinetics with pyruvate. We have investigated this using recombinantly expressed isoforms of soybean AOX in a previously described bacterial system (Selinski et al., 2016, Physiologia Plantarum 157, 264-279). Pyruvate activation kinetics were similar between the two GmAOX2 isoforms but differed substantially from those of GmAOX1, suggesting that selective expression of AOX1 and 2 could determine the level of AOX activity. However, this alone cannot completely explain the differences seen in sub-mitochondrial particles isolated from different legume tissues and possible reasons for this are discussed.
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Affiliation(s)
- Crystal Sweetman
- College of Science and Engineering, Flinders University, Bedford Park, SA, Australia
| | - Jennifer Selinski
- Department of Plant Cell Biology, Botanical Institute, Christian-Albrecht University of Kiel, Kiel, Germany
| | - Troy K. Miller
- College of Science and Engineering, Flinders University, Bedford Park, SA, Australia
| | - James Whelan
- Department of Animal, Plant, and Soil Science, School of Soil Science, La Trobe University, Bundoora, VIC, Australia
| | - David A. Day
- College of Science and Engineering, Flinders University, Bedford Park, SA, Australia
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Sankar TV, Saharay M, Santhosh D, Vishwakarma A, Padmasree K. Structural and Biophysical Characterization of Purified Recombinant Arabidopsis thaliana's Alternative Oxidase 1A (rAtAOX1A): Interaction With Inhibitor(s) and Activator. FRONTIERS IN PLANT SCIENCE 2022; 13:871208. [PMID: 35783971 PMCID: PMC9243770 DOI: 10.3389/fpls.2022.871208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 04/27/2022] [Indexed: 05/14/2023]
Abstract
In higher plants, alternative oxidase (AOX) participates in a cyanide resistant and non-proton motive electron transport pathway of mitochondria, diverging from the ubiquinone pool. The physiological significance of AOX in biotic/abiotic stress tolerance is well-documented. However, its structural and biophysical properties are poorly understood as its crystal structure is not yet revealed in plants. Also, most of the AOX purification processes resulted in a low yield/inactive/unstable form of native AOX protein. The present study aims to characterize the purified rAtAOX1A protein and its interaction with inhibitors, such as salicylhydroxamic acid (SHAM) and n-propyl gallate (n-PG), as well as pyruvate (activator), using biophysical/in silico studies. The rAtAOX1A expressed in E. coli BL21(DE3) cells was functionally characterized by monitoring the respiratory and growth sensitivity of E. coli/pAtAOX1A and E. coli/pET28a to classical mitochondrial electron transport chain (mETC) inhibitors. The rAtAOX1A, which is purified through affinity chromatography and confirmed by western blotting and MALDI-TOF-TOF studies, showed an oxygen uptake activity of 3.86 μmol min-1 mg-1 protein, which is acceptable in non-thermogenic plants. Circular dichroism (CD) studies of purified rAtAOX1A revealed that >50% of the protein content was α-helical and retained its helical absorbance signal (ellipticity) at a wide range of temperature and pH conditions. Further, interaction with SHAM, n-PG, or pyruvate caused significant changes in its secondary structural elements while retaining its ellipticity. Surface plasmon resonance (SPR) studies revealed that both SHAM and n-PG bind reversibly to rAtAOX1A, while docking studies revealed that they bind to the same hydrophobic groove (Met191, Val192, Met195, Leu196, Phe251, and Phe255), to which Duroquinone (DQ) bind in the AtAOX1A. In contrast, pyruvate binds to a pocket consisting of Cys II (Arg174, Tyr175, Gly176, Cys177, Val232, Ala233, Asn294, and Leu313). Further, the mutational docking studies suggest that (i) the Met195 and Phe255 of AtAOX1A are the potential candidates to bind the inhibitor. Hence, this binding pocket could be a 'potential gateway' for the oxidation-reduction process in AtAOX1A, and (ii) Arg174, Gly176, and Cys177 play an important role in binding to the organic acids like pyruvate.
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Affiliation(s)
- Tadiboina Veera Sankar
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Moumita Saharay
- Department of Systems and Computational Biology, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Dharawath Santhosh
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Abhaypratap Vishwakarma
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
- Department of Botany, Deshbandhu College, University of Delhi, New Delhi, India
| | - Kollipara Padmasree
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India
- *Correspondence: Kollipara Padmasree
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Møller IM, Rasmusson AG, Van Aken O. Plant mitochondria - past, present and future. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 108:912-959. [PMID: 34528296 DOI: 10.1111/tpj.15495] [Citation(s) in RCA: 86] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 09/02/2021] [Accepted: 09/06/2021] [Indexed: 06/13/2023]
Abstract
The study of plant mitochondria started in earnest around 1950 with the first isolations of mitochondria from animal and plant tissues. The first 35 years were spent establishing the basic properties of plant mitochondria and plant respiration using biochemical and physiological approaches. A number of unique properties (compared to mammalian mitochondria) were observed: (i) the ability to oxidize malate, glycine and cytosolic NAD(P)H at high rates; (ii) the partial insensitivity to rotenone, which turned out to be due to the presence of a second NADH dehydrogenase on the inner surface of the inner mitochondrial membrane in addition to the classical Complex I NADH dehydrogenase; and (iii) the partial insensitivity to cyanide, which turned out to be due to an alternative oxidase, which is also located on the inner surface of the inner mitochondrial membrane, in addition to the classical Complex IV, cytochrome oxidase. With the appearance of molecular biology methods around 1985, followed by genomics, further unique properties were discovered: (iv) plant mitochondrial DNA (mtDNA) is 10-600 times larger than the mammalian mtDNA, yet it only contains approximately 50% more genes; (v) plant mtDNA has kept the standard genetic code, and it has a low divergence rate with respect to point mutations, but a high recombinatorial activity; (vi) mitochondrial mRNA maturation includes a uniquely complex set of activities for processing, splicing and editing (at hundreds of sites); (vii) recombination in mtDNA creates novel reading frames that can produce male sterility; and (viii) plant mitochondria have a large proteome with 2000-3000 different proteins containing many unique proteins such as 200-300 pentatricopeptide repeat proteins. We describe the present and fairly detailed picture of the structure and function of plant mitochondria and how the unique properties make their metabolism more flexible allowing them to be involved in many diverse processes in the plant cell, such as photosynthesis, photorespiration, CAM and C4 metabolism, heat production, temperature control, stress resistance mechanisms, programmed cell death and genomic evolution. However, it is still a challenge to understand how the regulation of metabolism and mtDNA expression works at the cellular level and how retrograde signaling from the mitochondria coordinates all those processes.
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Affiliation(s)
- Ian Max Møller
- Department of Molecular Biology and Genetics, Aarhus University, Forsøgsvej 1, DK-4200, Slagelse, Denmark
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Dourmap C, Roque S, Morin A, Caubrière D, Kerdiles M, Béguin K, Perdoux R, Reynoud N, Bourdet L, Audebert PA, Moullec JL, Couée I. Stress signalling dynamics of the mitochondrial electron transport chain and oxidative phosphorylation system in higher plants. ANNALS OF BOTANY 2020; 125:721-736. [PMID: 31711195 PMCID: PMC7182585 DOI: 10.1093/aob/mcz184] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2019] [Accepted: 11/07/2019] [Indexed: 05/23/2023]
Abstract
BACKGROUND Mitochondria play a diversity of physiological and metabolic roles under conditions of abiotic or biotic stress. They may be directly subjected to physico-chemical constraints, and they are also involved in integrative responses to environmental stresses through their central position in cell nutrition, respiration, energy balance and biosyntheses. In plant cells, mitochondria present various biochemical peculiarities, such as cyanide-insensitive alternative respiration, and, besides integration with ubiquitous eukaryotic compartments, their functioning must be coupled with plastid functioning. Moreover, given the sessile lifestyle of plants, their relative lack of protective barriers and present threats of climate change, the plant cell is an attractive model to understand the mechanisms of stress/organelle/cell integration in the context of environmental stress responses. SCOPE The involvement of mitochondria in this integration entails a complex network of signalling, which has not been fully elucidated, because of the great diversity of mitochondrial constituents (metabolites, reactive molecular species and structural and regulatory biomolecules) that are linked to stress signalling pathways. The present review analyses the complexity of stress signalling connexions that are related to the mitochondrial electron transport chain and oxidative phosphorylation system, and how they can be involved in stress perception and transduction, signal amplification or cell stress response modulation. CONCLUSIONS Plant mitochondria are endowed with a diversity of multi-directional hubs of stress signalling that lead to regulatory loops and regulatory rheostats, whose functioning can amplify and diversify some signals or, conversely, dampen and reduce other signals. Involvement in a wide range of abiotic and biotic responses also implies that mitochondrial stress signalling could result in synergistic or conflicting outcomes during acclimation to multiple and complex stresses, such as those arising from climate change.
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Affiliation(s)
- Corentin Dourmap
- Université de Rennes 1, Department of Life Sciences and Environment, Campus de Beaulieu, Rennes, France
| | - Solène Roque
- Université de Rennes 1, Department of Life Sciences and Environment, Campus de Beaulieu, Rennes, France
| | - Amélie Morin
- Université de Rennes 1, Department of Life Sciences and Environment, Campus de Beaulieu, Rennes, France
| | - Damien Caubrière
- Université de Rennes 1, Department of Life Sciences and Environment, Campus de Beaulieu, Rennes, France
| | - Margaux Kerdiles
- Université de Rennes 1, Department of Life Sciences and Environment, Campus de Beaulieu, Rennes, France
- Université de Rennes 1, CNRS ECOBIO (Ecosystems-Biodiversity-Evolution) – UMR 6553, Rennes, France
| | - Kyllian Béguin
- Université de Rennes 1, Department of Life Sciences and Environment, Campus de Beaulieu, Rennes, France
- Université de Rennes 1, CNRS ECOBIO (Ecosystems-Biodiversity-Evolution) – UMR 6553, Rennes, France
| | - Romain Perdoux
- Université de Rennes 1, Department of Life Sciences and Environment, Campus de Beaulieu, Rennes, France
| | - Nicolas Reynoud
- Université de Rennes 1, Department of Life Sciences and Environment, Campus de Beaulieu, Rennes, France
| | - Lucile Bourdet
- Université de Rennes 1, Department of Life Sciences and Environment, Campus de Beaulieu, Rennes, France
| | - Pierre-Alexandre Audebert
- Université de Rennes 1, Department of Life Sciences and Environment, Campus de Beaulieu, Rennes, France
| | - Julien Le Moullec
- Université de Rennes 1, Department of Life Sciences and Environment, Campus de Beaulieu, Rennes, France
| | - Ivan Couée
- Université de Rennes 1, Department of Life Sciences and Environment, Campus de Beaulieu, Rennes, France
- Université de Rennes 1, CNRS ECOBIO (Ecosystems-Biodiversity-Evolution) – UMR 6553, Rennes, France
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7
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Sweetman C, Waterman CD, Rainbird BM, Smith PMC, Jenkins CD, Day DA, Soole KL. AtNDB2 Is the Main External NADH Dehydrogenase in Mitochondria and Is Important for Tolerance to Environmental Stress. PLANT PHYSIOLOGY 2019; 181:774-788. [PMID: 31409698 PMCID: PMC6776847 DOI: 10.1104/pp.19.00877] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 07/23/2019] [Indexed: 05/02/2023]
Abstract
In addition to the classical electron transport pathway coupled to ATP synthesis, plant mitochondria have an alternative pathway that involves type II NAD(P)H dehydrogenases (NDs) and alternative oxidase (AOX). This alternative pathway participates in thermogenesis in select organs of some species and is thought to help prevent cellular damage during exposure to environmental stress. Here, we investigated the function and role of one alternative path component, AtNDB2, using a transgenic approach in Arabidopsis (Arabidopsis thaliana). Disruption of AtNDB2 expression via T-DNA insertion led to a 90% decrease of external NADH oxidation in isolated mitochondria. Overexpression of AtNDB2 led to increased AtNDB2 protein abundance in mitochondria but did not enhance external NADH oxidation significantly unless AtAOX1A was concomitantly overexpressed and activated, demonstrating a functional link between these enzymes. Plants lacking either AtAOX1A or AtNDB2 were more sensitive to combined drought and elevated light treatments, whereas plants overexpressing these components showed increased tolerance and capacity for poststress recovery. We conclude that AtNDB2 is the predominant external NADH dehydrogenase in mitochondria and together with AtAOX1A forms a complete, functional, nonphosphorylating pathway of electron transport, whose operation enhances tolerance to environmental stress. This study demonstrates that at least one of the alternative NDs, as well as AOX, are important for the stress response.
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Affiliation(s)
- Crystal Sweetman
- College of Science and Engineering, Flinders University of South Australia, Adelaide, South Australia 5042, Australia
| | - Christopher D Waterman
- College of Science and Engineering, Flinders University of South Australia, Adelaide, South Australia 5042, Australia
| | - Barry M Rainbird
- College of Science and Engineering, Flinders University of South Australia, Adelaide, South Australia 5042, Australia
| | - Penelope M C Smith
- Department of Animal, Plant, and Soil Sciences, School of Life Sciences, Latrobe University, Bundoora, Victoria 3083, Australia
| | - Colin D Jenkins
- College of Science and Engineering, Flinders University of South Australia, Adelaide, South Australia 5042, Australia
| | - David A Day
- College of Science and Engineering, Flinders University of South Australia, Adelaide, South Australia 5042, Australia
| | - Kathleen L Soole
- College of Science and Engineering, Flinders University of South Australia, Adelaide, South Australia 5042, Australia
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8
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Ferraz P, Cássio F, Lucas C. Potential of Yeasts as Biocontrol Agents of the Phytopathogen Causing Cacao Witches' Broom Disease: Is Microbial Warfare a Solution? Front Microbiol 2019; 10:1766. [PMID: 31417539 PMCID: PMC6685038 DOI: 10.3389/fmicb.2019.01766] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 07/17/2019] [Indexed: 11/13/2022] Open
Abstract
Plant diseases caused by fungal pathogens are responsible for major crop losses worldwide, with a significant socio-economic impact on the life of millions of people who depend on agriculture-exclusive economy. This is the case of the Witches’ Broom Disease (WBD) affecting cacao plant and fruit in South and Central America. The severity and extent of this disease is prospected to impact the growing global chocolate market in a few decades. WBD is caused by the basidiomycete fungus Moniliophthora perniciosa. The methods used to contain the fungus mainly rely on chemical fungicides, such as copper-based compounds or azoles. Not only are these highly ineffective, but also their utilization is increasingly restricted by the cacao industry, in part because it promotes fungal resistance, in part related to consumers’ health concerns and environmental awareness. Therefore, the disease is being currently tentatively controlled through phytosanitary pruning, although the full removal of infected plant material is impossible and the fungus maintains persistent inoculum in the soil, or using an endophytic fungal parasite of Moniliophthora perniciosa which production is not sustainable. The growth of Moniliophthora perniciosa was reported as being antagonized in vitro by some yeasts, which suggests that they could be used as biological control agents, suppressing the fungus multiplication and containing its spread. Concurrently, some yeast-based products are used in the protection of fruits from postharvest fungal spoilage, and the extension of diverse food products shelf-life. These successful applications suggest that yeasts can be regarded a serious alternative also in the pre-harvest management of WBD and other fungal plant diseases. Yeasts’ GRAS (Generally Recognized as Safe) nature adds to their appropriateness for field application, not raising major ecological concerns as do the present more aggressive approaches. Importantly, mitigating WBD, in a sustainable manner, would predictably have a high socioeconomic impact, contributing to diminish poverty in the cacao-producing rural communities severely affected by the disease. This review discusses the importance/advantages and the challenges that such a strategy would have for WBD containment, and presents the available information on the molecular and cellular mechanisms underlying fungi antagonism by yeasts.
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Affiliation(s)
- Pedro Ferraz
- Institute of Science and Innovation for Bio-Sustainability, University of Minho, Braga, Portugal.,Centre of Molecular and Environmental Biology, University of Minho, Braga, Portugal
| | - Fernanda Cássio
- Institute of Science and Innovation for Bio-Sustainability, University of Minho, Braga, Portugal.,Centre of Molecular and Environmental Biology, University of Minho, Braga, Portugal
| | - Cândida Lucas
- Institute of Science and Innovation for Bio-Sustainability, University of Minho, Braga, Portugal.,Centre of Molecular and Environmental Biology, University of Minho, Braga, Portugal
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Ito-Inaba Y, Sato M, Sato MP, Kurayama Y, Yamamoto H, Ohata M, Ogura Y, Hayashi T, Toyooka K, Inaba T. Alternative Oxidase Capacity of Mitochondria in Microsporophylls May Function in Cycad Thermogenesis. PLANT PHYSIOLOGY 2019; 180:743-756. [PMID: 30918084 PMCID: PMC6548267 DOI: 10.1104/pp.19.00150] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 03/12/2019] [Indexed: 06/09/2023]
Abstract
Cone thermogenesis is a widespread phenomenon in cycads and may function to promote volatile emissions that affect pollinator behavior. Given their large population size and intense and durable heat-producing effects, cycads are important organisms for comprehensive studies of plant thermogenesis. However, knowledge of mitochondrial morphology and function in cone thermogenesis is limited. Therefore, we investigated these mitochondrial properties in the thermogenic cycad species Cycas revoluta Male cones generated heat even in cool weather conditions. Female cones produced heat, but to a lesser extent than male cones. Ultrastructural analyses of the two major tissues of male cones, microsporophylls and microsporangia, revealed the existence of a population of mitochondria with a distinct morphology in the microsporophylls. In these cells, we observed large mitochondria (cross-sectional area of 2 μm2 or more) with a uniform matrix density that occupied >10% of the total mitochondrial volume. Despite the size difference, many nonlarge mitochondria (cross-sectional area <2 μm2) also exhibited a shape and a matrix density similar to those of large mitochondria. Alternative oxidase (AOX) capacity and expression levels in microsporophylls were much higher than those in microsporangia. The AOX genes expressed in male cones revealed two different AOX complementary DNA sequences: CrAOX1 and CrAOX2 The expression level of CrAOX1 mRNA in the microsporophylls was 100 times greater than that of CrAOX2 mRNA. Collectively, these results suggest that distinctive mitochondrial morphology and CrAOX1-mediated respiration in microsporophylls might play a role in cycad cone thermogenesis.
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Affiliation(s)
- Yasuko Ito-Inaba
- Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, 1-1 Gakuenkibanadai-nishi, Miyazaki 889-2192, Japan
| | - Mayuko Sato
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Mitsuhiko P Sato
- Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Yuya Kurayama
- Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, 1-1 Gakuenkibanadai-nishi, Miyazaki 889-2192, Japan
| | - Haruna Yamamoto
- Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, 1-1 Gakuenkibanadai-nishi, Miyazaki 889-2192, Japan
| | - Mizuki Ohata
- Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, 1-1 Gakuenkibanadai-nishi, Miyazaki 889-2192, Japan
| | - Yoshitoshi Ogura
- Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Tetsuya Hayashi
- Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Kiminori Toyooka
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Takehito Inaba
- Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, 1-1 Gakuenkibanadai-nishi, Miyazaki 889-2192, Japan
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10
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Sweetman C, Soole KL, Jenkins CLD, Day DA. Genomic structure and expression of alternative oxidase genes in legumes. PLANT, CELL & ENVIRONMENT 2019; 42:71-84. [PMID: 29424926 DOI: 10.1111/pce.13161] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 01/22/2018] [Accepted: 01/25/2018] [Indexed: 05/26/2023]
Abstract
Mitochondria isolated from chickpea (Cicer arietinum) possess substantial alternative oxidase (AOX) activity, even in non-stressed plants, and one or two AOX protein bands were detected immunologically, depending on the organ. Four different AOX isoforms were identified in the chickpea genome: CaAOX1 and CaAOX2A, B and D. CaAOX2A was the most highly expressed form and was strongly expressed in photosynthetic tissues, whereas CaAOX2D was found in all organs examined. These results are very similar to those of previous studies with soybean and siratro. Searches of available databases showed that this pattern of AOX genes and their expression was common to at least 16 different legume species. The evolution of the legume AOX gene family is discussed, as is the in vivo impact of an inherently high AOX capacity in legumes on growth and responses to environmental stresses.
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Affiliation(s)
- Crystal Sweetman
- Australian Research Council Industrial Transformation Research Hub, Legumes for Sustainable Agriculture, College of Science and Engineering, Flinders University of South Australia, Adelaide, South Australia, GPO Box 2001, Australia
| | - Kathleen L Soole
- Australian Research Council Industrial Transformation Research Hub, Legumes for Sustainable Agriculture, College of Science and Engineering, Flinders University of South Australia, Adelaide, South Australia, GPO Box 2001, Australia
| | - Colin L D Jenkins
- Australian Research Council Industrial Transformation Research Hub, Legumes for Sustainable Agriculture, College of Science and Engineering, Flinders University of South Australia, Adelaide, South Australia, GPO Box 2001, Australia
| | - David A Day
- Australian Research Council Industrial Transformation Research Hub, Legumes for Sustainable Agriculture, College of Science and Engineering, Flinders University of South Australia, Adelaide, South Australia, GPO Box 2001, Australia
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11
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El-Khoury R, Kaulio E, Lassila KA, Crowther DC, Jacobs HT, Rustin P. Expression of the alternative oxidase mitigates beta-amyloid production and toxicity in model systems. Free Radic Biol Med 2016; 96:57-66. [PMID: 27094492 DOI: 10.1016/j.freeradbiomed.2016.04.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 04/05/2016] [Accepted: 04/09/2016] [Indexed: 12/13/2022]
Abstract
Mitochondrial dysfunction has been widely associated with the pathology of Alzheimer's disease, but there is no consensus on whether it is a cause or consequence of disease, nor on the precise mechanism(s). We addressed these issues by testing the effects of expressing the alternative oxidase AOX from Ciona intestinalis, in different models of AD pathology. AOX can restore respiratory electron flow when the cytochrome segment of the mitochondrial respiratory chain is inhibited, supporting ATP synthesis, maintaining cellular redox homeostasis and mitigating excess superoxide production at respiratory complexes I and III. In human HEK293-derived cells, AOX expression decreased the production of beta-amyloid peptide resulting from antimycin inhibition of respiratory complex III. Because hydrogen peroxide was neither a direct product nor substrate of AOX, the ability of AOX to mimic antioxidants in this assay must be indirect. In addition, AOX expression was able to partially alleviate the short lifespan of Drosophila models neuronally expressing human beta-amyloid peptides, whilst abrogating the induction of markers of oxidative stress. Our findings support the idea of respiratory chain dysfunction and excess ROS production as both an early step and as a pathologically meaningful target in Alzheimer's disease pathogenesis, supporting the concept of a mitochondrial vicious cycle underlying the disease.
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Affiliation(s)
- Riyad El-Khoury
- INSERM UMR 1141 and Université Paris 7, Faculté de Médecine Denis Diderot, Hôpital Robert Debré, 48, Boulevard Sérurier, 75019 Paris, France; American University of Beirut Medical Center, Department of Pathology and Laboratory Medicine, Cairo Street, Hamra, Beirut, Lebanon
| | - Eveliina Kaulio
- BioMediTech and Tampere University Hospital, FI-33014 University of Tampere, Finland
| | - Katariina A Lassila
- BioMediTech and Tampere University Hospital, FI-33014 University of Tampere, Finland
| | - Damian C Crowther
- Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK and MedImmune Ltd, Aaron Klug Building, Granta Park, Cambridge CB21 6GH, UK
| | - Howard T Jacobs
- BioMediTech and Tampere University Hospital, FI-33014 University of Tampere, Finland; Institute of Biotechnology, FI-00014 University of Helsinki, Finland.
| | - Pierre Rustin
- INSERM UMR 1141 and Université Paris 7, Faculté de Médecine Denis Diderot, Hôpital Robert Debré, 48, Boulevard Sérurier, 75019 Paris, France
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12
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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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13
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Shabnam N, Sharmila P, Sharma A, Strasser RJ, Pardha-Saradhi P. Mitochondrial electron transport protects floating leaves of long leaf pondweed (Potamogeton nodosus Poir) against photoinhibition: comparison with submerged leaves. PHOTOSYNTHESIS RESEARCH 2015; 125:305-319. [PMID: 25366828 DOI: 10.1007/s11120-014-0051-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 10/16/2014] [Indexed: 06/04/2023]
Abstract
Investigations were carried to unravel mechanism(s) for higher tolerance of floating over submerged leaves of long leaf pondweed (Potamogeton nodosus Poir) against photoinhibition. Chloroplasts from floating leaves showed ~5- and ~6.4-fold higher Photosystem (PS) I (reduced dichlorophenol-indophenol → methyl viologen → O2) and PS II (H2O → parabenzoquine) activities over those from submerged leaves. The saturating rate (V max) of PS II activity of chloroplasts from floating and submerged leaves reached at ~600 and ~230 µmol photons m(-2) s(-1), respectively. Photosynthetic electron transport rate in floating leaves was over 5-fold higher than in submerged leaves. Further, floating leaves, as compared to submerged leaves, showed higher F v/F m (variable to maximum chlorophyll fluorescence, a reflection of PS II efficiency), as well as a higher potential to withstand photoinhibitory damage by high light (1,200 µmol photons m(-2) s(-1)). Cells of floating leaves had not only higher mitochondria to chloroplast ratio, but also showed many mitochondria in close vicinity of chloroplasts. Electron transport (NADH → O2; succinate → O2) in isolated mitochondria of floating leaves was sensitive to both cyanide (CN(-)) and salicylhydroxamic acid (SHAM), whereas those in submerged leaves were sensitive to CN(-), but virtually insensitive to SHAM, revealing the presence of alternative oxidase in mitochondria of floating, but not of submerged, leaves. Further, the potential of floating leaves to withstand photoinhibitory damage was significantly reduced in the presence of CN(-) and SHAM, individually and in combination. Our experimental results establish that floating leaves possess better photosynthetic efficiency and capacity to withstand photoinhibition compared to submerged leaves; and mitochondria play a pivotal role in protecting photosynthetic machinery of floating leaves against photoinhibition, most likely by oxidation of NAD(P)H and reduction of O2.
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Affiliation(s)
- Nisha Shabnam
- Department of Environmental Studies, University of Delhi, Delhi, 110007, India
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14
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Kodru S, Malavath T, Devadasu E, Nellaepalli S, Stirbet A, Subramanyam R. The slow S to M rise of chlorophyll a fluorescence reflects transition from state 2 to state 1 in the green alga Chlamydomonas reinhardtii. PHOTOSYNTHESIS RESEARCH 2015; 125:219-31. [PMID: 25663564 DOI: 10.1007/s11120-015-0084-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2014] [Accepted: 01/08/2015] [Indexed: 05/03/2023]
Abstract
The green alga Chlamydomonas (C.) reinhardtii is a model organism for photosynthesis research. State transitions regulate redistribution of excitation energy between photosystem I (PS I) and photosystem II (PS II) to provide balanced photosynthesis. Chlorophyll (Chl) a fluorescence induction (the so-called OJIPSMT transient) is a signature of several photosynthetic reactions. Here, we show that the slow (seconds to minutes) S to M fluorescence rise is reduced or absent in the stt7 mutant (which is locked in state 1) in C. reinhardtii. This suggests that the SM rise in wild type C. reinhardtii may be due to state 2 (low fluorescence state; larger antenna in PS I) to state 1 (high fluorescence state; larger antenna in PS II) transition, and thus, it can be used as an efficient and quick method to monitor state transitions in algae, as has already been shown in cyanobacteria (Papageorgiou et al. 1999, 2007; Kaňa et al. 2012). We also discuss our results on the effects of (1) 3-(3,4-dichlorophenyl)-1,4-dimethyl urea, an inhibitor of electron transport; (2) n-propyl gallate, an inhibitor of alternative oxidase (AOX) in mitochondria and of plastid terminal oxidase in chloroplasts; (3) salicylhydroxamic acid, an inhibitor of AOX in mitochondria; and (4) carbonyl cyanide p-trifluoromethoxyphenylhydrazone, an uncoupler of phosphorylation, which dissipates proton gradient across membranes. Based on the data presented in this paper, we conclude that the slow PSMT fluorescence transient in C. reinhardtii is due to the superimposition of, at least, two phenomena: qE dependent non-photochemical quenching of the excited state of Chl, and state transitions.
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Affiliation(s)
- Sireesha Kodru
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500 046, India
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15
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Mróz TL, Havey MJ, Bartoszewski G. Cucumber Possesses a Single Terminal Alternative Oxidase Gene That is Upregulated by Cold Stress and in the Mosaic (MSC) Mitochondrial Mutants. PLANT MOLECULAR BIOLOGY REPORTER 2015; 33:1893-1906. [PMID: 26752808 PMCID: PMC4695503 DOI: 10.1007/s11105-015-0883-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Alternative oxidase (AOX) is a mitochondrial terminal oxidase which is responsible for an alternative route of electron transport in the respiratory chain. This nuclear-encoded enzyme is involved in a major path of survival under adverse conditions by transfer of electrons from ubiquinol instead of the main cytochrome pathway. AOX protects against unexpected inhibition of the cytochrome c oxidase pathway and plays an important role in stress tolerance. Two AOX subfamilies (AOX1 and AOX2) exist in higher plants and are usually encoded by small gene families. In this study, genome-wide searches and cloning were completed to identify and characterize AOX genes in cucumber (Cucumis sativus L.). Our results revealed that cucumber possesses no AOX1 gene(s) and only a single AOX2 gene located on chromosome 4. Expression studies showed that AOX2 in wild-type cucumber is constitutively expressed at low levels and is upregulated by cold stress. AOX2 transcripts and protein were detected in leaves and flowers of wild-type plants, with higher levels in the three independently derived mosaic (MSC) mitochondrial mutants. Because cucumber possesses a single AOX gene and its expression increases under cold stress and in the MSC mutants, this plant is a unique and intriguing model to study AOX expression and regulation particularly in the context of mitochondria-to-nucleus retrograde signaling.
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Affiliation(s)
- Tomasz L. Mróz
- />Department of Plant Genetics, Breeding and Biotechnology, Faculty of Horticulture, Biotechnology and Landscape Architecture, Warsaw University of Life Sciences, ul. Nowoursynowska 159, 02-776 Warsaw, Poland
| | - Michael J. Havey
- />Agricultural Research Service, U.S. Department of Agriculture, Vegetable Crops Unit, Department of Horticulture, University of Wisconsin, 1575 Linden Dr., Madison, WI 53706 USA
| | - Grzegorz Bartoszewski
- />Department of Plant Genetics, Breeding and Biotechnology, Faculty of Horticulture, Biotechnology and Landscape Architecture, Warsaw University of Life Sciences, ul. Nowoursynowska 159, 02-776 Warsaw, Poland
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16
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El-Khoury R, Kemppainen KK, Dufour E, Szibor M, Jacobs HT, Rustin P. Engineering the alternative oxidase gene to better understand and counteract mitochondrial defects: state of the art and perspectives. Br J Pharmacol 2014; 171:2243-9. [PMID: 24383965 DOI: 10.1111/bph.12570] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 10/25/2013] [Accepted: 11/18/2013] [Indexed: 12/22/2022] Open
Abstract
Mitochondrial disorders are nowadays recognized as impinging on most areas of medicine. They include specific and widespread organ involvement, including both tissue degeneration and tumour formation. Despite the spectacular progresses made in the identification of their underlying molecular basis, effective therapy remains a distant goal. Our still rudimentary understanding of the pathophysiological mechanisms by which these diseases arise constitutes an obstacle to developing any rational treatments. In this context, the idea of using a heterologous gene, encoding a supplemental oxidase otherwise absent from mammals, potentially bypassing the defective portion of the respiratory chain, was proposed more than 10 years ago. The recent progress made in the expression of the alternative oxidase in a wide range of biological systems and disease conditions reveals great potential benefit, considering the broad impact of mitochondrial diseases. This review addresses the state of the art and the perspectives that can be now envisaged by using this strategy.
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Affiliation(s)
- Riyad El-Khoury
- INSERM UMR 1141, Paris, France; Université Paris 7, Paris, France
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17
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Abstract
Our previous studies have described the purification and characterization of a novel plant NAD(P)-reductase like protein (RL) from the thermogenic appendix of the Sauromatum guttatum inflorescence. RL is mainly located in cytoplasm of thermogenic plants and it can act like a bistable switch. It adopts a compact conformation during heat-production and a more expanded conformation when heat is not generated. Addition of salicylic acid, a natural thermogenic inducer, at picomolar concentration to a solution of purified RL induced a discontinuous volume phase transition in which the volume of RL in the oligomeric form expanded and shrunk repeatedly every 4-5 min. In the present study using ESI-MS analysis we have demonstrated the existence of RL in the human SK-N-SH cell line and in mouse brain tissue. The molecular mass of human RL is in the same range as of its plant counterpart, 34,140 ± 34 Da. The charge state distribution of the human RL is identical to its plant counterpart from the Sauromatum appendix during heat-production. Human RL was present in the compact state when it was purified from the SK-N-SH cell line When these cells were treated with salicylic acid (10 μM) a shift to a much more compact conformation was observed. It seems that the potential of RL to respond to salicylic acid was conserved. These results may reveal the existence of a thermoregulation system that is evolutionarily conserved and is operating by conformational changes. This discovery may also represent an opportunity for a better understanding of some of the diverse functions of salicylic acid and aspirin in plants and humans.
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18
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Moore AL, Shiba T, Young L, Harada S, Kita K, Ito K. Unraveling the heater: new insights into the structure of the alternative oxidase. ANNUAL REVIEW OF PLANT BIOLOGY 2013; 64:637-63. [PMID: 23638828 DOI: 10.1146/annurev-arplant-042811-105432] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The alternative oxidase is a membrane-bound ubiquinol oxidase found in the majority of plants as well as many fungi and protists, including pathogenic organisms such as Trypanosoma brucei. It catalyzes a cyanide- and antimycin-A-resistant oxidation of ubiquinol and the reduction of oxygen to water, short-circuiting the mitochondrial electron-transport chain prior to proton translocation by complexes III and IV, thereby dramatically reducing ATP formation. In plants, it plays a key role in cellular metabolism, thermogenesis, and energy homeostasis and is generally considered to be a major stress-induced protein. We describe recent advances in our understanding of this protein's structure following the recent successful crystallization of the alternative oxidase from T. brucei. We focus on the nature of the active site and ubiquinol-binding channels and propose a mechanism for the reduction of oxygen to water based on these structural insights. We also consider the regulation of activity at the posttranslational and retrograde levels and highlight challenges for future research.
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Affiliation(s)
- Anthony L Moore
- Biochemistry and Molecular Biology, School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom.
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19
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Thomazella DPT, Teixeira PJPL, Oliveira HC, Saviani EE, Rincones J, Toni IM, Reis O, Garcia O, Meinhardt LW, Salgado I, Pereira GAG. The hemibiotrophic cacao pathogen Moniliophthora perniciosa depends on a mitochondrial alternative oxidase for biotrophic development. THE NEW PHYTOLOGIST 2012; 194:1025-1034. [PMID: 22443281 PMCID: PMC3415677 DOI: 10.1111/j.1469-8137.2012.04119.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The tropical pathogen Moniliophthora perniciosa causes witches' broom disease in cacao. As a hemibiotrophic fungus, it initially colonizes the living host tissues (biotrophic phase), and later grows over the dead plant (necrotrophic phase). Little is known about the mechanisms that promote these distinct fungal phases or mediate the transition between them. An alternative oxidase gene (Mp-aox) was identified in the M. perniciosa genome and its expression was analyzed througout the fungal life cycle. In addition, the effects of inhibitors of the cytochrome-dependent respiratory chain (CRC) and alternative oxidase (AOX) were evaluated on the in vitro development of M. perniciosa. Larger numbers of Mp-aox transcripts were observed in the biotrophic hyphae, which accordingly showed elevated sensitivity to AOX inhibitors. More importantly, the inhibition of CRC prevented the transition from the biotrophic to the necrotrophic phase, and the combined use of a CRC and AOX inhibitor completely halted fungal growth. On the basis of these results, a novel mechanism is presented in which AOX plays a role in the biotrophic development of M. perniciosa and regulates the transition to its necrotrophic stage. Strikingly, this model correlates well with the infection strategy of animal pathogens, particularly Trypanosoma brucei, which uses AOX as a strategy for pathogenicity.
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Affiliation(s)
- Daniela P T Thomazella
- Laboratório de Genômica e Expressão, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP 13083-970, Brazil
| | - Paulo José P L Teixeira
- Laboratório de Genômica e Expressão, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP 13083-970, Brazil
| | - Halley C Oliveira
- Departamento de Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP 13083-970, Brazil
| | - Elzira E Saviani
- Departamento de Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP 13083-970, Brazil
| | - Johana Rincones
- Laboratório de Genômica e Expressão, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP 13083-970, Brazil
| | - Isabella M Toni
- Laboratório de Genômica e Expressão, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP 13083-970, Brazil
| | - Osvaldo Reis
- Laboratório de Genômica e Expressão, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP 13083-970, Brazil
| | - Odalys Garcia
- Laboratório de Genômica e Expressão, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP 13083-970, Brazil
| | - Lyndel W Meinhardt
- Sustainable Perennial Crops Laboratory, USDA-ARS, 10300 Baltimore Ave., Bldg. 001, Beltsville, MD 20705-2350, USA
| | - Ione Salgado
- Departamento de Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP 13083-970, Brazil
| | - Gonçalo A G Pereira
- Laboratório de Genômica e Expressão, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP 13083-970, Brazil
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20
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Florez-Sarasa I, Flexas J, Rasmusson AG, Umbach AL, Siedow JN, Ribas-Carbo M. In vivo cytochrome and alternative pathway respiration in leaves of Arabidopsis thaliana plants with altered alternative oxidase under different light conditions. PLANT, CELL & ENVIRONMENT 2011; 34:1373-1383. [PMID: 21486306 DOI: 10.1111/j.1365-3040.2011.02337.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The in vivo activity of the alternative pathway (ν(alt)) has been studied using the oxygen isotope fractionation method in leaves of Arabidopsis thaliana modified for the expression of the AtAOX1a gene by anti-sense (AS-12) or overexpression (XX-2). Under non-stressful conditions, ν(alt) was similar in all plant lines regardless of its different alternative pathway capacities (V(alt)). Total leaf respiration (V(t)) and V(alt) were directly related to growth light conditions while electron partitioning between the cytochrome pathway (CP) and alternative pathway (AP) was unchanged by light levels. Interestingly, the AP functioned at full capacity in anti-sense plants under both growth light conditions. The role of the AP in response to a high light stress induced by short-term high light treatment (HLT) was also studied. In wild type and XX-2, both CP and AP rates increased proportionally after HLT while in AS-12, where the AP was unable to increase its rate, the CP accommodated all the increase in respiration. The results obtained under high light stress suggest that flexibility in the response of the mitochondrial electron transport chain is involved in sustaining photosynthetic rates in response to this stress while the saturated AP in AS-12 plants may contribute to the observed increase in photoinhibition.
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Affiliation(s)
- Igor Florez-Sarasa
- Grup de Recerca en Biologia de les Plantes en Condicions Mediterranies, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, 07122 Palma de Mallorca, Spain
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21
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A novel functional element in the N-terminal region of Arum concinnatum alternative oxidase is indispensable for catalytic activity of the enzyme in HeLa cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1797:20-8. [PMID: 19643077 DOI: 10.1016/j.bbabio.2009.07.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Revised: 07/14/2009] [Accepted: 07/21/2009] [Indexed: 11/20/2022]
Abstract
Alternative oxidase (AOX) is a quinol-oxygen oxidoreductase, which is known to possess a dicarboxylate diiron reaction center held in structurally postulated alpha-helical bundle. However, little is known about the structural or functional features of its N-terminal region in any organism, with the exception of a regulatory cysteine residue (CysI) in angiosperm plants. Here, we show that transcripts of two AOX1 isozymes (AcoAOX1a and AcoAOX1b) are coexpressed in thermogenic appendices of Arum concinnatum, while their enzymatic activities seem to be distinct. Namely, AcoAOX1a, an abundantly expressed transcript in vivo, shows an apparent cyanide-insensitive and n-propyl gallate-sensitive respiration during ectopic expression of the protein in HeLa cells, whereas AcoAOX1b exhibits a lower transcript expression, and appears to be totally inactive as AOX at the protein level. Our functional analyses further reveal that an E83K substitution in AcoAOX1b, which is located far upstream of CysI in the N-terminal region, is the cause of this loss of function. These results suggest the presence of a naturally occurring inactive AOX homologue in thermogenic plants. Accordingly, our results further imply that the N-terminal region of the AOX protein functionally contributes to the dynamic activities of respiratory control within the mitochondria.
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22
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Oliver SN, Lunn JE, Urbanczyk-Wochniak E, Lytovchenko A, van Dongen JT, Faix B, Schmälzlin E, Fernie AR, Geigenberger P. Decreased expression of cytosolic pyruvate kinase in potato tubers leads to a decline in pyruvate resulting in an in vivo repression of the alternative oxidase. PLANT PHYSIOLOGY 2008; 148:1640-54. [PMID: 18829984 PMCID: PMC2577264 DOI: 10.1104/pp.108.126516] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Accepted: 09/24/2008] [Indexed: 05/18/2023]
Abstract
The aim of this work was to investigate the effect of decreased cytosolic pyruvate kinase (PKc) on potato (Solanum tuberosum) tuber metabolism. Transgenic potato plants with strongly reduced levels of PKc were generated by RNA interference gene silencing under the control of a tuber-specific promoter. Metabolite profiling showed that decreased PKc activity led to a decrease in the levels of pyruvate and some other organic acids involved in the tricarboxylic acid cycle. Flux analysis showed that this was accompanied by changes in carbon partitioning, with carbon flux being diverted from glycolysis toward starch synthesis. However, this metabolic shift was relatively small and hence did not result in enhanced starch levels in the tubers. Although total respiration rates and the ATP to ADP ratio were largely unchanged, transgenic tubers showed a strong decrease in the levels of alternative oxidase (AOX) protein and a corresponding decrease in the capacity of the alternative pathway of respiration. External feeding of pyruvate to tuber tissue or isolated mitochondria resulted in activation of the AOX pathway, both in the wild type and the PKc transgenic lines, providing direct evidence for the regulation of AOX by changes in pyruvate levels. Overall, these results provide evidence for a crucial role of PKc in the regulation of pyruvate levels as well as the level of the AOX in heterotrophic plant tissue, and furthermore reveal that these parameters are interlinked in vivo.
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Affiliation(s)
- Sandra N Oliver
- Max-Planck Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany
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23
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Kende H. Remembering Lee McIntosh (1949-2004), a pioneer in the molecular biology of chloroplast and mitochondrion function. PHOTOSYNTHESIS RESEARCH 2006; 87:247-51. [PMID: 16479363 DOI: 10.1007/s11120-006-9037-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/25/2005] [Indexed: 05/06/2023]
Affiliation(s)
- Hans Kende
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48823, USA.
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24
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Gray GR, Villarimo AR, Whitehead CL, McIntosh L. Transgenic tobacco (Nicotiana tabacum L.) plants with increased expression levels of mitochondrial NADP+-dependent isocitrate dehydrogenase: evidence implicating this enzyme in the redox activation of the alternative oxidase. PLANT & CELL PHYSIOLOGY 2004; 45:1413-25. [PMID: 15564525 DOI: 10.1093/pcp/pch162] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Many metabolic reactions are coupled to NADPH in the mitochondrial matrix, including those involved in thiol group reduction. One enzyme linked to such processes is mitochondrial NADP+-dependent isocitrate dehydrogenase (mtICDH; EC 1.1.1.42), although the precise role of this enzyme is not yet known. Previous work has implicated mtICDH as part of a biochemical mechanism to reductively activate the alternative oxidase (AOX). We have partially purified mtICDH from tobacco (Nicotiana tabacum L. cv. Petit Havana SR1) cell suspension cultures and localized this to a 46-kDa protein on SDS-PAGE, which was verified by peptide sequencing. In the inflorescence of the aroid Sauromatum guttatum Schott (voodoo lily), mtICDH appears to be developmentally regulated, presenting maximal specific activity during the thermogenic period of anthesis when the capacity for AOX respiration is also at its peak. Transgenic tobacco plants were generated that overexpress mtICDH and lines were obtained that demonstrated up to a 7-fold increase in mtICDH activity. In isolated mitochondria, this resulted in a measurable increase in the reductive activation of AOX in comparison with wild type. When examined in planta in response to citrate feeding, a strong conversion of AOX from its oxidized to its reduced form was observed in the transgenic line. These data support the hypothesis that mtICDH may be a regulatory switch involved in tricarboxylic acid cycle flux and the reductive modulation of AOX.
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Affiliation(s)
- Gordon R Gray
- Department of Plant Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5A8, Canada.
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Affourtit C, Moore AL. Purification of the plant alternative oxidase from Arum maculatum: measurement, stability and metal requirement. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2004; 1608:181-9. [PMID: 14871496 DOI: 10.1016/j.bbabio.2003.12.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2003] [Revised: 12/03/2003] [Accepted: 12/10/2003] [Indexed: 10/26/2022]
Abstract
We have purified plant alternative oxidase (AOX) protein from the spadices of thermogenic Arum maculatum (cuckoo pint) to virtual homogeneity. The obtained enzyme fraction exhibits a high specific activity, consuming on average 32 micromol oxygen min(-1) mg(-1), which is completely stable for at least 6 months when the sample is stored at -70 degrees C. This exceptionally stable AOX activity is inhibited approximately 90% (I(50) approximately 10 microM) by 8-hydroxyquinoline (8-OHQ) and also, although to a lesser extent, by other metal chelators such as o-phenanthroline, alpha,alpha'-dipyridyl and EDTA. When inhibited by 8-OHQ, AOX activity is fully restored upon addition of 1.2 mM ferric iron, but neither ferrous iron nor manganese has any effect, whilst zinc decreases activity even further. Furthermore, we have developed a spectrophotometric assay to measure AOX activity in an accurate manner, which will facilitate future steady state and transient kinetic studies. The reliability of this assay is evidenced by retained stability of AOX protein during the course of the reaction, reproducibility of the measured initial rates, an observed 2:1 duroquinol-oxygen stoichiometry and by the fact that, in absolute terms, the measured rates of duroquinone formation and duroquinol disappearance are identical.
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Affiliation(s)
- Charles Affourtit
- Department of Biochemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, United Kingdom.
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26
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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]
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Rasmusson AG, Soole KL, Elthon TE. Alternative NAD(P)H dehydrogenases of plant mitochondria. ANNUAL REVIEW OF PLANT BIOLOGY 2004; 55:23-39. [PMID: 15725055 DOI: 10.1146/annurev.arplant.55.031903.141720] [Citation(s) in RCA: 171] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Plant mitochondria have a highly branched electron transport chain that provides great flexibility for oxidation of cytosolic and matrix NAD(P)H. In addition to the universal electron transport chain found in many organisms, plants have alternative NAD(P)H dehydrogenases in the first part of the chain and a second oxidase, the alternative oxidase, in the latter part. The alternative activities are nonproton pumping and allow for NAD(P)H oxidation with varying levels of energy conservation. This provides a mechanism for plants to, for example, remove excess reducing power and balance the redox poise of the cell. This review presents our current understanding of the alternative NAD(P)H dehydrogenases present in plant mitochondria.
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Affiliation(s)
- Allan G Rasmusson
- Department of Cell and Organism Biology, Lund University, SE-223 62 Lund, Sweden.
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Nihei C, Fukai Y, Kawai K, Osanai A, Yabu Y, Suzuki T, Ohta N, Minagawa N, Nagai K, Kita K. Purification of active recombinant trypanosome alternative oxidase. FEBS Lett 2003; 538:35-40. [PMID: 12633849 DOI: 10.1016/s0014-5793(03)00120-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Trypanosome alternative oxidase (TAO) is the terminal oxidase of the respiratory chain in long slender bloodstream forms of African trypanosomes. TAO is a cytochrome-independent, cyanide-insensitive quinol oxidase. These characteristics are distinct from those of the bacterial quinol oxidases, proteins that belong to the heme-copper terminal oxidase superfamily. The inability to purify stable TAO has severely hampered biochemical studies of the alternative oxidase family. In the present study, we were able to purify recombinant TAO to homogeneity from Escherichia coli membranes using the detergent digitonin. Kinetic analysis of the purified TAO revealed that the specific inhibitor ascofuranone is a competitive inhibitor of ubiquinol oxidase activity.
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Affiliation(s)
- Coichi Nihei
- Department of Biomedical Chemistry, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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29
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Karpova OV, Kuzmin EV, Elthon TE, Newton KJ. Differential expression of alternative oxidase genes in maize mitochondrial mutants. THE PLANT CELL 2002; 14:3271-84. [PMID: 12468742 PMCID: PMC151217 DOI: 10.1105/tpc.005603] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2002] [Accepted: 09/20/2002] [Indexed: 05/18/2023]
Abstract
We have examined the expression of three alternative oxidase (aox) genes in two types of maize mitochondrial mutants. Nonchromosomal stripe (NCS) mutants carry mitochondrial DNA deletions that affect subunits of respiratory complexes and show constitutively defective growth. Cytoplasmic male-sterile (CMS) mutants have mitochondrial DNA rearrangements, but they are impaired for mitochondrial function only during anther development. In contrast to normal plants, which have very low levels of AOX, NCS mutants exhibit high expression of aox genes in all nonphotosynthetic tissues tested. The expression pattern is specific for each type of mitochondrial lesion: the NADH dehydrogenase-defective NCS2 mutant has high expression of aox2, whereas the cytochrome oxidase-defective NCS6 mutant predominantly expresses aox3. Similarly, aox2 and aox3 can be induced differentially in normal maize seedlings by specific inhibitors of these two respiratory complexes. Translation-defective NCS4 plants show induction of both aox2 and aox3. AOX2 and AOX3 proteins differ in their ability to be regulated by reversible dimerization. CMS mutants show relatively high levels of aox2 mRNAs in young tassels but none in ear shoots. Significant expression of aox1 is detected only in NCS and CMS tassels. The induction pattern of maize aox genes could serve as a selective marker for diverse mitochondrial defects.
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Affiliation(s)
- Olga V Karpova
- Division of Biological Sciences, Tucker Hall, University of Missouri, Columbia, Missouri 6521, USA
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30
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Berthold DA, Voevodskaya N, Stenmark P, Gräslund A, Nordlund P. EPR studies of the mitochondrial alternative oxidase. Evidence for a diiron carboxylate center. J Biol Chem 2002; 277:43608-14. [PMID: 12215444 DOI: 10.1074/jbc.m206724200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The alternative oxidase (AOX) is a ubiquinol oxidase found in the mitochondrial respiratory chain of plants as well as some fungi and protists. It has been predicted to contain a coupled diiron center on the basis of a conserved sequence motif consisting of the proposed iron ligands, four glutamate and two histidine residues. However, this prediction has not been experimentally verified. Here we report the high level expression of the Arabidopsis thaliana alternative oxidase AOX1a as a maltose-binding protein fusion in Escherichia coli. Reduction and reoxidation of a sample of isolated E. coli membranes containing the alternative oxidase generated an EPR signal characteristic of a mixed-valent Fe(II)/Fe(III) binuclear iron center. The high anisotropy of the signal, the low value of the g-average tensor, and a small exchange coupling (-J) suggest that the iron center is hydroxo-bridged. A reduced membrane preparation yielded a parallel mode EPR signal with a g-value of about 15. In AOX containing a mutation of a putative glutamate ligand of the diiron center (E222A or E273A) the EPR signals are absent. These data provide evidence for an antiferromagnetic-coupled binuclear iron center, and together with the conserved sequence motif, identify the alternative oxidase as belonging to the growing family of diiron carboxylate proteins. The alternative oxidase is the first integral membrane protein in this family, and adds a new catalytic activity (ubiquinol oxidation) to this group of enzymatically diverse proteins.
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Affiliation(s)
- Deborah A Berthold
- Department of Biochemistry and Biophysics, Stockholm University Svante Arrhenius väg 16, Sweden.
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31
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Abe F, Saito K, Miura K, Toriyama K. A single nucleotide polymorphism in the alternative oxidase gene among rice varieties differing in low temperature tolerance. FEBS Lett 2002; 527:181-5. [PMID: 12220657 DOI: 10.1016/s0014-5793(02)03218-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Alternative oxidase (AOX) is encoded in a multigene family, and multiple isoforms have been observed in various plant species. We found for the first time an allelic variation in the same AOX locus. On SDS-gel blots of callus protein of rice (Oryza sativa L.), varieties without the QTL for low temperature tolerance showed a 32-kDa AOX band, whereas those with the QTL showed a 34-kDa band. The variation was attributed to the substitution of Lys(71) for Asn(71) caused by a single nucleotide polymorphism between alleles of OsAOX1a, and was tightly linked to the presence of the QTL.
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Affiliation(s)
- Fumitaka Abe
- Laboratory of Plant Breeding and Genetics, Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, 981-8555, Sendai, Japan
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32
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Zottini M, Formentin E, Scattolin M, Carimi F, Lo Schiavo F, Terzi M. Nitric oxide affects plant mitochondrial functionality in vivo. FEBS Lett 2002; 515:75-8. [PMID: 11943198 DOI: 10.1016/s0014-5793(02)02438-9] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this report, we show that nitric oxide affects mitochondrial functionality in plant cells and reduces total cell respiration due to strong inhibition of the cytochrome pathway. The residual respiration depends on the alternative pathway and novel synthesis of alternative oxidase occurs. These modifications are associated with depolarisation of the mitochondrial membrane potential and release of cytochrome c from mitochondria, suggesting a conserved signalling pathway in plants and animals. This signal cascade is triggered at the mitochondrial level and induces about 20% of cell death. In order to achieve a higher level of cell death, the addition of H(2)O(2) is necessary.
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Affiliation(s)
- Michela Zottini
- Department of Biology, University of Padova, Via U. Bassi, 58/B, 35131, Padova, Italy.
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33
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Li C, Liang H, Du L, Wang R. Studies on the relationship between cyanide-resistant respiration and expression of alternative oxidase in mung bean using antibodies prepared by synthetic polypeptide. ACTA ACUST UNITED AC 2001; 44:66-72. [DOI: 10.1007/bf02882074] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2000] [Indexed: 11/28/2022]
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34
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Berthold DA, Andersson ME, Nordlund P. New insight into the structure and function of the alternative oxidase. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1460:241-54. [PMID: 11106766 DOI: 10.1016/s0005-2728(00)00149-3] [Citation(s) in RCA: 158] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The alternative oxidase is a ubiquinol oxidase found in plant mitochondria, as well as in the mitochondria of some fungi and protists. It catalyzes a cyanide-resistant reduction of oxygen to water without translocation of protons across the inner mitochondrial membrane, and thus functions as a non-energy-conserving member of the respiratory electron transfer chain. The active site of the alternative oxidase has been modelled as a diiron center within a four-helix bundle by Siedow et al. (FEBS Lett. 362 (1995) 10-14) and more recently by Andersson and Nordlund (FEBS Lett. 449 (1999) 17-22). The cloning of the Arabidopsis thaliana IMMUTANS (Im) gene, which encodes a plastid enzyme distantly related to the mitochondrial alternative oxidases (Wu et al. Plant Cell 11 (1999) 43-55; Carol et al. Plant Cell 11 (1999) 57-68), has now narrowed the range of possible ligands to the diiron center of the alternative oxidase. The Im protein sequence suggests a minor modification to the recent model of the active site of the alternative oxidase. This change moves an invariant tyrosine into a conserved hydrophobic pocket in the vicinity of the active site, in a position analogous to the long-lived tyrosine radical at the diiron center of ribonucleotide reductase, and similar to the tyrosines near the diiron center of bacterioferritin and rubrerythrin. The Im sequence and modified structural model yield a compelling picture of the alternative oxidase as a diiron carboxylate protein. The current status of the relationship of structure to function in the alternative oxidase is reviewed.
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Affiliation(s)
- D A Berthold
- Department of Biochemistry, Stockholm University, Svante Arrhenius vag 16, S-106 91, Stockholm, Sweden
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35
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Maxwell DP, Wang Y, McIntosh L. The alternative oxidase lowers mitochondrial reactive oxygen production in plant cells. Proc Natl Acad Sci U S A 1999; 96:8271-6. [PMID: 10393984 PMCID: PMC22224 DOI: 10.1073/pnas.96.14.8271] [Citation(s) in RCA: 693] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/1999] [Accepted: 05/17/1999] [Indexed: 11/18/2022] Open
Abstract
Besides the cytochrome c pathway, plant mitochondria have an alternative respiratory pathway that is comprised of a single homodimeric protein, alternative oxidase (AOX). Transgenic cultured tobacco cells with altered levels of AOX were used to test the hypothesis that the alternative pathway in plant mitochondria functions as a mechanism to decrease the formation of reactive oxygen species (ROS) produced during respiratory electron transport. Using the ROS-sensitive probe 2',7'-dichlorofluorescein diacetate, we found that antisense suppression of AOX resulted in cells with a significantly higher level of ROS compared with wild-type cells, whereas the overexpression of AOX resulted in cells with lower ROS abundance. Laser-scanning confocal microscopy showed that the difference in ROS abundance among wild-type and AOX transgenic cells was caused by changes in mitochondrial-specific ROS formation. Mitochondrial ROS production was exacerbated by the use of antimycin A, which inhibited normal cytochrome electron transport. In addition, cells overexpressing AOX were found to have consistently lower expression of genes encoding ROS-scavenging enzymes, including the superoxide dismutase genes SodA and SodB, as well as glutathione peroxidase. Also, the abundance of mRNAs encoding salicylic acid-binding catalase and a pathogenesis-related protein were significantly higher in cells deficient in AOX. These results are evidence that AOX plays a role in lowering mitochondrial ROS formation in plant cells.
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Affiliation(s)
- D P Maxwell
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
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36
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He J, Wei Z, Liang H. Effects of water stress on development, operation and gene expression of cyanide-resistant respiratory pathway in wheat. ACTA ACUST UNITED AC 1999; 42:300-6. [DOI: 10.1007/bf03183607] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/1998] [Indexed: 10/19/2022]
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37
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Hoefnagel MH, Wiskich JT. Activation of the plant alternative oxidase by high reduction levels of the Q-pool and pyruvate. Arch Biochem Biophys 1998; 355:262-70. [PMID: 9675036 DOI: 10.1006/abbi.1998.0737] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This report describes the activation of the alternative oxidase (AOX) of higher plant mitochondria by a high reduction level of the ubiquinone pool in the presence of pyruvate. In mitochondria from both thermogenic (Arum italicum spadices) and nonthermogenic (Glycine max cotyledons) tissues AOXis activated when the Q-pool becomes highly reduced in the presence of pyruvate. Pyruvate is essential for this activation. The enzyme is not activated when pyruvate is added after a transient high reduction level of the Q-pool, but is when pyruvate is added before the transient reduction. Pyruvate also protects the enzyme against inhibition during catalytic turnover. Although this activation is not accompanied by a reduction of the covalent disulfide bond, the same activation can be achieved with dithiothreitol (DTT). It is suggested that a part of the activation by DTT is not the result of reducing the covalent disulfide bond, and the relation between these types of activation is discussed. The importance of this activation for the in vivo regulation and its relation to previously reported activators is discussed. A mechanism is proposed in which it is suggested that AOX is inactivated by its product (oxidized ubiquinone) during catalysis and that this inhibition is prevented in the presence of pyruvate. The inhibition can be reversed by a reductive process, achieved by high levels of reduction of the Q-pool or by DTT, but not by pyruvate. This restoration of activity is not related to the redox process involved in reducing the covalent disulfide bond.
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Affiliation(s)
- M H Hoefnagel
- Department of Botany, University of Adelaide, Adelaide, South Australia, 5005, Australia.
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38
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Joseph-Horne T, Wood PM, Wood CK, Moore AL, Headrick J, Hollomon D. Characterization of a split respiratory pathway in the wheat "take-all" fungus, Gaeumannomyces graminis var. tritici. J Biol Chem 1998; 273:11127-33. [PMID: 9556599 DOI: 10.1074/jbc.273.18.11127] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
This article describes the first detailed analysis of mitochondrial electron transfer and oxidative phosphorylation in the pathogenic filamentous fungus, Gaeumannomyces graminis var. tritici. While oxygen consumption was cyanide insensitive, inhibition occurred following treatment with complex III inhibitors and the alternative oxidase inhibitor, salicylhydroxamic acid (SHAM). Similarly, maintenance of a Deltapsi across the mitochondrial inner membrane was unaffected by cyanide but sensitive to antimycin A and SHAM when succinate was added as the respiratory substrate. As a result, ATP synthesis through complex V was demonstrated to be sensitive to these two inhibitors but not to cyanide. Analysis of the cytochrome content of mitochondria indicated the presence of those cytochromes normally associated with electron transport in eukaryotic mitochondria together with a third, b-type heme, exhibiting a dithionite-reduced absorbance maxima at 560 nm and not associated with complex III. Antibodies raised to plant alternative oxidase detected the presence of both the monomeric and dimeric forms of this oxidase. Overall this study demonstrates that a novel respiratory chain utilizing the terminal oxidases, cytochrome c oxidase and alternative oxidase, are present and constitutively active in electron transfer in G. graminis tritici. These results are discussed in relation to current understanding of fungal electron transfer and to the possible contribution of alternative redox centers in ATP synthesis.
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Affiliation(s)
- T Joseph-Horne
- IACR-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol, BS41 9AF, United Kingdom.
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Rockabrand D, Livers K, Austin T, Kaiser R, Jensen D, Burgess R, Blum P. Roles of DnaK and RpoS in starvation-induced thermotolerance of Escherichia coli. J Bacteriol 1998; 180:846-54. [PMID: 9473038 PMCID: PMC106963 DOI: 10.1128/jb.180.4.846-854.1998] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
DnaK is essential for starvation-induced resistance to heat, oxidation, and reductive division in Escherichia coli. Studies reported here indicate that DnaK is also required for starvation-induced osmotolerance, catalase activity, and the production of the RpoS-controlled Dps (PexB) protein. Because these dnaK mutant phenotypes closely resemble those of rpoS (sigma38) mutants, the relationship between DnaK and RpoS was evaluated directly during growth and starvation at 30 degrees C in strains with genetically altered DnaK content. A starvation-specific effect of DnaK on RpoS abundance was observed. During carbon starvation, DnaK deficiency reduced RpoS levels threefold, while DnaK excess increased RpoS levels nearly twofold. Complementation of the dnaK mutation restored starvation-induced RpoS levels to normal. RpoS deficiency had no effect on the cellular concentration of DnaK, revealing an epistatic relationship between DnaK and RpoS. Protein half-life studies conducted at the onset of starvation indicate that DnaK deficiency significantly destabilized RpoS. RpoH (sigma32) suppressors of the dnaK mutant with restored levels of RpoS and dnaK rpoS double mutants were used to show that DnaK plays both an independent and an RpoS-dependent role in starvation-induced thermotolerance. The results suggest that DnaK coordinates sigma factor levels in glucose-starved E. coli.
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Affiliation(s)
- D Rockabrand
- School of Biological Sciences, University of Nebraska, Lincoln 68588-0666, USA
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40
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Ito Y, Saisho D, Nakazono M, Tsutsumi N, Hirai A. Transcript levels of tandem-arranged alternative oxidase genes in rice are increased by low temperature. Gene X 1997; 203:121-9. [PMID: 9426242 DOI: 10.1016/s0378-1119(97)00502-7] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We identified two genes for alternative oxidase (AOX) from rice. One AOX gene (designated AOX1a) is located approx. 1.9 kb downstream of another AOX gene (designated AOX1b). Comparison of the genomic and cDNA sequences of the two AOX genes showed that the AOX1a gene is interrupted by three introns, as are AOX genes of other plants. On the other hand, two introns are inserted in the AOX1b gene. The predicted AOX1a and AOX1b precursor proteins consist of 332 and 335 amino acid residues, respectively. A genomic Southern hybridization analysis indicated that rice has several AOX genes other than the two tandem-arranged AOX genes. Steady-state mRNA levels of both of the genes for AOX1a and AOX1b were increased under low temperature (4 degrees C). However, no difference in the pattern of induction of transcription between the genes for AOX1a and AOX1b was observed.
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MESH Headings
- Blotting, Northern
- Blotting, Southern
- Chromosome Mapping
- Cloning, Molecular
- Cold Temperature
- DNA, Complementary
- Gene Expression Regulation, Enzymologic
- Mitochondrial Proteins
- Oryza/enzymology
- Oryza/genetics
- Oxidoreductases/chemistry
- Oxidoreductases/genetics
- Phylogeny
- Plant Proteins
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Temperature
- Transcription, Genetic
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Affiliation(s)
- Y Ito
- Laboratory of Radiation Genetics, Graduate School of Agricultural and Life Science, The University of Tokyo, Japan
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41
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Saisho D, Nambara E, Naito S, Tsutsumi N, Hirai A, Nakazono M. Characterization of the gene family for alternative oxidase from Arabidopsis thaliana. PLANT MOLECULAR BIOLOGY 1997; 35:585-96. [PMID: 9349280 DOI: 10.1023/a:1005818507743] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We investigated the copy number of the gene for alternative oxidase (AOX) of Arabidopsis thaliana by amplification by PCR and Southern hybridization. These studies indicated that there are at least four copies of the AOX gene in Arabidopsis. We isolated genomic clones containing individual copies (designated as AOX1a, AOX1b, AOX1c and AOX2) of the AOX genes. Interestingly, two of the AOX genes (AOX1a and AOX1b) were located in tandem in a ca. 5 kb region on one of the chromosomes of Arabidopsis. Comparison between genomic and cDNA sequences of the four AOX genes showed that all AOX genes are divided by three introns and the positions of the introns in AOX1a, AOX1b, AOX1c and AOX2 are the same. We examined whether expression of Arabidopsis AOX genes, like the tobacco AOX1a gene, is enhanced by treatment with antimycin A, an inhibitor of complex III in the mitochondrial respiratory chain. We found that, in young plants, the amount of Arabidopsis AOX1a mRNA was dramatically increased by addition of antimycin A, while the transcription of the other three genes (AOX1b, AOX1c and AOX2) did not respond to antimycin A. Amplification by RT-PCR showed that AOX1a and AOX1c were expressed in all organs examined (flowers and buds, stems, rosette, and roots of 8-week old plants). In contrast, transcripts of AOX1b were detected only in the flowers and buds, and transcripts of AOX2 were detected mainly in stems, rosette and roots. These results suggested that transcriptions of the four genes for alternative oxidase of Arabidopsis are differentially regulated.
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Affiliation(s)
- D Saisho
- Laboratory of Radiation Genetics, Graduate School of Agricultural and Life Science, University of Tokyo, Japan
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42
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Abstract
Plants, some fungi, and protists contain a cyanide-resistant, alternative mitochondrial respiratory pathway. This pathway branches at the ubiquinone pool and consists of an alternative oxidase encoded by the nuclear gene Aox1. Alternative pathway respiration is only linked to proton translocation at Complex 1 (NADH dehydrogenase). Alternative oxidase expression is influenced by stress stimuli-cold, oxidative stress, pathogen attack-and by factors constricting electron flow through the cytochrome pathway of respiration. Control is exerted at the levels of gene expression and in response to the availability of carbon and reducing potential. Posttranslational control involves reversible covalent modification of the alternative oxidase and activation by specific carbon metabolites. This dynamic system of coarse and fine control may function to balance upstream respiratory carbon metabolism and downstream electron transport when these coupled processes become imbalanced as a result of changes in the supply of, or demand for, carbon, reducing power, and ATP.
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Affiliation(s)
- Greg C. Vanlerberghe
- Department of Botany and Division of Life Science, University of Toronto at Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada, Department of Energy Plant Research Laboratory and Biochemistry Department, Michigan State University, East Lansing, Michigan 48824
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43
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Finnegan PM, Whelan J, Millar AH, Zhang Q, Smith MK, Wiskich JT, Day DA. Differential expression of the multigene family encoding the soybean mitochondrial alternative oxidase. PLANT PHYSIOLOGY 1997; 114:455-66. [PMID: 9193084 PMCID: PMC158325 DOI: 10.1104/pp.114.2.455] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The alternative oxidase (AOX) of the soybean (Glycine max L.) inner mitochondrial membrane is encoded by a multigene family (Aox) with three known members. Here, the Aox2 and Aox3 primary translation products, deduced for cDNA analysis, were found to be 38.1 and 36.4 Kd, respectively. Direct N-terminal sequencing of partially purified AOX from cotyledons demonstrates that the mature proteins are 31.8 and 31.6 KD, respectively, implying that processing occurs upon import of these proteins into the mitochondrion. Sequence comparisons show that the processing of plant AOX proteins occurs at a characteristic site and that the AOX2 and AOX3 proteins are more similar to one another than to other AOX proteins, including soybean AOX1. Transcript analysis using a polymerase chain reaction-based assay in conjunction with immunoblot experiments indicates that soybean Aox genes are differentially expressed in a tissue-dependent manner. Moreover, the relative abundance of both Aox2 transcripts and protein in cotyledons increase upon greening of dark-grown seedlings. These results comprehensively explain the multiple AOX-banding patterns observed on immunoblots of mitochondrial proteins isolated from various soybean tissues by matching protein bands with gene products.
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Affiliation(s)
- P M Finnegan
- Division of Biochemistry and Molecular Biology, Faculty of Science, Australian National University, Canberra, ACT.
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Gutierres S, Sabar M, Lelandais C, Chetrit P, Diolez P, Degand H, Boutry M, Vedel F, de Kouchkovsky Y, De Paepe R. Lack of mitochondrial and nuclear-encoded subunits of complex I and alteration of the respiratory chain in Nicotiana sylvestris mitochondrial deletion mutants. Proc Natl Acad Sci U S A 1997; 94:3436-41. [PMID: 9096412 PMCID: PMC20388 DOI: 10.1073/pnas.94.7.3436] [Citation(s) in RCA: 146] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/1996] [Accepted: 01/06/1997] [Indexed: 02/04/2023] Open
Abstract
We previously have shown that Nicotiana sylvestris cytoplasmic male sterile (CMS) mutants I and II present large mtDNA deletions and that the NAD7 subunit of complex I (the main dehydrogenase of the mitochondrial respiratory chain) is absent in CMS I. Here, we show that, despite a large difference in size in the mtDNA deletion, CMS I and II display similar alterations. Both have an impaired development from germination to flowering, with partial male sterility that becomes complete under low light. Besides NAD7, two other complex I subunits are missing (NAD9 and the nucleus-encoded, 38-kDa subunit), identified on two-dimensional patterns of mitochondrial proteins. Mitochondria isolated from CMS leaves showed altered respiration. Although their succinate oxidation through complex II was close to that of the wild type, oxidation of glycine, a priority substrate of plant mitochondria, was significantly reduced. The remaining activity was much less sensitive to rotenone, indicating the breakdown of Complex I activity. Oxidation of exogenous NADH (coupled to proton gradient generation and partly sensitive to rotenone) was strongly increased. These results suggest respiratory compensation mechanisms involving additional NADH dehydrogenases to complex I. Finally, the capacity of the cyanide-resistant alternative oxidase pathway was enhanced in CMS, and higher amounts of enzyme were evidenced by immunodetection.
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Affiliation(s)
- S Gutierres
- Institut de Biotechnologie des Plantes, Centre National de la Recherche Scientifique (Unité de Recherche Associée 1128), Université Paris-Sud, Orsay, France
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Ribas-Carbo M, Lennon AM, Robinson SA, Giles L, Berry JA, Siedow JN. The Regulation of Electron Partitioning between the Cytochrome and Alternative Pathways in Soybean Cotyledon and Root Mitochondria. PLANT PHYSIOLOGY 1997; 113:903-911. [PMID: 12223652 PMCID: PMC158210 DOI: 10.1104/pp.113.3.903] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The regulation of electron partitioning between the cytochrome (Cyt) and alternative pathways in soybean (Glycine max L. cv Ransom) mitochondria in the absence of added inhibitors has been studied using the oxygen isotope fractionation technique. This regulation can depend on several factors, including the amount of alternative oxidase protein, the redox status of the alternative oxidase regulatory sulfhydryl-disulfide system, the degree of activation by [alpha]-keto acids, and the concentration and redox state of the ubiquinone pool. We studied electron partitioning onto the alternative pathway in mitochondria isolated from etiolated and light-grown cotyledons and roots to ascertain how these factors interact in different tissues. In light-grown cotyledon mitochondria there is some partitioning to the alternative pathway in state 4, which is increased dramatically by either pyruvate or dithiothreitol. In etiolated cotyledon mitochondria, the alternative pathway shows little ability to compete for electrons with the Cyt pathway under any circumstances. In root mitochondria, control of alternative pathway activity is exercised by both the ubiquinone pool and the regulatory sulfhydryl-disulfide system. In addition, oxygen isotope fractionation by the Cyt and alternative pathways in mitochondria were identical to the fractionation for the respective pathways seen in intact tissue, suggesting that residual respiration is not present in the absence of inhibitors.
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Affiliation(s)
- M. Ribas-Carbo
- Department of Botany, Developmental, Cell, and Molecular Biology Group, Box 91000, Duke University, Durham, North Carolina 27708-1000 (M.R.-C., A.M.L., J.N.S.)
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Skubatz H, Kunkel DD, Howald WN, Trenkle R, Mookherjee B. The Sauromatum guttatum appendix as an osmophore: excretory pathways, composition of volatiles and attractiveness to insects. THE NEW PHYTOLOGIST 1996; 134:631-640. [PMID: 33863208 DOI: 10.1111/j.1469-8137.1996.tb04928.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
This report combines chemical, electron microscopic and ecological studies on the volatiles liberated by the Sauromatum guttatum appendix on D-Day, the day of inflorescence-opening and heat-production. More than 100 compounds from at least nine different chemical classes (monoterpenes, sesquiterpenes, fatty acids, ketones, alcohols, aldehydes, indole, and phenolic and sulphur compounds) are liberated during the thermogenic activity. The volatiles were identified using gas chromatography-mass spectrometry. Electron microscopy provides additional evidence that the endoplasmic reticulum (ER) interacts with the plasma membrane, creating novel routes of excretion of the volatiles to the exterior of the cell. It seems that the fusion event creates channels from the interior to the exterior of the cell. Furthermore, a multitubular body, conceivably originating in the ER, seems to fuse with the plasma membrane and to appear only on D-day. This multitubular body is closely associated with lipid bodies during heat-production and might be involved in the oxidation of lipids to volatile products. The foul odour produced by the appendix attracts at least 30 species of insects.
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Affiliation(s)
- Hanna Skubatz
- Department of Botany, University of Washington, Seattle, WA 98195, USA
| | - Dennis D Kunkel
- BEKESY Lab of Neurobiology, University of Hawaii at Manoa, Honolulu, Hawaii,96822
| | - William N Howald
- Department of Medicinal Chemisty, University of Washington, Seattle, WA 98195, USA
| | - Robert Trenkle
- Department of Botany, University of Washington, Seattle, WA 98195, USA
| | - Braja Mookherjee
- International Flavors and Fragrances, 1515 Highway 36, Union Beach, NJ 07735, USA
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Umbach AL, Siedow JN. The reaction of the soybean cotyledon mitochondrial cyanide-resistant oxidase with sulfhydryl reagents suggests that alpha-keto acid activation involves the formation of a thiohemiacetal. J Biol Chem 1996; 271:25019-26. [PMID: 8798784 DOI: 10.1074/jbc.271.40.25019] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The cyanide-resistant alternative oxidase of plant mitochondria is known to be activated by alpha-keto acids, such as pyruvate, and by the reduction of a disulfide bond that bridges the two subunits of the enzyme homodimer. When the regulatory cysteines are oxidized, the inactivated enzyme is much less responsive to pyruvate than when these groups are reduced. When soybean cotyledon mitochondria were isolated in the presence of iodoacetate or N-ethylmaleimide, the intermolecular disulfide bond did not form and the alternative oxidase was present only as a noncovalently associated dimer. N-Ethylmaleimide inhibited alternative oxidase activity, but iodoacetate was found to stimulate activity much like pyruvate, including enhancing the enzyme's apparent affinity for reduced ubiquinone. The presence of pyruvate or iodoacetate blocked inhibition of the enzyme by N-ethylmaleimide, indicating that all three compounds acted at the same sulfhydryl group on the alternative oxidase protein. The site of pyruvate and iodoacetate action was shown to be a different sulfhydryl than that involved in the redox-active regulatory disulfide bond, because iodoacetate bound to the alternative oxidase at the activating site even when the redox-active regulatory sulfhydryls were oxidized. Given the nature of the covalent adduct formed by the reaction of iodoacetate with sulfhydryls, the activation of the alternative oxidase by alpha-keto acids appears to involve the formation of a thiohemiacetal.
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Affiliation(s)
- A L Umbach
- Developmental, Cell, and Molecular Biology Group/Botany Department, Duke University, Durham, North Carolina 27708-1000, USA
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48
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A mechanism for low temperature induced sugar accumulation in stored potato tubers: The potential role of the alternative pathway and invertase. ACTA ACUST UNITED AC 1996. [DOI: 10.1007/bf02849671] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Li Q, Ritzel RG, McLean LL, McIntosh L, Ko T, Bertrand H, Nargang FE. Cloning and analysis of the alternative oxidase gene of Neurospora crassa. Genetics 1996; 142:129-40. [PMID: 8770590 PMCID: PMC1206941 DOI: 10.1093/genetics/142.1.129] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Mitochondria of Neurospora crassa contain a cyanide-resistant alternative respiratory pathway in addition to the cytochrome pathway. The alternative oxidase is present only when electron flow through the cytochrome chain is restricted. Both genomic and cDNA copies for the alternative oxidase gene have been isolated and analyzed. The sequence of the predicted protein is homologous to that of other species. The mRNA for the alternative oxidase is scarce in wild-type cultures grown under normal conditions, but it is abundant in cultures grown in the presence of chloramphenicol, an inhibitor of mitochondrial protein synthesis, or in mutants deficient in mitochondrial cytochromes. Thus, induction of alternative oxidase appears to be at the transcriptional level. Restriction fragment length polymorphism mapping of the isolated gene demonstrated that it is located in a position corresponding to the aod-1 locus. Sequence analysis of mutant aod-1 alleles reveals mutations affecting the coding sequence of the alternative oxidase. The level of aod-1 mRNA in an aod-2 mutant strain that had been grown in the presence of chloramphenicol was reduced several fold relative to wild-type, supporting the hypothesis that the product of aod-2 is required for optimal expression of aod-1.
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Affiliation(s)
- Q Li
- Department of Biological Sciences, University of Alberta, Edmonton, Canada
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Hiser C, Kapranov P, McIntosh L. Genetic modification of respiratory capacity in potato. PLANT PHYSIOLOGY 1996; 110:277-86. [PMID: 8587988 PMCID: PMC157719 DOI: 10.1104/pp.110.1.277] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Mitochondrial respiration was altered in transgenic potato (Solanum tuberosum) lines by overexpression of the alternative oxidase Aox1 gene. Overexpressing lines showed higher levels of Aox1 mRNA, increased levels of alternative oxidase protein(s), and an unusual higher molecular weight polypeptide, which may be a normal processing/modification intermediate. Evidence suggests that the alternative oxidase protein is further processed/modified beyond removal of the transit peptide. Addition of pyruvate to mitochondria oxidizing succinate or NADH increased the alternative pathway capacity but did not eliminate the difference in the capacity between these two substrates. Induction of alternative pathway capacity by aging of tubers appeared to be more dependent on increased levels of alternative oxidase protein than changes in its oxidation state. In leaf and tuber mitochondria, overexpressing lines possessed higher alternative pathway capacity than the control line, which suggests that changing the alternative oxidase protein level by genetic engineering can effectively change alternative pathway capacity.
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Affiliation(s)
- C Hiser
- Michigan State University-Department of Energy Plant Research Laboratory, East Lansing 28824, USA
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