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0000-0002-5882-4323
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Crop and Pasture Production | Cell Metabolism | Plant Biochemistry And Physiology | Gene Expression | Plant Nutrition | Plant Physiology | Biochemistry and Cell Biology | Genetics | Plant Biology | Membrane Biology | Genome Structure | Nanochemistry and Supramolecular Chemistry | Medical Biotechnology | Plant Improvement (Selection, Breeding And Genetic Engineering) | Plant Protection (Pests, Diseases And Weeds) | Biochemistry and Cell Biology not elsewhere classified | Structural Biology (incl. Macromolecular Modelling) | Biological Sciences Not Elsewhere Classified | Medical Virology | Medical Bacteriology | Bioinorganic Chemistry | Characterisation of Biological Macromolecules | Molecular Medicine | Inorganic Chemistry | Biologically Active Molecules | Biotechnology Not Elsewhere Classified | Post Harvest Technologies | Cell Physiology | Plant Cell and Molecular Biology | Crop and Pasture Nutrition | Sustainable Agricultural Development | Plant Pathology | Crop and Pasture Biochemistry and Physiology | Animal Production Not Elsewhere Classified | Genetic Technologies: Transformation, Site-Directed Mutagenesis, Etc. | Cell Development, Proliferation and Death |
ANZSRC Socio-Economic Objective (SEO)
Field crops | Grain legumes | Horticultural crops | Wheat | Land and water management | Primary products from plants | Biological sciences | Chemical sciences | Physical sciences | Field crops not elsewhere classified | Sheep—meat | Grain Legumes | Wheat | Clinical health not specific to particular organs, diseases and conditions | Diagnostics | Reproductive system and disorders | Treatments (e.g. chemicals, antibiotics) | Beef cattle | Organs, diseases and abnormal conditions not elsewhere classified | Soybeans | Infectious diseases | Nervous system and disorders | Cardiovascular system and diseases | Cancer and related disorders | Horticultural crops not elsewhere classified | Other
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Publications
AtNDB2 is the main external NADH dehydrogenase in mitochondria and is important for tolerance to environmental stress
Publisher: Oxford University Press (OUP)
Date: 13-08-2019
DOI: 10.1104/PP.19.00877
Cell-to-cell transport via the lumen of the endoplasmic reticulum
Publisher: Wiley
Date: 04-04-2011
Nutrient transport across symbiotic membranes from legume nodules
Publisher: CSIRO Publishing
Date: 2001
DOI: 10.1071/PP01028
GmZIP1 encodes a symbiosis-specific zinc transporter in soybean
Publisher: Elsevier BV
Date: 02-2002
Characterization of an ammonium transport protein from the peribacteroid membrane of soybean nodules
Publisher: American Association for the Advancement of Science (AAAS)
Date: 21-08-1998
DOI: 10.1126/SCIENCE.281.5380.1202
Abstract: Nitrogen-fixing bacteroids in legume root nodules are surrounded by the plant-derived peribacteroid membrane, which controls nutrient transfer between the symbionts. A nodule complementary DNA ( GmSAT1 ) encoding an ammonium transporter has been isolated from soybean. GmSAT1 is preferentially transcribed in nodules and immunoblotting indicates that GmSAT1 is located on the peribacteroid membrane. [ 14 C]methylammonium uptake and patch-cl analysis of yeast expressing GmSAT1 demonstrated that it shares properties with a soybean peribacteroid membrane NH 4 + channel described elsewhere. GmSAT1 is likely to be involved in the transfer of fixed nitrogen from the bacteroid to the host.
SUGAR AND AMINO-ACID-TRANSPORT ACROSS SYMBIOTIC MEMBRANES FROM SOYBEAN NODULES
Publisher: Scientific Societies
Date: 1990
DOI: 10.1094/MPMI-3-334
GmVTL1 is an iron transporter on the symbiosome membrane of soybean with an important role in nitrogen fixation
Publisher: Cold Spring Harbor Laboratory
Date: 05-03-2020
DOI: 10.1101/2020.03.03.975805
Abstract: Legumes establish symbiotic relationships with soil bacteria (rhizobia), housed in nodules on plant roots. The plant supplies carbon substrates and other nutrients to the bacteria in exchange for fixed nitrogen. The exchange occurs across a plant-derived symbiosome membrane (SM), which encloses rhizobia to form a symbiosome. Iron supplied by the plant is crucial for the rhizobial enzyme nitrogenase that catalyses N 2 fixation, but the SM iron transporter has not been identified. We use complementation of yeast and plant mutants, real-time PCR, hairy root transformation, microscopy and proteomics to demonstrate the role of soybean GmVTL1 and 2. Both are members of the vacuolar iron transporter family and homologous to Lotus japonicus SEN1 (LjSEN1), previously shown to be essential for N 2 fixation. GmVTL1 expression is enhanced in nodule infected cells and both proteins are localised to the SM. GmVTL1 and 2 transport iron in yeast and GmVTL1 restores N 2 fixation when expressed in the Ljsen1 mutant. Three GmVTL1 amino acid substitutions that reduce iron transport in yeast also block N 2 fixation in Ljsen1 plants. We conclude GmVTL1 is responsible for transport of iron across the SM to bacteroids and plays a crucial role in the N 2 -fixing symbiosis.
The cytotoxic lipid peroxidation product 4-hydroxy-2-nonenal covalently modifies a selective range of proteins linked to respiratory function in plant mitochondria
Publisher: Elsevier BV
Date: 12-2007
Genomic structure and expression of alternative oxidase genes in legumes
Publisher: Wiley
Date: 06-2019
DOI: 10.1111/PCE.13161
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.
MICROAEROBIC RESPIRATION AND OXIDATIVE-PHOSPHORYLATION BY SOYBEAN NODULE MITOCHONDRIA - IMPLICATIONS FOR NITROGEN-FIXATION
Publisher: Wiley
Date: 07-1995
Metabolite transport across symbiotic membranes of legume nodules
Publisher: Annual Reviews
Date: 06-1997
DOI: 10.1146/ANNUREV.ARPLANT.48.1.493
Abstract: ▪ Abstract Infection of legume roots or stems with soil bacteria of the Rhizobiaceae results in the formation of nodules that become symbiotic nitrogen-fixing organs. Within the infected cells of these nodules, bacteria are enveloped in a membrane of plant origin, called the peribacteroid membrane (PBM), and ide and differentiate to form nitrogen-fixing bacteroids. The organelle-like structure comprised of PBM and bacteroids is termed the symbiosome, and is the basic nitrogen-fixing unit of the nodule. The major exchange of nutrients between the symbiotic partners is reduced carbon from the plant, to fuel nitrogenase activity in the bacteroid, and fixed nitrogen from the bacteroid, which is assimilated in the plant cytoplasm. However, many other metabolites are also exchanged. The metabolic interaction between the plant and the bacteroids is regulated by a series of transporters and channels on the PBM and the bacteroid membrane, and these form the focus of this review.
Soybean Yellow Stripe-like 7 is a symbiosome membrane peptide transporter important for nitrogen fixation
Publisher: Oxford University Press (OUP)
Date: 05-02-2021
Abstract: Legumes form a symbiosis with rhizobia that convert atmospheric nitrogen (N2) to ammonia and provide it to the plant in return for a carbon and nutrient supply. Nodules, developed as part of the symbiosis, harbor rhizobia that are enclosed in a plant-derived symbiosome membrane (SM) to form an organelle-like structure called the symbiosome. In mature nodules exchanges between the symbionts occur across the SM. Here we characterize Yellow Stripe-like 7 (GmYSL7), a Yellow stripe-like family member localized on the SM in soybean (Glycine max) nodules. It is expressed specifically in infected cells with expression peaking soon after nitrogenase becomes active. Unlike most YSL family members, GmYSL7 does not transport metals complexed with phytosiderophores. Rather, it transports oligopeptides of between four and 12 amino acids. Silencing GmYSL7 reduces nitrogenase activity and blocks infected cell development so that symbiosomes contain only a single bacteroid. This indicates the substrate of YSL7 is required for proper nodule development, either by promoting symbiosome development directly or by preventing inhibition of development by the plant. RNAseq of nodules where GmYSL7 was silenced suggests that the plant initiates a defense response against rhizobia with genes encoding proteins involved in amino acid export downregulated and some transcripts associated with metal homeostasis altered. These changes may result from the decrease in nitrogen fixation upon GmYSL7 silencing and suggest that the peptide(s) transported by GmYSL7 monitor the functional state of the bacteroids and regulate nodule metabolism and transport processes accordingly. Further work to identify the physiological substrate for GmYSL7 will allow clarification of this role.
Proteomic Analysis of the Soybean Symbiosome Identifies New Symbiotic Proteins
Publisher: Elsevier BV
Date: 05-2015
Online Oxygen Kinetic Isotope Effects Using Membrane Inlet Mass Spectrometry Can Differentiate between Oxidases for Mechanistic Studies and Calculation of Their Contributions to Oxygen Consumption in
Publisher: American Chemical Society (ACS)
Date: 05-2014
DOI: 10.1021/AC501086N
Abstract: The reduction chemistry of molecular oxygen underpins the energy metabolism of multicellular organisms, liberating free energy needed to catalyze a plethora of enzymatic reactions. Measuring the isotope signatures of (16)O and (18)O during O2 reduction can provide insights into both kinetic and equilibrium isotope effects. However, current methods to measure O2 isotope signatures are time-consuming and disruptive. This paper describes the application of membrane inlet mass spectrometry to determine the oxygen isotope discrimination of a range of O2-consuming reactions, providing a rapid and convenient method for determining these values. A survey of oxygenase and oxidase reactions provides new insights into previously uncharacterized amino acid oxidase enzymes. Liquid and gas phase measurements show the ease of assays using this approach for purified enzymes, biological extracts and intact tissues.
Energy costs of salt tolerance in crop plants
Publisher: Wiley
Date: 11-07-2019
DOI: 10.1111/NPH.15864
Abstract: Agriculture is expanding into regions that are affected by salinity. This review considers the energetic costs of salinity tolerance in crop plants and provides a framework for a quantitative assessment of costs. Different sources of energy, and modifications of root system architecture that would maximize water vs ion uptake are addressed. Energy requirements for transport of salt (NaCl) to leaf vacuoles for osmotic adjustment could be small if there are no substantial leaks back across plasma membrane and tonoplast in root and leaf. The coupling ratio of the H
OCT Retinal and Choroidal Layer Instance Segmentation Using Mask R-CNN
Publisher: MDPI AG
Date: 04-03-2022
DOI: 10.3390/S22052016
Abstract: Optical coherence tomography (OCT) of the posterior segment of the eye provides high-resolution cross-sectional images that allow visualization of in idual layers of the posterior eye tissue (the retina and choroid), facilitating the diagnosis and monitoring of ocular diseases and abnormalities. The manual analysis of retinal OCT images is a time-consuming task therefore, the development of automatic image analysis methods is important for both research and clinical applications. In recent years, deep learning methods have emerged as an alternative method to perform this segmentation task. A large number of the proposed segmentation methods in the literature focus on the use of encoder–decoder architectures, such as U-Net, while other architectural modalities have not received as much attention. In this study, the application of an instance segmentation method based on region proposal architecture, called the Mask R-CNN, is explored in depth in the context of retinal OCT image segmentation. The importance of adequate hyper-parameter selection is examined, and the performance is compared with commonly used techniques. The Mask R-CNN provides a suitable method for the segmentation of OCT images with low segmentation boundary errors and high Dice coefficients, with segmentation performance comparable with the commonly used U-Net method. The Mask R-CNN has the advantage of a simpler extraction of the boundary positions, especially avoiding the need for a time-consuming graph search method to extract boundaries, which reduces the inference time by 2.5 times compared to U-Net, while segmenting seven retinal layers.
Response of mitochondria to light intensity in the leaves of sun and shade species
Publisher: Wiley
Date: 09-03-2005
The crucial roles of mitochondria in supporting C4 photosynthesis
Publisher: Wiley
Date: 13-11-2021
DOI: 10.1111/NPH.17818
Abstract: C 4 photosynthesis involves a series of biochemical and anatomical traits that significantly improve plant productivity under conditions that reduce the efficiency of C 3 photosynthesis. We explore how evolution of the three classical biochemical types of C 4 photosynthesis (NADP‐ME, NAD‐ME and PCK types) has affected the functions and properties of mitochondria. Mitochondria in C 4 NAD‐ME and PCK types play a direct role in decarboxylation of metabolites for C 4 photosynthesis. Mitochondria in C 4 PCK type also provide ATP for C 4 metabolism, although this role for ATP provision is not seen in NAD‐ME type. Such involvement has increased mitochondrial abundance/size and associated enzymatic capacity, led to changes in mitochondrial location and ultrastructure, and altered the role of mitochondria in cellular carbon metabolism in the NAD‐ME and PCK types. By contrast, these changes in mitochondrial properties are absent in the C 4 NADP‐ME type and C 3 leaves, where mitochondria play no direct role in photosynthesis. From an eco‐physiological perspective, rates of leaf respiration in darkness vary considerably among C 4 species but does not differ systematically among the three C 4 types. This review outlines further mitochondrial research in key areas central to the engineering of the C 4 pathway into C 3 plants and to the understanding of variation in rates of C 4 dark respiration.
Cytochrome and Alternative Respiratory Pathways Compete for Electrons in the Presence of Pyruvate in Soybean Mitochondria
Publisher: Elsevier BV
Date: 04-1995
Abstract: The partitioning of electrons between the alternative oxidase and the cytochrome pathway of soybean mitochondria has been reassessed in the presence of the alternative oxidase activator pyruvate. In the presence of pyruvate and with succinate as substrate, the alternative oxidase became active at a much lower level of ubiquinone reduction than in the absence of pyruvate. Under state 4 (no ADP present) conditions, activation of the alternative oxidase with pyruvate resulted in an oxidation of b cytochromes, demonstrating switching of electrons away from the cytochrome chain. In the presence of ferricyanide and the cytochrome oxidase inhibitor KCN, cytochrome chain activity could be followed spectrophotometrically and that of the alternative pathway with an oxygen electrode. Under these conditions, the addition of pyruvate erted electron flow from the cytochrome chain to the alternative pathway subsequent inhibition of the alternative oxidase increased electron flow via the cytochrome chain. This indicates that electrons can be switched from one pathway to the other when the cytochrome chain is not saturated and this was confirmed by n-propylgallate titrations (p plots) of mitochondria oxidizing succinate. Decreases in ADP/O ratios and phosphorylation rate upon addition of pyruvate indicated that the alternative pathway could also contribute to respiration under state 3 conditions. The results indicate that when the alternative oxidase is activated by pyruvate, it can compete for electrons with the cytochrome chain and does not act as an overflow pathway. The significance of these observations for in vivo respiration is discussed.
Organization and Regulation of Mitochondrial Respiration in Plants
Publisher: Annual Reviews
Date: 02-06-2011
DOI: 10.1146/ANNUREV-ARPLANT-042110-103857
Abstract: Mitochondrial respiration in plants provides energy for biosynthesis, and its balance with photosynthesis determines the rate of plant biomass accumulation. We describe recent advances in our understanding of the mitochondrial respiratory machinery of cells, including the presence of a classical oxidative phosphorylation system linked to the cytosol by transporters, discussed alongside nonphosphorylating (and, therefore, non-energy conserving) bypasses that alter the efficiency of ATP synthesis and play a role in oxidative stress responses in plants. We consider respiratory regulation in the context of the contrasting roles mitochondria play in different tissues, from photosynthetic leaves to nutrient-acquiring roots. We focus on the molecular nature of this regulation at transcriptional and post-transcriptional levels that allow the respiratory apparatus of plants to help shape organ development and the response of plants to environmental stress. We highlight the challenges for future research considering spatial and temporal changes of respiration in response to changing climatic conditions.
Energy costs of salinity tolerance in crop plants
Publisher: Wiley
Date: 29-11-2019
DOI: 10.1111/NPH.15555
Development physiology of cluster-root carboxylate synthesis and exudation in harsh hakea. Expression of phosphoenolpyruvate carboxylase and the alternative oxidase
Publisher: Oxford University Press (OUP)
Date: 05-2004
Abstract: Harsh hakea (Hakea prostrata R.Br.) is a member of the Proteaceae family, which is highly represented on the extremely nutrient-impoverished soils in southwest Australia. When phosphorus is limiting, harsh hakea develops proteoid or cluster roots that release carboxylates that mobilize sparingly soluble phosphate in the rhizosphere. To investigate the physiology underlying the synthesis and exudation of carboxylates from cluster roots in Proteaceae, we measured O2 consumption, CO2 release, internal carboxylate concentrations and carboxylate exudation, and the abundance of the enzymes phosphoenolpyruvate carboxylase and alternative oxidase (AOX) over a 3-week time course of cluster-root development. Peak rates of citrate and malate exudation were observed from 12- to 13-d-old cluster roots, preceded by a reduction in cluster-root total protein levels and a reduced rate of O2 consumption. In harsh hakea, phosphoenolpyruvate carboxylase expression was relatively constant in cluster roots, regardless of developmental stage. During cluster-root maturation, however, the expression of AOX protein increased prior to the time when citrate and malate exudation peaked. This increase in AOX protein levels is presumably needed to allow a greater flow of electrons through the mitochondrial electron transport chain in the absence of rapid ATP turnover. Citrate and isocitrate synthesis and accumulation contributed in a major way to the subsequent burst of citrate and malate exudation. Phosphorus accumulated by harsh hakea cluster roots was remobilized during senescence as part of their efficient P cycling strategy for growth on nutrient impoverished soils.
Mitochondrial protein expression in tomato fruit during on-vine ripening and cold storage
Publisher: CSIRO Publishing
Date: 2002
DOI: 10.1071/PP01245
Abstract: We have investigated the activity and abundance of a number of respiratory chain components in ripening and cold-treated tomato fruits (Lycopersicon esculentum L. Mill cvv. Moneymaker and Sweetie). Expression of the alternative oxidase (AOX) protein increased dramatically in both situations. Levels of the plant uncoupling protein (UCP) initially fell, but increased substantially in the later stages of ripening. In contrast, ATP synthase subunits and the COXII subunit of cytochrome oxidase decreased during ripening and increased slightly in response to cold stress. Other proteins involved in electron transport, tricarboxylic acid cycle function, chaperonin function, and membrane transport were also studied. These showed varying degrees of enhanced and depressed expression patterns. There were modest changes in whole fruit respiratory activities, and electron transport capacity of isolated mitochondria in response to these stimuli. However, respiratory control by ADP in the isolated mitochondria decreased as AOX capacity and abundance increased, indicating that although total respiration rates changed little, flux between the coupled and uncoupled pathways altered. The changes observed in AOX and UCP accumulation in tomato fruit that were vine-ripened were significantly different from post-harvest ripening patterns previously reported. The altered protein profiles are discussed in the context of on- and off-vine ripening and the potentially different roles of uncoupled respiration in each situation.
Siderophore-bound iron in the peribacteroid space of soybean root nodules
Publisher: Springer Science and Business Media LLC
Date: 1996
DOI: 10.1007/BF00011579
Molecular and physiological responses during thermal acclimation of leaf photosynthesis and respiration in rice.
Publisher: Wiley
Date: 10-01-2020
DOI: 10.1111/PCE.13706
Abstract: To further our understanding of how sustained changes in temperature affect the carbon economy of rice (Oryza sativa), hydroponically grown plants of the IR64 cultivar were developed at 30°C/25°C (day/night) before being shifted to 25/20°C or 40/35°C. Leaf messenger RNA and protein abundance, sugar and starch concentrations, and gas-exchange and elongation rates were measured on preexisting leaves (PE) already developed at 30/25°C or leaves newly developed (ND) subsequent to temperature transfer. Following a shift in growth temperature, there was a transient adjustment in metabolic gene transcript abundance of PE leaves before homoeostasis was reached within 24 hr, aligning with R
Soybean SAT1 ( Symbiotic Ammonium Transporter 1 ) encodes a bHLH transcription factor involved in nodule growth and NH 4 + transport
Publisher: Proceedings of the National Academy of Sciences
Date: 19-03-2014
Abstract: The legume/rhizobia symbiosis involves a root-based exchange of bacterial fixed nitrogen for plant-derived photosynthetic carbon. The exchange takes place within the legume root nodule, which is a specialized root tissue that develops in response to plant and bacterial signal exchange. The bacteria reside within plant cells inside the nodule. In this study, we explore the activity of a membrane-bound soybean transcription factor, Glycine max basic–helix-loop–helix membrane 1, which is important for soybean nodule growth and is linked to the activity of a unique class of ammonium channels and to signaling cascades influencing a nodule circadian clock.
ATPASE ACTIVITY AND ANION TRANSPORT ACROSS THE PERIBACTEROID MEMBRANE OF ISOLATED SOYBEAN SYMBIOSOMES
Publisher: Springer Science and Business Media LLC
Date: 10-1991
DOI: 10.1007/BF00248711
AMMONIA (C-14-METHYLAMINE) TRANSPORT ACROSS THE BACTEROID AND PERIBACTEROID MEMBRANES OF SOYBEAN ROOT-NODULES
Publisher: Oxford University Press (OUP)
Date: 09-1990
DOI: 10.1104/PP.94.1.71
Stress-induced co-expression of alternative respiratory chain components in Arabidopsis thaliana
Publisher: Springer Science and Business Media LLC
Date: 05-2005
DOI: 10.1007/S11103-005-5514-7
Abstract: Plant mitochondria contain non-phosphorylating bypasses of the respiratory chain, catalysed by the alternative oxidase (AOX) and alternative NADH dehydrogenases (NDH), as well as uncoupling (UCP) protein. Each of these components either circumvents or short-circuits proton translocation pathways, and each is encoded by a small gene family in Arabidopsis. Whole genome microarray experiments were performed with suspension cell cultures to examine the effects of various 3 h treatments designed to induce abiotic stress. The expression of over 60 genes encoding components of the classical, phosphorylating respiratory chain and tricarboxylic acid cycle remained largely constant when cells were subjected to a broad range of abiotic stresses, but expression of the alternative components responded differentially to the various treatments. In detailed time-course quantitative PCR analysis, specific members of both AOX and NDH gene families displayed coordinated responses to treatments. In particular, the co-expression of AOX1a and NDB2 observed under a number of treatments suggested co-regulation that may be directed by common sequence elements arranged hierarchically in the upstream promoter regions of these genes. A series of treatment sets were identified, representing the response of specific AOX and NDH genes to mitochondrial inhibition, plastid inhibition and abiotic stresses. These treatment sets emphasise the multiplicity of pathways affecting alternative electron transport components in plants.
Salt-induced expression of intracellular vesicle trafficking genes, CaRab-GTP, and their association with Na+ accumulation in leaves of chickpea (Cicer arietinum L.)
Publisher: Springer Science and Business Media LLC
Date: 10-2020
DOI: 10.1186/S12870-020-02331-5
Abstract: Chickpea is an important legume and is moderately tolerant to salinity stress during the growing season. However, the level and mechanisms for salinity tolerance can vary among accessions and cultivars. A large family of CaRab -GTP genes, previously identified in chickpea, is homologous to intracellular vesicle trafficking superfamily genes that play essential roles in response to salinity stress in plants. To determine which of the gene family members are involved in the chickpea salt response, plants from six selected chickpea accessions (Genesis 836, Hattrick, ICC12726, Rupali, Slasher and Yubileiny) were exposed to salinity stress and expression profiles resolved for the major CaRab -GTP gene clades after 5, 9 and 15 days of salt exposure. Gene clade expression profiles (using degenerate primers targeting all members of each clade) were tested for their relationship to salinity tolerance measures, namely plant biomass and Na + accumulation. Transcripts representing 11 out of the 13 CaRab clades could be detected by RT-PCR, but only six ( CaRabA2 , −B , −C , −D , −E and − H ) could be quantified using qRT-PCR due to low expression levels or poor lification efficiency of the degenerate primers for clades containing several gene members. Expression profiles of three gene clades, CaRabB , −D and −E , were very similar across all six chickpea accessions, showing a strongly coordinated network. Salt-induced enhancement of CaRabA2 expression at 15 days showed a very strong positive correlation (R 2 = 0.905) with Na + accumulation in leaves. However, salinity tolerance estimated as relative plant biomass production compared to controls, did not correlate with Na + accumulation in leaves, nor with expression profiles of any of the investigated CaRab -GTP genes. A coordinated network of CaRab-GTP genes, which are likely involved in intracellular trafficking, are important for the salinity stress response of chickpea plants.
Targets of stress-induced oxidative damage in plant mitochondria and their impact on cell carbon/nitrogen metabolism
Publisher: Oxford University Press (OUP)
Date: 28-11-2004
DOI: 10.1093/JXB/ERH001
Identification of alternative mitochondrial electron transport pathway components in chickpea indicates a differential response to salinity stress between cultivars
Publisher: MDPI AG
Date: 28-05-2020
DOI: 10.3390/IJMS21113844
Abstract: All plants contain an alternative electron transport pathway (AP) in their mitochondria, consisting of the alternative oxidase (AOX) and type 2 NAD(P)H dehydrogenase (ND) families, that are thought to play a role in controlling oxidative stress responses at the cellular level. These alternative electron transport components have been extensively studied in plants like Arabidopsis and stress inducible isoforms identified, but we know very little about them in the important crop plant chickpea. Here we identify AP components in chickpea (Cicer arietinum) and explore their response to stress at the transcript level. Based on sequence similarity with the functionally characterized proteins of Arabidopsis thaliana, five putative internal (matrix)-facing NAD(P)H dehydrogenases (CaNDA1-4 and CaNDC1) and four putative external (inter-membrane space)-facing NAD(P)H dehydrogenases (CaNDB1-4) were identified in chickpea. The corresponding activities were demonstrated for the first time in purified mitochondria of chickpea leaves and roots. Oxidation of matrix NADH generated from malate or glycine in the presence of the Complex I inhibitor rotenone was high compared to other plant species, as was oxidation of exogenous NAD(P)H. In leaf mitochondria, external NADH oxidation was stimulated by exogenous calcium and external NADPH oxidation was essentially calcium dependent. However, in roots these activities were low and largely calcium independent. A salinity experiment with six chickpea cultivars was used to identify salt-responsive alternative oxidase and NAD(P)H dehydrogenase gene transcripts in leaves from a three-point time series. An analysis of the Na:K ratio and Na content separated these cultivars into high and low Na accumulators. In the high Na accumulators, there was a significant up-regulation of CaAOX1, CaNDB2, CaNDB4, CaNDA3 and CaNDC1 in leaf tissue under long term stress, suggesting the formation of a stress-modified form of the mitochondrial electron transport chain (mETC) in leaves of these cultivars. In particular, stress-induced expression of the CaNDB2 gene showed a striking positive correlation with that of CaAOX1 across all genotypes and time points. The coordinated salinity-induced up-regulation of CaAOX1 and CaNDB2 suggests that the mitochondrial alternative pathway of respiration is an important facet of the stress response in chickpea, in high Na accumulators in particular, despite high capacities for both of these activities in leaf mitochondria of non-stressed chickpeas.
The impact of oxidative stress on Arabidopsis mitochondria
Publisher: Wiley
Date: 12-2002
DOI: 10.1046/J.1365-313X.2002.01474.X
Abstract: Treatment of Arabidopsis cell culture for 16 h with H2O2, menadione or antimycin A induced an oxidative stress decreasing growth rate and increasing DCF fluorescence and lipid peroxidation products. Treated cells remained viable and maintained significant respiratory rates. Mitochondrial integrity was maintained, but accumulation of alternative oxidase and decreased abundance of lipoic acid-containing components during several of the treatments indicated oxidative stress. Analysis of the treatments was undertaken by IEF/SDS-PAGE, comparison of protein spot abundances and tandem mass spectrometry. A set of 25 protein spots increased >3-fold in H2O2/menadione treatments, a subset of these increased in antimycin A-treated s les. A set of 10 protein spots decreased significantly during stress treatments. A specific set of mitochondrial proteins were degraded by stress treatments. These damaged components included subunits of ATP synthase, complex I, succinyl CoA ligase, aconitase, and pyruvate and 2-oxoglutarate dehydrogenase complexes. Nine increased proteins represented products of different genes not found in control mitochondria. One is directly involved in antioxidant defense, a mitochondrial thioredoxin-dependent peroxidase, while another, a thioredoxin reductase-dependent protein disulphide isomerase, is required for protein disulfide redox homeostasis. Several others are generally considered to be extramitochondrial but are clearly present in a highly purified mitochondrial fraction used in this study and are known to play roles in stress response. Using H2O2 as a model stress, further work revealed that this treatment induced a protease activity in isolated mitochondria, putatively responsible for the degradation of oxidatively damaged mitochondrial proteins and that O2 consumption by mitochondria was significantly decreased by H2O2 treatment.
Cyclin-dependent Kinase E1 (CDKE1) Provides a Cellular Switch in Plants between Growth and Stress Responses
Publisher: Elsevier BV
Date: 02-2013
A DICARBOXYLATE TRANSPORTER ON THE PERIBACTEROID MEMBRANE OF SOYBEAN NODULES
Publisher: Wiley
Date: 11-04-1988
GmVTL1a is an iron transporter on the symbiosome membrane of soybean with an important role in nitrogen fixation
Publisher: Wiley
Date: 12-07-2020
DOI: 10.1111/NPH.16734
Abstract: Legumes establish symbiotic relationships with soil bacteria (rhizobia), housed in nodules on roots. The plant supplies carbon substrates and other nutrients to the bacteria in exchange for fixed nitrogen. The exchange occurs across a plant‐derived symbiosome membrane (SM), which encloses rhizobia to form a symbiosome. Iron supplied by the plant is crucial for rhizobial enzyme nitrogenase that catalyses nitrogen fixation, but the SM iron transporter has not been identified. We use yeast complementation, real‐time PCR and proteomics to study putative soybean ( Glycine max ) iron transporters GmVTL1a and GmVTL1b and have characterized the role of GmVTL1a using complementation in plant mutants, hairy root transformation and microscopy. GmVTL1a and GmVTL1b are members of the vacuolar iron transporter family and homologous to Lotus japonicus SEN1 (LjSEN1), which is essential for nitrogen fixation. GmVTL1a expression is enhanced in nodule infected cells and both proteins are localized to the SM. GmVTL1a transports iron in yeast and restores nitrogen fixation when expressed in the Ljsen1 mutant. Three GmVTL1a amino acid substitutions that block nitrogen fixation in Ljsen1 plants reduce iron transport in yeast. We conclude GmVTL1a is responsible for transport of iron across the SM to bacteroids and plays a crucial role in the nitrogen‐fixing symbiosis.
Localization of H+ -ATPase in soybean root nodules
Publisher: Springer Science and Business Media LLC
Date: 19-07-1999
Abstract: The localization of H(+)-ATPases in soybean (Glycine max L. cv. Stevens) nodules was investigated using antibodies against both P-type and V-type enzymes. Immunoblots of peribacteroid membrane (PBM) proteins using antibodies against tobacco and Arabidopsis H(+)-ATPases detected a single immunoreactive band at approximately 100 kDa. These antibodies recognized a protein of similar relative molecular mass in the crude microsomal fraction from soybean nodules and uninoculated roots. The amount of this protein was greater in PBM from mature nodules than in younger nodules. Immunolocalization of P-type ATPases using silver enhancement of colloidal-gold labelling at the light-microscopy level showed signal distributed around the periphery of non-infected cells in both the nodule cortex and nodule parenchyma. In the central nitrogen-fixing zone of the nodule, staining was present in both the infected and uninfected cells. Examination of nodule sections using confocal microscopy and fluorescence staining showed an immunofluorescent signal clearly visible around the periphery of in idual symbiosomes which appeared as vesicles distributed throughout the infected cells of the central zone. Electron-microscopic examination of immunogold-labelled sections shows that P-type ATPase antigens were present on the PBM of both newly formed, single-bacteroid symbiosomes just released from infection threads, and on the PBM of mature symbiosomes containing two to four bacteroids. Immunogold labelling using antibody against the B-subunit of V-type ATPase from oat failed to detect this protein on symbiosome membranes. Only a very faint signal with this antibody was detected on Western blots of purified PBM. During nodule development, fusion of small symbiosomes to form larger ones containing multiple bacteroids was observed. Fusion was preceded by the formation of cone-like extensions of the PBM, allowing the membrane to make contact with the adjoining membrane of another symbiosome. We conclude that the major H(+)-ATPase on the PBM of soybean is a P-type enzyme with homology to other such enzymes in plants. In vivo, this enzyme is likely to play a critical role in the regulation of nutrient exchange between legume and bacteroids.
Molecular Distinction between Alternative Oxidase from Monocots and Dicots
Publisher: Oxford University Press (OUP)
Date: 07-2002
DOI: 10.1104/PP.004150
Environmental stress causes oxidative damage to plant mitochondria leading to inhibition of glycine decarboxylase
Publisher: Elsevier BV
Date: 11-2002
Respiratory gene expression in soybean cotyledons during post-germinative development
Publisher: Springer Science and Business Media LLC
Date: 2003
Abstract: Gene expression for nuclear- and mitochondrial-encoded subunits of respiratory chain components was measured in developing soybean cotyledons and compared to the abundance of the relevant proteins. Overall respiratory gene expression peaked at day 16, close to the peak in cytochrome chain and TCA cycle activities from day 10 to 15. Protein abundance followed transcript abundance for all components examined with the exception of the F1beta subunit of ATP synthase. A dramatic peak in F1beta transcript levels early in development (day 5 to 7) was not mirrored by an increase in protein suggesting translational or post-translational control. Mitochondrial-encoded transcripts were at least 10-fold more abundant than nuclear-encoded transcripts. The pattern of transcript and protein abundance for uncoupling proteins displayed a trend similar to other respiratory proteins examined, implicating similar control mechanisms. The expression of alternative oxidase differed, increasing throughout development with protein peaking at day 20, perhaps suggesting a role in senescence. Overall, this study indicated that respiratory gene expression and protein abundance is co-ordinated with respiratory activity for most components but that some components, such as the F1beta subunit may be under discrete forms of regulation.
Proteomic identification of divalent metal cation binding proteins in plant mitochondria
Publisher: Wiley
Date: 07-02-2003
DOI: 10.1016/S0014-5793(03)00101-7
Abstract: Divalent metal binding proteins in the Arabidopsis mitochondrial proteome were analysed by mobility shifts in the presence of alent cations during two-dimensional diagonal sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Tandem mass spectrometry and searches of the predicted Arabidopsis protein dataset were used in an attempt to identify 34 of the proteins which shifted. This analysis identified a total of 23 distinct protein spots as the products of at least 11 different Arabidopsis genes. A series of proteins known to be alent cation-binding proteins, or to catalyse alent cation-dependent reactions, were identified. These included: succinyl CoA ligase beta subunit, Mn-superoxide dismutase (SOD), an Fe-S centred component of complex I and the REISKE iron-sulphur protein of the b/c(1) complex. A further set of four proteins of known function but without known alent binding properties were also identified: the Vb subunit of cytochrome c oxidase, a subunit of ATP synthase (orfB), the acyl carrier protein, and the translocase of the outer membrane (TOM20). Three other proteins, of unknown function, were also found to shift in the presence of alent cations. This approach has broad application for the identification of sub-proteomes based on the metal interaction of polypeptides.
Lipoic Acid-Dependent Oxidative Catabolism of α-Keto Acids in Mitochondria Provides Evidence for Branched-Chain Amino Acid Catabolism in Arabidopsis
Publisher: Oxford University Press (OUP)
Date: 02-2004
Abstract: Lipoic acid-dependent pathways of α-keto acid oxidation by mitochondria were investigated in pea (Pisum sativum), rice (Oryza sativa), and Arabidopsis. Proteins containing covalently bound lipoic acid were identified on isoelectric focusing/sodium dodecyl sulfate-polyacrylamide gel electrophoresis separations of mitochondrial proteins by the use of antibodies raised to this cofactor. All these proteins were identified by tandem mass spectrometry. Lipoic acid-containing acyltransferases from pyruvate dehydrogenase complex and α-ketoglutarate dehydrogenase complex were identified from all three species. In addition, acyltransferases from the branched-chain dehydrogenase complex were identified in both Arabidopsis and rice mitochondria. The substrate-dependent reduction of NAD+ was analyzed by spectrophotometry using specific α-keto acids. Pyruvate- and α-ketoglutarate-dependent reactions were measured in all three species. Activity of the branched-chain dehydrogenase complex was only measurable in Arabidopsis mitochondria using substrates that represented the α-keto acids derived by deamination of branched-chain amino acids (Val [valine], leucine, and isoleucine). The rate of branched-chain amino acid- and α-keto acid-dependent oxygen consumption by intact Arabidopsis mitochondria was highest with Val and the Val-derived α-keto acid, α-ketoisovaleric acid. Sequencing of peptides derived from trypsination of Arabidopsis mitochondrial proteins revealed the presence of many of the enzymes required for the oxidation of all three branched-chain amino acids. The potential role of branched-chain amino acid catabolism as an oxidative phosphorylation energy source or as a detoxification pathway during plant stress is discussed.
Soybean Yellow Stripe-like7 is a symbiosome membrane peptide transporter essential for nitrogen fixation
Publisher: Cold Spring Harbor Laboratory
Date: 29-03-2020
DOI: 10.1101/2020.03.27.011973
Abstract: Legumes form a symbiosis with rhizobia that convert atmospheric nitrogen (N 2 ) to ammonia which they provide to the plant in return for a carbon and nutrient supply. Nodules, developed as part of the symbiosis, harbor rhizobia which are enclosed in the plant-derived symbiosome membrane (SM), to form a symbiosome. In the mature nodule all exchanges between the symbionts occur across the SM. Here we characterize GmYSL7, a member of Yellow stripe-like family which is localized to the SM in soybean nodules. It is expressed specifically in nodule infected cells with expression peaking soon after nitrogenase becomes active. Although most members of the family transport metal complexed with phytosiderophores, GmYSL7 does not. It transports oligopeptides of between four and 12 amino acids. Silencing of GmYSL7 reduces nitrogenase activity and blocks development when symbiosomes contain a single bacteroid. RNAseq of nodules in which GmYSL7 is silenced suggests that the plant initiates a defense response against the rhizobia. There is some evidence that metal transport in the nodules is dysregulated, with upregulation of genes encoding ferritin and vacuolar iron transporter family and downregulation of a gene encoding nicotianamine synthase. However, it is not clear whether the changes are a result of the reduction of nitrogen fixation and the requirement to store excess iron or an indication of a role of GmYSL7 in regulation of metal transport in the nodules. Further work to identify the physiological substrate for GmYSL7 will allow clarification of this role. GmYSL7 is a symbiosome membrane peptide transporter that is essential for symbiotic nitrogen fixation that when silenced blocks symbiosome development.
Nonlinear Reduction in Hyperautofluorescent Ring Area in Retinitis Pigmentosa
Publisher: Elsevier BV
Date: 09-2023
Dark respiration rates are not determined by differences in mitochondrial capacity, abundance and ultrastructure in C4 leaves
Publisher: Wiley
Date: 06-02-2022
DOI: 10.1111/PCE.14267
Abstract: Our understanding of the regulation of respiration in C 4 plants, where mitochondria play different roles in the different types of C 4 photosynthetic pathway, remains limited. We examined how leaf dark respiration rates ( R dark ), in the presence and absence of added malate, vary in monocots representing the three classical biochemical types of C 4 photosynthesis (NADP‐ME, NAD‐ME and PCK) using intact leaves and extracted bundle sheath strands. In particular, we explored to what extent rates of R dark are associated with mitochondrial number, volume and ultrastructure. Based on examination of a single species per C 4 type, we found that the respiratory response of NAD‐ME and PCK type bundle sheath strands to added malate was associated with differences in mitochondrial number, volume, and/or ultrastructure, while NADP‐ME type bundle sheath strands did not respond to malate addition. In general, mitochondrial traits reflected the contributions mitochondria make to photosynthesis in the three C 4 types. However, despite the obvious differences in mitochondrial traits, no clear correlation was observed between these traits and R dark . We suggest that R dark is primarily driven by cellular maintenance demands and not mitochondrial composition per se, in a manner that is somewhat independent of mitochondrial organic acid cycling in the light.
What makes a mitochondrion?
Publisher: Springer Science and Business Media LLC
Date: 2003
Identification of intra- and intermolecular disulphide bonding in the plant mitochondrial proteome by diagonal gel electrophoresis
Publisher: Wiley
Date: 11-2007
Abstract: Redox active proteins in plant mitochondria were examined using 2-D oxidant/reductant diagonal-SDS-PAGE to separate and identify proteins with intermolecular or intramolecular disulphide bonds using diamide in the first dimension and DTT in the second dimension. Eighteen proteins spots were resolved either above or below the diagonal and these were in-gel digested and identified by MS/MS. This analysis revealed intermolecular disulphide bonds in alternative oxidase, O-acetylserine (thiol) lyase, citrate synthase and between subunits of the ATP synthase. Intramolecular disulphide bonds were observed in a range of mitochondrial dehydrogenases, elongation factor Tu, adenylate kinase and the phosphate translocator. Many of the soluble proteins found were known glutaredoxin/thioredoxin targets in other plants, but the membrane proteins were not found by these methods nor were the nature of the disulphides able to be investigated. The accessibility of thiols involved in disulphide bonds to modification by a lipid derived aldehyde gave an insight into the potential impact of Cys modification on redox-functions in mitochondria during lipid peroxidation. Comparison of the protein sequences of the identified proteins with homologs from other species has identified specific Cys residues that may be responsible for plant-specific redox modulations of mitochondrial proteins.
The soybean NRAMP homologue, GmDMT1, is a symbiotic divalent metal transporter capable of ferrous iron transport
Publisher: Wiley
Date: 08-07-2003
DOI: 10.1046/J.1365-313X.2003.01802.X
Abstract: Iron is an important nutrient in N2-fixing legume root nodules. Iron supplied to the nodule is used by the plant for the synthesis of leghemoglobin, while in the bacteroid fraction, it is used as an essential cofactor for the bacterial N2-fixing enzyme, nitrogenase, and iron-containing proteins of the electron transport chain. The supply of iron to the bacteroids requires initial transport across the plant-derived peribacteroid membrane, which physically separates bacteroids from the infected plant cell cytosol. In this study, we have identified Glycine max alent metal transporter 1 (GmDmt1), a soybean homologue of the NRAMP/Dmt1 family of alent metal ion transporters. GmDmt1 shows enhanced expression in soybean root nodules and is most highly expressed at the onset of nitrogen fixation in developing nodules. Antibodies raised against a partial fragment of GmDmt1 confirmed its presence on the peribacteroid membrane (PBM) of soybean root nodules. GmDmt1 was able to both rescue growth and enhance 55Fe(II) uptake in the ferrous iron transport deficient yeast strain (fet3fet4). The results indicate that GmDmt1 is a nodule-enhanced transporter capable of ferrous iron transport across the PBM of soybean root nodules. Its role in nodule iron homeostasis to support bacterial nitrogen fixation is discussed.
Transport processes of the legume symbiosome membrane
Publisher: Frontiers Media SA
Date: 15-12-2014
Differential impact of environmental stresses on the pea mitochondrial proteome
Publisher: Elsevier BV
Date: 08-2005
A tomato alternative oxidase protein with altered regulatory properties
Publisher: Elsevier BV
Date: 09-4220
DOI: 10.1016/S0005-2728(03)00112-9
Abstract: We have investigated the expression and regulatory properties of the two alternative oxidase (Aox) proteins that are expressed in tomato (Lycopersicon esculentum L. Mill cv. Sweetie) after storage of green fruit at 4 degrees C. Four Aox genes were identified in the tomato genome, of which two (LeAox1a and LeAox1b) were demonstrated to be expressed in cold-treated fruit. The activity and regulatory properties of LeAox1a and LeAox1b were assayed after expression of each protein in yeast cells (Saccharomyces cerevisiae), proving that each is an active Aox protein. The LeAox1b protein was shown to have altered regulatory properties due to the substitution of a Ser for the highly conserved Cys(I) residue. LeAox1b could not form inactive disulfide-linked dimers and was activated by succinate instead of pyruvate. This is the first ex le of a dicot species expressing a natural Cys(I)/Ser isoform. The implications of the existence and expression of such Aox isoforms is discussed in the light of the hypothesised role for Aox in plant metabolism.
ELECTROGENIC ATPASE ACTIVITY ON THE PERIBACTEROID MEMBRANE OF SOYBEAN (GLYCINE-MAX L) ROOT-NODULES
Publisher: Oxford University Press (OUP)
Date: 07-1989
DOI: 10.1104/PP.90.3.982
Sensitivity of plant mitochondrial terminal oxidases to the lipid peroxidation product 4-hydroxy-2-nonenal (HNE)
Publisher: Portland Press Ltd.
Date: 26-04-2005
DOI: 10.1042/BJ20042044
Abstract: We have investigated the effect of the lipid peroxidation product, HNE (4-hydroxy-2-nonenal), on plant mitochondrial electron transport. In mitochondria isolated from Arabidopsis thaliana cell cultures, HNE inhibited succinate-dependent oxygen consumption via the Aox (alternative oxidase), but had minimal effect on respiration via Cox (cytochrome c oxidase). Maximal Cox activity, measured with reduced cytochrome c as substrate, was only slightly inhibited by high concentrations of HNE, at which Aox was completely inhibited. Incubation with HNE prevented dimerization of the Aox protein, suggesting that one site of modification was the conserved cysteine residue involved in dimerization and activation of this enzyme (CysI). However, a naturally occurring isoform of Aox lacking CysI and unable to be dimerized, LeAox1b from tomato (Lycopersicon esculentum), was equally sensitive to HNE inhibition, showing that other amino acid residues in Aox also interact with HNE. The presence of HNE in vivo in Arabidopsis cell cultures was also investigated. Induction of oxidative stress in the cell cultures by the addition of hydrogen peroxide, antimycin A or menadione, caused a significant increase in hydroxyalkenals (of which HNE is the most prominent). Western blotting of mitochondrial proteins with antibodies against HNE adducts, demonstrated significant modification of proteins during these treatments. The implications of these results for the response of plants to reactive oxygen species are discussed.
Experimental Analysis of the Arabidopsis Mitochondrial Proteome Highlights Signaling and Regulatory Components, Provides Assessment of Targeting Prediction Programs, and Indicates Plant-Specific Mitoc
Publisher: Oxford University Press (OUP)
Date: 2004
DOI: 10.1105/TPC.016055
Abstract: A novel insight into Arabidopsis mitochondrial function was revealed from a large experimental proteome derived by liquid chromatography–tandem mass spectrometry. Within the experimental set of 416 identified proteins, a significant number of low-abundance proteins involved in DNA synthesis, transcriptional regulation, protein complex assembly, and cellular signaling were discovered. Nearly 20% of the experimentally identified proteins are of unknown function, suggesting a wealth of undiscovered mitochondrial functions in plants. Only approximately half of the experimental set is predicted to be mitochondrial by targeting prediction programs, allowing an assessment of the benefits and limitations of these programs in determining plant mitochondrial proteomes. Maps of putative orthology networks between yeast, human, and Arabidopsis mitochondrial proteomes and the Rickettsia prowazekii proteome provide detailed insights into the ergence of the plant mitochondrial proteome from those of other eukaryotes. These show a clear set of putative cross-species orthologs in the core metabolic functions of mitochondria, whereas considerable ersity exists in many signaling and regulatory functions.
Organic acid activation of the alterNatlve oxidase of plant mitochondria
Publisher: Wiley
Date: 30-08-1993
DOI: 10.1016/0014-5793(93)80233-K
Abstract: Alternative oxidase activity (oxygen uptake in the presence of KCN, antimycin or myxothiazol) in mitochondria isolated from the roots of soybean seedlings was very slow, even with succinate as substrate. This activity was stimulated substantially (100-400%) by the addition of pyruvate, with half maximal stimulation occurring at 0.1 mM pyruvate. Mitochondria from soybean shoots displayed high alternative oxidase activity with succinate and malate as substrates but lower activity with exogenous NADH addition of pyruvate stimulated the activity with NADH up to that seen with succinate. This stimulation of cyanide-insensitive NADH oxidation was seen also with mitochondria from other species. Hydroxypyruvate and oxoglutarate could substitute for pyruvate, although higher concentrations were required to achieve maximum stimulation. Pyruvate stimulation of cyanide-insensitive oxygen uptake was observed with exogenous quinols as substrates, with sub-mitochondrial particles, and in the presence of the pyruvate transport inhibitor, cyanohydroxycinnamic acid, but was not observed with detergent-solubilised mitochondria. It is suggested that pyruvate acts allosterically on the alternative oxidase to stimulate its activity. The implications of these findings for respiration in vivo are discussed.
Salicylic acid is an uncoupler and inhibitor of mitochondrial electron transport
Publisher: Oxford University Press (OUP)
Date: 2004
Abstract: The effect of salicylic acid (SA) on respiration and mitochondrial function was examined in tobacco (Nicotiana tabacum) suspension cell cultures in the range of 0.01 to 5 mm. Cells rapidly accumulated SA up to 10-fold of the externally applied concentrations. At the lower concentrations, SA accumulation was transitory. When applied at 0.1 mm or less, SA stimulated respiration of whole cells and isolated mitochondria in the absence of added ADP, indicating uncoupling of respiration. However, at higher concentrations, respiration was severely inhibited. Measurements of ubiquinone redox poise in isolated mitochondria suggested that SA blocked electron flow from the substrate dehydrogenases to the ubiquinone pool. This inhibition could be at least partially reversed by re-isolating the mitochondria. Two active analogs of SA, benzoic acid and acetyl-SA, had the same effect as SA on isolated tobacco mitochondria, whereas the inactive p-hydroxybenzoic acid was without effect at the same concentration. SA induced an increase in Aox protein levels in cell suspensions, and this was correlated with an increase in Aox1 transcript abundance. However, when applied at 0.1 mm, this induction was transient and disappeared as SA levels in the cells declined. SA at 0.1 mm also increased the expression of other SA-responsive genes, and this induction was dependent on active mitochondria. The results indicate that SA is both an uncoupler and an inhibitor of mitochondrial electron transport and suggest that this underlies the induction of some genes by SA. The possible implications of this for the interpretation of SA action in plants are discussed.
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