| 1. |
- Møller, Ian Max, et al.
(författare)
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Isolation of Highly Purified, Intact, and Functional Mitochondria from Potato Tubers Using a Two-in-One Percoll Density Gradient
- 2022
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Ingår i: Plant Mitochondria : Methods and Protocols - Methods and Protocols. - New York, NY : Springer US. - 1064-3745 .- 1940-6029. - 9781071616536 - 9781071616529 ; 2363, s. 39-50
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Bokkapitel (refereegranskat)abstract
- The isolation of mitochondria from potato tubers (Solanum tuberosum L.) is described, but the methodology can easily be adapted to other storage tissues. After homogenization of the tissue, filtration and differential centrifugation, the key step is a Percoll density gradient centrifugation. The Percoll gradient contains two parts: a bottom part containing Percoll in 0.3 M sucrose, and a slightly less dense top part containing Percoll in 0.3 M mannitol. After centrifugation, a density gradient is formed that is almost linear in the central part, and this is where the band containing the purified intact mitochondria is formed. This method makes it possible to process large amounts of plant material (2–6 kg) and saves at least 1.5 h on the preparation time compared to methods where two consecutive purification methods are used. Nonetheless, it yields large amounts of mitochondria (50–125 mg protein) of very high purity, intactness and functionality.
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| 2. |
- Rasmusson, Allan G., et al.
(författare)
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Assessment of Respiratory Enzymes in Intact Cells by Permeabilization with Alamethicin
- 2022
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Ingår i: Plant Mitochondria : Methods and Protocols - Methods and Protocols. - New York, NY : Springer US. - 1940-6029 .- 1064-3745. - 9781071616536 - 9781071616529 ; 2363, s. 77-84
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Bokkapitel (refereegranskat)abstract
- We here describe measurements of respiratory enzymes in situ, which can be done on very small cell samples and make mitochondrial isolation unnecessary. The method is based on the ability of the fungal peptide alamethicin to permeate biological membranes from the net positively charged side, and form nonspecific ion channels. These channels allow rapid transport of substrates and products across the plasma membrane, the inner mitochondrial membrane, and the inner plastid envelope. In this way, mitochondrial enzyme activities can be studied without disrupting the cells. The enzymes can be investigated in their natural proteinaceous environment and the activity of enzymes, also those sensitive to detergents or to dilution, can be quantified on a whole cell basis. We here present protocols for in situ measurement of two mitochondrial enzymatic activities: malate oxidation measured as oxygen consumption by the electron transport chain, which is sensitive to detergents, and NAD+-isocitrate dehydrogenase, a tricarboxylic acid cycle enzyme that dissociates upon dilution.
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| 3. |
- Browse, John A., et al.
(författare)
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Respiration and Lipid Metabolism
- 2014. - 6th ed.
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Ingår i: Plant Physiology and Development. - 9781605352558 - 9781605354354 ; , s. 317-352
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Bokkapitel (refereegranskat)
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| 4. |
- Bykova, Natalia V., et al.
(författare)
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Two separate transhydrogenase activities are present in plant mitochondria
- 1999
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Ingår i: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 265:1, s. 106-111
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Tidskriftsartikel (refereegranskat)abstract
- Inside-out submitochondrial particles from both potato tubers and pea leaves catalyze the transfer of hydride equivalents from NADPH to NAD+ as monitored with a substrate-regenerating system. The NAD+ analogue acetylpyridine adenine dinucleotide is also reduced by NADPH and incomplete inhibition by the complex I inhibitor diphenyleneiodonium (DPI) indicates that two enzymes are involved in this reaction. Gel-filtration chromatography of solubilized mitochondrial membrane complexes confirms that the DPI-sensitive TH activity is due to NADH-ubiquinone oxidoreductase (EC 1.6.5.3, complex I), whereas the DPI-insensitive activity is due to a separate enzyme eluting around 220 kDa. The DPI-insensitive TH activity is specific for the 4B proton on NADH, whereas there is no indication of a 4A-specific activity characteristic of a mammalian-type energy-linked TH. The DPI-insensitive TH may be similar to the soluble type of transhydrogenase found in, e.g., Pseudomonas. The presence of non-energy-linked TH activities directly coupling the matrix NAD(H) and NADP(H) pools will have important consequences for the regulation of NADP-linked processes in plant mitochondria.
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| 5. |
- Catania, Alessia, et al.
(författare)
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Arabidopsis thaliana alternative dehydrogenases : A potential therapy for mitochondrial complex i deficiency? Perspectives and pitfalls
- 2019
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Ingår i: Orphanet Journal of Rare Diseases. - : Springer Science and Business Media LLC. - 1750-1172. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Complex I (CI or NADH:ubiquinone oxidoreductase) deficiency is the most frequent cause of mitochondrial respiratory chain defect. Successful attempts to rescue CI function by introducing an exogenous NADH dehydrogenase, such as the NDI1 from Saccharomyces cerevisiae (ScNDI1), have been reported although with drawbacks related to competition with CI. In contrast to ScNDI1, which is permanently active in yeast naturally devoid of CI, plant alternative NADH dehydrogenases (NDH-2) support the oxidation of NADH only when the CI is metabolically inactive and conceivably when the concentration of matrix NADH exceeds a certain threshold. We therefore explored the feasibility of CI rescue by NDH-2 from Arabidopsis thaliana (At) in human CI defective fibroblasts. Results: We showed that, other than ScNDI1, two different NDH-2 (AtNDA2 and AtNDB4) targeted to the mitochondria were able to rescue CI deficiency and decrease oxidative stress as indicated by a normalization of SOD activity in human CI-defective fibroblasts. We further demonstrated that when expressed in human control fibroblasts, AtNDA2 shows an affinity for NADH oxidation similar to that of CI, thus competing with CI for the oxidation of NADH as opposed to our initial hypothesis. This competition reduced the amount of ATP produced per oxygen atom reduced to water by half in control cells. Conclusions: In conclusion, despite their promising potential to rescue CI defects, due to a possible competition with remaining CI activity, plant NDH-2 should be regarded with caution as potential therapeutic tools for human mitochondrial diseases.
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| 6. |
- Dotson, Bradley R., et al.
(författare)
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The antibiotic peptaibol alamethicin from Trichoderma permeabilises Arabidopsis root apical meristem and epidermis but is antagonised by cellulase-induced resistance to alamethicin
- 2018
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Ingår i: BMC Plant Biology. - : Springer Science and Business Media LLC. - 1471-2229. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Trichoderma fungi live in the soil rhizosphere and are beneficial for plant growth and pathogen resistance. Several species and strains are currently used worldwide in co-cultivation with crops as a biocontrol alternative to chemical pesticides even though little is known about the exact mechanisms of the beneficial interaction. We earlier found alamethicin, a peptide antibiotic secreted by Trichoderma, to efficiently permeabilise cultured tobacco cells. However, pre-treatment with Trichoderma cellulase made the cells resistant to subsequent alamethicin, suggesting a potential mechanism for plant tolerance to Trichoderma, needed for mutualistic symbiosis. Results: We here investigated intact sterile-grown Arabidopsis thaliana seedlings germinated in water or growth medium. These could be permeabilised by alamethicin but not if pretreated with cellulase. By following the fluorescence from the membrane-impermeable DNA-binding probe propidium iodide, we found alamethicin to mainly permeabilise root tips, especially the apical meristem and epidermis cells, but not the root cap and basal meristem cells nor cortex cells. Alamethicin permeabilisation and cellulase-induced resistance were confirmed by developing a quantitative in situ assay based on NADP-isocitrate dehydrogenase accessibility. The combined assays also showed that hyperosmotic treatment after the cellulase pretreatment abolished the induced cellulase resistance. Conclusion: We here conclude the presence of cell-specific alamethicin permeabilisation, and cellulase-induced resistance to it, in root tip apical meristem and epidermis of the model organism A. thaliana. We suggest that contact between the plasma membrane and the cell wall is needed for the resistance to remain. Our results indicate a potential mode for the plant to avoid negative effects of alamethicin on plant growth and localises the point of potential damage and response. The results also open up for identification of plant genetic components essential for beneficial effects from Trichoderma on plants.
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| 7. |
- Fan, Kaijian, et al.
(författare)
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The pentatricopeptide repeat protein EMP603 is required for the splicing of mitochondrial Nad1 intron 2 and seed development in maize
- 2021
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Ingår i: Journal of Experimental Botany. - : Oxford University Press (OUP). - 0022-0957 .- 1460-2431. ; 72:20, s. 6933-6948
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Tidskriftsartikel (refereegranskat)abstract
- Intron splicing is an essential event in post-transcriptional RNA processing in plant mitochondria, which requires the participation of diverse nuclear-encoded splicing factors. However, it is presently unclear how these proteins cooperatively take part in the splicing of specific introns. In this study, we characterized a nuclear-encoded mitochondrial P-type pentatricopeptide repeat (PPR) protein named EMP603. This protein is essential for splicing of intron 2 in the Nad1 gene and interacts with the mitochondria-localized DEAD-box RNA helicase PMH2-5140, the RAD52-like proteins ODB1-0814 and ODB1-5061, and the CRM domain-containing protein Zm-mCSF1. Further study revealed that the N-terminal region of EMP603 interacts with the DEAD-box of PMH2-5140, the CRM domain of Zm-mCSF1, and OBD1-5061, but not with OBD1-0814, whereas the PPR domain of EMP603 can interact with ODB1-0814, ODB1-5061, and PMH2-5140, but not with Zm-mCSF1. Defects in EMP603 severely disrupt the assembly and activity of mitochondrial complex I, leading to impaired mitochondrial function, and delayed seed development. The interactions revealed between EMP603 and PMH2-5140, ODB1-0814, ODB1-5061, and Zm-mCSF1 indicate a possible involvement of a dynamic 'spliceosome-like' complex in intron splicing, and may accelerate the elucidation of the intron splicing mechanism in plant mitochondria.
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| 8. |
- Fredlund, Kenneth M., et al.
(författare)
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Oxidation of external NAD(P)H by purified mitochondria from fresh and aged red beetroots (Beta vulgaris L.)
- 1991
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 97:1, s. 99-103
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Tidskriftsartikel (refereegranskat)abstract
- Mitochondria were isolated from fresh beetroots (Beta vulgaris L. cvs Rubria and Nina) by differential centrifugation followed by Percoll gradient centrifugation. These purified mitochondria oxidized external NADH, although relatively slowly (20-40 versus 100-120 nanomoles oxygen per minute times milligram protein for NADH and succinate oxidation, respectively), with respiratory control ratios of two to three and ADP/O ratios of 1.2 to 1.6. NADPH was also oxidized, but even more slowly and with little or no coupling. The optimum for both NADH and NADPH oxidation by fresh beetroot mitochondria was pH 6. The rate of external NADH oxidation by isolated mitochondria was enhanced threefold during storage of the intact tubers at 10°C for 12 weeks. The optimum of the induced NADH oxidation was approximately pH 6.8. Succinate and malate oxidation only increased by 30% during the same period and NADPH oxidation was constant. This is strong evidence that NADH and NADPH oxidation are catalyzed by different enzymes at least in beetroots. Activity staining of nondenaturing polyacrylamide gels with NADH and Nitro Blue Tetrazolium did not show differences in banding pattern between mitochondria isolated from fresh and stored beetroots. The induction is discussed in relation to physiological aging processes.
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| 9. |
- Glab, Bartosz, et al.
(författare)
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Cloning of Glycerophosphocholine Acyltransferase (GPCAT) from Fungi and Plants A NOVEL ENZYME IN PHOSPHATIDYLCHOLINE SYNTHESIS
- 2016
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Ingår i: Journal of Biological Chemistry. - : AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC. - 0021-9258 .- 1083-351X. ; 291:48, s. 25066-25076
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Tidskriftsartikel (refereegranskat)abstract
- Glycero-3-phosphocholine (GPC), the product of the complete deacylation of phosphatidylcholine (PC), was long thought to not be a substrate for reacylation. However, it was recently shown that cell-free extracts from yeast and plants could acylate GPC with acyl groups from acyl-CoA. By screening enzyme activities of extracts derived from a yeast knock-out collection, we were able to identify and clone the yeast gene (GPC1) encoding the enzyme, named glycerophosphocholine acyltransferase (GPCAT). By homology search, we also identified and cloned GPCAT genes from three plant species. All enzymes utilize acyl-CoA to acylate GPC, forming lyso-PC, and they show broad acyl specificities in both yeast and plants. In addition to acyl-CoA, GPCAT efficiently utilizes LPC and lysophosphatidylethanolamine as acyl donors in the acylation of GPC. GPCAT homologues were found in the major eukaryotic organism groups but not in prokaryotes or chordates. The enzyme forms its own protein family and does not contain any of the acyl binding or lipase motifs that are present in other studied acyltransferases and transacylases. In vivo labeling studies confirm a role for Gpc1p in PC biosynthesis in yeast. It is postulated that GPCATs contribute to the maintenance of PC homeostasis and also have specific functions in acyl editing of PC (e.g. in transferring acyl groups modified at the sn-2 position of PC to the sn-1 position of this molecule in plant cells).
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| 10. |
- Hao, Meng-Shu, et al.
(författare)
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The Ca2+-Regulation of the Mitochondrial External NADPH Dehydrogenase in Plants Is Controlled by Cytosolic pH
- 2015
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:9
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Tidskriftsartikel (refereegranskat)abstract
- NADPH is a key reductant carrier that maintains internal redox and antioxidant status, and that links biosynthetic, catabolic and signalling pathways. Plants have a mitochondrial external NADPH oxidation pathway, which depends on Ca2+ and pH in vitro, but concentrations of Ca2+ needed are not known. We have determined the K-0.5(Ca2+) of the external NADPH dehydrogenase from Solanum tuberosum mitochondria and membranes of E. coli expressing Arabidopsis thaliana NDB1 over the physiological pH range using O-2 and decylubiquinone as electron acceptors. The K-0.5(Ca2+) of NADPH oxidation was generally higher than for NADH oxidation, and unlike the latter, it depended on pH. At pH 7.5, K-0.5(Ca2+) for NADPH oxidation was high (approximate to 100 mu M), yet 20-fold lower K-0.5(Ca2+) values were determined at pH 6.8. Lower K-0.5(Ca2+) values were observed with decylubiquinone than with O-2 as terminal electron acceptor. NADPH oxidation responded to changes in Ca2+ concentrations more rapidly than NADH oxidation did. Thus, cytosolic acidification is an important activator of external NADPH oxidation, by decreasing the Ca2+-requirements for NDB1. The results are discussed in relation to the present knowledge on how whole cell NADPH redox homeostasis is affected in plants modified for the NDB1 gene.
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| 11. |
- Hao, Mengshu, et al.
(författare)
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The evolution of substrate specificity-associated residues and Ca2+-binding motifs in EF-hand-containing type II NAD(P)H dehydrogenases
- 2016
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Ingår i: Physiologia Plantarum. - : WILEY. - 0031-9317 .- 1399-3054. ; 157:3, s. 338-351
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Tidskriftsartikel (refereegranskat)abstract
- Most eukaryotic organisms, except some animal clades, have mitochondrial alternative electron transport enzymes that allow respiration to bypass the energy coupling in oxidative phosphorylation. The energy bypass enzymes in plants include the external type II NAD(P)H dehydrogenases (DHs) of the NDB family, which are characterized by an EF-hand domain for Ca2+ binding. Here we investigate these plant enzymes by combining molecular modeling with evolutionary analysis. Molecular modeling of the Arabidopsis thalianaAtNDB1 with the yeast ScNDI1 as template revealed distinct similarities in the core catalytic parts, and highlighted the interaction between the pyridine nucleotide and residues correlating with NAD(P)H substrate specificity. The EF-hand domain of AtNDB1 has no counterpart in ScNDI1, and was instead modeled with Ca2+-binding signal transducer proteins. Combined models displayed a proximity of the AtNDB1 EF-hand domain to the substrate entrance side of the catalytic part. Evolutionary analysis of the eukaryotic NDB-type proteins revealed ancient and recent reversions between the motif observed in proteins specific for NADH (acidic type) and NADPH (non-acidic type), and that the clade of enzymes with acidic motifs in angiosperms derives from non-acidic-motif NDB-type proteins present in basal plants, fungi and protists. The results suggest that Ca2+-dependent external NADPH oxidation is an ancient process, indicating that it has a fundamental importance for eukaryotic cellular redox metabolism. In contrast, the external NADH DHs in plants are products of a recent expansion, mirroring the expansion of the alternative oxidase family.
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| 12. |
- Heiser, Volker, et al.
(författare)
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Antisense repression of the mitochondrial nadh-binding subunit of complex I in transgenic potato plants affects male fertility
- 1997
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Ingår i: Plant Science. - 0168-9452. ; 127:1, s. 61-69
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Tidskriftsartikel (refereegranskat)abstract
- Mitochondrial respiratory chain complex I is a large multi-subunit enzyme composed of both organellar and nuclear encoded proteins. To investigate the role of the nuclear encoded components, expression of the gene for the 55 kDa NADH-binding subunit of complex I was disturbed by antisense repression in transgenic potato plants. The antisense construct driven by the CaMV 35S promoter decreases the steady-state mRNA levels of transcripts for the 55 kDa subunit to 33% of the wild type levels. Quantities of the 55 kDa protein in mitochondrial protein extracts are lowered to about 50% in these plants. Transgenic plants show normal vegetative growth and tuber formation, but pollen maturation is found to be disturbed. The reduced male fertility of the transgenic 55 kDa antisense plants may be caused by an insufficient mitochondrial respiratory chain, impaired by the decreased expression of the NADH-binding component of mitochondrial complex I.
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| 13. |
- Kwao, Stephen, et al.
(författare)
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Effect of guard cells electroporation on drying kinetics and aroma compounds of Genovese basil (Ocimum basilicum L.) leaves
- 2016
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Ingår i: Innovative Food Science and Emerging Technologies. - : Elsevier BV. - 1466-8564. ; 38, s. 15-23
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Tidskriftsartikel (refereegranskat)abstract
- In this study the effect of the application of pulsed electric fields as pre-treatment before air drying of basil leaves at 50 °C was investigated. The parameters of the electric treatment were designed in such a way that they either (i) electroporated the tissue reversibly (tissue remains viable) and without electroporating the guard cells in the stomata complex (65 pulses of 600 V/cm, 120 μs pulse width, 500 μs between pulses), (ii) electroporated the tissue reversibly causing the guard cells to irreversibly open the stomata (65 pulses of 600 V/cm, 150 μs pulse width, 760 μs between pulses), or (iii) irreversibly electroporated the tissue leading to cell death (65 pulses of 1500 V/cm, 150 μs pulse width, 760 μs between pulses). Results demonstrate that dehydration of basil leaves at 50 °C can be aided by the application of pulsed electric fields (PEF). If the applied PEF conditions are such that stomata are irreversibly opened while the rest of the tissue remains viable, the drying process is faster and the product keeps a better colour, is richer in aroma compounds and has better rehydration capacity than the untreated control. Irreversible tissue damage provoked by high intensity PEF drastically decreased the drying time but the measured quality characteristics of the dried leaves were inferior compared to those of the dried product when the stomatal function of the fresh leaf was selectively targeted. Industrial relevance This paper addresses the ever-increasing global demand from consumers for high-quality foods, reporting a novel methodology which improves the quality of dried aromatic herbs using pulsed electric fields.
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| 14. |
- Møller, Ian M., et al.
(författare)
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Isolation of Mitochondria
- 2015
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Ingår i: Plant Physiology and Development 6e Companion Website.
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Bokkapitel (refereegranskat)
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| 15. |
- Møller, Ian Max, et al.
(författare)
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Matrix Redox Physiology Governs the Regulation of Plant Mitochondrial Metabolism through Posttranslational Protein Modifications
- 2020
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Ingår i: The Plant cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 32:3, s. 573-594
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Forskningsöversikt (refereegranskat)abstract
- Mitochondria function as hubs of plant metabolism. Oxidative phosphorylation produces ATP, but it is also a central high-capacity electron sink required by many metabolic pathways that must be flexibly coordinated and integrated. Here, we review the crucial roles of redox-associated posttranslational protein modifications (PTMs) in mitochondrial metabolic regulation. We discuss several major concepts. First, the major redox couples in the mitochondrial matrix (NAD, NADP, thioredoxin, glutathione, and ascorbate) are in kinetic steady state rather than thermodynamic equilibrium. Second, targeted proteomics have produced long lists of proteins potentially regulated by Cys oxidation/thioredoxin, Met-SO formation, phosphorylation, or Lys acetylation, but we currently only understand the functional importance of a few of these PTMs. Some site modifications may represent molecular noise caused by spurious reactions. Third, different PTMs on the same protein or on different proteins in the same metabolic pathway can interact to fine-tune metabolic regulation. Fourth, PTMs take part in the repair of stress-induced damage (e.g., by reducing Met and Cys oxidation products) as well as adjusting metabolic functions in response to environmental variation, such as changes in light irradiance or oxygen availability. Finally, PTMs form a multidimensional regulatory system that provides the speed and flexibility needed for mitochondrial coordination far beyond that provided by changes in nuclear gene expression alone.
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| 16. |
- Møller, Ian M., et al.
(författare)
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NAD(P)H-ubiquinone oxidoreductases in plant mitochondria
- 1993
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Ingår i: Journal of Bioenergetics and Biomembranes. - 0145-479X. ; 25:4, s. 377-384
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Tidskriftsartikel (refereegranskat)abstract
- Plant (and fungal) mitochondria contain multiple NAD(P)H dehydrogenases in the inner membrane all of which are connected to the respiratory chain via ubiquinone. On the outer surface, facing the intermembrane space and the cytoplasm, NADH and NADPH are oxidized by what is probably a single low-molecular-weight, nonproton-pumping, unspecific rotenone-insensitive NAD(P)H dehydrogenase. Exogenous NADH oxidation is completely dependent on the presence of free Ca2+ with a K0.5 of about 1 μM. On the inner surface facing the matrix there are two dehydrogenases: (1) the proton-pumping rotenone-sensitive multisubunit Complex I with properties similar to those of Complex I in mammalian and fungal mitochondria. (2) a rotenone-insensitive NAD(P)H dehydrogenase with equal activity with NADH and NADPH and no proton-pumping activity. The NADPH-oxidizing activity of this enzyme is completely dependent on Ca2+ with a K0.5 of 3 μM. The enzyme consists of a single subunit of 26 kDa and has a native size of 76 kDa, which means that it may form a trimer.
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| 17. |
- Møller, Ian Max, et al.
(författare)
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Plant mitochondria – past, present and future
- 2021
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Ingår i: Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 108:4, s. 912-959
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Tidskriftsartikel (refereegranskat)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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| 18. |
- Møller, Ian M., et al.
(författare)
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The role of NADP in the mitochondrial matrix
- 1998
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Ingår i: Trends in Plant Science. - 1360-1385. ; 3:1, s. 21-27
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Tidskriftsartikel (refereegranskat)abstract
- Many diverse metabolic processes are coupled to the turnover of the coenzyme NADP in the matrix of plant mitochondria. NADPH can be produced via the NADP-specific isocitrate dehydrogenase as well as via enzymes like NAD-malic enzyme, NAD-malate dehydrogenase and Δ1-pyrroline-5-carboxylate dehydrogenase. Although not NADP-specific, the latter enzymes can all catalyse the reduction of NADP+ at appreciable rates. The NADPH produced can be used in folate metabolism, by glutathione reductase for protection against oxidative damage, and by thioredoxin reductase in the (putative) regulation of metabolic pathways via thiol-group reduction. It can also be oxidized by the respiratory chain via a Ca2+-dependent NADPH dehydrogenase - this is a potential way of regulating the NADP reduction level in the matrix and thus, indirectly, the other processes. It is now possible to present an integrated picture of NADP turnover inside the mitochondrion.
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| 19. |
- Møller, Ian M., et al.
(författare)
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Ubiquinone-1 induces external deamino-NADH oxidation in potato tuber mitochondria
- 1996
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Ingår i: Plant Physiology. - 0032-0889. ; 112:1, s. 75-78
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Tidskriftsartikel (refereegranskat)abstract
- The addition of ubiquinone-1 (UQ-1) induced Ca2+-independent oxidation of deamino-NADH and NADH by intact potato (Solanum tuberosum L. cv Bintje) tuber mitochondria. The induced oxidation was coupled to the generation of a membrane potential. Measurements of NAD+-malate dehydrogenase activity indicated that the permeability of the inner mitochondrial membrane to NADH and deamino-NADH was not altered by the addition of UQ-1. We conclude that UQ-1-induced external deamino-NADH oxidation is due to a change in specificity of the external rotenone-insensitive NADH dehydrogenase. The addition of UQ-1 also induced rotenone-insensitive oxidation of deamino-NADH by inside-out submitochondrial particles, but whether this was due to a change in the specificity of the internal rotenone-insensitive NAD(P)H dehydrogenase or to a bypass in complex I could not be determined.
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| 20. |
- Panarese, Valentina, et al.
(författare)
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Vacuum impregnation modulates the metabolic activity of spinach leaves
- 2014
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Ingår i: Innovative Food Science & Emerging Technologies. - : Elsevier BV. - 1466-8564. ; 26, s. 286-293
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Tidskriftsartikel (refereegranskat)abstract
- In this study calorimetric measurements provided evidence of a drastic increase of spinach leaf gross metabolism as a consequence of vacuum impregnation (VI) at a minimum pressure of 150 mbar with trehalose and sucrose isotonic solutions. When applying VI extracellular air is replaced by the impregnation solution, potentially limiting tissue respiration to any remaining air volume in the tissue. However the observation that impregnated leaves showed photosynthetic activity suggests that not all air was exhausted during VI. Hence impregnation appears to reach a maximum with remaining gas filled compartments. Metabolic inhibitors impregnated together with sugars showed that the short-term metabolic response, causing the drastic increase of gross metabolism upon VI, depends on mitochondrial oxygen consuming pathways. The metabolic effect following mannitol impregnation was comparable with water impregnation, suggesting that the strong metabolic effect reported here is only seen for molecules that can be metabolized and provide energy to the cells. Industrial relevance: Vacuum impregnation is used to incorporate additives in fruit and vegetable tissues, such as anti-browning agents, microbial preservatives or cryoprotectants. As a promising technology in the food industry, deeper insights on the metabolic consequences of vacuum impregnation are required to define and control the shelf-life of the processed fruits and vegetables. (C) 2014 Elsevier Ltd. All rights reserved.
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| 21. |
- Patterson, Kurt, et al.
(författare)
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Nitrate-regulated glutaredoxins control Arabidopsis thaliana primary root growth.
- 2016
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 1532-2548 .- 0032-0889. ; , s. 989-999
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen is an essential soil nutrient for plants, and lack of nitrogen commonly limits plant growth. Soil nitrogen is typically available to plants in two inorganic forms: nitrate and ammonium. To better understand how nitrate and ammonium differentially affect plant metabolism and development, we performed transcriptional profiling of the shoots of ammonium-supplied and nitrate-supplied Arabidopsis thaliana plants. Seven genes encoding class III glutaredoxins were found to be strongly and specifically induced by nitrate. RNA silencing of four of these glutaredoxin genes (AtGRXS3/4/5/8) resulted in plants with increased primary root length (~25% longer than wild-type) and decreased sensitivity to nitrate-mediated inhibition of primary root growth. Increased primary root growth is also a well-characterized phenotype of many cytokinin-deficient plant lines. We determined that nitrate induction of glutaredoxin gene expression was dependent upon cytokinin signaling and that cytokinins could activate glutaredoxin gene expression independent of plant nitrate status. In addition, crosses between "long-root" cytokinin-deficient plants and "long-root" glutaredoxin-silenced plants generated hybrids that displayed no further increase in primary root length (i.e. epistasis). Collectively, these findings suggest that AtGRXS3/4/5/8 operate downstream of cytokinins in a signal transduction pathway that negatively regulates plant primary root growth in response to nitrate. This pathway could allow Arabidopsis to actively discriminate between different nitrogen sources in the soil, with the preferred nitrogen source, nitrate, acting to suppress primary root growth (vertical dimension) in concert with its well-characterized stimulatory effect on lateral root growth (horizontal dimension).
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| 22. |
- Petersen, Gitte, et al.
(författare)
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Genes from oxidative phosphorylation complexes II-V and two dual-function subunits of complex I are transcribed in Viscum album despite absence of the entire mitochondrial holo-complex I
- 2022
-
Ingår i: Mitochondrion. - : Elsevier BV. - 1567-7249 .- 1872-8278. ; 62, s. 1-12
-
Tidskriftsartikel (refereegranskat)abstract
- Mistletoes (Viscum) and close relatives are unique among flowering plants in having a drastically altered electron transport chain. Lack of complex I genes has previously been reported for the mitochondrial genome, and here we report an almost complete absence of nuclear-encoded complex I genes in the transcriptome of Viscum album. Compared to Arabidopsis with approximately 40 nuclear complex I genes, we recover only transcripts of two dual-function genes: gamma carbonic anhydrase and L-galactono-1,4-lactone dehydrogenase. The complement of genes belonging to complexes II–V of the oxidative phosphorylation pathway appears to be in accordance with other vascular plants. Additionally, transcripts encoding alternative NAD(P)H dehydrogenases and alternative oxidase were found. Despite sequence divergence, structural modeling suggests that the encoded proteins are structurally conserved. Complex I loss is a special feature in Viscum species and relatives, as all other parasitic flowering plants investigated to date seem to have a complete OXPHOS system. Hence, Viscum offers a unique system for specifically investigating molecular consequences of complex I absence, such as the role of complex I subunits involved in secondary functions.
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| 23. |
- Petit, Patrice X., et al.
(författare)
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Properties of submitochondrial particles from plant mitochondria : generation, surface characteristics and NAD(P)H oxidation
- 1991
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Ingår i: Plant Science. - 0168-9452 .- 1873-2259. ; 78:2, s. 177-183
-
Tidskriftsartikel (refereegranskat)abstract
- Purified mitochondria isolated from potato (Solanum tuberosum L. cv. Bintje) tuber, Jerusalem artichoke (Helianthus tuberosu L.) tuber and rat liver were disrupted at different pH and different EDTA and MgCl2 concentrations either by French Press treatment or by sonication. The submitochondrial particles (SMP) were isolated by differential centrifugation and polarity estimated by the latency of cytochrome c oxidase (CCO) activity. The SMP were 5-9% inside-out depending on the conditions, and the disruption method was more important than the composition of the disruption medium in determining the polarity. At pH 6 and 7 and high-salt conditions sonication yielded SMP of the same polarity (82-91% inside-out) whereas French Press treatment in a low-salt buffer + EDTA gave more inside-out SMP at pH 6 than at pH 7. The inside out vesicles were able to build up a membrane potential in the presence of respiratory substrates (as tested with the anionic dye, oxonol VI) whereas no membrane potantial could be detected with the right-side-out vesicles (as tested with cationic dyes, and optical dye, safranine O, and a fluorescent dye, rhodamine 123) under similar conditions. Binding of Concanavalin A indicated that both the inner and outer surface of the inner membrane have exposed glycoproteins and/or glycolipids. Both right-side-out and inside-out SMP oxidized NADH, NADPH and succinate with good rates but there were clear differences in both donor and acceptor specificity between the outer and inner surface of the inner mitochondrial membrane. NADH oxidation by inside-out SMP was Ca2+-independent and rotenone-inhibited whereas NADPH oxidation by the inside-out SMP was Ca2+-dependent and relatively unaffected by rotenone.
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| 24. |
- Podgórska, Anna, et al.
(författare)
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Efficient Photosynthetic Functioning of Arabidopsis thaliana Through Electron Dissipation in Chloroplasts and Electron Export to Mitochondria Under Ammonium Nutrition
- 2020
-
Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 11
-
Tidskriftsartikel (refereegranskat)abstract
- An improvement in photosynthetic rate promotes the growth of crop plants. The sink-regulation of photosynthesis is crucial in optimizing nitrogen fixation and integrating it with carbon balance. Studies on these processes are essential in understanding growth inhibition in plants with ammonium ((Formula presented.)) syndrome. Hence, we sought to investigate the effects of using nitrogen sources with different states of reduction (during assimilation of (Formula presented.) versus (Formula presented.)) on the photosynthetic performance of Arabidopsis thaliana. Our results demonstrated that photosynthetic functioning during long-term (Formula presented.) nutrition was not disturbed and that no indication of photoinhibition of PSII was detected, revealing the robustness of the photosynthetic apparatus during stressful conditions. Based on our findings, we propose multiple strategies to sustain photosynthetic activity during limited reductant utilization for (Formula presented.) assimilation. One mechanism to prevent chloroplast electron transport chain overreduction during (Formula presented.) nutrition is for cyclic electron flow together with plastid terminal oxidase activity. Moreover, redox state in chloroplasts was optimized by a dedicated type II NAD(P)H dehydrogenase. In order to reduce the amount of energy that reaches the photosynthetic reaction centers and to facilitate photosynthetic protection during (Formula presented.) nutrition, non-photochemical quenching (NPQ) and ample xanthophyll cycle pigments efficiently dissipate excess excitation. Additionally, high redox load may be dissipated in other metabolic reaA ctions outside of chloroplasts due to the direct export of nucleotides through the malate/oxaloacetate valve. Mitochondrial alternative pathways can downstream support the overreduction of chloroplasts. This mechanism correlated with the improved growth of A. thaliana with the overexpression of the alternative oxidase 1a (AOX1a) during (Formula presented.) nutrition. Most remarkably, our findings demonstrated the capacity of chloroplasts to tolerate (Formula presented.) syndrome instead of providing redox poise to the cells.
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| 25. |
- Podgorska, Anna, et al.
(författare)
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In comparison with nitrate nutrition, ammonium nutrition increases growth of the frostbite1 Arabidopsis mutant
- 2015
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Ingår i: Plant, Cell and Environment. - : Wiley. - 0140-7791 .- 1365-3040. ; 38:1, s. 224-237
-
Tidskriftsartikel (refereegranskat)abstract
- Ammonium nutrition inhibits the growth of many plant species, including Arabidopsis thaliana. The toxicity of ammonium is associated with changes in the cellular redox state. The cellular oxidant/antioxidant balance is controlled by mitochondrial electron transport chain. In this study, we analysed the redox metabolism of frostbite1 (fro1) plants, which lack mitochondrial respiratory chain complex I. Surprisingly, the growth of fro1 plants increased under ammonium nutrition. Ammonium nutrition increased the reduction level of pyridine nucleotides in the leaves of wild-type plants, but not in the leaves of fro1 mutant plants. The observed higher activities of type II NADH dehydrogenases and cytochrome c oxidase in the mitochondrial electron transport chain may improve the energy metabolism of fro1 plants grown on ammonium. Additionally, the observed changes in reactive oxygen species (ROS) metabolism in the apoplast may be important for determining the growth of fro1 under ammonium nutrition. Moreover, bioinformatic analyses showed that the gene expression changes in fro1 plants significantly overlap with the changes previously observed in plants with a modified apoplastic pH. Overall, the results suggest a pronounced connection between the mitochondrial redox system and the apoplastic pH and ROS levels, which may modify cell wall plasticity and influence growth. In this paper, we analysed the redox metabolism of frostbite1 (fro1) plants lacking Complex I under ammonium nutrition. We showed that, although ammonium leads to stress in wild type plants, ammonium does not cause reductive stress in fro1 plants. Our experimental and bioinformatic analyses indicated that mtETC dysfunction strongly influences apoplastic reactive oxygen species content and pH, and suggested that the faster growth of fro1 plants under ammonium nutrition probably results from modification of the cell wall.
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| 26. |
- Podgórska, Anna, et al.
(författare)
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Respiratory burst oxidases and apoplastic peroxidases facilitate ammonium syndrome development in Arabidopsis
- 2021
-
Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472. ; 181
-
Tidskriftsartikel (refereegranskat)abstract
- Ammonium-nitrogen (NH4+) nutrition is linked to metabolic over-reduction for plants. The characteristic symptom of sole NH4+ nutrition is growth suppression, signifying this condition as the ammonium syndrome. In the present study, we investigated the mechanism of perception of high NH4+ conditions in Arabidopsis thaliana plants by examining apoplastic reactive oxygen species (ROS) metabolism. Major enzyme activity and a special pattern of expression of NADPH-dependent respiratory burst oxidases (RBOH) was found in Arabidopsis individuals cultured under NH4+ as the sole nitrogen source. This oxidative burst is independent of RBOHD/F expression and does not activate typical intracellular signalling pathways. In addition, elevated superoxide dismutase and apoplastic secretory peroxidase activities contributed to hydrogen peroxide (H2O2) accumulation in plants exposed to NH4+ nutrition. Consequently, higher H2O2 contents were determined in the extracellular space and were localised cytochemically. H2O2 is a substrate for cell wall cross-linking peroxidases, which showed enhanced activity in the presence of NH4+. Increase of cell wall polymerisation, could in turn inhibit cell elongation and slow down growth, as observed under NH4+ toxicity.
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| 27. |
- Podgórska, Anna, et al.
(författare)
-
Short-term ammonium supply induces cellular defence to prevent oxidative stress in Arabidopsis leaves
- 2017
-
Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317. ; 160:1, s. 65-83
-
Tidskriftsartikel (refereegranskat)abstract
- Plants can assimilate nitrogen from soil pools of both ammonium and nitrate, and the relative levels of these two nitrogen sources are highly variable in soil. Long-term ammonium nutrition is known to cause damage to Arabidopsis that has been linked to mitochondrial oxidative stress. Using hydroponic cultures, we analysed the consequences of rapid shifts between nitrate and ammonium nutrition. This did not induce growth retardation, showing that Arabidopsis can compensate for the changes in redox metabolism associated with the variations in nitrogen redox status. During the first 3h of ammonium treatment, we observed distinct transient shifts in reactive oxygen species (ROS), low-mass antioxidants, ROS-scavenging enzymes, and mitochondrial alternative electron transport pathways, indicating rapid but temporally separated changes in chloroplastic, mitochondrial and cytosolic ROS metabolism. The fast induction of antioxidant defences significantly lowered intracellular H2O2 levels, and thus protected Arabidopsis leaves from oxidative stress. On the other hand elevated extracellular ROS production in response to ammonium supply may be involved in signalling. The response pattern displays an intricate plasticity of Arabidopsis redox metabolism to minimise stress in responses to nutrient changes.
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| 28. |
- Podgórska, Anna, et al.
(författare)
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Suppression of external NADPH dehydrogenase—NDB1 in arabidopsis thaliana confers improved tolerance to ammonium toxicity via efficient Glutathione/Redox metabolism
- 2018
-
Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 19:5
-
Tidskriftsartikel (refereegranskat)abstract
- Environmental stresses, including ammonium (NH4 +) nourishment, can damage key mitochondrial components through the production of surplus reactive oxygen species (ROS) in the mitochondrial electron transport chain. However, alternative electron pathways are significant for efficient reductant dissipation in mitochondria during ammonium nutrition. The aim of this study was to define the role of external NADPH-dehydrogenase (NDB1) during oxidative metabolism of NH4 +-fed plants. Most plant species grown with NH4 + as the sole nitrogen source experience a condition known as “ammonium toxicity syndrome”. Surprisingly, transgenic Arabidopsis thaliana plants suppressing NDB1 were more resistant to NH4 + treatment. The NDB1 knock-down line was characterized by milder oxidative stress symptoms in plant tissues when supplied with NH4 +. Mitochondrial ROS accumulation, in particular, was attenuated in the NDB1 knock-down plants during NH4 + treatment. Enhanced antioxidant defense, primarily concerning the glutathione pool, may prevent ROS accumulation in NH4 +-grown NDB1-suppressing plants. We found that induction of glutathione peroxidase-like enzymes and peroxiredoxins in the NDB1-surpressing line contributed to lower ammonium-toxicity stress. The major conclusion of this study was that NDB1 suppression in plants confers tolerance to changes in redox homeostasis that occur in response to prolonged ammonium nutrition, causing cross tolerance among plants.
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| 29. |
- Rasmusson, Allan G., et al.
(författare)
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Component of the alternative oxidase localized to the matrix surface of the inner membrane of plant mitochondria
- 1990
-
Ingår i: FEBS Letters. - 0014-5793. ; 259:2, s. 311-314
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Tidskriftsartikel (refereegranskat)abstract
- In mitoplasts from Arum maculatum spadices, succinate dehydrogenase (EC 1.3.99.1) and the alternative, cyanide-resistant oxidase activity (measured as m-chlorobenzhydroxamic acid-sensitive duroquinol oxidation) was unaffected by treatment with trypsin. In contrast, when 85% inside-out submitochondrial particles were treated with trypsin the alternative oxidase activity was inhibited by about 50% and succinate dehydrogenase activity by about 40%. Thus, a trypsin-sensitive component of the alternative pathway is located on the inner surface of the inner mitochondrial membrane. After trypsin treatment of the inside-out submitochondrial particles the inhibited alternative oxidase activity was partly restored by including 0.7 M citrate in the assay medium. This indicates that trypsin does not destroy the active site but merely causes a conformational change in the enzyme, thereby lowering its activity.
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| 30. |
- Rasmusson, Allan G., et al.
(författare)
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Homologues of yeast and bacterial rotenone-insensitive NADH dehydrogenases in higher eukaryotes : Two enzymes are present in potato mitochondria
- 1999
-
Ingår i: Plant Journal. - 0960-7412. ; 20:1, s. 79-87
-
Tidskriftsartikel (refereegranskat)abstract
- Two different cDNAs, homologous to genes for rotenone-insensitive NADH dehydrogenases of bacteria and yeast, were isolated from potato. The encoded proteins, called NDA and NDB, have calculated molecular masses of 55 and 65kDa, respectively. The N-terminal parts show similarity to mitochondrial targeting peptides and the polypeptides are in vitro imported into potato mitochondria. Import processing to a smaller polypeptide is seen for the NDA but not the NDB protein. After import, NDA is intramitochondrially sorted to the matrix side of the inner membrane, whereas NDB becomes exposed to the intermembrane space. Imported proteins are associated to membranes upon digitonin permeabilization. On expression in Escherichia coli, NDB is released from the bacterial membrane in the absence of divalent cations whereas detergents are necessary for solubilization of NDA. Both deduced amino-acid sequences contain the dual motifs for nucleotide binding with the characteristics of the core criteria, similar to the bacterial homologues. Unique among NADH dehydrogenases, the NDB amino-acid sequence contains a nonconserved insert, which is similar to EF-hand motifs for calcium binding. Phylogenetic analyses group the rotenone-insensitive NADH dehydrogenases largely by species, but suggest ancient gene duplications.
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| 31. |
- Rasmusson, Allan G., et al.
(författare)
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Integrity Assessment of Isolated Plant Mitochondria
- 2022
-
Ingår i: Methods in Molecular Biology. - New York, NY : Springer US. - 1940-6029 .- 1064-3745. ; 2363, s. 51-62
-
Bokkapitel (refereegranskat)abstract
- The integrity of isolated mitochondria can be estimated functionally using enzymatic activities or the permeability of mitochondrial membranes to molecules of different sizes. Thus, the permeability of the outer membrane to the protein cytochrome c, the permeability of the inner membrane to protons, and the permeability of the inner membrane to NAD+, NADH and organic acids using soluble matrix dehydrogenases as markers have all been used. These assays all have limitations to how the data can be converted into a measure of integrity, are differently sensitive to artifacts and require widely variable amounts of material. Therefore, each method has a restricted utility for estimating integrity, depending on the type of mitochondria analysed. Here, we review the advantages and disadvantages of different integrity assays and present protocols for integrity assays that require relatively small amounts of mitochondria. They are based on the permeability of the outer membrane to cytochrome c, and the inner membrane to protons or NAD(H). The latter has the advantage of utilizing a membrane-bound activity (complex I) and the pore-forming peptide alamethicin to gain access to the matrix space. These methods together provide a toolbox for the determination of functionality and quality of isolated mitochondria.
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| 32. |
- Rasmusson, Allan G., et al.
(författare)
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Mitochondrial NAD(P)H oxidation pathways and nitrate/ammonium redox balancing in plants
- 2020
-
Ingår i: Mitochondrion (Amsterdam. Print). - : ELSEVIER SCI LTD. - 1567-7249 .- 1872-8278. ; 53, s. 158-165
-
Forskningsöversikt (refereegranskat)abstract
- Plant mitochondrial oxidative phosphorylation is characterised by alternative electron transport pathways with different energetic efficiencies, allowing turnover of cellular redox compounds like NAD(P)H. These electron transport chain pathways are profoundly affected by soil nitrogen availability, most commonly as oxidized nitrate (NO3-) and/or reduced ammonium (NH4+). The bioenergetic strategies involved in assimilating different N sources can alter redox homeostasis and antioxidant systems in different cellular compartments, including the mitochondria and the cell wall. Conversely, changes in mitochondrial redox systems can affect plant responses to N. This review explores the integration between N assimilation, mitochondrial redox metabolism, and apoplast metabolism.
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| 33. |
- Rasmusson, Allan G., et al.
(författare)
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Molecular characterisation of the 76 kDa iron-sulphur protein subunit of potato mitochondrial complex I
- 1998
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Ingår i: Plant and Cell Physiology. - 0032-0781. ; 39:4, s. 373-381
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Tidskriftsartikel (refereegranskat)abstract
- Genes encoding subunits of complex I (EC 1.6.5.3) of the mitochondrial respiratory chain vary in their locations between the mitochondrial and nuclear genomes in different organisms, whereas genes for a homologous multisubunit complex in chloroplasts have to date only been found on the plastid genome. In potato (Solanum tuberosum L.), the gene coding for the mitochondrial 76 kDa iron-sulphur protein is identified in the nuclear genome. The gene is transcribed into polyadenylated mRNA which is most abundant in flowers, and more frequent in tubers than in leaves. The amino acid sequence is well conserved relative to the nuclear-encoded 75 kDa and 78 kDa subunits of Bos taurus and Neurospora crassa, respectively, and to the Paracoccus denitrificans homologue, most prominently in the region presumed to carry the iron-sulphur clusters. Polyclonal antibodies directed against the 78 kDa complex I subunit of N. crassa recognise the 76 kDa polypeptide in potato mitochondrial complex I, and additionally a polypeptide of 75 kDa in solubilised stroma thylakoids from spinach chloroplasts. The 32 amino acid residues long presequence of the potato mitochondrial 76 kDa complex I subunit targets the precursor polypeptide into isolated potato mitochondria but not into isolated chloroplasts. These results suggest that chloroplast stroma thylakoids contain a protein similar in size and antigenicity to, but genetically distinct from, the mitochondrial subunit.
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| 34. |
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| 35. |
- Rasmusson, Allan G., et al.
(författare)
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NADP-utilizing enzymes in the matrix of plant mitochondria
- 1990
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 94:3, s. 1012-1018
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Tidskriftsartikel (refereegranskat)abstract
- Purified potato tuber (Solanum tuberosum L. cv Bintje) mitochondria contain soluble, highly latent NAD+- and NADP+-isocitrate dehydrogenases, NAD+- and NADP+-malate dehydrogenases, as well as an NADPH-specific glutathione reductase (160, 25, 7200, 160, and 16 nanomoles NAD(P)H per minute and milligram protein, respectively). The two isocitrate dehydrogenase activities, but not the two malate dehydrogenase activities, could be separated by ammonium sulfate precipitation. Thus, the NADP+-isocitrate dehydrogenase activity is due to a separate matrix enzyme, whereas the NADP+-malate dehydrogenase activity is probably due to unspecificity of the NAD+-malate dehydrogenase. NADP+-specific isocitrate dehydrogenase had much lower Kms for NADP+ and isocitrate (5.1 and 10.7 micromolar, respectively) than the NAD+-specific enzyme (101 micromolar for NAD+ and 184 micromolar for isocitrate). A broad activity optimum at pH 7.4 to 9.0 was found for the NADP+-specific isocitrate dehydrogenase whereas the NAD+-specific enzyme had a sharp optimum at pH 7.8. Externally added NADP+ stimulated both isocitrate and malate oxidation by intact mitochondria under conditions where external NADPH oxidation was inhibited. This shows that (a) NADP+ is taken up by the mitochondria across the inner membrane and into the matrix, and (b) NADP+-reducing activities of malate dehydrogenase and the NADP+-specific isocitrate dehydrogenase in the matrix can contribute to electron transport in intact plant mitochondria. The physiological relevance of mitochondrial NADP(H) and soluble NADP(H)-consuming enzymes is discussed in relation to other known mitochondrial NADP(H)-utilizing enzymes.
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| 36. |
- Rasmusson, Allan G., et al.
(författare)
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Physiological, biochemical and molecular aspects of mitochondrial complex I in plants
- 1998
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Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - 0005-2728. ; 1364:2, s. 101-111
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Tidskriftsartikel (refereegranskat)abstract
- Respiratory complex I of plant mitochondria has to date been investigated with respect to physiological function, biochemical properties and molecular structure. In the respiratory chain complex I is the major entry gate for low potential electrons from matrix NADH, reducing ubiquinone and utilizing the released energy to pump protons across the inner membrane. Plant complex I is active against a background of several other NAD(P)H dehydrogenases, which do not contribute in proton pumping, but permit and establish several different routes of shuttling electrons from NAD(P)H to ubiquinone. Identification of the corresponding molecular structures, that is the proteins and genes of the different NADH dehydrogenases, will allow more detailed studies of this interactive regulatory network in plant mitochondria. Present knowledge of the structure of complex I and the respective mitochondrial and nuclear genes encoding various subunits of this complex in plants is summarized here. Copyright (C) 1998 Elsevier Science B.V.
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| 37. |
- Rasmusson, Allan G., et al.
(författare)
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Purification of a rotenone-insensitive NAD(P)H dehydrogenase from the inner surface of the inner membrane of red beetroot mitochondria
- 1993
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Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - 0005-2728. ; 1141:1, s. 107-110
-
Tidskriftsartikel (refereegranskat)abstract
- The soluble fraction of disrupted red beetroot mitochondria was resolved by anion-exchange chromatography. Three NADH-oxidising activities were found, including one duroquinone reductase oxidising both NADH and NADPH. This NAD(P)H-duroquinone reductase, which we assign as the internal rotenone-insensitive NAD(P)H dehydrogenase, was further purified by affinity chromatography into a 26 kDa polypeptide.
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| 38. |
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| 39. |
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| 40. |
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| 41. |
- Ren, Zhenjing, et al.
(författare)
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Tetratricopeptide-containing SMALL KERNEL 11 is essential for the assembly of cytochrome c oxidase in maize mitochondria
- 2023
-
Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 192:1, s. 170-187
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Tidskriftsartikel (refereegranskat)abstract
- Assembly of the functional complexes of the mitochondrial respiratory chain requires sophisticated and efficient regulatory mechanisms. In plants, the subunit composition and assembly factors involved in the biogenesis of cytochrome c oxidase (complex IV) are substantially less defined than in mammals and yeast. In this study, we cloned maize (Zea mays) Small kernel 11 (Smk11) via map-based cloning. Smk11 encodes a mitochondria-localized tetratricopeptide repeat protein. Disruption of Smk11 severely affected the assembly and activity of mitochondrial complex IV, leading to delayed plant growth and seed development. Protein interactions studies revealed that SMK11 might interact with four putative complex IV assembly factors, Inner membrane peptidase 1A (ZmIMP1A), MYB domain protein 3R3 (ZmMYB3R-3), cytochrome c oxidase 23 (ZmCOX23), and mitochondrial ferredoxin 1 (ZmMFDX1), among which ZmMFDX1 might interact with subunits ZmCOX6a and ZmCOX-X1; ZmMYB3R-3 might also interact with ZmCOX6a. The mutation of SMK11 perturbed the normal assembly of these subunits, leading to the inactivation of complex IV. The results of this study revealed that SMK11 serves as an accessory assembly factor required for the normal assembly of subunits into complex IV, which will accelerate the elucidation of the assembly of complex IV in plant mitochondria.
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| 42. |
- Rollano-Peñaloza, Oscar M., et al.
(författare)
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The Disease Progression and Molecular Defense Response in Chenopodium Quinoa Infected with Peronospora Variabilis, the Causal Agent of Quinoa Downy Mildew
- 2022
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Ingår i: Plants. - : MDPI AG. - 2223-7747. ; 11:21
-
Tidskriftsartikel (refereegranskat)abstract
- Downy mildew disease, caused by the biotrophic oomycete Peronospora variabilis, is the largest threat to the cultivation of quinoa (Chenopodium quinoa Willd.) in the Andean highlands, and occurs worldwide. However, so far, no molecular study of the quinoa–Peronospora interaction has been reported. Here, we developed tools to study downy mildew disease in quinoa at the gene expression level. P. variabilis was isolated and maintained, allowing the study of downy mildew disease progression in two quinoa cultivars under controlled conditions. Quinoa gene expression changes induced by P. variabilis were analyzed by qRT-PCR, for quinoa homologues of A. thaliana pathogen-associated genes. Overall, we observed a slower disease progression and higher tolerance in the quinoa cultivar Kurmi than in the cultivar Maniqueña Real. The quinoa orthologs of putative defense genes such as the catalase CqCAT2 and the endochitinase CqEP3 showed no changes in gene expression. In contrast, quinoa orthologs of other defense response genes such as the transcription factor CqWRKY33 and the chaperone CqHSP90 were significantly induced in plants infected with P. variabilis. These genes could be used as defense response markers to select quinoa cultivars that are more tolerant to P. variabilis infection.
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| 43. |
- Rollano Penaloza, Oscar Miguel, et al.
(författare)
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Trichoderma harzianum T-22 and BOL-12QD inhibits lateral root development of Chenopodium quinoa in axenic co-culture
- 2018
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Ingår i: Cogent Biology. - : Informa UK Limited. - 2331-2025. ; 4:1530493
-
Tidskriftsartikel (refereegranskat)abstract
- To investigate the symbiotic interaction of Trichoderma harzianum Rifaion Chenopodium quinoa Willd. in isolation, we studied axenic co-culture of the T. harzianum isolates T-22 and BOL-12QD and the C. quinoa cultivars Kurmi andManiqueña real. Neither T-22 nor BOL-12QD affected seedling growth during two days of co-culture in the early growth phase of rapid primary root extension.However, after longer axenic co-culture, T-22 and BOL-12 were found to significantly inhibit the overall growth of C. quinoa cv. Kurmi and Real, affecting also vitality parameters as seen for chlorophyll and betalains. Lateral root development was strongly inhibited in all plant−fungal combinations, leaving stunted lateral roots. These results suggest that T. harzianum has a general capacity to inhibit the growth of C. quinoa plants with a main effect on the lateral root development.
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| 44. |
- Schmidt, John, et al.
(författare)
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Substrate and plant genotype strongly influence the growth and gene expression response to trichoderma afroharzianum T22 in sugar beet
- 2020
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Ingår i: Plants. - : MDPI AG. - 2223-7747. ; 9:8, s. 1-14
-
Tidskriftsartikel (refereegranskat)abstract
- Many strains of Trichoderma fungi have beneficial effects on plant growth and pathogen control, but little is known about the importance of plant genotype, nor the underlying mechanisms. We aimed to determine the effect of sugar beet genotypic variation on Trichoderma biostimulation. The effect of Trichoderma afroharzianum T22 on sugar beet inbred genotypes were investigated in soil and on sterile agar medium regarding plant growth, and by quantitative reverse transcriptase-linked polymerase chain reaction (qRT-PCR) analysis for gene expression. In soil, T22 application induced up to 30% increase or decrease in biomass, depending on plant genotype. In contrast, T22 treatment of sterile-grown seedlings resulted in a general decrease in fresh weight and root length across all sugar beet genotypes. Root colonization of T22 did not vary between the sugar beet genotypes. Sand-and sterile-grown roots were investigated by qRT-PCR for expression of marker genes for pathogen response pathways. Genotype-dependent effects of T22 on, especially, the jasmonic acid/ethylene expression marker PR3 were observed, and the effects were further dependent on the growth system used. Thus, both growth substrate and sugar beet genotype strongly affect the outcome of inoculation with T. afroharzianum T22.
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| 45. |
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| 46. |
- Thamkaew, Grant, et al.
(författare)
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Reversible Electroporation and Post-Electroporation Resting of Thai Basil Leaves Prior to Convective and Vacuum Drying
- 2022
-
Ingår i: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 12:5
-
Tidskriftsartikel (refereegranskat)abstract
- Pretreatment by reversible electroporation followed by resting (storage under saturated moisture at 21 ± 2 °C) was evaluated for modification of the properties of dried and rehydrated Thai basil leaves. The treated leaves were dried by convection at 40 °C or in a vacuum at room temperature. The results showed that vacuum drying provoked more cell damage and tissue collapse than convective air drying at a moisture ratio (MR) of 0.2 and 0.1. Under this level of MR, the pulsed electric field (PEF) and resting pretreatment exerts a protective effect of the tissue for both drying methods. However, under complete dehydration (water activity, aw = 0.05) damage seems to be similar for both drying methods despite the PEF pretreatment. Remarkably, reversible electroporation followed by resting resulted in higher trichome preservation. At MR of 0.05, the area of trichomes on the surface of convective-dried, PEF-rested and fresh samples were not statistically different at 2267 ± 89 µm2 and 2218 ± 65 µm2, respectively, showing that this pretreatment still exerts a protective effect on trichomes when complete dehydration is achieved.
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| 47. |
- Thamkaew, Grant, et al.
(författare)
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The effect of reversible permeabilization and post-electroporation resting on the survival of Thai basil (O. Basilicum cv. thyrsiflora) leaves during drying
- 2021
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1567-5394. ; 142
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Tidskriftsartikel (refereegranskat)abstract
- Horticultural crops have a low tolerance to dehydration. In this paper, we show that the reversible electroporation (200 monopolar, rectangular pulses of 50 µs pulse duration, 760 µs between pulses and nominal field strength of 650 V/cm) of Thai basil leaves followed by 24 h resting before hot air drying at 40 °C enhanced the survivability of the tissues at certain levels of dehydration (moisture ratio = 0.2 and 0.1). However, this increased survival was rather limited. Through measurements of metabolic heat production during resting, rehydration kinetics, respiration and photosynthesis of the rehydrated leaves, we show that resting after the application of a reversible pulse-electric field (PEF) may allow a phase of hardening that has a protective effect on the cells, thus decreasing damage during the subsequent drying phase. Increased preservation of cell vitality would be associated with a more turgid and fresh-like rehydrated product, as cells would have the capacity to retain the rehydration water.
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| 48. |
- Tran, Huy Cuong, et al.
(författare)
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Purification of Leaf Mitochondria from Arabidopsis thaliana Using Percoll Density Gradients
- 2022
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Ingår i: Plant Mitochondria : Methods and Protocols - Methods and Protocols. - New York, NY : Springer US. - 1064-3745 .- 1940-6029. - 9781071616536 - 9781071616529 ; 2363, s. 1-12
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Bokkapitel (refereegranskat)abstract
- The study of plant mitochondria often requires isolation of mitochondria from plant tissues in intact and functional form. Here, we describe an effective procedure of mitochondrial isolation from leaf tissues and whole seedlings of the model dicot species Arabidopsis thaliana by using differential centrifugation and continuous Percoll density gradients.
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| 49. |
- Vajda, Vivi, et al.
(författare)
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Confirmation that Antevsia zeilleri microsporangiate organs associated with latest Triassic Lepidopteris ottonis (Peltaspermales) leaves produced Cycadopites-Monosulcites-Chasmatosporites- and Ricciisporites-type monosulcate pollen
- 2024
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182. ; 640
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Tidskriftsartikel (refereegranskat)abstract
- In reply to the commentary by N. Zavialova (Rev. Palaeobot. Palynol. 322, 105,065), we provide additional data and illustrations reaffirming that the Triassic peltaspermalean ‘seed-fern’ Lepidopteris ottonis produced the abnormal pollen Ricciisporites tuberculatus, solving a long-standing mystery in palaeobotany. The microsporangiate organ Antevsia zeilleri linked to Lepidopteris ottonis foliage produced polymorphic pollen ranging from smooth-walled monads that would normally be attributed to Cycadopites, Monosulcites and Chasmatosporites to strongly ornamented Ricciisporites tuberculatus-type grains occurring in permanent tetrads. Multiple microscopy techniques reveal that these in situ and associated dispersed pollen are represented by a complete continuum in exine ornamentation. Moreover, scanning electron microscopy and ultrastructural analyses reveal variation in the wall architecture between these pollen types that can be explained by aberrant developmental pathways within the pollen sac. Finally, the occurrence of Ricciisporites tuberculatus in at least 15 Antevsia zeilleri sacs and their co-occurrence with smooth-walled monosulcate pollen in an additional five pollen sacs, in the absence of any other palynomorphs, plant detritus or mineral matter, demonstrates their co-production by the parent plant and excludes the possibility of taphonomic mixing.
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| 50. |
- Vajda, Vivi, et al.
(författare)
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The ‘seed-fern’ Lepidopteris mass-produced the abnormal pollen Ricciisporites during the end-Triassic biotic crisis
- 2023
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 627
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Tidskriftsartikel (refereegranskat)abstract
- The end-Triassic mass extinction (ETE; ~201.6 million years ago) led to dramatic changes in terrestrial eco systems including the extinction of several seed-plant groups. Among the most intriguing features in the vege tation signal is the dominance of the peculiar pollen, Ricciisporites tuberculatus Lundblad, across large areas of the Northern Hemisphere immediately prior to and during the ETE. The parent plant of this pollen has remained unknown for 70 years. Here, we demonstrate that the ‘seed-fern’ Lepidopteris ottonis (Go¨ppert) Schimper (Pel taspermales) produced R. tuberculatus in permanent tetrads. We show that R. tuberculatus is a large, abnormal form of the small smooth-walled monosulcate pollen traditionally associated with L. ottonis, which disappeared at the ETE, when volcanism induced cold-spells followed by global warming. We argue that the production of aberrant R. tuberculatus resulted from ecological pressure in stressed environments that favoured asexual reproduction in peltasperms. The expansion of dry environments led to the dominance of drought-tolerant plants in the Early Jurassic of northern middle latitudes.
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