scholarly journals Pyruvate metabolism in castor-bean mitochondria

1986 ◽  
Vol 239 (2) ◽  
pp. 355-361 ◽  
Author(s):  
M A Brailsford ◽  
A G Thompson ◽  
N Kaderbhai ◽  
R B Beechey
Keyword(s):  
Electron Transport ◽  
Castor Bean ◽  
Silicone Oil ◽  
Ricinus Communis ◽  
Mitochondrial Protein ◽  
Respiratory Control ◽  
O2 Uptake ◽  
Salicylhydroxamic Acid ◽  
Oxidation Rates ◽  
Pyruvate Oxidation

We report the isolation of mitochondria from the endosperm of castor beans (Ricinus communis). These mitochondria oxidized succinate, external NADH, malate and pyruvate with respiratory-control and ADP/O ratios consistent with those found previously with mitochondria from other plant sources. The mitochondria exhibited considerable sensitivity to the electron-transport-chain inhibitors antimycin A and cyanide when oxidizing succinate and external NADH. Pyruvate-dependent O2 uptake was relatively insensitive to these inhibitors, although the residual O2 uptake could be inhibited by salicylhydroxamic acid. We conclude that a cyanide-insensitive alternative terminal oxidase is functional in these mitochondria. However, electrons from the succinate dehydrogenase or external NADH dehydrogenase seem to have no access to this pathway. There is little interconnection between the salicylhydroxamic acid-sensitive and cyanide-sensitive pathways of electron transport. alpha-Cyanocinnamate and its analogues, compound UK5099 [alpha-cyano-beta-(1-phenylindol-3-yl)acrylate] and alpha-cyano-4-hydroxycinnamate, were all found to be potent non-competitive inhibitors of pyruvate oxidation in castor-bean mitochondria. The accumulation of pyruvate by castor-bean mitochondria was determined by using a silicone-oil-centrifugation technique. The accumulation was shown to observe Michaelis-Menten kinetics, with a Km for pyruvate of 0.10 mM and a Vmax. of 0.95 nmol/min per mg of mitochondrial protein. However, the observed rates of pyruvate accumulation were insufficient to account for the pyruvate oxidation rates found in the oxygen-electrode studies. We were able to demonstrate that this is due to the immediate export of the accumulated radiolabel in the form of malate and citrate. Compound UK5099 inhibited the accumulation of [2-14C]pyruvate by castor-bean mitochondria at concentrations similar to those required to inhibit pyruvate oxidation.

Biochemical and ultrastructural studies on flight muscle mitochondria from the blowfly Calliphora erythrocephala following treatment by chloramphenicol and ethidium bromide

1980 ◽  
Vol 41 (1) ◽  
pp. 291-306
Author(s):  
B. Ashour ◽  
M. Tribe ◽  
S. Danks ◽  
P. Whittaker
Keyword(s):  
Protein Synthesis ◽  
Ethidium Bromide ◽  
Mitochondrial Protein ◽  
Respiratory Control ◽  
Mitochondrial Morphology ◽  
Difference Spectra ◽  
Calliphora Erythrocephala ◽  
Oxidation Rates ◽  
Ultrastructural Studies ◽  
High Doses

Adult blowflies were injected during the first day after eclosion with various concentrations of the drugs chloramphenicol and ethidium bromide. Previous experiments had shown that these drugs inhibit mitochondrial protein synthesis and at high doses increase mortality. Mitochondria isolated from blowflies 24 h after drug injection revealed a considerable decrease in oxidation rates when pyruvate plus proline were used as substrates. There was also a reduction up to 50% in the respiratory control ratios obtained, though there was little change in the measurable ADP: O ratios. This loss in activity was commensurate with the finding that both drugs block the rapid increase in protein synthesis (expressed as mitochondrial protein content) during the period of observation. Examination of the cytochrome difference spectra 24 h after treatment again showed a decline in all major cytochrome peaks with increasing concentration of both drugs. Examination of mitochondrial morphology in situ using electron microscopy revealed degenerative changes 24 h after treatment with high doses of both drugs. In particular, irregular alignment of cristae and extensive vacuolation were observed within the mitochondria. The extent of decreased biochemical activity and morphological damage to mitochondria was clearly dependent on the concentration of drugs administered and such changes may be attributed primarily to a loss of certain polypeptide subunits coded for by mitochondrial DNA and synthesized on mitochondrial ribosomes.

Mitochondrial protein expression in tomato fruit during on-vine ripening and cold storage

2002 ◽  
Vol 29 (7) ◽  
pp. 827 ◽  
Author(s):  
Ruth C. Holtzapffel ◽  
Patrick M. Finnegan ◽  
A. Harvey Millar ◽  
Murray R. Badger ◽  
David A. Day
Keyword(s):  
Electron Transport ◽  
Alternative Oxidase ◽  
Uncoupling Protein ◽  
Tricarboxylic Acid Cycle ◽  
Tomato Fruit ◽  
Expression Patterns ◽  
Mitochondrial Protein ◽  
Respiratory Control ◽  
Isolated Mitochondria ◽  
Plant Uncoupling Protein

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.

scholarly journals Properties of mitochondria isolated from cyanide-sensitive and cyanide-stimulated cultures of Acanthamoeba castellanii

1978 ◽  
Vol 174 (1) ◽  
pp. 203-211 ◽  
Author(s):  
Steven W. Edwards ◽  
David Lloyd
Keyword(s):  
Electron Transport ◽  
Respiratory Control ◽  
Acanthamoeba Castellanii ◽  
Type A ◽  
Antimycin A ◽  
Type B ◽  
Transport Pathway ◽  
Salicylhydroxamic Acid ◽  
Stages Of Growth ◽  
Electron Transport Pathway

1. Mitochondria isolated from cultures of Acanthamoeba castellanii exhibit respiratory control and oxidize α-oxoglutarate, succinate and NADH with ADP:O ratios of about 2.4, 1.4 and 1.25 respectively. 2. Mitochondria from cultures of which the respiration was stimulated up to 50% by 1mm-cyanide (type-A mitochondria) and from cyanide-sensitive cultures (type-B mitochondria) had similar respiratory-control ratios and ADP:O ratios. 3. State-3 rates of respiration were generally more cyanide-sensitive than State-4 rates, and the respiration of type-A mitochondria was more cyanide-resistant than that of type-B mitochondria. 4. Salicylhydroxamic acid alone had little effect on respiratory activities of either type of mitochondria, but when added together with cyanide, irrespective of the order of addition, inhibition was almost complete. 5. Oxidation of externally added NADH by type-A mitochondria was mainly via an oxidase with a low affinity for oxygen (Km[unk]15μm), which was largely cyanide-sensitive and partially antimycin A-sensitive; this electron-transport pathway was inhibited by ADP. 6. Cyanide-insensitive but salicylhydroxamic acid-sensitive respiration was stimulated by AMP and ADP, and by ATP after incubation in the presence of MgCl2. 7. Addition of rotenone to mitochondria oxidizing α-oxoglutarate lowered the ADP:O ratios by about one-third and rendered inhibition by cyanide more complete. 8. The results suggest that mitochondria of A. castellanii possess branched pathways of electron transport which terminate in three separate oxidases; the proportions of electron fluxes via these pathways vary at different stages of growth.

On the origin of oil droplets in maturing castor bean seeds,Ricinus communis

Lipids ◽  
1971 ◽  
Vol 6 (11) ◽  
pp. 851-854 ◽  
Author(s):  
J. L. Harwood ◽  
Ann Sodja ◽  
P. K. Stumpf ◽  
A. R. Spurr
Keyword(s):  
Castor Bean ◽  
Ricinus Communis ◽  
Oil Droplets ◽  
Origin Of Oil

First report of association of Cucumber mosaic virus with blister and leaf distortion of castor bean (Ricinus communis) in India

2010 ◽  
Vol 38 (3) ◽  
pp. 283-289 ◽  
Author(s):  
Shri Krishna Raj ◽  
Sunil Kumar Snehi ◽  
Karmveer Kumar Gautam ◽  
Mohammad Sajid Khan
Keyword(s):  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Castor Bean ◽  
Ricinus Communis ◽  
First Report ◽  
Leaf Distortion

scholarly journals Bulked segregant analysis reveals candidate genes responsible for dwarf formation in woody oilseed crop castor bean

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zaiqing Wang ◽  
Anmin Yu ◽  
Fei Li ◽  
Wei Xu ◽  
Bing Han ◽  
...  
Keyword(s):  
Candidate Genes ◽  
Castor Bean ◽  
Woody Plants ◽  
Molecular Mechanisms ◽  
Ricinus Communis ◽  
Bulked Segregant Analysis ◽  
Oilseed Crop ◽  
Yeast Transformation ◽  
Dwarf Phenotype ◽  
Genetic Breeding

AbstractPlant dwarfism is a desirable agronomic trait in non-timber trees, but little is known about the physiological and molecular mechanism underlying dwarfism in woody plants. Castor bean (Ricinus communis) is a typical woody oilseed crop. We performed cytological observations within xylem, phloem and cambia tissues, revealing that divergent cell growth in all tissues might play a role in the dwarf phenotype in cultivated castor bean. Based on bulked segregant analyses for a F2 population generated from the crossing of a tall and a dwarf accession, we identified two QTLs associated with plant height, covering 325 candidate genes. One of these, Rc5NG4-1 encoding a putative IAA transport protein localized in the tonoplast was functionally characterized. A non-synonymous SNP (altering the amino acid sequence from Y to C at position 218) differentiated the tall and dwarf plants and we confirmed, through heterologous yeast transformation, that the IAA uptake capacities of Rc5NG4-1Y and Rc5NG4-1C were significantly different. This study provides insights into the physiological and molecular mechanisms of dwarfing in woody non-timber economically important plants, with potential to aid in the genetic breeding of castor bean and other related crops.

Dual Mutations Reveal Interactions Between Components of Oxidative Phosphorylation in Kluyveromyces lactis

Genetics ◽  
2001 ◽  
Vol 159 (3) ◽  
pp. 929-938
Author(s):  
G D Clark-Walker ◽  
X J Chen
Keyword(s):  
Electron Transport ◽  
Oxidative Phosphorylation ◽  
Atp Synthase ◽  
Kluyveromyces Lactis ◽  
Mitochondrial Protein ◽  
Proton Pumping ◽  
Nuclear Genes ◽  
Suppressor Activity ◽  
Inner Membrane ◽  
Atp Production

Abstract Loss of mtDNA or mitochondrial protein synthesis cannot be tolerated by wild-type Kluyveromyces lactis. The mitochondrial function responsible for ρ0-lethality has been identified by disruption of nuclear genes encoding electron transport and F0-ATP synthase components of oxidative phosphorylation. Sporulation of diploid strains heterozygous for disruptions in genes for the two components of oxidative phosphorylation results in the formation of nonviable spores inferred to contain both disruptions. Lethality of spores is thought to result from absence of a transmembrane potential, ΔΨ, across the mitochondrial inner membrane due to lack of proton pumping by the electron transport chain or reversal of F1F0-ATP synthase. Synergistic lethality, caused by disruption of nuclear genes, or ρ0-lethality can be suppressed by the atp2.1 mutation in the β-subunit of F1-ATPase. Suppression is viewed as occurring by an increased hydrolysis of ATP by mutant F1, allowing sufficient electrogenic exchange by the translocase of ADP in the matrix for ATP in the cytosol to maintain ΔΨ. In addition, lethality of haploid strains with a disruption of AAC encoding the ADP/ATP translocase can be suppressed by atp2.1. In this case suppression is considered to occur by mutant F1 acting in the forward direction to partially uncouple ATP production, thereby stimulating respiration and relieving detrimental hyperpolarization of the inner membrane. Participation of the ADP/ATP translocase in suppression of ρ0-lethality is supported by the observation that disruption of AAC abolishes suppressor activity of atp2.1.

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