80 results on '"Laties GG"'
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2. Plasmalemma and Tonoplast Influxes of Potassium in Barley Roots, and Interpretation of the Absorption Isotherm at High Concentrations
- Author
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Robinson, JB and Laties, GG
- Abstract
Estimates of plasmalemma influx and steady-state vacuolar influx of potassium in low-salt barley roots have been obtained in the concentration range 10-80 mM by the use of controlled loading and washing times. Both fluxes are reduced by preloading the tissue in solutions containing potassium. When the experimental temperature is increased from 20 to 30°C, an apparent increase in the steady-state vacuolar influx occurs; separation of this flux from the apparent plasmalemma influx is not possible. The data support the hypothesis that the kinetics of potassium exchange in barley root tissue may be confounded by both loading time and temperature, and thus interpretation of the influx isotherm in the high concentration range is difficult. Where experiments are carried out at 20-25°C the steady- state vacuolar influx is measured unless closely defined experimental conditions obtain. At higher temperatures the plasmalemma influx may be measured.
- Published
- 1975
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3. The Use of Short-Term and Quasi-Steady Influx in Estimating Plasmalemma and Tonoplast Influx in Barley Root Cells at Various External and Internal Chloride Concentrations
- Author
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Cram, WJ, primary and Laties, GG, additional
- Published
- 1971
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4. Ethylene and Wound-Induced Gene Expression in the Preclimacteric Phase of Ripening Avocado Fruit and Mesocarp Discs.
- Author
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Starrett DA and Laties GG
- Abstract
Whereas intact postharvest avocado (Persea americana Mill.) fruit may take 1 or more weeks to ripen, ripening is hastened by pulsing fruit for 24 h with ethylene or propylene and is initiated promptly by cutting slices, or discs, of mesocarp tissue. Because the preclimacteric lag period constitutes the extended and variable component of the ripening syndrome, we postulated that selective gene expression during the lag period leads to the triggering of the climacteric. Accordingly, we sought to identify genes that are expressed gradually in the course of the lag period in intact fruit, are turned on sooner in response to a pulse, and are induced promptly in response to wounding (i.e. slicing). To this end, a mixed cDNA library was constructed from mRNA from untreated fruit, pulsed fruit, and aged slices, and the library was screened for genes induced by wounding or by pulsing and/or wounding. The time course of induction of genes encoding selected clones was established by probing northern blots of mRNA from tissues variously treated over a period of time. Four previously identified ripening-associated genes encoding cellulase, polygalacturonase (PG), cytochrome P-450 oxidase (P-450), and ethylene-forming enzyme (EFE, or 1-aminocyclopropane-1-carboxylic acid synthase), respectively, were studied in the same way. Whereas cellulase, PG, and EFE were ruled out as having a role in the initiation of the climacteric, the time course of P-450 induction, as well as the response of same to pulsing and wounding met the criteria[mdash]together with several clones from the mixed library[mdash]for a gene potentially involved in preclimacteric events leading to the onset of the climacteric. Further, it was established that the continuous presence of ethylene is required for persisting induction, and it is suggested that in selected cases wounding may exert a synergistic effect on ethylene action.
- Published
- 1993
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5. Ripening-related polygalacturonase cDNA from avocado.
- Author
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Kutsunai SY, Lin AC, Percival FW, Laties GG, and Christoffersen RE
- Subjects
- Amino Acid Sequence, DNA, Complementary metabolism, Databases, Factual, Genes, Plant, Molecular Sequence Data, Open Reading Frames, Vegetables genetics, Vegetables physiology, Polygalacturonase biosynthesis, Vegetables enzymology
- Published
- 1993
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6. Ethylene-Mediated Posttranscriptional Regulation in Ripening Avocado (Persea americana) Mesocarp Discs.
- Author
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Buse EL and Laties GG
- Abstract
Discs of avocado (Persea americana) fruit (15 x 3 mm thick) kept in a stream of moist air ripen within 72 h. Following cutting, a modest evolution of wound ethylene that dissipates in 24 h is followed by a burst of autocatalytic ethylene production associated with a respiratory climacteric, much as in the intact fruit. Aminoethoxyvinylglycine (AVG), an inhibitor of ethylene synthesis, and 2,5-norbornadiene (NBD) and Ag+, inhibitors of ethylene action, inhibit disc ripening, as does 2,4-dichlorophenoxyacetic acid (2,4-D), a synthetic auxin. On the other hand, none of the foregoing agents except Ag+, at concentrations that delay or prevent ripening, suppress the induction of four ripening-related genes encoding cellulase, polygalacturonase (PG), cytochrome P-450 oxidase (P-450), and ethylene-forming enzyme (EFE, or 1-aminopropane-1-carboxylic acid oxidase), respectively. Whereas Ag+ fully inhibits the production of cellulase and PG mRNAs, it has little effect on the induction of EFE and P-450 mRNAs. Cellulase and PG enzyme activities are absent in extracts of discs treated with AVG, NBD, or 2,4-D, as are antigenically detectable cellulase and PG proteins. The strong appearance of ripening-related mRNAs in discs inhibited from softening by ethylene antagonists suggests posttranscriptional control by ethylene. Similarly, inhibition of ripening by 2,4-D without suppression of mRNA induction suggests translational control. Whether ethylene inhibits transcription or postttranscriptional events or both depends on its concentration.
- Published
- 1993
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7. Involvement of wound and climacteric ethylene in ripening avocado discs.
- Author
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Starrett DA and Laties GG
- Abstract
Avocado (Persea americana Mill. cv Hass) discs (3 mm thick) ripened in approximately 72 hours when maintained in a flow of moist air and resembled ripe fruit in texture and taste. Ethylene evolution by discs of early and midseason fruit was characterized by two distinct components, viz. wound ethylene, peaking at approximately 18 hours, and climacteric ethylene, rising to a peak at approximately 72 hours. A commensurate respiratory stimulation accompanied each ethylene peak. Aminoethoxyvinyl glycine (AVG) given consecutively, at once and at 24 hours following disc preparation, prevented wound and climacteric respiration peaks, virtually all ethylene production, and ripening. When AVG was administered for the first 24 hours only, respiratory stimulation and softening (ripening) were retarded by at least a day. When AVG was added solely after the first 24 hours, ripening proceeded as in untreated discs, although climacteric ethylene and respiration were diminished. Propylene given together with AVG led to ripening under all circumstances. 2,5-Norbornadiene given continuously stimulated wound ethylene production, and it inhibited climacteric ethylene evolution, the augmentation of ethylene-forming enzyme activity normally associated with climacteric ethylene, and ripening. 2,5-Norbornadiene given at 24 hours fully inhibited ripening. When intact fruit were pulsed with ethylene for 24 hours before discs were prepared therefrom, the respiration rate, ethylene-forming enzyme activity buildup, and rate of ethylene production were all subsequently enhanced. The evidence suggests that ethylene is involved in all phases of disc ripening. In this view, wound ethylene in discs accelerates events that normally take place over an extended period throughout the lag phase in intact fruit, and climacteric ethylene serves the same ripening function in discs and intact fruit alike.
- Published
- 1991
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8. The Effect of Ethylene and Propylene Pulses on Respiration, Ripening Advancement, Ethylene-Forming Enzyme, and 1-Aminocyclopropane-1-carboxylic Acid Synthase Activity in Avocado Fruit.
- Author
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Starrett DA and Laties GG
- Abstract
When early-season avocado fruit (Persea americana Mill. cv Hass) were treated with ethylene or propylene for 24 hours immediately on picking, the time to the onset of the respiratory climacteric, i.e. the lag period, remained unchanged compared with that in untreated fruit. When fruit were pulsed 24 hours after picking, on the other hand, the lag period was shortened. In both cases, however, a 24 hour ethylene or propylene pulse induced a transient increase in respiration, called the pulse-peak, unaccompanied by ethylene production (IL Eaks [1980] Am Soc Hortic Sci 105: 744-747). The pulse also caused a sharp rise in ethylene-forming enzyme activity in both cases, without any increase in the low level of 1-aminocyclopropane-1-carboxylic acid synthase activity. Thus, the shortening of the lag period by an ethylene pulse is not due to an effect of ethylene on either of the two key enzymes in ethylene biosynthesis. A comparison of two-dimensional polyacrylamide gel electrophoresis polypeptide profiles of in vitro translation products of poly(A(+)) mRNA from control and ethylene-pulsed fruit showed both up- and down-regulation in response to ethylene pulsing of a number of genes expressed during the ripening syndrome. It is proposed that the pulse-peak or its underlying events reflect an intrinsic element in the ripening process that in late-season or continuously ethylene-treated fruit may be subsumed in the overall climacteric response. A computerized system that allows continuous readout of multiple samples has established that the continued presentation of exogeneous ethylene or propylene to preclimacteric fruit elicits a dual respiration response comprising the merged pulse-peak and climacteric peak in series. The sequential removal of cores from a single fruit has proven an unsatisfactory sampling procedure inasmuch as coring induces wound ethylene, evokes a positive respiration response, and advances ripening.
- Published
- 1991
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9. Comparative effects of ethylene and cyanide on respiration, polysome prevalence, and gene expression in carrot roots.
- Author
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Tucker ML and Laties GG
- Abstract
Treatment of carrot roots (Daucus carota L.) with 10 microliters per liter ethylene in O(2) evokes a three- to four-fold increase in polysome prevalence and associated poly(A)(+) RNA. The increase in polysome prevalence is attended by a similar change in CO(2) evolution. The increase in polysomal poly(A)(+) mRNA constitutes primarily a generic increase in constitutive mRNAs as assayed by in vitro translation. However, changes in the relative abundance of several in vitro translatable ethylene specific mRNAs do occur.Cyanide, at concentrations which inhibit cytochrome oxidase, initiates a respiratory rise very similar in kinetics and magnitude to that evoked by ethylene. Moreover, the combined treatment with cyanide and ethylene evokes a respiratory response resembling that caused by ethylene or cyanide alone. Nevertheless, cyanide, in the presence of ethylene, significantly inhibits the increase in polysome prevalence and new gene expression associated with ethylene treatment of carrot roots. Separation of in vitro translation products by one-dimensional and two-dimensional gel electrophoresis shows that several new in vitro translation products appear in cyanide-treated carrots different from those evoked by ethylene. Engagement of the less energy efficient alternative electron transport path by cyanide may be responsible for inhibition of the normal ethylene associated increase in polysome prevalence and new gene expression. The implications of these results on regulation of respiratory metabolism are discussed and compared with the results for similar experiments with avocado fruit (Tucker and Laties 1984 Plant Physiol 74: 307-315) in which cyanide does not inhibit an ethylene educed increase in polysome prevalence and change in gene expression.
- Published
- 1984
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10. Similarities between the Actions of Ethylene and Cyanide in Initiating the Climacteric and Ripening of Avocados.
- Author
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Solomos T and Laties GG
- Abstract
A continuous exposure of intact avocados (Persea americana) to 400 mul/l of cyanide results in a rapid increase in the rate of respiration, followed by a rise in ethylene production, and eventual ripening. The pattern of changes in the glycolytic intermediates glucose 6-phosphate, fructose diphosphate, 3-phosphoglyceric acid, and phosphoenolpyruvate during the rapid rise in respiration in both ethylene and cyanide-treated fruits is similar to that found in fruits made anaerobic where a 2.3- to 3-fold increase in the rate of glycolysis is observed. It is suggested that both during the climacteric and in response to cyanide, glycolysis is enhanced. It is proposed that cyanide implements the diversion of electrons to the cyanide-resistant electron path through structural alterations which are independent of the simultaneous inhibition of cytochrome oxidase.
- Published
- 1974
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11. Relative Contribution of Cytochrome-mediated and Cyanide-resistant Electron Transport in Fresh and Aged Potato Slices.
- Author
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Theologis A and Laties GG
- Abstract
The respiration of fresh potato (Solanum tuberosum, var. Russet Burbank) slices is predominantly cyanide-sensitive whether in the presence or absence of uncoupler. By contrast, the wound-induced respiration which develops in thin slices with aging is cyanide-resistant, and in the presence of cyanide, sensitive to chlorobenzhydroxamic acid, a selective inhibitor of the cyanide-resistant respiration. Titration of the alternate path in coupled slices with chlorobenzhydroxamic acid, in the presence and absence of cyanide, shows that the contribution of the cyanide-resistant pathway to the wound-induced respiration is zero. Similar titrations with uncoupled slices reveal that the alternate path is engaged and utilized extensively.The maximal capacity of the cytochrome path (V(cyt)) has been estimated in fresh and aged slices in the presence of the uncoupler carbonyl-cyanide m-chlorophenyl hydrazone. It has been found that V(cyt) of aged slices is but 30 to 40% higher than that of fresh slices. The results suggest that the bulk of the wound-induced respiration is mediated through the cytochrome pathway which exists in fresh slices in suppressed form, and which is fully expressed by slice aging. The engagement of the alternate path by uncouplers in aged slices is attributed to an increase in substrate mobilization, with the result that the electron transport capacity of the cytochrome chain is exceeded.
- Published
- 1978
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12. Trypsin-induced ATPase Activity in Potato Mitochondria.
- Author
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Jung DW and Laties GG
- Abstract
Potato mitochondria (Solanum tuberosum var. Russet Burbank), which readily phosphorylate ADP in oxidative phosphorylation, show low levels of ATPase activity which is stimulated neither by Mg(2+), 2,4-dinitrophenol, incubation with respiratory substrates, nor disruption by sonication or treatment with Triton X-100, individually or in concert. Treatment of disrupted potato mitochondria with trypsin stimulates Mg(2+)-dependent, oligomycin-sensitive ATPase activity 10- to 15-fold, suggesting the presence of an ATPase inhibitor protein. Trypsin-induced ATPase activity was unaffected by uncoupler. Oligomycin-sensitive ATPase activity decreases as exposure to trypsin is increased. Incubation at alkaline pH or heating at 60 C for 2 minutes also activates ATPase of sonicated potato mitochondria. Disruption of cauliflower (Brassica oleracea), red sweet potato (Ipomoea batatas), and carrot (Daucus carota) mitochondria increases ATPase activity, which is further enhanced by treatment with trypsin. The significance of the tight association of the inhibitor protein and ATPase in potato mitochondria is not clear.
- Published
- 1976
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13. Isolation and Characterization of Inner Membrane-Associated and Matrix NAD-Specific Isocitrate Dehydrogenase in Potato Mitochondria.
- Author
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Tezuka T and Laties GG
- Abstract
The isotherm for isocitrate oxidation by potato (Solanum tuberosum L. var. Russet Burbank) mitochondria in the presence of exogenous NAD is characterized by a hyperbolic phase at isocitrate concentrations below 3 millimolar, and a sigmoid, or positively cooperative phase from approximately 3 to 30 millimolar. The two forms of isocitrate dehydrogenase were separated and characterized following the sonication of mitochondria in 15% glycerol in the absence of buffer, followed by fractionation in a density step gradient to yield inner membrane and matrix components. The membrane-associated isocitrate dehydrogenase was found to have a Hill, or cooperativity, number of 1, while the Hill number of the matrix enzyme was 2.5. Upon digitonin extraction the cooperativity number of the membrane enzyme rose to 3.5. The isocitrate K(m) for the membrane enzyme was calculated to be approximately 5.9 x 10(-4) molar, while the S(0.5) for the matrix was 6.9 x 10(-4) molar. The NAD K(m) for both enzymes was 150 micromolar. Whereas the membrane enzyme proved indifferent to adenine nucleotides, the matrix enzyme was arguably inhibited by AMP and ADP, and inhibited some 25% by 5 millimolar ATP. Both enzymes were negatively responsive to the mole fraction of NADH, the membrane enzyme being 50% inhibited at a mole fraction of 0.26, and the matrix enzyme by a mole fraction of 0.32. The suggestion is offered that the enzymes in question constitute two forms of a single enzyme, one peripherally associated with the inner membrane, and one soluble in the matrix. It is proposed that a degree of regulation may be achieved by the apportionment of the enzyme between the bound and free forms.
- Published
- 1983
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14. Alternative path mediated chloride absorption in cyanide-resistant tissues.
- Author
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Theologis A and Laties GG
- Abstract
The ability of two cyanide-resistant tissues-aged potato slices and fresh preclimacteric banana slices-to take up chloride in the presence of cyanide has been established. Extensive inhibition of chloride uptake by cyanide and chlorbenzhydroxamate together indicates that chloride absorption in the presence of cyanide is supported by respiration mediated by the alternative path. The partial inhibition of respiration-dependent chloride uptake by chlorbenzhydroxamate alone is independent of its effect on the alternative oxidase, and points to inhibition of the transport process per se.
- Published
- 1981
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15. Gene expression during fruit ripening in avocado.
- Author
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Christoffersen RE, Warm E, and Laties GG
- Abstract
The poly(A) (+)RNA populations from avocado fruit (Persea americana Mill cv. Hass) at four stages of ripening were isolated by two cycles of oligo-dT-cellulose chromatography and examined by invitro translation, using the rabbit reticulocyte lysate system, followed by two-dimensional gel electrophoresis (isoelectric focusing followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis) of the resulting translation products. Three mRNAs increased dramatically with the climacteric rise in respiration and ethylene production. The molecular weights of the corresponding translation products from the ripening-related mRNAs are 80,000, 36,000, and 16,500. These results indicate that ripening may be linked to the expression of specific genes.
- Published
- 1982
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16. Antimycin-insensitive Cytochrome-mediated Respiration in Fresh and Aged Potato Slices.
- Author
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Theologis A and Laties GG
- Abstract
The effect of antimycin A on the respiration of fresh potato (Solanum tuberosum var. Russet Burbank) slices has been determined in the presence and absence of m-chlorobenzhydroxamic acid (CLAM). Two antimycin-binding sites are indicated. At low concentrations antimycin alone inhibits respiration only slightly. When CLAM and low antimycin are added together, respiration is sharply inhibited, as in response to cyanide. High antimycin alone is as inhibitory as cyanide. The branch point to the alternate path is intact in fresh slices, as is the hydroxamate-sensitive component. The full alternate path is inoperative, however, as indicated by the sensitivity to cyanide. The data suggest an alternate path loop which bypasses the high affinity antimycin site and returns electrons to the cytochrome path. Antimycin at high concentrations prevents articulation of the loop with the cytochrome path.The respiration of aged slices is not only markedly resistant to antimycin at high concentrations, but quite insensitive to CLAM in the presence of antimycin. A model is proposed which involves parallel paths within complex III of the cytochrome path, with one path bearing the high affinity, and the other the low affinity antimycin site. With slice aging the antimycin affinity of the latter site is even further reduced, providing a relatively antimycin-insensitive bypass to both the high affinity antimycin-sensitive cytochrome path, and the CLAM-sensitive alternate path. The alternate path loop in fresh slices is presumed to feed into the low affinity antimycin-sensitive arm of the cytochrome path.
- Published
- 1978
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17. Ethylene regulation of gene expression in carrots.
- Author
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Christoffersen RE and Laties GG
- Abstract
The respiration of carrot (Daucus carota L.) roots is stimulated by ethylene. Polyribosomes were shown to proliferate concomitantly with the increase in respiration, and the extent of polyribosome augmentation was closely correlated to the amount of respiratory stimulation. In addition to the increase in quantity, ethylene caused a 2-fold increase in the average polyribosome size, suggesting tighter packing of ribosomes on RNA. In vitro translation of carrot polyadenylylated RNA with the rabbit reticulocyte lysate system followed by electrophoresis of the resulting translation products showed that ethylene treatment results in the appearance of new mRNAs.
- Published
- 1982
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18. Inhibition of the Development of Induced Respiration and Cyanide-insensitive Respiration in Potato Tuber Slices by Cerulenin and Dimethylaminoethanol.
- Author
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Waring AJ and Laties GG
- Abstract
The interdependence of the development of wound-induced respiration and membrane-related phospholipid biosynthesis in potato tuber (Solanum tuberosum var. Russet) slices was established by the use of agents which selectively affect lipid and phospholipid synthesis. Cerulenin, a specific inhibitor of de novo fatty acid synthesis, inhibited the ultimate development of wound-induced respiration and of cyanide resistance only when given in the critical first 10 to 12 hours of slice aging. Similarly, when slices were exposed to the choline analogue dimethylaminoethanol within the first 10 hours, the phospholipid composition of the membrane lipids was drastically altered, the wound-induced respiration in a 24-hr period was substantially curtailed, and the development of cyanide insensitivity was sharply inhibited. These observations indicate that time-restricted membrane-related phospholipid synthesis is prerequisite to the development of wound-induced respiration and concurrent cyanide insensitivity.
- Published
- 1977
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19. Differential control of ethylene-induced gene expression and respiration in carrot roots.
- Author
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Nichols SE and Laties GG
- Abstract
Ethylene treatment of carrot roots elicits a developmental program encompassing an increase in respiration rate and changes in gene expression. Both phenomena are potentiated when ethylene is administered in O(2). Our previous studies showed that both respiration and a number of ethylene specific mRNAs increase together in response to ethylene through some 21 hours, whereas thereafter respiration continues to rise, while the level of induced mRNAs drops. Herein we ask whether an experimentally effected drop in the respiration rate within the first 21 hours caused by the withdrawal of ethylene, or substitution of air for O(2) in the continued presence of ethylene, is linked to a drop in the level of ethylene-induced mRNA. Quantitative estimation of two ethylene evoked mRNAs by dot blot hybridization with appropriate cDNA clones has shown that under the specified treatment the induced mRNA levels remain constant while the respiration rate drops, suggesting that gene expression, as reflected in induced mRNA levels, and respiration rate are separately regulated facets of the ethylene response.
- Published
- 1985
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20. Effect of ethylene and carbon dioxide on potato metabolism: stimulation of tuber and mitochondrial respiration, and inducement of the alternative path.
- Author
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Day DA, Arron GP, Christoffersen RE, and Laties GG
- Abstract
The respiration of potato tubers (Solanum tuberosum var. Russet Burbank) which have been kept at room temperature for 10 days is stimulated upon subsequent treatment with C(2)H(4) (10 microliters per liter) and O(2). The respiratory rise reaches a peak in 24 to 30 hours and thereafter declines. Coincident with the rise in tuber respiration is an increase in the respiratory rates of fresh slices and isolated mitochondria. Slices and mitochondria from C(2)H(4)- and O(2)-treated tubers also display substantial resistance to CN, and the resistant respiration is inhibited by hydroxamates.The longer the tubers are stored after harvest, the less effective is C(2)H(4) in causing CN resistance in slices and mitochondria from treated tubers. Addition of 10% CO(2) to the C(2)H(4)-O(2) mixture, however, causes extensive CN resistance to develop, even in slices and mitochondria from old tubers. The results show that C(2)H(4), O(2), and CO(2) act synergistically to induce alternative path development in potatoes.
- Published
- 1978
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21. Membrane Lipid Breakdown in Relation to the Wound-induced and Cyanide-resistant Respiration in Tissue Slices: A COMPARATIVE STUDY.
- Author
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Theologis A and Laties GG
- Abstract
A study of a variety of bulky storage organs and fruits reveals that fresh slices fall into two categories with respect to their sensitivity to CN. Fresh slices in the first class are CN-sensitive, whereas slices of the second class are resistant to, and often stimulated by, CN. In tissue slices which are initially CN-sensitive, cutting initiates a burst of lipolytic activity. In CN-resistant fresh slices, there is no measurable lipid breakdown.Slicing evokes the wound-respiration which is 5- to 10-fold that of the parent organ. Slice aging, in turn, evokes a further 2- to 3-fold respiratory increase, the wound-induced respiration, whether fresh slice respiration is CN-sensitive or -resistant. Estimation of the contribution by the cytochrome and alternative paths shows that the wound respiration in both groups is mediated by the cytochrome path. On the other hand, the wound-induced respiration in the first class is cytochrome path mediated, whereas, in some members of the second group, both pathways are utilized. Uncouplers of oxidative phosphorylation elicit a CN-sensitive increment in fresh slices as great or greater than the wound-induced respiration. Accordingly, de novo synthesis of mitochondria is ruled out as an explanation of the latter.The integrity of endomembranes, perhaps including mitochondrial membranes, is seemingly a prerequisite for the operation of the alternative path, that is, alternative path activity is lost concomitantly with membrane lipid breakdown. The development of the wound-induced respiration is not co-extensive with the development of the CN-resistant path in all tissue slices. The fundamental process of aging appears to involve activation of pre-existing respiratory capacity.Fresh slices from whatever source fail to utilize exogenous (14)C-labeled glucose, whereas aged slices do so readily. A transport lesion is indicated, the healing of which does not depend on the development of the wound-induced respiration but does depend on fatty acid, and presumably membrane lipid, biosynthesis.
- Published
- 1980
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22. Identification of a wound-induced inhibitor of a nuclear factor that binds the carrot extensin gene.
- Author
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Holdsworth MJ and Laties GG
- Abstract
Following wounding of carrot (Daucus carota L.) roots, the activity of a nuclear factor (EGBF-1) that binds a 5'-region of the carrot extensin gene declines to undetectable levels within 48 h. Mixing of nuclear extracts from wounded roots with nuclear extracts from unwounded roots has demonstrated the existence of a wound-induced inhibitor of EGBF-1. Inhibition of EGBF-1 DNA-binding activity by nuclear extracts from wounded roots is shown to be specific for EGBF-1, and to be destroyed by heat treatment. In addition, inhibition is saturable and occurs rapidly. Active EGBF-1 can be reconstituted from its inhibited state by renaturation of proteins from mixed extracts following denaturation by boiling in sodium dodecyl sulfate and 2-mercaptoethanol, and electrophoretic separation, indicating that inhibition is dependent upon the reversible interaction of EGBF-1 with a titratable factor. However, EGBF-1 activity could not be detected in nuclear extracts from wounded roots following denaturation and electrophoretic separation. Inhibitory activity was not detectable in nuclear extracts from roots that had been trated with ethylene. The action of the inhibitor indicates one possible mechanism for the control of EGBF-1 activity in carrot roots following wounding.
- Published
- 1989
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23. Cellulase gene expression in ripening avocado fruit: The accumulation of cellulase mRNA and protein as demonstrated by cDNA hybridization and immunodetection.
- Author
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Christoffersen RE, Tucker ML, and Laties GG
- Abstract
A cDNA library was constructed from poly(A)(+)RNA of ripe avocado fruit. Colony hybridization identified a number of ripening specific clones of which one, pAV5, was shown to be specific for cellulase. Hybrid selection with pAV5 provided a message from ripe fruit that on in vitro translation yielded a polypeptide of 53kD, comigrating with purified avocado cellulase on SDS polyacrylamide gel electrophoresis. The translation product was selectively immunoprecipitated by antiserum to purified avocado cellulase. Immunoblotting of unripe and ripe avocado fruit extracts following SDS-PAGE showed a plentiful immunoreactive polypeptide in ripe fruit, and essentially none in unripe fruit. Hybridization of pAV5 to poly(A)(+)-RNA from unripe and ripe avocado fruit demonstrated that there is at least a 50-fold increase in the cellulase message concentration during ripening. Thus, the expression of cellulase enzyme activity during ripening is regulated by the appearance of mRNA coding for cellulase rather than by either translational or post-translational control mechanisms.
- Published
- 1984
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24. Isolation of mitochondria from plant material.
- Author
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Laties GG
- Subjects
- Calcium, Cell Fractionation methods, Chelating Agents, Edetic Acid, Fatty Acids, Nonesterified analysis, Lipase analysis, Magnesium, Oxygen Consumption, Plants analysis, Plants enzymology, Plants metabolism, Ultracentrifugation, Mitochondria analysis, Mitochondria enzymology, Mitochondria metabolism, Plants ultrastructure
- Published
- 1974
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25. Wound-induced membrane lipid breakdown in potato tuber.
- Author
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Theologis A and Laties GG
- Abstract
Freshly cut slices of potato tuber show an extensive loss of membrane lipid components which may be as great as 35% for phospholipids and 30% for glycolipids, in less than 15 minutes at 3 C. Phosphatidyl-choline, phosphatidyl-ethanolamine and mono- and di-galactosyl diglycerides comprise the bulk of the lipids that are degraded. Concomitantly, there is a pronounced loss of linoleic and linolenic acids. Whereas degradative events elicited by slicing proceed to a depth of at least 10 millimeters from the surface, phospholipid biosynthesis, as well as the development of the wound induced respiration and cyanide resistance on aging, are restricted to the superficial 1 millimeter.
- Published
- 1981
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26. Citrate and succinate uptake by potato mitochondria.
- Author
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Jung DW and Laties GG
- Abstract
The uptake of [(14)C]citrate and [(14)C]succinate was studied in potato mitochondria (Solanum tuberosum var. Russet Burbank) using cellulose pore filtration and was found to occur by the same mechanisms as described for mammalian mitochondria. Potato mitochondria, in the absence of respiration, have a very low capacity for uptake by exchange with endogenous anions, taking up only 2.4 nanomoles citrate and 2.0 nanomoles succinate per milligram protein. Maximum citrate uptake of over 17 nanomoles per milligram protein occurs in the presence of inorganic phosphate, a dicarboxylic acid, and an external energy source (NADH), conditions where net anion accumulation proceeds, mediated by the interlinking of the inorganic phosphate, dicarboxylate, and tricarboxylate carriers. Maximum succinate uptake in the absence of respiratory inhibitors requires only added inorganic phosphate.Compounds which inhibit respiration (antimycin), the exchange carriers (mersalyl and benzylmalonate), or the establishment of the membrane proton motive force (uncouplers) reduce substrate accumulation. A potent inhibitor of the citrate carrier in animal mitochondria, 1,2,3-benzenetricarboxylic acid, does not inhibit citrate uptake in potato mitochondria. Citrate uptake is reduced by concurrent ADP phosphorylation and this reduction is sensitive to oligomycin. The initiation of state 3 after a 3-minute substrate state results in a reduction of the steady-state of citrate uptake by approximately 50%. Accumulation of succinate initially is inhibited by increasing sucrose concentration in the reaction medium from 50 to 400 millimolar.Limited substrate uptake is one of the factors responsible for the often observed depressed initial state 3 respiration rates in many mitochondrial preparations. Since nonlimiting levels of substrate in the matrix cannot be attained by energy-independent exchange, a dependence on respiration for adequate uptake results. Substrate limitation therefore occurs in the matrix for the period of time needed for energy-dependent accumulation of nonlimiting levels.
- Published
- 1979
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27. The mechanism of ethylene and cyanide action in triggering the rise in respiration in potato tubers.
- Author
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Solomos T and Laties GG
- Abstract
Ethylene and cyanide induce a sharp increase in respiration in potato tubers (Solanum tuberosum, var. Russet) attended by changes in the glycolytic intermediates which indicate that both gases enhance glycolysis. The level of sucrose also increases in response to both treatments. The data are taken to indicate that both cyanide and ethylene either activate or affect the link between the conventional electron transport chain and the cyanide-insensitive path. It is further proposed that this activation may well be the primary event leading to the rise in respiration. Ethylene increases the level of adenosine 5'-triphosphate and it is suggested that because of the 4- to 6-fold increase in the rate of electron flux through site I, which continues to operate in the over-all cyanide-insensitive path, the absolute levels of adenosine 5'-triphosphate will also be expected to increase in the presence of cyanide. The increase in sucrose content is considered to be the consequence of the rise in adenosine 5'-triphosphate concentration.
- Published
- 1975
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28. Interrelationship of Gene Expression, Polysome Prevalence, and Respiration during Ripening of Ethylene and/or Cyanide-Treated Avocado Fruit.
- Author
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Tucker ML and Laties GG
- Abstract
Upon initiation of ripening in avocado fruit (Persea americana Mill. cv Hass) with 10 microliters/liter ethylene, polysome prevalence and associated poly(A)(+) mRNA increase approximately 3-fold early in the respiratory climacteric and drop off to preclimacteric levels at the peak of the respiratory climacteric. The increase in poly(A)(+) mRNA on polysomes early in the respiratory climacteric constitutes a generic increase in constitutive mRNAs. New gene expression associated with ripening is minimal but evident after 10 hours of ethylene treatment and continues to increase relative to constitutive gene expression throughout the climacteric. The respiratory climacteric can be temporally separated into two phases. The first phase is associated with a general increase in protein synthesis, whereas the second phase reflects new gene expression and accumulation of corresponding proteins which may be responsible for softening and other ripening characteristics. A major new message on polysomes that arises concomitantly with the respiratory climacteric codes for an in vitro translation product of 53 kilodaltons which is immunoprecipitated by antiserum against avocado fruit cellulase.Cyanide at 500 microliters/liter fails to affect the change in polysome prevalance or new gene expression associated with the ethylene-evoked climacteric in avocado fruit. Treatment of fruit with 500 microliters/liter cyanide alone initiates a respiratory increase within 4 hours, ethylene biosynthesis within 18 hours, and new gene expression akin to that educed by ethylene within 20 hours of exposure to cyanide.
- Published
- 1984
- Full Text
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29. Respiratory Contribution of the Alternate Path during Various Stages of Ripening in Avocado and Banana Fruits.
- Author
-
Theologis A and Laties GG
- Abstract
The respiration of fresh slices of preclimacteric avocado (Persea americana Mill. var. Hass) and banana (Musa cavendishii var. Valery) fruits is stimulated by cyanide and antimycin. The respiration is sensitive to m-chlorobenzhydroxamic acid in the presence of cyanide but much less so in the presence of antimycin. In the absence of cyanide the contribution of the cyanide-resistant pathway to the coupled preclimacteric respiration is zero. In uncoupled slices, by contrast, the alternate path is engaged and utilized fully in avocado, and extensively in banana. Midclimacteric and peak climacteric slices are also cyanide-resistant and, in the presence of cyanide, sensitive to m-chlorobenzhydroxamic acid. In the absence of uncoupler there is no contribution by the alternate path in either tissue. In uncoupled midclimacteric avocado slices the alternate path is fully engaged. Midclimacteric banana slices, however, do not respond to uncouplers, and the alternate path is not engaged. Avocado and banana slices at the climacteric peak neither respond to uncouplers nor utilize the alternate path in the presence or absence of uncoupler.The maximal capacities of the cytochrome and alternate paths, V(cyt) and V(alt), respectively, have been estimated in slices from preclimacteric and climacteric avocado fruit and found to remain unchanged. The total respiratory capacity in preclimacteric and climacteric slices exceeds the respiratory rise which attends fruit ripening. In banana V(alt) decreases slightly with ripening.The aging of thin preclimacteric avocado slices in moist air results in ripening with an accompanying climacteric rise. In this case the alternate path is fully engaged at the climacteric peak, and the respiration represents the total potential respiratory capacity present in preclimacteric tissue. The respiratory climacteric in intact avocado and banana fruits is cytochrome path-mediated, whereas the respiratory climacteric of ripened thin avocado slices comprises the alternate as well as the cytochrome path. The ripening of intact fruits is seemingly independent of the nature of the electron transport path.Uncouplers are thought to stimulate glycolysis to the point where the glycolytic flux exceeds the oxidative capacity of the cytochrome path, with the result that the alternate path is engaged.
- Published
- 1978
- Full Text
- View/download PDF
30. Membrane-Associated NAD-Dependent Isocitrate Dehydrogenase in Potato Mitochondria.
- Author
-
Laties GG
- Abstract
The oxidation isotherms for citrate and isocitrate by potato (Solanum tuberosum var. Russet Burbank) mitochondria in the presence of NAD differ markedly. Citrate oxidation shows positively cooperative kinetics with a sigmoid isotherm, whereas isocitrate oxidation shows Michaelis-Menten kinetics at concentrations up to 3 millimolar, and cooperative kinetics thereafter up to 30 millimolar. In the absence of exogenous NAD, the isocitrate isotherm is sigmoid throughout. The dual isotherm for isocitrate oxidation in the presence of exogenous NAD reflects the operation of two forms of isocitrate dehydrogenase, one in the matrix and one associated with the inner mitochondrial membrane. Whereas in intact mitochondria the activity of the membrane-bound enzyme is insensitive to rotenone, and to butylmalonate, an inhibitor of organic acid transport, isocitrate oxidation by the soluble matrix enzyme is inhibited by both. The membrane-bound isocitrate dehydrogenase does not operate through the NADH dehydrogenase on the outer face of the inner mitochondrial membrane, and is thus considered to face inward. The regulatory potential of isocitrate dehydrogenase in potato mitochondria may be realized by the apportionment of the enzyme between its soluble and bound forms.
- Published
- 1983
- Full Text
- View/download PDF
31. Induction of ethylene of cyanide-resistant respiration.
- Author
-
Solomos T and Laties GG
- Subjects
- Fruit, Kinetics, Mitochondria drug effects, Mitochondria metabolism, Seeds metabolism, Species Specificity, Cyanides pharmacology, Ethylenes pharmacology, Oxygen Consumption drug effects, Plants metabolism
- Published
- 1976
- Full Text
- View/download PDF
32. Purification and characterization of an a type phospholipase from potato and its effect on potato mitochondria.
- Author
-
Hasson EP and Laties GG
- Abstract
A potato (Solanum tuberosum) phospholipid acyl-hydrolase, which - in the pH range 7.5 to 8.5-is at least 10,000 times more effective with phospholipids than with galactolipids, has been purified and characterized. It is a soluble enzyme readily distinguished from a neutral lipid lipase and a third lipid acyl-hydrolase which, while acting on phospholipid, shows a decided preference for glyceryl monoolein. The phospholipase in question has a pH optimum of 8.5, is stimulated by Ca(2+) at pH above 7.5 and inhibited by Ca(2+) at lower pH, is not dependent on detergents although stimulated by Triton X-100 to a moderate extent, and remains very active at temperatures close to zero. The phospholipids of intact potato mitochondria are highly susceptible to degradation by potato phospholipase, and it is suggested that this enzyme is involved in the extensive lipid breakdown which occurs in fresh potato slices following cutting, and in the deterioration of mitochondria during their preparation and aging.
- Published
- 1976
- Full Text
- View/download PDF
33. Dependence of Wound-induced Respiration in Potato Slices on the Time-restricted Actinomycin-sensitive Biosynthesis of Phospholipid.
- Author
-
Waring AJ and Laties GG
- Abstract
Actinomycin D prevents the full development in a 24-hour period of both wound respiration and cyanide resistance only when given in the first 10 to 12 hours following the cutting of potato tuber (Solanum tuberosum var. Russet) slices. The capacity for choline incorporation into phosphatidylcholine increases with slice aging and is inhibited by actinomycin D in the same time-restricted way. The time-restricted effectiveness of actinomycin D applies to the cutting-elicited enhanced synthesis of three critical enzymes of phosphatidylcholine synthesis, namely phosphorylcholine-glyceride transferase, phosphorylcholine-cytidyl transferase, and phosphatidylphosphatase. By contrast, actinomycim D given at any time is without effect on the measurable levels after 24 hours of a selection of glycolytic and mitochondrial respiratory enzymes. Neither succinic dehydrogenase nor cytochrome oxidase activity increases with time in aging potato slices in the presence or absence of chloramphenicol. The foregoing observations emphasize the central role of phospholipid, and ultimately membrane biosynthesis, in the development of wound-induced respiration.
- Published
- 1977
- Full Text
- View/download PDF
34. Disulfiram inhibition of the alternative respiratory pathway in plant mitochondria.
- Author
-
Grover SD and Laties GG
- Abstract
Disulfiram (tetraethylthiuram disulfide) was found to be a potent and selective inhibitor of the alternative respiratory path of plant mitochondria. The onset of inhibition by disulfiram takes several minutes and the inhibition is not readily reversed by washing, nor by metal ions. By contrast, thiols such as dithiothreitol not only reverse, but also prevent, disulfiram inhibition. Inhibition by disulfiram and by hydroxamic acids are not mutually exclusive. Structural analogs of disulfiram are far less potent inhibitors, with the exception of bisethyl xanthogen. Inhibition is due to disulfiram, per se, and not to its reduction product, diethyldithiocarbamate, a powerful chelator. Accordingly, the inhibitory effect of disulfiram is considered to involve the formation of mixed disulfides with one or more sulfhydryl groups in the alternative path. Disulfiram does not act as an electron sink diverting electron flow from oxygen.Disulfiram inhibition was observed only with isolated mitochondria or submitochondrial particles. In intact cells or tissues either a failure to absorb disulfiram, or its dissipation in the cytosol, precludes inhibition. In vitro, bovine serum albumin reduces disulfiram inhibition by complexing free inhibitor.The binding of (35)S-disulfiram by cyanide-resistant mitochondria displays the same kinetics as disulfiram inhibition. A comparison was made of (35)S-disulfiram binding by cyanide-sensitive and cyanide-resistant potato mitochondria. Cyanide-resistant mitochondria were obtained from ethylene-treated potato tubers. Incorporation of label proved essentially the same in both types of mitochondria, suggesting that the disulfiram-sensitive component of the alternative path is present in untreated potato tubers, and is not induced by ethylene.
- Published
- 1981
- Full Text
- View/download PDF
35. Separation and characterization of potato lipid acylhydrolases.
- Author
-
Hasson EP and Laties GG
- Abstract
Three distinct potato (Solanum tuberosum) lipid acyl-hydrolases have been isolated and characterized. Nonfluorescent esters of the fluorescent alcohols, N-methylindoxyl and N-methylumbelliferone, have been used as convenient substrates for lipid acyl-hydrolase estimation. Enzyme I has been shown to be a neutral lipase which favors glyceryl triolein over the di- and monoolein, which shows no activity with phospho- and galactolipids and which favors long chain fatty acid esters of N-methylindoxyl over the butyrate ester. Enzyme II, while attacking glyceryl mono- and diolein, as well as favoring the butyrate ester of N-methylindoxyl over the myristate ester, is basically a phospholipid and galactolipid acyl-hydrolase. Enzyme III may reasonably be considered an esterase, since it hydrolyzes glyceryl monoolein exclusively among the neutral lipids, shows minimal activity on phospho- and galactolipids, and hydrolyzes N-methylindoxylbutyrate exclusively compared with N-methylindoxyl-myristate.
- Published
- 1976
- Full Text
- View/download PDF
36. Ethylene-regulated gene transcription in carrot roots.
- Author
-
Nichols SE and Laties GG
- Abstract
The plant hormone ethylene elicits many biochemical changes in target tissues. To investigate ethylene effects on expression of genetic information, cDNA clones corresponding to ethylene-induced carrot root mRNAs were constructed and isolated. RNA dot blot analysis showed that for the three clones studied peak cytosolic mRNA prevalence occurred at 21 h of treatment followed thereafter by rapid messenger decay. DNA filter excess hybridization to in vitro synthesized nuclear RNA showed that the ethylene-induced mRNA increase is engendered by transcription of previously quiescent genes. The kinetics and magnitude of changes in mRNA prevalence parallel changes in transcriptional activity; therefore the ethylene effect is primarily at the level of transcription. In vivo pulse labelling with [(35)S]-methionine showed that between 18 and 27 h of ethylene treatment a 2.5 fold increase in translational efficiency occurred for one message studied. The resulting protein is the predominant protein synthesized in carrots treated with ethylene for 27 h. Thus ethylene seemingly exerts multiple regulatory controls on the expression of genetic information.
- Published
- 1984
- Full Text
- View/download PDF
37. Site-specific binding of a nuclear factor to the carrot extensin gene is influenced by both ethylene and wounding.
- Author
-
Holdsworth MJ and Laties GG
- Abstract
Experiments conducted in vitro using the electrophoretic mobility shift assay have shown that a single region of the extensin gene of carrot (Daucus carota L.) interacts with a protein factor designated Extensin Gene Binding Factor-1 (EGBF-1) present in nuclear extracts obtained from carrot roots. This interaction is sequence-specific as judged by the failure of other plant gene sequences to compete with the extensin gene for EGBF-1 binding. The EGBF-1 activity is organspecific, not being expressed in nuclear extracts obtained from carrot leaves or stems. Both ethylene treatment and wounding of roots are shown to have a controlling influence on the expression of EGBF-1 activity in nuclear extracts. These results demonstrate that at least three distinct signals: ethylene treatment, wounding, and development, are important in determining the activity of EGBF-1 in nuclear extracts, and indicate a role for EGBF-1 in stress-related signal transduction and the regulation of extensin-gene expression.
- Published
- 1989
- Full Text
- View/download PDF
38. Potentiating effect of pure oxygen on the enhancement of respiration by ethylene in plant storage organs: a comparative study.
- Author
-
Theologis A and Laties GG
- Abstract
A number of fruits and bulky storage organs were studied with respect to the effect of pure O(2) on the extent and time-course of the respiratory rise induced by ethylene. In one group, of which potato (Solanum tuberosum var. Russet) and carrot (Daucus carota) are examples, the response to ethylene in O(2) is much greater than in air. In a second group, of which avocado (Persea americana Mill. var. Hass) and banana (Musa cavendishii Lambert var. Valery) are examples, air and O(2) are equally effective. When O(2)-responsive organs are peeled, air and O(2) synergize the ethylene response to the same extent in parsnip (Pastinaca sativa), whereas O(2) is more stimulatory than air in carrots. In the latter instance, carrot flesh is considered to contribute significantly to diffusion resistance. The release of CO(2), an ethylene antagonist, is recognized as another element in the response to peeling.The potentiating effect of O(2) is considered to be primarily on ethylene action in the development of the respiratory rise rather than on the respiration process per se. On the assumption that diffusion controls O(2) movement into bulky organs and the peel represents the major diffusion barrier, simple calculations indicate that the O(2) concentration in untreated organs in air readily sustains respiration. Furthermore, in ethylene-treated organs in pure O(2), the internal O(2) concentration is more than enough to maintain the high respiration rates. Skin conductivity to O(2) is the fundamental parameter differentiating O(2)-responsive from O(2)-nonresponsive fruits and bulky storage organs. The large preceding the earliest response to ethylene, as well as the magnitude of the ethylene-induced respiratory rise, is also controlled by permeability characteristics of the peel.
- Published
- 1982
- Full Text
- View/download PDF
39. Cyanide-resistant Respiration in Fresh and Aged Sweet Potato Slices.
- Author
-
Theologis A and Laties GG
- Abstract
The respiration of fresh sweet potato (Ipomoea batatas) slices is resistant to, and often stimulated by, cyanide and antimycin A. m-Chlorobenzhydroxamic acid (CLAM), a selective inhibitor of the alternate path, inhibits respiration in the presence of cyanide and has a limited inhibitory effect in the presence of antimycin A. Thus, a partial bypass of the antimycinsensitive site is indicated. Respiration rises 2-fold at best with slice aging, the increment being cytochrome-mediated. The cyanide-resistant pathway contributes neither to coupled fresh slice respiration nor to the induced respiration in the absence of inhibitors of the cytochrome path. In the presence of uncoupler, however, the alternate path is engaged both in fresh and aged slices. V(cyt), the maximal capacity of the cytochrome path, remains essentially the same with slice aging, whereas V(alt) decreases from 20 to 60 per cent. The induced respiration is readily accommodated by the potential cytochrome path capacity of fresh slices, which is realized on aging. Accordingly, there is no need to invoke mitochondrial proliferation in explanation of the development of the induced respiration. The engagement of the alternate path in response to uncoupler reflects substrate mobilization to a degree that substrate oxidation exceeds the electron transport capacity of the cytochrome path.Fresh slices do not utilize exogenous substrates, whereas aged slices do so readily. Cerulenin, a specific inhibitor of fatty acid synthesis, prevents the development of the induced respiration as well as the capacity to oxidize exogenous substrates. It is suggested that lipid, and ultimately membrane, biosynthesis is central to the development of the induced respiration and the ability to use exogenous substrates, much as in potato.
- Published
- 1978
- Full Text
- View/download PDF
40. Effects of Cyanide and Ethylene on the Respiration of Cyanide-sensitive and Cyanide-resistant Plant Tissues.
- Author
-
Solomos T and Laties GG
- Abstract
The effects of cyanide and ethylene, respectively, were studied on the respiration of a fully cyanide-sensitive tissue-the fresh pea, a slightly cyanide-sensitive tissue-the germinating pea seedling, and a cyanide-insensitive tissue-the cherimoya fruit. Cyanide inhibition of both fresh pea and pea seedling respiration was attended by a conventional Pasteur effect where fermentation was enhanced with an accumulation of lactate and ethanol and a change in the level of glycolytic intermediates indicative of the activation of phosphofructokinase and pyruvate kinase accompanied by a sharp decline in ATP level. In these tissues, ethylene had little or no effect on the respiration rate, or on the level of glycolytic intermediates or ATP. By contrast, ethylene as well as cyanide enhanced both respiration and aerobic glycolysis in cherimoya fruits with no buildup of lactate and ethanol and with an increase in the level of ATP. The data support the proposition that for ethylene to stimulate respiration the capacity for cyanide-resistant respiration must be present.
- Published
- 1976
- Full Text
- View/download PDF
41. Selective enhancement of alternative path capacity in plant storage organs in response to ethylene plus oxygen: a comparative study.
- Author
-
Theologis A and Laties GG
- Abstract
The respiration rise in bulky storage organs induced by ethylene plus pure O(2) is accompanied by an increase in the CN-resistant respiration, or alternative path. Whereas a lesser respiratory stimulation in response to ethylene is demonstrable in air and increased by peeling, ethylene-induced alternative path development depends on the synergistic effect of pure O(2), with or without peeling. The effect of ethylene plus O(2) is evident, whether untreated parent organs yield CN-sensitive or CN-resistant fresh slices. Alternative path capacity and maximal cytochrome oxidase-mediated electron transport have been separately estimated. Ethylene plus O(2) selectively enhances the alternative path. It is proposed that the gross rise in respiration evoked by ethylene is implemented by a system with an O(2) requirement much higher than that of cytochrome oxidase, while the ethylene-induced development of the alternative path depends on a system of still higher O(2) requirement.
- Published
- 1982
- Full Text
- View/download PDF
42. Effect of chloral hydrate and acetaldehyde on mitochondrial preparations from sweet potato.
- Author
-
Pierpoint WS and Laties GG
- Abstract
The inhibitory effects of chloral hydrate and acetaldehyde have been studied on oxidations performed by mitochondrial preparations of sweet potatoes (Ipomea batatas). With a variety of substrates, chloral acts very like amytal but only between a fifth and a tenth as effectively; it affects those reactions which would be expected to depend on the oxidation of intramitochondrial DPNH, more than the oxidation of succinate or of added DPNH. It also acts like amytal when oxygen is replaced by other electron accepting agents. It is more effective, for example, against the malate reduction of cytochrome c than against the malate reduction of 2:6-dichlorophenol-indophenol.Inhibitions producd by acetaldehyde are more complex. Some DPN-dependent oxidations, especially those of pyruvate and alpha-keto-glutarate, are strongly inhibited, while that of citrate is not.It is suggested that chloral affects the electron transport sequence of sweet potato mitochondria at a similar locus to amytal. Although the present work fails to provide unambiguous evidence that acetaldehyde acts in the same manner, experiments described in the literature have been interpreted in this way.
- Published
- 1966
- Full Text
- View/download PDF
43. The Relation of Glucose Absorption to Respiration in Potato Slices.
- Author
-
Laties GG
- Published
- 1964
- Full Text
- View/download PDF
44. Limitations of the use of potassium hydroxide-potassium cyanide mixture in manometric studies.
- Author
-
LATIES GG
- Subjects
- Cyanides, Hydroxides, Manometry instrumentation, Potassium, Potassium Compounds, Potassium Cyanide
- Published
- 1949
45. Ribosomal RNA synthesis in newly sliced discs of potato tuber.
- Author
-
Sampson MJ and Laties GG
- Abstract
A burst of ribosomal RNA synthesis is induced in potato tissue by slicing, and continues at a decreasing rate for about 12 hours. Ribosomal RNA synthesis in potato discs is sensitive to puromycin, in contrast to non-ribosomal RNA synthesis. Thus, the influence of puromycin on total RNA synthesis is significant only during the first 12 hours following slicing. The function of RNA made after 12 hours in a puromycin-insensitive manner is unknown. However, it is apparently unrelated to protein synthesis, since it has been shown that total inhibition of RNA synthesis by addition of actinomycin D to potato tissue after 12 hours of aging has no effect upon protein synthesis during the ensuing 12 hours.
- Published
- 1968
- Full Text
- View/download PDF
46. Inhibition of RNA and protein synthesis by chloral in potato slices.
- Author
-
Laties GG
- Subjects
- In Vitro Techniques, Chloral Hydrate pharmacology, Plant Proteins biosynthesis, RNA biosynthesis
- Published
- 1965
- Full Text
- View/download PDF
47. Reversible changes in conformation of mitochondria of constant volume.
- Author
-
Laties GG and Treffry T
- Abstract
When potato mitochondria are prepared in a suitable isotonic or hypertonic medium, their morphology depends upon whether or not a macromolecular solute is present in the final suspending medium. Any of several chemically disparate polymers or macromolecules, above a certain critical concentration, will produce filamentous or rod-like mitochondria, which morphologically resemble mitochondria in the living cell. Below this critical level, or in the absence of a suitable macromolecular solute, mitochondria are spherical, even in hypertonic solution. The transition from rod-like to spherical morphology is reversible, rapid and independent of metabolism. Swelling of the mitochondria is not involved, since there is no change in mitochondrial fresh weight, nor in the optical density of mitochondrial suspensions when mitochondria are transformed from one form to the other. Alternative mechanisms, based either on screening interaction between macromolecules and the mitochondrial membrane, or on the reduction of mitochondrial interfacial tension, are proposed to account for the reversible changes in morphology. The reversible sphere to rod transition ostensibly depends upon the maintenance of mitochondrial resilience or elasticity, which in turn is considered to depend upon the presence of an appropriate chelator and sulfhydryl agent during the isolation process. In the absence of the latter, mitochondria are subsequently irreversibly spherical. Mercaptobenzothiazole effectively substitutes for a mixture of EDTA and cysteine.
- Published
- 1969
- Full Text
- View/download PDF
48. Influence of the Counter-ion on the Absorption Isotherm for Chloride at Low Temperature.
- Author
-
Laties GG, Macdonald IR, and Dainty J
- Published
- 1964
- Full Text
- View/download PDF
49. The role of state 4 electron transport in the activation of state 3 respiration in potato mitochondria.
- Author
-
Raison JK, Laties GG, and Crompton M
- Subjects
- Adenosine Diphosphate metabolism, Adenosine Diphosphate pharmacology, Adenosine Triphosphate metabolism, Adenosine Triphosphate pharmacology, Amobarbital pharmacology, Electron Transport, Kinetics, Mitochondria drug effects, Oligomycins pharmacology, Oxidative Phosphorylation, Oxygen Consumption, Plant Cells, Time Factors, Uncoupling Agents pharmacology, Mitochondria metabolism, Plants metabolism
- Published
- 1973
- Full Text
- View/download PDF
50. An oxidative, cyanide-insensitive enzyme system in the chloroplasts of a higher plant.
- Author
-
LATIES GG
- Subjects
- Chloroplasts, Cyanides, Plants
- Published
- 1950
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