The effect of osmotic stress on the oxidation of glycolate by the blue-green alga Anacystis nidulans

Grodzinski, Bernard; Colman, Brian

doi:10.1007/bf00384754

Cited by 14 publications

(8 citation statements)

References 26 publications

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“…This maximum rate was similar to those in all dark treatments (Table I 10 Mm DCMU (data not shown), although photosynthesis and refixation of CO2 derived from glycolate was inhibited by DCMU in the same manner as reported in other photosynthetic systems (12,26). When leaf discs were incubated in the light with the photosynthetic inhibitor, DCMU, glycolate did not stimulate C2H4 release above the rate attributable to DCMU alone (Table II).…”

Section: Resultssupporting

confidence: 83%

“…Although previous studies indicate that net photosynthesis and dark respiration are not markedly affected by the application of 0.5 mM ACC (8-10), at present there are no published data indicating whether ACC and/or C2H4 can modify glycolate metabolism over the duration of such experiments. The data in Table I demonstrate that exogenously supplied [I-'4C]glycolate was taken up and metabolized to '4CO2 in both the light and the dark by Salvia leaf discs as observed previously (11,12,26). The addition of 0.5 mm ACC did not alter glycolate decarboxylation in either the light or the dark (Table I).…”

Section: Resultssupporting

confidence: 79%

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Enhancement of Ethylene Release from Leaf Tissue during Glycolate Decarboxylation

Grodzinski

1984

Plant Physiol.

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When leaf discs of Xanthium strumarium L. and Saivia spkndens L. are incubated in sealed flasks in the light, more C2H4 gas is released in the presence of added CO2 (30-200 millimolar NaHCO3) than without CO2. In Salvia, the maximum rate of C2H1-release occurs when sufficient CO2 (above 125 millimolar NaHCO3) is added to saturate photosynthesis confirming previous studies. The maximum rate of C2H4 release from illuminated discs is similar to the rate in the dark with or without CO2 in both species. Glycolate enhances a CO2-dependent C2H-4 evolution from illuminated leaf discs. However, the maximum rate of C2H1-release with glycolate is the same as that observed with saturating CO2. When photosynthesis is inhibited by darkness or by 3-(3,4-dichlorophenyl)-1,1-dimethylurea, glycolate has no effect.Studies with 12,3-'4Cl--aminocyclopropane-l-carboxylic acid (ACC) show that the pattern of C2H4 release and the specific activity of the '4C2H4 in the presence and absence ofglycolate is similar to that described above, indicating that glycolate does not alter uptake of the exogenously supplied precursor (ACC) Recent studies from our laboratory with both C3 and C4 species indicate that the amount of carbon released in the light in the form of C2H4 gas is minute compared with either the rates of photosynthetic CO2 assimilation or CO2 losses from dark respiration or during photorespiration (8-10). However, these investigations have shown that the amount of C2H4 generated by photosynthetic tissue can be controlled by the availability of CO2. The relationship between CO2 levels and C2H1 production is an important consideration when leaf tissue is placed in a sealed flask in order to allow for the production and accumulation of sufficient C2H4 in the headspace of the flask for accurate assay by current gas chromatographic techniques. In all of the ' Supported by grants from the Natural Science and Engineering Council of Canada and the Ontario Ministry of Agriculture and Food. C3 and C4 leaf tissues which we have studied, C2H4 release by the tissue is lowest in the light when the tissue is allowed to deplete the CO2 level from 330 ppm (ambient) to the compensation point. In C3 plants, light and dark rates of C2H4 release are similar when CO2 is available for photosynthesis. In C4 plants when CO2 is available, C2H4 release is higher in the light than in the dark (8-10). In C4 plants, the internal CO, level may be raised 'naturally' in the light as a result of internal decarboxylation reactions. In our view (8, 10), failure to maintain CO2 levels around photosynthetic tissue has resulted in several erroneous reports that light is an inhibitor of C2H4 production.A sealed reaction flask creates an environment in which gas exchange is restricted. During the time period of an experiment (30-120 min), CO2 levels tend to approach the CO2 compensation point. Although CO2 can clearly become a limiting factor in C2H4 production (8)(9)(10)14) it must also be realized that at low CO2 concentrations glycolate metabolism (i.e. ...

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Section: Resultssupporting

confidence: 83%

Section: Resultssupporting

confidence: 79%

Enhancement of Ethylene Release from Leaf Tissue during Glycolate Decarboxylation

Grodzinski

1984

Plant Physiol.

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“…A number of unicellular eucaryotic algae have been found to have a glycolate pathway similar to that of higher plants, but there is no clear evidence for the association of the glycolate-oxidizing enzyme in these cells, glycolate dehydrogenase, with a microbody of the peroxisomal type (18). An enzyme catalyzing glycolate oxidation, similar to that in green algae, has been detected in several blue-green algae (11,12), and glycolate is readily oxidized to CO2 by these cells (5,13,19). The spatial location of this enzyme within the bluegreen algal cell is not known.…”

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confidence: 99%

Intracellular Localization of Glycolate Dehydrogenase in a Blue-Green Alga

Grodzinski

Colman²

1976

Plant Physiol.

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Glycolate dehydrogenase activity was detected in cell-free extracts of Oscillatoria sp. prepared by osmotic lysis of spheroplasts in 0.05 M potassium phosphate buffer, pH 7.5, containing 0.3 M mannitol. Most of the enzyme activity was found in a particulate fraction and localized in the photosynthetic lameliae after centrifugation in a discontinuous sucrose density gradient. Enzyme activity was detected in this fraction both in the presence and absence of the artificial electron acceptor 2,6-dichlorophenolindophenol (DPIP) and a low rate of 02 uptake was detected in this lameilar fraction. Activity was lost from the lamellar fraction by repeated washing or by treatment with 0.005% Triton X-100 and the solubilized enzyme activity was DPIP-dependent. The data indicate that both glycolate dehydrogenase and its natural electron acceptor are bound to the photosynthetic lamellae in vivo. In contrast, catalase activity was found in the soluble cytoplasmic fraction. obtained by lysing spheroplasts of the alga prepared in a manner similar to that described by Biggins (1). Washed cells were resuspended in 0.55 M mannitol-0.03 M K-phosphate buffer, pH 6.8, containing 0.06% (w/v) lysozyme (eggwhite muramidase, grade l, Sigma Chemical Co.) and incubated at 32 C with gentle agitation at a light intensity of 8 klux for about 2 hr. Spheroplasts prepared in this manner lysed more readily and uniformly than those prepared in the dark (9). After incubation any intact filaments were removed by filtration through loosely packed prechilled glass wool, the spheroplasts collected by centrifugation, washed twice with mannitol-phosphate buffer, pH 6.8, and lysed either in 0.05 M K-phosphate buffer, pH 7.5, containing 0.3 mm magnesium chloride, or in the same medium with 0.3 M mannitol. The viscosity of the resulting suspension was reduced by the addition of about 0.1 mg deoxyribonuclease/mg dry weight of cells. The suspension was centrifuged at 5000g for 40 min at 0 to 4 C and the resulting supernatant fluid, referred to as the crude lysate, was used for enzyme assay.Fractionation of Ceil-free Preparations. Particulate fractions were obtained from the crude lysates either by centrifugation at 10OOOOg for 90 min or by centrifugation at 45,000g for 4 hr in a discontinuous gradient of sucrose comprised of layers of 0.3, 0.5, 0.67, 1, 1.33, 1.67, and 1.9 M sucrose (Fig. 1) containing 0.05 M K-phosphate buffer, pH 7.5, and 0.3 mm magnesium chloride in a 40-ml polyallomer tube, at 0 to 4 C in an IEC B-60 ultracentrifuge equipped with a swinging bucket rotor. Samples were removed from the top of the gradient by pumping a 2.1 M sucrose solution through the bottom of the tube using an ISCO model 82 density gradient fractionator.Enzyme Assays. Glycolate dehydrogenase was assayed by determination of glyoxylate phenylhydrazone formation in the presence or absence of DPIP4 (11)

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“…Although little glycolate is produced, the initial enzymes of the glycolate pathway have been detected in cyanobacteria. While the reported activities of glycolate dehydrogenase are low (0.9 to 3.5 nmol substrate mg"' protein min"'; Stewart 1973, Grodzinski andColman 1975), phosphoglycolate phosphatase activity is relatively high (15 to 20 nmol substrate mg"' protein min"') presumably because this compound is a potent inhibitor of triose phosphate isomerase, a key enzyme of the Calvin cycle (Norman and Colman 1991).…”

Section: Discussionmentioning

confidence: 99%

“…Much of the exogenous ['''C]-glycolate supplied to cyanobacteriai cells is oxidised to CO2 and its metabolism is not inhibited by isonicotinyl hydrazide, an inhibitor of the glycine to serine conversion in higher plants and green algae (Miller et al 1971, Codd and Stewart 1973, Grodzinski and Colman 1975. Activity of glyoxylate aminotransferases has been found in some cyanobacteria (16 to 19 nmol substrate mg"' protein min"'; Stewart 1973, Grodzinski andColman 1975) and there is some carbon flow from [''*C]-glycolate to glycine and to intermediates of the glyoxylate cycle (Pearce and Carr 1967, Codd and Stewart 1973, Norman and Colman 1992. However there is little or no serine formation from exogenous ['"^CJ-glycolate or ['^C]-glycine (Miller et al 1971, Codd and Stewart 1973, Norman and Colman 1992.…”

Section: Discussionmentioning

confidence: 99%