A Study of the Control of Glycolate Excretion in <i>Chlorella</i>

Colman, Brian; Miller, Anthony G.; Grodzinski, Bernard

doi:10.1104/pp.53.3.395

Cited by 33 publications

(14 citation statements)

References 22 publications

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“…In part, this position is based on observations on glycolate excretion by algae. However, it seems that significant glycolate excretion only occurs upon transfer of the algae from a high CO2 concentration to a low CO2 concentration (2,11,13,20,24,29), a condition in which photosynthesis is greatly suppressed (3,24). Even then glycolate excretion cannot account for the observed inhibition of photosynthesis by 02 (2) and either a direct inhibition is involved (2,8) or a large portion of the glycolate is metabolized.…”

Section: Discussionmentioning

confidence: 94%

“…Even then glycolate excretion cannot account for the observed inhibition of photosynthesis by 02 (2) and either a direct inhibition is involved (2,8) or a large portion of the glycolate is metabolized. Air-grown algae do not excrete glycolate (11,13,24,29) but since glycolate excretion can be forced using inhibitors (13,29,30), it is implied that in air, the glycolate is metabolized via the glycolate pathway (29,33). Most of our algae were grown in air and we could still not find any indication of CO2 evolution due to metabolism of glycolate in the glycolate pathway.…”

Section: Discussionmentioning

confidence: 99%

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Photosynthesis and Photorespiration in Algae

Lloyd¹,

Canvin²,

Culver³

1977

Plant Physiol.

147

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The CO2 exchange of several species of fresh water and marine algae was measured in the laboratory to determine whether photorespiration occurs in these organisms. The algae were positioned as thin layers on filter paper and the CO2 exchange determined in an open gas exchange system. In either 21 or 1% 02 there was little difference between 14CO2 and 12CO2 uptake. Apparent photosynthesis was the same in 2, 21, or 50% 02. The compensation points of all algae were less than 10 id 1-1.CO2 or 14CO2 evolution into C02-free air in the light was always less than the corresponding evolution in darkness. These observadons are inconsistent with the proposal that photorespiration exists in these algae.Algae are C3 plants but there is still controversy regarding the existence or nature of photorespiration (7,8,33). Many algae have been shown to produce glycolate (28,33) and to possess the enzymes of the glycolate pathway (28, 33). The inhibition of photosynthesis by 02 or the Warburg effect was first shown in algae, and has since been extensively studied (2, 34). Some workers, however, have found no effect of 02 on CO2 fixation in algae (1, 16, 18) and many algae show low compensation points (4,25,35) and release less CO2 in the light compared to the dark (7,17).In higher plants, CO2 evolution and CO2 exchange are the most extensively studied aspects of photorespiration (36). In algae, although CO2 evolution during photosynthesis has been implied (33), few studies have been performed on CO2 exchange because of the difficulties imposed by the aqueous medium. In view of the paucity of information and the diversity of observations and opinions on CO2 exchange in algae, we decided to investigate the CO2 exchange of several species of algae using an open gas analysis system such as that used for measurement of CO2 exchange in higher plants (15,26). MATERIALS AND METHODSThe following algae were obtained from the Indiana University Culture Collection, and were grown on Gorham's culture medium No. 11 (21) Scotia. These marine species were grown on a shaker without aeration with a 16-hr photoperiod.All species were grown at 25 C and a quantum flux density of 80 to 100 ,ueinsteins m-2 sec-'. All cultures were axenic with the exception of Mougeotia. Cells were harvested during linear growth phase, and concentrated, where necessary, by settling and decanting the medium. Algae were suspended as an "artificial leaf" (12) to facilitate gas exchange and rapid changes in gas composition. The cells were filtered on Whatman No. 3 filter paper, producing an even double layer of cells (4 x 4 cm). This square was cut out and enclosed in the leaf chamber for the gas analysis measurements. The total volume of medium on the filter paper was approximately 0.3 ml. Similar results were obtained when the algae were suspended on 10-gm Nitex nylon mesh (B and S. H.The open gas analysis system was as previously described (15, 26). Measurements were started about 30 min after the algae were placed in the leaf chamber because the rate of apparent ...

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Photosynthesis and Photorespiration in Algae

Lloyd¹,

Canvin²,

Culver³

1977

Plant Physiol.

147

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“…A decrease in the activity of the enzyme responsible for its initial oxidation, glycolate dehydrogenase, that corresponded with the increased excretion following growth on high levels of CO2 corroborated this notion (17). However, this correlation has been shown to break down in Chlorella pyrenoidosa (7) and Euglena (6) as well as in the following results with Chlamydomonas. In addition, the control of the glycolate balance by permeability and the availability of counterions was suggested in early work by Tolbert and Zill (24) and has been recently carefully examined in Scenedesmus by Findenegg (9).…”

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confidence: 82%

Limitations on the Utilization of Glycolate by Chlamydomonas reinhardtii

Spencer

Togasaki²

1981

Plant Physiol.

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Growth and shorter term incorporation measurements with both wild type Chiamydomonas reinWii and a mutant (F-60, lacking Recent gas exchange measurements with Chlamydomonas reinhardtii and other green algae (3, 5, 13) have indicated very low levels of photorespiration, thereby changing the perception of the role of glycolate in these organisms. An inducible mechanism for concentrating CO2 internally has been characterized (2). A high intracellular CO2 concentration enables the algal cell to avoid glycolate formation and photorespiratory gas exchange. This mechanism provides a good explanation for many of the well known changes in measurements of whole cell glycolate release; prominent glycolate excretion is seen only in cells grown with elevated levels of CO2 when there is little internal concentrating of CO2. The likelihood of variable glycolate formation and the observations of glycolate excretion by the cell raise questions about the maximum capacity and the variability of glycolate utilization.The very existence of glycolate excretion suggests that turnover is at times limited. However, radioisotopic and enzymic analyses have indicated that the potential for carbon flow through the glycolate pathway of higher plants exists in including the present study, has noted the limitations of such utilization by green algae (23).Before the awareness of active CO2 concentration it was concluded that differences in metabolism were responsible for changes in the excretion of glycolate. A decrease in the activity of the enzyme responsible for its initial oxidation, glycolate dehydrogenase, that corresponded with the increased excretion following growth on high levels of CO2 corroborated this notion (17). However, this correlation has been shown to break down in Chlorella pyrenoidosa (7) and Euglena (6) as well as in the following results with Chlamydomonas. In addition, the control of the glycolate balance by permeability and the availability of counterions was suggested in early work by Tolbert and Zill (24) and has been recently carefully examined in Scenedesmus by Findenegg (9). The latter study concluded that permeability can be the primary controlling factor in the uptake and release of glycolate.In this report the potential for utilization of internal glycolate is estimated by several methods. At a low pH, the permeability barrier of glycolate into the cell is relieved. The effects of various growth conditions are determined. Incorporation studies with the F-60 mutant are particularly important in measuring true heterotrophic glycolate utilization. Because of its phosphoribulokinase lesion, this mutant can produce little glycolate. The effects of the metabolic inhibitor isonicotinyl hydrazide are also measured. MATERIALS AND METHODSCell Culture. The MM3 of Sueoka (21) was used with the following modifications: 15 mm potassium acetate was added to make MA; 15 mm potassium glycolate was added to make MG; 10 mm glycylglycine buffer (pH 3.8) was added to medium which contained only one-sixth of the phosphate...

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“…Yet these algae fail to show the sympton~ of photorespiration (02 inhibition of photosynthesis, glycolate excretion) that are readily apparent when the same algae are cultured under CO2 enriched conditions [56,[80][81][82][83][84][85]. It has been suggested [56] that the cells adapted to growth on limiting carbon may have a CO2 concentrating mechanism.…”

Section: Rup2 Carboxylase-oxygenase In Plants Lacking the External Mamentioning

confidence: 99%