Capacity of Enzymes of the Euphorbiacea Aleurites montana Involved in CO2- Fixation, Compared to Plants Having C3-, C4- and Crassulacean Acid Metabolism

2000 ◽  
Vol 55 (5-6) ◽  
pp. 383-391 ◽  
Author(s):  
Norbert Grotjohann ◽  
Ping He ◽  
Georg H. Schmid
Keyword(s):  
Sugar Cane ◽  
Malic Enzyme ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Saccharum Officinarum ◽  
Light Period ◽  
Ribulose Bisphosphate Carboxylase ◽  
Bisphosphate Carboxylase ◽  
Efficient Uptake ◽  
Low Activity

Capacities of phosphoenolpyruvate carboxylase (PEP-Co), ribulose bisphosphate carboxylase (Rubisco), NADP+ malic enzyme (ME) and of malate dehydrogenase (MDH) were measured in the Euphorbiacea Aleurites montana, grown under 700 ppm CO2 for four weeks prior to enzyme extraction. For comparison Bryophyllum daigremontiana (CAM), Saccharum officinarum (C4) and Capsicum frutescens (C3) were treated in the same way. PEP-Co capacity of Aleurites was in the range of 12-, that of Capsicum approx. 26 nmol × min-1 × mg protein-1, without significant influence of the light period or CO2-treatment. In contrast, the activity of the enzyme from Saccharum was. depending on the duration of light, 160- respectively 96 times higher than that of the tung-oil tree. In Bryophyllum a rather low activity in the morning was increased during the day to approx. 230 nmol × min-1 × mg protein-1 in plants grown in the greenhouse and to approx. 115 nmol × min-1 × mg protein-1 in those from the growth chamber. Malate was hardly detectable in extracts of Aleurites, whereas it was high in Bryophyllum, depending on the light period. The ratio of average PEP-Co to Rub-Co capacity was high for the CAM-plant (20:1), somewhat lower for sugar cane (10:1), but almost at equality for Aleurites (0.9:1) and chilli (0.8:1). For the NADP+ malic enzyme, low capacity (20 to 28 nmol x min-1 × mg protein-1) was found for Aleurites and for Capsicum, whereas it was 10 to 17 times higher in Saccharum. In Bryophyllum, the activity was up to 80 nmol × min-1 × mg protein , dependent on light period. MDH capacity was extremely high in all plants investigated. Highest rates (10-20 μmol × min-1 × mg protein-1), were obtained for Bryophyllum, followed by sugar cane and Capsicum with 5 -8 μmol × min-1 x mg protein-1. Again, the lowest capacity was found in extracts of Aleurites with approx. 1.3 to 1.6 μmol × min-1 × m protein-1. Thus, in Aleurites montana no indication for C4- or Crassulacean acid metabolism was obtained. Therefore, the earlier observed very efficient uptake of CO2 cannot be explained by a high expression of the PEP-Co protein, known to occur in CAM- and C4-plants.

Degrees of crassulacean acid metabolism in tropical epiphytic and lithophytic ferns

1999 ◽  
Vol 26 (8) ◽  
pp. 749 ◽  
Author(s):  
Joseph A.M. Holtum ◽  
Klaus Winter
Keyword(s):  
Carbon Isotope ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Dark Period ◽  
Titratable Acidity ◽  
Isotope Ratios ◽  
Light Period ◽  
Co2 Uptake ◽  
Carbon Isotope Ratios ◽  
Net Co2 Uptake

Crassulacean acid metabolism (CAM) was observed in three species of tropical ferns, the epiphytes Microsorium punctatum and Polypodium crassifolium and the lithophyte Platycerium veitchii. Polypodium crassifolium and P. veitchii exhibited characteristics of weak CAM. Although no net nocturnal CO2 uptake was observed, the presence of CAM was inferred from nocturnal increases in titratable acidity of 4.7 and 4.1 µequiv (g fr wt)–1 respectively, a reduction in the rates of net CO2 evolution during the first half of the dark period, and the presence of a CAM-like decrease in net CO2 uptake during the early light period. In M. punctatum net CO2 uptake during the first half of the dark period was accompanied by an increase in titratable acidity of 39.2 µequiv (g fr wt)–1 and a pronounced reduction in net CO2 uptake during the early light period. When water was withheld from P. crassifolium and M. punctatum, net CO2 uptake during the light was reduced markedly but there was no change in the extent or patterns of CO2 exhange in the dark. As a consequence, the proportion of carbon gained due to CO2 fixation in the dark increased from 2.8 and 10% to 63.5 and 49.3%, respectively (100% being net CO2 uptake during the light plus the estimated CO2 uptake during the dark). After 9 days without added water, dark CO2 uptake was responsible for the maintenance of a net 24 h carbon gain in P. crassifolium. Platycerium veitchii, P. crassifolium and M. punctatum exhibited carbon isotope ratios of between –25.9 and –22.6‰ indicating that carbon isotope ratios may not, by themselves, be sufficient for the identification of weak CAM. We suggest that CAM may be more prevalent in tropical epiphytic and lithophytic ferns than currently envisaged.

Regulation of Rubisco activity in crassulacean acid metabolism plants: better late than never

2002 ◽  
Vol 29 (6) ◽  
pp. 689 ◽  
Author(s):  
Kate Maxwell ◽  
Howard Griffiths ◽  
Brent Helliker ◽  
Andrew Roberts ◽  
Richard P. Haslam ◽  
...  
Keyword(s):  
Electron Transport ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Rubisco Activase ◽  
Light Period ◽  
Phase Iii ◽  
Co2 Uptake ◽  
Rubisco Activity ◽  
Free Atmosphere ◽  
Phase Iv

This paper originates from a presentation at the IIIrd International Congress on Crassulacean Acid Metabolism, Cape Tribulation, Queensland, Australia, August 2001. The diurnal regulation of Rubisco was compared for a range of crassulacean acid metabolism (CAM) species in the context of high carboxylation and electron transport capacities, which may be an order of magnitude greater than rates of net CO2 uptake. Early in the light period, Rubisco activity and electron transport were limited when phosphoenolpyruvate carboxylase (PEPC) may have been operating, and maximal extractable activities and activation state for Rubisco were achieved at the end of Phase III, prior to the direct atmospheric uptake of CO2 during Phase IV. The delayed activation was associated with levels of Rubisco activase protein, which reached a maximum at midday, and may account for this pattern of Rubisco activation. This regulation may be modified by environmental conditions - processes that tend to restrict PEPC activity, such as drought stress or incubation of leaves overnight in an oxygen-free atmosphere, release Rubisco from inhibition early in the light period. The quantum yield of light use also tracks Rubisco carboxylation, being particularly low at dawn when PEPC is active. The plasticity in expression of the CAM cycle is therefore matched by the regulation of key carboxylases, with extractable Rubisco activity maximal when drawdown of atmospheric CO2 to cells in succulent CAM tissues is most likely to limit photon utilization shortly after midday, during Phase IV.

scholarly journals Metabolic Modeling of the C3-CAM Continuum Revealed the Establishment of a Starch/Sugar-Malate Cycle in CAM Evolution

2021 ◽  
Vol 11 ◽  
Author(s):  
Ignacius Y. Y. Tay ◽  
Kristoforus Bryant Odang ◽  
C. Y. Maurice Cheung
Keyword(s):  
Crassulacean Acid Metabolism ◽  
Large Scale ◽  
Acid Metabolism ◽  
Metabolic Modeling ◽  
Light Period ◽  
Mitochondrial Electron Transport Chain ◽  
Metabolic Fluxes ◽  
Transport Chain ◽  
Use Efficiency ◽  
Constraint Based Modeling

The evolution of Crassulacean acid metabolism (CAM) is thought to be along a C3-CAM continuum including multiple variations of CAM such as CAM cycling and CAM idling. Here, we applied large-scale constraint-based modeling to investigate the metabolism and energetics of plants operating in C3, CAM, CAM cycling, and CAM idling. Our modeling results suggested that CAM cycling and CAM idling could be potential evolutionary intermediates in CAM evolution by establishing a starch/sugar-malate cycle. Our model analysis showed that by varying CO2 exchange during the light period, as a proxy of stomatal conductance, there exists a C3-CAM continuum with gradual metabolic changes, supporting the notion that evolution of CAM from C3 could occur solely through incremental changes in metabolic fluxes. Along the C3-CAM continuum, our model predicted changes in metabolic fluxes not only through the starch/sugar-malate cycle that is involved in CAM photosynthetic CO2 fixation but also other metabolic processes including the mitochondrial electron transport chain and the tricarboxylate acid cycle at night. These predictions could guide engineering efforts in introducing CAM into C3 crops for improved water use efficiency.

Intracellular transport and pathways of carbon flow in plants with crassulacean acid metabolism

2005 ◽  
Vol 32 (5) ◽  
pp. 429 ◽  
Author(s):  
Joseph A. M. Holtum ◽  
J. Andrew C. Smith ◽  
H. Ekkehard Neuhaus
Keyword(s):  
Malic Enzyme ◽  
Crassulacean Acid Metabolism ◽  
Intracellular Transport ◽  
Acid Metabolism ◽  
Soluble Sugar ◽  
Carbon Flow ◽  
Mitochondrial Transporter ◽  
Photosynthetic Carbon Metabolism ◽  
Pep Carboxykinase ◽  
Reciprocal Transfer

The massive daily reciprocal transfer of carbon between acids and carbohydrates that is unique to crassulacean acid metabolism (CAM) involves extensive and regulated transport of metabolites between chloroplasts, vacuoles, the cytosol and mitochondria. In this review of the CAM pathways of carbon flow and intracellular transport, we highlight what is known and what has been postulated. For three of the four CAM pathway variants currently known (malic enzyme- or PEP carboxykinase-type decarboxylase, and starch- or soluble sugar-type carbohydrate storage), the mechanisms of intracellular transport are still hypothetical and have yet to be demonstrated experimentally. Even in malic enzyme starch-storing species such as Kalanchoë daigremontiana Hamet et Perr. and Mesembryanthemum crystallinum L., the best-described variants of plants with the second-most common mode of photosynthetic carbon metabolism known, no tonoplast or mitochondrial transporter has been functionally described at a molecular level.

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