Malate Accumulation in Leaf Slices of Mesembryanthemum crystallinum in Relation to Osmotic Gradients Between the Cells and the Medium

1976 ◽  
Vol 3 (5) ◽  
pp. 653 ◽  
Author(s):  
K Winter ◽  
U Luttge
Keyword(s):  
Temperature Dependence ◽  
Osmotic Pressure ◽  
Incubation Medium ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Dark Period ◽  
Mesembryanthemum Crystallinum ◽  
Experimental Results ◽  
Carbon Gain ◽  
Intact Leaves

Leaf slices of two sets of M. crystallinum plants were used in the present study. The first set were plants grown in 400 mM NaCl and showing diurnal oscillations of malate levels typical of crassulacean acid metabolism (CAM). The second set were plants grown in non-saline media and exhibiting no CAM-like diurnal malate fluctuations. Both sets of leaf slices accumulated malate during a 12-h light or dark period, depending on the osmotic pressure of the incubation medium. Highest malate accumulations were obtained when media were isotonic or slightly hypertonic. These osmotic characteristics are similar to those of leaf slices of the CAM plant Kalanchoe daigremontiana as reported elsewhere. However, discrepancies are observed in light and temperature dependence. Unlike in K. daigremontiana leaf slices and in intact leaves with CAM (i.e. also in intact leaves of M. crystallinum grown on highly saline media), in both sets of M. crystallinum leaf slices used here light stimulated malate accumulation. Compared to 15°C, 25°C had either no effect on malate accumulation or stimulated malate accumulation. After leaf slices had accumulated malate in the dark in isotonic or slightly hypertonic media, malate accumulation continued in the light when the osmolarity of the medium remained unchanged. When the osmotic pressure of the medium was lowered considerably, however, malate accumulation in the light was much reduced or else there was a loss of malate from the tissue. Mechanisms different from CAM may be partially involved in the changes of malate levels in these experiments. The significance of the experimental results for the interpretation of the balance between net carbon gain via C3 pathway and CAM in M. crystallinum is discussed.

Change in Properties of Phosphoenolpyruvate Carboxylase From the Crassulacean Acid Metabolism Plant Mesembryanthemum crystallinum After Isolation

1981 ◽  
Vol 8 (1) ◽  
pp. 115 ◽  
Author(s):  
K Winter
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Molecular Basis ◽  
Enzyme Catalysis ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Dark Period ◽  
Mesembryanthemum Crystallinum ◽  
Cytoplasmic Ph ◽  
Strong Inhibitor ◽  
Crassulacean Acid Metabolism Plant

Phosphoenolpyruvate carboxylase (EC 4.1.1.31) in desalted extracts from the inducible crassulacean acid metabolism plant M. crystallinum exists in a highly malate-sensitive state when isolated from plants in the light, and after isolation rapidly changes into a less sensitive state typical of the dark period. Loss of sensitivity to malate inhibition after isolation is largely prevented when the enzyme is extracted and stored at acid pH and in the presence of malate. This demonstrates that, in addition to its effect as a strong inhibitor of enzyme catalysis during the light, malate may also maintain the highly malate-sensitive state of phosphoenolpyruvate carboxylase during the light, particularly in combination with a lowered cytoplasmic pH. These experiments also establish conditions necessary for the study of the molecular basis for the change in properties of phosphoenolpyruvate carboxylase.

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.

scholarly journals Transcriptional profiles of organellar metabolite transporters during induction of crassulacean acid metabolism in Mesembryanthemum crystallinum

2005 ◽  
Vol 32 (5) ◽  
pp. 451 ◽  
Author(s):  
Shin Kore-eda ◽  
Chiyuki Noake ◽  
Masahisa Ohishi ◽  
Jun-ichi Ohnishi ◽  
John C. Cushman
Keyword(s):  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Expression Patterns ◽  
Transcript Abundance ◽  
Transport Processes ◽  
Mesembryanthemum Crystallinum ◽  
Water Deficit Stress ◽  
Diurnal Changes ◽  
Metabolite Transport ◽  
Leaf Tissues

Metabolite transport across multiple organellar compartments is essential for the operation of crassulacean acid metabolism (CAM). To investigate potential circadian regulation of inter-organellar metabolite transport processes, we have identified eight full-length cDNAs encoding an organellar triose phosphate / Pi translocator (McTPT1), a phosphoenolpyruvate / Pi translocator (McPPT1), two glucose-6-phosphate / Pi translocators (McGPT1, 2), two plastidic Pi translocator-like proteins (McPTL1, 2), two adenylate transporters (McANT1, 2), a dicarboxylate transporter (McDCT2), and a partial cDNA encoding a second dicarboxylate transporter (McDCT1) in the model CAM plant, Mesembryanthemum crystallinum L. We next investigated day / night changes in steady-state transcript abundance of each of these transporters in plants performing either C3 photosynthesis or CAM induced by salinity or water-deficit stress. We observed that the expression of both isogenes of the glucose-6-phosphate / Pi translocator (McGPT1, 2) was enhanced by CAM induction, with McGPT2 transcripts exhibiting much more pronounced diurnal changes in transcript abundance than McGPT1. Transcripts for McTPT1, McPPT1, and McDCT1 also exhibited more pronounced diurnal changes in abundance in the CAM mode relative to the C3 mode. McGPT2 and McDCT1 transcripts exhibited sustained oscillations for at least 3 d under constant light and temperature conditions suggesting their expression is under circadian clock control. McTPT1 and McGPT2 transcripts were preferentially expressed in leaf tissues in either C3 or CAM modes. The leaf-specific and / or circadian controlled gene expression patterns are consistent with McTPT1, McGPT2 and McDCT1 playing CAM-specific metabolite transport roles.

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