The Gluconeogenic Metabolism of Pyruvate During Deacidification in Plants With Crassulacean Acid Metabolism

1981 ◽  
Vol 8 (1) ◽  
pp. 31 ◽  
Author(s):  
JAM Holtum ◽  
CB Osmond
Keyword(s):  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Tricarboxylic Acid Cycle ◽  
Mesembryanthemum Crystallinum ◽  
C3 Plants ◽  
Cam Plants ◽  
Mesophyll Cells ◽  
14Co2 Fixation ◽  
Cam Plant ◽  
Pep Carboxykinase

Pyruvate, PI dikinase (EC 2.7.9.1) was present in crassulacean acid metabolism (CAM) plants that lack phosphoenolpyruvate (PEP) carboxykinase (EC 4.1.1.32) but was not detected in plants that contain PEP carboxykinase or in C3 plants. It is suggested that, during deacidification in CAM plants that contain NAD and NADP malic enzymes (EC 1.1.1.38 and EC 1.1.1.40) but not PEP carboxykinase, pyruvate, P*i dikinase reverses the glycolytic reaction catalysed by pyruvate kinase (EC 2.7.1.40) and converts pyruvate to PEP as the first step in the gluconeogenic conservation of pyruvate as storage carbohydrate. The enzyme is not required by CAM plants that contain PEP carboxykinase and produce mainly PEP during decarboxylation. Leaf slices from Kalanchoe daigremontiana and CAM Mesembryanthemum crystallinum, two species that possess pyruvate, PI dikinase, transfer label from exogenous [3-14C]pyruvate to carbohydrates more rapidly than either Stapelia gigantea, a PEP carboxykinase CAM plant, or C3 Mesembryanthemum crystallinum, which lack the dikinase. Label from [2-14C]- and [3-14C]pyruvate is converted to carbohydrate at the same rate in K. daigremontiana while in S. gigantea label from [2-14C]pyruvate accumulates in carbohydrates twice as rapidly as label from [3-14C]pyruvate. The patterns observed for K. daigremontiana and for CAM M. crystallinum are consistent with the gluconeogenic anabolism of pyruvate whereas the patterns observed for S. gigantea and for C.3 M. crystallinum suggest pyruvate is oxidized possibly via the tricarboxylic acid cycle in these species. Deacidification in Aloe arborescens, a PEP carboxykinase CAM plant that also possesses NAD and NADP malic enzyme activity, was inhibited 80% by 0.1 mM 3-mercaptopicolinic acid (3-MPA), an inhibitor of PEP carboxykinase. It is thus likely that, in this species and probably also in other CAM plants with high PEP carboxykinase activities, a small proportion of the malic acid may be decarboxylated by malic enzymes. However, as 0.5 mM 3-MPA inhibited deacidification in K. daigremontiana by 40%, the inhibitor is probably only specific at low concentrations. 14CO2 fixation in the light by mesophyll cells isolated from K. daigremontiana was stimulated by 20-50% in the presence of 10 mM pyruvate, but there was no increase in 14CO2 fixation by mesophyll cells isolated from S. gigantea.

Kinetic Properties of Phosphorylase and 6-Phosphofructokinase of Kalanchoe daigremontiana and Atriplex spongiosa

1975 ◽  
Vol 2 (3) ◽  
pp. 403 ◽  
Author(s):  
G Sutton
Keyword(s):  
Carbohydrate Metabolism ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Kinetic Properties ◽  
C4 Plant ◽  
Cam Plants ◽  
Regulation Of Carbohydrate Metabolism ◽  
Cam Plant ◽  
Kalanchoë Daigremontiana ◽  
Kalanchoe Daigremontiana

The kinetic properties of phosphorylase (EC 2.4.1.1) and 6-phosphofructokinase (EC 2.7.1.11) extracted from a crassulacean acid metabolism (CAM) plant, Kalanchoe daigremontiana Hamet et Perrier, and a C4 plant, Atriplex spongiosa F. Muell., were compared. The phosphorylase from the CAM plant was strongly inhibited by P1 (1 mM), phosphoenolpyruvate (PEP) (2 mM) and glucose (4 mM). The C4 phosphorylase was less strongly inhibited by P1, and not at all by PEP or glucose. The C4 6-phosphofructokinase was, at Km levels of substrate, about 100 times more sensitive to inhibition by PEP than the CAM enzyme. These results are discussed as the basis for a biochemical regulation of carbohydrate metabolism in CAM plants at night.

Functional leaf anatomy of plants with crassulacean acid metabolism

2005 ◽  
Vol 32 (5) ◽  
pp. 409 ◽  
Author(s):  
Elizabeth A. Nelson ◽  
Tammy L. Sage ◽  
Rowan F. Sage
Keyword(s):  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Internal Resistance ◽  
C3 Plants ◽  
Cam Plants ◽  
Internal Co2 ◽  
Low Exposure ◽  
Cam Species ◽  
Diffusional Barrier ◽  
Carbon Economy

Crassulacean acid metabolism (CAM) has evolved independently on dozens of occasions and is now found in over 7% of plant species. In this study, the leaf structure of a phylogenetically diverse assemblage of 18 CAM plants was compared with six C3 plants and four C4 plants to assess whether consistent anatomical patterns that may reflect functional constraints are present. CAM plants exhibited increased cell size and increased leaf and mesophyll thickness relative to C3 and C4 species. CAM species also exhibited reduced intercellular air space (IAS) and reduced length of mesophyll surface exposed to IAS per unit area (Lmes / area). The low volume of IAS and low exposure of mesophyll surface to IAS likely increases internal resistance to CO2 in CAM tissues. While this diffusional barrier may limit uptake of CO2 during Phases II and IV, carbon economy could be enhanced through the reduced loss of internal CO2 during all four phases of CAM.

Crassulacean Acid Metabolism and Diurnal Variations of Internal CO2 and O2 Concentrations in Sedum praealtum DC

1979 ◽  
Vol 6 (4) ◽  
pp. 557 ◽  
Author(s):  
MH Spalding ◽  
DK Stumpf ◽  
MSB Ku ◽  
RH Burris ◽  
GE Edwards
Keyword(s):  
Malic Acid ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Dark Period ◽  
Stomatal Closure ◽  
Co2 Concentration ◽  
Co2 Exchange ◽  
C3 Plants ◽  
Cam Plants ◽  
Internal Co2

Internal CO2 and O2 concentrations in Sedum praealtum DC. were determined by gas chromatography of 200-�l gas samples. Day-night monitoring showed that internal CO2 varied from a high of approximately 4000 �l/l during periods of daytime stomatal closure to a low of 270-280 �l/l during the dark period (stomata open). Internal O2 concentrations varied from a high of approximately 26 % at midday to a low of 20.8 % during the dark period. The calculated internal O2/CO2 ratio varied about 12-15-fold from 50-60 near midday to approximately 750 during the dark period (ratio in normal air is roughly 600). Day-night patterns of CO2 exchange and malic acid concentration were typical for a plant with crassulacean acid metabolism (CAM). Influx of CO2 during the late light period was inhibited by O2, but dark CO2 influx was O2-insensitive. Gas samples taken near midday from several CAM plants all showed elevated internal CO2 and O2 concentrations. Ratios of O2/CO2 in these plants ranged from 81 in Sedum praealtum to 285 in Hoya carnosa. The highest internal O2 concentration observed was 41.5% in Kalanchoe gastonis-bonnieri. The high CO2 concentration in leaves of CAM plants during daytime stomatal closure should provide a near- saturating level of this substrate for photosynthesis. In comparison to C3 plants, the relatively low O2/CO2 ratio in the CAM leaf during malic acid decarboxylation should be favourable for photosynthesis and unfavourable for O2 inhibition of photosynthesis.

Nocturnal Uptake and Assimilation of Nitrogen Dioxide by C3 and CAM Plants

2005 ◽  
Vol 60 (3-4) ◽  
pp. 279-284 ◽  
Author(s):  
Misa Takahashi ◽  
Daisuke Konaka ◽  
Atsushi Sakamoto ◽  
Hiromichi Morikawa
Keyword(s):  
Mass Spectrometry ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Dry Weight ◽  
Hibiscus Cannabinus ◽  
C3 Plants ◽  
High Uptake ◽  
Cam Plants ◽  
Aloe Arborescens ◽  
Kjeldahl Nitrogen

Abstract In order to investigate nocturnal uptake and assimilation of NO2 by C3 and crassulacean acid metabolism (CAM) plants, they were fumigated with 4 μl I-115N-Iabeled nitrogen diox­ide (NO2) for 8 h. The amound of NO2 and assimilation of NO2by plants were determined by mass spectrometry and Kjeldahl-nitrogen based mass spectrometry, respectively. C3 plants such as kenaf (Hibiscus cannabinus), tobacco (Nicotiana tabacum) and ground cherry (Phy- salis alkekengi) showed a high uptake and assimilation during daytime as high as 1100 to 2700 ng N mg-1 dry weight. While tobacco and ground cherry strongly reduced uptake and assimilation of NO2 during nighttime, kenaf kept high nocturnal uptake and assimilation of NO2 as high as about 1500 ng N mg-1 dry weight. Stomatal conductance measurements indicated that there were no significant differences to account for the differences in the uptake of NO2 by tobacco and kenaf during nighttime. CAM plants such as Sedum sp., Kalanchoe blossfeldiana (kalanchoe) and Aloe arborescens exhibited nocturnal uptake and assimilation of NO2. However, the values of uptake and assimilation of NO2 both during daytime and nighttime was very low (at most about 500 ng N mg-1 dry weight) as compared with those of above mentioned C3 plants. The present findings indicate that kenaf is an efficient phytoremediator of NO2 both during daytime and nighttime.

How to tell the time: the regulation of phosphoenolpyruvate carboxylase in Crassulacean acid metabolism (CAM) plants

2003 ◽  
Vol 31 (3) ◽  
pp. 728-730 ◽  
Author(s):  
H.G. Nimmo
Keyword(s):  
Circadian Rhythms ◽  
Phosphoenolpyruvate Carboxylase ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Circadian Oscillator ◽  
Cam Plants ◽  
Reversible Phosphorylation ◽  
Circadian Expression ◽  
Phosphoenolpyruvate Carboxylase Kinase ◽  
Co2 Metabolism

Crassulacean acid metabolism (CAM) plants exhibit persistent circadian rhythms of CO2 metabolism. These rhythms are driven by changes in the flux through phosphoenolpyruvate carboxylase, which is regulated by reversible phosphorylation in response to a circadian oscillator. This article reviews progress in our understanding of the circadian expression of phosphoenolpyruvate carboxylase kinase.

scholarly journals Light-responsive expression atlas reveals the effects of light quality and intensity in Kalanchoë fedtschenkoi, a plant with crassulacean acid metabolism

GigaScience ◽  
2020 ◽  
Vol 9 (3) ◽  
Author(s):  
Jin Zhang ◽  
Rongbin Hu ◽  
Avinash Sreedasyam ◽  
Travis M Garcia ◽  
Anna Lipzen ◽  
...  
Keyword(s):  
Light Intensity ◽  
White Light ◽  
Crassulacean Acid Metabolism ◽  
Light Quality ◽  
Acid Metabolism ◽  
Easy Access ◽  
Cam Plants ◽  
A Genome ◽  
Acid Accumulation ◽  
Expression Atlas

Abstract Background Crassulacean acid metabolism (CAM), a specialized mode of photosynthesis, enables plant adaptation to water-limited environments and improves photosynthetic efficiency via an inorganic carbon-concentrating mechanism. Kalanchoë fedtschenkoi is an obligate CAM model featuring a relatively small genome and easy stable transformation. However, the molecular responses to light quality and intensity in CAM plants remain understudied. Results Here we present a genome-wide expression atlas of K. fedtschenkoi plants grown under 12 h/12 h photoperiod with different light quality (blue, red, far-red, white light) and intensity (0, 150, 440, and 1,000 μmol m–2 s–1) based on RNA sequencing performed for mature leaf samples collected at dawn (2 h before the light period) and dusk (2 h before the dark period). An eFP web browser was created for easy access of the gene expression data. Based on the expression atlas, we constructed a light-responsive co-expression network to reveal the potential regulatory relationships in K. fedtschenkoi. Measurements of leaf titratable acidity, soluble sugar, and starch turnover provided metabolic indicators of the magnitude of CAM under the different light treatments and were used to provide biological context for the expression dataset. Furthermore, CAM-related subnetworks were highlighted to showcase genes relevant to CAM pathway, circadian clock, and stomatal movement. In comparison with white light, monochrome blue/red/far-red light treatments repressed the expression of several CAM-related genes at dusk, along with a major reduction in acid accumulation. Increasing light intensity from an intermediate level (440 μmol m−2 s−1) of white light to a high light treatment (1,000 μmol m–2 s–1) increased expression of several genes involved in dark CO2 fixation and malate transport at dawn, along with an increase in organic acid accumulation. Conclusions This study provides a useful genomics resource for investigating the molecular mechanism underlying the light regulation of physiology and metabolism in CAM plants. Our results support the hypothesis that both light intensity and light quality can modulate the CAM pathway through regulation of CAM-related genes in K. fedtschenkoi.

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