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.

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.

Metabolic control of photosynthetic electron transport in crassulacean acid metabolism-induced Mesembryanthemum crystallinum

2002 ◽  
Vol 29 (6) ◽  
pp. 697 ◽  
Author(s):  
Mark Aurel Schöttler ◽  
Helmut Kirchhoff ◽  
Engelbert Weis ◽  
Katharina Siebke
Keyword(s):  
Electron Transport ◽  
Chlorophyll A ◽  
Chlorophyll A Fluorescence ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Electron Flux ◽  
Photosynthetic Electron Transport ◽  
Mesembryanthemum Crystallinum ◽  
Phase Iii ◽  
Linear Electron

This paper originates from a presentation at the IIIrd International Congress on Crassulacean Acid Metabolism, Cape Tribulation, Queensland, Australia, August 2001. We investigated photosynthetic electron transport in leaves of the facultative crassulacean acid metabolism (CAM) plant Mesembryanthemum crystallinum L. After CAM induction, electron transport exhibited variable redox kinetics during the diurnal CAM cycle. In CAM Phase IV, most of PSI (P700) and chlorophyll a fluorescence relaxed with a halftime of 20 ms after a saturating light pulse. This time-constant may reflect the overall linear electron flux from PSII to PSI in saturating light. Comparable relaxation kinetics were also determined for C3 plants. At the end of CAM Phase I and during Phase II, slow components (> 50% of signal amplitude) appeared in both P700 reduction and fluorescence relaxation. They displayed halftimes > 250 ms and > 1 s, suggesting a strong restriction of the linear electron flux from H2O to NADP. The appearance of the slow redox components was accompanied by a decrease in the Fv/Fm ratio of chlorophyll a fluorescence, suggesting a reversible detachment of light-harvesting complex (LHC) II from PSII. The slow redox fractions and the depression of Fv/Fm disappeared again in parallel to malate decarboxylation during CAM Phase III. We discuss a reversible downregulation of linear electron flux during CAM Phases II and III, due to a reversible deprivation of cytochrome-b6f complexes (cyt-bfs) and PSI from the linear system. In parallel, a redistribution of some LHCIIs could also occur. This could be an adaptive response to a reduced metabolic demand for NADPH due to a limited carbon flux through the Calvin cycle, resulting from low Rubisco activation. Furthermore, the cyt-bfs and PSIs deprived of linear electron transport could support cyclic electron flux to cover an increased ATP demand during gluconeogenesis in CAM Phase III.

Historical aspects and net CO2 uptake for cultivated Crassulacean acid metabolism plants in Mexico

2002 ◽  
Vol 140 (2) ◽  
pp. 133-142 ◽  
Author(s):  
PARK S NOBEL ◽  
EULOGIO PIMIENTA-BARRIOS ◽  
JULIA ZANUDO HERNANDEZ ◽  
BLANCA C RAMIREZ-HERNANDEZ
Keyword(s):  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Co2 Uptake ◽  
Historical Aspects ◽  
Net Co2 Uptake

Sucrose transport across the vacuolar membrane of Ananas comosus

2002 ◽  
Vol 29 (6) ◽  
pp. 717 ◽  
Author(s):  
Shelley R. McRae ◽  
John T. Christopher ◽  
J. Andrew C. Smith ◽  
Joseph A. M. Holtum
Keyword(s):  
Atpase Activity ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
External Medium ◽  
Soluble Sugars ◽  
Sugar Transport ◽  
Phase Iii ◽  
Ananas Comosus ◽  
Sucrose Uptake ◽  
Sucrose Transport

This paper originates from a presentation at the IIIrd International Congress on Crassulacean Acid Metabolism, Cape Tribulation, Queensland, Australia, August 2001. In Ananas comosus L. (Merr.) (pineapple), a widely cultivated bromeliad that exhibits crassulacean acid metabolism (CAM), much of the carbohydrate synthesized during the daytime appears to accumulate as soluble sugars in the vacuole. To investigate the mechanism of sugar transport into the vacuole, microsomal extracts were prepared from deacidifying leaves harvested during Phase III of the CAM cycle. The vesicle preparations exhibited features expected for a fraction highly enriched in vacuolar membranes (tonoplast), i.e. the ATPase activity of 16 ±�2�nkat mg-1 protein was inhibited 96% by 50 mm KNO3, an inhibitor of vacuolar ATPases, and was only 7% inhibited by 100μm NaN3 plus 100μm Na3VO4, inhibitors of mitochondrial and plasma membrane ATPases, respectively. Further, the microsomal ATPase activity showed a pH optimum between 7.0 and 8.0, typical of a vacuolar ATPase. When presented with Mg-ATP, vesicles established H+ gradients that could be maintained for at least 25 min. The vesicles were able to take up [14C]sucrose from an external medium. Sucrose uptake exhibited saturable kinetics with an apparent Km of 50 m sucrose and apparent Vmax of 171 ± 5 pkat mg-1 protein. Sucrose uptake was not dependent upon, nor stimulated by, Mg-ATP, suggesting that the mechanism of sucrose transport into the vacuole in A. comosus does not involve H+-coupled cotransport. However, the initial rates of sucrose uptake from the external medium were stimulated when vesicles were preloaded with sucrose. This trans-stimulation is consistent with characteristics expected for a sucrose uniporter capable of operating in an exchange mode. It is proposed that the accumulation of glucose and fructose in leaf vacuoles of Ananas during the light period involves at least two steps - transport of sucrose into the vacuole by a mechanism exhibiting characteristics of a sucrose uniporter, followed by cleavage of sucrose by a vacuolar acid invertase to form glucose and fructose.

Short-term plasticity of crassulacean acid metabolism expression in the epiphytic bromeliad Tillandsia usneoides

2002 ◽  
Vol 29 (6) ◽  
pp. 749 ◽  
Author(s):  
Richard Haslam ◽  
Anne Borland ◽  
Howard Griffiths
Keyword(s):  
Phase I ◽  
Carbon Balance ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Rapid Change ◽  
Co2 Uptake ◽  
Short Term Plasticity ◽  
Non Invasive ◽  
Tillandsia Usneoides

This paper originates from a presentation at the IIIrd International Congress on Crassulacean Acid Metabolism, Cape Tribulation, Queensland, Australia, August 2001. The regulation and flexibility of the crassulacean acid metabolism (CAM) pathway has been investigated in the 'extreme epiphyte' Tillandsia usneoides (L.). Submerging strands of T. usneoides under water, thereby inhibiting the supply of atmospheric CO2, allowed non-invasive in vivo manipulation of the supply of CO2 during the nocturnal Phase I of CAM. Once the plants were removed from submersion, T. usneoides maintained open stomata, and net CO2 uptake occurred throughout most of the photoperiod. Variability in the expression of CAM allowed T. usneoides to compensate for restricted CO2 availability through Phase I of CAM by adjusting gas exchange rates through the photoperiod and subsequent dark period to maintain a constant internal supply of CO2 in the light. Furthermore, T. usneoides demonstrated a gradual, rather than rapid, change in phosphoenolpyruvate carboxylase (PEPC) activation across the day-night cycle, such that PEPC and Rubisco appear to work in tandem in order to maintain carbon balance for this extreme atmospheric bromeliad.

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.

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