Influence of CO2concentration on carbon concentrating mechanisms in cyanobacteria and green algae: a proteomic approach (original) (raw)
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Adapting from Low to High: An Update to CO2-Concentrating Mechanisms of Cyanobacteria and Microalgae
Plants
The intracellular accumulation of inorganic carbon (Ci) by microalgae and cyanobacteria under ambient atmospheric CO2 levels was first documented in the 80s of the 20th Century. Hence, a third variety of the CO2-concentrating mechanism (CCM), acting in aquatic photoautotrophs with the C3 photosynthetic pathway, was revealed in addition to the then-known schemes of CCM, functioning in CAM and C4 higher plants. Despite the low affinity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) of microalgae and cyanobacteria for the CO2 substrate and low CO2/O2 specificity, CCM allows them to perform efficient CO2 fixation in the reductive pentose phosphate (RPP) cycle. CCM is based on the coordinated operation of strategically located carbonic anhydrases and CO2/HCO3− uptake systems. This cooperation enables the intracellular accumulation of HCO3−, which is then employed to generate a high concentration of CO2 molecules in the vicinity of Rubisco’s active centers compensating up fo...
CO2 CONCENTRATING MECHANISMS IN ALGAE: Mechanisms, Environmental Modulation, and Evolution
Annual Review of Plant Biology, 2005
The evolution of organisms capable of oxygenic photosynthesis paralleled a long-term reduction in atmospheric CO 2 and the increase in O 2 . Consequently, the competition between O 2 and CO 2 for the active sites of RUBISCO became more and more restrictive to the rate of photosynthesis. In coping with this situation, many algae and some higher plants acquired mechanisms that use energy to increase the CO 2 concentrations (CO 2 concentrating mechanisms, CCMs) in the proximity of RUBISCO. A number of CCM variants are now found among the different groups of algae. Modulating the CCMs may be crucial in the energetic and nutritional budgets of a cell, and a multitude of environmental factors can exert regulatory effects on the expression of the CCM components. We discuss the diversity of CCMs, their evolutionary origins, and the role of the environment in CCM modulation. 99 Annu. Rev. Plant. Biol. 2005.56:99-131. Downloaded from arjournals.annualreviews.org by UNIVERSITY OF NEW MEXICO on 06/02/05. For personal use only.
2013
Cellular and molecular organization of CO2-concentrating mechanism (CCM) of cyanobacteria is reviewed. Primary processes of uptake, translocation and accumulation of inorganic carbon (Ci) in a cell, as well as concentrating of CO2 near the active site of RuBisCO, are presented as one of the specialized functions of the photoautotrophic cell equipped with the C3-type of photosynthesis. The existence of the ССМ expands our understanding of the photosynthetic Ci assimilation. It implies that the metabolic pathways preceding the involvement of Ci into organic products are the important regulatory elements of light and dark reactions of the cell that maintain its homeostasis and adaptation to CO2 limitation. Here we describe the organization of the CCM in cyanobacteria with a special focus on the CCM of relict halo-and alkaliphilic cyanobacteria of soda lakes. We also assess the role of the CCM at the levels of the organism, the biosphere, and evolution.
The capacity of algae to express CO2 concentrating mechanisms (CCMs) is regulated by environmental factors. Some of these factors, especially photon flux, can influence the instantaneous activity of a CCM without necessarily affecting gene expression or the capacity of the cell to transport inorganic carbon. Other environmental parameters, especially those causing changes in the availability of CO2 dissolved in the surrounding medium, act at a transcriptional level. In this review, the complex interactions between environmental factors in controlling CCM activity will be discussed, as will the ecological consequences of CCMs as they relate to the growth and ecological performance of algal cells in nature. We also consider the consequences of global climate change for the performance of algae with and without CCMs.
Journal of Plant Physiology, 2017
Cyanidioschyzon merolae (C. merolae) is an acidophilic red alga growing in a naturally low carbon dioxide (CO 2) environment. Although it uses a ribulose 1,5-bisphosphate carboxylase/oxygenase with high affinity for CO 2 , the survival of C. merolae relies on functional photorespiratory metabolism. In this study, we quantified the transcriptomic response of C. merolae to changes in CO 2 conditions. We found distinct changes upon shifts between CO 2 conditions, such as a concerted up-regulation of photorespiratory genes and responses to carbon starvation. We used the transcriptome data set to explore a hypothetical CO 2 concentrating mechanism in C. merolae, based on the assumption that photorespiratory genes and possible candidate genes involved in a CO 2 concentrating mechanism are co-expressed. A putative bicarbonate transport protein and two α-carbonic anhydrases were identified, which showed enhanced transcript levels under reduced CO 2 conditions. Genes encoding enzymes of a PEPCK-type C 4 pathway were co-regulated with the photorespiratory gene cluster. We propose a model of a hypothetical low CO 2 compensation mechanism in C. merolae integrating these low CO 2-inducible components.
Planta, 1992
Mass spectrometry was used to investigate the uptake of CO2 in Eremosphaera viridis DeBary. Upon illumination, cells preincubated at pH 7.5 with 100 ~tM dissolved inorganic carbon (DIC) rapidly depleted almost all the free CO2 from the medium. Rapid equilibrium between HCO~ and CO2 occurred upon addition of bovine carbonic anhydrase (CA) to the medium, showing that CO2 depletion resulted from a selective uptake of CO2 rather than an uptake of all inorganic carbon species. Glycolaldehyde (10 mM) completely inhibited CO2 fixation but had little effect on CO2 transport. Transfer of glycolaldehyde-treated cells to the dark caused a rapid effiux of COz from the unfixed intracellular DIC pool which was found to be at least three-to sixfold higher in concentration than that of the external medium. These results indicate that E. viridis actively transports COz against a concentration gradient. No external CA was detected in these cells either by potentiometric or mass-spectrometric assay. In the absence of external CA, the rate of photosynthetic 02 evolution in the pH range 7.5 to 8.0 did not exceed the calculated rate of CO2 supply, indicating a limited capacity for HCOS uptake in these cells. Electrophysiological measurements indicate that CO2 uptake is electrically silent and thus is not a consequence of H+-CO2 symport activity. Microsomal membranes isolated from Eremosphaera showed ATPase activity which was enhanced by CO2. These results indicate that active CO2 uptake is mediated by an ATPase. * To whom correspondence should be addressed; FAX : 1 (416) 736 5698 Abbreviations. BTP = 1,3-bis[tris(hydroximethyl)-methylamino]--propane; CA = carbonic anhydrase; Chl = chlorophyll ; DIC = dissolved inorganic carbon; [14C]DMO = 5,5-dimethyl-[2-t4C]-oxazdidine-2,4-dione; WA=Wilbur-Anderson units