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The molecular evolution of C4 photosynthesis: opportunities for understanding and improving the world's most productive plants.
Niklaus, M, Kelly, S
Journal of experimental botany. 2019;(3):795-804
Abstract
C4 photosynthesis is a convergent evolutionary trait that enhances photosynthetic efficiency in a variety of environmental conditions. It has evolved repeatedly following a fall in atmospheric CO2 concentration such that there is up to a 30 million year difference in the amount of time that natural selection has had to improve C4 function between the oldest and youngest C4 lineages. This large difference in time, coupled with the phylogenetic distance between lineages, has resulted in a large disparity in anatomy, physiology, and biochemistry between extant C4 species. This review summarizes the myriad of molecular sequence changes that have been linked to the evolution of C4 photosynthesis. These range from single nucleotide changes to duplication of entire genes, and provide a roadmap for how natural selection has adapted enzymes and pathways for enhanced C4 function. Finally, this review discusses how this molecular diversity can provide opportunities for understanding and improving photosynthesis for multiple important C4 food, feed, and bioenergy crops.
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2.
Carbon Dioxide As a Standard of Care for Zero Contrast Interventions: When, Why and How?
Bisdas, T, Koutsias, S
Current pharmaceutical design. 2019;(44):4662-4666
Abstract
BACKGROUND Traditional contrast media containing iodine remain the gold standard for vessel visualization during endovascular procedures. On the other hand, their use has several side effects and implications and may cause contrast medium-induced nephropathy. Carbon dioxide (CO2) angiography is an old alternative technique used only for critical patients in order to prevent kidney damages or allergic reactions. Zero contrast procedure: The availability of automated CO2 injectors has led to an increase in the use of CO2 angiography, providing an option for zero contrast interventions, preserving patient renal function and saving costs for the hospital facility. Taking advantage of the properties of CO2 gas, it is possible to improve the performance of some complex procedures such as atherectomy and the detection of type II endoleaks after EVARs. However, a learning curve is needed to get good imaging, and learn about the qualities and limitations of the technique. CONCLUSIONS The use of automatic delivery systems for CO2 angiography appears to be a good choice for the use of CO2 as the first imaging option. The standardization of injection protocols and the extensive use of this technique could lead to significant benefits both for the patient's prospects and health facilities.
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3.
Biological CO2 mitigation by microalgae: technological trends, future prospects and challenges.
de Morais, MG, de Morais, EG, Duarte, JH, Deamici, KM, Mitchell, BG, Costa, JAV
World journal of microbiology & biotechnology. 2019;(5):78
Abstract
The increase in the CO2 concentration in the Earth's atmosphere has been a topic of worldwide concern since anthropogenic emissions of greenhouse gases began increasing considerably during the industrial period. The effects of these mass emissions are probably the main cause of global warming, which has been observed over recent decades. Among the various techniques of CO2 capture, microalgal biofixation by photosynthesis is considered a promising technology due to the efficiency of these microorganisms in converting this gas into organic compounds through its use as a nutrient in the culture medium. Over the years, several research centers have developed studies on this subject, which have focused on mainly the development of bioreactors, the growth conditions that increase the efficiency of the process and the production of biomass with applicability in several areas. The biological mitigation of CO2 by microalgae has many advantages, including reductions in the concentration of an industrially sourced greenhouse gas and the energy or food obtained from the produced photosynthetic biomass. This versatility allows for the cultivation of economically useful biomass while reducing the environmental impacts of industrial facilities. In this context, this mini-review aims to discuss new technologies and strategies along with the main challenges and future prospects in the field and the ecological and economic impacts of CO2 biofixation by microalgae.
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4.
Effects of water deficit stress on agronomic and physiological responses of rice and greenhouse gas emission from rice soil under elevated atmospheric CO2.
Kumar, A, Nayak, AK, Das, BS, Panigrahi, N, Dasgupta, P, Mohanty, S, Kumar, U, Panneerselvam, P, Pathak, H
The Science of the total environment. 2019;(Pt 2):2032-2050
Abstract
Rice is the foremost staple food in the world, safeguarding the global food and nutritional security. Rise in atmospheric carbon dioxide (CO2) and water deficits are threatening global rice productivity and sustainability. Under real field conditions these climatic factors often interact with each other resulting in impacts that are remarkably different compared to individual factor exposure. Rice soils exposed to drought and elevated CO2 (eCO2) alters the biomass, diversity and activity of soil microorganisms affecting greenhouse gas (GHG) emission dynamics. In this review we have discussed the impacts of eCO2 and water deficit on agronomic, biochemical and physiological responses of rice and GHGs emissions from rice soils. Drought usually results in oxidative stress due to stomatal closure, dry weight reduction, formation of reactive oxygen species, decrease in relative water content and increase in electrolyte leakage at almost all growth and developmental phases of rice. Elevated atmospheric CO2 concentration reduces the negative effects of drought by improving plant water relations, reducing stomatal opening, decreasing transpiration, increasing canopy photosynthesis, shortening crop growth period and increasing the antioxidant metabolite activities in rice. Increased scientific understanding of the effects of drought and eCO2 on rice agronomy, physiology and GHG emission dynamics of rice soil is essential for devising adaptation options. Integration of novel agronomic practices viz., crop establishment methods and alternate cropping systems with improved water and nutrient management are important steps to help rice farmers cope with drought and eCO2. The review summarizes future research needs for ensuring sustained global food security under future warmer, drier and high CO2 conditions.
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5.
Microbially induced calcium carbonate precipitation: a widespread phenomenon in the biological world.
Seifan, M, Berenjian, A
Applied microbiology and biotechnology. 2019;(12):4693-4708
Abstract
Biodeposition of minerals is a widespread phenomenon in the biological world and is mediated by bacteria, fungi, protists, and plants. Calcium carbonate is one of those minerals that naturally precipitate as a by-product of microbial metabolic activities. Over recent years, microbially induced calcium carbonate precipitation (MICP) has been proposed as a potent solution to address many environmental and engineering issues. However, for being a viable alternative to conventional techniques as well as being financially and industrially competitive, various challenges need to be overcome. In this review, the detailed metabolic pathways, including ammonification of amino acids, dissimilatory reduction of nitrate, and urea degradation (ureolysis), along with the potent bacteria and the favorable conditions for precipitation of calcium carbonate, are explained. Moreover, this review highlights the potential environmental and engineering applications of MICP, including restoration of stones and concrete, improvement of soil properties, sand consolidation, bioremediation of contaminants, and carbon dioxide sequestration. The key research and development questions necessary for near future large-scale applications of this innovative technology are also discussed.
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6.
Exploring the Relationship between Crassulacean Acid Metabolism (CAM) and Mineral Nutrition with a Special Focus on Nitrogen.
Pereira, PN, Cushman, JC
International journal of molecular sciences. 2019;(18)
Abstract
Crassulacean acid metabolism (CAM) is characterized by nocturnal CO2 uptake and concentration, reduced photorespiration, and increased water-use efficiency (WUE) when compared to C3 and C4 plants. Plants can perform different types of CAM and the magnitude and duration of CAM expression can change based upon several abiotic conditions, including nutrient availability. Here, we summarize the abiotic factors that are associated with an increase in CAM expression with an emphasis on the relationship between CAM photosynthesis and nutrient availability, with particular focus on nitrogen, phosphorus, potassium, and calcium. Additionally, we examine nitrogen uptake and assimilation as this macronutrient has received the greatest amount of attention in studies using CAM species. We also discuss the preference of CAM species for different organic and inorganic sources of nitrogen, including nitrate, ammonium, glutamine, and urea. Lastly, we make recommendations for future research areas to better understand the relationship between macronutrients and CAM and how their interaction might improve nutrient and water-use efficiency in order to increase the growth and yield of CAM plants, especially CAM crops that may become increasingly important as global climate change continues.
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7.
Upper ocean oxygenation, evolution of RuBisCO and the Phanerozoic succession of phytoplankton.
Rickaby, REM, Eason Hubbard, MR
Free radical biology & medicine. 2019;:295-304
Abstract
Evidence is compiled to demonstrate a redox scale within Earth's photosynthesisers that correlates the specificity of their RuBisCO with organismal metabolic tolerance to anoxia, and ecological selection by dissolved O2/CO2 and nutrients. The Form 1B RuBisCO found in the chlorophyte green algae, has a poor selectivity between the two dissolved substrates, O2 and CO2, at the active site. This enzyme appears adapted to lower O2/CO2 ratios, or more "anoxic" conditions and therefore requires additional energetic or nutrient investment in a carbon concentrating mechanism (CCM) to boost the intracellular CO2/O2 ratio and maintain competitive carboxylation rates under increasingly high O2/CO2 conditions in the environment. By contrast the coccolithophores and diatoms evolved containing the more selective Rhodophyte Form 1D RuBisCO, better adapted to a higher O2/CO2 ratio, or more oxic conditions. This Form 1D RuBisCO requires lesser energetic or nutrient investment in a CCM to attain high carboxylation rates under environmentally high O2/CO2 ratios. Such a physiological relationship may underpin the succession of phytoplankton in the Phanerozoic oceans: the coccolithophores and diatoms took over the oceanic realm from the incumbent cyanobacteria and green algae when the upper ocean became persistently oxygenated, alkaline and more oligotrophic. The facultatively anaerobic green algae, able to tolerate the anoxic conditions of the water column and a periodically inundated soil, were better poised to adapt to the fluctuating anoxia associated with periods of submergence and emergence and transition onto the land. The induction of a CCM may exert a natural limit to the improvement of RuBisCO efficiency over Earth history. Rubisco specificity appears to adapt on the timescale of ∼100 Myrs. So persistent elevation of CO2/O2 ratios in the intracellular environment around the enzyme, may induce a relaxation in RuBisCO selectivity for CO2 relative to O2. The most efficient RuBisCO for net carboxylation is likely to be found in CCM-lacking algae that have been exposed to hyperoxic conditions for at least 100 Myrs, such as intertidal brown seaweeds.
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8.
Current and possible approaches for improving photosynthetic efficiency.
Éva, C, Oszvald, M, Tamás, L
Plant science : an international journal of experimental plant biology. 2019;:433-440
Abstract
One of the most important tasks laying ahead today's biotechnology is to improve crop productivity with the aim of meeting increased food and energy demands of humankind. Plant productivity depends on many genetic factors, including life cycle, harvest index, stress tolerance and photosynthetic activity. Many approaches were already tested or suggested to improve either. Limitations of photosynthesis have also been uncovered and efforts been taken to increase its efficiency. Examples include decreasing photosynthetic antennae size, increasing the photosynthetically available light spectrum, countering oxygenase activity of Rubisco by implementing C4 photosynthesis to C3 plants and altering source to sink transport of metabolites. A natural and effective photosynthetic adaptation, the sugar alcohol metabolism got however remarkably little attention in the last years, despite being comparably efficient as C4, and can be considered easier to introduce to new species. We also propose root to shoot carbon-dioxide transport as a means to improve photosynthetic performance and drought tolerance at the same time. Different suggestions and successful examples are covered here for improving plant photosynthesis as well as novel perspectives are presented for future research.
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9.
Rising Atmospheric CO2 Lowers Concentrations of Plant Carotenoids Essential to Human Health: A Meta-Analysis.
Loladze, I, Nolan, JM, Ziska, LH, Knobbe, AR
Molecular nutrition & food research. 2019;(15):e1801047
Abstract
Plant and human tissues (e.g., leaves, retina) share the need for carotenoids to protect against light-induced and other oxidative stresses. While plants synthesize carotenoids de novo, humans must obtain them primarily through plant-based foods. In plants, elevated levels of atmospheric carbon dioxide (eCO2 ) decrease the concentrations of essential minerals, including magnesium and zinc (essential for brain and eye health), but the overall effect of globally rising CO2 levels on carotenoids is unknown. Here, investigation is sought on how eCO2 affects carotenoids in plants. A meta-analysis of 1026 experimental observations from 37 studies shows that eCO2 decreases plant carotenoid concentrations by 15% (95% CI: -26% to -6%). The meta-analysis of available gene expression data for Arabidopsis thaliana points to a potential CO2 -induced downregulation of carotenoid biosynthesis (Log2 fold-change -13%, 95% CI: -17% to -9%). Some other stoichiometric and biochemical mechanisms related to CO2 -induced changes in carotenoids are also highlighted. While overall eCO2 decreases carotenoid concentrations, individual CO2 studies report variable responses, including increases in carotenoid levels, especially in abiotically stressed plants. The initial assessment raises a novel question about the potential effects of rising CO2 on human health through its global effect on plant carotenoids.
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10.
Net photosynthetic CO2 assimilation: more than just CO2 and O2 reduction cycles.
Tcherkez, G, Limami, AM
The New phytologist. 2019;(2):520-529
Abstract
Net photosynthetic assimilation in C3 plants is mostly viewed as a simple balance between CO2 fixation by Rubisco-catalyzed carboxylation and CO2 production by photorespiration (and to a lower extent, by day respiration) that can be easily manipulated during gas exchange experiments using the CO2 : O2 ratio of the environment. However, it now becomes clear that it is not so simple, because the photosynthetic response to gaseous conditions involves 'ancillary' metabolisms, even in the short-term. That is, carbon and nitrogen utilization by pathways other than the Calvin cycle and the photorespiratory cycle, as well as rapid signaling events, can influence the observed rate of net photosynthesis. The potential impact of such ancillary metabolisms is assessed as well as how it must be taken into account to avoid misinterpretation of photosynthetic CO2 response curves or low O2 effects in C3 leaves.