1
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Ludwig M, Hartwell J, Raines CA, Simkin AJ. The Calvin-Benson-Bassham cycle in C 4 and Crassulacean acid metabolism species. Semin Cell Dev Biol 2024; 155:10-22. [PMID: 37544777 DOI: 10.1016/j.semcdb.2023.07.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 07/03/2023] [Accepted: 07/25/2023] [Indexed: 08/08/2023]
Abstract
The Calvin-Benson-Bassham (CBB) cycle is the ancestral CO2 assimilation pathway and is found in all photosynthetic organisms. Biochemical extensions to the CBB cycle have evolved that allow the resulting pathways to act as CO2 concentrating mechanisms, either spatially in the case of C4 photosynthesis or temporally in the case of Crassulacean acid metabolism (CAM). While the biochemical steps in the C4 and CAM pathways are known, questions remain on their integration and regulation with CBB cycle activity. The application of omic and transgenic technologies is providing a more complete understanding of the biochemistry of C4 and CAM species and will also provide insight into the CBB cycle in these plants. As the global population increases, new solutions are required to increase crop yields and meet demands for food and other bioproducts. Previous work in C3 species has shown that increasing carbon assimilation through genetic manipulation of the CBB cycle can increase biomass and yield. There may also be options to improve photosynthesis in species using C4 photosynthesis and CAM through manipulation of the CBB cycle in these plants. This is an underexplored strategy and requires more basic knowledge of CBB cycle operation in these species to enable approaches for increased productivity.
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Affiliation(s)
- Martha Ludwig
- School of Molecular Sciences, University of Western Australia, Perth, Western Australia, Australia.
| | - James Hartwell
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | | | - Andrew J Simkin
- University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK; School of Biosciences, University of Kent, Canterbury CT2 7NJ, UK
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2
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Gilman IS, Smith JAC, Holtum JAM, Sage RF, Silvera K, Winter K, Edwards EJ. The CAM lineages of planet Earth. ANNALS OF BOTANY 2023; 132:627-654. [PMID: 37698538 PMCID: PMC10799995 DOI: 10.1093/aob/mcad135] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 01/09/2023] [Accepted: 09/11/2023] [Indexed: 09/13/2023]
Abstract
BACKGROUND AND SCOPE The growth of experimental studies of crassulacean acid metabolism (CAM) in diverse plant clades, coupled with recent advances in molecular systematics, presents an opportunity to re-assess the phylogenetic distribution and diversity of species capable of CAM. It has been more than two decades since the last comprehensive lists of CAM taxa were published, and an updated survey of the occurrence and distribution of CAM taxa is needed to facilitate and guide future CAM research. We aimed to survey the phylogenetic distribution of these taxa, their diverse morphology, physiology and ecology, and the likely number of evolutionary origins of CAM based on currently known lineages. RESULTS AND CONCLUSIONS We found direct evidence (in the form of experimental or field observations of gas exchange, day-night fluctuations in organic acids, carbon isotope ratios and enzymatic activity) for CAM in 370 genera of vascular plants, representing 38 families. Further assumptions about the frequency of CAM species in CAM clades and the distribution of CAM in the Cactaceae and Crassulaceae bring the currently estimated number of CAM-capable species to nearly 7 % of all vascular plants. The phylogenetic distribution of these taxa suggests a minimum of 66 independent origins of CAM in vascular plants, possibly with dozens more. To achieve further insight into CAM origins, there is a need for more extensive and systematic surveys of previously unstudied lineages, particularly in living material to identify low-level CAM activity, and for denser sampling to increase phylogenetic resolution in CAM-evolving clades. This should allow further progress in understanding the functional significance of this pathway by integration with studies on the evolution and genomics of CAM in its many forms.
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Affiliation(s)
- Ian S Gilman
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
| | | | - Joseph A M Holtum
- College of Science and Engineering, James Cook University, Townsville, Queensland, Australia
| | - Rowan F Sage
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
| | - Katia Silvera
- Smithsonian Tropical Research Institute, Balboa, Ancón, Panama
- Department of Botany & Plant Sciences, University of California, Riverside, CA, USA
| | - Klaus Winter
- Smithsonian Tropical Research Institute, Balboa, Ancón, Panama
| | - Erika J Edwards
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
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3
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Chomthong M, Griffiths H. Prospects and perspectives: inferring physiological and regulatory targets for CAM from molecular and modelling approaches. ANNALS OF BOTANY 2023; 132:583-596. [PMID: 37742290 PMCID: PMC10799989 DOI: 10.1093/aob/mcad142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 08/26/2023] [Accepted: 09/21/2023] [Indexed: 09/26/2023]
Abstract
BACKGROUND AND SCOPE This review summarizes recent advances in our understanding of Crassulacean Acid Metabolism (CAM) by integrating evolutionary, ecological, physiological, metabolic and molecular perspectives. A number of key control loops which moderate the expression of CAM phases, and their metabolic and molecular control, are explored. These include nocturnal stomatal opening, activation of phosphoenolpyruvate carboxylase by a specific protein kinase, interactions with circadian clock control, as well as daytime decarboxylation and activation of Rubisco. The vacuolar storage and release of malic acid and the interplay between the supply and demand for carbohydrate reserves are also key metabolic control points. FUTURE OPPORTUNITIES We identify open questions and opportunities, with experimentation informed by top-down molecular modelling approaches allied with bottom-up mechanistic modelling systems. For example, mining transcriptomic datasets using high-speed systems approaches will help to identify targets for future genetic manipulation experiments to define the regulation of CAM (whether circadian or metabolic control). We emphasize that inferences arising from computational approaches or advanced nuclear sequencing techniques can identify potential genes and transcription factors as regulatory targets. However, these outputs then require systematic evaluation, using genetic manipulation in key model organisms over a developmental progression, combining gene silencing and metabolic flux analysis and modelling to define functionality across the CAM day-night cycle. From an evolutionary perspective, the origins and function of CAM succulents and responses to water deficits are set against the mesophyll and hydraulic limitations imposed by cell and tissue succulence in contrasting morphological lineages. We highlight the interplay between traits across shoots (3D vein density, mesophyll conductance and cell shrinkage) and roots (xylem embolism and segmentation). Thus, molecular, biophysical and biochemical processes help to curtail water losses and exploit rapid rehydration during restorative rain events. In the face of a changing climate, we hope such approaches will stimulate opportunities for future research.
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Affiliation(s)
- Methawi Chomthong
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Howard Griffiths
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
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4
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Santos MG, Davey PA, Hofmann TA, Borland A, Hartwell J, Lawson T. Stomatal Responses to Light, CO 2, and Mesophyll Tissue in Vicia faba and Kalanchoë fedtschenkoi. FRONTIERS IN PLANT SCIENCE 2021; 12:740534. [PMID: 34777422 PMCID: PMC8579043 DOI: 10.3389/fpls.2021.740534] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 09/22/2021] [Indexed: 05/14/2023]
Abstract
The responses of stomatal aperture to light intensity and CO2 concentration were studied in both Vicia faba (C3) and Kalanchoë fedtschenkoi (Crassulacean acid metabolism; CAM), in material sampled from both light and dark periods. Direct comparison was made between intact leaf segments, epidermises grafted onto exposed mesophyll, and isolated epidermal peels, including transplantations between species and between diel periods. We reported the stomatal opening in response to darkness in isolated CAM peels from the light period, but not from the dark. Furthermore, we showed that C3 mesophyll has stimulated CAM stomata in transplanted peels to behave as C3 in response to light and CO2. By using peels and mesophyll from plants sampled in the dark and the light period, we provided clear evidence that CAM stomata behaved differently from C3. This might be linked to stored metabolites/ions and signalling pathway components within the guard cells, and/or a mesophyll-derived signal. Overall, our results provided evidence for both the involvement of guard cell metabolism and mesophyll signals in stomatal responses in both C3 and CAM species.
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Affiliation(s)
- Mauro G. Santos
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, United Kingdom
| | - Phillip A. Davey
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, United Kingdom
| | | | - Anne Borland
- School of Natural and Environmental Sciences, Devonshire Building, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - James Hartwell
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Tracy Lawson
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, United Kingdom
- *Correspondence: Tracy Lawson
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5
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Guan Q, Tan B, Kelley TM, Tian J, Chen S. Physiological Changes in Mesembryanthemum crystallinum During the C 3 to CAM Transition Induced by Salt Stress. FRONTIERS IN PLANT SCIENCE 2020; 11:283. [PMID: 32256510 PMCID: PMC7090145 DOI: 10.3389/fpls.2020.00283] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 02/25/2020] [Indexed: 05/27/2023]
Abstract
Salt stress impedes plant growth and development, and leads to yield loss. Recently, a halophyte species Mesembryanthemum crystallinum has become a model to study plant photosynthetic responses to salt stress. It has an adaptive mechanism of shifting from C3 photosynthesis to crassulacean acid metabolism (CAM) photosynthesis under stresses, which greatly enhances water usage efficiency and stress tolerance. In this study, we focused on investigating the morphological and physiological changes [e.g., leaf area, stomatal movement behavior, gas exchange, leaf succulence, and relative water content (RWC)] of M. crystallinum during the C3 to CAM photosynthetic transition under salt stress. Our results showed that in M. crystallinum seedlings, CAM photosynthesis was initiated after 6 days of salt treatment, the transition takes place within a 3-day period, and plants became mostly CAM in 2 weeks. This result defined the transition period of a facultative CAM plant, laid a foundation for future studies on identifying the molecular switches responsible for the transition from C3 to CAM, and contributed to the ultimate goal of engineering CAM characteristics into C3 crops.
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Affiliation(s)
- Qijie Guan
- College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China
- Department of Biology, Genetics Institute, Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL, United States
| | - Bowen Tan
- Department of Biology, University of Florida, Gainesville, FL, United States
| | - Theresa M. Kelley
- Department of Biology, Genetics Institute, Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL, United States
| | - Jingkui Tian
- College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China
- Zhejiang-Malaysia Joint Research Center for Traditional Medicine, Zhejiang University, Hangzhou, China
| | - Sixue Chen
- Department of Biology, Genetics Institute, Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL, United States
- Proteomics and Mass Spectrometry, Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL, United States
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6
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Cousins AB, Mullendore DL, Sonawane BV. Recent developments in mesophyll conductance in C3, C4, and crassulacean acid metabolism plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 101:816-830. [PMID: 31960507 DOI: 10.1111/tpj.14664] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Accepted: 12/19/2019] [Indexed: 05/24/2023]
Abstract
The conductance of carbon dioxide (CO2 ) from the substomatal cavities to the initial sites of CO2 fixation (gm ) can significantly reduce the availability of CO2 for photosynthesis. There have been many recent reviews on: (i) the importance of gm for accurately modelling net rates of CO2 assimilation, (ii) on how leaf biochemical and anatomical factors influence gm , (iii) the technical limitation of estimating gm , which cannot be directly measured, and (iv) how gm responds to long- and short-term changes in growth and measurement environmental conditions. Therefore, this review will highlight these previous publications but will attempt not to repeat what has already been published. We will instead initially focus on the recent developments on the two-resistance model of gm that describe the potential of photorespiratory and respiratory CO2 released within the mitochondria to diffuse directly into both the chloroplast and the cytosol. Subsequently, we summarize recent developments in the three-dimensional (3-D) reaction-diffusion models and 3-D image analysis that are providing new insights into how the complex structure and organization of the leaf influences gm . Finally, because most of the reviews and literature on gm have traditionally focused on C3 plants we review in the final sections some of the recent developments, current understanding and measurement techniques of gm in C4 and crassulacean acid metabolism (CAM) plants. These plants have both specialized leaf anatomy and either a spatially or temporally separated CO2 concentrating mechanisms (C4 and CAM, respectively) that influence how we interpret and estimate gm compared with a C3 plants.
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Affiliation(s)
- Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Daniel L Mullendore
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Balasaheb V Sonawane
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
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7
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Chomthong M, Griffiths H. Model approaches to advance crassulacean acid metabolism system integration. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 101:951-963. [PMID: 31943394 DOI: 10.1111/tpj.14691] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 01/02/2020] [Indexed: 06/10/2023]
Abstract
This review summarises recent progress in understanding crassulacean acid metabolism (CAM) systems and the integration of internal and external stimuli to maximise water-use efficiency. Complex CAM traits have been reduced to their minimum and captured as computational models, which can now be refined using recently available data from transgenic manipulations and large-scale omics studies. We identify three key areas in which an appropriate choice of modelling tool could help capture relevant comparative molecular data to address the evolutionary drivers and plasticity of CAM. One focus is to identify the environmental and internal signals that drive inverse stomatal opening at night. Secondly, it is important to identify the regulatory processes required to orchestrate the diel pattern of carbon fluxes within mesophyll layers. Finally, the limitations imposed by contrasting succulent systems and associated hydraulic conductance components should be compared in the context of water-use and evolutionary strategies. While network analysis of transcriptomic data can provide insights via co-expression modules and hubs, alternative forms of computational modelling should be used iteratively to define the physiological significance of key components and informing targeted functional gene manipulation studies. We conclude that the resultant improvements of bottom-up, mechanistic modelling systems can enhance progress towards capturing the physiological controls for phylogenetically diverse CAM systems in the face of the recent surge of information in this omics era.
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Affiliation(s)
- Methawi Chomthong
- Department of Plant Sciences, University of Cambridge, Downing street, Cambridge, CB2 3EA, UK
| | - Howard Griffiths
- Department of Plant Sciences, University of Cambridge, Downing street, Cambridge, CB2 3EA, UK
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8
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Chen LY, Xin Y, Wai CM, Liu J, Ming R. The role of cis-elements in the evolution of crassulacean acid metabolism photosynthesis. HORTICULTURE RESEARCH 2020; 7:5. [PMID: 31908808 PMCID: PMC6938490 DOI: 10.1038/s41438-019-0229-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Revised: 12/01/2019] [Accepted: 12/04/2019] [Indexed: 05/30/2023]
Abstract
Crassulacean acid metabolism (CAM) photosynthesis is an innovation of carbon concentrating mechanism that is characterized by nocturnal CO2 fixation. Recent progresses in genomics, transcriptomics, proteomics, and metabolomics of CAM species yielded new knowledge and abundant genomic resources. In this review, we will discuss the pattern of cis-elements in stomata movement-related genes and CAM CO2 fixation genes, and analyze the expression dynamic of CAM related genes in green leaf tissues. We propose that CAM photosynthesis evolved through the re-organization of existing enzymes and associated membrane transporters in central metabolism and stomatal movement-related genes, at least in part by selection of existing circadian clock cis-regulatory elements in their promoter regions. Better understanding of CAM evolution will help us to design crops that can thrive in arid or semi-arid regions, which are likely to expand due to global climate change.
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Affiliation(s)
- Li-Yu Chen
- FAFU and UIUC Joint Center for Genomics and Biotechnology, Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Key Laboratory of Genetics, Breeding and Multiple Utilization of Crops, Ministry of Education, Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian China
| | - Yinghui Xin
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801 USA
| | - Ching Man Wai
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801 USA
| | - Juan Liu
- FAFU and UIUC Joint Center for Genomics and Biotechnology, Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Key Laboratory of Genetics, Breeding and Multiple Utilization of Crops, Ministry of Education, Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian China
| | - Ray Ming
- FAFU and UIUC Joint Center for Genomics and Biotechnology, Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Key Laboratory of Genetics, Breeding and Multiple Utilization of Crops, Ministry of Education, Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian China
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801 USA
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9
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Giuliani R, Karki S, Covshoff S, Lin HC, Coe RA, Koteyeva NK, Evans MA, Quick WP, von Caemmerer S, Furbank RT, Hibberd JM, Edwards GE, Cousins AB. Transgenic maize phosphoenolpyruvate carboxylase alters leaf-atmosphere CO 2 and 13CO 2 exchanges in Oryza sativa. PHOTOSYNTHESIS RESEARCH 2019; 142:153-167. [PMID: 31325077 PMCID: PMC6848035 DOI: 10.1007/s11120-019-00655-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 06/11/2019] [Indexed: 05/07/2023]
Abstract
The engineering process of C4 photosynthesis into C3 plants requires an increased activity of phosphoenolpyruvate carboxylase (PEPC) in the cytosol of leaf mesophyll cells. The literature varies on the physiological effect of transgenic maize (Zea mays) PEPC (ZmPEPC) leaf expression in Oryza sativa (rice). Therefore, to address this issue, leaf-atmosphere CO2 and 13CO2 exchanges were measured, both in the light (at atmospheric O2 partial pressure of 1.84 kPa and at different CO2 levels) and in the dark, in transgenic rice expressing ZmPEPC and wild-type (WT) plants. The in vitro PEPC activity was 25 times higher in the PEPC overexpressing (PEPC-OE) plants (~20% of maize) compared to the negligible activity in WT. In the PEPC-OE plants, the estimated fraction of carboxylation by PEPC (β) was ~6% and leaf net biochemical discrimination against 13CO2[Formula: see text] was ~ 2‰ lower than in WT. However, there were no differences in leaf net CO2 assimilation rates (A) between genotypes, while the leaf dark respiration rates (Rd) over three hours after light-dark transition were enhanced (~ 30%) and with a higher 13C composition [Formula: see text] in the PEPC-OE plants compared to WT. These data indicate that ZmPEPC in the PEPC-OE rice plants contributes to leaf carbon metabolism in both the light and in the dark. However, there are some factors, potentially posttranslational regulation and PEP availability, which reduce ZmPEPC activity in vivo.
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Affiliation(s)
- Rita Giuliani
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Shanta Karki
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
| | - Sarah Covshoff
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Hsiang-Chun Lin
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
| | - Robert A Coe
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
| | - Nuria K Koteyeva
- Laboratory of Anatomy and Morphology, V.L. Komarov Botanical Institute of the Russian Academy of Sciences, Prof. Popov Street 2, St. Petersburg, Russia, 197376
| | - Marc A Evans
- Department of Mathematics and Statistics, Washington State University, Pullman, WA, 99164-3113, USA
| | - W Paul Quick
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK
| | - Susanne von Caemmerer
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT, 0200, Australia
| | - Robert T Furbank
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT, 0200, Australia
| | - Julian M Hibberd
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Gerald E Edwards
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Asaph B Cousins
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA.
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10
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Niechayev NA, Pereira PN, Cushman JC. Understanding trait diversity associated with crassulacean acid metabolism (CAM). CURRENT OPINION IN PLANT BIOLOGY 2019; 49:74-85. [PMID: 31284077 DOI: 10.1016/j.pbi.2019.06.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 05/30/2019] [Accepted: 06/04/2019] [Indexed: 06/09/2023]
Abstract
Crassulacean acid metabolism (CAM) is a specialized mode of photosynthesis that exploits a temporal CO2 pump with nocturnal CO2 uptake and concentration to reduce photorespiration, improve water-use efficiency (WUE), and optimize the adaptability of plants to climates with seasonal or intermittent water limitations. CAM plants display a plastic continuum in the extent to which species engage in net nocturnal CO2 uptake that ranges from 0 to 100%. CAM plants also display diverse enzyme and organic acid and carbohydrate storage systems, which likely reflect the multiple, independent evolutionary origins of CAM. CAM is often accompanied by a diverse set of anatomical traits, such as tissue succulence and water-storage and water-capture strategies to attenuate drought. Other co-adaptive traits, such as thick cuticles, epicuticular wax, low stomatal density, high stomatal responsiveness, and shallow rectifier-like roots limit water loss under conditions of water deficit. Recommendations for future research efforts to better explore and understand the diversity of traits associated with CAM and CAM Biodesign efforts are presented.
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Affiliation(s)
- Nicholas A Niechayev
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Reno, NV 89557-0330, United States
| | - Paula N Pereira
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Reno, NV 89557-0330, United States
| | - John C Cushman
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Reno, NV 89557-0330, United States.
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11
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Cheng Y, He D, He J, Niu G, Gao R. Effect of Light/Dark Cycle on Photosynthetic Pathway Switching and CO 2 Absorption in Two Dendrobium Species. FRONTIERS IN PLANT SCIENCE 2019; 10:659. [PMID: 31178881 PMCID: PMC6538687 DOI: 10.3389/fpls.2019.00659] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 05/02/2019] [Indexed: 05/26/2023]
Abstract
Many Dendrobium species are both ornamental and medicinal plants in China. Several wild species have been exploited to near extinction, and facility cultivation has become an important way to meet the great market demand. Most Dendrobium species have evolved into crassulacean acid metabolism (CAM) pathways in adapting to harsh epiphytic environment, leading to low daily net CO2 absorption. Photosynthetic pathways of many facultative CAM plants are regulated by various environmental factors. Light/dark cycle plays an important role in regulating the photosynthetic pathway of several CAM species. The aims of this study were to investigate whether the photosynthetic pathway of Dendrobium species could be regulated between C3 and CAM by changing light/dark cycles and the daily net CO2 absorption could be enhanced by shortening light/dark cycle. In this study, net CO2 exchange rates of D. officinale and D. primulinum were monitored continuously during two different light/dark cycles conversion compared to Kalanchoe daigremontiana as an obligate CAM plant. The net CO2 exchange pattern and stomatal behavior of D. officinale and D. primulinum were switched from CAM to C3-like by changing the light/dark cycle from 12/12 h to 4/4 h. However, this switching was not completely reversible. Compared to the original 12/12 h light/dark cycle, the dark, light, and daily net CO2 exchange amount of D. officinale were significantly increased after the light/dark cycle was changed from 4/4 h to 12/12 h, but those in D. primulinum was opposite and those in K. daigremontiana was not affected. Daily net CO2 exchange amount of D. officinale increased by 47% after the light/dark cycle was changed from 12/12 h to 4/4 h, due to the sharp increase of light net CO2 exchange amount. However, the large decrease of dark net CO2 exchange amount could not be offset by increased light net CO2 exchange amount, leading to reduced daily net CO2 exchange amount of D. primulinum. In conclusion, the 4/4 h light/dark cycle can induce the photosynthetic pathway of D. officinale and D. primulinum to C3-like, and improve the daily CO2 absorption of D. officinale.
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Affiliation(s)
- Yongsan Cheng
- Key Laboratory Agricultural Engineering in Structure and Environment, Ministry of Agriculture and Rural Affairs, China Agricultural University, Beijing, China
| | - Dongxian He
- Key Laboratory Agricultural Engineering in Structure and Environment, Ministry of Agriculture and Rural Affairs, China Agricultural University, Beijing, China
| | - Jie He
- National Institute of Education, Nanyang Technological University, Singapore, Singapore
| | - Genhua Niu
- Texas A&M AgriLife Research at El Paso, Texas A&M University System, El Paso, TX, United States
| | - Rongfu Gao
- College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
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12
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Hultine KR, Dettman DL, Williams DG, Puente R, English NB, Butterfield BJ, Búrquez A. Relationships among climate, stem growth, and biomass δ
13
C in the giant saguaro cactus (
Carnegiea gigantea
). Ecosphere 2018. [DOI: 10.1002/ecs2.2498] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- K. R. Hultine
- Department of Research, Conservation and Collections Desert Botanical Garden Phoenix Arizona 85008 USA
| | - D. L. Dettman
- Department of Geosciences University of Arizona Tucson Arizona 85721 USA
| | - D. G. Williams
- Department of Botany University of Wyoming Laramie Wyoming 82071 USA
| | - R. Puente
- Department of Research, Conservation and Collections Desert Botanical Garden Phoenix Arizona 85008 USA
| | - N. B. English
- School of Health, Medical and Applied Sciences Central Queensland University Townsville Queensland 4810 Australia
| | - B. J. Butterfield
- Merriam Powell Center for Environmental Research and Department of Biological Sciences Northern Arizona University Flagstaff Arizona 86011 USA
| | - A. Búrquez
- Unidad Hermosillo Instituto de Ecología Universidad Nacional Autónoma de México Apartado Postal 1354 C.P. 83000 Hermosillo Sonora México
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13
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Earles JM, Theroux-Rancourt G, Roddy AB, Gilbert ME, McElrone AJ, Brodersen CR. Beyond Porosity: 3D Leaf Intercellular Airspace Traits That Impact Mesophyll Conductance. PLANT PHYSIOLOGY 2018; 178:148-162. [PMID: 30042212 PMCID: PMC6130031 DOI: 10.1104/pp.18.00550] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 07/10/2018] [Indexed: 05/21/2023]
Abstract
The leaf intercellular airspace (IAS) is generally considered to have high conductance to CO2 diffusion relative to the liquid phase. While previous studies accounted for leaf-level variation in porosity and mesophyll thickness, they omitted 3D IAS traits that potentially influence IAS conductance (gIAS). Here, we reevaluated the standard equation for gIAS by incorporating tortuosity, lateral path lengthening, and IAS connectivity. We measured and spatially mapped these geometric IAS traits for 19 Bromeliaceae species with Crassulacean acid metabolism (CAM) or C3 photosynthetic pathways using x-ray microcomputed tomography imaging and a novel computational approach. We found substantial variation in porosity (0.04-0.73 m3 m-3), tortuosity (1.09-3.33 m2 m-2), lateral path lengthening (1.12-3.19 m m-1), and IAS connectivity (0.81-0.97 m2 m-2) across all bromeliad leaves. The revised gIAS model predicted significantly lower gIAS in CAM (0.01-0.19 mol m-2 s-1 bar-1) than in C3 (0.41-2.38 mol m-2 s-1 bar-1) plants due to a coordinated decline in these IAS traits. Our reevaluated equation also generally predicted lower gIAS values than the former one. Moreover, we observed high spatial heterogeneity in these IAS geometric traits throughout the mesophyll, especially within CAM leaves. Our data show that IAS traits that better capture the 3D complexity of leaves strongly influence gIAS and that the impact of the IAS on mesophyll conductance should be carefully considered with respect to leaf anatomy. We provide a simple function to estimate tortuosity and lateral path lengthening in the absence of access to imaging tools such as x-ray microcomputed tomography or other novel 3D image-processing techniques.
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Affiliation(s)
- J Mason Earles
- School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06511
| | | | - Adam B Roddy
- School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06511
| | - Matthew E Gilbert
- Department of Plant Sciences, University of California, Davis, California 95616
| | - Andrew J McElrone
- United States Department of Agriculture-Agricultural Research Service, Davis, California 95616
- Department of Viticulture and Enology, University of California, Davis, California 95616
| | - Craig R Brodersen
- School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06511
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Males J, Griffiths H. Stomatal Biology of CAM Plants. PLANT PHYSIOLOGY 2017; 174:550-560. [PMID: 28242656 PMCID: PMC5462028 DOI: 10.1104/pp.17.00114] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 02/24/2017] [Indexed: 05/19/2023]
Abstract
Recent advances in the stomatal biology of CAM plants are reviewed, and key opportunities for future progress are identified.
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Affiliation(s)
- Jamie Males
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Howard Griffiths
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
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15
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Alonso-Cantabrana H, von Caemmerer S. Carbon isotope discrimination as a diagnostic tool for C4 photosynthesis in C3-C4 intermediate species. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:3109-21. [PMID: 26862154 PMCID: PMC4867892 DOI: 10.1093/jxb/erv555] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The presence and activity of the C4 cycle in C3-C4 intermediate species have proven difficult to analyze, especially when such activity is low. This study proposes a strategy to detect C4 activity and estimate its contribution to overall photosynthesis in intermediate plants, by using tunable diode laser absorption spectroscopy (TDLAS) coupled to gas exchange systems to simultaneously measure the CO2 responses of CO2 assimilation (A) and carbon isotope discrimination (Δ) under low O2 partial pressure. Mathematical models of C3-C4 photosynthesis and Δ are then fitted concurrently to both responses using the same set of constants. This strategy was applied to the intermediate species Flaveria floridana and F. brownii, and to F. pringlei and F. bidentis as C3 and C4 controls, respectively. Our results support the presence of a functional C4 cycle in F. floridana, that can fix 12-21% of carbon. In F. brownii, 75-100% of carbon is fixed via the C4 cycle, and the contribution of mesophyll Rubisco to overall carbon assimilation increases with CO2 partial pressure in both intermediate plants. Combined gas exchange and Δ measurement and modeling is a powerful diagnostic tool for C4 photosynthesis.
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Affiliation(s)
- Hugo Alonso-Cantabrana
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - Susanne von Caemmerer
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
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16
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Owen NA, Choncubhair ÓN, Males J, Del Real Laborde JI, Rubio-Cortés R, Griffiths H, Lanigan G. Eddy covariance captures four-phase crassulacean acid metabolism (CAM) gas exchange signature in Agave. PLANT, CELL & ENVIRONMENT 2016; 39:295-309. [PMID: 26177873 DOI: 10.1111/pce.12610] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 07/05/2015] [Indexed: 06/04/2023]
Abstract
Mass and energy fluxes were measured over a field of Agave tequilana in Mexico using eddy covariance (EC) methodology. Data were gathered over 252 d, including the transition from wet to dry periods. Net ecosystem exchanges (FN,EC ) displayed a crassulacean acid metabolism (CAM) rhythm that alternated from CO2 sink at night to CO2 source during the day, and partitioned canopy fluxes (FA,EC ) showed a characteristic four-phase CO2 exchange pattern. Results were cross-validated against diel changes in titratable acidity, leaf-unfurling rates, energy exchange fluxes and reported biomass yields. Projected carbon balance (g C m(-2) year(-1) , mean ± 95% confidence interval) indicated the site was a net sink of -333 ± 24, of which contributions from soil respiration were +692 ± 7, and FA,EC was -1025 ± 25. EC estimated biomass yield was 20.1 Mg (dry) ha(-1) year(-1) . Average integrated daily FA,EC was -234 ± 5 mmol CO2 m(-2) d(-1) and persisted almost unchanged after 70 d of drought conditions. Regression analyses were performed on the EC data to identify the best environmental predictors of FA . Results suggest that the carbon acquisition strategy of Agave offers productivity and drought resilience advantages over conventional semi-arid C3 and C4 bioenergy candidates.
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Affiliation(s)
- Nick A Owen
- Department of Plant Sciences, University of Cambridge, Cambridge, UK, CB2 3EA
| | | | - Jamie Males
- Department of Plant Sciences, University of Cambridge, Cambridge, UK, CB2 3EA
| | | | - Ramón Rubio-Cortés
- Rancho el Indio, Tequila Sauza, S. de R.L. de C.V., Tequila, Jalisco, Mexico
| | - Howard Griffiths
- Department of Plant Sciences, University of Cambridge, Cambridge, UK, CB2 3EA
| | - Gary Lanigan
- Teagasc Environmental Research Centre, Johnstown Castle, County Wexford, Ireland
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17
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Winter K, Holtum JAM, Smith JAC. Crassulacean acid metabolism: a continuous or discrete trait? THE NEW PHYTOLOGIST 2015; 208:73-8. [PMID: 25975197 DOI: 10.1111/nph.13446] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 03/22/2015] [Indexed: 05/27/2023]
Abstract
The key components of crassulacean acid metabolism (CAM) - nocturnal fixation of atmospheric CO2 and its processing via Rubisco in the subsequent light period - are now reasonably well understood in terms of the biochemical reactions defining this water-saving mode of carbon assimilation. Phenotypically, however, the degree to which plants engage in the CAM cycle relative to regular C3 photosynthesis is highly variable. Depending upon species, ontogeny and environment, the contribution of nocturnal CO2 fixation to 24-h carbon gain can range continuously from close to 0% to 100%. Nevertheless, not all possible combinations of light and dark CO2 fixation appear equally common. Large-scale surveys of carbon-isotope ratios typically show a strongly bimodal frequency distribution, with relatively few intermediate values. Recent research has revealed that many species capable of low-level CAM activity are nested within the peak of C3 -type isotope signatures. While questions remain concerning the adaptive significance of dark CO2 fixation in such species, plants with low-level CAM should prove valuable models for investigating the discrete changes in genetic architecture and gene expression that have enabled the evolutionary transition from C3 to CAM.
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Affiliation(s)
- Klaus Winter
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama
| | - Joseph A M Holtum
- Centre for Tropical Biodiversity and Climate Change, James Cook University, Townsville, QLD, 4811, Australia
| | - J Andrew C Smith
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
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18
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Cushman JC, Davis SC, Yang X, Borland AM. Development and use of bioenergy feedstocks for semi-arid and arid lands. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:4177-93. [PMID: 25873672 DOI: 10.1093/jxb/erv087] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Global climate change is predicted to increase heat, drought, and soil-drying conditions, and thereby increase crop sensitivity to water vapour pressure deficit, resulting in productivity losses. Increasing competition between agricultural freshwater use and municipal or industrial uses suggest that crops with greater heat and drought durability and greater water-use efficiency will be crucial for sustainable biomass production systems in the future. Agave (Agavaceae) and Opuntia (Cactaceae) represent highly water-use efficient bioenergy crops that could diversify bioenergy feedstock supply yet preserve or expand feedstock production into semi-arid, abandoned, or degraded agricultural lands, and reclaim drylands. Agave and Opuntia are crassulacean acid metabolism species that can achieve high water-use efficiencies and grow in water-limited areas with insufficient precipitation to support traditional C3 or C4 bioenergy crops. Both Agave and Opuntia have the potential to produce above-ground biomass rivalling that of C3 and C4 crops under optimal growing conditions. The low lignin and high amorphous cellulose contents of Agave and Opuntia lignocellulosic biomass will be less recalcitrant to deconstruction than traditional feedstocks, as confirmed by pretreatments that improve saccharification of Agave. Refined environmental productivity indices and geographical information systems modelling have provided estimates of Agave and Opuntia biomass productivity and terrestrial sequestration of atmospheric CO2; however, the accuracy of such modelling efforts can be improved through the expansion of field trials in diverse geographical settings. Lastly, life cycle analysis indicates that Agave would have productivity, life cycle energy, and greenhouse gas balances comparable or superior to those of traditional bioenergy feedstocks, but would be far more water-use efficient.
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Affiliation(s)
- John C Cushman
- Department of Biochemistry & Molecular Biology, MS330, University of Nevada, Reno, NV 89557-0330, USA
| | - Sarah C Davis
- Voinovich School of Leadership and Public Affairs and Department of Environmental and Plant Biology, Ohio University, Athens, OH 45701, USA
| | - Xiaohan Yang
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6407, USA
| | - Anne M Borland
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6407, USA School of Biology, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
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19
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von Caemmerer S, Ghannoum O, Pengelly JJL, Cousins AB. Carbon isotope discrimination as a tool to explore C4 photosynthesis. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:3459-70. [PMID: 24711615 DOI: 10.1093/jxb/eru127] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Photosynthetic carbon isotope discrimination is a non-destructive tool for investigating C4 metabolism. Tuneable diode laser absorption spectroscopy provides new opportunities for making rapid, concurrent measurements of carbon isotope discrimination and CO2 assimilation over a range of environmental conditions, and this has facilitated the use of carbon isotope discrimination as a probe of C4 metabolism. In spite of the significant progress made in recent years, understanding how photosynthetic carbon isotope discrimination measured concurrently with gas exchange relates to carbon isotope composition of leaf and plant dry matter remains a challenge that requires resolution if this technique is to be successfully applied as a screening tool in crop breeding and phylogenetic research. In this review, we update our understanding of the factors and assumptions that underlie variations in photosynthetic carbon isotope discrimination in C4 leaves. Closing the main gaps in our understanding of carbon isotope discrimination during C4 photosynthesis may help advance research aimed at developing higher productivity and efficiency in key C4 food, feed, and biofuel crops.
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Affiliation(s)
- Susanne von Caemmerer
- Research School of Biology, The Australian National University, Canberra ACT 0200, Australia
| | - Oula Ghannoum
- Hawkesbury Institute for the Environment, University of Western Sydney, Hawkesbury campus, Locked Bag 1797, Penrith 2751, NSW, Australia
| | - Jasper J L Pengelly
- Research School of Biology, The Australian National University, Canberra ACT 0200, Australia
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
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20
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Williams DG, Hultine KR, Dettman DL. Functional trade-offs in succulent stems predict responses to climate change in columnar cacti. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:3405-3413. [PMID: 24759883 DOI: 10.1093/jxb/eru174] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Columnar cacti occur naturally in many habitats and environments in the Americas but are conspicuously dominant in very dry desert regions. These majestic plants are widely regarded for their cultural, economic, and ecological value and, in many ecosystems, support highly diverse communities of pollinators, seed dispersers, and frugivores. Massive amounts of water and other resources stored in the succulent photosynthetic stems of these species confer a remarkable ability to grow and reproduce during intensely hot and dry periods. Yet many columnar cacti are potentially under severe threat from environmental global changes, including climate change and loss of habitat. Stems in columnar cacti and other cylindrical-stemmed cacti are morphologically diverse; stem volume-to-surface area ratio (V:S) across these taxa varies by almost two orders of magnitude. Intrinsic functional trade-offs are examined here across a broad range of V:S in species of columnar cacti. It is proposed that variation in photosynthetic gas exchange, growth, and response to stress is highly constrained by stem V:S, establishing a mechanistic framework for understanding the sensitivity of columnar cacti to climate change and drought. Specifically, species that develop stems with low V:S, and thus have little storage capacity, are expected to express high mass specific photosynthesis and growth rates under favourable conditions compared with species with high V:S. But the trade-off of having little storage capacity is that low V:S species are likely to be less tolerant of intense or long-duration drought compared with high V:S species. The application of stable isotope measurements of cactus spines as recorders of growth, water relations, and metabolic responses to the environment across species of columnar cacti that vary in V:S is also reviewed. Taken together, our approach provides a coherent theory and required set of observations needed for predicting the responses of columnar cacti to climate change.
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Affiliation(s)
- David G Williams
- Department of Botany, 1000 East University Ave, University of Wyoming, Laramie, WY 82070, USA
| | - Kevin R Hultine
- Department of Research, Conservation and Collections, Desert Botanical Garden, Phoenix, AZ, USA
| | - David L Dettman
- Department of Geosciences, University of Arizona, Tucson, AZ, USA
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21
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Owen NA, Griffiths H. A system dynamics model integrating physiology and biochemical regulation predicts extent of crassulacean acid metabolism (CAM) phases. THE NEW PHYTOLOGIST 2013; 200:1116-1131. [PMID: 23992169 DOI: 10.1111/nph.12461] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 07/19/2013] [Indexed: 06/02/2023]
Abstract
A system dynamics (SD) approach was taken to model crassulacean acid metabolism (CAM) expression from measured biochemical and physiological constants. SD emphasizes state-dependent feedback interaction to describe the emergent properties of a complex system. These mechanisms maintain biological systems with homeostatic limits on a temporal basis. Previous empirical studies on CAM have correlated biological constants (e.g. enzyme kinetic parameters) with expression over the CAM diel cycle. The SD model integrates these constants within the architecture of the CAM 'system'. This allowed quantitative causal connections to be established between biological inputs and the four distinct phases of CAM delineated by gas exchange and malic acid accumulation traits. Regulation at flow junctions (e.g. stomatal and mesophyll conductance, and malic acid transport across the tonoplast) that are subject to feedback control (e.g. stomatal aperture, malic acid inhibition of phosphoenolpyruvate carboxylase, and enzyme kinetics) was simulated. Simulated expression for the leaf-succulent Kalanchoë daigremontiana and more succulent tissues of Agave tequilana showed strong correlation with measured gas exchange and malic acid accumulation (R(2) = 0.912 and 0.937, respectively, for K. daigremontiana and R(2) = 0.928 and 0.942, respectively, for A. tequilana). Sensitivity analyses were conducted to quantitatively identify determinants of diel CO2 uptake. The transition in CAM expression from low to high volume/area tissues (elimination of phase II-IV carbon-uptake signatures) was achieved largely by the manipulation three input parameters.
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Affiliation(s)
- Nick A Owen
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK
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22
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Ripley BS, Abraham T, Klak C, Cramer MD. How succulent leaves of Aizoaceae avoid mesophyll conductance limitations of photosynthesis and survive drought. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:5485-96. [PMID: 24127513 PMCID: PMC3871808 DOI: 10.1093/jxb/ert314] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In several taxa, increasing leaf succulence has been associated with decreasing mesophyll conductance (g M) and an increasing dependence on Crassulacean acid metabolism (CAM). However, in succulent Aizoaceae, the photosynthetic tissues are adjacent to the leaf surfaces with an internal achlorophyllous hydrenchyma. It was hypothesized that this arrangement increases g M, obviating a strong dependence on CAM, while the hydrenchyma stores water and nutrients, both of which would only be sporadically available in highly episodic environments. These predictions were tested with species from the Aizoaceae with a 5-fold variation in leaf succulence. It was shown that g M values, derived from the response of photosynthesis to intercellular CO2 concentration (A:C i), were independent of succulence, and that foliar photosynthate δ(13)C values were typical of C3, but not CAM photosynthesis. Under water stress, the degree of leaf succulence was positively correlated with an increasing ability to buffer photosynthetic capacity over several hours and to maintain light reaction integrity over several days. This was associated with decreased rates of water loss, rather than tolerance of lower leaf water contents. Additionally, the hydrenchyma contained ~26% of the leaf nitrogen content, possibly providing a nutrient reservoir. Thus the intermittent use of C3 photosynthesis interspersed with periods of no positive carbon assimilation is an alternative strategy to CAM for succulent taxa (Crassulaceae and Aizoaceae) which occur sympatrically in the Cape Floristic Region of South Africa.
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Affiliation(s)
- Brad S. Ripley
- Department of Botany, Rhodes University, 6140 Grahamstown, South Africa
| | - Trevor Abraham
- Department of Botany, Rhodes University, 6140 Grahamstown, South Africa
| | - Cornelia Klak
- Bolus Herbarium, Department of Biological Sciences, University of Cape Town, 7701 Rondebosch, South Africa
| | - Michael D. Cramer
- Department of Biological Sciences, University of Cape Town, 7701 Rondebosch, South Africa
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Cernusak LA, Ubierna N, Winter K, Holtum JAM, Marshall JD, Farquhar GD. Environmental and physiological determinants of carbon isotope discrimination in terrestrial plants. THE NEW PHYTOLOGIST 2013; 200:950-65. [PMID: 23902460 DOI: 10.1111/nph.12423] [Citation(s) in RCA: 232] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Accepted: 06/25/2013] [Indexed: 05/05/2023]
Abstract
Stable carbon isotope ratios (δ(13) C) of terrestrial plants are employed across a diverse range of applications in environmental and plant sciences; however, the kind of information that is desired from the δ(13) C signal often differs. At the extremes, it ranges between purely environmental and purely biological. Here, we review environmental drivers of variation in carbon isotope discrimination (Δ) in terrestrial plants, and the biological processes that can either damp or amplify the response. For C3 plants, where Δ is primarily controlled by the ratio of intercellular to ambient CO2 concentrations (ci /ca ), coordination between stomatal conductance and photosynthesis and leaf area adjustment tends to constrain the potential environmentally driven range of Δ. For C4 plants, variation in bundle-sheath leakiness to CO2 can either damp or amplify the effects of ci /ca on Δ. For plants with crassulacean acid metabolism (CAM), Δ varies over a relatively large range as a function of the proportion of daytime to night-time CO2 fixation. This range can be substantially broadened by environmental effects on Δ when carbon uptake takes place primarily during the day. The effective use of Δ across its full range of applications will require a holistic view of the interplay between environmental control and physiological modulation of the environmental signal.
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Affiliation(s)
- Lucas A Cernusak
- Department of Marine and Tropical Biology, James Cook University, Cairns, Qld, Australia
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Herrera A. Crassulacean acid metabolism-cycling in Euphorbia milii. AOB PLANTS 2013; 5:plt014. [PMID: 23596548 PMCID: PMC3628315 DOI: 10.1093/aobpla/plt014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 02/14/2013] [Indexed: 05/22/2023]
Abstract
Crassulacean acid metabolism (CAM) occurs in many Euphorbiaceae, particularly Euphorbia, a genus with C3 and C4 species as well. With the aim of contributing to our knowledge of the evolution of CAM in this genus, this study examined the possible occurrence of CAM in Euphorbia milii, a species with leaf succulence and drought tolerance suggestive of this carbon fixation pathway. Leaf anatomy consisted of a palisade parenchyma, a spongy parenchyma and a bundle sheath with chloroplasts, which indicates the possible functioning of C2 photosynthesis. No evidence of nocturnal CO2 fixation was found in plants of E. milii either watered or under drought; watered plants had a low nocturnal respiration rate (R). After 12 days without watering, the photosynthetic rate (P N) decreased 85 % and nocturnal R was nearly zero. Nocturnal H(+) accumulation (ΔH(+)) in watered plants was 18 ± 2 (corresponding to malate) and 18 ± 4 (citrate) μmol H(+) (g fresh mass)(-1). Respiratory CO2 recycling through acid synthesis contributed to a night-time water saving of 2 and 86 % in watered plants and plants under drought, respectively. Carbon isotopic composition (δ(13)C) was -25.2 ± 0.7 ‰ in leaves and -24.7 ± 0.1 ‰ in stems. Evidence was found for the operation of weak CAM in E. milii, with statistically significant ΔH(+), no nocturnal CO2 uptake and values of δ(13)C intermediate between C3 and constitutive CAM plants; ΔH(+) was apparently attributable to both malate and citrate. The results suggest that daily malate accumulation results from recycling of part of the nocturnal respiratory CO2, which helps explain the occurrence of an intermediate value of leaf δ(13)C. Euphorbia milii can be considered as a CAM-cycling species. The significance of the operation of CAM-cycling in E. milii lies in water conservation, rather than carbon acquisition. The possible occurrence of C2 photosynthesis merits research.
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Affiliation(s)
- Ana Herrera
- Instituto de Biología Experimental, Facultad de Ciencias, Universidad Central de Venezuela, Caracas, Miranda 1020, Venezuela
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Ricalde MF, Andrade JL, Durán R, Dupuy JM, Simá JL, Us-Santamaría R, Santiago LS. Environmental regulation of carbon isotope composition and crassulacean acid metabolism in three plant communities along a water availability gradient. Oecologia 2010; 164:871-80. [PMID: 20652592 PMCID: PMC2981738 DOI: 10.1007/s00442-010-1724-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2009] [Accepted: 07/04/2010] [Indexed: 10/27/2022]
Abstract
Expression of crassulacean acid metabolism (CAM) is characterized by extreme variability within and between taxa and its sensitivity to environmental variation. In this study, we determined seasonal fluctuations in CAM photosynthesis with measurements of nocturnal tissue acidification and carbon isotopic composition (δ(13)C) of bulk tissue and extracted sugars in three plant communities along a precipitation gradient (500, 700, and 1,000 mm year(-1)) on the Yucatan Peninsula. We also related the degree of CAM to light habitat and relative abundance of species in the three sites. For all species, the greatest tissue acid accumulation occurred during the rainy season. In the 500 mm site, tissue acidification was greater for the species growing at 30% of daily total photon flux density (PFD) than species growing at 80% PFD. Whereas in the two wetter sites, the species growing at 80% total PFD had greater tissue acidification. All species had values of bulk tissue δ(13)C less negative than -20‰, indicating strong CAM activity. The bulk tissue δ(13)C values in plants from the 500 mm site were 2‰ less negative than in plants from the wetter sites, and the only species growing in the three communities, Acanthocereus tetragonus (Cactaceae), showed a significant negative relationship between both bulk tissue and sugar δ(13)C values and annual rainfall, consistent with greater CO(2) assimilation through the CAM pathway with decreasing water availability. Overall, variation in the use of CAM photosynthesis was related to water and light availability and CAM appeared to be more ecologically important in the tropical dry forests than in the coastal dune.
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Affiliation(s)
- M. Fernanda Ricalde
- Unidad de Recursos Naturales, Centro de Investigación Científica de Yucatán, A. C., Calle 43 # 130, Col. Chuburná de Hidalgo, 97200 Mérida, Yucatán Mexico
| | - José Luis Andrade
- Unidad de Recursos Naturales, Centro de Investigación Científica de Yucatán, A. C., Calle 43 # 130, Col. Chuburná de Hidalgo, 97200 Mérida, Yucatán Mexico
| | - Rafael Durán
- Unidad de Recursos Naturales, Centro de Investigación Científica de Yucatán, A. C., Calle 43 # 130, Col. Chuburná de Hidalgo, 97200 Mérida, Yucatán Mexico
| | - Juan Manuel Dupuy
- Unidad de Recursos Naturales, Centro de Investigación Científica de Yucatán, A. C., Calle 43 # 130, Col. Chuburná de Hidalgo, 97200 Mérida, Yucatán Mexico
| | - J. Luis Simá
- Unidad de Recursos Naturales, Centro de Investigación Científica de Yucatán, A. C., Calle 43 # 130, Col. Chuburná de Hidalgo, 97200 Mérida, Yucatán Mexico
| | - Roberth Us-Santamaría
- Unidad de Recursos Naturales, Centro de Investigación Científica de Yucatán, A. C., Calle 43 # 130, Col. Chuburná de Hidalgo, 97200 Mérida, Yucatán Mexico
| | - Louis S. Santiago
- Department of Botany and Plant Sciences, University of California, 2150 Batchelor Hall, Riverside, CA 92521 USA
- Facility for Isotope Ratio Mass Spectrometry (FIRMS), Center for Conservation Biology, University of California, Riverside, CA 92521 USA
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Wild B, Wanek W, Postl W, Richter A. Contribution of carbon fixed by Rubisco and PEPC to phloem export in the Crassulacean acid metabolism plant Kalanchoe daigremontiana. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:1375-83. [PMID: 20159885 PMCID: PMC2837257 DOI: 10.1093/jxb/erq006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 12/23/2009] [Accepted: 01/04/2010] [Indexed: 05/21/2023]
Abstract
Crassulacean acid metabolism (CAM) plants exhibit a complex interplay between CO(2) fixation by phosphoenolpyruvate carboxylase (PEPC) and ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco), and carbon demand for CAM maintenance and growth. This study investigated the flux of carbon from PEPC and direct Rubisco fixation to different leaf carbon pools and to phloem sap over the diurnal cycle. Concentrations and carbon isotope compositions of starch, soluble sugars, and organic acids were determined in leaves and phloem exudates of Kalanchoë daigremontiana Hamet et Perr., and related to CO(2) fixation by PEPC and Rubisco. Three types of leaf carbon pools could be distinguished. (i) Starch and malate pools were dominant and showed a pattern of reciprocal mobilization and accumulation (85/54 and 13/48 mg C g(-1) DW, respective, at the beginning/end of phase I). The carbon isotope composition of these pools was compatible with predominant PEPC fixation (delta(13)C values of -13 and -11 per thousand for starch and malate compared to -11 per thousand of PEPC fixed carbon). (ii) Isotopic composition (-17 per thousand and -14 per thousand) and concentration of glucose and fructose (2 and 3 mg C g(-1) DW, respectively) were not affected by diurnal metabolism, suggesting a low turnover. (iii) Sucrose (1-3 mg C g(-1) DW), in contrast, exhibited large diurnal changes in delta(13)C values (from -17 per thousand in the evening to -12 per thousand in the morning), which were not matched by net changes in sucrose concentration. This suggests a high sucrose turnover, fed by nocturnal starch degradation and direct Rubisco fixation during the day. A detailed dissection of the carbon fixation and mobilization pattern in K. daigremontiana revealed that direct fixation of Rubisco during the light accounted for 30% of phloem sucrose, but only 15% of fixed carbon, indicating that carbon from direct Rubisco fixation was preferentially used for leaf export.
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Affiliation(s)
- Birgit Wild
- Department of Chemical Ecology and Ecosystem Research, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria.
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von Caemmerer S, Griffiths H. Stomatal responses to CO2 during a diel Crassulacean acid metabolism cycle in Kalanchoe daigremontiana and Kalanchoe pinnata. PLANT, CELL & ENVIRONMENT 2009; 32:567-76. [PMID: 19210641 DOI: 10.1111/j.1365-3040.2009.01951.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
To investigate the diurnal variation of stomatal sensitivity to CO2, stomatal response to a 30 min pulse of low CO2 was measured four times during a 24 h time-course in two Crassulacean acid metabolism (CAM) species Kalanchoe daigremontiana and Kalanchoe pinnata, which vary in the degree of succulence, and hence, expression and commitment to CAM. In both species, stomata opened in response to a reduction in pCO2 in the dark and in the latter half of the light period, and thus in CAM species, chloroplast photosynthesis is not required for the stomatal response to low pCO2. Stomata did not respond to a decreased pCO2 in K. daigremontiana in the light when stomata were closed, even when the supply of internal CO2 was experimentally reduced. We conclude that stomatal closure during phase III is not solely mediated by high internal pCO2, and suggest that in CAM species the diurnal variability in the responsiveness of stomata to pCO2 could be explained by hypothesizing the existence of a single CO2 sensor which interacts with other signalling pathways. When not perturbed by low pCO2, CO2 assimilation rate and stomatal conductance were correlated both in the light and in the dark in both species.
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Affiliation(s)
- Susanne von Caemmerer
- Molecular Plant Physiology Group, Research School of Biological Sciences, Australian National University, Canberra ACT 2601, Australia
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Cernusak LA, Mejia-Chang M, Winter K, Griffiths H. Oxygen isotope composition of CAM and C3 Clusia species: non-steady-state dynamics control leaf water 18O enrichment in succulent leaves. PLANT, CELL & ENVIRONMENT 2008; 31:1644-1662. [PMID: 18684241 DOI: 10.1111/j.1365-3040.2008.01868.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Leaf gas exchange and leaf water (18)O enrichment (Delta(18)O(L)) were measured in three Clusia species under field conditions during dry and wet seasons and in Miconia argentea during the dry season in the Republic of Panama. During the dry season, all three Clusia species used crassulacean acid metabolism (CAM); during the wet season Clusia pratensis operated in the C(3) mode, while Clusia uvitana and Clusia rosea used CAM. Large departures from isotopic steady state were observed in daytime Delta(18)O(L) of the Clusia species, especially during the dry season. In contrast, daytime Delta(18)O(L) was near isotopic steady state in the C(3) tree M. argentea. Across the full data set, non-steady-state predictions explained 49% of variation in observed Delta(18)O(L), whereas steady-state predictions explained only 14%. During the wet season, when Delta(18)O(L) could be compared with Clusia individuals operating in both C(3) and CAM modes, steady-state and non-steady-state models gave contrasting predictions with respect to interspecific variation in daytime Delta(18)O(L). The observed Delta(18)O(L) pattern matched that predicted for the non-steady state. The results provided a clear example of how non-steady-state control of leaf water (18)O dynamics can shift the slope of the relationship between transpiration rate and daytime Delta(18)O(L) from negative to positive.
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Affiliation(s)
- Lucas A Cernusak
- Smithsonian Tropical Research Institute, Balboa, Ancon, Republic of Panama.
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The evolution of inorganic carbon concentrating mechanisms in photosynthesis. Philos Trans R Soc Lond B Biol Sci 2008; 363:2641-50. [PMID: 18487130 PMCID: PMC2606764 DOI: 10.1098/rstb.2008.0020] [Citation(s) in RCA: 167] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Inorganic carbon concentrating mechanisms (CCMs) catalyse the accumulation of CO(2) around rubisco in all cyanobacteria, most algae and aquatic plants and in C(4) and crassulacean acid metabolism (CAM) vascular plants. CCMs are polyphyletic (more than one evolutionary origin) and involve active transport of HCO(3)(-), CO(2) and/or H(+), or an energized biochemical mechanism as in C(4) and CAM plants. While the CCM in almost all C(4) plants and many CAM plants is constitutive, many CCMs show acclimatory responses to variations in the supply of not only CO(2) but also photosynthetically active radiation, nitrogen, phosphorus and iron. The evolution of CCMs is generally considered in the context of decreased CO(2) availability, with only a secondary role for increasing O(2). However, the earliest CCMs may have evolved in oxygenic cyanobacteria before the atmosphere became oxygenated in stromatolites with diffusion barriers around the cells related to UV screening. This would decrease CO(2) availability to cells and increase the O(2) concentration within them, inhibiting rubisco and generating reactive oxygen species, including O(3).
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Flexas J, Ribas-Carbó M, Diaz-Espejo A, Galmés J, Medrano H. Mesophyll conductance to CO2: current knowledge and future prospects. PLANT, CELL & ENVIRONMENT 2008; 31:602-21. [PMID: 17996013 DOI: 10.1111/j.1365-3040.2007.01757.x] [Citation(s) in RCA: 554] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
During photosynthesis, CO2 moves from the atmosphere (C(a)) surrounding the leaf to the sub-stomatal internal cavities (C(i)) through stomata, and from there to the site of carboxylation inside the chloroplast stroma (C(c)) through the leaf mesophyll. The latter CO2 diffusion component is called mesophyll conductance (g(m)), and can be divided in at least three components, that is, conductance through intercellular air spaces (g(ias)), through cell wall (g(w)) and through the liquid phase inside cells (g(liq)). A large body of evidence has accumulated in the past two decades indicating that g(m) is sufficiently small as to significantly decrease C(c) relative to C(i), therefore limiting photosynthesis. Moreover, g(m) is not constant, and it changes among species and in response to environmental factors. In addition, there is now evidence that g(liq) and, in some cases, g(w), are the main determinants of g(m). Mesophyll conductance is very dynamic, changing in response to environmental variables as rapid or even faster than stomatal conductance (i.e. within seconds to minutes). A revision of current knowledge on g(m) is presented. Firstly, a historical perspective is given, highlighting the founding works and methods, followed by a re-examination of the range of variation of g(m) among plant species and functional groups, and a revision of the responses of g(m) to different external (biotic and abiotic) and internal (developmental, structural and metabolic) factors. The possible physiological bases for g(m), including aquaporins and carbonic anhydrases, are discussed. Possible ecological implications for variable g(m) are indicated, and the errors induced by neglecting g(m) when interpreting photosynthesis and carbon isotope discrimination models are highlighted. Finally, a series of research priorities for the near future are proposed.
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Affiliation(s)
- Jaume Flexas
- Grup de Recerca en Biologia de les Plantes en Condicions Mediterrànies, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, 07122 Palma de Mallorca, Balears, Spain.
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Griffiths H, Robe WE, Girnus J, Maxwell K. Leaf succulence determines the interplay between carboxylase systems and light use during Crassulacean acid metabolism in Kalanchöe species. JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:1851-1861. [PMID: 18408219 DOI: 10.1093/jxb/ern085] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The photosynthetic physiology of Crassulacean acid metabolism was investigated in two Kalanchoë species with differing leaf succulence. The magnitude of CAM was higher for the more succulent leaves of K. daigremontiana, compared to the less succulent leaves of K. pinnata. High succulence was related to low mesophyll conductance: K. pinnata was able to maximize diurnal carbon gain by the C(3) pathway, whereas increased succulence is associated with a higher commitment to the CAM cycle in K. daigremontiana. The Rubisco specificity factor, tau, determining selectivity for CO(2) over O(2), was similar for both species (approximately 88), and lower than that of Spinacea (approximately 95), but in contrast to C(4) plants, the Rubisco K(mCO(2)) (determined independently) was also lower in Kalanchoë spp. than in spinach. Differences in light use were related to the nature of the sink strength in each Phase of CAM, with PEPC activity resulting in low electron transport rates. Decarboxylation was marked by high, non-saturated rates of electron transport, with Rubisco activity and activation state increasing in both species during the course of the light period. The degree of succulence, and extent of CAM activity, was associated with a progressive inhibition of PSII photochemistry and potential Rubisco activity during the night in both species. Rubisco could be 'woken up' more rapidly in K. pinnata, whereas 45 min light acclimation was required for full recovery of electron transport and Rubisco activity in K. daigremontiana. Leaf morphology therefore seems to alter the expression of and dependence on CAM, but also the extent of co-regulation of carboxylase networks and light use capacity.
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Affiliation(s)
- Howard Griffiths
- Physiological Ecology Group, Department of Plant Sciences, Downing Street, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
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Cousins AB, Badger MR, von Caemmerer S. C4 photosynthetic isotope exchange in NAD-ME- and NADP-ME-type grasses. JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:1695-703. [PMID: 18375608 DOI: 10.1093/jxb/ern001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Monitoring photosynthetic isotope exchange is an important tool for predicting the influence of plant communities on the global carbon cycle in response to climate change. C(4) grasses play an important role in the global carbon cycle, but their contribution to the isotopic composition of atmospheric CO(2) is not well understood. Instantaneous measurements of (13)CO(2) (Delta(13)C) and C(18)OO (Delta(18)O) isotope exchange in five NAD-ME and seven NADP-ME C(4) grasses have been conducted to investigate the difference in photosynthetic CO(2) isotopic fractionation in these subgroups. As previously reported, the isotope composition of the leaf material (delta(13)C) was depleted in (13)C in the NAD-ME compared with the NADP-ME grasses. However, Delta(13)C was not different between subtypes at high light, and, although Delta(13)C increased at low light, it did so similarly in both subtypes. This suggests that differences in leaf delta(13)C between the C(4) subtypes are not caused by photosynthetic isotope fractionation and leaf delta(13)C is not a good indicator of bundle sheath leakiness. Additionally, low carbonic anhydrase (CA) in C(4) grasses may influences Delta(13)C and should be considered when estimating the contribution of C(4) grasses to the global isotopic signature of atmospheric CO(2). It was found that measured Delta(18)O values were lower than those predicted from leaf CA activities and Delta(18)O was similar in all species measured. The Delta(18)O in these C(4) grasses is similar to low Delta(18)O previously measured in C(4) dicots which contain 2.5 times the leaf CA activity, suggesting that leaf CA activity is not a predictor of Delta(18)O in C(4) plants.
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Affiliation(s)
- Asaph B Cousins
- Molecular Plant Physiology Group, Research School of Biological Sciences, Australian National University, Canberra, Australian Capital Territory, 2601 Australia.
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McNevin DB, Badger MR, Whitney SM, von Caemmerer S, Tcherkez GGB, Farquhar GD. Differences in carbon isotope discrimination of three variants of D-ribulose-1,5-bisphosphate carboxylase/oxygenase reflect differences in their catalytic mechanisms. J Biol Chem 2007; 282:36068-76. [PMID: 17925403 DOI: 10.1074/jbc.m706274200] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023] Open
Abstract
The carboxylation kinetic (stable carbon) isotope effect was measured for purified d-ribulose-1,5-bisphosphate carboxylases/oxygenases (Rubiscos) with aqueous CO(2) as substrate by monitoring Rayleigh fractionation using membrane inlet mass spectrometry. This resulted in discriminations (Delta) of 27.4 +/- 0.9 per thousand for wild-type tobacco Rubisco, 22.2 +/- 2.1 per thousand for Rhodospirillum rubrum Rubisco, and 11.2 +/- 1.6 per thousand for a large subunit mutant of tobacco Rubisco in which Leu(335) is mutated to valine (L335V). These Delta values are consistent with the photosynthetic discrimination determined for wild-type tobacco and transplastomic tobacco lines that exclusively produce R. rubrum or L335V Rubisco. The Delta values are indicative of the potential evolutionary variability of Delta values for a range of Rubiscos from different species: Form I Rubisco from higher plants; prokaryotic Rubiscos, including Form II; and the L335V mutant. We explore the implications of these Delta values for the Rubisco catalytic mechanism and suggest that Rubiscos that are associated with a lower Delta value have a less product-like carboxylation transition state and/or allow a decarboxylation step that evolution has excluded in higher plants.
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Affiliation(s)
- Dennis B McNevin
- Molecular Plant Physiology and Environmental Biology, Research School of Biological Sciences, The Australian National University, Canberra, Australian Capital Territory, Australia
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Cousins AB, Baroli I, Badger MR, Ivakov A, Lea PJ, Leegood RC, von Caemmerer S. The role of phosphoenolpyruvate carboxylase during C4 photosynthetic isotope exchange and stomatal conductance. PLANT PHYSIOLOGY 2007; 145:1006-17. [PMID: 17827274 PMCID: PMC2048775 DOI: 10.1104/pp.107.103390] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Accepted: 09/03/2007] [Indexed: 05/17/2023]
Abstract
Phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) plays a key role during C(4) photosynthesis and is involved in anaplerotic metabolism, pH regulation, and stomatal opening. Heterozygous (Pp) and homozygous (pp) forms of a PEPC-deficient mutant of the C(4) dicot Amaranthus edulis were used to study the effect of reduced PEPC activity on CO(2) assimilation rates, stomatal conductance, and (13)CO(2) (Delta(13)C) and C(18)OO (Delta(18)O) isotope discrimination during leaf gas exchange. PEPC activity was reduced to 42% and 3% and the rates of CO(2) assimilation in air dropped to 78% and 10% of the wild-type values in the Pp and pp mutants, respectively. Stomatal conductance in air (531 mubar CO(2)) was similar in the wild-type and Pp mutant but the pp mutant had only 41% of the wild-type steady-state conductance under white light and the stomata opened more slowly in response to increased light or reduced CO(2) partial pressure, suggesting that the C(4) PEPC isoform plays an essential role in stomatal opening. There was little difference in Delta(13)C between the Pp mutant (3.0 per thousand +/- 0.4 per thousand) and wild type (3.3 per thousand +/- 0.4 per thousand), indicating that leakiness (), the ratio of CO(2) leak rate out of the bundle sheath to the rate of CO(2) supply by the C(4) cycle, a measure of the coordination of C(4) photosynthesis, was not affected by a 60% reduction in PEPC activity. In the pp mutant Delta(13)C was 16 per thousand +/- 3.2 per thousand, indicative of direct CO(2) fixation by Rubisco in the bundle sheath at ambient CO(2) partial pressure. Delta(18)O measurements indicated that the extent of isotopic equilibrium between leaf water and the CO(2) at the site of oxygen exchange () was low (0.6) in the wild-type and Pp mutant but increased to 0.9 in the pp mutant. We conclude that in vitro carbonic anhydrase activity overestimated as compared to values determined from Delta(18)O in wild-type plants.
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Affiliation(s)
- Asaph B Cousins
- Molecular Plant Physiology Group , Research School of Biological Sciences, Australian National University, Canberra, Australian Capital Territory 2601, Australia.
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Abstract
The role of carbon dioxide (CO(2)) as a signal in biochemical regulation networks of plants is fathomed. Transport mechanisms of CO(2) and HCO3- are surveyed, which are the prerequisite for signalling. A CO(2) sensor is not known to date, but any reaction where CO(2)/HCO3- is a substrate can be a candidate. Carbon concentrating mechanisms, e.g., in higher plants C(4)-photosynthesis and crassulacean acid metabolism (CAM), generate high internal CO(2) concentrations, important for photosynthesis, but also as a basis for signalling via diffusion of CO(2). Spatiotemporal dynamics of desynchronization/synchronization of photosynthetic activity over leaves can be followed by chlorophyll fluorescence imaging. One example of desynchronization is based on patchiness of stomatal opening/closing in heterobaric leaves due to anatomic constraints of lateral CO(2) diffusion. During CAM, largely different internal CO(2) concentrations prevail in the leaves, offering opportunities to study the effect of lateral diffusion of CO(2) in synchronizing photosynthetic activity over the entire leaves.
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Affiliation(s)
- Ulrich Lüttge
- Institute of Botany, Department of Biology, Technical University Darmstadt, Schnittspahnstrasse 3-5, 64287 Darmstadt, Germany.
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