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Rao S, Liu T, Cernusak LA, Song X. Harnessing photosynthetic C 18O 16O discrimination dynamics under leaf water nonsteady state to estimate mesophyll conductance: a new, regression-based method. THE NEW PHYTOLOGIST 2024. [PMID: 38634162 DOI: 10.1111/nph.19767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2023] [Accepted: 03/27/2024] [Indexed: 04/19/2024]
Abstract
Mesophyll conductance (gm) is a crucial plant trait that can significantly limit photosynthesis. Measurement of photosynthetic C18O16O discrimination (Δ18O) has proved to be the only viable means of resolving gm in both C3 and C4 plants. However, the currently available methods to exploit Δ18O for gm estimation are error prone due to their inadequacy in constraining the degree of oxygen isotope exchange (θ) during mesophyll CO2 hydration. Here, we capitalized on experimental manipulation of leaf water isotopic dynamics to establish a novel, nonsteady state, regression-based approach for simultaneous determination of gm and θ from online Δ18O measurements. We demonstrated the methodological and theoretical robustness of this new Δ18O-gm estimation approach and showed through measurements on several C3 and C4 species that this approach can serve as a benchmark method against which to identify previously-unrecognized biases of the existing Δ18O-gm methods. Our results highlight the unique value of this nonsteady state-based approach for contributing to ongoing efforts toward quantitative understanding of mesophyll conductance for crop yield improvement and carbon cycle modeling.
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Affiliation(s)
- Sen Rao
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, China
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China
| | - Tao Liu
- College of Resources, Sichuan Agricultural University, Chengdu, 611130, China
| | - Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, Qld, 4878, Australia
| | - Xin Song
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, China
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2
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Sharma N, Froehlich JE, Rillema R, Raba DA, Chambers T, Kerfeld CA, Kramer DM, Walker B, Brandizzi F. Arabidopsis stromal carbonic anhydrases exhibit non-overlapping roles in photosynthetic efficiency and development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2023. [PMID: 37010739 DOI: 10.1111/tpj.16231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 03/22/2023] [Indexed: 06/19/2023]
Abstract
Carbonic anhydrases (CAs) are ubiquitous enzymes that accelerate the reversible conversion of CO2 to HCO3 - . The Arabidopsis genome encodes members of the α-, β- and γ-CA families, and it has been hypothesized that βCA activity has a role in photosynthesis. In this work, we tested this hypothesis by characterizing the two plastidial βCAs, βCA1 and βCA5, in physiological conditions of growth. We conclusively established that both proteins are localized in the chloroplast stroma and that the loss of βCA5 induced the expression of βCA1, supporting the existence of regulatory mechanisms to control the expression of stromal βCAs. We also established that βCA1 and βCA5 have markedly different enzymatic kinetics and physiological relevance. Specifically, we found that βCA5 had a first-order rate constant ~10-fold lower than βCA1, and that the loss of βCA5 is detrimental to growth and could be rescued by high CO2 . Furthermore, we established that, while a βCA1 mutation showed near wild-type growth and no significant impact on photosynthetic efficiency, the loss of βCA5 markedly disrupted photosynthetic efficiency and light-harvesting capacity at ambient CO2 . Therefore, we conclude that in physiological autotrophic growth, the loss of the more highly expressed βCA1 does not compensate for the loss of a less active βCA5, which in turn is involved in growth and photosynthesis at ambient CO2 levels. These results lend support to the hypothesis that, in Arabidopsis,βCAs have non-overlapping roles in photosynthesis and identify a critical activity of stromal βCA5 and a dispensable role for βCA1.
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Affiliation(s)
- Naveen Sharma
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, 48824, USA
| | - John E Froehlich
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, 48824, USA
- Biochemistry and Molecular Biology Department, Michigan State University, East Lansing, Michigan, 48824, USA
| | - Rees Rillema
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, 48824, USA
| | - Daniel A Raba
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, 48824, USA
| | - Taylor Chambers
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, 48824, USA
| | - Cheryl A Kerfeld
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, 48824, USA
- Biochemistry and Molecular Biology Department, Michigan State University, East Lansing, Michigan, 48824, USA
| | - David M Kramer
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, 48824, USA
- Biochemistry and Molecular Biology Department, Michigan State University, East Lansing, Michigan, 48824, USA
| | - Berkley Walker
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, 48824, USA
- Department of Plant Biology, Michigan State University, East Lansing, Michigan, 48824, USA
| | - Federica Brandizzi
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, 48824, USA
- Department of Plant Biology, Michigan State University, East Lansing, Michigan, 48824, USA
- DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, Michigan, 48824, USA
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3
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Kandoi D, Ruhil K, Govindjee G, Tripathy BC. Overexpression of cytoplasmic C 4 Flaveria bidentis carbonic anhydrase in C 3 Arabidopsis thaliana increases amino acids, photosynthetic potential, and biomass. PLANT BIOTECHNOLOGY JOURNAL 2022; 20:1518-1532. [PMID: 35467074 PMCID: PMC9342616 DOI: 10.1111/pbi.13830] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 04/15/2022] [Accepted: 04/18/2022] [Indexed: 05/20/2023]
Abstract
An important method to improve photosynthesis in C3 crops, such as rice and wheat, is to transfer efficient C4 characters to them. Here, cytosolic carbonic anhydrase (CA: βCA3) of the C4 Flaveria bidentis (Fb) was overexpressed under the control of 35 S promoter in Arabidopsis thaliana, a C3 plant, to enhance its photosynthetic efficiency. Overexpression of CA resulted in a better supply of the substrate HCO3- for the endogenous phosphoenolpyruvate carboxylase in the cytosol of the overexpressers, and increased its activity for generating malate that feeds into the tricarboxylic acid cycle. This provided additional carbon skeleton for increased synthesis of amino acids aspartate, asparagine, glutamate, and glutamine. Increased amino acids contributed to higher protein content in the transgenics. Furthermore, expression of FbβCA3 in Arabidopsis led to a better growth due to expression of several genes leading to higher chlorophyll content, electron transport, and photosynthetic carbon assimilation in the transformants. Enhanced CO2 assimilation resulted in increased sugar and starch content, and plant dry weight. In addition, transgenic plants had lower stomatal conductance, reduced transpiration rate, and higher water-use efficiency. These results, taken together, show that expression of C4 CA in the cytosol of a C3 plant can indeed improve its photosynthetic capacity with enhanced water-use efficiency.
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Affiliation(s)
- Deepika Kandoi
- School of Life SciencesJawaharlal Nehru UniversityNew DelhiIndia
| | - Kamal Ruhil
- School of Life SciencesJawaharlal Nehru UniversityNew DelhiIndia
| | - Govindjee Govindjee
- Department of Plant BiologyDepartment of Biochemistry, and Center of Biophysics & Quantitative BiologyUniversity of Illinois at Urbana‐ChampaignUrbanaILUSA
| | - Baishnab C. Tripathy
- School of Life SciencesJawaharlal Nehru UniversityNew DelhiIndia
- Department of BiotechnologySharda UniversityGreater NoidaUPIndia
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4
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DiMario RJ, Giuliani R, Ubierna N, Slack AD, Cousins AB, Studer AJ. Lack of leaf carbonic anhydrase activity eliminates the C 4 carbon-concentrating mechanism requiring direct diffusion of CO 2 into bundle sheath cells. PLANT, CELL & ENVIRONMENT 2022; 45:1382-1397. [PMID: 35233800 DOI: 10.1111/pce.14291] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 10/13/2021] [Accepted: 10/30/2021] [Indexed: 06/14/2023]
Abstract
Carbonic anhydrase (CA) performs the first enzymatic step of C4 photosynthesis by catalysing the reversible hydration of dissolved CO2 that diffuses into mesophyll cells from intercellular airspaces. This CA-catalysed reaction provides the bicarbonate used by phosphoenolpyruvate carboxylase to generate products that flow into the C4 carbon-concentrating mechanism (CCM). It was previously demonstrated that the Zea mays ca1ca2 double mutant lost 97% of leaf CA activity, but there was little difference in the growth phenotype under ambient CO2 partial pressures (pCO2 ). We hypothesise that since CAs are among the fastest enzymes, minimal activity from a third CA, CA8, can provide the inorganic carbon needed to drive C4 photosynthesis. We observed that removing CA8 from the maize ca1ca2 background resulted in plants that had 0.2% of wild-type leaf CA activity. These ca1ca2ca8 plants had reduced photosynthetic parameters and could only survive at elevated pCO2 . Photosynthetic and carbon isotope analysis combined with modelling of photosynthesis and carbon isotope discrimination was used to determine if ca1ca2ca8 plants had a functional C4 cycle or were relying on direct CO2 diffusion to ribulose 1,5-bisphosphate carboxylase/oxygenase within bundle sheath cells. The results suggest that leaf CA activity in ca1ca2ca8 plants was not sufficient to sustain the C4 CCM.
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Affiliation(s)
- Robert J DiMario
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
| | - Rita Giuliani
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
| | - Nerea Ubierna
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
| | - Aaron D Slack
- Department of Crop Sciences, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
| | - Anthony J Studer
- Department of Crop Sciences, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
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5
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Crawford JD, Cousins AB. Limitation of C4 photosynthesis by low carbonic anhydrase activity increases with temperature but does not influence mesophyll CO2 conductance. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:927-938. [PMID: 34698863 DOI: 10.1093/jxb/erab464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 10/23/2021] [Indexed: 06/13/2023]
Abstract
The CO2-concentrating mechanism (CCM) in C4 plants is initiated by the uptake of bicarbonate (HCO3-) via phosphoenolpyruvate carboxylase (PEPC). Generation of HCO3- for PEPC is determined by the interaction between mesophyll CO2 conductance and the hydration of CO2 to HCO3- by carbonic anhydrase (CA). Genetic reduction of CA was previously shown not to limit C4 photosynthesis under ambient atmospheric partial pressures of CO2 (pCO2). However, CA activity varies widely across C4 species and it is unknown if there are specific environmental conditions (e.g. high temperature) where CA may limit HCO3- production for C4 photosynthesis. Additionally, CA activity has been suggested to influence mesophyll conductance, but this has not been experimentally tested. We hypothesize that CA activity can limit PEPC at high temperatures, particularly at low pCO2, but does not directly influence gm. Here we tested the influence of genetically reduced CA activity on photosynthesis and gm in the C4 plant Zea mays under a range of pCO2 and temperatures. Reduced CA activity limited HCO3- production for C4 photosynthesis at low pCO2 as temperatures increased, but did not influence mesophyll conductance. Therefore, high leaf CA activity may enhance C4 photosynthesis under high temperature when stomatal conductance restricts the availability of atmospheric CO2.
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Affiliation(s)
- Joseph D Crawford
- School of Biological Sciences, Washington State University, Pullman, WA, USA
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA, USA
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6
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Momayyezi M, McKown AD, Bell SCS, Guy RD. Emerging roles for carbonic anhydrase in mesophyll conductance and photosynthesis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 101:831-844. [PMID: 31816145 DOI: 10.1111/tpj.14638] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2019] [Revised: 11/17/2019] [Accepted: 11/25/2019] [Indexed: 05/24/2023]
Abstract
Carbonic anhydrase (CA) is an abundant protein in most photosynthesizing organisms and higher plants. This review paper considers the physiological importance of the more abundant CA isoforms in photosynthesis, through their effects on CO2 diffusion and other processes in photosynthetic organisms. In plants, CA has multiple isoforms in three different families (α, β and γ) and is mainly known to catalyze the CO2↔HCO3- equilibrium. This reversible conversion has a clear role in photosynthesis, primarily through sustaining the CO2 concentration at the site of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Despite showing the same major reaction mechanism, the three main CA families are evolutionarily distinct. For different CA isoforms, cellular localization and total gene expression as a function of developmental stage are predicted to determine the role of each family in relation to the net assimilation rate. Reaction-diffusion modeling and observational evidence support a role for CA activity in reducing resistance to CO2 diffusion inside mesophyll cells by facilitating CO2 transfer in both gas and liquid phases. In addition, physical and/or biochemical interactions between CAs and other membrane-bound compartments, for example aquaporins, are suggested to trigger a CO2 -sensing response by stomatal movement. In response to environmental stresses, changes in the expression level of CAs and/or stimulated deactivation of CAs may correspond with lower photosynthetic capacity. We suggest that further studies should focus on the dynamics of the relationship between the activity of CAs (with different subcellular localization, abundance and gene expression) and limitations due to CO2 diffusivity through the mesophyll and supply of CO2 to photosynthetic reactions.
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Affiliation(s)
- Mina Momayyezi
- Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, 2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada
- Department of Viticulture and Enology, University of California, Davis, CA, 95616, USA
| | - Athena D McKown
- Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, 2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada
| | - Shannon C S Bell
- Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, 2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada
| | - Robert D Guy
- Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, 2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada
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7
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Ogée J, Wingate L, Genty B. Estimating Mesophyll Conductance from Measurements of C 18OO Photosynthetic Discrimination and Carbonic Anhydrase Activity. PLANT PHYSIOLOGY 2018; 178:728-752. [PMID: 30104255 PMCID: PMC6181052 DOI: 10.1104/pp.17.01031] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 07/26/2018] [Indexed: 05/20/2023]
Abstract
Carbonic anhydrase (CA) activity in leaves catalyzes the 18O exchange between CO2 and water during photosynthesis. This feature has been used to estimate the mesophyll conductance to CO2 (g m) from measurements of online C18OO photosynthetic discrimination (∆18O). Based on CA assays on leaf extracts, it has been argued that CO2 in mesophyll cells should be in isotopic equilibrium with water in most C3 species as well as many C4 dicot species. However, this seems incompatible with ∆18O data that would indicate a much lower degree of equilibration, especially in C4 plants under high light intensity. This apparent contradiction is resolved here using a new model of C3 and C4 photosynthetic discrimination that includes competition between CO2 hydration and carboxylation and the contribution of respiratory fluxes. This new modeling framework is used to revisit previously published data sets on C3 and C4 species, including CA-deficient plants. We conclude that (1) newly ∆18O-derived g m values are usually close but significantly higher (typically 20% and up to 50%) than those derived assuming full equilibration and (2) despite the uncertainty associated with the respiration rate in light, or the water isotope gradient between mesophyll and bundle sheath cells, robust estimates of ∆18O-derived g m can be achieved in both C3 and C4 plants.
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Affiliation(s)
- Jérôme Ogée
- Institut National de la Recherche Agronomique, Bordeaux Sciences Agro, Unité Mixte de Recherche 1361, Interactions Sol-Plante-Atmosphère, 33140 Villenave d'Ornon, France
| | - Lisa Wingate
- Institut National de la Recherche Agronomique, Bordeaux Sciences Agro, Unité Mixte de Recherche 1361, Interactions Sol-Plante-Atmosphère, 33140 Villenave d'Ornon, France
| | - Bernard Genty
- Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique-Université Aix-Marseille, Unité Mixte de Recherche 7265, Biosciences and Biotechnologies Institute, 13108 Saint-Paul-lez-Durance, France
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8
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Kolbe AR, Cousins AB. Mesophyll conductance in Zea mays responds transiently to CO 2 availability: implications for transpiration efficiency in C 4 crops. THE NEW PHYTOLOGIST 2018; 217:1463-1474. [PMID: 29220090 DOI: 10.1111/nph.14942] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 11/07/2017] [Indexed: 06/07/2023]
Abstract
Mesophyll conductance (gm ) describes the movement of CO2 from the intercellular air spaces below the stomata to the site of initial carboxylation in the mesophyll. In contrast with C3 -gm , little is currently known about the intraspecific variation in C4 -gm or its responsiveness to environmental stimuli. To address these questions, gm was measured on five maize (Zea mays) lines in response to CO2 , employing three different estimates of gm . Each of the methods indicated a significant response of gm to CO2 . Estimates of gm were similar between methods at ambient and higher CO2 , but diverged significantly at low partial pressures of CO2 . These differences are probably driven by incomplete chemical and isotopic equilibrium between CO2 and bicarbonate under these conditions. Carbonic anhydrase and phosphoenolpyruvate carboxylase in vitro activity varied significantly despite similar values of gm and leaf anatomical traits. These results provide strong support for a CO2 response of gm in Z. mays, and indicate that gm in maize is probably driven by anatomical constraints rather than by biochemical limitations. The CO2 response of gm indicates a potential role for facilitated diffusion in C4 -gm . These results also suggest that water-use efficiency could be enhanced in C4 species by targeting gm .
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Affiliation(s)
- Allison R Kolbe
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
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9
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Osborn HL, Alonso-Cantabrana H, Sharwood RE, Covshoff S, Evans JR, Furbank RT, von Caemmerer S. Effects of reduced carbonic anhydrase activity on CO2 assimilation rates in Setaria viridis: a transgenic analysis. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:299-310. [PMID: 27702996 PMCID: PMC5853810 DOI: 10.1093/jxb/erw357] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 09/05/2016] [Indexed: 05/22/2023]
Abstract
In C4 species, the major β-carbonic anhydrase (β-CA) localized in the mesophyll cytosol catalyses the hydration of CO2 to HCO3-, which phosphoenolpyruvate carboxylase uses in the first step of C4 photosynthesis. To address the role of CA in C4 photosynthesis, we generated transgenic Setaria viridis depleted in β-CA. Independent lines were identified with as little as 13% of wild-type CA. No photosynthetic defect was observed in the transformed lines at ambient CO2 partial pressure (pCO2). At low pCO2, a strong correlation between CO2 assimilation rates and CA hydration rates was observed. C18O16O isotope discrimination was used to estimate the mesophyll conductance to CO2 diffusion from the intercellular air space to the mesophyll cytosol (gm) in control plants, which allowed us to calculate CA activities in the mesophyll cytosol (Cm). This revealed a strong relationship between the initial slope of the response of the CO2 assimilation rate to cytosolic pCO2 (ACm) and cytosolic CA activity. However, the relationship between the initial slope of the response of CO2 assimilation to intercellular pCO2 (ACi) and cytosolic CA activity was curvilinear. This indicated that in S. viridis, mesophyll conductance may be a contributing limiting factor alongside CA activity to CO2 assimilation rates at low pCO2.
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Affiliation(s)
- Hannah L Osborn
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT 2601, Australia
| | - Hugo Alonso-Cantabrana
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT 2601, Australia
| | - Robert E Sharwood
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT 2601, Australia
| | - Sarah Covshoff
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, UK
| | - John R Evans
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT 2601, Australia
| | - Robert T Furbank
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT 2601, Australia
| | - Susanne von Caemmerer
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT 2601, Australia
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10
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Barbour MM. Understanding regulation of leaf internal carbon and water transport using online stable isotope techniques. THE NEW PHYTOLOGIST 2017; 213:83-88. [PMID: 27651090 DOI: 10.1111/nph.14171] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 07/12/2016] [Indexed: 06/06/2023]
Abstract
83 I. 83 II. 84 III. 84 IV. 85 V. 86 VI. 86 VII. 86 87 References 87 SUMMARY: The balance of carbon dioxide (CO2 ) and water vapour exchange between leaves and the atmosphere is strongly controlled by stomatal conductance. However, the influence of transport processes within leaves has recently been gaining prominence. Stable isotope techniques are at the forefront of understanding transport within leaves and the recent development of online, real-time optical isotope analysers has paved the way for new questions to be asked. In this insight, I outline these new techniques and the questions they can potentially address, including assessing possible coordination between mesophyll conductance to CO2 and leaf hydraulic conductance.
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Affiliation(s)
- Margaret M Barbour
- Centre for Carbon, Water and Food, the University of Sydney, 380 Werombi Road, Brownlow Hill, Sydney, NSW, 2570, Australia
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11
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Liu HT, Gong XY, Schäufele R, Yang F, Hirl RT, Schmidt A, Schnyder H. Nitrogen fertilization and δ 18 O of CO 2 have no effect on 18 O-enrichment of leaf water and cellulose in Cleistogenes squarrosa (C 4 ) - is VPD the sole control? PLANT, CELL & ENVIRONMENT 2016; 39:2701-2712. [PMID: 27576868 DOI: 10.1111/pce.12824] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 08/23/2016] [Accepted: 08/24/2016] [Indexed: 06/06/2023]
Abstract
The oxygen isotope composition of cellulose (δ18 OCel ) archives hydrological and physiological information. Here, we assess previously unexplored direct and interactive effects of the δ18 O of CO2 (δ18 OCO2 ), nitrogen (N) fertilizer supply and vapour pressure deficit (VPD) on δ18 OCel , 18 O-enrichment of leaf water (Δ18 OLW ) and cellulose (Δ18 OCel ) relative to source water, and pex px , the proportion of oxygen in cellulose that exchanged with unenriched water at the site of cellulose synthesis, in a C4 grass (Cleistogenes squarrosa). δ18 OCO2 and N supply, and their interactions with VPD, had no effect on δ18 OCel , Δ18 OLW , Δ18 OCel and pex px . Δ18 OCel and Δ18 OLW increased with VPD, while pex px decreased. That VPD-effect on pex px was supported by sensitivity tests to variation of Δ18 OLW and the equilibrium fractionation factor between carbonyl oxygen and water. N supply altered growth and morphological features, but not 18 O relations; conversely, VPD had no effect on growth or morphology, but controlled 18 O relations. The work implies that reconstructions of VPD from Δ18 OCel would overestimate amplitudes of VPD variation, at least in this species, if the VPD-effect on pex px is ignored. Progress in understanding the relationship between Δ18 OLW and Δ18 OCel will require separate investigations of pex and px and of their responses to environmental conditions.
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Affiliation(s)
- Hai Tao Liu
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany
| | - Xiao Ying Gong
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany
| | - Rudi Schäufele
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany
| | - Fang Yang
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany
| | - Regina Theresia Hirl
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany
| | - Anja Schmidt
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany
| | - Hans Schnyder
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany
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12
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Song X, Barbour MM. Leaf water oxygen isotope measurement by direct equilibration. THE NEW PHYTOLOGIST 2016; 211:1120-1128. [PMID: 27147584 DOI: 10.1111/nph.13962] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 03/07/2016] [Indexed: 06/05/2023]
Abstract
The oxygen isotope composition of leaf water imparts a signal to a range of molecules in the atmosphere and biosphere, but has been notoriously difficult to measure in studies requiring a large number of samples as a consequence of the labour-intensive extraction step. We tested a method of direct equilibration of water in fresh leaf samples with CO2 , and subsequent oxygen isotope analysis on an optical spectrometer. The oxygen isotope composition of leaf water measured by the direct equilibration technique was strongly linearly related to that of cryogenically extracted leaf water in paired samples for a wide range of species with differing anatomy, with an R(2) of 0.95. The somewhat more enriched values produced by the direct equilibration method may reflect lack of full equilibration with unenriched water in the vascular bundles, but the strong relationship across a wide range of species suggests that this difference can be adequately corrected for using a simple linear relationship.
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Affiliation(s)
- Xin Song
- Centre for Carbon, Water and Food, The University of Sydney, 380 Werombi Road, Brownlow Hill, NSW, 2570, Australia
| | - Margaret M Barbour
- Centre for Carbon, Water and Food, The University of Sydney, 380 Werombi Road, Brownlow Hill, NSW, 2570, Australia
- Landcare Research, PO Box 40, Lincoln, 7640, New Zealand
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13
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Barbour MM, Evans JR, Simonin KA, von Caemmerer S. Online CO2 and H2 O oxygen isotope fractionation allows estimation of mesophyll conductance in C4 plants, and reveals that mesophyll conductance decreases as leaves age in both C4 and C3 plants. THE NEW PHYTOLOGIST 2016; 210:875-89. [PMID: 26778088 DOI: 10.1111/nph.13830] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 11/30/2015] [Indexed: 05/09/2023]
Abstract
Mesophyll conductance significantly, and variably, limits photosynthesis but we currently have no reliable method of measurement for C4 plants. An online oxygen isotope technique was developed to allow quantification of mesophyll conductance in C4 plants and to provide an alternative estimate in C3 plants. The technique is compared to an established carbon isotope method in three C3 species. Mesophyll conductance of C4 species was similar to that in the C3 species measured, and declined in both C4 and C3 species as leaves aged from fully expanded to senescing. In cotton leaves, simultaneous measurement of carbon and oxygen isotope discrimination allowed the partitioning of total conductance to the chloroplasts into cell wall and plasma membrane versus chloroplast membrane components, if CO2 was assumed to be isotopically equilibrated with cytosolic water, and the partitioning remained stable with leaf age. The oxygen isotope technique allowed estimation of mesophyll conductance in C4 plants and, when combined with well-established carbon isotope techniques, may provide additional information on mesophyll conductance in C3 plants.
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Affiliation(s)
- Margaret M Barbour
- Faculty of Agriculture and Environment, The University of Sydney, Private Bag 4011, Narellan, NSW, 2567, Australia
| | - John R Evans
- Research School of Biology, The Australian National University, Acton, ACT, 0200, Australia
| | - Kevin A Simonin
- Department of Biology, San Francisco State University, San Francisco, CA, 94132, USA
| | - Susanne von Caemmerer
- Research School of Biology, The Australian National University, Acton, ACT, 0200, Australia
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14
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Loucos KE, Simonin KA, Song X, Barbour MM. Observed relationships between leaf H218O Péclet effective length and leaf hydraulic conductance reflect assumptions in Craig-Gordon model calculations. TREE PHYSIOLOGY 2015; 35:16-26. [PMID: 25576755 DOI: 10.1093/treephys/tpu110] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Stable oxygen isotope techniques may be a useful tool to investigate the pathways of water movement within leaves. However, implementation of such methods is limited due to uncertainty in the effective path length (L) for the Péclet effect in leaf water enrichment models. Previous studies have found relationships between L and physiological parameters such as transpiration rate (E) and leaf hydraulic conductance (k(leaf)) both within and between species. However, these studies relied on assumptions in their calculation of L, which were not directly tested. Eucalyptus paniculata Smith was used to evaluate the relationships between L, k(leaf) and E under differing water availability and a range of leaf temperatures. Coupled gas exchange and transpiration isotope measurements allowed previous assumptions to be directly tested. L was significantly and negatively related to both k(leaf) and E when the isotopic signature of water vapour was assumed to be in equilibrium with source water, was equivalent to the room vapour or equal to source water. However, the relationship between L and k(leaf) was non-significant when measured δ( 18)O of transpired vapour was used and disappeared entirely when non-steady-state leaves were excluded, and when evaporation site water was calculated from coupled gas exchange and transpiration isotope values. These results suggest that great care must be taken when calculating L, particularly regarding assumptions of isotopic steady state and δ( 18)O of vapour. Previous suggestions of changes in pathways for water movement as transpiration rate varied need to be reassessed in light of these observations.
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Affiliation(s)
- Karen E Loucos
- Centre for Carbon, Water and Food, Faculty of Agriculture and Environment, The University of Sydney, 380 Werombi Rd, NSW 2570, Australia
| | - Kevin A Simonin
- Centre for Carbon, Water and Food, Faculty of Agriculture and Environment, The University of Sydney, 380 Werombi Rd, NSW 2570, Australia Current address: Department of Biology, San Francisco State University, San Francisco, CA 94132, USA
| | - Xin Song
- Centre for Carbon, Water and Food, Faculty of Agriculture and Environment, The University of Sydney, 380 Werombi Rd, NSW 2570, Australia
| | - Margaret M Barbour
- Centre for Carbon, Water and Food, Faculty of Agriculture and Environment, The University of Sydney, 380 Werombi Rd, NSW 2570, Australia
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15
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Barthel M, Sturm P, Hammerle A, Buchmann N, Gentsch L, Siegwolf R, Knohl A. Soil H₂¹⁸O labelling reveals the effect of drought on C¹⁸OO fluxes to the atmosphere. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:5783-93. [PMID: 25100825 DOI: 10.1093/jxb/eru312] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Above- and belowground processes in plants are tightly coupled via carbon and water fluxes through the soil-plant-atmosphere system. The oxygen isotopic composition of atmospheric CO₂ and water vapour (H₂Ov) provides a valuable tool for investigating the transport and cycling of carbon and water within this system. However, detailed studies on the coupling between ecosystem components and environmental drivers are sparse. Therefore, we conducted a H2 (18)O-labelling experiment to investigate the effect of drought on the speed of the link between below- and aboveground processes and its subsequent effect on C(18)OO released by leaves and soils. A custom-made chamber system, separating shoot from soil compartments, allowed separate measurements of shoot- and soil-related processes under controlled conditions. Gas exchange of oxygen stable isotopes in CO₂ and H₂Ov served as the main tool of investigation and was monitored in real time on Fagus sylvatica saplings using laser spectroscopy. H₂(18)O-labelling showed that drought caused a slower transport of water molecules from soil to shoot, which was indicated by its direct derivation from independently measured concentrations and (18)O/(16)O ratios of CO₂ and H₂Ov, respectively. Furthermore, drought reduced the (18)O equilibrium between H₂O and CO₂ at the shoot level, resulting in less-enriched C(18)OO fluxes from leaf to atmosphere compared with control plants. Compared with the shoot, (18)O equilibrium was not instantaneous in the soil and no drought effect was apparent.
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Affiliation(s)
- Matti Barthel
- Ecosystems and Global Change, Landcare Research, P.O. Box 69040, Lincoln 7640, New Zealand Institute of Agricultural Sciences, ETH Zürich, Universitätsstrasse 2, 8092 Zurich, Switzerland
| | - Patrick Sturm
- Institute of Agricultural Sciences, ETH Zürich, Universitätsstrasse 2, 8092 Zurich, Switzerland
| | - Albin Hammerle
- Institute of Agricultural Sciences, ETH Zürich, Universitätsstrasse 2, 8092 Zurich, Switzerland Institute of Ecology, University of Innsbruck, Sternwartestrasse 15, 6020 Innsbruck, Austria
| | - Nina Buchmann
- Institute of Agricultural Sciences, ETH Zürich, Universitätsstrasse 2, 8092 Zurich, Switzerland
| | - Lydia Gentsch
- Institute of Agricultural Sciences, ETH Zürich, Universitätsstrasse 2, 8092 Zurich, Switzerland Chair of Bioclimatology, Georg-August University of Göttingen, Büsgenweg 2, D-37077 Göttingen, Germany
| | - Rolf Siegwolf
- Laboratory for Atmospheric Chemistry/Stable Isotopes & Ecosystem Fluxes, PSI - Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Alexander Knohl
- Institute of Agricultural Sciences, ETH Zürich, Universitätsstrasse 2, 8092 Zurich, Switzerland Chair of Bioclimatology, Georg-August University of Göttingen, Büsgenweg 2, D-37077 Göttingen, Germany
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16
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Kromdijk J, Ubierna N, Cousins AB, Griffiths H. Bundle-sheath leakiness in C4 photosynthesis: a careful balancing act between CO2 concentration and assimilation. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:3443-57. [PMID: 24755278 DOI: 10.1093/jxb/eru157] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Crop species with the C4 photosynthetic pathway are generally characterized by high productivity, especially in environmental conditions favouring photorespiration. In comparison with the ancestral C3 pathway, the biochemical and anatomical modifications of the C4 pathway allow spatial separation of primary carbon acquisition in mesophyll cells and subsequent assimilation in bundle-sheath cells. The CO2-concentrating C4 cycle has to operate in close coordination with CO2 reduction via the Calvin-Benson-Bassham (CBB) cycle in order to keep the C4 pathway energetically efficient. The gradient in CO2 concentration between bundle-sheath and mesophyll cells facilitates diffusive leakage of CO2. This rate of bundle-sheath CO2 leakage relative to the rate of phosphoenolpyruvate carboxylation (termed leakiness) has been used to probe the balance between C4 carbon acquisition and subsequent reduction as a result of environmental perturbations. When doing so, the correct choice of equations to derive leakiness from stable carbon isotope discrimination (Δ(13)C) during gas exchange is critical to avoid biased results. Leakiness responses to photon flux density, either short-term (during measurements) or long-term (during growth and development), can have important implications for C4 performance in understorey light conditions. However, recent reports show leakiness to be subject to considerable acclimation. Additionally, the recent discovery of two decarboxylating C4 cycles operating in parallel in Zea mays suggests that flexibility in the transported C4 acid and associated decarboxylase could also aid in maintaining C4/CBB balance in a changing environment. In this paper, we review improvements in methodology to estimate leakiness, synthesize reports on bundle-sheath leakiness, discuss different interpretations, and highlight areas where future research is necessary.
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Affiliation(s)
- Johannes Kromdijk
- Institute for Genomic Biology, University of Illinois, 1206W Gregory drive, Urbana, IL 61801, USA
| | - Nerea Ubierna
- Research School of Biology, The Australian National University, Canberra, ACT, Australia
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA99164-4236, USA
| | - Howard Griffiths
- Physiological Ecology Group, Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB23EA, UK
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17
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Studer AJ, Gandin A, Kolbe AR, Wang L, Cousins AB, Brutnell TP. A Limited Role for Carbonic Anhydrase in C4 Photosynthesis as Revealed by a ca1ca2 Double Mutant in Maize. PLANT PHYSIOLOGY 2014; 165:608-617. [PMID: 24706552 PMCID: PMC4044840 DOI: 10.1104/pp.114.237602] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 04/03/2014] [Indexed: 05/19/2023]
Abstract
Carbonic anhydrase (CA) catalyzes the first biochemical step of the carbon-concentrating mechanism of C4 plants, and in C4 monocots it has been suggested that CA activity is near limiting for photosynthesis. Here, we test this hypothesis through the characterization of transposon-induced mutant alleles of Ca1 and Ca2 in maize (Zea mays). These two isoforms account for more than 85% of the CA transcript pool. A significant change in isotopic discrimination is observed in mutant plants, which have as little as 3% of wild-type CA activity, but surprisingly, photosynthesis is not reduced under current or elevated CO2 partial pressure (pCO2). However, growth and rates of photosynthesis under subambient pCO2 are significantly impaired in the mutants. These findings suggest that, while CA is not limiting for C4 photosynthesis in maize at current pCO2, it likely maintains high rates of photosynthesis when CO2 availability is reduced. Current atmospheric CO2 levels now exceed 400 ppm (approximately 40.53 Pa) and contrast with the low-pCO2 conditions under which C4 plants expanded their range approximately 10 million years ago, when the global atmospheric CO2 was below 300 ppm (approximately 30.4 Pa). Thus, as CO2 levels continue to rise, selective pressures for high levels of CA may be limited to arid climates where stomatal closure reduces CO2 availability to the leaf.
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Affiliation(s)
- Anthony J Studer
- Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (A.J.S., A.R.K., L.W., T.P.B.); andSchool of Biological Sciences, Washington State University, Pullman, Washington 99164 (A.G., A.B.C.)
| | - Anthony Gandin
- Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (A.J.S., A.R.K., L.W., T.P.B.); andSchool of Biological Sciences, Washington State University, Pullman, Washington 99164 (A.G., A.B.C.)
| | - Allison R Kolbe
- Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (A.J.S., A.R.K., L.W., T.P.B.); andSchool of Biological Sciences, Washington State University, Pullman, Washington 99164 (A.G., A.B.C.)
| | - Lin Wang
- Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (A.J.S., A.R.K., L.W., T.P.B.); andSchool of Biological Sciences, Washington State University, Pullman, Washington 99164 (A.G., A.B.C.)
| | - Asaph B Cousins
- Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (A.J.S., A.R.K., L.W., T.P.B.); andSchool of Biological Sciences, Washington State University, Pullman, Washington 99164 (A.G., A.B.C.)
| | - Thomas P Brutnell
- Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (A.J.S., A.R.K., L.W., T.P.B.); andSchool of Biological Sciences, Washington State University, Pullman, Washington 99164 (A.G., A.B.C.)
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18
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Busch FA, Sage TL, Cousins AB, Sage RF. C3 plants enhance rates of photosynthesis by reassimilating photorespired and respired CO2. PLANT, CELL & ENVIRONMENT 2013; 36:200-12. [PMID: 22734462 DOI: 10.1111/j.1365-3040.2012.02567.x] [Citation(s) in RCA: 146] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Photosynthetic carbon gain in plants using the C(3) photosynthetic pathway is substantially inhibited by photorespiration in warm environments, particularly in atmospheres with low CO(2) concentrations. Unlike C(4) plants, C(3) plants are thought to lack any mechanism to compensate for the loss of photosynthetic productivity caused by photorespiration. Here, for the first time, we demonstrate that the C(3) plants rice and wheat employ a specific mechanism to trap and reassimilate photorespired CO(2) . A continuous layer of chloroplasts covering the portion of the mesophyll cell periphery that is exposed to the intercellular air space creates a diffusion barrier for CO(2) exiting the cell. This facilitates the capture and reassimilation of photorespired CO(2) in the chloroplast stroma. In both species, 24-38% of photorespired and respired CO(2) were reassimilated within the cell, thereby boosting photosynthesis by 8-11% at ambient atmospheric CO(2) concentration and 17-33% at a CO(2) concentration of 200 µmol mol(-1) . Widespread use of this mechanism in tropical and subtropical C(3) plants could explain why the diversity of the world's C(3) flora, and dominance of terrestrial net primary productivity, was maintained during the Pleistocene, when atmospheric CO(2) concentrations fell below 200 µmol mol(-1) .
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Affiliation(s)
- Florian A Busch
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.
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19
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Stimler K, Berry JA, Yakir D. Effects of carbonyl sulfide and carbonic anhydrase on stomatal conductance. PLANT PHYSIOLOGY 2012; 158:524-30. [PMID: 22106096 PMCID: PMC3252075 DOI: 10.1104/pp.111.185926] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The potential use of carbonyl sulfide (COS) as tracer of CO(2) flux into the land biosphere stimulated research on COS interactions with leaves during gas exchange. We carried out leaf gas-exchange measurements of COS and CO(2) in 22 plant species representing deciduous and evergreen trees, grasses, and shrubs, under a range of light intensities, using mid-infrared laser spectroscopy. A narrow range in the normalized ratio of the net uptake rates of COS (A(s)) and CO(2) (A(c)), leaf relative uptake (A(s)/A(c) × [CO(2)]/[COS]), was observed, with a mean value of 1.61 ± 0.26, which is advantageous to the use of COS in photosynthesis research. Notably, increasing COS concentrations between 250 and 2,800 pmol mol(-1) (enveloping atmospheric levels) enhanced stomatal conductance (g(s)) to a variable extent in most plants examined (up to a normalized enhancement factor [ f(e) = (g(s-max) - g(s-min))/g(s-min)] of 1). This enhancement was completely abolished in carbonic anhydrase (CA)-deficient antisense lines of both C3 and C4 plants. We suggest that the stomatal response is mediated by CA and may involve hydrogen sulfide formed in the reaction of COS and water with CA. In all species examined, the uptake rates of COS and CO(2) were highly correlated, but there was no relationship between the sensitivity of stomata to COS and the rate of COS uptake (or, by inference, hydrogen sulfide production). The basis for the observed stomatal sensitivity and its variations is still to be determined.
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20
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Kramer DM, Evans JR. The importance of energy balance in improving photosynthetic productivity. PLANT PHYSIOLOGY 2011; 155:70-8. [PMID: 21078862 PMCID: PMC3075755 DOI: 10.1104/pp.110.166652] [Citation(s) in RCA: 319] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Accepted: 11/10/2010] [Indexed: 05/18/2023]
Affiliation(s)
- David M Kramer
- Biochemistry and Molecular Biology and Department of Energy, Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.
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21
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Xiao W, Lee X, Griffis TJ, Kim K, Welp LR, Yu Q. A modeling investigation of canopy-air oxygen isotopic exchange of water vapor and carbon dioxide in a soybean field. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009jg001163] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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22
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Hartard B, Cuntz M, Máguas C, Lakatos M. Water isotopes in desiccating lichens. PLANTA 2009; 231:179-93. [PMID: 19888598 PMCID: PMC2852525 DOI: 10.1007/s00425-009-1038-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Accepted: 10/08/2009] [Indexed: 05/27/2023]
Abstract
The stable isotopic composition of water is routinely used as a tracer to study water exchange processes in vascular plants and ecosystems. To date, no study has focussed on isotope processes in non-vascular, poikilohydric organisms such as lichens and bryophytes. To understand basic isotope exchange processes of non-vascular plants, thallus water isotopic composition was studied in various green-algal lichens exposed to desiccation. The study indicates that lichens equilibrate with the isotopic composition of surrounding water vapour. A model was developed as a proof of concept that accounts for the specific water relations of these poikilohydric organisms. The approach incorporates first their variable thallus water potential and second a compartmentation of the thallus water into two isotopically distinct but connected water pools. Moreover, the results represent first steps towards the development of poikilohydric organisms as a recorder of ambient vapour isotopic composition.
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Affiliation(s)
- Britta Hartard
- Department of Experimental Ecology, University of Kaiserslautern, P.O. Box 3049, Erwin-Schroedinger-Str. 14/262, 67653 Kaiserslautern, Germany
- Stable Isotopes Laboratory, Centre for Environmental Biology, FCUL, University of Lisbon, Campo Grande, 1749-016 Lisbon, Portugal
| | - Matthias Cuntz
- Max-Planck Institute for Biogeochemistry, P.O. Box 100164, 07701 Jena, Germany
- UFZ, Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany
| | - Cristina Máguas
- Stable Isotopes Laboratory, Centre for Environmental Biology, FCUL, University of Lisbon, Campo Grande, 1749-016 Lisbon, Portugal
| | - Michael Lakatos
- Department of Experimental Ecology, University of Kaiserslautern, P.O. Box 3049, Erwin-Schroedinger-Str. 14/262, 67653 Kaiserslautern, Germany
- Stable Isotopes Laboratory, Centre for Environmental Biology, FCUL, University of Lisbon, Campo Grande, 1749-016 Lisbon, Portugal
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23
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Still CJ, Riley WJ, Biraud SC, Noone DC, Buenning NH, Randerson JT, Torn MS, Welker J, White JWC, Vachon R, Farquhar GD, Berry JA. Influence of clouds and diffuse radiation on ecosystem-atmosphere CO2and CO18O exchanges. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2007jg000675] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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24
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Tcherkez G, Farquhar GD. On the effect of heavy water (D 2O) on carbon isotope fractionation in photosynthesis. FUNCTIONAL PLANT BIOLOGY : FPB 2008; 35:201-212. [PMID: 32688774 DOI: 10.1071/fp07282] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2007] [Accepted: 02/18/2008] [Indexed: 06/11/2023]
Abstract
Internal conductance to carbon dioxide is a key aspect of leaf photosynthesis although is still not well understood. It is thought that it comprises two components, namely, a gas phase component (diffusion from intercellular spaces to cell walls) and a liquid phase component (dissolution, diffusion in water, hydration equilibrium). Here we use heavy water (D2O), which is known to slow down CO2 hydration by a factor of nearly three. Using 12C/13C stable isotope techniques and Xanthium strumarium L. leaves, we show that the on-line carbon isotope discrimination (Δ13C, or Δobs) associated with photosynthesis is not significantly decreased by heavy water, and that the internal conductance, estimated with relationships involving the deviation of Δ13C, decreased by 8-40% in 21% O2. It is concluded that in typical conditions, the CO2-hydration equilibrium does not exert an effect on CO2 assimilation larger than 9%. The carbon isotope discrimination associated with CO2 addition to ribulose-1,5,bisphosphate by Rubisco is slightly decreased by heavy water. This effect is proposed to originate from the use of solvent-derived proton/deuteron during the last step of the catalytic cycle of the enzyme (hydration/cleavage).
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Affiliation(s)
- Guillaume Tcherkez
- Plateforme Métabolisme-Métabolome, IFR87, Université Paris-Sud XI, 91405 Orsay, France
| | - Graham D Farquhar
- Environmental Biology Group, Research School of Biological Sciences, Australian National University, Canberra, ACT 2601, Australia
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25
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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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26
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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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27
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Griffiths H, Cousins AB, Badger MR, von Caemmerer S. Discrimination in the dark. Resolving the interplay between metabolic and physical constraints to phosphoenolpyruvate carboxylase activity during the crassulacean acid metabolism cycle. PLANT PHYSIOLOGY 2007; 143:1055-67. [PMID: 17142488 PMCID: PMC1803711 DOI: 10.1104/pp.106.088302] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2006] [Accepted: 11/08/2006] [Indexed: 05/12/2023]
Abstract
A model defining carbon isotope discrimination (delta13C) for crassulacean acid metabolism (CAM) plants was experimentally validated using Kalanchoe daigremontiana. Simultaneous measurements of gas exchange and instantaneous CO2 discrimination (for 13C and 18O) were made from late photoperiod (phase IV of CAM), throughout the dark period (phase I), and into the light (phase II). Measurements of CO2 response curves throughout the dark period revealed changing phosphoenolpyruvate carboxylase (PEPC) capacity. These systematic changes in PEPC capacity were tracked by net CO2 uptake, stomatal conductance, and online delta13C signal; all declined at the start of the dark period, then increased to a maximum 2 h before dawn. Measurements of delta13C were higher than predicted from the ratio of intercellular to external CO2 (p(i)/p(a)) and fractionation associated with CO2 hydration and PEPC carboxylations alone, such that the dark period mesophyll conductance, g(i), was 0.044 mol m(-2) s(-1) bar(-1). A higher estimate of g(i) (0.085 mol m(-2) s(-1) bar(-1)) was needed to account for the modeled and measured delta18O discrimination throughout the dark period. The differences in estimates of g(i) from the two isotope measurements, and an offset of -5.5 per thousand between the 18O content of source and transpired water, suggest spatial variations in either CO2 diffusion path length and/or carbonic anhydrase activity, either within individual cells or across a succulent leaf. Our measurements support the model predictions to show that internal CO2 diffusion limitations within CAM leaves increase delta13C discrimination during nighttime CO2 fixation while reducing delta13C during phase IV. When evaluating the phylogenetic distribution of CAM, carbon isotope composition will reflect these diffusive limitations as well as relative contributions from C3 and C4 biochemistry.
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Affiliation(s)
- Howard Griffiths
- Physiological Ecology Group, Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom.
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