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Zhou L, Xiang X, Ji D, Chen Q, Ma T, Wang J, Liu C. A Carbonic Anhydrase, ZmCA4, Contributes to Photosynthetic Efficiency and Modulates CO2 Signaling Gene Expression by Interacting with Aquaporin ZmPIP2;6 in Maize. PLANT & CELL PHYSIOLOGY 2024; 65:243-258. [PMID: 37955399 DOI: 10.1093/pcp/pcad145] [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: 06/30/2023] [Revised: 11/07/2023] [Accepted: 11/10/2023] [Indexed: 11/14/2023]
Abstract
Carbonic anhydrase (CA) catalyzes the reversible CO2 hydration reaction that produces bicarbonate for phosphoenolpyruvate carboxylase (PEPC). This is the initial step for transmitting the CO2 signal in C4 photosynthesis. However, it remains unknown whether the maize (Zea mays L.) CA gene, ZmCA4, plays a role in the maize photosynthesis process. In our study, we found that ZmCA4 was relatively highly expressed in leaves and localized in the chloroplast and the plasma membrane of mesophyll protoplasts. Knock-out of ZmCA4 reduced CA activity, while overexpression of ZmCA4 increased rubisco activity, as well as the quantum yield and relative electron transport rate in photosystem II. Overexpression of ZmCA4 enhanced maize yield-related traits. Moreover, ZmCA4 interacted with aquaporin ZmPIP2;6 in bimolecular fluorescence complementation and co-immunoprecipitation experiments. The double-knock-out mutant for ZmPIP2;6 and ZmCA4 genes showed reductions in its growth, CA and PEPC activities, assimilation rate and photosystem activity. RNA-Seq analysis revealed that the expression of other ZmCAs, ZmPIPs, as well as CO2 signaling pathway homologous genes, and photosynthetic-related genes was all altered in the double-knock-out mutant compared with the wild type. Altogether, our study's findings point to a critical role of ZmCA4 in determining photosynthetic capacity and modulating CO2 signaling regulation via its interaction with ZmPIP2;6, thus providing insight into the potential genetic value of ZmCA4 for maize yield improvement.
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Affiliation(s)
- Lian Zhou
- Maize Research Institute, College of Agronomy and Biotechnology, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China
- Engineering Research Center of South Upland Agriculture, Ministry of Education, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China
| | - Xiaoqin Xiang
- Maize Research Institute, College of Agronomy and Biotechnology, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China
| | - Dongpu Ji
- Maize Research Institute, College of Agronomy and Biotechnology, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China
| | - Qiulan Chen
- Maize Research Institute, College of Agronomy and Biotechnology, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China
| | - Tengfei Ma
- Maize Research Institute, College of Agronomy and Biotechnology, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China
| | - Jiuguang Wang
- Maize Research Institute, College of Agronomy and Biotechnology, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China
- Engineering Research Center of South Upland Agriculture, Ministry of Education, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China
| | - Chaoxian Liu
- Maize Research Institute, College of Agronomy and Biotechnology, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China
- Engineering Research Center of South Upland Agriculture, Ministry of Education, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China
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Ubierna N, Holloway-Phillips MM, Wingate L, Ogée J, Busch FA, Farquhar GD. Using Carbon Stable Isotopes to Study C 3 and C 4 Photosynthesis: Models and Calculations. Methods Mol Biol 2024; 2790:163-211. [PMID: 38649572 DOI: 10.1007/978-1-0716-3790-6_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
Stable carbon isotopes are a powerful tool to study photosynthesis. Initial applications consisted of determining isotope ratios of plant biomass using mass spectrometry. Subsequently, theoretical models relating C isotope values to gas exchange characteristics were introduced and tested against instantaneous online measurements of 13C photosynthetic discrimination. Beginning in the twenty-first century, laser absorption spectroscopes with sufficient precision for determining isotope mixing ratios became commercially available. This has allowed collection of large data sets at lower cost and with unprecedented temporal resolution. More data and accompanying knowledge have permitted refinement of 13C discrimination model equations, but often at the expense of increased model complexity and difficult parametrization. This chapter describes instantaneous online measurements of 13C photosynthetic discrimination, provides recommendations for experimental setup, and presents a thorough compilation of equations available to researchers. We update our previous 2018 version of this chapter by including recently improved descriptions of (photo)respiratory processes and associated fractionations. We discuss the capabilities and limitations of the diverse 13C discrimination model equations and provide guidance for selecting the model complexity needed for different applications.
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Affiliation(s)
- Nerea Ubierna
- Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Unité Mixte de Recherche (UMR)1391 ISPA, Villenave D'Ornon, France
| | - Meisha-Marika Holloway-Phillips
- Research Unit of Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmendsorf, Switzerland
| | - Lisa Wingate
- Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Unité Mixte de Recherche (UMR)1391 ISPA, Villenave D'Ornon, France
| | - Jérôme Ogée
- Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Unité Mixte de Recherche (UMR)1391 ISPA, Villenave D'Ornon, France
| | - Florian A Busch
- School of Biosciences and The Birmingham Institute of Forest Research, University of Birmingham, Birmingham, UK
| | - Graham D Farquhar
- Research School of Biology, Australian National University, Canberra, ACT, Australia
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Simpson CJC, Singh P, Sogbohossou DEO, Eric Schranz M, Hibberd JM. A rapid method to quantify vein density in C 4 plants using starch staining. PLANT, CELL & ENVIRONMENT 2023; 46:2928-2938. [PMID: 37350263 PMCID: PMC10947256 DOI: 10.1111/pce.14656] [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: 03/15/2023] [Revised: 06/05/2023] [Accepted: 06/13/2023] [Indexed: 06/24/2023]
Abstract
C4 photosynthesis has evolved multiple times in the angiosperms and typically involves alterations to the biochemistry, cell biology and development of leaves. One common modification found in C4 plants compared with the ancestral C3 state is an increase in vein density such that the leaf contains a larger proportion of bundle sheath cells. Recent findings indicate that there may be significant intraspecific variation in traits such as vein density in C4 plants but to use such natural variation for trait-mapping, rapid phenotyping would be required. Here we report a high-throughput method to quantify vein density that leverages the bundle sheath-specific accumulation of starch found in C4 species. Starch staining allowed high-contrast images to be acquired permitting image analysis with MATLAB- and Python-based programmes. The method works for dicotyledons and monocotolydons. We applied this method to Gynandropsis gynandra where significant variation in vein density was detected between natural accessions, and Zea mays where no variation was apparent in the genotypically diverse lines assessed. We anticipate this approach will be useful to map genes controlling vein density in C4 species demonstrating natural variation for this trait.
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Affiliation(s)
| | - Pallavi Singh
- Department of Plant SciencesUniversity of CambridgeCambridgeUK
| | | | - M. Eric Schranz
- Biosystematics GroupWageningen UniversityWageningenThe Netherlands
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4
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Pathare VS, DiMario RJ, Koteyeva N, Cousins AB. Mesophyll conductance response to short-term changes in pCO 2 is related to leaf anatomy and biochemistry in diverse C 4 grasses. THE NEW PHYTOLOGIST 2022; 236:1281-1295. [PMID: 35959528 PMCID: PMC9825963 DOI: 10.1111/nph.18427] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 07/31/2022] [Indexed: 06/15/2023]
Abstract
Mesophyll CO2 conductance (gm ) in C3 species responds to short-term (minutes) changes in environment potentially due to changes in leaf anatomical and biochemical properties and measurement artefacts. Compared with C3 species, there is less information on gm responses to short-term changes in environmental conditions such as partial pressure of CO2 (pCO2 ) across diverse C4 species and the potential determinants of these responses. Using 16 C4 grasses we investigated the response of gm to short-term changes in pCO2 and its relationship with leaf anatomy and biochemistry. In general, gm increased as pCO2 decreased (statistically significant increase in 12 species), with percentage increases in gm ranging from +13% to +250%. Greater increase in gm at low pCO2 was observed in species exhibiting relatively thinner mesophyll cell walls along with greater mesophyll surface area exposed to intercellular air spaces, leaf N, photosynthetic capacity and activities of phosphoenolpyruvate carboxylase and Rubisco. Species with greater CO2 responses of gm were also able to maintain their leaf water-use efficiencies (TEi ) under low CO2 . Our study advances understanding of CO2 response of gm in diverse C4 species, identifies the key leaf traits related to this response and has implications for improving C4 photosynthetic models and TEi through modification of gm .
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Affiliation(s)
- Varsha S. Pathare
- School of Biological SciencesWashington State UniversityPullmanWA99164‐4236USA
| | - Robert J. DiMario
- School of Biological SciencesWashington State UniversityPullmanWA99164‐4236USA
| | - Nuria Koteyeva
- School of Biological SciencesWashington State UniversityPullmanWA99164‐4236USA
- Laboratory of Anatomy and MorphologyV.L. Komarov Botanical Institute of the Russian Academy of Sciences197376St PetersburgRussia
| | - Asaph B. Cousins
- School of Biological SciencesWashington State UniversityPullmanWA99164‐4236USA
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5
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Simpson CJC, Reeves G, Tripathi A, Singh P, Hibberd JM. Using breeding and quantitative genetics to understand the C4 pathway. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:3072-3084. [PMID: 34747993 PMCID: PMC9126733 DOI: 10.1093/jxb/erab486] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Accepted: 11/03/2021] [Indexed: 05/09/2023]
Abstract
Reducing photorespiration in C3 crops could significantly increase rates of photosynthesis and yield. One method to achieve this would be to integrate C4 photosynthesis into C3 species. This objective is challenging as it involves engineering incompletely understood traits into C3 leaves, including complex changes to their biochemistry, cell biology, and anatomy. Quantitative genetics and selective breeding offer underexplored routes to identify regulators of these processes. We first review examples of natural intraspecific variation in C4 photosynthesis as well as the potential for hybridization between C3 and C4 species. We then discuss how quantitative genetic approaches including artificial selection and genome-wide association could be used to better understand the C4 syndrome and in so doing guide the engineering of the C4 pathway into C3 crops.
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Affiliation(s)
- Conor J C Simpson
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Gregory Reeves
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Anoop Tripathi
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Pallavi Singh
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Julian M Hibberd
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
- Correspondence:
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6
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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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7
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Sales CRG, Wang Y, Evers JB, Kromdijk J. Improving C4 photosynthesis to increase productivity under optimal and suboptimal conditions. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:5942-5960. [PMID: 34268575 PMCID: PMC8411859 DOI: 10.1093/jxb/erab327] [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: 03/12/2021] [Accepted: 07/09/2021] [Indexed: 05/05/2023]
Abstract
Although improving photosynthetic efficiency is widely recognized as an underutilized strategy to increase crop yields, research in this area is strongly biased towards species with C3 photosynthesis relative to C4 species. Here, we outline potential strategies for improving C4 photosynthesis to increase yields in crops by reviewing the major bottlenecks limiting the C4 NADP-malic enzyme pathway under optimal and suboptimal conditions. Recent experimental results demonstrate that steady-state C4 photosynthesis under non-stressed conditions can be enhanced by increasing Rubisco content or electron transport capacity, both of which may also stimulate CO2 assimilation at supraoptimal temperatures. Several additional putative bottlenecks for photosynthetic performance under drought, heat, or chilling stress or during photosynthetic induction await further experimental verification. Based on source-sink interactions in maize, sugarcane, and sorghum, alleviating these photosynthetic bottlenecks during establishment and growth of the harvestable parts are likely to improve yield. The expected benefits are also shown to be augmented by the increasing trend in planting density, which increases the impact of photosynthetic source limitation on crop yields.
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Affiliation(s)
- Cristina R G Sales
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
| | - Yu Wang
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Jochem B Evers
- Centre for Crops Systems Analysis (WUR), Wageningen University, Wageningen, The Netherlands
| | - Johannes Kromdijk
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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8
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Adnew GA, Hofmann MEG, Pons TL, Koren G, Ziegler M, Lourens LJ, Röckmann T. Leaf scale quantification of the effect of photosynthetic gas exchange on Δ 47 of CO 2. Sci Rep 2021; 11:14023. [PMID: 34234170 PMCID: PMC8263724 DOI: 10.1038/s41598-021-93092-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 06/15/2021] [Indexed: 11/30/2022] Open
Abstract
The clumped isotope composition (Δ47, the anomaly of the mass 47 isotopologue relative to the abundance expected from a random isotope distribution) of CO2 has been suggested as an additional tracer for gross CO2 fluxes. However, the effect of photosynthetic gas exchange on Δ47 has not been directly determined and two indirect/conceptual studies reported contradicting results. In this study, we quantify the effect of photosynthetic gas exchange on Δ47 of CO2 using leaf cuvette experiments with one C4 and two C3 plants. The experimental results are supported by calculations with a leaf cuvette model. Our results demonstrate the important roles of the Δ47 value of CO2 entering the leaf, kinetic fractionation as CO2 diffuses into, and out of the leaf and CO2–H2O isotope exchange with leaf water. We experimentally confirm the previously suggested dependence of Δ47 of CO2 in the air surrounding a leaf on the stomatal conductance and back-diffusion flux. Gas exchange can enrich or deplete the Δ47 of CO2 depending on the Δ47 of CO2 entering the leaf and the fraction of CO2 exchanged with leaf water and diffused back to the atmosphere, but under typical ambient conditions, it will lead to a decrease in Δ47.
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Affiliation(s)
- Getachew Agmuas Adnew
- Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, The Netherlands.
| | - Magdalena E G Hofmann
- Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, The Netherlands.,Picarro B.V., 's-Hertogenbosch, The Netherlands
| | - Thijs L Pons
- Institute of Environmental Biology, Utrecht University, Utrecht, The Netherlands
| | - Gerbrand Koren
- Meteorology and Air Quality Group, Wageningen University, Wageningen, The Netherlands
| | - Martin Ziegler
- Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands
| | - Lucas J Lourens
- Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands
| | - Thomas Röckmann
- Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, The Netherlands
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9
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Abstract
Since 1893, when the word "photosynthesis" was first coined by Charles Reid Barnes and Conway MacMillan, our understanding of the elements and regulation of this complex process is far from being entirely understood. We aim to review the most relevant advances in photosynthesis research from the last few years and to provide a perspective on the forthcoming research in this field. Recent discoveries related to light sensing, harvesting, and dissipation; kinetics of CO2 fixation; components and regulators of CO2 diffusion through stomata and mesophyll; and genetic engineering for improving photosynthetic and production capacities of crops are addressed.
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Affiliation(s)
- Alicia V Perera-Castro
- Department of Biology, Universitat de les Illes Balears, INAGEA, Palma de Mallorca, Spain
| | - Jaume Flexas
- Department of Biology, Universitat de les Illes Balears, INAGEA, Palma de Mallorca, Spain
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10
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Sonawane BV, Cousins AB. Mesophyll CO 2 conductance and leakiness are not responsive to short- and long-term soil water limitations in the C 4 plant Sorghum bicolor. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 103:1590-1602. [PMID: 32438487 DOI: 10.1111/tpj.14849] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 04/30/2020] [Accepted: 05/05/2020] [Indexed: 05/13/2023]
Abstract
Breeding economically important C4 crops for enhanced whole-plant water-use efficiency (WUEplant ) is needed for sustainable agriculture. WUEplant is a complex trait and an efficient phenotyping method that reports on components of WUEplant , such as intrinsic water-use efficiency (WUEi , the rate of leaf CO2 assimilation relative to water loss via stomatal conductance), is needed. In C4 plants, theoretical models suggest that leaf carbon isotope composition (δ13 C), when the efficiency of the CO2 -concentrating mechanism (leakiness, ϕ) remains constant, can be used to screen for WUEi . The limited information about how ϕ responds to water limitations confines the application of δ13 C for WUEi screening of C4 crops. The current research aimed to test the response of ϕ to short- or long-term moderate water limitations, and the relationship of δ13 C with WUEi and WUEplant , by addressing potential mesophyll CO2 conductance (gm ) and biochemical limitations in the C4 plant Sorghum bicolor. We demonstrate that gm and ϕ are not responsive to short- or long-term water limitations. Additionally, δ13 C was not correlated with gas-exchange estimates of WUEi under short- and long-term water limitations, but showed a significant negative relationship with WUEplant . The observed association between the δ13 C and WUEplant suggests an intrinsic link of δ13 C with WUEi in this C4 plant, and can potentially be used as a screening tool for WUEplant in sorghum.
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Affiliation(s)
- Balasaheb V Sonawane
- 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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11
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Zhu L, Cernusak LA, Song X. Dynamic responses of gas exchange and photochemistry to heat interference during drought in wheat and sorghum. FUNCTIONAL PLANT BIOLOGY : FPB 2020; 47:611-627. [PMID: 32393434 DOI: 10.1071/fp19242] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 01/14/2020] [Indexed: 06/11/2023]
Abstract
Drought and heat stress significantly affect crop growth and productivity worldwide. It is unknown how heat interference during drought affects physiological processes dynamically in crops. Here we focussed on gas exchange and photochemistry in wheat and sorghum in response to simulated heat interference via +15°C of temperature during ~2 week drought and re-watering. Results showed that drought decreased net photosynthesis (Anet), stomatal conductance (gs), maximum velocity of ribulose-1, 5-bisphosphate carboxylase/oxygenase carboxylation (Vcmax) and electron transport rate (J) in both wheat and sorghum. Heat interference did not further reduce Anet or gs. Drought increased non-photochemical quenching (Φnpq), whereas heat interference decreased Φnpq. The δ13C of leaf, stem and roots was higher in drought-treated wheat but lower in drought-treated sorghum. The results suggest that (1) even under drought conditions wheat and sorghum increased or maintained gs for transpirational cooling to alleviate negative effects by heat interference; (2) non-photochemical quenching responded differently to drought and heat stress; (3) wheat and sorghum responded in opposing patterns in δ13C. These findings point to the importance of stomatal regulation under heat crossed with drought stress and could provide useful information on development of better strategies to secure crop production for future climate change.
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Affiliation(s)
- Lingling Zhu
- Shenzhen Key Laboratory of Marine Biological Resources and Ecological Environment, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, China; and Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China
| | - Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, Australia
| | - Xin Song
- Shenzhen Key Laboratory of Marine Biological Resources and Ecological Environment, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, China; and Corresponding author.
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12
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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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13
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Knauer J, Zaehle S, De Kauwe MG, Haverd V, Reichstein M, Sun Y. Mesophyll conductance in land surface models: effects on photosynthesis and transpiration. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 101:858-873. [PMID: 31659806 DOI: 10.1111/tpj.14587] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 10/10/2019] [Accepted: 10/17/2019] [Indexed: 05/08/2023]
Abstract
The CO2 transfer conductance within plant leaves (mesophyll conductance, gm ) is currently not considered explicitly in most land surface models (LSMs), but instead treated implicitly as an intrinsic property of the photosynthetic machinery. Here, we review approaches to overcome this model deficiency by explicitly accounting for gm , which comprises the re-adjustment of photosynthetic parameters and a model describing the variation of gm in dependence of environmental conditions. An explicit representation of gm causes changes in the response of photosynthesis to environmental factors, foremost leaf temperature, and ambient CO2 concentration, which are most pronounced when gm is small. These changes in leaf-level photosynthesis translate into a stronger climate and CO2 response of gross primary productivity (GPP) and transpiration at the global scale. The results from two independent studies show consistent latitudinal patterns of these effects with biggest differences in GPP in the boreal zone (up to ~15%). Transpiration and evapotranspiration show spatially similar, but attenuated, changes compared with GPP. These changes are indirect effects of gm caused by the assumed strong coupling between stomatal conductance and photosynthesis in current LSMs. Key uncertainties in these simulations are the variation of gm with light and the robustness of its temperature response across plant types and growth conditions. Future research activities focusing on the response of gm to environmental factors and its relation to other plant traits have the potential to improve the representation of photosynthesis in LSMs and to better understand its present and future role in the Earth system.
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Affiliation(s)
- Jürgen Knauer
- CSIRO Oceans and Atmosphere, Canberra, ACT, 2601, Australia
- Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, 07745, Jena, Germany
| | - Sönke Zaehle
- Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, 07745, Jena, Germany
- Michael-Stifel Center Jena for Data-Driven and Simulation Science, 07745, Jena, Germany
| | - Martin G De Kauwe
- ARC Centre of Excellence for Climate Extremes and the Climate Change Research Centre, University of New South Wales, Sydney, 2052, NSW, Australia
| | - Vanessa Haverd
- CSIRO Oceans and Atmosphere, Canberra, ACT, 2601, Australia
| | - Markus Reichstein
- Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, 07745, Jena, Germany
- Michael-Stifel Center Jena for Data-Driven and Simulation Science, 07745, Jena, Germany
| | - Ying Sun
- School of Integrative Plant Science, Soil and Crop Sciences Section, Cornell University, Ithaca, NY, 14850, USA
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14
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Pathare VS, Koteyeva N, Cousins AB. Increased adaxial stomatal density is associated with greater mesophyll surface area exposed to intercellular air spaces and mesophyll conductance in diverse C 4 grasses. THE NEW PHYTOLOGIST 2020; 225:169-182. [PMID: 31400232 DOI: 10.1111/nph.16106] [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: 05/23/2019] [Accepted: 08/01/2019] [Indexed: 05/21/2023]
Abstract
Mesophyll conductance (gm ) is the diffusion of CO2 from intercellular air spaces (IAS) to the first site of carboxylation in the mesophyll cells. In C3 species, gm is influenced by diverse leaf structural and anatomical traits; however, little is known about traits affecting gm in C4 species. To address this knowledge gap, we used online oxygen isotope discrimination measurements to estimate gm and microscopy techniques to measure leaf structural and anatomical traits potentially related to gm in 18 C4 grasses. In this study, gm scaled positively with photosynthesis and intrinsic water-use efficiency (TEi ), but not with stomatal conductance. Also, gm was not determined by a single trait but was positively correlated with adaxial stomatal densities (SDada ), stomatal ratio (SR), mesophyll surface area exposed to IAS (Smes ) and leaf thickness. However, gm was not related to abaxial stomatal densities (SDaba ) and mesophyll cell wall thickness (TCW ). Our study suggests that greater SDada and SR increased gm by increasing Smes and creating additional parallel pathways for CO2 diffusion inside mesophyll cells. Thus, SDada , SR and Smes are important determinants of C4 -gm and could be the target traits selected or modified for achieving greater gm and TEi in C4 species.
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Affiliation(s)
- Varsha S Pathare
- School of Biological Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Nuria Koteyeva
- School of Biological Sciences, Washington State University, Pullman, WA, 99164-4236, USA
- Laboratory of Anatomy and Morphology, V.L. Komarov Botanical Institute of the Russian Academy of Sciences, 197376, St Petersburg, Russia
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA, 99164-4236, USA
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15
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Cano FJ, Sharwood RE, Cousins AB, Ghannoum O. The role of leaf width and conductances to CO 2 in determining water use efficiency in C 4 grasses. THE NEW PHYTOLOGIST 2019; 223:1280-1295. [PMID: 31087798 DOI: 10.1111/nph.15920] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 04/28/2019] [Indexed: 05/26/2023]
Abstract
C4 plants achieve higher photosynthesis (An ) and intrinsic water use efficiency (iWUE) than C3 plants, but processes underpinning the variability in An and iWUE across the three C4 subtypes remain unclear, partly because we lack an integrated framework for quantifying the contribution of diffusional and biochemical limitations to C4 photosynthesis. We exploited the natural diversity among C4 grasses to develop an original mathematical approach for estimating eight key processes of C4 photosynthesis and their relative limitations to An . We also developed a new formulation to estimate mesophyll conductance (gm ) based on actual hydration rates of CO2 by carbonic anhydrases. We found a positive relationship between gm and iWUE and an inverse correlation with gsw among C4 grasses. We also revealed subtype-specific regulatory processes of iWUE that may be related to known anatomical traits characterising each C4 subtype. Leaf width was an important determinant of iWUE and showed significant correlations with key limitations of An , especially among NADP-ME species. In conclusion, incorporating leaf width in breeding trials may unlock new opportunities for C4 crops because the revealed negative relationship between leaf width and iWUE may translate into higher crop and canopy WUE.
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Affiliation(s)
- Francisco Javier Cano
- ARC Centre of Translational Photosynthesis and Hawkesbury Institute for the Environment, Western Sydney University, Sydney, NSW, 2753, Australia
| | - Robert E Sharwood
- ARC Centre of Translational Photosynthesis and Australian National University, Research School of Biology, Acton, ACT, 2601, Australia
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
| | - Oula Ghannoum
- ARC Centre of Translational Photosynthesis and Hawkesbury Institute for the Environment, Western Sydney University, Sydney, NSW, 2753, Australia
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16
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DeLucia EH, Chen S, Guan K, Peng B, Li Y, Gomez‐Casanovas N, Kantola IB, Bernacchi CJ, Huang Y, Long SP, Ort DR. Are we approaching a water ceiling to maize yields in the United States? Ecosphere 2019. [DOI: 10.1002/ecs2.2773] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Evan H. DeLucia
- Department of Plant Biology University of Illinois Urbana Illinois 61801 USA
- Institute for Sustainability, Energy, and Environment University of Illinois Urbana Illinois 61801 USA
- Carl R. Woese Institute for Genomic Biology University of Illinois Urbana Illinois 61801 USA
- Center for Advanced Bioenergy and Bioproducts Innovation University of Illinois Urbana Illinois 61801 USA
- Department of Natural Resources and Environmental Science University of Illinois Urbana Illinois 61801 USA
| | - Shiliu Chen
- Department of Natural Resources and Environmental Science University of Illinois Urbana Illinois 61801 USA
- State Key Laboratory of Plateau Ecology and Agriculture Qinghai University Xining Qinghai 810016 China
| | - Kaiyu Guan
- Institute for Sustainability, Energy, and Environment University of Illinois Urbana Illinois 61801 USA
- Center for Advanced Bioenergy and Bioproducts Innovation University of Illinois Urbana Illinois 61801 USA
- Department of Natural Resources and Environmental Science University of Illinois Urbana Illinois 61801 USA
- National Center for Supercomputing Applications University of Illinois Urbana Illinois 61801 USA
- State Key Laboratory of Plateau Ecology and Agriculture Qinghai University Xining Qinghai 810016 China
| | - Bin Peng
- Department of Natural Resources and Environmental Science University of Illinois Urbana Illinois 61801 USA
- National Center for Supercomputing Applications University of Illinois Urbana Illinois 61801 USA
| | - Yan Li
- Department of Natural Resources and Environmental Science University of Illinois Urbana Illinois 61801 USA
| | - Nuria Gomez‐Casanovas
- Department of Plant Biology University of Illinois Urbana Illinois 61801 USA
- Institute for Sustainability, Energy, and Environment University of Illinois Urbana Illinois 61801 USA
- Carl R. Woese Institute for Genomic Biology University of Illinois Urbana Illinois 61801 USA
| | - Ilsa B. Kantola
- Institute for Sustainability, Energy, and Environment University of Illinois Urbana Illinois 61801 USA
- Carl R. Woese Institute for Genomic Biology University of Illinois Urbana Illinois 61801 USA
| | - Carl J. Bernacchi
- Department of Plant Biology University of Illinois Urbana Illinois 61801 USA
- Carl R. Woese Institute for Genomic Biology University of Illinois Urbana Illinois 61801 USA
- Center for Advanced Bioenergy and Bioproducts Innovation University of Illinois Urbana Illinois 61801 USA
- USDA‐ARS Global Change and Photosynthesis Research Unit Urbana Illinois 61801 USA
| | - Yuefei Huang
- Department of Hydraulic Engineering State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China
- State Key Laboratory of Plateau Ecology and Agriculture Qinghai University Xining Qinghai 810016 China
| | - Stephen P. Long
- Department of Plant Biology University of Illinois Urbana Illinois 61801 USA
- Institute for Sustainability, Energy, and Environment University of Illinois Urbana Illinois 61801 USA
- Carl R. Woese Institute for Genomic Biology University of Illinois Urbana Illinois 61801 USA
- Center for Advanced Bioenergy and Bioproducts Innovation University of Illinois Urbana Illinois 61801 USA
- National Center for Supercomputing Applications University of Illinois Urbana Illinois 61801 USA
| | - Donald R. Ort
- Department of Plant Biology University of Illinois Urbana Illinois 61801 USA
- Carl R. Woese Institute for Genomic Biology University of Illinois Urbana Illinois 61801 USA
- Center for Advanced Bioenergy and Bioproducts Innovation University of Illinois Urbana Illinois 61801 USA
- Department of Crop Science University of Illinois Urbana Illinois 61801 USA
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17
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Giuliani R, Karki S, Covshoff S, Lin HC, Coe RA, Koteyeva NK, Quick WP, Von Caemmerer S, Furbank RT, Hibberd JM, Edwards GE, Cousins AB. Knockdown of glycine decarboxylase complex alters photorespiratory carbon isotope fractionation in Oryza sativa leaves. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:2773-2786. [PMID: 30840760 PMCID: PMC6506765 DOI: 10.1093/jxb/erz083] [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: 10/23/2018] [Accepted: 02/12/2019] [Indexed: 05/07/2023]
Abstract
The influence of reduced glycine decarboxylase complex (GDC) activity on leaf atmosphere CO2 and 13CO2 exchange was tested in transgenic Oryza sativa with the GDC H-subunit knocked down in leaf mesophyll cells. Leaf measurements on transgenic gdch knockdown and wild-type plants were carried out in the light under photorespiratory and low photorespiratory conditions (i.e. 18.4 kPa and 1.84 kPa atmospheric O2 partial pressure, respectively), and in the dark. Under approximately current ambient O2 partial pressure (18.4 kPa pO2), the gdch knockdown plants showed an expected photorespiratory-deficient phenotype, with lower leaf net CO2 assimilation rates (A) than the wild-type. Additionally, under these conditions, the gdch knockdown plants had greater leaf net discrimination against 13CO2 (Δo) than the wild-type. This difference in Δo was in part due to lower 13C photorespiratory fractionation (f) ascribed to alternative decarboxylation of photorespiratory intermediates. Furthermore, the leaf dark respiration rate (Rd) was enhanced and the 13CO2 composition of respired CO2 (δ13CRd) showed a tendency to be more depleted in the gdch knockdown plants. These changes in Rd and δ13CRd were due to the amount and carbon isotopic composition of substrates available for dark respiration. These results demonstrate that impairment of the photorespiratory pathway affects leaf 13CO2 exchange, particularly the 13C decarboxylation fractionation associated with photorespiration.
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Affiliation(s)
- Rita Giuliani
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, USA
| | - Shanta Karki
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
| | - Sarah Covshoff
- Department of Plant Sciences, University of Cambridge, Cambridge, 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, St. Petersburg, Russia
| | - W Paul Quick
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK
| | - Susanne Von Caemmerer
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, Australia
| | - Robert T Furbank
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, Australia
| | - Julian M Hibberd
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Gerald E Edwards
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, USA
| | - Asaph B Cousins
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, USA
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18
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Knauer J, Zaehle S, De Kauwe MG, Bahar NHA, Evans JR, Medlyn BE, Reichstein M, Werner C. Effects of mesophyll conductance on vegetation responses to elevated CO 2 concentrations in a land surface model. GLOBAL CHANGE BIOLOGY 2019; 25:1820-1838. [PMID: 30809890 PMCID: PMC6487956 DOI: 10.1111/gcb.14604] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 01/26/2019] [Indexed: 05/13/2023]
Abstract
Mesophyll conductance (gm ) is known to affect plant photosynthesis. However, gm is rarely explicitly considered in land surface models (LSMs), with the consequence that its role in ecosystem and large-scale carbon and water fluxes is poorly understood. In particular, the different magnitudes of gm across plant functional types (PFTs) are expected to cause spatially divergent vegetation responses to elevated CO2 concentrations. Here, an extensive literature compilation of gm across major vegetation types is used to parameterize an empirical model of gm in the LSM JSBACH and to adjust photosynthetic parameters based on simulated An - Ci curves. We demonstrate that an explicit representation of gm changes the response of photosynthesis to environmental factors, which cannot be entirely compensated by adjusting photosynthetic parameters. These altered responses lead to changes in the photosynthetic sensitivity to atmospheric CO2 concentrations which depend both on the magnitude of gm and the climatic conditions, particularly temperature. We then conducted simulations under ambient and elevated (ambient + 200 μmol/mol) CO2 concentrations for contrasting ecosystems and for historical and anticipated future climate conditions (representative concentration pathways; RCPs) globally. The gm -explicit simulations using the RCP8.5 scenario resulted in significantly higher increases in gross primary productivity (GPP) in high latitudes (+10% to + 25%), intermediate increases in temperate regions (+5% to + 15%), and slightly lower to moderately higher responses in tropical regions (-2% to +5%), which summed up to moderate GPP increases globally. Similar patterns were found for transpiration, but with a lower magnitude. Our results suggest that the effect of an explicit representation of gm is most important for simulated carbon and water fluxes in the boreal zone, where a cold climate coincides with evergreen vegetation.
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Affiliation(s)
- Jürgen Knauer
- Department of Biogeochemical IntegrationMax Planck Institute for BiogeochemistryJenaGermany
- International Max Planck Research School for Global Biogeochemical Cycles (IMPRS gBGC)JenaGermany
| | - Sönke Zaehle
- Department of Biogeochemical IntegrationMax Planck Institute for BiogeochemistryJenaGermany
- Michael‐Stifel Center Jena for Data‐Driven and Simulation ScienceJenaGermany
| | - Martin G. De Kauwe
- ARC Centre of Excellence for Climate Extremes and the Climate Change Research CentreUniversity of New South WalesSydneyNSWAustralia
| | - Nur H. A. Bahar
- ARC Centre of Excellence in Plant Energy Biology, Division of Plant SciencesResearch School of Biology, Australian National UniversityCanberraACTAustralia
| | - John R. Evans
- ARC Centre of Excellence for Translational Photosynthesis, Division of Plant SciencesResearch School of Biology, Australian National UniversityCanberraACTAustralia
| | - Belinda E. Medlyn
- Hawkesbury Institute for the EnvironmentWestern Sydney UniversityRichmondNSWAustralia
| | - Markus Reichstein
- Department of Biogeochemical IntegrationMax Planck Institute for BiogeochemistryJenaGermany
- Michael‐Stifel Center Jena for Data‐Driven and Simulation ScienceJenaGermany
| | - Christiane Werner
- Department of Ecosystem PhysiologyUniversity of FreiburgFreiburgGermany
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19
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Leakey ADB, Ferguson JN, Pignon CP, Wu A, Jin Z, Hammer GL, Lobell DB. Water Use Efficiency as a Constraint and Target for Improving the Resilience and Productivity of C 3 and C 4 Crops. ANNUAL REVIEW OF PLANT BIOLOGY 2019; 70:781-808. [PMID: 31035829 DOI: 10.1146/annurev-arplant-042817-040305] [Citation(s) in RCA: 108] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The ratio of plant carbon gain to water use, known as water use efficiency (WUE), has long been recognized as a key constraint on crop production and an important target for crop improvement. WUE is a physiologically and genetically complex trait that can be defined at a range of scales. Many component traits directly influence WUE, including photosynthesis, stomatal and mesophyll conductances, and canopy structure. Interactions of carbon and water relations with diverse aspects of the environment and crop development also modulate WUE. As a consequence, enhancing WUE by breeding or biotechnology has proven challenging but not impossible. This review aims to synthesize new knowledge of WUE arising from advances in phenotyping, modeling, physiology, genetics, and molecular biology in the context of classical theoretical principles. In addition, we discuss how rising atmospheric CO2 concentration has created and will continue to create opportunities for enhancing WUE by modifying the trade-off between photosynthesis and transpiration.
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Affiliation(s)
- Andrew D B Leakey
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA;
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - John N Ferguson
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Charles P Pignon
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA;
| | - Alex Wu
- Centre for Crop Science and Centre of Excellence for Translational Photosynthesis, University of Queensland, St. Lucia, Queensland 4069, Australia
| | - Zhenong Jin
- Department of Earth System Science and Center for Food Security and Environment, Stanford University, Stanford, California 94305, USA
| | - Graeme L Hammer
- Centre for Crop Science and Centre of Excellence for Translational Photosynthesis, University of Queensland, St. Lucia, Queensland 4069, Australia
| | - David B Lobell
- Department of Earth System Science and Center for Food Security and Environment, Stanford University, Stanford, California 94305, USA
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20
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Sonawane BV, Cousins AB. Uncertainties and limitations of using carbon-13 and oxygen-18 leaf isotope exchange to estimate the temperature response of mesophyll CO 2 conductance in C 3 plants. THE NEW PHYTOLOGIST 2019; 222:122-131. [PMID: 30394538 DOI: 10.1111/nph.15585] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 10/28/2018] [Indexed: 06/08/2023]
Abstract
The internal CO2 gradient imposed by mesophyll conductance (gm ) reduces substrate availability for C3 photosynthesis. With several assumptions, estimates of gm can be made from coupled leaf gas exchange with isoflux analysis of carbon ∆13 C-gm and oxygen in CO2 , coupled with transpired water (H2 O) ∆18 O-gm to partition gm into its biochemical and anatomical components. However, these assumptions require validation under changing leaf temperatures. To test these assumptions, we measured and modeled the temperature response (15-40°C) of ∆13 C-gm and ∆18 O-gm along with leaf biochemistry in the C3 grass Panicum bisulcatum, which has naturally low carbonic anhydrase activity. Our study suggests that assumptions regarding the extent of isotopic equilibrium (θ) between CO2 and H2 O at the site of exchange, and that the isotopic composition of the H2 O at the sites of evaporation ( δw-e18 ) and at the site of exchange ( δw-ce18 ) are similar, may lead to errors in estimating the ∆18 O-gm temperature response. The input parameters for ∆13 C-gm appear to be less sensitive to temperature. However, this needs to be tested in species with diverse carbonic anhydrase activity. Additional information on the temperature dependency of cytosolic and chloroplastic pH may clarify uncertainties used for ∆18 O-gm under changing leaf temperatures.
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Affiliation(s)
- Balasaheb V Sonawane
- 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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21
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Kolbe AR, Studer AJ, Cornejo OE, Cousins AB. Insights from transcriptome profiling on the non-photosynthetic and stomatal signaling response of maize carbonic anhydrase mutants to low CO 2. BMC Genomics 2019; 20:138. [PMID: 30767781 PMCID: PMC6377783 DOI: 10.1186/s12864-019-5522-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 02/08/2019] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Carbonic anhydrase (CA) catalyzes the hydration of CO2 in the first biochemical step of C4 photosynthesis, and has been considered a potentially rate-limiting step when CO2 availability within a leaf is low. Previous work in Zea mays (maize) with a double knockout of the two highest-expressed β-CA genes, CA1 and CA2, reduced total leaf CA activity to less than 3% of wild-type. Surprisingly, this did not limit photosynthesis in maize at ambient or higher CO2concentrations. However, the ca1ca2 mutants exhibited reduced rates of photosynthesis at sub-ambient CO2, and accumulated less biomass when grown under sub-ambient CO2 (9.2 Pa). To further clarify the importance of CA for C4 photosynthesis, we assessed gene expression changes in wild-type, ca1 and ca1ca2 mutants in response to changes in pCO2 from 920 to 9.2 Pa. RESULTS Leaf samples from each genotype were collected for RNA-seq analysis at high CO2 and at two time points after the low CO2 transition, in order to identify early and longer-term responses to CO2 deprivation. Despite the existence of multiple isoforms of CA, no other CA genes were upregulated in CA mutants. Although photosynthetic genes were downregulated in response to low CO2, differential expression was not observed between genotypes. However, multiple indicators of carbon starvation were present in the mutants, including amino acid synthesis, carbohydrate metabolism, and sugar signaling. In particular, multiple genes previously implicated in low carbon stress such as asparagine synthetase, amino acid transporters, trehalose-6-phosphate synthase, as well as many transcription factors, were strongly upregulated. Furthermore, genes in the CO2 stomatal signaling pathway were differentially expressed in the CA mutants under low CO2. CONCLUSIONS Using a transcriptomic approach, we showed that carbonic anhydrase mutants do not compensate for the lack of CA activity by upregulating other CA or photosynthetic genes, but rather experienced extreme carbon stress when grown under low CO2. Our results also support a role for CA in the CO2 stomatal signaling pathway. This study provides insight into the importance of CA for C4 photosynthesis and its role in stomatal signaling.
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Affiliation(s)
- Allison R. Kolbe
- School of Biological Sciences, Washington State University, Pullman, WA USA
| | - Anthony J. Studer
- Department of Crop Sciences, University of Illinois Urbana-Champaign, Urbana, IL USA
| | - Omar E. Cornejo
- 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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Ubierna N, Gandin A, Cousins AB. The response of mesophyll conductance to short-term variation in CO2 in the C4 plants Setaria viridis and Zea mays. JOURNAL OF EXPERIMENTAL BOTANY 2018; 69:1159-1170. [PMID: 29474683 PMCID: PMC6018935 DOI: 10.1093/jxb/erx464] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2017] [Accepted: 01/10/2018] [Indexed: 05/13/2023]
Abstract
Mesophyll conductance (gm) limits rates of C3 photosynthesis but little is known about its role in C4 photosynthesis. If gm were to limit C4 photosynthesis, it would likely be at low CO2 concentrations (pCO2). However, data on C4-gm across ranges of pCO2 are scarce. We describe the response of C4-gm to short-term variation in pCO2, at three temperatures in Setaria viridis, and at 25 °C in Zea mays. Additionally, we quantified the effect of finite gm calculations of leakiness (ϕ) and the potential limitations to photosynthesis imposed by stomata, mesophyll, and carbonic anhydrase (CA) across pCO2. In both species, gm increased with decreasing pCO2. Including a finite gm resulted in either no change or increased ϕ compared with values calculated with infinite gm depending on whether the observed 13C discrimination was high (Setaria) or low (Zea). Post-transitional regulation of the maximal PEP carboxylation rate and PEP regeneration limitation could influence estimates of gm and ϕ. At pCO2 below ambient, the photosynthetic rate was limited by CO2 availability. In this case, the limitation imposed by the mesophyll was similar or slightly lower than stomata limitation. At very low pCO2, CA further constrained photosynthesis. High gm could increase CO2 assimilation at low pCO2 and improve photosynthetic efficiency under situations when CO2 is limited, such as drought.
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Affiliation(s)
- Nerea Ubierna
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, Washington, USA
| | - Anthony Gandin
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, Washington, USA
| | - Asaph B Cousins
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, Washington, USA
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