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Mabry ME, Abrahams RS, Al-Shehbaz IA, Baker WJ, Barak S, Barker MS, Barrett RL, Beric A, Bhattacharya S, Carey SB, Conant GC, Conran JG, Dassanayake M, Edger PP, Hall JC, Hao Y, Hendriks KP, Hibberd JM, King GJ, Kliebenstein DJ, Koch MA, Leitch IJ, Lens F, Lysak MA, McAlvay AC, McKibben MTW, Mercati F, Moore RC, Mummenhoff K, Murphy DJ, Nikolov LA, Pisias M, Roalson EH, Schranz ME, Thomas SK, Yu Q, Yocca A, Pires JC, Harkess AE. Complementing model species with model clades. THE PLANT CELL 2024; 36:1205-1226. [PMID: 37824826 PMCID: PMC11062466 DOI: 10.1093/plcell/koad260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 09/07/2023] [Accepted: 09/22/2023] [Indexed: 10/14/2023]
Abstract
Model species continue to underpin groundbreaking plant science research. At the same time, the phylogenetic resolution of the land plant tree of life continues to improve. The intersection of these 2 research paths creates a unique opportunity to further extend the usefulness of model species across larger taxonomic groups. Here we promote the utility of the Arabidopsis thaliana model species, especially the ability to connect its genetic and functional resources, to species across the entire Brassicales order. We focus on the utility of using genomics and phylogenomics to bridge the evolution and diversification of several traits across the Brassicales to the resources in Arabidopsis, thereby extending scope from a model species by establishing a "model clade." These Brassicales-wide traits are discussed in the context of both the model species Arabidopsis and the family Brassicaceae. We promote the utility of such a "model clade" and make suggestions for building global networks to support future studies in the model order Brassicales.
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Affiliation(s)
- Makenzie E Mabry
- Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA
| | - R Shawn Abrahams
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520, USA
- Department of Biochemistry, Purdue University, West Lafayette, IN 47906, USA
| | | | | | - Simon Barak
- Ben-Gurion University of the Negev, French Associates Institute for Agriculture and Biotechnology of Drylands, Jacob Blaustein Institutes for Desert Research, Midreshet Ben-Gurion, 8499000, Israel
| | - Michael S Barker
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA
| | - Russell L Barrett
- National Herbarium of New South Wales, Australian Botanic Garden, Locked Bag 6002, Mount Annan, NSW 2567, Australia
| | - Aleksandra Beric
- Department of Psychiatry, Washington University in Saint Louis School of Medicine, St. Louis, MO 63110, USA
- NeuroGenomics and Informatics Center, Washington University in Saint Louis School of Medicine, St. Louis, MO 63108, USA
| | - Samik Bhattacharya
- Department of Biology, Botany, University of Osnabrück, D-49076 Osnabrück, Germany
| | - Sarah B Carey
- HudsonAlpha Institute for Biotechnology, Huntsville, AL 35806, USA
| | - Gavin C Conant
- Department of Biological Sciences, Bioinformatics Research Center, Program in Genetics, North Carolina State University, Raleigh, NC 27695, USA
| | - John G Conran
- ACEBB and SGC, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
| | - Maheshi Dassanayake
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Patrick P Edger
- Department of Horticulture, Michigan State University, East Lansing, MI 48864, USA
| | - Jocelyn C Hall
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
| | - Yue Hao
- Cancer and Cell Biology Division, Translational Genomics Research Institute, Phoenix, AZ 85004, USA
| | - Kasper P Hendriks
- Department of Biology, Botany, University of Osnabrück, D-49076 Osnabrück, Germany
- Functional Traits, Naturalis Biodiversity Center, PO Box 9517, Leiden 2300 RA, the Netherlands
| | - Julian M Hibberd
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 1TN, UK
| | - Graham J King
- Southern Cross Plant Science, Southern Cross University, Lismore, NSW 2480, Australia
| | | | - Marcus A Koch
- Centre for Organismal Studies (COS), Heidelberg University, 69120 Heidelberg, Germany
| | - Ilia J Leitch
- Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AE, UK
| | - Frederic Lens
- Functional Traits, Naturalis Biodiversity Center, PO Box 9517, Leiden 2300 RA, the Netherlands
- Institute of Biology Leiden, Plant Sciences, Leiden University, 2333 BE Leiden, the Netherlands
| | - Martin A Lysak
- CEITEC, and NCBR, Faculty of Science, Masaryk University, 625 00 Brno, Czech Republic
| | - Alex C McAlvay
- Institute of Economic Botany, New York Botanical Garden, The Bronx, NY 10458, USA
| | - Michael T W McKibben
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA
| | - Francesco Mercati
- National Research Council (CNR), Institute of Biosciences and Bioresource (IBBR), Palermo 90129, Italy
| | | | - Klaus Mummenhoff
- Department of Biology, Botany, University of Osnabrück, D-49076 Osnabrück, Germany
| | - Daniel J Murphy
- Royal Botanic Gardens Victoria, Melbourne, VIC 3004, Australia
| | | | - Michael Pisias
- Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Eric H Roalson
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - M Eric Schranz
- Biosystematics Group, Wageningen University, 6708 PB Wageningen, the Netherlands
| | - Shawn K Thomas
- Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA
- Bioinformatics and Analytics Core, University of Missouri, Columbia, MO 65211, USA
| | - Qingyi Yu
- Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center, Agricultural Research Service, United States Department of Agriculture, Hilo, HI 96720, USA
| | - Alan Yocca
- HudsonAlpha Institute for Biotechnology, Huntsville, AL 35806, USA
| | - J Chris Pires
- Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523-1170, USA
| | - Alex E Harkess
- HudsonAlpha Institute for Biotechnology, Huntsville, AL 35806, USA
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2
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Gilman IS, Smith JAC, Holtum JAM, Sage RF, Silvera K, Winter K, Edwards EJ. The CAM lineages of planet Earth. ANNALS OF BOTANY 2023; 132:627-654. [PMID: 37698538 PMCID: PMC10799995 DOI: 10.1093/aob/mcad135] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 01/09/2023] [Accepted: 09/11/2023] [Indexed: 09/13/2023]
Abstract
BACKGROUND AND SCOPE The growth of experimental studies of crassulacean acid metabolism (CAM) in diverse plant clades, coupled with recent advances in molecular systematics, presents an opportunity to re-assess the phylogenetic distribution and diversity of species capable of CAM. It has been more than two decades since the last comprehensive lists of CAM taxa were published, and an updated survey of the occurrence and distribution of CAM taxa is needed to facilitate and guide future CAM research. We aimed to survey the phylogenetic distribution of these taxa, their diverse morphology, physiology and ecology, and the likely number of evolutionary origins of CAM based on currently known lineages. RESULTS AND CONCLUSIONS We found direct evidence (in the form of experimental or field observations of gas exchange, day-night fluctuations in organic acids, carbon isotope ratios and enzymatic activity) for CAM in 370 genera of vascular plants, representing 38 families. Further assumptions about the frequency of CAM species in CAM clades and the distribution of CAM in the Cactaceae and Crassulaceae bring the currently estimated number of CAM-capable species to nearly 7 % of all vascular plants. The phylogenetic distribution of these taxa suggests a minimum of 66 independent origins of CAM in vascular plants, possibly with dozens more. To achieve further insight into CAM origins, there is a need for more extensive and systematic surveys of previously unstudied lineages, particularly in living material to identify low-level CAM activity, and for denser sampling to increase phylogenetic resolution in CAM-evolving clades. This should allow further progress in understanding the functional significance of this pathway by integration with studies on the evolution and genomics of CAM in its many forms.
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Affiliation(s)
- Ian S Gilman
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
| | | | - Joseph A M Holtum
- College of Science and Engineering, James Cook University, Townsville, Queensland, Australia
| | - Rowan F Sage
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
| | - Katia Silvera
- Smithsonian Tropical Research Institute, Balboa, Ancón, Panama
- Department of Botany & Plant Sciences, University of California, Riverside, CA, USA
| | - Klaus Winter
- Smithsonian Tropical Research Institute, Balboa, Ancón, Panama
| | - Erika J Edwards
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
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3
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Holtum JAM. The diverse diaspora of CAM: a pole-to-pole sketch. ANNALS OF BOTANY 2023; 132:597-625. [PMID: 37303205 PMCID: PMC10800000 DOI: 10.1093/aob/mcad067] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 12/13/2022] [Accepted: 06/09/2023] [Indexed: 06/13/2023]
Abstract
BACKGROUND Crassulacean acid metabolism (CAM) photosynthesis is a successful adaptation that has evolved often in angiosperms, gymnosperms, ferns and lycophytes. Present in ~5 % of vascular plants, the CAM diaspora includes all continents apart from Antarctica. Species with CAM inhabit most landscapes colonized by vascular plants, from the Arctic Circle to Tierra del Fuego, from below sea level to 4800 m a.s.l., from rainforests to deserts. They have colonized terrestrial, epiphytic, lithophytic, palustrine and aquatic systems, developing perennial, annual or geophyte strategies that can be structurally arborescent, shrub, forb, cladode, epiphyte, vine or leafless with photosynthetic roots. CAM can enhance survival by conserving water, trapping carbon, reducing carbon loss and/or via photoprotection. SCOPE This review assesses the phylogenetic diversity and historical biogeography of selected lineages with CAM, i.e. ferns, gymnosperms and eumagnoliids, Orchidaceae, Bromeliaceae, Crassulaceae, Euphorbiaceae, Aizoaceae, Portulacineae (Montiaceae, Basellaceae, Halophytaceae, Didiereaceae, Talinaceae, Portulacaceae, Anacampserotaceae and Cactaceae) and aquatics. CONCLUSIONS Most extant CAM lineages diversified after the Oligocene/Miocene, as the planet dried and CO2 concentrations dropped. Radiations exploited changing ecological landscapes, including Andean emergence, Panamanian Isthmus closure, Sundaland emergence and submergence, changing climates and desertification. Evidence remains sparse for or against theories that CAM biochemistry tends to evolve before pronounced changes in anatomy and that CAM tends to be a culminating xerophytic trait. In perennial taxa, any form of CAM can occur depending upon the lineage and the habitat, although facultative CAM appears uncommon in epiphytes. CAM annuals lack strong CAM. In CAM annuals, C3 + CAM predominates, and inducible or facultative CAM is common.
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Affiliation(s)
- Joseph A M Holtum
- College of Science and Engineering, James Cook University, Townsville, QLD4811, Australia
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Berasategui JA, Žerdoner Čalasan A, Zizka A, Kadereit G. Global distribution, climatic preferences and photosynthesis-related traits of C 4 eudicots and how they differ from those of C 4 grasses. Ecol Evol 2023; 13:e10720. [PMID: 37964791 PMCID: PMC10641307 DOI: 10.1002/ece3.10720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 10/25/2023] [Accepted: 10/30/2023] [Indexed: 11/16/2023] Open
Abstract
C₄ is one of three known photosynthetic processes of carbon fixation in flowering plants. It evolved independently more than 61 times in multiple angiosperm lineages and consists of a series of anatomical and biochemical modifications to the ancestral C3 pathway increasing plant productivity under warm and light-rich conditions. The C4 lineages of eudicots belong to seven orders and 15 families, are phylogenetically less constrained than those of monocots and entail an enormous structural and ecological diversity. Eudicot C4 lineages likely evolved the C4 syndrome along different evolutionary paths. Therefore, a better understanding of this diversity is key to understanding the evolution of this complex trait as a whole. By compiling 1207 recognised C4 eudicots species described in the literature and presenting trait data among these species, we identify global centres of species richness and of high phylogenetic diversity. Furthermore, we discuss climatic preferences in the context of plant functional traits. We identify two hotspots of C4 eudicot diversity: arid regions of Mexico/Southern United States and Australia, which show a similarly high number of different C4 eudicot genera but differ in the number of C4 lineages that evolved in situ. Further eudicot C4 hotspots with many different families and genera are in South Africa, West Africa, Patagonia, Central Asia and the Mediterranean. In general, C4 eudicots are diverse in deserts and xeric shrublands, tropical and subtropical grasslands, savannas and shrublands. We found C4 eudicots to occur in areas with less annual precipitation than C4 grasses which can be explained by frequently associated adaptations to drought stress such as among others succulence and salt tolerance. The data indicate that C4 eudicot lineages utilising the NAD-ME decarboxylating enzyme grow in drier areas than those using the NADP-ME decarboxylating enzyme indicating biochemical restrictions of the later system in higher temperatures. We conclude that in most eudicot lineages, C4 evolved in ancestrally already drought-adapted clades and enabled these to further spread in these habitats and colonise even drier areas.
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Affiliation(s)
- Jessica A. Berasategui
- Prinzessin Therese von Bayern Lehrstuhl für Systematik, Biodiversität & Evolution der PflanzenLudwig‐Maximilians Universität MünchenMünchenGermany
- Institute for Molecular PhysiologyJohannes Gutenberg‐University MainzMainzGermany
| | - Anže Žerdoner Čalasan
- Prinzessin Therese von Bayern Lehrstuhl für Systematik, Biodiversität & Evolution der PflanzenLudwig‐Maximilians Universität MünchenMünchenGermany
| | - Alexander Zizka
- Department of BiologyPhilipps‐University MarburgMarburgGermany
| | - Gudrun Kadereit
- Prinzessin Therese von Bayern Lehrstuhl für Systematik, Biodiversität & Evolution der PflanzenLudwig‐Maximilians Universität MünchenMünchenGermany
- Botanischer Garten München‐Nymphenburg und Botanische Staatssammlung MünchenStaatliche Naturwissenschaftliche Sammlungen BayernsMünchenGermany
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Ferrari RC, Kawabata AB, Ferreira SS, Hartwell J, Freschi L. A matter of time: regulatory events behind the synchronization of C4 and crassulacean acid metabolism in Portulaca oleracea. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:4867-4885. [PMID: 35439821 DOI: 10.1093/jxb/erac163] [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: 11/30/2021] [Accepted: 04/14/2022] [Indexed: 06/14/2023]
Abstract
Portulaca species can switch between C4 and crassulacean acid metabolism (CAM) depending on environmental conditions. However, the regulatory mechanisms behind this rare photosynthetic adaptation remain elusive. Using Portulaca oleracea as a model system, here we investigated the involvement of the circadian clock, plant hormones, and transcription factors in coordinating C4 and CAM gene expression. Free-running experiments in constant conditions suggested that C4 and CAM gene expression are intrinsically connected to the circadian clock. Detailed time-course, drought, and rewatering experiments revealed distinct time frames for CAM induction and reversion (days versus hours, respectively), which were accompanied by changes in abscisic acid (ABA) and cytokinin metabolism and signaling. Exogenous ABA and cytokinins were shown to promote and repress CAM expression in P. oleracea, respectively. Moreover, the drought-induced decline in C4 transcript levels was completely recovered upon cytokinin treatment. The ABA-regulated transcription factor genes HB7, NFYA7, NFYC9, TT8, and ARR12 were identified as likely candidate regulators of CAM induction following this approach, whereas NFYC4 and ARR9 were connected to C4 expression patterns. Therefore, we provide insights into the signaling events controlling C4-CAM transitions in response to water availability and over the day/night cycle, highlighting candidate genes for future functional studies in the context of facultative C4-CAM photosynthesis.
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Affiliation(s)
- Renata Callegari Ferrari
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, Brasil
| | - Aline Bastos Kawabata
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, Brasil
| | - Sávio Siqueira Ferreira
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, Brasil
| | - James Hartwell
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Luciano Freschi
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, Brasil
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6
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Callegari Ferrari R, Pires Bittencourt P, Yumi Nagumo P, Silva Oliveira W, Aurineide Rodrigues M, Hartwell J, Freschi L. Developing Portulaca oleracea as a model system for functional genomics analysis of C 4/CAM photosynthesis. FUNCTIONAL PLANT BIOLOGY : FPB 2021; 48:666-682. [PMID: 33256895 DOI: 10.1071/fp20202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Accepted: 10/20/2020] [Indexed: 06/12/2023]
Abstract
Previously regarded as an intriguing photosynthetic curiosity, the occurrence of C4 and Crassulacean acid metabolism (CAM) photosynthesis within a single organism has recently emerged as a source of information for future biotechnological use. Among C4/CAM facultative species, Portulaca oleracea L. has been used as a model for biochemical and gene expression analysis of C4/CAM under field and laboratory conditions. In the present work, we focussed on developing molecular tools to facilitate functional genomics studies in this species, from the optimisation of RNA isolation protocols to a method for stable genetic transformation. Eleven variations of RNA extraction procedures were tested and compared for RNA quantity and quality. Also, 7 sample sets comprising total RNA from hormonal and abiotic stress treatments, distinct plant organs, leaf developmental stages, and subspecies were used to select, among 12 reference genes, the most stable reference genes for RT-qPCR analysis of each experimental condition. Furthermore, different explant sources, Agrobacterium tumefaciens strains, and regeneration and antibiotic selection media were tested in various combinations to optimise a protocol for stable genetic transformation of P. oleracea. Altogether, we provide essential tools for functional gene analysis in the context of C4/CAM photosynthesis, including an efficient RNA isolation method, preferred reference genes for RT-qPCR normalisation for a range of experimental conditions, and a protocol to produce P. oleracea stable transformants using A. tumefaciens.
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Affiliation(s)
- Renata Callegari Ferrari
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo 05508-090, Brasil
| | - Priscila Pires Bittencourt
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo 05508-090, Brasil
| | - Paula Yumi Nagumo
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo 05508-090, Brasil
| | - Willian Silva Oliveira
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo 05508-090, Brasil
| | - Maria Aurineide Rodrigues
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo 05508-090, Brasil
| | - James Hartwell
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, UK
| | - Luciano Freschi
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo 05508-090, Brasil; and Corresponding author.
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7
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Winter K, Garcia M, Virgo A, Ceballos J, Holtum JAM. Does the C 4 plant Trianthema portulacastrum (Aizoaceae) exhibit weakly expressed crassulacean acid metabolism (CAM)? FUNCTIONAL PLANT BIOLOGY : FPB 2021; 48:655-665. [PMID: 33213694 DOI: 10.1071/fp20247] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 10/06/2020] [Indexed: 06/11/2023]
Abstract
We examined whether crassulacean acid metabolism (CAM) is present in Trianthema portulacastrum L. (Aizoaceae), a pantropical, salt-tolerant C4 annual herb with atriplicoid-type Kranz anatomy in leaves but not in stems. The leaves of T. portulacastrum are slightly succulent and the stems are fleshy, similar to some species of Portulaca, the only genus known in which C4 and CAM co-occur. Low- level nocturnal acidification typical of weakly expressed, predominantly constitutive CAM was measured in plants grown for their entire life-cycle in an outdoor raised garden box. Acidification was greater in stems than in leaves. Plants showed net CO2 uptake only during the light irrespective of soil water availability. However, nocturnal traces of CO2 exchange exhibited curved kinetics of reduced CO2 loss during the middle of the night consistent with low-level CAM. Trianthema becomes the second genus of vascular land plants in which C4 and features of CAM have been demonstrated to co-occur in the same plant and the first C4 plant with CAM-type acidification described for the Aizoaceae. Traditionally the stems of herbs are not sampled in screening studies. Small herbs with mildly succulent leaves and fleshy stems might be a numerically significant component of CAM biodiversity.
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Affiliation(s)
- Klaus Winter
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama; and Corresponding author.
| | - Milton Garcia
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama
| | - Aurelio Virgo
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama
| | - Jorge Ceballos
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama
| | - Joseph A M Holtum
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama; and College of Science and Engineering, James Cook University, Townsville, Qld 4811, Australia
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8
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Winter K, Virgo A, Garcia M, Aranda J, Holtum JAM. Constitutive and facultative crassulacean acid metabolism (CAM) in Cuban oregano, Coleus amboinicus (Lamiaceae). FUNCTIONAL PLANT BIOLOGY : FPB 2021; 48:647-654. [PMID: 32919492 DOI: 10.1071/fp20127] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 07/23/2020] [Indexed: 06/11/2023]
Abstract
Plants exhibiting the water-conserving crassulacean acid metabolism (CAM) photosynthetic pathway provide some of the most intriguing examples of photosynthetic diversity and plasticity. Here, a largely unnoticed facet of CAM-plant photosynthesis is highlighted: the co-occurrence of ontogenetically controlled constitutive and environmentally controlled facultative CAM in a species. Both forms of CAM are displayed in leaves of Coleus amboinicus Lour. (Lamiaceae), a semi-succulent perennial plant with oregano-like flavour that is native to southern and eastern Africa and naturalised elsewhere in the tropics. Under well-watered conditions, leaves assimilate CO2 predominantly by the C3 pathway. They also display low levels of CO2 uptake at night accompanied by small nocturnal increases in leaf tissue acidity. This indicates the presence of weakly expressed constitutive CAM. CAM expression is strongly enhanced in response to drought stress. The drought-enhanced component of CAM is reversible upon rewatering and thus considered to be facultative. In contrast to C. amboinicus, the thin-leaved closely related Coleus scutellarioides (L.) Benth. exhibits net CO2 fixation solely in the light via the C3 pathway, both under well-watered and drought conditions. However, low levels of nocturnal acidification detected in leaves and stems indicate that the CAM cycle is present. The highly speciose mint family, which contains few known CAM-exhibiting species and is composed predominantly of C3 species, appears to be an excellent group of plants for studying the evolutionary origins of CAM and for determining the position of facultative CAM along the C3-full CAM trajectory.
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Affiliation(s)
- Klaus Winter
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama; and Corresponding author.
| | - Aurelio Virgo
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama
| | - Milton Garcia
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama
| | - Jorge Aranda
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama
| | - Joseph A M Holtum
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama; and College of Science and Engineering, James Cook University, Townsville, Qld 4811, Australia
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9
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Schweiger AH, Nürk NM, Beckett H, Liede-Schumann S, Midgley GF, Higgins SI. The eco-evolutionary significance of rainfall constancy for facultative CAM photosynthesis. THE NEW PHYTOLOGIST 2021; 230:1653-1664. [PMID: 33533483 DOI: 10.1111/nph.17250] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 01/28/2021] [Indexed: 06/12/2023]
Abstract
A flexible use of the crassulacean acid metabolism (CAM) has been hypothesised to represent an intermediate stage along a C3 to full CAM evolutionary continuum, when relative contributions of C3 vs CAM metabolism are co-determined by evolutionary history and prevailing environmental constraints. However, evidence for such eco-evolutionary interdependencies is lacking. We studied these interdependencies for the leaf-succulent genus Drosanthemum (Aizoaceae, Southern African Succulent Karoo) by testing for relationships between leaf δ13 C diagnostic for CAM dependence (i.e. contribution of C3 and CAM to net carbon gain), and climatic variables related to temperature and precipitation and their temporal variation. We further quantified the effects of shared phylogenetic ancestry on CAM dependence and its relation to climate. CAM dependence is predicted by rainfall and its temporal variation, with high predictive power of rainfall constancy (temporal entropy). The predictive power of rainfall seasonality and temperature-related variables was negligible. Evolutionary history of the tested clades significantly affected the relationship between rainfall constancy and CAM dependence. We argue that higher CAM dependence might provide an adaptive advantage in increasingly unpredictable rainfall environments when the anatomic exaptation (succulence) is already present. These observations might shed light on the evolution of full CAM.
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Affiliation(s)
- Andreas H Schweiger
- Institute of Landscape and Plant Ecology, Department of Plant Ecology, University of Hohenheim, Ottilie-Zeller-Weg 2, Stuttgart, 70599, Germany
| | - Nicolai M Nürk
- Plant Systematics, University of Bayreuth, Universitätsstr. 30, Bayreuth, 95447, Germany
- Bayreuth Center of Ecology and Environmental Research, BayCEER, University of Bayreuth, Universitätsstr. 30, Bayreuth, 95447, Germany
| | - Heath Beckett
- Department of Botany and Zoology, Stellenbosch University, SUN, Stellenbosch, Western Cape, South Africa
| | - Sigrid Liede-Schumann
- Plant Systematics, University of Bayreuth, Universitätsstr. 30, Bayreuth, 95447, Germany
- Bayreuth Center of Ecology and Environmental Research, BayCEER, University of Bayreuth, Universitätsstr. 30, Bayreuth, 95447, Germany
| | - Guy F Midgley
- Department of Botany and Zoology, Stellenbosch University, SUN, Stellenbosch, Western Cape, South Africa
| | - Steven I Higgins
- Bayreuth Center of Ecology and Environmental Research, BayCEER, University of Bayreuth, Universitätsstr. 30, Bayreuth, 95447, Germany
- Plant Ecology, University of Bayreuth, Universitätsstr. 30, Bayreuth, 95447, Germany
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10
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Habibi G. Comparison of CAM expression, photochemistry and antioxidant responses in Sedum album and Portulaca oleracea under combined stress. PHYSIOLOGIA PLANTARUM 2020; 170:550-568. [PMID: 32785996 DOI: 10.1111/ppl.13187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 08/06/2020] [Indexed: 05/14/2023]
Abstract
Previous studies of crassulacean acid metabolism (CAM) pathway during stress have been directed at individual drought and salinity stress, here, we studied the effects of a combination of drought and salt on CAM expression, chlorophyll fluorescence and antioxidant parameters in the C3 -CAM facultative Sedum album and C4 -CAM facultative Portulaca oleracea plants. While salinity alone was not able to induce functional CAM expression in P. oleracea leaves, we showed that salinity induced low level of nocturnal acid accumulation in S. album species. After 20 d of exposure to the combination of simultaneous salt and drought stress, P. oleracea plants exhibited more resistance to photoinhibition as compared to S. album plants. The decrease of maximum quantum yield (Fv /Fm ) in S. album leaves under combined stress was in parallel with the largest suppression of CAM expression of >50%, probably displaying the withdrawal of functional CAM back to C3 pathway. However, under drought treatment alone, S. album plants exhibited higher photosynthetic flexibility, which was associated with the up-regulation of antioxidant enzymes activities and maintenance of glutathione (GSH) pool, and consequently higher photochemical functioning. The levels of nitric oxide (NO) correlated well with CAM expression, which was observed only in S. album, suggesting that NO acts in a different way in C3 and C4 species during CAM induction. Additionally, in both species, over the course of CAM induction, the changes in CAM expression parameters exhibited a similar pattern to that of antioxidant capacity and photochemical functioning parameters.
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Affiliation(s)
- Ghader Habibi
- Department of Biology, Payame Noor University (PNU), Tehran, Iran
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11
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Ferrari RC, Cruz BC, Gastaldi VD, Storl T, Ferrari EC, Boxall SF, Hartwell J, Freschi L. Exploring C 4-CAM plasticity within the Portulaca oleracea complex. Sci Rep 2020; 10:14237. [PMID: 32859905 PMCID: PMC7455729 DOI: 10.1038/s41598-020-71012-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 07/29/2020] [Indexed: 11/21/2022] Open
Abstract
Portulaca oleracea is a C4 herb capable of performing CAM under drought stress. It is distributed worldwide and is either considered a polymorphic species or a complex of subspecies, due to its numerous morphological variations. We evaluated CAM plasticity within P. oleracea genotypes since the complexity surrounding this species may be reflected in intraspecific variations in photosynthetic behavior. Eleven subspecies of P. oleracea from distant geographical locations and one cultivar were morphologically and physiologically characterized. C4 and CAM photosynthesis were monitored in plants exposed to well-watered, droughted and rewatered treatments, and data obtained were compared among individual genotypes. All subspecies expressed CAM in a fully-reversible manner. Transcript abundance of C4–CAM signature genes was shown to be a useful indicator of the C4–CAM–C4 switches in all genotypes. C4-related genes were down-regulated and subsequently fully expressed upon drought and rewatering, respectively. CAM-marker genes followed the opposite pattern. A gradient of morphological traits and drought-induced nighttime malate accumulation was observed across genotypes. Therefore, different combinations of CAM expression levels, plant sizes and shapes are available within the P. oleracea complex, which can be a valuable tool in the context of C4/CAM photosynthesis research.
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Affiliation(s)
- Renata Callegari Ferrari
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brasil
| | - Bruna Coelho Cruz
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brasil
| | | | - Thalyson Storl
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brasil
| | - Elisa Callegari Ferrari
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brasil
| | - Susanna F Boxall
- Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, Liverpool, UK
| | - James Hartwell
- Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, Liverpool, UK
| | - Luciano Freschi
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brasil.
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12
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Wu Y, Ma L, Liu Q, Sikder MM, Vestergård M, Zhou K, Wang Q, Yang X, Feng Y. Pseudomonas fluorescens promote photosynthesis, carbon fixation and cadmium phytoremediation of hyperaccumulator Sedum alfredii. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 726:138554. [PMID: 32305763 DOI: 10.1016/j.scitotenv.2020.138554] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 04/02/2020] [Accepted: 04/06/2020] [Indexed: 06/11/2023]
Abstract
Plant growth-promoting bacteria (PGPB) can promote photosynthesis and biomass production of hyperaccumulators, achieving enhanced phytoremediation efficiency of cadmium (Cd). A better understanding of the mechanisms controlling photosynthesis of hyperaccumulating plants by PGPB is necessary for developing strategies that promote the practical phytoextraction of Cd-polluted soils. In this study, chlorophyll fluorescence, gas exchange, and transcriptome sequencing were conducted to evaluate the physiological and transcriptional changes on photosynthesis and carbon fixation in hyperaccumulator Sedum alfredii after inoculation with PGPB Pseudomonas fluorescens. The results showed that bacterial inoculation significantly enhanced maximum quantum yield of PS II (Fv/Fm), effective quantum yield of PS II (ΦPSII), photochemical quenching (qP) and chlorophyll concentration, while reduced non-photochemical quenching (NPQ) of S. alfredii. Further, inoculation resulted in an increased net photosynthetic rates (Pn), intercellular CO2 concentration (Ci), transpiration rate (Tr) and stomatal conductance (Gs) of the studied plant. At the transcriptional level, 70 photosynthetic genes and 42 C4-pathway carbon fixation related genes were significantly up-regulated in response to inoculation, which could be the reason for enhanced photosynthesis and dry biomass. To sum up, this P. fluorescens strain can simultaneously promote growth and Cd uptake of S. alfredii, which can be a promising bacterial agent applied to Cd phytoremediation practices.
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Affiliation(s)
- Yingjie Wu
- MOE Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Department of Agroecology, Faculty of Technical Sciences, Aarhus University, Forsøgsvej 1, 4200 Slagelse, Denmark
| | - Luyao Ma
- MOE Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
| | - Qizhen Liu
- MOE Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
| | - Md Maniruzzaman Sikder
- Department of Agroecology, Faculty of Technical Sciences, Aarhus University, Forsøgsvej 1, 4200 Slagelse, Denmark; Mycology and Plant Pathology, Department of Botany, Jahangirnagar University, Dhaka, Bangladesh
| | - Mette Vestergård
- Department of Agroecology, Faculty of Technical Sciences, Aarhus University, Forsøgsvej 1, 4200 Slagelse, Denmark
| | - Kaiyue Zhou
- College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Qiong Wang
- MOE Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
| | - Xiaoe Yang
- MOE Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
| | - Ying Feng
- MOE Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
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13
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Ferrari RC, Bittencourt PP, Rodrigues MA, Moreno-Villena JJ, Alves FRR, Gastaldi VD, Boxall SF, Dever LV, Demarco D, Andrade SCS, Edwards EJ, Hartwell J, Freschi L. C 4 and crassulacean acid metabolism within a single leaf: deciphering key components behind a rare photosynthetic adaptation. THE NEW PHYTOLOGIST 2020; 225:1699-1714. [PMID: 31610019 DOI: 10.1111/nph.16265] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 10/07/2019] [Indexed: 06/10/2023]
Abstract
Although biochemically related, C4 and crassulacean acid metabolism (CAM) systems are expected to be incompatible. However, Portulaca species, including P. oleracea, operate C4 and CAM within a single leaf, and the mechanisms behind this unique photosynthetic arrangement remain largely unknown. Here, we employed RNA-seq to identify candidate genes involved exclusively or shared by C4 or CAM, and provided an in-depth characterization of their transcript abundance patterns during the drought-induced photosynthetic transitions in P. oleracea. Data revealed fewer candidate CAM-specific genes than those recruited to function in C4 . The putative CAM-specific genes were predominantly involved in night-time primary carboxylation reactions and malate movement across the tonoplast. Analysis of gene transcript-abundance regulation and photosynthetic physiology indicated that C4 and CAM coexist within a single P. oleracea leaf under mild drought conditions. Developmental and environmental cues were shown to regulate CAM expression in stems, whereas the shift from C4 to C4 -CAM hybrid photosynthesis in leaves was strictly under environmental control. Moreover, efficient starch turnover was identified as part of the metabolic adjustments required for CAM operation in both organs. These findings provide insights into C4 /CAM connectivity and compatibility, contributing to a deeper understanding of alternative ways to engineer CAM into C4 crop species.
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Affiliation(s)
- Renata C Ferrari
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, Brasil
| | - Priscila P Bittencourt
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, Brasil
| | - Maria A Rodrigues
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, Brasil
| | - Jose J Moreno-Villena
- Department of Ecology and Evolutionary Biology, Yale University, PO Box 208105, New Haven, CT, 06520, USA
| | - Frederico R R Alves
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, Brasil
| | - Vinícius D Gastaldi
- Departamento e Instituto de Psiquiatria, Hospital das Clínicas (HCFMUSP), Faculdade de Medicina, Universidade de São Paulo, São Paulo, 05403-903, Brasil
| | - Susanna F Boxall
- Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, UK
| | - Louisa V Dever
- Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, UK
| | - Diego Demarco
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, Brasil
| | - Sónia C S Andrade
- Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, Brasil
| | - Erika J Edwards
- Department of Ecology and Evolutionary Biology, Yale University, PO Box 208105, New Haven, CT, 06520, USA
| | - James Hartwell
- Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, UK
| | - Luciano Freschi
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, Brasil
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14
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Winter K, Sage RF, Edwards EJ, Virgo A, Holtum JAM. Facultative crassulacean acid metabolism in a C3-C4 intermediate. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:6571-6579. [PMID: 30820551 PMCID: PMC6883265 DOI: 10.1093/jxb/erz085] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 02/14/2019] [Indexed: 05/27/2023]
Abstract
The Portulacaceae enable the study of the evolutionary relationship between C4 and crassulacean acid metabolism (CAM) photosynthesis. Shoots of well-watered plants of the C3-C4 intermediate species Portulaca cryptopetala Speg. exhibit net uptake of CO2 solely during the light. CO2 fixation is primarily via the C3 pathway as indicated by a strong stimulation of CO2 uptake when shoots were provided with air containing 2% O2. When plants were subjected to water stress, daytime CO2 uptake was reduced and CAM-type net CO2 uptake in the dark occurred. This was accompanied by nocturnal accumulation of acid in both leaves and stems, also a defining characteristic of CAM. Following rewatering, net CO2 uptake in the dark ceased in shoots, as did nocturnal acidification of the leaves and stems. With this unequivocal demonstration of stress-related reversible, i.e. facultative, induction of CAM, P. cryptopetala becomes the first C3-C4 intermediate species reported to exhibit CAM. Portulaca molokiniensis Hobdy, a C4 species, also exhibited CAM only when subjected to water stress. Facultative CAM has now been demonstrated in all investigated species of Portulaca, which are well sampled from across the phylogeny. This strongly suggests that in Portulaca, a lineage in which species engage predominately in C4 photosynthesis, facultative CAM is ancestral to C4. In a broader context, it has now been demonstrated that CAM can co-exist in leaves that exhibit any of the other types of photosynthesis known in terrestrial plants: C3, C4 and C3-C4 intermediate.
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Affiliation(s)
- Klaus Winter
- Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama
| | - Rowan F Sage
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
| | - Erika J Edwards
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
| | - Aurelio Virgo
- Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama
| | - Joseph A M Holtum
- Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama
- College of Science and Engineering, James Cook University, Townsville, QLD, Australia
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15
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Winter K. Ecophysiology of constitutive and facultative CAM photosynthesis. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:6495-6508. [PMID: 30810162 DOI: 10.1093/jxb/erz002] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 01/08/2019] [Indexed: 05/24/2023]
Abstract
In plants exhibiting crassulacean acid metabolism (CAM), CAM photosynthesis almost always occurs together with C3 photosynthesis, and occasionally with C4 photosynthesis. Depending on species, ontogeny, and environment, CAM input to total carbon gain can vary from values of <1% to 100%. The wide range of CAM phenotypes between and within species is a fascinating example of functional diversity and plasticity, but poses a significant challenge when attempting to define CAM. CO2 gas exchange experiments designed for this review illustrate key patterns of CAM expression and highlight distinguishing features of constitutive and facultative CAM. Furthermore, they help to address frequently recurring questions on CAM terminology. The functional and evolutionary significance of contrasting CAM phenotypes and of intermediate states between extremes is discussed. Results from a study on nocturnal malate accumulation in 50 species of Aizoaceae exposed to drought and salinity stress suggest that facultative CAM is more widespread amongst vascular plants than previously thought.
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Affiliation(s)
- Klaus Winter
- Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama
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16
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Winter K, Garcia M, Virgo A, Holtum JAM. Operating at the very low end of the crassulacean acid metabolism spectrum: Sesuvium portulacastrum (Aizoaceae). JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:6561-6570. [PMID: 30535159 PMCID: PMC6883264 DOI: 10.1093/jxb/ery431] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 11/30/2018] [Indexed: 05/31/2023]
Abstract
Demonstration of crassulacean acid metabolism (CAM) in species with low usage of this system relative to C3-photosynthetic CO2 assimilation can be challenging experimentally but provides crucial information on the early steps of CAM evolution. Here, weakly expressed CAM was detected in the well-known pantropical coastal, leaf-succulent herb Sesuvium portulacastrum, demonstrating that CAM is present in the Sesuvioideae, the only sub-family of the Aizoaceae in which it had not yet been shown conclusively. In outdoor plots in Panama, leaves and stems of S. portulacastrum consistently exhibited a small degree of nocturnal acidification which, in leaves, increased during the dry season. In potted plants, nocturnal acidification was mainly facultative, as levels of acidification increased in a reversible manner following the imposition of short-term water-stress. In drought-stressed plants, nocturnal net CO2 exchange approached the CO2-compensation point, consistent with low rates of CO2 dark fixation sufficient to eliminate respiratory carbon loss. Detection of low-level CAM in S. portulacastrum adds to the growing number of species that cannot be considered C3 plants sensu stricto, although they obtain CO2 principally via the C3 pathway. Knowledge about the presence/absence of low-level CAM is critical when assessing trajectories of CAM evolution in lineages. The genus Sesuvium is of particular interest because it also contains C4 species.
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Affiliation(s)
- Klaus Winter
- Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama
| | - Milton Garcia
- Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama
| | - Aurelio Virgo
- Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama
| | - Joseph A M Holtum
- Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama
- Centre for Tropical Biodiversity and Climate Change, College of Science and Engineering, James Cook University, Townsville, Queensland, Australia
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17
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Davis SC, Simpson J, Gil-Vega KDC, Niechayev NA, van Tongerlo E, Castano NH, Dever LV, Búrquez A. Undervalued potential of crassulacean acid metabolism for current and future agricultural production. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:6521-6537. [PMID: 31087091 PMCID: PMC6883259 DOI: 10.1093/jxb/erz223] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 05/03/2019] [Indexed: 05/11/2023]
Abstract
The potential for crassulacean acid metabolism (CAM) to support resilient crops that meet demands for food, fiber, fuel, and pharmaceutical products far exceeds current production levels. This review provides background on five families of plants that express CAM, including examples of many species within these families that have potential agricultural uses. We summarize traditional uses, current developments, management practices, environmental tolerance ranges, and economic values of CAM species with potential commercial applications. The primary benefit of CAM in agriculture is high water use efficiency that allows for reliable crop yields even in drought conditions. Agave species, for example, grow in arid conditions and have been exploited for agricultural products in North and South America for centuries. Yet, there has been very little investment in agricultural improvement for most useful Agave varieties. Other CAM species that are already traded globally include Ananas comosus (pineapple), Aloe spp., Vanilla spp., and Opuntia spp., but there are far more with agronomic uses that are less well known and not yet developed commercially. Recent advances in technology and genomic resources provide tools to understand and realize the tremendous potential for using CAM crops to produce climate-resilient agricultural commodities in the future.
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Affiliation(s)
- Sarah C Davis
- Voinovich School of Leadership and Public Affairs, Ohio University, Athens, OH, USA
- Department of Environmental and Plant Biology, Ohio University, Athens, OH, USA
| | - June Simpson
- Department of Genetic Engineering, Cinvestav Unidad Irapuato, Irapuato, Guanajuato, México
| | | | - Nicholas A Niechayev
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, USA
| | - Evelien van Tongerlo
- Horticulture and Product Physiology, Wageningen University, Wageningen, The Netherlands
| | | | - Louisa V Dever
- Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, Liverpool, UK
| | - Alberto Búrquez
- Instituto de Ecología, Universidad Nacional Autónoma de México, Unidad Hermosillo, Sonora, México
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18
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Edwards EJ. Evolutionary trajectories, accessibility and other metaphors: the case of C 4 and CAM photosynthesis. THE NEW PHYTOLOGIST 2019; 223:1742-1755. [PMID: 30993711 DOI: 10.1111/nph.15851] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 03/18/2019] [Indexed: 05/24/2023]
Abstract
Are evolutionary outcomes predictable? Adaptations that show repeated evolutionary convergence across the Tree of Life provide a special opportunity to dissect the context surrounding their origins, and identify any commonalities that may predict why certain traits evolved many times in particular clades and yet never evolved in others. The remarkable convergence of C4 and Crassulacean Acid Metabolism (CAM) photosynthesis in vascular plants makes them exceptional model systems for understanding the repeated evolution of complex phenotypes. This review highlights what we have learned about the recurring assembly of C4 and CAM, focusing on the increasingly predictable stepwise evolutionary integration of anatomy and biochemistry. With the caveat that we currently understand C4 evolution better than we do CAM, I propose a general model that explains and unites C4 and CAM evolutionary trajectories. Available data suggest that anatomical modifications are the 'rate-limiting step' in each trajectory, which in large part determines the evolutionary accessibility of both syndromes. The idea that organismal structure exerts a primary influence on innovation is discussed in the context of other systems. Whether the rate-limiting step occurs early or late in the evolutionary assembly of a new phenotype may have profound implications for its distribution across the Tree of Life.
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Affiliation(s)
- Erika J Edwards
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect St, New Haven, CT, 06520-8105, USA
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19
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Hancock LP, Holtum JAM, Edwards EJ. The Evolution of CAM Photosynthesis in Australian Calandrinia Reveals Lability in C3+CAM Phenotypes and a Possible Constraint to the Evolution of Strong CAM. Integr Comp Biol 2019; 59:517-534. [DOI: 10.1093/icb/icz089] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Australian Calandrinia has radiated across the Australian continent during the last 30 Ma, and today inhabits most Australian ecosystems. Given its biogeographic range and reports of facultative Crassulacean acid metabolism (CAM) photosynthesis in multiple species, we hypothesized (1) that CAM would be widespread across Australian Calandrinia and that species, especially those that live in arid regions, would engage in strong CAM, and (2) that Australian Calandrinia would be an important lineage for informing on the CAM evolutionary trajectory. We cultivated 22 Australian Calandrinia species for a drought experiment. Using physiological measurements and δ13C values we characterized photosynthetic mode across these species, mapped the resulting character states onto a phylogeny, and characterized the climatic envelopes of species in their native ranges. Most species primarily utilize C3 photosynthesis, with CAM operating secondarily, often upregulated following drought. Several phylogenetically nested species are C3, indicating evolutionary losses of CAM. No strong CAM was detected in any of the species. Results highlight the limitations of δ13C surveys in detecting C3+CAM phenotypes, and the evolutionary lability of C3+CAM phenotypes. We propose a model of CAM evolution that allows for lability and reversibility among C3+CAM phenotypes and C3 and suggest that an annual life-cycle may preclude the evolution of strong CAM.
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Affiliation(s)
- Lillian P Hancock
- Department of Ecology and Evolutionary Biology, Brown University, Box G-W, Providence, RI 02912, USA
- Terrestrial Ecosystems and Climate Change, College of Marine and Environmental Sciences, James Cook University, Townsville, 4811, Queensland, Australia
| | - Joseph A M Holtum
- Terrestrial Ecosystems and Climate Change, College of Marine and Environmental Sciences, James Cook University, Townsville, 4811, Queensland, Australia
| | - Erika J Edwards
- Department of Ecology and Evolutionary Biology, Brown University, Box G-W, Providence, RI 02912, USA
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT PO Box 208105, 06520, USA
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20
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Flood PJ. Using natural variation to understand the evolutionary pressures on plant photosynthesis. CURRENT OPINION IN PLANT BIOLOGY 2019; 49:68-73. [PMID: 31284076 DOI: 10.1016/j.pbi.2019.06.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 05/23/2019] [Accepted: 06/03/2019] [Indexed: 06/09/2023]
Abstract
Photosynthesis is the gateway of the Sun's energy into the biosphere and the source of the ozone layer; thus it is both provider and protector of life as we know it. Despite its pivotal role we know surprisingly little about the genetic basis of variation in photosynthesis and the selective pressures giving rise to or maintaining this variation. In this review, I will briefly summarise our current knowledge of intraspecific and interspecific variation in photosynthesis to understand the main selective constraints on photosynthesis and what this means for the future of nature and agriculture in a changing world.
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Affiliation(s)
- Pádraic J Flood
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Cologne, Germany.
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21
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Niechayev NA, Pereira PN, Cushman JC. Understanding trait diversity associated with crassulacean acid metabolism (CAM). CURRENT OPINION IN PLANT BIOLOGY 2019; 49:74-85. [PMID: 31284077 DOI: 10.1016/j.pbi.2019.06.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 05/30/2019] [Accepted: 06/04/2019] [Indexed: 06/09/2023]
Abstract
Crassulacean acid metabolism (CAM) is a specialized mode of photosynthesis that exploits a temporal CO2 pump with nocturnal CO2 uptake and concentration to reduce photorespiration, improve water-use efficiency (WUE), and optimize the adaptability of plants to climates with seasonal or intermittent water limitations. CAM plants display a plastic continuum in the extent to which species engage in net nocturnal CO2 uptake that ranges from 0 to 100%. CAM plants also display diverse enzyme and organic acid and carbohydrate storage systems, which likely reflect the multiple, independent evolutionary origins of CAM. CAM is often accompanied by a diverse set of anatomical traits, such as tissue succulence and water-storage and water-capture strategies to attenuate drought. Other co-adaptive traits, such as thick cuticles, epicuticular wax, low stomatal density, high stomatal responsiveness, and shallow rectifier-like roots limit water loss under conditions of water deficit. Recommendations for future research efforts to better explore and understand the diversity of traits associated with CAM and CAM Biodesign efforts are presented.
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Affiliation(s)
- Nicholas A Niechayev
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Reno, NV 89557-0330, United States
| | - Paula N Pereira
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Reno, NV 89557-0330, United States
| | - John C Cushman
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Reno, NV 89557-0330, United States.
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22
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Bohley K, Schröder T, Kesselmeier J, Ludwig M, Kadereit G. C4-like photosynthesis and the effects of leaf senescence on C4-like physiology in Sesuvium sesuvioides (Aizoaceae). JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:1553-1565. [PMID: 30689935 PMCID: PMC6411375 DOI: 10.1093/jxb/erz011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Accepted: 01/07/2019] [Indexed: 05/10/2023]
Abstract
Sesuvium sesuvioides (Sesuvioideae, Aizoaceae) is a perennial, salt-tolerant herb distributed in flats, depressions, or disturbed habitats of southern Africa and the Cape Verdes. Based on carbon isotope values, it is considered a C4 species, despite a relatively high ratio of mesophyll to bundle sheath cells (2.7:1) in the portulacelloid leaf anatomy. Using leaf anatomy, immunocytochemistry, gas exchange measurements, and enzyme activity assays, we sought to identify the biochemical subtype of C4 photosynthesis used by S. sesuvioides and to explore the anatomical, physiological, and biochemical traits of young, mature, and senescing leaves, with the aim to elucidate the plasticity and possible limitations of the photosynthetic efficiency in this species. Assays indicated that S. sesuvioides employs the NADP-malic enzyme as the major decarboxylating enzyme. The activity of C4 enzymes, however, declined as leaves aged, and the proportion of water storage tissue increased while air space decreased. These changes suggest a functional shift from photosynthesis to water storage in older leaves. Interestingly, S. sesuvioides demonstrated CO2 compensation points ranging between C4 and C3-C4 intermediate values, and immunocytochemistry revealed labeling of the Rubisco large subunit in mesophyll cells. We hypothesize that S. sesuvioides represents a young C4 lineage with C4-like photosynthesis in which C3 and C4 cycles are running simultaneously in the mesophyll.
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Affiliation(s)
- Katharina Bohley
- Institut für Molekulare Physiologie, Johannes Gutenberg-Universität, Mainz, Germany
- Institut für Organismische und Molekulare Evolutionsbiologie, Johannes Gutenberg-Universität, Mainz, Germany
| | - Till Schröder
- Philipps-Universität, FB 16–Pharmazie, Marburg, Germany
| | - Jürgen Kesselmeier
- Max Planck Institute for Chemistry, Multiphase Chemistry Department, Mainz, Germany
| | - Martha Ludwig
- School of Molecular Sciences [310], University of Western Australia, Crawley, Western Australia, Australia
| | - Gudrun Kadereit
- Institut für Molekulare Physiologie, Johannes Gutenberg-Universität, Mainz, Germany
- Institut für Organismische und Molekulare Evolutionsbiologie, Johannes Gutenberg-Universität, Mainz, Germany
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Huang WM, Shao H, Zhou SN, Zhou Q, Fu WL, Zhang T, Jiang HS, Li W, Gontero B, Maberly SC. Different CO 2 acclimation strategies in juvenile and mature leaves of Ottelia alismoides. PHOTOSYNTHESIS RESEARCH 2018; 138:219-232. [PMID: 30078074 DOI: 10.1007/s11120-018-0568-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 07/28/2018] [Indexed: 06/08/2023]
Abstract
The freshwater macrophyte, Ottelia alismoides, is a bicarbonate user performing C4 photosynthesis in the light, and crassulacean acid metabolism (CAM) when acclimated to low CO2. The regulation of the three mechanisms by CO2 concentration was studied in juvenile and mature leaves. For mature leaves, the ratios of phosphoenolpyruvate carboxylase (PEPC) to ribulose-bisphosphate carboxylase/oxygenase (Rubisco) are in the range of that of C4 plants regardless of CO2 concentration (1.5-2.5 at low CO2, 1.8-3.4 at high CO2). In contrast, results for juvenile leaves suggest that C4 is facultative and only present under low CO2. pH-drift experiments showed that both juvenile and mature leaves can use bicarbonate irrespective of CO2 concentration, but mature leaves have a significantly greater carbon-extracting ability than juvenile leaves at low CO2. At high CO2, neither juvenile nor mature leaves perform CAM as indicated by lack of diurnal acid fluctuation. However, CAM was present at low CO2, though the fluctuation of titratable acidity in juvenile leaves (15-17 µequiv g-1 FW) was slightly but significantly lower than in mature leaves (19-25 µequiv g-1 FW), implying that the capacity to perform CAM increases as leaves mature. The increased CAM activity is associated with elevated PEPC activity and large diel changes in starch content. These results show that in O. alismoides, carbon-dioxide concentrating mechanisms are more effective in mature compared to juvenile leaves, and C4 is facultative in juvenile leaves but constitutive in mature leaves.
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Affiliation(s)
- Wen Min Huang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Hui Shao
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Aix Marseille Univ, CNRS, BIP, UMR 7281, 31 Chemin Joseph Aiguier, CS70071, 13402, Marseille Cedex 09, France
| | - Si Ning Zhou
- Sino-Danish Center, The University of Chinese Academy of Sciences, Beijing, 101400, China
| | - Qin Zhou
- School of Resources and Environmental Science, Hubei University, Wuhan, 430074, China
| | - Wen Long Fu
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Ting Zhang
- School of Resource and Environmental Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Hong Sheng Jiang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Wei Li
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Brigitte Gontero
- Aix Marseille Univ, CNRS, BIP, UMR 7281, 31 Chemin Joseph Aiguier, CS70071, 13402, Marseille Cedex 09, France.
| | - Stephen C Maberly
- Lake Ecosystems Group, Centre for Ecology & Hydrology, Lancaster Environment Centre, Library Avenue, Lancaster, Bailrigg, LA1 4AP, UK.
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Holtum JAM, Hancock LP, Edwards EJ, Winter K. Crassulacean acid metabolism in the Basellaceae (Caryophyllales). PLANT BIOLOGY (STUTTGART, GERMANY) 2018; 20:409-414. [PMID: 29369469 DOI: 10.1111/plb.12698] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 01/22/2018] [Indexed: 06/07/2023]
Abstract
C4 and crassulacean acid metabolism (CAM) have evolved in the order Caryophyllales many times but neither C4 nor CAM have been recorded for the Basellaceae, a small family in the CAM-rich sub-order Portulacineae. 24 h gas exchange and day-night changes in titratable acidity were measured in leaves of Anredera baselloides exposed to wet-dry-wet cycles. While net CO2 uptake was restricted to the light period in well-watered plants, net CO2 fixation in the dark, accompanied by significant nocturnal increases in leaf acidity, developed in droughted plants. Plants reverted to solely C3 photosynthesis upon rewatering. The reversible induction of nocturnal net CO2 uptake by drought stress indicates that this species is able to exhibit CAM in a facultative manner. This is the first report of CAM in a member of the Basellaceae.
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Affiliation(s)
- J A M Holtum
- College of Science and Engineering, James Cook University, Townsville, Qld, Australia
- Smithsonian Tropical Research Institute, Panama City, Panama
| | - L P Hancock
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA
| | - E J Edwards
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
| | - K Winter
- Smithsonian Tropical Research Institute, Panama City, Panama
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Goolsby EW, Moore AJ, Hancock LP, De Vos JM, Edwards EJ. Molecular evolution of key metabolic genes during transitions to C 4 and CAM photosynthesis. AMERICAN JOURNAL OF BOTANY 2018; 105:602-613. [PMID: 29660114 DOI: 10.1002/ajb2.1051] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 12/12/2017] [Indexed: 06/08/2023]
Abstract
PREMISE OF THE STUDY Next-generation sequencing facilitates rapid production of well-sampled phylogenies built from very large genetic data sets, which can then be subsequently exploited to examine the molecular evolution of the genes themselves. We present an evolutionary analysis of 83 gene families (19 containing carbon-concentrating mechanism (CCM) genes, 64 containing non-CCM genes) in the portullugo clade (Caryophyllales), a diverse lineage of mostly arid-adapted plants that contains multiple evolutionary origins of all known photosynthesis types in land plants (C3 , C4 , CAM, C4 -CAM, and various intermediates). METHODS We inferred a phylogeny of 197 individuals from 167 taxa using coalescent-based approaches and individual gene family trees using maximum likelihood. Positive selection analyses were conducted on individual gene family trees with a mixed effects model of evolution (MEME). We devised new indices to compare levels of convergence and prevalence of particular residues between CCM and non-CCM genes and between species with different photosynthetic pathways. KEY RESULTS Contrary to expectations, there were no significant differences in the levels of positive selection detected in CCM versus non-CCM genes. However, we documented a significantly higher level of convergent amino acid substitutions in CCM genes, especially in C4 taxa. CONCLUSIONS Our analyses reveal a new suite of amino acid residues putatively important for C4 and CAM function. We discuss both the advantages and challenges of using targeted enrichment sequence data for exploratory studies of molecular evolution.
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Affiliation(s)
- Eric W Goolsby
- Brown University, Department of Ecology and Evolutionary Biology, Box G-W, 80 Waterman St, Providence, Rhode Island, 02912, USA
- Yale University, Department of Ecology and Evolutionary Biology, 165 Prospect Street, New Haven, Connecticut, 06511, USA
| | - Abigail J Moore
- Brown University, Department of Ecology and Evolutionary Biology, Box G-W, 80 Waterman St, Providence, Rhode Island, 02912, USA
- University of Oklahoma, Department of Microbiology and Plant Biology and Oklahoma Biological Survey, 136 George Lynn Cross Hall, 770 Van Vleet Oval, Norman, Oklahoma, 73019, USA
| | - Lillian P Hancock
- Brown University, Department of Ecology and Evolutionary Biology, Box G-W, 80 Waterman St, Providence, Rhode Island, 02912, USA
| | - Jurriaan M De Vos
- Brown University, Department of Ecology and Evolutionary Biology, Box G-W, 80 Waterman St, Providence, Rhode Island, 02912, USA
- University of Basel, Department of Environmental Sciences-Botany, Bernoullistrasse 32, 4056, Basel, Switzerland
| | - Erika J Edwards
- Brown University, Department of Ecology and Evolutionary Biology, Box G-W, 80 Waterman St, Providence, Rhode Island, 02912, USA
- Yale University, Department of Ecology and Evolutionary Biology, 165 Prospect Street, New Haven, Connecticut, 06511, USA
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26
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Holtum JAM, Hancock LP, Edwards EJ, Winter K. Facultative CAM photosynthesis (crassulacean acid metabolism) in four species of Calandrinia, ephemeral succulents of arid Australia. PHOTOSYNTHESIS RESEARCH 2017; 134:17-25. [PMID: 28871459 DOI: 10.1007/s11120-017-0359-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 02/14/2017] [Indexed: 06/07/2023]
Abstract
Crassulacean acid metabolism (CAM) was demonstrated in four small endemic Australian terrestrial succulents from the genus Calandrinia (Montiaceae) viz. C. creethiae, C. pentavalvis, C. quadrivalvis and C. reticulata. CAM was substantiated by measurements of CO2 gas-exchange and nocturnal acidification. In all species, the expression of CAM was overwhelmingly facultative in that nocturnal H+ accumulation was greatest in droughted plants and zero, or close to zero, in plants that were well-watered, including plants that had been droughted and were subsequently rewatered, i.e. the inducible component was proven to be reversible. Gas-exchange measurements complemented the determinations of acidity. In all species, net CO2 uptake was restricted to the light in well-watered plants, and cessation of watering was followed by a progressive reduction of CO2 uptake in the light and a reduction in nocturnal CO2 efflux. In C. creethiae, C. pentavalvis and C. reticulata net CO2 assimilation was eventually observed in the dark, whereas in C. quadrivalvis nocturnal CO2 exchange approached the compensation point but did not transition to net CO2 gain. Following rewatering, all species returned to their original well-watered CO2 exchange pattern of net CO2 uptake restricted solely to the light. In addition to facultative CAM, C. quadrivalvis and C. reticulata exhibited an extremely small constitutive CAM component as demonstrated by the nocturnal accumulation in well-watered plants of small amounts of acidity and by the curved pattern of the nocturnal course of CO2 efflux. It is suggested that low-level CAM and facultative CAM are more common within the Australian succulent flora, and perhaps the world succulent flora, than has been previously assumed.
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Affiliation(s)
- Joseph A M Holtum
- College of Science and Engineering, James Cook University, Townsville, QLD, 4811, Australia.
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama.
| | - Lillian P Hancock
- Department of Ecology and Evolutionary Biology, Brown University, Box G-W, Providence, RI, 02912, USA
| | - Erika J Edwards
- Department of Ecology and Evolutionary Biology, Brown University, Box G-W, Providence, RI, 02912, USA
| | - Klaus Winter
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama
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