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Sunda WG, Marchetti A. Proton-pumping rhodopsins promote the growth and survival of phytoplankton in a highly variable ocean. THE ISME JOURNAL 2024; 18:wrae079. [PMID: 38696358 PMCID: PMC11104272 DOI: 10.1093/ismejo/wrae079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2024] [Revised: 04/23/2024] [Accepted: 04/29/2024] [Indexed: 05/04/2024]
Affiliation(s)
- William G Sunda
- Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States
| | - Adrian Marchetti
- Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States
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2
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Strauss J, Deng L, Gao S, Toseland A, Bachy C, Zhang C, Kirkham A, Hopes A, Utting R, Joest EF, Tagliabue A, Löw C, Worden AZ, Nagel G, Mock T. Plastid-localized xanthorhodopsin increases diatom biomass and ecosystem productivity in iron-limited surface oceans. Nat Microbiol 2023; 8:2050-2066. [PMID: 37845316 PMCID: PMC10627834 DOI: 10.1038/s41564-023-01498-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 09/12/2023] [Indexed: 10/18/2023]
Abstract
Microbial rhodopsins are photoreceptor proteins that convert light into biological signals or energy. Proteins of the xanthorhodopsin family are common in eukaryotic photosynthetic plankton including diatoms. However, their biological role in these organisms remains elusive. Here we report on a xanthorhodopsin variant (FcR1) isolated from the polar diatom Fragilariopsis cylindrus. Applying a combination of biophysical, biochemical and reverse genetics approaches, we demonstrate that FcR1 is a plastid-localized proton pump which binds the chromophore retinal and is activated by green light. Enhanced growth of a Thalassiora pseudonana gain-of-function mutant expressing FcR1 under iron limitation shows that the xanthorhodopsin proton pump supports growth when chlorophyll-based photosynthesis is iron-limited. The abundance of xanthorhodopsin transcripts in natural diatom communities of the surface oceans is anticorrelated with the availability of dissolved iron. Thus, we propose that these proton pumps convey a fitness advantage in regions where phytoplankton growth is limited by the availability of dissolved iron.
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Affiliation(s)
- Jan Strauss
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK.
- Ocean EcoSystems Biology Unit, RD3, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany.
- European Molecular Biology Laboratory (EMBL), Hamburg Unit c/o Deutsches Elektronen Synchrotron (DESY), Hamburg, Germany.
- Centre for Structural Systems Biology (CSSB), Hamburg, Germany.
- German Maritime Centre, Hamburg, Germany.
| | - Longji Deng
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Shiqiang Gao
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, Wuerzburg, Germany
| | - Andrew Toseland
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Charles Bachy
- Ocean EcoSystems Biology Unit, RD3, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
- Sorbonne Université, CNRS, FR2424, Station biologique de Roscoff, Roscoff, France
| | - Chong Zhang
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, Wuerzburg, Germany
| | - Amy Kirkham
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Amanda Hopes
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Robert Utting
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Eike F Joest
- Department of Biology, Biocenter, University of Würzburg, Wuerzburg, Germany
| | | | - Christian Löw
- European Molecular Biology Laboratory (EMBL), Hamburg Unit c/o Deutsches Elektronen Synchrotron (DESY), Hamburg, Germany
- Centre for Structural Systems Biology (CSSB), Hamburg, Germany
| | - Alexandra Z Worden
- Ocean EcoSystems Biology Unit, RD3, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
- Max Planck Institute for Evolutionary Biology, Plön, Germany
- Marine Biological Laboratory, Woods Hole, MA, USA
| | - Georg Nagel
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, Wuerzburg, Germany
| | - Thomas Mock
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK.
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3
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Andrew SM, Moreno CM, Plumb K, Hassanzadeh B, Gomez-Consarnau L, Smith SN, Schofield O, Yoshizawa S, Fujiwara T, Sunda WG, Hopkinson BM, Septer AN, Marchetti A. Widespread use of proton-pumping rhodopsin in Antarctic phytoplankton. Proc Natl Acad Sci U S A 2023; 120:e2307638120. [PMID: 37722052 PMCID: PMC10523587 DOI: 10.1073/pnas.2307638120] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2023] [Accepted: 08/13/2023] [Indexed: 09/20/2023] Open
Abstract
Photosynthetic carbon (C) fixation by phytoplankton in the Southern Ocean (SO) plays a critical role in regulating air-sea exchange of carbon dioxide and thus global climate. In the SO, photosynthesis (PS) is often constrained by low iron, low temperatures, and low but highly variable light intensities. Recently, proton-pumping rhodopsins (PPRs) were identified in marine phytoplankton, providing an alternate iron-free, light-driven source of cellular energy. These proteins pump protons across cellular membranes through light absorption by the chromophore retinal, and the resulting pH energy gradient can then be used for active membrane transport or for synthesis of adenosine triphosphate. Here, we show that PPR is pervasive in Antarctic phytoplankton, especially in iron-limited regions. In a model SO diatom, we found that it was localized to the vacuolar membrane, making the vacuole a putative alternative phototrophic organelle for light-driven production of cellular energy. Unlike photosynthetic C fixation, which decreases substantially at colder temperatures, the proton transport activity of PPR was unaffected by decreasing temperature. Cellular PPR levels in cultured SO diatoms increased with decreasing iron concentrations and energy production from PPR photochemistry could substantially augment that of PS, especially under high light intensities, where PS is often photoinhibited. PPR gene expression and high retinal concentrations in phytoplankton in SO waters support its widespread use in polar environments. PPRs are an important adaptation of SO phytoplankton to growth and survival in their cold, iron-limited, and variable light environment.
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Affiliation(s)
- Sarah M. Andrew
- Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC27599
| | - Carly M. Moreno
- Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC27599
| | - Kaylie Plumb
- Department of Marine Sciences, University of Georgia, Athens, GA30602
| | - Babak Hassanzadeh
- Department of Biological Sciences, University of Southern California, Log Angeles, CA90089
| | - Laura Gomez-Consarnau
- Department of Biological Sciences, University of Southern California, Log Angeles, CA90089
- Departamento de Oceanografía Biológica, Centro de Investigación Científca y de Educación Superior de Ensenada, Ensenada, Baja California22860, Mexico
| | - Stephanie N. Smith
- Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC27599
| | - Oscar Schofield
- Department of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ08901
| | - Susumu Yoshizawa
- Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba277-8564, Japan
| | - Takayoshi Fujiwara
- Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba277-8564, Japan
| | - William G. Sunda
- Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC27599
| | | | - Alecia N. Septer
- Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC27599
| | - Adrian Marchetti
- Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC27599
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Ma M, Li H, Wang C, Li T, Wang J, Yuan H, Yu L, Wang J, Li L, Lin S. A comparative study reveals the relative importance of prokaryotic and eukaryotic proton pump rhodopsins in a subtropical marginal sea. ISME COMMUNICATIONS 2023; 3:79. [PMID: 37596487 PMCID: PMC10439184 DOI: 10.1038/s43705-023-00292-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 08/02/2023] [Accepted: 08/04/2023] [Indexed: 08/20/2023]
Abstract
Proton-pump rhodopsin (PPR) in marine microbes can convert solar energy to bioavailable chemical energy. Whereas bacterial PPR has been extensively studied, counterparts in microeukaryotes are less explored, and the relative importance of the two groups is poorly understood. Here, we sequenced whole-assemblage metatranscriptomes and investigated the diversity and expression dynamics of PPR in microbial eukaryotes and prokaryotes at a continental shelf and a slope site in the northern South China Sea. Data showed the whole PPRs transcript pool was dominated by Proteorhodopsins and Xanthorhodopsins, followed by Bacteriorhodopsin-like proteins, dominantly contributed by prokaryotes both in the number and expression levels of PPR unigenes, although at the continental slope station, microeukaryotes and prokaryotes contributed similarly in transcript abundance. Furthermore, eukaryotic PPRs are mainly contributed by dinoflagellates and showed significant correlation with nutrient concentrations. Green light-absorbing PPRs were mainly distributed in >3 μm organisms (including microeukaryotes and their associated bacteria), especially at surface layer at the shelf station, whereas blue light-absorbing PPRs dominated the <3 μm (mainly bacterial) communities at both study sites, especially at deeper layers at the slope station. Our study portrays a comparative PPR genotype and expression landscape for prokaryotes and eukaryotes in a subtropical marginal sea, suggesting PPR's role in niche differentiation and adaptation among marine microbes.
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Affiliation(s)
- Minglei Ma
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, 361102, China
| | - Hongfei Li
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, 361102, China
- National Engineering Research Center for Marine Aquaculture, Zhejiang Ocean University, Zhoushan, 316022, China
| | - Cong Wang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, 361102, China
| | - Tangcheng Li
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, 361102, China
- Biology Department and Institute of Marine Sciences, College of Science, Shantou University, Shantou, 515063, China
| | - Jierui Wang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, 361102, China
| | - Huatao Yuan
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, 361102, China
| | - Liying Yu
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, 361102, China
- Central Laboratory, the Second Affiliated Hospital of Fujian Medical University, Quanzhou, 362000, China
| | - Jingtian Wang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, 361102, China
| | - Ling Li
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, 361102, China
| | - Senjie Lin
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, 361102, China.
- Laboratory of Marine Biology and Biotechnology, Qingdao National Laboratory of Marine Science and Technology, Qingdao, 266237, China.
- Department of Marine Sciences, University of Connecticut, Groton, CT, 06340, USA.
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5
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Hassanzadeh B, Thomson B, Deans F, Wenley J, Lockwood S, Currie K, Morales SE, Steindler L, Sañudo-Wilhelmy SA, Baltar F, Gómez-Consarnau L. Microbial rhodopsins are increasingly favoured over chlorophyll in High Nutrient Low Chlorophyll waters. ENVIRONMENTAL MICROBIOLOGY REPORTS 2021; 13:401-406. [PMID: 33870657 DOI: 10.1111/1758-2229.12948] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 03/26/2021] [Accepted: 04/04/2021] [Indexed: 05/16/2023]
Abstract
Microbial rhodopsins are simple light-harvesting complexes that, unlike chlorophyll photosystems, have no iron requirements for their synthesis and phototrophic functions. Here, we report the environmental concentrations of rhodopsin along the Subtropical Frontal Zone off New Zealand, where Subtropical waters encounter the iron-limited Subantarctic High Nutrient Low Chlorophyll (HNLC) region. Rhodopsin concentrations were highest in HNLC waters where chlorophyll-a concentrations were lowest. Furthermore, while the ratio of rhodopsin to chlorophyll-a photosystems was on average 20 along the transect, this ratio increased to over 60 in HNLC waters. We further show that microbial rhodopsins are abundant in both picoplankton (0.2-3 μm) and in the larger (>3 μm) size fractions of the microbial community containing eukaryotic plankton and/or particle-attached prokaryotes. These findings suggest that rhodopsin phototrophy could be critical for microbial plankton to adapt to resource-limiting environments where photosynthesis and possibly cellular respiration are impaired.
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Affiliation(s)
- Babak Hassanzadeh
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Blair Thomson
- Department of Marine Science, University of Otago, Dunedin, 9016, New Zealand
| | - Fenella Deans
- Department of Marine Science, University of Otago, Dunedin, 9016, New Zealand
| | - Jess Wenley
- Department of Marine Science, University of Otago, Dunedin, 9016, New Zealand
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - Scott Lockwood
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - Kim Currie
- National Institute of Water and Atmospheric Research, Dunedin, New Zealand
| | - Sergio E Morales
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - Laura Steindler
- Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, BC, Israel
| | - Sergio A Sañudo-Wilhelmy
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Federico Baltar
- Department of Functional & Evolutionary Ecology, University of Vienna, Vienna, Austria
| | - Laura Gómez-Consarnau
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
- Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada, BC, México
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6
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Molecular electrets – Why do dipoles matter for charge transfer and excited-state dynamics? J Photochem Photobiol A Chem 2020. [DOI: 10.1016/j.jphotochem.2020.112779] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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7
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Koedooder C, Van Geersdaële R, Guéneuguès A, Bouget FY, Obernosterer I, Blain S. The interplay between iron limitation, light and carbon in the proteorhodopsin-containing Photobacterium angustum S14. FEMS Microbiol Ecol 2020; 96:5847691. [DOI: 10.1093/femsec/fiaa103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Accepted: 05/25/2020] [Indexed: 01/01/2023] Open
Abstract
ABSTRACTIron (Fe) limitation is known to affect heterotrophic bacteria within the respiratory electron transport chain, therefore strongly impacting the overall intracellular energy production. We investigated whether the gene expression pattern of the light-sensitive proton pump, proteorhodopsin (PR), is influenced by varying light, carbon and Fe concentrations in the marine bacterium Photobacterium angustum S14 and whether PR can alleviate the physiological processes associated with Fe starvation. Our results show that the gene expression of PR increases as cells enter the stationary phase, irrespective of Fe-replete or Fe-limiting conditions. This upregulation is coupled to a reduction in cell size, indicating that PR gene regulation is associated with a specific starvation-stress response. We provide experimental evidence that PR gene expression does not result in an increased growth rate, cell abundance, enhanced survival or ATP concentration within the cell in either Fe-replete or Fe-limiting conditions. However, independent of PR gene expression, the presence of light did influence bacterial growth rates and maximum cell abundances under varying Fe regimes. Our observations support previous results indicating that PR phototrophy seems to play an important role within the stationary phase for several members of the Vibrionaceae family, but that the exact role of PR in Fe limitation remains to be further explored.
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Affiliation(s)
- Coco Koedooder
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, Banyuls/mer, France
- The Fredy and Nadine Herrmann Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Rémy Van Geersdaële
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, Banyuls/mer, France
| | - Audrey Guéneuguès
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, Banyuls/mer, France
| | - François-Yves Bouget
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, Banyuls/mer, France
| | - Ingrid Obernosterer
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, Banyuls/mer, France
| | - Stéphane Blain
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, Banyuls/mer, France
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8
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Gómez-Consarnau L, Raven JA, Levine NM, Cutter LS, Wang D, Seegers B, Arístegui J, Fuhrman JA, Gasol JM, Sañudo-Wilhelmy SA. Microbial rhodopsins are major contributors to the solar energy captured in the sea. SCIENCE ADVANCES 2019; 5:eaaw8855. [PMID: 31457093 PMCID: PMC6685716 DOI: 10.1126/sciadv.aaw8855] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 06/28/2019] [Indexed: 05/19/2023]
Abstract
All known phototrophic metabolisms on Earth rely on one of three categories of energy-converting pigments: chlorophyll-a (rarely -d), bacteriochlorophyll-a (rarely -b), and retinal, which is the chromophore in rhodopsins. While the significance of chlorophylls in solar energy capture has been studied for decades, the contribution of retinal-based phototrophy to this process remains largely unexplored. We report the first vertical distributions of the three energy-converting pigments measured along a contrasting nutrient gradient through the Mediterranean Sea and the Atlantic Ocean. The highest rhodopsin concentrations were observed above the deep chlorophyll-a maxima, and their geographical distribution tended to be inversely related to that of chlorophyll-a. We further show that proton-pumping proteorhodopsins potentially absorb as much light energy as chlorophyll-a-based phototrophy and that this energy is sufficient to sustain bacterial basal metabolism. This suggests that proteorhodopsins are a major energy-transducing mechanism to harvest solar energy in the surface ocean.
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Affiliation(s)
- Laura Gómez-Consarnau
- Departamento de Oceanografía Biológica, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), 22860 Ensenada, Baja California, México
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - John A. Raven
- Division of Plant Science, University of Dundee at the James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK
- Climate Change Cluster, University of Technology Sydney, Ultimo, NSW 2007, Australia
- School of Biological Sciences, University of Western Australia, 25 Stirling Highway, Crawley, WA 6009, Australia
| | - Naomi M. Levine
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Lynda S. Cutter
- Department of Earth Science, University of Southern California, Los Angeles, CA 90089, USA
| | - Deli Wang
- State Key Laboratory of Marine Environmental Science, Xiamen University, 422 Siming Nanlu, 361005 Xiamen, China
| | - Brian Seegers
- The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Javier Arístegui
- Instituto de Oceanografía y Cambio Global (IOCAG), Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain
| | - Jed A. Fuhrman
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Josep M. Gasol
- Institut de Ciències del Mar-CSIC, ES-08003 Barcelona, Catalonia, Spain
- Centre for Marine Ecosystems Research, School of Science, Edith Cowan University, Joondalup, WA, Australia
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9
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Raven JA. Chloride: essential micronutrient and multifunctional beneficial ion. JOURNAL OF EXPERIMENTAL BOTANY 2017; 38:359-367. [PMID: 28040799 DOI: 10.1093/jxb/erw421] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Cl− is an essential micronutrient for oxygenic photolithotrophs. About half of global primary productivity is carried out by oxygenic photolithotrophs exposed to saline waters with Cl− concentrations orders of magnitude higher than that needed to satisfy the micronutrient requirement. The other half of primary productivity involves terrestrial and freshwater glycophytes sometimes in environments containing significantly more Cl− than is needed for the micronutrient requirement, but less than the toxic Cl– concentration for glycophytes. Intracellular Cl− acts in regulation of cell turgor and volume, including that of stomatal and pulvinar nastic movements, is a major ion in streptophyte and ulvophycean action potentials, and is involved in ion currents flowing around apices of pollen tubes and Acetabularia cells. More work is needed on the essentiality of Cl− in these processes, as well as the recent finding that Cl− at 1–5 mol m−3 increases water use efficiency of growth and leaf area in Nicotiana tabacum.
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Affiliation(s)
- John A Raven
- Division of Plant Science, University of Dundee at the James Hutton Institute, Invergowrie, Dundee, UK
- School of Plant Biology, University of Western Australia MO84, Stirling Highway. Crawley, WA, Australia
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10
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Marchetti A, Catlett D, Hopkinson BM, Ellis K, Cassar N. Marine diatom proteorhodopsins and their potential role in coping with low iron availability. THE ISME JOURNAL 2015; 9:2745-8. [PMID: 26023874 PMCID: PMC4817633 DOI: 10.1038/ismej.2015.74] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 02/16/2015] [Accepted: 03/30/2015] [Indexed: 01/02/2023]
Abstract
Proteorhodopsins (PR) are retinal-binding membrane proteins that function as light-driven proton pumps to generate energy for metabolism and growth. Recently PR-like genes have been identified in some marine eukaryotic protists, including diatoms, dinoflagellates, haptophytes and cryptophytes. These rhodopsins are homologous to green-light-absorbing, ATP-generating PRs present within bacteria. Here we show that in the oceanic diatom Pseudo-nitzschia granii, PR-like gene and protein expressions increase appreciably under iron limitation. In a survey of available transcriptomes, PR-like genes in diatoms are generally found in isolates from marine habitats where seasonal to chronic growth limitation by the micronutrient iron is prevalent, yet similar biogeographical patterns are not apparent in other phytoplankton taxa. We propose that rhodopsin-based phototrophy could account for a proportion of energy synthesis in marine eukaryotic photoautotrophs, especially when photosynthesis is compromised by low iron availability. This alternative ATP-generating pathway could have significant effects on plankton community structure and global ocean carbon cycling.
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Affiliation(s)
- Adrian Marchetti
- Department of Marine Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Dylan Catlett
- Department of Marine Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Brian M Hopkinson
- Department of Marine Sciences, University of Georgia, Athens, GA, USA
| | - Kelsey Ellis
- Department of Marine Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Nicolas Cassar
- Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, NC, USA
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11
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Vogt A, Wietek J, Hegemann P. Gloeobacter rhodopsin, limitation of proton pumping at high electrochemical load. Biophys J 2013; 105:2055-63. [PMID: 24209850 PMCID: PMC3824519 DOI: 10.1016/j.bpj.2013.08.031] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 08/05/2013] [Accepted: 08/28/2013] [Indexed: 12/29/2022] Open
Abstract
We studied the photocurrents of a cyanobacterial rhodopsin Gloeobacter violaceus (GR) in Xenopus laevis oocytes and HEK-293 cells. This protein is a light-driven proton pump with striking similarities to marine proteorhodopsins, including the D121-H87 cluster of the retinal Schiff base counterion and a glutamate at position 132 that acts as a proton donor for chromophore reprotonation during the photocycle. Interestingly, at low extracellular pH(o) and negative voltage, the proton flux inverted and directed inward. Using electrophysiological measurements of wild-type and mutant GR, we demonstrate that the electrochemical gradient limits outward-directed proton pumping and converts it into a purely passive proton influx. This conclusion contradicts the contemporary paradigm that at low pH, proteorhodopsins actively transport H(+) into cells. We identified E132 and S77 as key residues that allow inward directed diffusion. Substitution of E132 with aspartate or S77 with either alanine or cysteine abolished the inward-directed current almost completely. The proton influx is likely caused by the pK(a) of E132 in GR, which is lower than that of other microbial ion pumping rhodopsins. The advantage of such a low pK(a) is an acceleration of the photocycle and high pump turnover at high light intensities.
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Affiliation(s)
| | | | - Peter Hegemann
- Institute of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Berlin, Germany
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12
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Li S, Zhang YJ, Sack L, Scoffoni C, Ishida A, Chen YJ, Cao KF. The heterogeneity and spatial patterning of structure and physiology across the leaf surface in giant leaves of Alocasia macrorrhiza. PLoS One 2013; 8:e66016. [PMID: 23776594 PMCID: PMC3679039 DOI: 10.1371/journal.pone.0066016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2012] [Accepted: 05/06/2013] [Indexed: 11/18/2022] Open
Abstract
Leaf physiology determines the carbon acquisition of the whole plant, but there can be considerable variation in physiology and carbon acquisition within individual leaves. Alocasia macrorrhiza (L.) Schott is an herbaceous species that can develop very large leaves of up to 1 m in length. However, little is known about the hydraulic and photosynthetic design of such giant leaves. Based on previous studies of smaller leaves, and on the greater surface area for trait variation in large leaves, we hypothesized that A. macrorrhiza leaves would exhibit significant heterogeneity in structure and function. We found evidence of reduced hydraulic supply and demand in the outer leaf regions; leaf mass per area, chlorophyll concentration, and guard cell length decreased, as did stomatal conductance, net photosynthetic rate and quantum efficiency of photosystem II. This heterogeneity in physiology was opposite to that expected from a thinner boundary layer at the leaf edge, which would have led to greater rates of gas exchange. Leaf temperature was 8.8°C higher in the outer than in the central region in the afternoon, consistent with reduced stomatal conductance and transpiration caused by a hydraulic limitation to the outer lamina. The reduced stomatal conductance in the outer regions would explain the observed homogeneous distribution of leaf water potential across the leaf surface. These findings indicate substantial heterogeneity in gas exchange across the leaf surface in large leaves, greater than that reported for smaller-leafed species, though the observed structural differences across the lamina were within the range reported for smaller-leafed species. Future work will determine whether the challenge of transporting water to the outer regions can limit leaf size for plants experiencing drought, and whether the heterogeneity of function across the leaf surface represents a particular disadvantage for large simple leaves that might explain their global rarity, even in resource-rich environments.
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Affiliation(s)
- Shuai Li
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui Province, China
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan Province, China
| | - Yong-Jiang Zhang
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan Province, China
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Lawren Sack
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Christine Scoffoni
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Atsushi Ishida
- Center for Ecological Research, Kyoto University, Otsu, Shiga, Japan
| | - Ya-Jun Chen
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan Province, China
- Graduate University of Chinese Academy of Sciences, Beijing, China
| | - Kun-Fang Cao
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan Province, China
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, and College of Forestry, Guangxi University, Nanning, Guangxi Province, China
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13
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Raven JA. Iron acquisition and allocation in stramenopile algae. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:2119-27. [PMID: 23658428 DOI: 10.1093/jxb/ert121] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The essential element iron has a low biological availability in the surface ocean where photosynthetic organisms live. Recent advances in our understanding of iron acquisition mechanisms in brown algae and diatoms (stramenopile algae) show the importance of the reduction of ferric to ferrous iron prior to, or during, transport in the uptake process. The uses of iron in photosynthetic stramenopiles resembles that in other oxygenic organisms, although (with the exception of the diatom Thalassiosira oceanica from an iron-deficient part of the ocean) they lack plastocyanin, instead using cytochrome c 6, This same diatom further economizes genotypically on the use of iron in photosynthesis by decreasing the expression of photosystem I, cytochrome c 6, and the cytochrome b 6 f complex per cell and per photosystem II relative to the coastal Thalassiosira pseudonana; similar changes occur phenotypically in response to iron deficiency in other diatoms such as Phaeodactylum tricornutum. In some diatoms grown under iron-limiting conditions, essentially all of the iron in the cells can be accounted for by the iron occurring in catalytic proteins. However, stramenopiles can store iron. Genomic studies show that pennate, but not centric, diatoms have the iron storage protein ferritin. While Mössbauer and X-ray analysis of (57)Fe-labelled Ectocarpus siliculosus shows iron in an amorphous mineral phase resembling the core of ferritin, the genome shows no protein with significant sequence similarity to ferritin.
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Affiliation(s)
- John A Raven
- Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK.
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Brown Dwarfs and Black Smokers: The Potential for Photosynthesis Using Radiation from Low-Temperature Black Bodies. HABITABILITY OF OTHER PLANETS AND SATELLITES 2013. [DOI: 10.1007/978-94-007-6546-7_15] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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15
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Bernát G, Schreiber U, Sendtko E, Stadnichuk IN, Rexroth S, Rögner M, Koenig F. Unique properties vs. common themes: the atypical cyanobacterium Gloeobacter violaceus PCC 7421 is capable of state transitions and blue-light-induced fluorescence quenching. PLANT & CELL PHYSIOLOGY 2012; 53:528-542. [PMID: 22302714 DOI: 10.1093/pcp/pcs009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The atypical unicellular cyanobacterium Gloeobacter violaceus PCC 7421, which diverged very early during the evolution of cyanobacteria, can be regarded as a key organism for understanding many structural, functional, regulatory and evolutionary aspects of oxygenic photosynthesis. In the present work, the performance of two basic photosynthetic adaptation/protection mechanisms, common to all other oxygenic photoautrophs, had been challenged in this ancient cyanobacterium which lacks thylakoid membranes: state transitions and non-photochemical fluorescence quenching. Both low temperature fluorescence spectra and room temperature fluorescence transients show that G. violaceus is capable of performing state transitions similar to evolutionarily more recent cyanobacteria, being in state 2 in darkness and in state 1 upon illumination by weak blue or far-red light. Compared with state 2, variable fluorescence yield in state 1 is strongly enhanced (almost 80%), while the functional absorption cross-section of PSII is only increased by 8%. In contrast to weak blue light, which enhances fluorescence yield via state 1 formation, strong blue light reversibly quenches Chl fluorescence in G. violaceus. This strongly suggests regulated heat dissipation which is triggered by the orange carotenoid protein whose presence was directly proven by immunoblotting and mass spectrometry in this primordial cyanobacterium. The results are discussed in the framework of cyanobacterial evolution.
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Affiliation(s)
- Gábor Bernát
- Plant Biochemistry, Ruhr-University Bochum, D-44801 Bochum, Germany.
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16
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Marchetti A, Schruth DM, Durkin CA, Parker MS, Kodner RB, Berthiaume CT, Morales R, Allen AE, Armbrust EV. Comparative metatranscriptomics identifies molecular bases for the physiological responses of phytoplankton to varying iron availability. Proc Natl Acad Sci U S A 2012; 109:E317-25. [PMID: 22308424 PMCID: PMC3277525 DOI: 10.1073/pnas.1118408109] [Citation(s) in RCA: 168] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
In vast expanses of the oceans, growth of large phytoplankton such as diatoms is limited by iron availability. Diatoms respond almost immediately to the delivery of iron and rapidly compose the majority of phytoplankton biomass. The molecular bases underlying the subsistence of diatoms in iron-poor waters and the plankton community dynamics that follow iron resupply remain largely unknown. Here we use comparative metatranscriptomics to identify changes in gene expression associated with iron-stimulated growth of diatoms and other eukaryotic plankton. A microcosm iron-enrichment experiment using mixed-layer waters from the northeastern Pacific Ocean resulted in increased proportions of diatom transcripts and reduced proportions of transcripts from most other taxa within 98 h after iron addition. Hundreds of diatom genes were differentially expressed in the iron-enriched community compared with the iron-limited community; transcripts of diatom genes required for synthesis of photosynthesis and chlorophyll components, nitrate assimilation and the urea cycle, and synthesis of carbohydrate storage compounds were significantly overrepresented. Transcripts of genes encoding rhodopsins in eukaryotic phytoplankton were significantly underrepresented following iron enrichment, suggesting rhodopsins help cells cope with low-iron conditions. Oceanic diatoms appear to display a distinctive transcriptional response to iron enrichment that allows chemical reduction of available nitrogen and carbon sources along with a continued dependence on iron-free photosynthetic proteins rather than substituting for iron-containing functional equivalents present within their gene repertoire. This ability of diatoms to divert their newly acquired iron toward nitrate assimilation may underlie why diatoms consistently dominate iron enrichments in high-nitrate, low-chlorophyll regions.
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Affiliation(s)
- Adrian Marchetti
- School of Oceanography, University of Washington, Seattle, WA 98105; and
| | - David M. Schruth
- School of Oceanography, University of Washington, Seattle, WA 98105; and
| | - Colleen A. Durkin
- School of Oceanography, University of Washington, Seattle, WA 98105; and
| | - Micaela S. Parker
- School of Oceanography, University of Washington, Seattle, WA 98105; and
| | - Robin B. Kodner
- School of Oceanography, University of Washington, Seattle, WA 98105; and
| | | | - Rhonda Morales
- School of Oceanography, University of Washington, Seattle, WA 98105; and
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O'Malley-James JT, Raven JA, Cockell CS, Greaves JS. Life and light: exotic photosynthesis in binary and multiple-star systems. ASTROBIOLOGY 2012; 12:115-124. [PMID: 22283409 DOI: 10.1089/ast.2011.0678] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The potential for Earth-like planets within binary/multiple-star systems to host photosynthetic life was evaluated by modeling the levels of photosynthetically active radiation (PAR) such planets receive. Combinations of M and G stars in (i) close-binary systems; (ii) wide-binary systems, and (iii) three-star systems were investigated, and a range of stable radiation environments were found to be possible. These environmental conditions allow for the possibility of familiar, but also more exotic, forms of photosynthetic life, such as IR photosynthesizers and organisms that are specialized for specific spectral niches.
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Affiliation(s)
- J T O'Malley-James
- School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, UK.
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18
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Abstract
Energy conversion of sunlight by photosynthetic organisms has changed Earth and life on it. Photosynthesis arose early in Earth's history, and the earliest forms of photosynthetic life were almost certainly anoxygenic (non-oxygen evolving). The invention of oxygenic photosynthesis and the subsequent rise of atmospheric oxygen approximately 2.4 billion years ago revolutionized the energetic and enzymatic fundamentals of life. The repercussions of this revolution are manifested in novel biosynthetic pathways of photosynthetic cofactors and the modification of electron carriers, pigments, and existing and alternative modes of photosynthetic carbon fixation. The evolutionary history of photosynthetic organisms is further complicated by lateral gene transfer that involved photosynthetic components as well as by endosymbiotic events. An expanding wealth of genetic information, together with biochemical, biophysical, and physiological data, reveals a mosaic of photosynthetic features. In combination, these data provide an increasingly robust framework to formulate and evaluate hypotheses concerning the origin and evolution of photosynthesis.
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19
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Raven JA. Inorganic carbon acquisition by eukaryotic algae: four current questions. PHOTOSYNTHESIS RESEARCH 2010; 106:123-34. [PMID: 20524069 DOI: 10.1007/s11120-010-9563-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2010] [Accepted: 05/17/2010] [Indexed: 05/18/2023]
Abstract
The phylogenetically and morphologically diverse eukaryotic algae are typically oxygenic photolithotrophs. They have a diversity of incompletely understood mechanisms of inorganic carbon acquisition: this article reviews four areas where investigations continue. The first topic is diffusive CO(2) entry. Most eukaryotic algae, like all cyanobacteria, have inorganic carbon concentrating mechanisms (CCMs). The ancestral condition was presumably the absence of a CCM, i.e. diffusive CO(2) entry, as found in a small minority of eukaryotic algae today; however, it is likely that, as is found in several cases, this condition is due to a loss of a CCM. There are a number of algae which are in various respects intermediate between diffusive CO(2) entry and occurrence of a CCM: further study is needed on this aspect. A second topic is the nature of cyanelles and their role in inorganic carbon assimilation. The cyanelles (plastids) of the euglyphid amoeba Paulinella have been acquired relatively recently by endosymbiosis with genetic integration of an α-cyanobacterium with a Form 1A Rubisco. The α-carboxysomes in the cyanelles are presumably involved in a CCM, but further investigation is needed.Also called cyanelles are the plastids of glaucocystophycean algae, but is it now clear that these were derived from the β-cyanobacterial ancestor of all plastids other than that of Paulinella. The resemblances of the central body of the cyanelles of glaucocystophycean algae to carboxysomes may not reflect derivation from cyanobacterial β-carboxysomes; although it is clear that these algae have CCMs but these are now well characterized. The other two topics concern CCMs in other eukaryotic algae; these CCMs arose polyphyletically and independently of the cyanobacterial CCMs. It is generally believed that eukaryotic algal, like cyanobacterial, CCMs are based on active transport of an inorganic carbon species and/or protons, and they have C(3) biochemistry. This is the case for the organism considered as the third topic, i.e. Chlamydomonas reinhardtii, the eukaryotic alga with the best understood CCM. This CCM involves HCO(3)(-) conversion to CO(2) in the thylakoid lumen so the external inorganic carbon must cross four membranes in series with a final CO(2) effux from the thylakoid. More remains to be investigated about this CCM. The final topic is that of the occurrence of C(4)-like metabolism in the CCMs of marine diatoms. Different conclusions have been reached depending on the organism investigated and the techniques used, and several aspects require further study.
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Affiliation(s)
- John A Raven
- Division of Plant Sciences, College of Life Sciences, University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK.
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20
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Marosvölgyi MA, van Gorkom HJ. Cost and color of photosynthesis. PHOTOSYNTHESIS RESEARCH 2010; 103:105-9. [PMID: 20063064 PMCID: PMC2807594 DOI: 10.1007/s11120-009-9522-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Accepted: 12/20/2009] [Indexed: 05/04/2023]
Abstract
The question of why plants are green has been revisited in several articles recently. A common theme in the discussions is to explain why photosynthesis appears to absorb less of the available green sunlight than expected. The expectation is incorrect, however, because it fails to take the energy cost of the photosynthetic apparatus into account. Depending on that cost, the red absorption band of the chlorophylls may be closely optimized to provide maximum growth power. The optimization predicts a strong influence of Fraunhofer lines in the solar irradiance on the spectral shape of the optimized absorption band, which appears to be correct. It does not predict any absorption at other wavelengths.
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