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Kobayashi T, Shimada Y, Nagao R, Noguchi T. pH-Dependent Regulation of Electron Flow in Photosystem II by a Histidine Residue at the Stromal Surface. Biochemistry 2022; 61:1351-1362. [PMID: 35686693 DOI: 10.1021/acs.biochem.2c00150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In photosystem II (PSII), the secondary plastoquinone electron acceptor QB functions as a substrate that converts into plastoquinol upon its double reduction by electrons abstracted from water. It has been suggested that a histidine residue, D1-H252, which is located at the stromal surface near QB, is involved in the pH-dependent regulation of electron flow and proton transfer to QB. However, definitive evidence for the involvement of D1-H252 in the QB reactions has not been obtained yet. Here, we studied the roles of D1-H252 in PSII using a cyanobacterial mutant, in which D1-H252 was replaced with Ala. Delayed luminescence (DL) measurement upon a single flash showed a faster QB- decay at higher pH in the thylakoids from the wild-type strain due to the downshift of the redox potential of QB [Em(QB-/QB)]. This pH dependence of the QB- decay was lost in the D1-H252A mutant. The experimental Em(QB-/QB) changes were well reproduced by the density functional theory calculations for models with different protonation states of D1-H252 and with Ala replaced for H252. It was further shown that the period-four oscillation of the DL intensity by successive flashes was significantly diminished in the D1-H252A mutant, suggesting the inhibition of plastoquinone exchange at the QB pocket in this mutant. It is thus concluded that D1-H252 is a key amino acid residue that regulates electron flow in PSII by sensing pH in the stroma and stabilizes the QB binding site to facilitate the quinone exchange reaction.
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Affiliation(s)
- Tomoyuki Kobayashi
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Yuichiro Shimada
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Ryo Nagao
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan.,Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Takumi Noguchi
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
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Coral symbioses under prolonged environmental change: living near tolerance range limits. Sci Rep 2016; 6:36271. [PMID: 27805069 PMCID: PMC5090243 DOI: 10.1038/srep36271] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 10/13/2016] [Indexed: 02/08/2023] Open
Abstract
As climate change progresses, understanding the long-term response of corals and their endosymbionts (Symbiodinium) to prolonged environmental change is of immediate importance. Here, a total of 1152 fragments from 72 colonies of three common coral species (Stylophora pistillata, Pocillopora damicornis, Seriatopora hystrix) underwent a 32-month reciprocal depth transplantation. Genetic analysis showed that while S. hystrix maintained its generalist symbiont, some S. pistillata and P. damicornis underwent temporary changes in resident symbionts immediately after stress (transplantation; natural bleaching). These temporary changes were phylogenetically constrained to ‘host-compatible’ symbionts only and reversion to original symbionts occurred within 7 to 12 months, indicating long-term fidelity and stability of adult symbioses. Measurements of symbiont photo-physiology (dark adapted yield, pressure over photosystem II) and coral health (host protein, bleaching status, mortality) indicated a broad acclimatory capacity. However, this came at an apparent energetic expense as disproportionate mortality amongst symbioses that persisted outside their distribution range was observed following a natural bleaching event. As environmental changes due to climate change become more continuous in nature, sub-lethal effects linked to the existence near tolerance range limits coupled with the inability of adult coral colonies to change resident symbionts makes corals particularly susceptible to additional environmental fluctuations or stress events and reduces the resilience of coral populations.
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Lambreva MD, Russo D, Polticelli F, Scognamiglio V, Antonacci A, Zobnina V, Campi G, Rea G. Structure/function/dynamics of photosystem II plastoquinone binding sites. Curr Protein Pept Sci 2015; 15:285-95. [PMID: 24678671 PMCID: PMC4030317 DOI: 10.2174/1389203715666140327104802] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 11/22/2013] [Accepted: 03/16/2014] [Indexed: 11/22/2022]
Abstract
Photosystem II (PSII)
continuously attracts the attention of researchers aiming to unravel the riddle
of its functioning and efficiency fundamental for all life on Earth. Besides, an
increasing number of biotechnological applications have been envisaged
exploiting and mimicking the unique properties of this macromolecular
pigment-protein complex. The PSII organization and working principles have
inspired the design of electrochemical water splitting schemes and charge
separating triads in energy storage systems as well as biochips and sensors for
environmental, agricultural and industrial screening of toxic compounds. An
intriguing opportunity is the development of sensor devices, exploiting native
or manipulated PSII complexes or ad hoc synthesized polypeptides
mimicking the PSII reaction centre proteins as bio-sensing elements. This review
offers a concise overview of the recent improvements in the understanding of
structure and function of PSII donor side, with focus on the interactions of the
plastoquinone cofactors with the surrounding environment and operational
features. Furthermore, studies focused on photosynthetic proteins
structure/function/dynamics and computational analyses aimed at rational design
of high-quality bio-recognition elements in biosensor devices are discussed.
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Affiliation(s)
| | | | | | | | | | | | | | - Giuseppina Rea
- Institute of Crystallography, National Research Council, Monterotondo, Italy.
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Finazzi G, Minagawa J. High Light Acclimation in Green Microalgae. ADVANCES IN PHOTOSYNTHESIS AND RESPIRATION 2014. [DOI: 10.1007/978-94-017-9032-1_21] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Tu W, Li Y, Zhang Y, Zhang L, Liu H, Liu C, Yang C. Diminished photoinhibition is involved in high photosynthetic capacities in spring ephemeral Berteroa incana under strong light conditions. JOURNAL OF PLANT PHYSIOLOGY 2012; 169:1463-70. [PMID: 22854181 DOI: 10.1016/j.jplph.2012.05.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2012] [Revised: 05/22/2012] [Accepted: 05/22/2012] [Indexed: 05/15/2023]
Abstract
Berteroa incana (B. incana), a spring ephemeral species of Brassicaceae, possesses very high photosynthetic capacities at high irradiances. Exploring the mechanism of the high light use efficiency of B. incana under strong light conditions may help to explore mechanisms of plants' survival strategies. Therefore, the photosynthetic characteristics of B. incana grown under three different light intensities (field conditions (field): 200-1500μmolphotonsm(-2)s(-1); greenhouse high light (HL) conditons: 600μmolphotonsm(-2)s(-1); and greenhouse low light (LL) conditions: 100μmolphotonsm(-2)s(-1)) were investigated and compared with those of the model plant Arabidopsis thaliana (A. thaliana). Our results revealed that B. incana behaved differently in adjusting its photosynthetic activities under both HL and LL conditions compared with what A. thaliana did under the same conditions, suggesting that the potential of photosynthetic capacity of B. incana might be enhanced under strong light conditions. Under LL conditions, B. incana reached its maximum photosynthetic activity at a much higher light intensity than A. thaliana did, although their maximum photochemical efficiency of photosystem II (PSII) (F(v)/F(m)) was almost the same. When grown under HL conditions, B. incana showed much higher photosynthetic capacity than A. thaliana. A detailed analysis of the OJIP transient kinetics of B. incana under HL and LL conditions revealed that HL-grown B. incana possessed not only a high ability in regulating photosystem stoichiometry that ensured high linear electron transport, but also an enhanced availability of oxidized plastoquinone (PQ) pool which reduced non-photochemical quenching (NPQ), especially its slow components qT and qI, and increased the photochemical efficiency, which in turn, increased the electron transport. We suggest that the high ability in regulating photosystem stoichiometry and the high level of the availability of oxidized PQ pool in B. incana under strong light conditions play important roles in its ability to retain higher photosynthetic capacity under extreme environmental conditions.
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Affiliation(s)
- Wenfeng Tu
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
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Middlebrook R, Anthony KRN, Hoegh-Guldberg O, Dove S. Heating rate and symbiont productivity are key factors determining thermal stress in the reef-building coral Acropora formosa. J Exp Biol 2010; 213:1026-34. [DOI: 10.1242/jeb.031633] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
SUMMARY
The onset of large-scale coral bleaching events is routinely estimated on the basis of the duration and intensity of thermal anomalies determined as degree heating weeks. Degree heating weeks, however, do not account for differential rates of heating. This study aimed to explore the relationship between different rates of heating above the documented regional winter threshold, and resultant bleaching of the reef-building coral Acropora formosa. Under a relatively low light field, rapid heating of 1°C day−1 from 29°C to 32°C lead to a 17.6% decline in Fv/Fm, concurrent with a rapid increase in xanthophyll de-epoxidation sustained into the dark, whereas slower heating rates of 0.5°C day−1 lead to no decline in Fv/Fm and no change in dark-adapted xanthophyll cycling. At the winter bleaching threshold of 30°C, areal net O2 evolution exceeded the control values for rapidly heated corals, but was lower than the controls for slowly heated corals. At the maximum temperature of 33°C, however, both treatments had net O2 fluxes that were 50% of control values. At 30°C, only symbiont densities in the slowly heated controls were reduced relative to controls values. By 33°C, however, symbiont densities were 55% less than the controls in both treatments. The rate of heat accumulation was found to be an important variable, with rapidly heated corals attaining the same bleaching status and loss of areal O2 production for half the degree heating week exposure as slowly heated corals. The study revealed that it is incorrect to assume that significant dark acclimation disables non-photochemical quenching, because 75% of an increased xanthophyll pool was found to be in the de-epoxidated state following rapid heat accumulation. This has important ramifications for the interpretation of chlorophyll fluorescence data such as dark adapted Fv/Fm.
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Affiliation(s)
- Rachael Middlebrook
- ARC Centre of Excellence for Coral Reef Studies, Centre for Marine Studies, University of Queensland, St Lucia, QLD 4072, Australia
| | - Kenneth R. N. Anthony
- ARC Centre of Excellence for Coral Reef Studies, Centre for Marine Studies, University of Queensland, St Lucia, QLD 4072, Australia
| | - Ove Hoegh-Guldberg
- ARC Centre of Excellence for Coral Reef Studies, Centre for Marine Studies, University of Queensland, St Lucia, QLD 4072, Australia
| | - Sophie Dove
- ARC Centre of Excellence for Coral Reef Studies, Centre for Marine Studies, University of Queensland, St Lucia, QLD 4072, Australia
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Ocean acidification causes bleaching and productivity loss in coral reef builders. Proc Natl Acad Sci U S A 2008; 105:17442-6. [PMID: 18988740 DOI: 10.1073/pnas.0804478105] [Citation(s) in RCA: 415] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Ocean acidification represents a key threat to coral reefs by reducing the calcification rate of framework builders. In addition, acidification is likely to affect the relationship between corals and their symbiotic dinoflagellates and the productivity of this association. However, little is known about how acidification impacts on the physiology of reef builders and how acidification interacts with warming. Here, we report on an 8-week study that compared bleaching, productivity, and calcification responses of crustose coralline algae (CCA) and branching (Acropora) and massive (Porites) coral species in response to acidification and warming. Using a 30-tank experimental system, we manipulated CO(2) levels to simulate doubling and three- to fourfold increases [Intergovernmental Panel on Climate Change (IPCC) projection categories IV and VI] relative to present-day levels under cool and warm scenarios. Results indicated that high CO(2) is a bleaching agent for corals and CCA under high irradiance, acting synergistically with warming to lower thermal bleaching thresholds. We propose that CO(2) induces bleaching via its impact on photoprotective mechanisms of the photosystems. Overall, acidification impacted more strongly on bleaching and productivity than on calcification. Interestingly, the intermediate, warm CO(2) scenario led to a 30% increase in productivity in Acropora, whereas high CO(2) lead to zero productivity in both corals. CCA were most sensitive to acidification, with high CO(2) leading to negative productivity and high rates of net dissolution. Our findings suggest that sensitive reef-building species such as CCA may be pushed beyond their thresholds for growth and survival within the next few decades whereas corals will show delayed and mixed responses.
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Dove SG, Lovell C, Fine M, Deckenback J, Hoegh-Guldberg O, Iglesias-Prieto R, Anthony KRN. Host pigments: potential facilitators of photosynthesis in coral symbioses. PLANT, CELL & ENVIRONMENT 2008; 31:1523-1533. [PMID: 18643952 DOI: 10.1111/j.1365-3040.2008.01852.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Reef-building corals occur as a range of colour morphs because of varying types and concentrations of pigments within the host tissues, but little is known about their physiological or ecological significance. Here, we examined whether specific host pigments act as an alternative mechanism for photoacclimation in the coral holobiont. We used the coral Montipora monasteriata (Forskål 1775) as a case study because it occurs in multiple colour morphs (tan, blue, brown, green and red) within varying light-habitat distributions. We demonstrated that two of the non-fluorescent host pigments are responsive to changes in external irradiance, with some host pigments up-regulating in response to elevated irradiance. This appeared to facilitate the retention of antennal chlorophyll by endosymbionts and hence, photosynthetic capacity. Specifically, net P(max) Chl a(-1) correlated strongly with the concentration of an orange-absorbing non-fluorescent pigment (CP-580). This had major implications for the energetics of bleached blue-pigmented (CP-580) colonies that maintained net P(max) cm(-2) by increasing P(max) Chl a(-1). The data suggested that blue morphs can bleach, decreasing their symbiont populations by an order of magnitude without compromising symbiont or coral health.
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Affiliation(s)
- Sophie G Dove
- Centre for Marine Studies, Australian Research Council Centre of Excellence for Coral Reef Studies, University of Queensland, St Lucia, Queensland, Australia.
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Ivanov AG, Sane PV, Hurry V, Oquist G, Huner NPA. Photosystem II reaction centre quenching: mechanisms and physiological role. PHOTOSYNTHESIS RESEARCH 2008; 98:565-74. [PMID: 18821028 DOI: 10.1007/s11120-008-9365-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2008] [Accepted: 09/01/2008] [Indexed: 05/03/2023]
Abstract
Dissipation of excess absorbed light energy in eukaryotic photoautotrophs through zeaxanthin- and DeltapH-dependent photosystem II antenna quenching is considered the major mechanism for non-photochemical quenching and photoprotection. However, there is mounting evidence of a zeaxanthin-independent pathway for dissipation of excess light energy based within the PSII reaction centre that may also play a significant role in photoprotection. We summarize recent reports which indicate that this enigma can be explained, in part, by the fact that PSII reaction centres can be reversibly interconverted from photochemical energy transducers that convert light into ATP and NADPH to efficient, non-photochemical energy quenchers that protect the photosynthetic apparatus from photodamage. In our opinion, reaction centre quenching complements photoprotection through antenna quenching, and dynamic regulation of photosystem II reaction centre represents a general response to any environmental condition that predisposes the accumulation of reduced Q(A) in the photosystem II reaction centres of prokaryotic and eukaryotic photoautotrophs. Since the evolution of reaction centres preceded the evolution of light harvesting systems, reaction centre quenching may represent the oldest photoprotective mechanism.
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Affiliation(s)
- Alexander G Ivanov
- Department of Biology and The Biotron, University of Western Ontario, London, ON, Canada
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