| 1. |
- Huner, Norman P A, et al.
(author)
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Photoprotection of Photosystem II: Reaction center quenching versus antenna quenching
- 2006
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In: Photoprotection, Photoinhibition, Gene Regulation and Environment. - : Springer. - 9781402035647 ; , s. 155-174
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Book chapter (other academic/artistic)abstract
- Photoprotection, Photoinhibition, Gene Regulation, and Environment examines the processes whereby plants monitor environmental conditions and orchestrate their response to change, an ability paramount to the life of all plants. "Excess light", absorbed by the light-harvesting systems of photosynthetic organisms, is an integrative indicator of the environment, communicating the presence of intense light and any conditions unfavorable for growth and photosynthesis. Key plant responses are photoprotection and photoinhibition. In this volume, the dual role of photoprotective responses in the preservation of leaf integrity and in redox signaling networks modulating stress acclimation, growth, and development is addressed. In addition, the still unresolved impact of photoinhibition on plant survival and productivity is discussed. Specific topics include dissipation of excess energy via thermal and other pathways, scavenging of reactive oxygen by antioxidants, proteins key to photoprotection and photoinhibition, peroxidation of lipids, as well as signaling by reactive oxygen, lipid-derived messengers, and other messengers that modulate gene expression. Approaches include biochemical, physiological, genetic, molecular, and field studies, addressing intense visible and ultraviolet light, winter conditions, nutrient deficiency, drought, and salinity. This book is directed toward advanced undergraduate students, graduate students, and researchers interested in Plant Ecology, Stress Physiology, Plant Biochemistry, Integrative Biology, and Photobiology.
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| 2. |
- Ivanov, Alexander G, et al.
(author)
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Acclimation to temperature and irradiance modulates PSII charge recombination.
- 2006
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In: FEBS Letters. - : Wiley. - 0014-5793. ; 580:11, s. 2797-802
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Journal article (peer-reviewed)abstract
- Acclimation of wild type and the chlorina F2 mutant of barley to either high light or low temperature results in a 2- to 3-fold increase in non-photochemical quenching which occurred independently of either energy-dependent quenching (qE), xanthophyll cycle-mediated antenna quenching or state transitions. Results of in vivo thermoluminescence measurements used to address this conundrum indicated that excitation pressure regulates the temperature gap for Click to view the MathML source and Click to view the MathML source charge recombinations within photosystem II reaction centers. This is discussed in terms of photoprotection through non-radiative charge recombination.
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| 3. |
- Ivanov, Alexander G, et al.
(author)
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Reaction centre quenching of excess light energy and photoprotection of photosystem II
- 2008
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In: Journal of Plant Biology. ; 51:2, s. 85-96
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Journal article (peer-reviewed)abstract
- In addition to the energy dissipation of excess light occurring in PSII antenna via the xanthophyll cycle, there is mounting evidence of a zeaxanthin-independent pathway for non-photochemical quenching based within the PSII reaction centre (reaction centre quenching) that may also play a significant role in photoprotection. It has been demonstrated that acclimation of higher plants, green algae and cyanobacteria to low temperature or high light conditions which potentially induce an imbalance between energy supply and energy utilization is accompanied by the development of higher reduction state of QA and higher resistance to photoinhibition (Huner et al., 1998). Although this is a fundamental feature of all photoautotrophs, and the acquisition of increased tolerance to photoinhibition has been ascribed to growth and development under high PSII excitation pressure, the precise mechanism controlling the redox state of QA and its physiological significance in developing higher resistance to photoinhibition has not been fully elucidated. In this review we summarize recent data indicating that the increased resistance to high light in a broad spectrum of photosynthetic organisms acclimated to high excitation pressure conditions is associated with an increase probability for alternative non-radiative P680+QA − radical pair recombination pathway for energy dissipation within the reaction centre of PSII. The various molecular mechanisms that could account for nonphotochemical quenching through PSII reaction centre are also discussed.
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| 4. |
- Ivanov, Alexander G, et al.
(author)
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The induction of CP43' by iron-stress in Synechococcus sp. PCC 7942 is associated with carotenoid accumulation and enhanced fatty acid unsaturation.
- 2007
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In: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002 .- 0005-2728. ; 1767:6, s. 807-13
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Journal article (peer-reviewed)abstract
- Comparative lipid analysis demonstrated reduced amount of PG (50%) and lower ratio of MGDG/DGDG in iron-stressed Synechococcus sp. PCC 7942 cells compared to cells grown under iron sufficient conditions. In parallel, the monoenoic (C:1) fatty acids in MGDG, DGDG and PG increased from 46.8%, 43.7% and 45.6%, respectively in control cells to 51.6%, 48.8% and 48.7%, respectively in iron-stressed cells. This suggests increased membrane dynamics, which may facilitate the diffusion of PQ and keep the PQ pool in relatively more oxidized state in iron-stressed compared to control cells. This was confirmed by chlorophyll fluorescence and thermoluminescence measurements. Analysis of carotenoid composition demonstrated that the induction of isiA (CP43′) protein in response to iron stress is accompanied by significant increase of the relative abundance of all carotenoids. The quantity of carotenoids calculated on a Chl basis increased differentially with nostoxanthin, cryptoxanthin, zeaxanthin and β-carotene showing 2.6-, 3.1-, 1.9- and 1.9-fold increases, respectively, while the relative amount of caloxanthin was increased only by 30%. HPLC analyses of the pigment composition of Chl–protein complexes separated by non-denaturating SDS-PAGE demonstrated even higher relative carotenoids content, especially of cryptoxanthin, in trimer and monomer PSI Chl–protein complexes co-migrating with CP43′ from iron-stressed cells than in PSI complexes from control cells where CP43′ is not present. This implies a carotenoid-binding role for the CP43′ protein which supports our previous suggestion for effective energy quenching and photoprotective role of CP43′ protein in cyanobacteria under iron stress.
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| 5. |
- Sane, Prafullachandra Vishnu, et al.
(author)
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Thermoluminescence
- 2012
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In: Photosynthesis. - Dordrecht : Springer Netherlands. - 9789400715783 - 9789400715790 ; , s. 445-474
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Book chapter (peer-reviewed)abstract
- Thermo luminescence (TL) of photosynthetic membranes was discovered by William Arnold and Helen Sherwood in 1957. In the last half century, several studies have elucidated the mechanism of TL emission, which showed that the recombination of different charge pairs generated and trapped during pre-illumination are responsible for the observed light emission. Since most of the TL bands originate within Photosystem II (PS II), the technique of TL has become a useful complementary tool to chlorophyll a fluorescence to probe subtle changes in PS II photochemistry. The technique is simple and non-invasive; it has been successfully used to study leaf, cells, thylakoids and even reaction center preparations. The TL technique provides quick information about the redox potential changes of the bound primary quinone (Q(A)) and the secondary quinone (Q(B)) acceptors of PS II; TL has been extensively used to study the effects of photoinhibition, mutations, stresses and myriad responses of the photosynthetic apparatus during acclimation and adaptation. This chapter reviews crucial evidence for the identification of charge pairs responsible for the generation of different TL bands; the relationship of these bands to the components of delayed light emission; responses to excitation pressure arising out of environmental factors; methodology, and instrumentation. A model based on the detailed analysis of the redox shifts of the PS II electron acceptors Q(A) and Q(B), explaining the possibility of non-radiative dissipation of excess light energy within the reaction center of PS II (reaction center quenching) and its physiological significance in photoprotection of the photosynthetic membranes has been suggested. Developments in the analysis of biophysical parameters and the non-adherence of photosynthetic TL to the analysis by the 1945 theory of J.T. Randall and M.H.F. Wilkins have been briefly reviewed.
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