Effect of ultraviolet-B radiation on intact cells of the cyanobacterium Spirulina platensis: characterization of the alterations in the thylakoid membranes

Subramanyam, Rajagopal; Murthy, S. D. S.; Mohanty, Prasanna

doi:10.1016/s1011-1344(99)00156-6

Cited by 44 publications

(26 citation statements)

References 20 publications

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“…However, studies have shown that the DNA molecule is indeed degraded in cyanobacteria (6,34) and that the physiology of these organisms responds negatively when they are exposed to elevated levels of UV-B (44). In particular, it has been shown that UV-B affects the photosynthetic electron transport and pigment-protein complexes of A. platensis (38). However, it is also now known that aquatic organisms have mechanisms to minimize and counteract the deleterious effects produced by highly energetic short wavelengths (1,32).…”

Section: Discussionmentioning

confidence: 99%

Effects of Solar UV Radiation on Morphology and Photosynthesis of Filamentous Cyanobacterium Arthrospira platensis

Gao

Villafañe

et al. 2005

Appl Environ Microbiol

154

125

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To study the impact of solar UV radiation (UVR) (280 to 400 nm) on the filamentous cyanobacterium Arthrospira (Spirulina) platensis, we examined the morphological changes and photosynthetic performance using an indoor-grown strain (which had not been exposed to sunlight for decades) and an outdoor-grown strain (which had been grown under sunlight for decades) while they were cultured with three solar radiation treatments: PAB (photosynthetically active radiation [PAR] plus UVR; 280 to 700 nm), PA (PAR plus UV-A; 320 to 700 nm), and P (PAR only; 400 to 700 nm). Solar UVR broke the spiral filaments of A. platensis exposed to full solar radiation in short-term low-cell-density cultures. This breakage was observed after 2 h for the indoor strain but after 4 to 6 h for the outdoor strain. Filament breakage also occurred in the cultures exposed to PAR alone; however, the extent of breakage was less than that observed for filaments exposed to full solar radiation. The spiral filaments broke and compressed when high-cell-density cultures were exposed to full solar radiation during long-term experiments. When UV-B was screened off, the filaments initially broke, but they elongated and became loosely arranged later (i.e., there were fewer spirals per unit of filament length). When UVR was filtered out, the spiral structure hardly broke or became looser. Photosynthetic O 2 evolution in the presence of UVR was significantly suppressed in the indoor strain compared to the outdoor strain. UVRinduced inhibition increased with exposure time, and it was significantly lower in the outdoor strain. The concentration of UV-absorbing compounds was low in both strains, and there was no significant change in the amount regardless of the radiation treatment, suggesting that these compounds were not effectively used as protection against solar UVR. Self-shading, on the other hand, produced by compression of the spirals over adaptive time scales, seems to play an important role in protecting this species against deleterious UVR. Our findings suggest that the increase in UV-B irradiance due to ozone depletion not only might affect photosynthesis but also might alter the morphological development of filamentous cyanobacteria during acclimation or over adaptive time scales.

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Section: Discussionmentioning

confidence: 99%

Effects of Solar UV Radiation on Morphology and Photosynthesis of Filamentous Cyanobacterium Arthrospira platensis

Gao

Villafañe

et al. 2005

Appl Environ Microbiol

154

125

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“…5A) or was irradiated with visible light (B) or UV-B light (C) for 30 min. The intensity of each peak was measured in the three samples deriving from the same preparation and expressed as a percentage of the intensity of the CP43 peak (m/z 51,470), which is known to be unaffected by the light intensities used here (30). Whereas the relative intensities of most of the peaks did not change upon exposure to radiation, those corresponding to D1 and D2 (m/z 38,048 and 39,268, respectively) showed marked variations.…”

Section: Maldi Spectrum Of High Mw Subunits Of Psii Core Complex In Lmentioning

confidence: 99%

Determination of Photosystem II Subunits by Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

Szabó

Seraglia²,

Rigoni

et al. 2001

Journal of Biological Chemistry

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Photosystem II of higher plants and cyanobacteria is composed of more than 20 polypeptide subunits. The pronounced hydrophobicity of these proteins hinders their purification and subsequent analysis by mass spectrometry. This paper reports the results obtained by application of matrix-assisted laser desorption/ionization mass spectrometry directly to isolated complexes and thylakoid membranes prepared from cyanobacteria and spinach. Changes in protein contents following physiopathological stimuli are also described. Good correlations between expected and measured molecular masses allowed the identification of the main, as well as most of the minor, low molecular weight components of photosystem II. These results open up new perspectives for clarifying the functional role of the various polypeptide components of photosystems and other supramolecular integral membrane complexes.Photosystem II is a pigment-protein complex of the thylakoid membrane of higher plants, eukaryotic algae, and cyanobacteria. It catalyzes light-induced electron transfer from water to plastoquinone, with associated production of molecular oxygen. PSII 1 consists of a large complex with a number of polypeptide components, most of which are integral membrane proteins. A number of extrinsic proteins are also associated with it at the membrane surface. The entire set of electron transfer cofactors, including chlorophyll a, pheophytin a, plastoquinones, and non-heme iron, is associated with the D1/D2 heterodimer. These two proteins, together with the ␣ and ␤ subunits of cytochrome b 559 and the PsbI protein, constitute the so-called reaction center II (RCII), which is the smallest PSII subparticle still able to perform light-induced charge separation (1). Two large integral membrane proteins, CP43 and CP47, each coordinating a number (12-15) of chlorophyll a molecules, and several low molecular mass (Ͻ10 kDa) polypeptides are constituents of the PSII core complex, which is very similar in higher plants and prokaryotic cyanobacteria.During the last decade, considerable progress has been made in our understanding of the organization of polypeptides constituting the reaction center of PSII, but the topology and functional role of the small protein subunits are still largely unknown. Some of them are universal, whereas others are present only in cyanobacteria (PsbU and PsbV) or only in higher plants (e.g. PsbP, PsbQ, PsbS) (2).Investigation of the structural and functional roles of the various PSII subunits requires, as a preliminary step, a suitable method to detect them in the thylakoid membrane or purified subparticle preparations. The detection and study of stimuli-induced modifications of several PSII components have mainly been based on the use of polyclonal antibodies. However, these are often not available and, when available, are time-consuming to use.A different technique, capable of accurately detecting even small amounts of the various PSII subunits in an integrated system, could be of great help in studying the function of these protein...

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“…Passive defense mechanisms (such as the accumulation of UV-screening compounds) are known to play important roles in protecting cyanobacteria from photodamage (Garcia-Pichel and Castenholz 1991;Rozema 2002). However, in A. platensis, the amount of UV-absorbing compounds is very low, and will not effectively protect the cells from harmful levels of UVR (Rajagopal 2000;Gupta et al 2008;Gao and Ma 2008). Wu et al (2005a) suggest that the self-shading provided by the compressed spirals provides photoprotection against harmful radiation.…”

Section: Discussionmentioning

confidence: 99%

Photoregulation of morphological structure and its physiological relevance in the cyanobacterium Arthrospira (Spirulina) platensis

Gao

2009

Planta

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The spiral structure of the cyanobacterium Arthrospira (Spirulina) platensis (Nordst.) Gomont was previously found to be altered by solar ultraviolet radiation (UVR, 280-400 nm). However, how photosynthetic active radiation (PAR, 400-700 nm) and UVR interact in regulating this morphological change remains unknown. Here, we show that the spiral structure of A. platensis (D-0083) was compressed under PAR alone at 30 degrees C, but that at 20 degrees C, the spirals compressed only when exposed to PAR with added UVR, and that UVR alone (the PAR was filtered out) did not tighten the spiral structure, although its presence accelerated morphological regulation by PAR. Their helix pitch decreased linearly as the cells received increased PAR doses, and was reversible when they were transferred back to low PAR levels. SDS-PAGE analysis showed that a 52.0 kDa periplasmic protein was more abundant in tighter filaments, which may have been responsible for the spiral compression. This spiral change together with the increased abundance of the protein made the cells more resistant to high PAR as well as UVR, resulting in a higher photochemical yield.

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Effect of ultraviolet-B radiation on intact cells of the cyanobacterium Spirulina platensis: characterization of the alterations in the thylakoid membranes

Cited by 44 publications

References 20 publications

Effects of Solar UV Radiation on Morphology and Photosynthesis of Filamentous Cyanobacterium Arthrospira platensis

Effects of Solar UV Radiation on Morphology and Photosynthesis of Filamentous Cyanobacterium Arthrospira platensis

Determination of Photosystem II Subunits by Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

Photoregulation of morphological structure and its physiological relevance in the cyanobacterium Arthrospira (Spirulina) platensis

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