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

S. Rajagopal, S. D S Murthy, P. Mohanty

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Abstract

Intact trichomes of Spirulina platensis are exposed to ultraviolet-B (UV-B) radiation (270-320 nm; 1.9 mW m-2) for 9 h. This UV-B exposure results in alterations in the pigment-protein complexes and in the fluorescence emission profile of the chlorophyll-protein complexes of the thylakoids as compared with thylakoids isolated from control dark-adapted Spirulina cells. The UV-B exposure causes a significant decrease in photosystem II activity, but no loss in photosystem I activity. Although there is no change in the photosystem I activity in thylakoids from UV-B-exposed cells, the chlorophyll a emission at room temperature and at 77 K indicates alterations associated with photosystem I. Additionally, the results clearly demonstrate that the photosystem II core antennae of chlorophyll proteins CP47 and CP43 are affected by UV-B exposure, as revealed by Western blot analysis. Furthermore, a prominent 94 kDa protein band appears in the sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) profile of UV-B-exposed cell thylakoids, which is absent from the control thylakoids. This 94 kDa protein appears not to be newly induced by UV-B exposure, but could possibly have originated from the UV-B-induced cross-linking of the thylakoid proteins. The exposure of isolated Spirulina thylakoids to the same intensity of UV-B radiation for 1-3 h induces losses in the CP47 and CP43 levels, but does not induce the appearance of the 94 kDa protein band in SDS-PAGE. These results clearly demonstrate that prolonged exposure of Spirulina cells to moderate levels of UV-B affects the chlorophyll a-protein complexes and alters the fluorescence emission spectral profile of the pigment-protein complexes of the thylakoid membranes. Thus, it is clear that chlorophyll a antennae of Spirulina platensis are significantly altered by UV-B radiation. (C) 2000 Elsevier Science S.A. All rights reserved.

Original languageEnglish
Pages (from-to)61-66
Number of pages6
JournalJournal of Photochemistry and Photobiology, B: Biology
Volume54
Issue number1
DOIs
Publication statusPublished - Jan 30 2000

Fingerprint

Spirulina
Spirulina platensis
Thylakoids
Cyanobacteria
thylakoids
ultraviolet radiation
Radiation
membranes
proteins
Proteins
Membranes
Chlorophyll Binding Proteins
chlorophylls
Chlorophyll
Photosystem I Protein Complex
radiation
cells
Photosystem II Protein Complex
photosystem I
Electrophoresis

Keywords

  • Chlorophyll a-protein complexes
  • CP43
  • CP47
  • Fluorescence emission spectra
  • Photosystems
  • Spirulina platensis
  • UV-B radiation

ASJC Scopus subject areas

  • Plant Science
  • Bioengineering
  • Physical and Theoretical Chemistry

Cite this

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title = "Effect of ultraviolet-B radiation on intact cells of the cyanobacterium Spirulina platensis: Characterization of the alterations in the thylakoid membranes",
abstract = "Intact trichomes of Spirulina platensis are exposed to ultraviolet-B (UV-B) radiation (270-320 nm; 1.9 mW m-2) for 9 h. This UV-B exposure results in alterations in the pigment-protein complexes and in the fluorescence emission profile of the chlorophyll-protein complexes of the thylakoids as compared with thylakoids isolated from control dark-adapted Spirulina cells. The UV-B exposure causes a significant decrease in photosystem II activity, but no loss in photosystem I activity. Although there is no change in the photosystem I activity in thylakoids from UV-B-exposed cells, the chlorophyll a emission at room temperature and at 77 K indicates alterations associated with photosystem I. Additionally, the results clearly demonstrate that the photosystem II core antennae of chlorophyll proteins CP47 and CP43 are affected by UV-B exposure, as revealed by Western blot analysis. Furthermore, a prominent 94 kDa protein band appears in the sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) profile of UV-B-exposed cell thylakoids, which is absent from the control thylakoids. This 94 kDa protein appears not to be newly induced by UV-B exposure, but could possibly have originated from the UV-B-induced cross-linking of the thylakoid proteins. The exposure of isolated Spirulina thylakoids to the same intensity of UV-B radiation for 1-3 h induces losses in the CP47 and CP43 levels, but does not induce the appearance of the 94 kDa protein band in SDS-PAGE. These results clearly demonstrate that prolonged exposure of Spirulina cells to moderate levels of UV-B affects the chlorophyll a-protein complexes and alters the fluorescence emission spectral profile of the pigment-protein complexes of the thylakoid membranes. Thus, it is clear that chlorophyll a antennae of Spirulina platensis are significantly altered by UV-B radiation. (C) 2000 Elsevier Science S.A. All rights reserved.",
keywords = "Chlorophyll a-protein complexes, CP43, CP47, Fluorescence emission spectra, Photosystems, Spirulina platensis, UV-B radiation",
author = "S. Rajagopal and Murthy, {S. D S} and P. Mohanty",
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T1 - Effect of ultraviolet-B radiation on intact cells of the cyanobacterium Spirulina platensis

T2 - Characterization of the alterations in the thylakoid membranes

AU - Rajagopal, S.

AU - Murthy, S. D S

AU - Mohanty, P.

PY - 2000/1/30

Y1 - 2000/1/30

N2 - Intact trichomes of Spirulina platensis are exposed to ultraviolet-B (UV-B) radiation (270-320 nm; 1.9 mW m-2) for 9 h. This UV-B exposure results in alterations in the pigment-protein complexes and in the fluorescence emission profile of the chlorophyll-protein complexes of the thylakoids as compared with thylakoids isolated from control dark-adapted Spirulina cells. The UV-B exposure causes a significant decrease in photosystem II activity, but no loss in photosystem I activity. Although there is no change in the photosystem I activity in thylakoids from UV-B-exposed cells, the chlorophyll a emission at room temperature and at 77 K indicates alterations associated with photosystem I. Additionally, the results clearly demonstrate that the photosystem II core antennae of chlorophyll proteins CP47 and CP43 are affected by UV-B exposure, as revealed by Western blot analysis. Furthermore, a prominent 94 kDa protein band appears in the sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) profile of UV-B-exposed cell thylakoids, which is absent from the control thylakoids. This 94 kDa protein appears not to be newly induced by UV-B exposure, but could possibly have originated from the UV-B-induced cross-linking of the thylakoid proteins. The exposure of isolated Spirulina thylakoids to the same intensity of UV-B radiation for 1-3 h induces losses in the CP47 and CP43 levels, but does not induce the appearance of the 94 kDa protein band in SDS-PAGE. These results clearly demonstrate that prolonged exposure of Spirulina cells to moderate levels of UV-B affects the chlorophyll a-protein complexes and alters the fluorescence emission spectral profile of the pigment-protein complexes of the thylakoid membranes. Thus, it is clear that chlorophyll a antennae of Spirulina platensis are significantly altered by UV-B radiation. (C) 2000 Elsevier Science S.A. All rights reserved.

AB - Intact trichomes of Spirulina platensis are exposed to ultraviolet-B (UV-B) radiation (270-320 nm; 1.9 mW m-2) for 9 h. This UV-B exposure results in alterations in the pigment-protein complexes and in the fluorescence emission profile of the chlorophyll-protein complexes of the thylakoids as compared with thylakoids isolated from control dark-adapted Spirulina cells. The UV-B exposure causes a significant decrease in photosystem II activity, but no loss in photosystem I activity. Although there is no change in the photosystem I activity in thylakoids from UV-B-exposed cells, the chlorophyll a emission at room temperature and at 77 K indicates alterations associated with photosystem I. Additionally, the results clearly demonstrate that the photosystem II core antennae of chlorophyll proteins CP47 and CP43 are affected by UV-B exposure, as revealed by Western blot analysis. Furthermore, a prominent 94 kDa protein band appears in the sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) profile of UV-B-exposed cell thylakoids, which is absent from the control thylakoids. This 94 kDa protein appears not to be newly induced by UV-B exposure, but could possibly have originated from the UV-B-induced cross-linking of the thylakoid proteins. The exposure of isolated Spirulina thylakoids to the same intensity of UV-B radiation for 1-3 h induces losses in the CP47 and CP43 levels, but does not induce the appearance of the 94 kDa protein band in SDS-PAGE. These results clearly demonstrate that prolonged exposure of Spirulina cells to moderate levels of UV-B affects the chlorophyll a-protein complexes and alters the fluorescence emission spectral profile of the pigment-protein complexes of the thylakoid membranes. Thus, it is clear that chlorophyll a antennae of Spirulina platensis are significantly altered by UV-B radiation. (C) 2000 Elsevier Science S.A. All rights reserved.

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