Plant Physiol. Journal of Pharmacology and Experimental Therapeutics
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Plant Physiology 95:492-497 (1991)
© 1991 American Society of Plant Biologists

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Environmental and Stress Physiology

Effect of Light Quality on Phycobilisome Components of the Cyanobacterium Spirulina platensis

T. Sudhakar Babu, Ashok Kumar1 and Ajit K. Varma

School of Life Sciences, Jawaharlal Nehru University, New Delhi-110 067, India

Phycobilisomes from the nonchromatic adapting cyanobacterium Spirulina platensis are composed of a central core containing allophycocyanin and rods with phycocyanin and linker polypeptides in a regular array. Room temperature absorption spectra of phycobilisomes from this organism indicated the presence of phycocyanin and allophycocyanin. However, low temperature absorption spectra showed the association of a phycobiliviolin type of chromophore within phycobilisomes. This chromophore had an absorption maximum at 590 nanometers when phycobilisomes were suspended in 0.75 molar K-phosphate buffer (pH 7.0). Purified phycocyanin from this cyanobacterium was found to consist of three subparticles and the phycobiliviolin type of chromophore was associated with the lowest density subparticle. Circular dichroism spectra of phycocyanin subparticles also indicated the association of this chromophore with the lowest density subparticle. Absorption spectral analysis of {alpha} and {beta} subunits of phycocyanin showed that phycobiliviolin type of chromophore was attached to the {alpha} subunit, but not the {beta} subunit. Effect of light quality showed that green light enhanced the synthesis of this chromophore as analyzed from the room temperature absorption spectra of phycocyanin subparticles and subunits, while red or white light did not have any effect. Low temperature absorption spectra of phycobilisomes isolated from green, red, and white light conditions also indicated the enhancement of phycobiliviolin type of chromophore under green light.

1 Present address: Department of Molecular Biology, University of Edinburgh, Kings Building, Mayfield Road, Edinburgh EH9 3JR, Scotland, UK.






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ASPB Publications PLANT PHYSIOLOGY THE PLANT CELL
Copyright © 1991 by the American Society of Plant Biologists