Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
Volume 1777, Issue 10, Pages 1344-1354Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbabio.2008.07.002
Keywords
Cyanobacteria; Iron starvation; Non-photochemical quenching; Orange-carotenoid-protein; Photoprotection; Photosystem II
Categories
Funding
- EU network [INTRO2]
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Excess light is harmful for photosynthetic organisms. The cyanobacterium Synechocystis PCC 6803 protects itself by dissipating the excess of energy absorbed by the phycobilisome, the water-soluble antenna of Photosystem II, into heat decreasing the excess energy arriving to the reaction centers. Energy dissipation results in a detectable decrease of fluorescence. The soluble Orange Carotenoid Protein (OCP) is essential for this blue-green light induced mechanism. OCP genes appear to be highly conserved among phycobilisome-containing cyanobacteria with few exceptions. Here, we show that only the strains containing a whole OCP gene can perform a blue-light induced photoprotective mechanism under both iron-replete and iron-starvation conditions. In contrast, strains containing only N-terminal and/or C-terminal OCP-like genes, or no OCP-like genes at all lack this light induced photoprotective mechanism and they were more sensitive to high-light illumination. These strains must adopt a different strategy to longer survive under stress conditions. Under iron starvation, the relative decrease of phycobiliproteins was larger in these strains than in the OCP-containing strains, avoiding the appearance of a population of dangerous, functionally disconnected phycobilisomes. The OCP-containing strains protect themselves from high light, notably under conditions inducing the appearance of disconnected phycobilisomes, using the energy dissipation OCP-phycobilisome mechanism. (C) 2008 Elsevier B.V. All rights reserved.
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