期刊
JOURNAL OF PHYCOLOGY
卷 48, 期 1, 页码 145-154出版社
WILEY
DOI: 10.1111/j.1529-8817.2011.01092.x
关键词
chlorophyll-binding protein; cyanobacteria; iron limitation; IsiA; PSI
资金
- Natural Environment Research Council (UK) [NF/F019254/1, NE/G009155/1]
- NERC [NE/G009155/1, NE/F019254/1] Funding Source: UKRI
- Natural Environment Research Council [NE/F019254/1, NE/G009155/1] Funding Source: researchfish
Iron availability limits primary production in >30% of the worlds oceans; hence phytoplankton have developed acclimation strategies. In particular, cyanobacteria express IsiA (iron-stress-induced) under iron stress, which can become the most abundant chl-binding protein in the cell. Within iron-limited oceanic regions with significant cyanobacterial biomass, IsiA may represent a significant fraction of the total chl. We spectroscopically measured the effective cross-section of the photosynthetic reaction center PSI (sPSI) in vivo and biochemically quantified the absolute abundance of PSI, PSII, and IsiA in the model cyanobacterium Synechocystis sp. PCC 6803. We demonstrate that accumulation of IsiA results in a similar to 60% increase in sPSI, in agreement with the theoretical increase in cross-section based on the structure of the biochemically isolated IsiA-PSI supercomplex from cyanobacteria. Deriving a chl budget, we suggest that IsiA plays a primary role as a light-harvesting antenna for PSI. On progressive iron-stress in culture, IsiA continues to accumulate without a concomitant increase in sPSI, suggesting that there may be a secondary role for IsiA. In natural populations, the potential physiological significance of the uncoupled pool of IsiA remains to be established. However, the functional role as a PSI antenna suggests that a large fraction of IsiA-bound chl is directly involved in photosynthetic electron transport.
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