Document Detail

Expression of the isiA gene is essential for the survival of the cyanobacterium Synechococcus sp. PCC 7942 by protecting photosystem II from excess light under iron limitation.
MedLine Citation:
PMID:  10216865     Owner:  NLM     Status:  MEDLINE    
Iron deficiency is known to suppress primary productivity in both marine and freshwater ecosystems. In response to iron deficiency, certain cyanobacteria induce a chlorophyll (Chl)-protein complex, CP43', which is encoded by the isiA gene. The deduced amino-acid sequence of CP43' predicts some structural similarity to the CP43 polypeptide of photosystem II, but the function of CP43' remains uncertain. In order to assess its physiological role, the isiA gene of a cyanobacterium, Synechococcus sp. PCC7942, was inactivated by insertion mutagenesis (giving isiA cells). Compared with isiA cells, under iron deprivation, wild-type cells showed both lower rates of photosystem II-mediated O2 evolution at limiting light irradiances and decreased yields of room temperature Chl fluorescence at various irradiances. These observations strongly suggest that the decreased photosystem II activity in wild-type cells with CP43' is attributable to increased non-radiative dissipation of light energy. In agreement with this hypothesis, isiA cells were more susceptible to photoinhibition of photosynthesis than wild-type cells, resulting in much slower growth rates under iron limitation. Based on these results, we suggest that CP43' functions as a non-radiative dissipator of light energy, thus protecting photosystem II from excessive excitation under iron-deficient conditions.
Y I Park; S Sandström; P Gustafsson; G Oquist
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Molecular microbiology     Volume:  32     ISSN:  0950-382X     ISO Abbreviation:  Mol. Microbiol.     Publication Date:  1999 Apr 
Date Detail:
Created Date:  1999-07-07     Completed Date:  1999-07-07     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8712028     Medline TA:  Mol Microbiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  123-9     Citation Subset:  IM    
Department of Biology, Chungnam National University, Taejón, Korea.
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MeSH Terms
Bacterial Proteins / genetics*,  physiology*
Blotting, Southern
Carrier Proteins / genetics*,  physiology*
Chlorophyll / metabolism
Cyanobacteria / genetics*,  physiology*
Dose-Response Relationship, Radiation
Gene Expression
Iron / metabolism*
Light / adverse effects*
Light-Harvesting Protein Complexes*
Photosynthesis / physiology
Photosynthetic Reaction Center Complex Proteins*
Photosystem II Protein Complex
Time Factors
Transformation, Genetic
Reg. No./Substance:
0/Bacterial Proteins; 0/Carrier Proteins; 0/Light-Harvesting Protein Complexes; 0/Photosynthetic Reaction Center Complex Proteins; 0/Photosystem II Protein Complex; 1406-65-1/Chlorophyll; 148266-13-1/chlorophyll A binding protein CP43, Cyanobacteria; 7439-89-6/Iron

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