The chlorophyll-binding protein IsiA is inducible by high light and protects the cyanobacterium Synechocystis PCC6803 from photooxidative stress.
The products of the isiAB operon are a chlorophyll antenna protein (IsiA) and flavodoxin (IsiB), which accumulate in cyanobacteria grown under iron starvation conditions. Here we show that strong light triggers de-repression of isiAB transcription and leads to IsiA and flavodoxin accumulation under iron replete conditions. Genetic deletion of isiAB resulted in a photosensitive phenotype, with accumulation of reactive oxygen species and cell bleaching in high light, while the flavodoxin-deficient isiB null mutant expressing isiA was phototolerant. We conclude that IsiA protects cyanobacteria from photooxidative stress. IsiA is the first example of a chlorophyll antenna protein outside the extended LHC family that is induced transiently by high light and that fulfills a photoprotective role.
Havaux
Michel
M
CEA/Cadarache, DSV, DEVM, Laboratoire d'Ecophysiologie de la Photosynthèse, UMR 6191 CNRS-CEA-Aix Marseille II, Saint-Paul-lez-Durance, France. michel.havaux@cea.fr
Guedeney
Geneviève
G
Hagemann
Martin
M
Yeremenko
Nataliya
N
Matthijs
Hans C P
HC
Jeanjean
Robert
R
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010083:Oxidants, Photochemical / Q000378:metabolism*; D018384:Oxidative Stress / Q000528:radiation effects*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects*
D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D010083:Oxidants, Photochemical; D012333:RNA, Messenger; C076726:chlorophyll A binding protein CP43, Cyanobacteria