Thylakoid FtsH protease contributes to photosystem II and cytochrome b6f remodeling in Chlamydomonas reinhardtii under stress conditions.
FtsH is the major thylakoid membrane protease found in organisms performing oxygenic photosynthesis. Here, we show that FtsH from Chlamydomonas reinhardtii forms heterooligomers comprising two subunits, FtsH1 and FtsH2. We characterized this protease using FtsH mutants that we identified through a genetic suppressor approach that restored phototrophic growth of mutants originally defective for cytochrome b6f accumulation. We thus extended the spectrum of FtsH substrates in the thylakoid membranes beyond photosystem II, showing the susceptibility of cytochrome b6f complexes (and proteins involved in the ci heme binding pathway to cytochrome b6) to FtsH. We then show how FtsH is involved in the response of C. reinhardtii to macronutrient stress. Upon phosphorus starvation, photosynthesis inactivation results from an FtsH-sensitive photoinhibition process. In contrast, we identified an FtsH-dependent loss of photosystem II and cytochrome b6f complexes in darkness upon sulfur deprivation. The D1 fragmentation pattern observed in the latter condition was similar to that observed in photoinhibitory conditions, which points to a similar degradation pathway in these two widely different environmental conditions. Our experiments thus provide extensive evidence that FtsH plays a major role in the quality control of thylakoid membrane proteins and in the response of C. reinhardtii to light and macronutrient stress.
Institut de Biologie Physico-Chimique, Unité Mixte de Recherche 7141, Centre National de la Recherche Scientifique/Université Pierre et Marie Curie, Paris 6, 75005 Paris, France.
Alizée
A
Malnoë
Fei
F
Wang
Jacqueline
J
Girard-Bascou
Francis-André
FA
Wollman
Catherine
C
de Vitry
D049069:ATP-Dependent Proteases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D016825:Chlamydomonas reinhardtii / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D045346:Cytochrome b6f Complex / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D017354:Point Mutation; D013312:Stress, Physiological; D020524:Thylakoids / Q000378:metabolism*
D020418:Algal Proteins; D045332:Photosystem II Protein Complex; D045346:Cytochrome b6f Complex; D049069:ATP-Dependent Proteases