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Mol Plant. 2017 Jan 9;10(1):99-114. doi: 10.1016/j.molp.2016.09.012. Epub 2016 Oct 1.

The High Light Response and Redox Control of Thylakoid FtsH Protease in Chlamydomonas reinhardtii.

Author information

1
Institut de Biologie Physico-Chimique, Unité Mixte de Recherche 7141, Centre National de la Recherche Scientifique/Université Pierre et Marie Curie, Paris 75005, France.
2
Institut de Biologie Physico-Chimique, Unité Mixte de Recherche 7141, Centre National de la Recherche Scientifique/Université Pierre et Marie Curie, Paris 75005, France. Electronic address: catherine.devitry@ibpc.fr.

Abstract

In Chlamydomonas reinhardtii, the major protease involved in the maintenance of photosynthetic machinery in thylakoid membranes, the FtsH protease, mostly forms large hetero-oligomers (∼1 MDa) comprising FtsH1 and FtsH2 subunits, whatever the light intensity for growth. Upon high light exposure, the FtsH subunits display a shorter half-life, which is counterbalanced by an increase in FTSH1/2 mRNA levels, resulting in the modest upregulation of FtsH1/2 proteins. Furthermore, we found that high light increases the protease activity through a hitherto unnoticed redox-controlled reduction of intermolecular disulfide bridges. We isolated a Chlamydomonas FTSH1 promoter-deficient mutant, ftsh1-3, resulting from the insertion of a TOC1 transposon, in which the high light-induced upregulation of FTSH1 gene expression is largely lost. In ftsh1-3, the abundance of FtsH1 and FtsH2 proteins are loosely coupled (decreased by 70% and 30%, respectively) with no formation of large and stable homo-oligomers. Using strains exhibiting different accumulation levels of the FtsH1 subunit after complementation of ftsh1-3, we demonstrate that high light tolerance is tightly correlated with the abundance of the FtsH protease. Thus, the response of Chlamydomonas to light stress involves higher levels of FtsH1/2 subunits associated into large complexes with increased proteolytic activity.

KEYWORDS:

Chlamydomonas reinhardtii; chloroplast protease; photoinhibition; regulation of gene expression

PMID:
27702692
DOI:
10.1016/j.molp.2016.09.012
[Indexed for MEDLINE]
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