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

• Published in: Molecular plant Vol. 10; no. 1; pp. 99 - 114
• Main Authors: Wang, Fei, Qi, Yafei, Malnoë, Alizée, Choquet, Yves, Wollman, Francis-André, de Vitry, Catherine
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 09-01-2017; Cell Press/Oxford UP
• Subjects: Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biochemistry, Molecular Biology; Chlamydomonas reinhardtii; Chlamydomonas reinhardtii - genetics; Chlamydomonas reinhardtii - metabolism; Chlamydomonas reinhardtii - radiation effects; chloroplast protease; Life Sciences; Light; Metalloproteases - genetics; Metalloproteases - metabolism; Molecular biology; Oxidation-Reduction; photoinhibition; Promoter Regions, Genetic; Protein Isoforms - genetics; Protein Isoforms - metabolism; Proteolysis; regulation of gene expression; Suppression, Genetic; Thylakoid Membrane Proteins - genetics; Thylakoid Membrane Proteins - metabolism; regulation of gene expression; chloroplast protease; photoinhibition; Chlamydomonas reinhardtii
• ISSN: 1674-2052; 1752-9867; 1752-9867
• DOI: 10.1016/j.molp.2016.09.012

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 iso- lated 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 FtsH 1/2 subunits associated into large complexes with increased proteolytic activity.