title: Redox regulation in the thylakoid lumen.
abstract: Higher plants need to balance the efficiency of light energy absorption and dissipative photo-protection when exposed to fluctuations in light quantity and quality. This aim is partially realized through redox regulation within the chloroplast, which occurs in all chloroplast compartments except the envelope intermembrane space. In contrast to the chloroplast stroma, less attention has been paid to the thylakoid lumen, an inner, continuous space enclosed by the thylakoid membrane in which redox regulation is also essential for photosystem biogenesis and function. This sub-organelle compartment contains at least 80 lumenal proteins, more than 30 of which are known to contain disulfide bonds. Thioredoxins (Trx) in the chloroplast stroma are photo-reduced in the light, transferring reducing power to the proteins in the thylakoid membrane and ultimately the lumen through a trans-thylakoid membrane-reduced, equivalent pathway. The discovery of lumenal thiol oxidoreductase highlights the importance of the redox regulation network in the lumen for controlling disulfide bond formation, which is responsible for protein activity and folding and even plays a role in photo-protection. In addition, many lumenal members involved in photosystem assembly and non-photochemical quenching are likely required for reduction and/or oxidation to maintain their proper efficiency upon changes in light intensity. In light of recent findings, this review summarizes the multiple redox processes that occur in the thylakoid lumen in great detail, highlighting the essential auxiliary roles of lumenal proteins under fluctuating light conditions.
authors.affiliation: Key Laboratory of Biorheological Science and Technology (Chongqing University), Ministry of Education, Bioengineering College of Chongqing University, Chongqing 400030, China.
authors.forename: Zhen-Hui
authors.initials: ZH
authors.lastname: Kang
authors.affiliation: Key Laboratory of Biorheological Science and Technology (Chongqing University), Ministry of Education, Bioengineering College of Chongqing University, Chongqing 400030, China. Electronic address: wanggx@cqu.edu.cn.
authors.forename: Gui-Xue
authors.initials: GX
authors.lastname: Wang
mesh_terms: D017360:Arabidopsis / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism* / Q000528:radiation effects; D008027:Light; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D013879:Thioredoxins / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D013879:Thioredoxins; D010088:Oxidoreductases
keywords: Disulfide; Photosynthetic efficiency; Redox; Thiol; Thylakoid lumen