title: Thioredoxin targets of the plant chloroplast lumen and their implications for plastid function.
abstract: The light-dependent regulation of stromal enzymes by thioredoxin (Trx)-catalysed disulphide/dithiol exchange is known as a classical mechanism for control of chloroplast metabolism. Recent proteome studies show that Trx targets are present not only in the stroma but in all chloroplast compartments, from the envelope to the thylakoid lumen. Trx-mediated redox control appears to be a common feature of important pathways, such as the Calvin cycle, starch synthesis and tetrapyrrole biosynthesis. However, the extent of thiol-dependent redox regulation in the thylakoid lumen has not been previously systematically explored. In this study, we addressed Trx-linked redox control in the chloroplast lumen of Arabidopsis thaliana. Using complementary proteomics approaches, we identified 19 Trx target proteins, thus covering more than 40% of the currently known lumenal chloroplast proteome. We show that the redox state of thiols is decisive for degradation of the extrinsic PsbO1 and PsbO2 subunits of photosystem II. Moreover, disulphide reduction inhibits activity of the xanthophyll cycle enzyme violaxanthin de-epoxidase, which participates in thermal dissipation of excess absorbed light. Our results indicate that redox-controlled reactions in the chloroplast lumen play essential roles in the function of photosystem II and the regulation of adaptation to light intensity.
authors.affiliation: Department of Chemistry, Umea3 University, Umea3, Sweden.
authors.forename: Michael
authors.initials: M
authors.lastname: Hall
authors.forename: Alejandro
authors.initials: A
authors.lastname: Mata-Cabana
authors.forename: Hans-Erik
authors.initials: HE
authors.lastname: Akerlund
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Florencio
authors.forename: Wolfgang P
authors.initials: WP
authors.lastname: Schröder
authors.forename: Marika
authors.initials: M
authors.lastname: Lindahl
authors.forename: Thomas
authors.initials: T
authors.lastname: Kieselbach
mesh_terms: D000478:Alkylation / Q000187:drug effects; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000302:isolation & purification / Q000378:metabolism; D055162:Biocatalysis / Q000187:drug effects; D001643:Bridged Bicyclo Compounds / Q000378:metabolism; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism*; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D010084:Oxidation-Reduction / Q000187:drug effects; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D020543:Proteome / Q000378:metabolism; D013194:Staining and Labeling; D013438:Sulfhydryl Compounds / Q000378:metabolism; D046939:Synechocystis / Q000378:metabolism; D013879:Thioredoxins / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D029681:Arabidopsis Proteins; D001643:Bridged Bicyclo Compounds; D020543:Proteome; D013438:Sulfhydryl Compounds; D013879:Thioredoxins; D010088:Oxidoreductases; C023290:violaxanthin de-epoxidase; C028381:monobromobimane