Oxidation-reduction signalling components in regulatory pathways of state transitions and photosystem stoichiometry adjustment in chloroplasts

• Published in: Plant, cell and environment Vol. 35; no. 2; pp. 347 - 359
• Main Authors: PUTHIYAVEETIL, SUJITH, IBRAHIM, ISKANDER M., ALLEN, JOHN F.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.02.2012
• Subjects: adaptability; Adaptation, Physiological; Adaptations; Algae; Arabidopsis; Chlamydomonas; Chloroplast DNA; chloroplast genome; chloroplast sensor kinase; Chloroplasts; Chloroplasts - chemistry; Chloroplasts - enzymology; Chloroplasts - genetics; CoRR hypothesis; DNA; downstream; Gene regulation; Harvesting; Light; Light effects; light-harvesting complex; light-harvesting complex II; Light-Harvesting Protein Complexes - chemistry; Light-Harvesting Protein Complexes - metabolism; Oxidation-Reduction; Phosphoprotein Phosphatases - metabolism; Phosphorylation; Photosynthesis; Photosystem; Photosystem I; Photosystem II; Plant Proteins - metabolism; Plants - chemistry; Plants - enzymology; Plants - genetics; Plastids; plastoquinone; Plastoquinone - metabolism; plastoquinones; Post-translation; protein phosphatase; Protein-Serine-Threonine Kinases - metabolism; Protein-serine/threonine kinase; Protein-tyrosine kinase; Proteins; Redox properties; redox sensor; redox signalling; Sensors; serine/threonine kinase; Sigma factor; Signal Transduction; Transcription; Transcription, Genetic; two-component systems
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/j.1365-3040.2011.02349.x

ABSTRACT State transitions and photosystem stoichiometry adjustment are two oxidation–reduction (redox)‐regulated acclimatory responses in photosynthesis. State transitions are short‐term adaptations that, in chloroplasts, involve reversible post‐translational modification by phosphorylation of light‐harvesting complex II (LHC II). Photosystem stoichiometry adjustments are long‐term responses involving transcriptional regulation of reaction centre genes. Both responses are initiated by changes in light quality and are regulated by the redox state of plastoquinone (PQ). The LHC II kinase involved in the state 2 transition is a serine/threonine kinase known as STT7 in Chlamydomonas, and as STN7 in Arabidopsis. The phospho‐LHC II phosphatase that produces the state 1 transition is a PP2C‐type protein phosphatase currently termed both TAP38 and PPH1. In plants and algae, photosystem stoichiometry adjustment is governed by a modified two‐component sensor kinase of cyanobacterial origin – chloroplast sensor kinase (CSK). CSK is a sensor of the PQ redox state. Chloroplast sigma factor 1 (SIG1) and plastid transcription kinase (PTK) are the functional partners of CSK in chloroplast gene regulation. We suggest a signalling pathway for photosystem stoichiometry adjustment. The signalling pathways of state transitions and photosystem stoichiometry adjustments are proposed to be distinct, with the two pathways sensing PQ redox state independently of each other. State transitions are short‐term adaptations which, in chloroplasts, involve reversible post‐translational modification, by phosphorylation, of apoproteins of light harvesting complex II. In contrast, photosystem stoichiometry adjustments are long‐term responses involving transcriptional regulation of reaction centre genes located in chloroplast DNA. Both of these responses result from changes in the redox state of plastoquinone that are caused, in turn, by changes in light quality that alter the relative activities of photosystem I and photosystem II. Recent progress reveals that these two responses nevertheless each operate by means of downstream components that comprise separate and distinct pathways of signal transduction.