High Light Induced Disassembly of Photosystem II Supercomplexes in Arabidopsis Requires STN7-Dependent Phosphorylation of CP29

Photosynthetic oxidation of water and production of oxygen by photosystem II (PSII) in thylakoid membranes of plant chloroplasts is highly affected by changes in light intensities. To minimize damage imposed by excessive sunlight and sustain the photosynthetic activity PSII, organized in supercomplexes with its light harvesting antenna, undergoes conformational changes, disassembly and repair via not clearly understood mechanisms. We characterized the phosphoproteome of the thylakoid membranes from Arabidopsis thaliana wild type, stn7, stn8 and stn7stn8 mutant plants exposed to high light. The high light treatment of the wild type and stn8 caused specific increase in phosphorylation of Lhcb4.1 and Lhcb4.2 isoforms of the PSII linker protein CP29 at five different threonine residues. Phosphorylation of CP29 at four of these residues was not found in stn7 and stn7stn8 plants lacking the STN7 protein kinase. Blue native gel electrophoresis followed by immunological and mass spectrometric analyses of the membrane protein complexes revealed that the high light treatment of the wild type caused redistribution of CP29 from PSII supercomplexes to PSII dimers and monomers. A similar high-light-induced disassembly of the PSII supercomplexes occurred in stn8, but not in stn7 and stn7stn8. Transfer of the high-light-treated wild type plants to normal light relocated CP29 back to PSII supercomplexes. We postulate that disassembly of PSII supercomplexes in plants exposed to high light involves STN7-kinase-dependent phosphorylation of the linker protein CP29. Disruption of this adaptive mechanism can explain dramatically retarded growth of the stn7 and stn7stn8 mutants under fluctuating normal/high light conditions, as previously reported

FINANCIAL DISTRESS AND INDUSTRY STRUCTURE: AN INTER-INDUSTRY APPROACH TO THE LOST DECADE IN JAPAN

This paper proposes a novel approach to investigating the propagation mechanism of balance sheet deterioration in financial institutions and firms, by extending the input-output analysis. First, we use a unique input-output table augmented by firm size dimension. Second, we link the input-output table with the balance sheet conditions of financial institutions and firms. Based on Japanese input-output tables, we find that the lending attitude of financial institutions affected firms' input decision in the late 1990s and the early 2000s. Simulation exercises are conducted to evaluate the effects of changes in the lending attitude toward small firms as favorable as that toward large firms on sectoral allocations. We find that output was increased for small firms and reduced for large firms. The change in output was non-negligible, about 5.5% of the initial output of each sector. In particular, it exceeded 20% in textile, iron and steel and fabricated metal products

Light-independent regulation of algal photoprotection by CO2 availability

Photosynthetic algae have evolved to survive in suboptimal light and CO2 conditions. Here, the authors show that depletion of CO2 can drive photoprotection and carbon acquisition even in the absence of light, that was previously believed to be indispensable for the activation of these processes

RNAi Knock-Down of LHCBM1, 2 and 3 Increases Photosynthetic H-2 Production Efficiency of the Green Alga Chlamydomonas reinhardtii

Single cell green algae (microalgae) are rapidly emerging as a platform for the production of sustainable fuels. Solar-driven H-2 production from H2O theoretically provides the highest-efficiency route to fuel production in microalgae. This is because the H-2-producing hydrogenase (HYDA) is directly coupled to the photosynthetic electron transport chain, thereby eliminating downstream energetic losses associated with the synthesis of carbohydrate and oils (feedstocks for methane, ethanol and oil-based fuels). Here we report the simultaneous knock-down of three light-harvesting complex proteins (LHCMB1, 2 and 3) in the high H-2-producing Chlamydomonas reinhardtii mutant Stm6Glc4 using an RNAi triple knock-down strategy. The resultant Stm6Glc4L01 mutant exhibited a light green phenotype, reduced expression of LHCBM1 (20.6% +/- 0.27%), LHCBM2 (81.2% +/- 0.037%) and LHCBM3 (41.4% +/- 0.05%) compared to 100% control levels, and improved light to H-2 (180%) and biomass (165%) conversion efficiencies. The improved H-2 production efficiency was achieved at increased solar flux densities (450 instead of similar to 100 mu E m(-2) s(-1)) and high cell densities which are best suited for microalgae production as light is ideally the limiting factor. Our data suggests that the overall improved photon-to-H-2 conversion efficiency is due to: 1) reduced loss of absorbed energy by non-photochemical quenching (fluorescence and heat losses) near the photobioreactor surface; 2) improved light distribution in the reactor; 3) reduced photoinhibition; 4) early onset of HYDA expression and 5) reduction of O-2-induced inhibition of HYDA. The Stm6Glc4L01 phenotype therefore provides important insights for the development of high-efficiency photobiological H-2 production systems