Quenching of excess light energy: PsbS, one big part of the puzzle

  • Datum: 28.10.2015
  • Uhrzeit: 14:00 - 15:30
  • Vortragende(r): Viviana Correa Galvis
  • Ort: Central Building
  • Raum: Seminar Room
  • Gastgeber: Ute Armbruster
Sunlight is the ultimate energy source driving photosynthesis. In nature, however, absorbed light energy often exceeds the capacity of light utilization in photosynthesis, giving rise to the formation of reactive oxygen species and thus photo-oxidative damage of the chloroplast. Non-photochemical quenching of excitation energy (NPQ) in the antenna of Photosystem II (PSII) allows the harmless dissipation of excess light energy as heat and thereby avoids oxidative damage to the photosynthetic apparatus. Four different mechanisms contribute to NPQ, termed qT, qE, qZ and qI. Under saturating light conditions, the energy dependent-quenching mechanism (qE) represents the dominant NPQ component; qE is based on a complex mechanism which strictly depends on three factors: (i) lumen pH, (ii) the PsbS protein and (iii) the xanthophyll zeaxanthin (Zx). According to the current understanding of qE, a low pH in the thylakoid lumen induces PsbS-dependent conformational changes in the PSII antenna and formation of Zx, both being central for activation of maximum qE capacity. The central role of PsbS in these processes is related to the function of PsbS as sensor of lumenal pH. Our work focuses on the identification of protein interaction partners of PsbS and how these interactions contribute to the pH-regulated reorganization of the PSII antenna during activation of NPQ. Additionally, we are interested in the role of PsbS in green algae as an approach to understand the evolution of photoprotective mechanisms. Altogether, our findings support that throughout land colonization of plants, PsbS evolved as a key player in energy dissipation by modulating light induced protein interactions in the PSII-Antenna required for the activation of qE.
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