CeBiTec Colloquium
Monday, November 25th 2013, 17 c.t.
G2-104, CeBiTec Building
Prof. Dr. Roberto Bassi
Department of Biotechnology, University for Studies of Verona (Italy)
Regulation of photosynthetic light use efficiency in algae and mosses

Photosynthesis is light-dependent and yet excess light causes its inhibition by photooxidative damage. Photosynthesis evolved in anaerobiosis or very low oxygen. Present oxygenic atmosphere is a poison for plant photosynthesis because it is both a good electron acceptor for energized electrons from photosynthetic electron transport and a reactant for chlorophyll triplet excited states generated in the antenna system, yielding singlet oxygen. Photosynthetic organisms evolved photoprotective processes to survive this stressing environment. The fastest-responding mechanism, called Non Photochemical Quenching (NPQ) leads to the dissipation of excess energy as heat. Signalling of excess light depends on ATP/NADPH accumulation through chloroplast lumen acidification. The pH-responding trigger for NPQ in green algae is the LHCSR protein, an homologous of plant PSBS. Green algae exhibit a large variability in the NPQ response depending on species and environmental cues. The interplay between the identified component of NPQ machinery can be studied by using as model system Chlamydomonas reinhardtii for non-zeaxanthin dependent NPQ and the moss Physcomitrella patens for zeaxanthin-dependent NPQ. In P. p. NPQ depends on both LHCSR and PSBS thus making it the only available model for both algal-like and plant-like photoprotection. By this tool we have tracked the fate of zeaxanthin synthesized in high light and found it binds to LHCSR. We conclude that the feed-back regulation of light use in algal photosynthesis is activated synergically by protonation of LHCSR and the binding of zeaxanthin to specific sites. The consequences for increasing the yield of algal growth in photobioreactors are discussed.

Host: Prof. Dr. Olaf Kruse