Symposium on Thylakoid biogenesis and Regulation of Photosynthesis – University of Copenhagen

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Symposium on Thylakoid biogenesis and Regulation of Photosynthesis

Eva-Mari Aro, Department of Biochemistry, University of Turku, Finland:

Regulation of oxygen evolving photosynthesis – evolutionary considerations

The principal water oxidation reactions leading to release of oxygen as well as the linear electron transport via the two photosystems have remained fairly unchanged during the evolution of cyanobacteria, algae, mosses and higher plants. However, the regulatory mechanisms protecting the photosynthetic apparatus from photo-oxidative damage show distinct evolutionary differences and a number of specific regulation mechanisms has appeared in oxygenic photosynthetic organisms.

While cyanobacteria rely heavily on electron valves to dissipate excess electrons, algae, mosses and higher plants have gradually replaced them with more sophisticated regulatory mechanisms that exert protection to both photosystems. Such evolution in photo-protective mechanisms was necessary for the transition of photosynthetic organisms from the aquatic to the terrestrial environment. 

Jörg Nickelsen, Biocenter LMU Munich, Molecular Plant Sciences, Planegg-Martinsried, Germany: 

Biogenesis of Cyanobacterial Thylakoid Membranes

Cyanobacteria, algae and plants convert light energy into chemical energy by using a very similar type of photosynthetic membrane system, named thylakoids. Current molecular analyses suggest that the biogenesis of the cyanobacterial energy conversion system, in particular photosystem (PS) II, is initiated in dedicated membrane sub-fractions at the cellular periphery.

Here, these membranes form centres which are marked by the manganese- transporting PS II assembly factor PratA. PratA forms a complex with the protease HhoA and the pilus-related factor PilQ. Moreover, center formation depends on the membrane curving protein CurT, a homolog of the chloroplast grana-forming CURT1 protein family. By applying cryo EM tomography, we dismantled the in situ ultrastructure of biogenesis centers.