Revealing the architecture of the photosynthetic apparatus in the diatom Thalassiosira pseudonana |
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| Authors: | Rameez Arshad,Claudio Calvaruso,Egbert J Boekema,Claudia Bü chel,Roman Kouř il |
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| Affiliation: | 1. Department of Biophysics, Faculty of Science, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University, Olomouc 78371, Czech Republic;2. Electron Microscopy Group, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen 9747AG, The Netherlands;3. Institute for Molecular Biosciences, Goethe University of Frankfurt, Frankfurt 60438, Germany |
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| Abstract: | Diatoms are a large group of marine algae that are responsible for about one-quarter of global carbon fixation. Light-harvesting complexes of diatoms are formed by the fucoxanthin chlorophyll a/c proteins and their overall organization around core complexes of photosystems (PSs) I and II is unique in the plant kingdom. Using cryo-electron tomography, we have elucidated the structural organization of PSII and PSI supercomplexes and their spatial segregation in the thylakoid membrane of the model diatom species Thalassiosira pseudonana. 3D sub-volume averaging revealed that the PSII supercomplex of T. pseudonana incorporates a trimeric form of light-harvesting antenna, which differs from the tetrameric antenna observed previously in another diatom, Chaetoceros gracilis. Surprisingly, the organization of the PSI supercomplex is conserved in both diatom species. These results strongly suggest that different diatom classes have various architectures of PSII as an adaptation strategy, whilst a convergent evolution occurred concerning PSI and the overall plastid structure. The antenna organization of photosystem II in the diatom Thalassiosira pseudonana strongly differs from Chaetoceros gracilis, while the architecture of the photosystem I antenna remains the same. |
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