FZL is primarily localized to the inner chloroplast membrane however influences thylakoid maintenance
FZL is primarily localized to the chloroplast inner envelope and not to the thylakoids, but nevertheless affects the maintenance of thylakoid membranes and photosynthetic protein complexes.
The fuzzy-onion-like protein (FZL) is a membrane-bound dynamin-like GTPase located in the chloroplast. We have investigated the chloroplast sub-localization of the endogenous FZL protein and found it to be primarily localized to the inner envelope. Moreover, we observed that mature leaves of fzl mutants start to turn pale, especially in the midvein area of the leaves, 11 days after germination. We therefore assessed their photosynthetic performance as well as the accumulation of thylakoid membrane proteins and complexes after the initial appearance of the phenotype. Interestingly, we could observe a significant decrease in amounts of the cytochrome b6f complex in 20-day-old mutants, which was also reflected in an impaired electron transport rate as well as a more oxidized P700 redox state. Analysis of differences in transcriptome datasets obtained before and after onset of the phenotype, revealed large-scale changes in gene expression after the phenotype became visible. In summary, we propose that FZL, despite its localization in the inner chloroplast envelope has an important role in thylakoid maintenance in mature and aging leaves.
KeywordsChloroplast Dynamin-like protein Inner envelope Thylakoid Arabidopsis
This project was funded by the Deutsche Forschungsgemeinschaft (DFG), TR175, Project B05 to J.S. and SFB1035, Project A04 to S.S. F.S. was financially supported by Rhenac Green Tec AG (Hennef, Germany) for some time of the conducted study. We would like to thank Sabine Grahl for data analysis and help with supervision. Antje von Schaewen and Jörg Meurer are kindly acknowledged for providing antisera. We would further like to thank Chris Carrie and his group for providing isolated mitochondria.
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