title: Elevated growth temperature can enhance photosystem I trimer formation and affects xanthophyll biosynthesis in Cyanobacterium Synechocystis sp. PCC6803 cells.
abstract: In the thylakoid membranes of the mesophilic cyanobacterium Synechocystis PCC6803, PSI reaction centers (RCs) are organized as monomers and trimers. PsaL, a 16 kDa hydrophobic protein, a subunit of the PSI RC, was previously identified as crucial for the formation of PSI trimers. In this work, the physiological effects accompanied by PSI oligomerization were studied using a PsaL-deficient mutant (ΔpsaL), not able to form PSI trimers, grown at various temperatures. We demonstrate that in wild-type Synechocystis, the monomer to trimer ratio depends on the growth temperature. The inactivation of the psaL gene in Synechocystis grown phototropically at 30°C induces profound morphological changes, including the accumulation of glycogen granules localized in the cytoplasm, resulting in the separation of particular thylakoid layers. The carotenoid composition in ΔpsaL shows that PSI monomerization leads to an increased accumulation of myxoxantophyll, zeaxanthin and echinenone irrespective of the temperature conditions. These xanthophylls are formed at the expense of β-carotene. The measured H2O→CO2 oxygen evolution rates in the ΔpsaL mutant are higher than those observed in the wild type, irrespective of the growth temperature. Moreover, circular dichroism spectroscopy in the visible range reveals that a peak attributable to long-wavelength-absorbing carotenoids is apparently enhanced in the trimer-accumulating wild-type cells. These results suggest that specific carotenoids are accompanied by the accumulation of PSI oligomers and play a role in the formation of PSI oligomer structure.
authors.affiliation: Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland.
authors.forename: Kinga
authors.initials: K
authors.lastname: Kłodawska
authors.affiliation: Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Hungary.
authors.forename: László
authors.initials: L
authors.lastname: Kovács
authors.affiliation: Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Hungary.
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Várkonyi
authors.affiliation: Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Hungary.
authors.forename: Mihály
authors.initials: M
authors.lastname: Kis
authors.affiliation: Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Hungary.
authors.forename: Özge
authors.initials: Ö
authors.lastname: Sozer
authors.affiliation: Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Hungary.
authors.forename: Hajnalka
authors.initials: H
authors.lastname: Laczkó-Dobos
authors.affiliation: Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Hungary.
authors.forename: Ottilia
authors.initials: O
authors.lastname: Kóbori
authors.affiliation: Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Hungary.
authors.forename: Ildikó
authors.initials: I
authors.lastname: Domonkos
authors.affiliation: Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland.
authors.forename: Kazimierz
authors.initials: K
authors.lastname: Strzałka
authors.affiliation: Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Gombos
authors.affiliation: Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland przemyslaw.malec@uj.edu.pl.
authors.forename: Przemysław
authors.initials: P
authors.lastname: Malec
mesh_terms: D052818:Autotrophic Processes; D002338:Carotenoids / Q000378:metabolism; D002852:Chromatography, Ion Exchange; D002942:Circular Dichroism; D020868:Gene Silencing; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D006358:Hot Temperature; D009154:Mutation / Q000235:genetics; D010100:Oxygen / Q000378:metabolism; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D052817:Phototrophic Processes; D055503:Protein Multimerization; D046939:Synechocystis / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism* / Q000648:ultrastructure; D020524:Thylakoids / Q000378:metabolism; D024341:Xanthophylls / Q000096:biosynthesis*
chemical_list: D045331:Photosystem I Protein Complex; D024341:Xanthophylls; D002338:Carotenoids; D010100:Oxygen
keywords: CD spectra; Carotenoids; PSI trimer; PsaL-deficient mutant; Synechocystis