Lipid and carotenoid cooperation-driven adaptation to light and temperature stress in Synechocystis sp. PCC6803

Abstract

Polyunsaturated lipids are important components of photosynthetic membranes. Xanthophylls are the main photoprotective agents, can assist in protection against light stress, and are crucial in the recovery from photoinhibition. We generated the xanthophyll- and polyunsaturated lipid-deficient ROAD mutant of Synechocystis sp. PCC6803 (Synechocystis) in order to study the little-known cooperative effects of lipids and carotenoids (Cars). Electron microscopic investigations confirmed that in the absence of xanthophylls the S-layer of the cellular envelope is missing. In wild-type (WT) cells, as well as the xanthophyll-less (RO), polyunsaturated lipid-less (AD), and the newly constructed ROAD mutants the lipid and Car compositions were determined by MS and HPLC, respectively. We found that, relative to the WT, the lipid composition of the mutants was remodeled and the Car content changed accordingly. In the mutants the ratio of non-bilayer-forming (NBL) to bilayer-forming (BL) lipids were found considerably lower. Xanthophyll to β-carotene ratio increased in the AD mutant. In vitro and in vivo methods demonstrated that saturated, monounsaturated lipids and xanthophylls may stabilize the trimerization of Photosystem I (PSI). Fluorescence induction and oxygen-evolving activity measurements revealed increased light sensitivity of RO cells compared to those of the WT. ROAD showed a robust increase in light susceptibility and reduced recovery capability, especially at moderate low (ML) and moderate high (MH) temperatures, indicating a cooperative effect of xanthophylls and polyunsaturated lipids. We suggest that both lipid unsaturation and xanthophylls are required for providing the proper structure and functioning of the membrane environment that protects against light and temperature stress.

Influence of osmolytes on the stability of thylakoid‐based dye‐sensitized solar cells

“…The efficiency of these cells remains very low, and pigmentprotein complexes are very susceptible to degradation over time in vitro, yielding a short lifespan of such solar devices. [17][18][19] From this viewpoint, it can be proposed that retention of the native membrane environment may preserve photosystem proteins after membrane extraction. 15,16 In the latter case, deterioration of biological structures during the bio-based preparation is also expected to lead to the low efficiencies currently observed in these solar cells.…”

“…Previously published data suggest that the specialized galactolipid environment of the thylakoid membrane stabilizes the PSII and PSI complexes. [17][18][19] From this viewpoint, it can be proposed that retention of the native membrane environment may preserve photosystem proteins after membrane extraction. 10,20 However, the bilayer structure of the thylakoid membrane is also sensitive to high temperatures, which can cause phase transitions of the surrounding lipids and subsequent cessation of electron transport.…”

Lipidek és karotinoidok szerepe a cianobakteriális fotoszintetikus makrokomplexek kialakulásában

“…A WT-ban és mutáns törzsekben lévő PSI oligomer szintek összehasonlítása érdekében két in vitro (natív PAGE, FPLC) és két in vivo (mélyhőmérsékletű fluoreszcens emissziós spektroszkópia, cirkuláris dikroizmus -CD -spektroszkópia) módszert alkalmaztam. (Zakar et al, 2017). III.…”

“…A többszörösen telítetlen lipidek eltávolítása a xantofill tartalom átszerveződését eredményezte, növelve a xantofill-t a β-karotin aránnyal szemben. Kimutattuk, hogy a lipidek és a Car-ok együttműködnek a membránszerkezetek fenntartásában és védelmében (Zakar et al, 2017).…”

“…A xantofillok hiánya ebben az esetben sokkal hangsúlyosabb volt. A fotoszintetikus komplexek xantofilljainak pontos helyzete továbbra is ismeretlen a tudomány számára, ezért a jövőben érdemes lesz ezt a területet kutatni (Zakar et al, 2017). IV.…”