Cyanobacteria possess a family of one-helix high-light-inducible proteins (HLIPs) that are widely viewed as ancestors of the light-harvesting antenna of plants and algae. HLIPs are essential for viability under various stress conditions, although their exact role is not fully understood. The unicellular cyanobacterium Synechocystis sp. PCC 6803 contains four HLIPs named HliA-D, and HliD has recently been isolated in a small protein complex and shown to bind chlorophyll and β-carotene. However, no HLIP has been isolated and characterized in a pure form up to now. We have developed a protocol to purify large quantities of His-tagged HliC from an engineered Synechocystis strain. Purified His-HliC is a pigmented homo-oligomer and is associated with chlorophyll and β-carotene with a 2:1 ratio. This differs from the 3:1 ratio reported for HliD. Comparison of these two HLIPs by resonance Raman spectroscopy revealed a similar conformation for their bound β-carotenes, but clear differences in their chlorophylls. We present and discuss a structural model of HliC, in which a dimeric protein binds four chlorophyll molecules and two β-carotenes.

• Klíčová slova
• Chlorophyll, HLIPs, HliC, Raman spectroscopy, Synechocystis, β-Carotene,
• MeSH
• bakteriální proteiny chemie   genetika   izolace a purifikace   metabolismus   MeSH
• beta-karoten metabolismus   MeSH
• chlorofyl metabolismus   MeSH
• multimerizace proteinu MeSH
• Ramanova spektroskopie MeSH
• rekombinantní proteiny genetika   izolace a purifikace   metabolismus   MeSH
• světlosběrné proteinové komplexy genetika   metabolismus   MeSH
• Synechocystis genetika   metabolismus   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• bakteriální proteiny MeSH
• beta-karoten MeSH
• chlorofyl MeSH
• high light-inducible protein, cyanobacteria MeSH Prohlížeč
• rekombinantní proteiny MeSH
• světlosběrné proteinové komplexy MeSH

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 was 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.

• Klíčová slova
• Cyanobacteria, Lipid remodeling, Lipid-carotenoid-protein interactions, Photoinhibition, Temperature stress, Xanthophylls,
• MeSH
• beta-karoten metabolismus   účinky záření   MeSH
• buněčná membrána genetika   metabolismus   účinky záření   ultrastruktura   MeSH
• časové faktory MeSH
• fenotyp MeSH
• fotosyntéza genetika   účinky záření   MeSH
• fotosystém I (proteinový komplex) genetika   metabolismus   účinky záření   MeSH
• fyziologická adaptace MeSH
• fyziologický stres * MeSH
• genotyp MeSH
• membránové lipidy metabolismus   účinky záření   MeSH
• metabolismus lipidů genetika   účinky záření   MeSH
• mutace MeSH
• světlo * MeSH
• Synechocystis genetika   metabolismus   účinky záření   ultrastruktura   MeSH
• teplota * MeSH
• tylakoidy metabolismus   účinky záření   MeSH
• xanthofyly genetika   metabolismus   účinky záření   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• beta-karoten MeSH
• fotosystém I (proteinový komplex) MeSH
• membránové lipidy MeSH
• xanthofyly MeSH

Differential kinetic absorption spectra were measured during actinic illumination of photosystem II reaction centres and core complexes in the presence of electron acceptors silicomolybdate and ferricyanide. The spectra of samples with ferricyanide differ from those with both ferricyanide and silicomolybdate. Near-infrared spectra show temporary beta-carotene and peripheral chlorophyll oxidation during room temperature actinic illumination. Peripheral chlorophyll is photooxidized even after decay of beta-carotene oxidation activity and significant reduction of beta-carotene content in both reaction centres and photosystem II core complexes. Besides, new carotenoid cation is observed after about 1 s of actinic illumination in the reaction centres when silicomolybdate is present. Similar result was observed in PSII core complexes. HPLC analyses of illuminated reaction centres reveal several novel carotenoids, whereas no new carotenoid species were observed in HPLC of illuminated core complexes. Our data support the proposal that pigments of inner antenna are a sink of cations originating in the photosystem II reaction centre.

• MeSH
• beta-karoten metabolismus   MeSH
• chlorofyl metabolismus   MeSH
• ferrikyanidy metabolismus   MeSH
• fotosyntéza MeSH
• fotosystém II (proteinový komplex) metabolismus   MeSH
• hrách setý MeSH
• molybden metabolismus   MeSH
• oxidace-redukce MeSH
• sloučeniny křemíku metabolismus   MeSH
• světlo MeSH
• teplota MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• beta-karoten MeSH
• chlorofyl MeSH
• ferrikyanidy MeSH
• fotosystém II (proteinový komplex) MeSH
• hexacyanoferrate III MeSH Prohlížeč
• molybden MeSH
• silicomolybdate MeSH Prohlížeč
• sloučeniny křemíku MeSH

Light-dependent conversion of violaxanthin to zeaxanthin, the so-called xanthophyll cycle, was shown to serve as a major, short-term light acclimation mechanism in higher plants. The role of xanthophylls in thermal dissipation of surplus excitation energy was deduced from the linear relationship between zeaxanthin formation and the magnitude of non-photochemical quenching. Unlike in higher plants, the role of the xanthophyll cycle in green algae (Chlorophyta) is ambiguous, since its contribution to energy dissipation can significantly vary among species. Here, we have studied the role of the xanthophyll cycle in the adaptation of several species of green algae (Chlorella, Scenedesmus, Haematococcus, Chlorococcum, Spongiochloris) to high irradiance. The xanthophyll cycle has been found functional in all tested organisms; however its contribution to non-photochemical quenching is not as significant as in higher plants. This conclusion is supported by three facts: (i) in green algae the content of zeaxanthin normalized per chlorophyll was significantly lower than that reported from higher plants, (ii) antheraxanthin + zeaxanthin content displayed different diel kinetics from NPQ and (iii) in green algae there was no such linear relationship between NPQ and Ax + Zx, as found in higher plants. We assume that microalgae rely on other dissipation mechanism(s), which operate along with xanthophyll cycle-dependent quenching.

• MeSH
• aklimatizace účinky záření   MeSH
• beta-karoten analogy a deriváty   metabolismus   MeSH
• chlorofyl metabolismus   MeSH
• Chlorophyta fyziologie   účinky záření   MeSH
• fotosyntetická reakční centra (proteinové komplexy) fyziologie   účinky záření   MeSH
• fotosyntéza fyziologie   účinky záření   MeSH
• světlo MeSH
• teplota MeSH
• xanthofyly metabolismus   MeSH
• zeaxanthiny MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antheraxanthin MeSH Prohlížeč
• beta-karoten MeSH
• chlorofyl MeSH
• fotosyntetická reakční centra (proteinové komplexy) MeSH
• xanthofyly MeSH
• zeaxanthiny MeSH

The effect of high light on spatial distribution of chlorophyll (Chl) fluorescence parameters over a lichen thallus (Umbilicaria antarctica) was investigated by imaging of Chl fluorescence parameters before and after exposure to high light (1500 micro mol m (-2) s (-1), 30 min at 5 degrees C). False colour images of F (V)/F (M) and Phi (II) distribution, taken over thallus with 0.1 mm (2) resolution, showed that maximum F (V)/F (M) and Phi (II) values were located close to the thallus centre. Minimum values were typical for thallus margins. After exposure to high light, a differential response of F (V)/F (M) and Phi (II) was found. The marginal thallus part exhibited a loss of photosynthetic activity, manifested as a lack of Chl fluorescence signal, and close-to-centre parts showed a different extent of F (V)/F (M) and Phi (II) decrease. Subsequent recovery in the dark led to a gradual return of F (V)/F (M) and Phi (II) to their initial values. Fast (30 min) and slow (1 - 22 h) phase of recovery were distinguished, suggesting a sufficient capacity of photoprotective mechanisms in U. antarctica to cope with low-temperature photoinhibition. Glutathione and xanthophyll cycle pigments were analyzed by HPLC. High light led to an increase in oxidized glutathione (GSSG), and a conversion of violaxanthin to zeaxanthin, expressed as their de-epoxidation state (DEPS). The responses of GSSG and DEPS were reversible during subsequent recovery in the dark. GSSG and DEPS were highly correlated to non-photochemical quenching (NPQ), indicating involvement of these antioxidants in the resistance of U. antarctica to high-light stress. Heterogeneity of Chl fluorescence parameters over the thallus and differential response to high light are discussed in relation to thallus anatomy and intrathalline distribution of the symbiotic alga Trebouxia sp.

• MeSH
• aklimatizace účinky záření   MeSH
• beta-karoten analogy a deriváty   metabolismus   MeSH
• chlorofyl metabolismus   MeSH
• Eukaryota růst a vývoj   MeSH
• fluorometrie metody   MeSH
• fotosyntetická reakční centra (proteinové komplexy) fyziologie   účinky záření   MeSH
• glutathion metabolismus   MeSH
• lišejníky cytologie   fyziologie   účinky záření   MeSH
• mikroskopie MeSH
• nízká teplota MeSH
• světlo MeSH
• symbióza MeSH
• xanthofyly MeSH
• zeaxanthiny MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• beta-karoten MeSH
• chlorofyl MeSH
• fotosyntetická reakční centra (proteinové komplexy) MeSH
• glutathion MeSH
• xanthofyly MeSH
• zeaxanthiny MeSH