The role of the light harvesting complex and photosystem II in thylakoid stacking in thechlorina-f2 barley mutant

Bassi, Roberto; Hinz, Ursula; Barbato, Roberto

doi:10.1007/bf02907157

Cited by 48 publications

(33 citation statements)

References 26 publications

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“…Treatment with ultraviolet B light apparently brought about general swelling of thylakoid membranes, which, in some cases (emphasized by arrows in the 3-h irradiated samples, but clearly visible also after 6 h), could be considered as partial destacking of the membrane. We interpret this phenomenon as the consequence of the dismantling of a fraction of those PSII cores that are involved in membrane stacking (43)(44)(45). This interpretation is supported by the observation that this phenomenon was even more pronounced when the chlorophyll b-less mutant chlorina f2 was treated in the same way with ultraviolet B light (panels D-F).…”

Section: Figsupporting

confidence: 59%

“…Ultraviolet B degradation of proteins D1 and D2 may be the origin of the partial destacking of granum regions. Accordingly, data from the chlorophyll b-less mutant chlorina f2, where granum stacking is maintained essentially by PSII cores (since LHCII proteins are present only in residual amounts) (20,43), show that the effect of ultraviolet B light on thylakoid ultrastructure is dramatic. In this case, a low number of grana with a smaller number of thylakoids per granum are found after irradiation with ultraviolet B, 2 confirming that damage to PSII can actually affect the stability of the grana.…”

Section: Discussionmentioning

confidence: 99%

“…This interpretation is supported by the observation that this phenomenon was even more pronounced when the chlorophyll b-less mutant chlorina f2 was treated in the same way with ultraviolet B light (panels D-F). In this mutant, stacking of thylakoids is thought to be maintained mainly by PSII (43) and only marginally by residual LHCII (43,44). Thus, in view of this result, we interpret the increase in LHCII observed in the digitonin-derived stroma-exposed membranes of the wild type as the result of more extensive solubilization of membranes, produced by the detergent because of partial destacking linked to PSII degradation rather than to actual lateral migration of antenna proteins.…”

Section: Figmentioning

confidence: 90%

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Ultraviolet B Exposure of Whole Leaves of Barley Affects Structure and Functional Organization of Photosystem II

Barbato

Bergo

Szabó

et al. 2000

Journal of Biological Chemistry

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This study examines the effects of ecologically important levels of ultraviolet B radiation on protein D1 turnover and stability and lateral redistribution of photosystem II. It is shown that ultraviolet B light supported only limited synthesis of protein D1, one of the most important components of photosystem II, whereas it promoted significant degradation of proteins D1 and D2. Furthermore, dephosphorylation of photosystem II subunits was specifically elicited upon exposure to ultraviolet B light. Structural modifications of photosystem II and changes in its lateral distribution between granum membranes and stroma-exposed lamellae were found to be different from those observed after photoinhibition by strong visible light. In particular, more complete dismantling of photosystem II cores was observed. Altogether, the data reported here suggest that ultraviolet B radiation alone fails to activate the photosystem II repair cycle, as hypothesized for visible light. This failure may contribute to the toxic effect of ultraviolet B radiation, which is increasing as a consequence of depletion of stratospheric ozone.An increased level of ultraviolet B radiation (280 -320 nm) reaching the Earth's surface has been observed as a consequence of depletion of stratospheric ozone. This phenomenon, first described over the Antarctic Circle, is now extending significantly even to temperate regions (1). It has been shown that even low levels of ultraviolet B light may harm most biological organisms, land plants being particularly sensitive to this radiation (2, 3). The molecular basis of ultraviolet B-induced damage is not completely understood. Apart from DNA damage (4) and other effects such as activation of genes involved in the phenylpropanoid pathway (5, 6), ultraviolet B light impairs photosynthesis. PSII 1 is the most sensitive protein complex of the photosynthetic electron transfer chain (7-9). Damage to the manganese cluster associated with oxygen-evolving activity (10 -12), redox-active tyrosines (12, 13), P 680 (the primary donor in photosystem II) (14), and bound (15, 16) and unbound (10, 15) plastoquinone molecules has been reported. As a consequence of damage, loss of photosynthesis and degradation of reaction center proteins D1 and D2 occur. Studies carried out using in vitro systems have shown that irradiation with ultraviolet B light brings about a loss of protein D1, paralleled by the appearance of an immunodetectable C-terminal fragment of 20 kDa (17). This fragment is produced by cleavage in the second transmembrane ␣-helix (17) in a reaction depending on the presence of manganese ions bound at the catalytic site(s) of the PSII donor side (10). Degradation of protein D2 upon ultraviolet B exposure occurs both in vitro (18) and in vivo (19), although the appearance of specific degradation fragments of protein D2 has so far been reported only in vitro (18). Since protein cleavage was observed only when the Q A site was at least partially active, a role for the bound quinone in the ultraviolet B-induced degradat...

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Section: Figsupporting

confidence: 59%

Section: Discussionmentioning

confidence: 99%

Section: Figmentioning

confidence: 90%

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Ultraviolet B Exposure of Whole Leaves of Barley Affects Structure and Functional Organization of Photosystem II

Barbato

Bergo

Szabó

et al. 2000

Journal of Biological Chemistry

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“…The anomalous in vivo PS II £uorescence lifetimes in clo f 2 clearly are physically related to the well-known Mg 2+ e¡ects on isolated clo f 2 thylakoids, with respect to stacking and PS II versus PS I emission (Bassi et al 1985). Isolated clo f 2 thylakoids, compared to the wt and clo f104, are quite labile with respect to stacking and require high Mg 2+ and chelating agents to induce and retain stacking in vitro.…”

Section: Discussionmentioning

confidence: 84%

Global spectral–kinetic analysis of room temperature chlorophyll a fluorescence from light-harvesting antenna mutants of barley

Gilmore

Itoh

Govindjee

2000

Phil. Trans. R. Soc. Lond. B

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This study presents a novel measurement, and simulation, of the time-resolved room temperature chlorophyll a £uorescence emission spectra from leaves of the barley wild-type and chlorophyll-b-de¢cient chlorina (clo) f 2 and f104 mutants. The primary data were collected with a streak-camera-based picosecond-pulsed £uorometer that simultaneously records the spectral distribution and time dependence of the £uorescence decay. A new global spectral-kinetic analysis programme method, termed the double convolution integral (DCI) method, was developed to convolve the exciting laser pulse shape with a multimodal-distributed decay pro¢le function that is again convolved with the spectral emission band amplitude functions. We report several key results obtained by the simultaneous spectral-kinetic acquisition and DCI methods. First, under conditions of dark-level £uorescence, when photosystem II (PS II) photochemistry is at a maximum at room temperature, both the clo f 2 and clo f104 mutants exhibit very similar PS II spectral-decay contours as the wild-type (wt), with the main band centred around 685 nm. Second, dark-level £uorescence is strongly in£uenced beyond 700 nm by broad emission bands from PS I, and its associated antennae proteins, which exhibit much more rapid decay kinetics and strong integrated amplitudes. In particular a 705^720 nm band is present in all three samples, with a 710 nm band predominating in the clo f 2 leaves. When the PS II photochemistry becomes inhibited, maximizing the £uorescence yield, both the clo f104 mutant and the wt exhibit lifetime increases for their major distribution modes from the minimal 250^500 ps range to the maximal 1500^2500 ps range for both the 685 nm and 740 nm bands. The clo f 2 mutant, however, exhibits several unique spectral-kinetic properties, attributed to its unique PS I antennae and thylakoid structure, indicating changes in both PS II £uorescence reabsorption and PS II to PS I energy transfer pathways compared to the wt and clo f104. Photoprotective energy dissipation mediated by the xanthophyll cycle pigments and the PsbS protein was uninhibited in the clo f 104 mutant but, as commonly reported in the literature, signi¢cantly inhibited in the clo f 2; the inhibited energy dissipation is partly attributed to its thylakoid structure and PS II to PS I energy transfer properties. It is concluded that it is imperative with steady-state £uorometers, especially for in vivo studies of PS II e¤ciency or photoprotective energy dissipation, to quantify the in£uence of the PS I spectral emission.

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“…Betula pubescens (V ALANNE 1975), Cucumis sativus (PALCZEWSKA et al 1983), Hordeum sp. (WETISTEIN 1958(WETISTEIN , 1961BAsSI et al 1985), Lycopersicon esculentum (BoYNTON 1966), Scindapsus aureus (.ARAus et al 1986), Zea mays (BACHMANN et al 1967;MILLERD et a/. 1969).…”

Section: Introductionunclassified

Genetic analysis and plastid ultrastructure of three chlorophyll lethal mutants in winter rye (Secale cerealeL.)

Gabara

Kubicka²,

Kubicki³

et al. 1991

Caryologia

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The role of the light harvesting complex and photosystem II in thylakoid stacking in thechlorina-f2 barley mutant

Cited by 48 publications

References 26 publications

Ultraviolet B Exposure of Whole Leaves of Barley Affects Structure and Functional Organization of Photosystem II

Ultraviolet B Exposure of Whole Leaves of Barley Affects Structure and Functional Organization of Photosystem II

Global spectral–kinetic analysis of room temperature chlorophyll a fluorescence from light-harvesting antenna mutants of barley

Genetic analysis and plastid ultrastructure of three chlorophyll lethal mutants in winter rye (Secale cerealeL.)

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