Biochemistry of the violaxanthin cycle in higher plants

Yamamoto, Harry Y.

doi:10.1351/pac197951030639

Cited by 352 publications

(113 citation statements)

References 26 publications

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“…The extent of qE is generally correlated with changes in the carotenoid composition of the LHCII antenna. Specifically, the light-induced ⌬pH activates a lumen-located deepoxidase that becomes membrane-bound and converts violaxanthin into zeaxanthin at low pH levels (24,25).…”

Section: Transient Fluorescence Quenching Is Not Related To Carotenoidmentioning

confidence: 99%

A zeaxanthin-independent nonphotochemical quenching mechanism localized in the photosystem II core complex

Finazzi

Johnson

Dall’Osto

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

131

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Illumination of dark-adapted barley plants with low light transiently induced a large nonphotochemical quenching of chlorophyll fluorescence. This reaction was identified as a form of high-energy-state quenching. Its appearance was not accompanied by zeaxanthin synthesis but was associated with a reversible inactivation of a fraction of photosystem II (PSII) centers. Both the fluorescence quenching and PSII inactivation relaxed in parallel with the activation of the Calvin cycle. We interpret the induction of this phenomenon as due to the generation of a quenched state in the PSII core complex. This reaction is probably caused by the transient overacidification of the thylakoid lumen, whereas its dissipation results from the relaxation of both the pH gradient across the thylakoid membrane and redox pressure upon activation of carbon fixation. At saturating light intensities, inactivation of PSII was still observed at the onset of illumination, although its recovery did not result in dissipation of high-energy quenching, which presents typical characteristics of an antenna-associated quenching at steady state. Reaction-center quenching seems therefore to be a common transient feature during illumination, being replaced by other phenomena (photochemical or antenna quenching and photoinhibition), depending on the balance between light and carbon fixation fluxes

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Section: Transient Fluorescence Quenching Is Not Related To Carotenoidmentioning

confidence: 99%

A zeaxanthin-independent nonphotochemical quenching mechanism localized in the photosystem II core complex

Finazzi

Johnson

Dall’Osto

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

131

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“…3B shows that there were very large changes in the relative concentrations of the xanthophyll cycle pigments violaxanthin (V), antheraxanthin (A), and zeaxanthin (Z); note that like the Chl levels the xanthophyll pool size [V ϩ A ϩ Z] remained constant during deacclimation. The epoxide-free zeaxanthin (Z) and mono-epoxide A molecules form via reversible de-epoxidation and epoxidation of the di-epoxide violaxanthin (V) in the xanthophyll cycle (8). The de-epoxidation reaction is associated with excess light conditions that acidify the chloroplast thylakoid lumen and activate the luminal violaxanthin de-epoxidase enzyme.…”

Section: Resultsmentioning

confidence: 99%

“…Although the spectral and kinetic changes during winter acclimation are induced by excess light and chloroplast intrathylakoid acidification (6, 7), the slowly reversing changes during deacclimation are sustained largely independently of intrathylakoid acidification. The enhanced thermal dissipation during winter acclimation correlates with a massive build-up of the same xanthophyll cycle pigments (8) that are most widely known to correlate with PSII thermal dissipation when there is intrathylakoid acidification (6,7,(9)(10)(11)(12). The primary steps of winter deacclimation correlate with a slow, stoichiometric conversion of epoxide-free xanthophyll cycle pigments to epoxide-containing forms without a change in the total leaf xanthophyll cycle or Chl pools.…”

mentioning

confidence: 99%

Protection and storage of chlorophyll in overwintering evergreens

Gilmore

Ball

2000

Proc. Natl. Acad. Sci. U.S.A.

163

126

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How evergreen species store and protect chlorophyll during exposure to high light in winter remains unexplained. This study reveals that the evergreen snow gum (Eucalyptus pauciflora Sieb. ex Spreng.) stores and protects its chlorophylls by forming special complexes that are unique to the winter-acclimated state. Our in vivo spectral and kinetic characterizations reveal a prominent component of the chlorophyll fluorescence spectrum around 715 nm at 77 K. This band coincides structurally with a loss of chlorophyll and an increase in energy-dissipating carotenoids. Functionally, the band coincides with an increased capacity to dissipate excess light energy, absorbed by the chlorophylls, as heat without intrathylakoid acidification. The increased heat dissipation helps protect the chlorophylls from photo-oxidative bleaching and thereby facilitates rapid recovery of photosynthesis in spring.U nder favorable light and temperatures, most plants operate with a high quantum efficiency (better than 80%) to use absorbed photons to catalyze photosynthetic electron transport, ATP synthesis, and carbon fixation. However, photosynthetic efficiency in leaves of evergreens such as holly (1), pines (2, 3), and snow gum (4, 5), naturally declines to very low levels during winter and remains inhibited until conditions become favorable for growth in spring. These evergreen species maintain significant levels of chlorophyll (Chl), which exists in a state that has not been characterized previously with respect to the Chl electronic-excited state or fluorescence lifetimes, or the Chl excitation vs. emission spectra of photosystems I and II (PSI and PSII). This characterization is essential for understanding mechanisms of Chl protection and storage in overwintering evergreens.We report that winter acclimation of the photosynthetic apparatus in the snow gum Eucalyptus pauciflora Sieb. ex Spreng results in a large loss of Chl in the leaf and profound changes in the Chl a fluorescence emission spectrum at 77 K in the form of a broad emission maximum featured in the 715-nm region. Concomitantly there is a significant increase in the amplitudes of room temperature PSII Chl a fluorescence emission components with subnanosecond fluorescence lifetimes. The subnanosecond lifetime components indicate a more rapid rate of thermal excitation dissipation compared to the main 2.5-ns components (6) that typify the deacclimated state. Although the spectral and kinetic changes during winter acclimation are induced by excess light and chloroplast intrathylakoid acidification (6, 7), the slowly reversing changes during deacclimation are sustained largely independently of intrathylakoid acidification. The enhanced thermal dissipation during winter acclimation correlates with a massive build-up of the same xanthophyll cycle pigments (8) that are most widely known to correlate with PSII thermal dissipation when there is intrathylakoid acidification (6,7,(9)(10)(11)(12). The primary steps of winter deacclimation correlate with a slow, stoichiometric conversi...

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“…The binding of Z or A is then suggested to cause a switching of PSII units to a state with an increased rate constant of heat dissipation (16)(17)(18), leading to the quenching of Chl a fluorescence (a "dimmer switch" effect), as measured by the pulse amplitude modulation fluorometer (Figures 3 and 4) or by multifrequency phase fluorometry ( Figures 5 and 6). We note that the sulfhydryl reagent dithiothreitol (DTT) inhibits deepoxidation (34) without inhibiting either the light-driven or ATPase-mediated proton pumps. By varying the concentration of DTT, we were able to obtain different concentrations of Z and A (see Figure 1).…”

Section: Discussionmentioning

confidence: 99%

Quantitative Analysis of the Effects of Intrathylakoid pH and Xanthophyll Cycle Pigments on Chlorophyll a Fluorescence Lifetime Distributions and Intensity in Thylakoids

et al. 1998

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The xanthophyll cycle-dependent dissipation of excitation energy in higher plants is one of the most important regulatory and photoprotective mechanisms in photosynthesis. Using parallel timeresolved and pulse-amplitude modulation fluorometry, we studied the influence of the intrathylakoid pH and the xanthophyll cycle carotenoids on the PSII chlorophyll (Chl) a fluorescence yield in thylakoids of Arabidopsis, spinach, and barley. Increases in concentrations of dithiothreitol in thylakoids, which have a trans-thylakoid membrane pH gradient and are known to have decreased conversion of violaxanthin (V) to zeaxanthin (Z), lead to (1) decreases in the fractional intensity of the ∼0.5 ns Chl a fluorescence lifetime (τ) distribution component and simultaneous increases in a 1.6-1.8 ns fluorescence component and (2) increases in the maximal fluorescence intensity. These effects disappear when the pH gradient is eliminated by the addition of nigericin. To quantitatively explain these results, we present a new mathematical model that describes the simultaneous effects of the chloroplast trans-thylakoid membrane pH gradient and xanthophyll cycle pigments on the PSII Chl a fluorescence τ distributions and intensity. The model assumes that (1) there exists a specific binding site for Z (or antheraxanthin, A) among or in an inner antenna complex (primarily CP29), (2) this binding site is activated by a low intrathylakoid pH (pK ≈4.5) that increases the affinity for Z (or A), (3) about one Z or A molecule binds to the activated site, and (4) this binding effectively "switches" the fluorescence τ distribution of the PSII unit to a state with a decreased fluorescence τ and emission intensity (a "dimmer switch" concept). This binding is suggested to cause the formation of an exciton trap with a rapid intrinsic rate constant of heat dissipation. Statistical analysis of the data yields an equilibrium association constant, K a , that ranges from 0.7 to 3.4 per PSII for the protonated/activated binding site for Z (or A). The model explains (1) the relative fraction of the ∼0.5 ns fluorescence component as a function of both Z and A concentration and intrathylakoid pH, (2) Interest in the molecular mechanisms used by higher plants to adapt and acclimate to light levels in excess of that used in photosynthesis has recently increased. One possible photoprotective mechanism involves xanthophyll cycledependent thermal dissipation of excess absorbed light energy in the light-harvesting complexes of photosystem II (PSII) (1-8). Light harvesting in the PSII antenna and the xanthophyll cycle-dependent heat dissipation mechanism are related to the structure and organization of the PSII pigmentproteins. The PSII holochrome is composed of (a) the PSII core that includes chlorophyll proteins CP43 and CP47 and reaction center proteins D1, D2, and cytochrome b 559 , (b) the minor inner antenna, labeled as CP24, CP26, and CP29, and (c) the major peripheral antenna complex that includes trimeric assemblies of the light-harvesting complex ...

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Biochemistry of the violaxanthin cycle in higher plants

Cited by 352 publications

References 26 publications

A zeaxanthin-independent nonphotochemical quenching mechanism localized in the photosystem II core complex

A zeaxanthin-independent nonphotochemical quenching mechanism localized in the photosystem II core complex

Protection and storage of chlorophyll in overwintering evergreens

Quantitative Analysis of the Effects of Intrathylakoid pH and Xanthophyll Cycle Pigments on Chlorophyll a Fluorescence Lifetime Distributions and Intensity in Thylakoids

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