The xanthophyll cycle, its regulation and components

Abstract

1997. The xanthophyll cycle, its regulation and components. -Physiol. Plant. 100: 806-816.During the last few years much interest has been focused on the photoprotective role of zeaxanthin. In excessive light zeaxanthin is rapidly formed in the xanthophyll cycle from violaxanthin, via the intermediate antheraxanthin, a reaction reversed in the dark. The role of zeaxanthin and the xanthophyll cycle in photoprotection, is based on fluorescence quenching measurements, and in many studies a good correlation to the amount of zeaxanthin (and antheraxanthin) has been found. Other suggested roles for the xanthophylls involve, protection against oxidative stress of lipids, participation in the blue light response, modulation of the membrane fluidity and regulation of abscisic acid synthesis. The enzyme violaxanthin de-epoxidase has recently been purified from spinach and lettuce as a 43-kDa protein. It was found as 1 molecule per 20-100 electron-transport chains. The gene has been cloned and sequenced from Lactuca sativa, Nicotiana tabacum and Arabidopsis thaliana. The transit peptide was characteristic of nuclear-encoded and lumen-localized proteins. The activity of violaxanthin de-epoxidase is controlled by the lumen pH. Thus, below pH 6.6 the enzyme binds to the thylakoid membrane. In addition ascorbate becomes protonated to ascorbic acid (pKa = 4.2) the true substrate (K^ = 0.1 mM) for the violaxanthin de-epoxidase. We present arguments for an ascorbate transporter in the thylakoid membrane. The enzyme zeaxanthin epoxidase requires FAD as a cofactor and appears to use ferredoxin rather than NADPH as a reductant. The zeaxanthin epoxidase has not been isolated but the gene has been sequenced and a functional protein of 72.5 kDa has been expressed. The xanthophyll cycle pigments are almost evenly distributed in the thylakoid membrane and at least part of the pigments appears to be free in the lipid matrix where we conclude that the conversion by violaxanthin de-epoxidase occurs.

Effects of heavy metals and light levels on the biosynthesis of carotenoids and fatty acids in the macroalgae Gracilaria tenuistipitata (var. liui Zhang & Xia)

“…Under certain stressful conditions, including high light incidence, plants can dissipate the excess energy in photosynthesis via a cyclic reaction involving two successive de-epoxidations of violaxanthin to zeaxanthin, with antheraxanthin as an intermediate (DemmigAdams & Adams, 1996;Eskling et al, 1997;Havaux & Niyogi, 1999). As mentioned above, low and high light irradiances (L-and L+: 100 and 1000 µmol.photons.m -2 .s -1 , respectively) had no effect on the biosynthesis of fatty acids in G. tenuistipitata.…”

Potential of Photochemical Reflectance Index for Indicating Photochemistry and Light Use Efficiency in Leaves of European Beech and Norway Spruce Trees

“…Decreased diurnal magnitude of the R 531 response under HI-LT ( Figure 7E,F) can be attributed to maintaining sustained NPQ. The development of NPQ in response to low temperature is typically correlated with the retention of antheraxanthin and zeaxanthin [40] under conditions when generation of the electrochemical potential on thylakoid membrane (∆pH) or the enzymatic de-epoxidation reaction necessary for optimal functioning of the NPQ are very slow [41,42]. Although most of the published works report increased overnight zeaxanthin levels under freezing temperatures [43], the temperature around 12 • C also seems to produce substantial overnight zeaxanthin retention in studied tree species.…”

Xanthophyll Cycle Pigment Localization and Dynamics during Exposure to Low Temperatures and Light Stress inVinca major1

“…The xanthophyll cycle pigments Z and A are formed from V when light is excessive, and they are involved in a photoprotective process whereby excess absorbed excitation energy is dissipated thermally in the light-harvesting antennae of PSII Eskling et al, 1997;Gilmore, 1997). The retention of Z plus A in photoinhibited leaves often correlates closely with sustained low PSII efficiencies measured as the F v /F m (Adams et al, 1995;Verhoeven et al, 1996;Demmig-Adams et al, 1998, and refs.…”