Journal Article

Significance of the Lipid Phase in the Dynamics and Functions of the Xanthophyll Cycle as Revealed by PsbS Overexpression in Tobacco and In-vitro De-epoxidation in Monogalactosyldiacylglycerol Micelles

A. David Hieber, Osamu Kawabata and Harry Y. Yamamoto

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 1, pages 92-102
Published in print January 2004 | ISSN: 0032-0781
Published online January 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pch010
Significance of the Lipid Phase in the Dynamics and Functions of the Xanthophyll Cycle as Revealed by PsbS Overexpression in Tobacco and In-vitro De-epoxidation in Monogalactosyldiacylglycerol Micelles

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The dynamics of the xanthophyll cycle relative to non-photochemical quenching (NPQ) were examined in tobacco plants overexpressing violaxanthin de-epoxidase (VDE), PsbS and PsbS+VDE for effects on NPQ and violaxanthin (V) de-epoxidation over a range of light intensities. Induction of de-epoxidation and NPQ increased in overexpressed VDE and PsbS plants, respectively. Surprisingly, under low light, overexpressing PsbS enhanced de-epoxidation in addition to NPQ. The effect was hypothesized as due to PsbS binding zeaxanthin (Z) or inducing the binding of Z within the quenching complex, thus shifting the equilibrium toward higher de-epoxidation states. Studies in model systems show that Z can stereospecifically inhibit VDE activity against violaxanthin. This effect, observed under conditions of limiting lipid concentration, was interpreted as product feedback inhibition. These results support the hypothesis that the capacity of the thylakoid lipid phase for xanthophylls is limited and modulates xanthophyll-cycle activity, in conjunction with the release of V and binding of Z by pigment-binding proteins. These modulating factors are incorporated into a lipid-matrix model that has elements of a signal transduction system wherein the light-generated protons are the signal, VDE the signal receptor, Z the secondary messenger, the lipid phase the transduction network, and Z-binding proteins the targets.

Keywords: Keywords: Lipid-matrix model — Lipid-capacity — Product inhibition signal-transduction — Violaxanthin de-epoxidase — Zeaxanthin.; Abbreviations: A, antheraxanthin; DES, de-epoxidation state, (A+Z)/(A+Z+V); Lhc, light-harvesting complex; IML, intermittent light; LHCII, light-harvesting complex of PSII; MGDG, monogalactosyldiacylglycerol; NPQ, non-photochemical quenching; PSII, photosystem II; PsbS, S subunit of PSII also known as CP22; qE, energy-dependent quenching; qI, photoinhibitory quenching; qP, photochemical quenching; V, violaxanthin; VDE, violaxanthin de-epoxidase; Z, zeaxanthin; RR-Z, synthetic naturally occurring isomer of zeaxanthin, (3R,3′R)-β-β-carotene-3,3′-diol; SS-Z, synthetic unnatural enantiomer of zeaxanthin, (3S,3′S)-β-β-carotene-3,3′-diol.

Journal Article.  8868 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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