Dehydroascorbate Reductase Affects Non-photochemical Quenching and Photosynthetic Performance*
- 1 To whom correspondence should be addressed. Tel.: 951-827-7298; Fax: 951-827-4434; E-mail: drgallie{at}citrus.ucr.edu.
Abstract
Ascorbic acid (Asc) is a major antioxidant involved in photoprotection and photosynthetic function in plants. Dehydroascorbate reductase (DHAR) catalyzes the regeneration of Asc from its oxidized state and serves as an important regulator of Asc recycling. In this work, we used a molecular biochemical approach to investigate how the efficiency of Asc recycling affects non-photochemical quenching (NPQ). Suppression of DHAR expression resulted in a lower induction of NPQ that correlated with reductions in chlorophyll and xanthophyll pigments, quantum yield of photosystem II, and CO2 assimilation, whereas the level of reactive oxygen species increased. The quickly reversible component of NPQ decreased and the slowly reversible or irreversible component of NPQ increased following a reduction in DHAR expression. Significant photoinhibition was also observed following exposure to high light. Direct feeding with Asc restored the appropriate induction of NPQ in DHAR-suppressed leaves. In contrast, increasing DHAR expression increased the pool size of xanthophyll and chlorophyll pigments as well as the rate of CO2 assimilation, particularly at high light intensities, whereas the level of reactive oxygen species was reduced. Leaves with increased DHAR expression experienced less photoinhibition than did wild-type plants following exposure to high light. DHAR activity, therefore, can affect the appropriate induction of NPQ and level of photoprotection during exposure to high light.
Footnotes
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↵2 The abbreviations used are: Chl, chlorophyll; Asc, ascorbic acid; DHA, dehydroascorbate; DHAR, dehydroascorbate reductase; NPQ, non-photochemical quenching; ROS, reactive oxygen species; H2O2, hydrogen peroxide; PS, photosystem; qE, pH-dependent fluorescence quenching (or feedback de-excitation); qT, quenching associated with state transition; qI, quenching caused by photoinhibition; MDHA, monodehydroascorbate; Rubisco, ribulose-bisphosphate carboxylase/oxygenase; PFD, photon flux density; ϕPSII, quantum yield of photosystem II; ETR, electron transport rate; LHCP, light-harvesting complex protein; HSP70, heat shock protein 70; eEF1A, eukaryotic elongation factor 1A; QA, primary quinone electron acceptor of PSII; qP, photochemical quenching; NPQf, fast relaxing NPQ; NPQs, slow relaxing NPQ; DOX, DHAR-overexpressing; DKD, DHAR-suppressed; WT, wild-type; TaDHAR, wheat DHAR; NtDHAR, tobacco DHAR; cHSP70, chloroplast-localized HSP70; V, violaxanthin; A, antheraxanthin; Z, zeaxanthin; Fo, minimum fluorescence in the dark-adapted state; Fo′, minimum fluorescence in the light-adapted state; Fm, maximum fluorescence in the dark-adapted state; Fm′, maximum fluorescence in the light-adapted state; Fv, variable fluorescence; Fs, steady state fluorescence yield during actinic illumination; Fs′, steady state fluorescence yield in the light-adapted state.
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↵* This work was supported by United States Department of Agriculture Grant NRICGP 2002-35100-12469 and by the University of California Agricultural Experiment Station. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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The on-line version of this article (available at http://www.jbc.org) contains supplemental Figs. 1–3 and Table 1.
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- Received April 3, 2008.
- Revision received June 4, 2008.
- The American Society for Biochemistry and Molecular Biology, Inc.
