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. 2012 Sep 25;109(39):15757-62.
doi: 10.1073/pnas.1211017109. Epub 2012 Aug 13.

A kinetic model of rapidly reversible nonphotochemical quenching

Julia Zaks  1 , Kapil Amarnath, David M Kramer, Krishna K Niyogi, Graham R Fleming
Affiliations

A kinetic model of rapidly reversible nonphotochemical quenching

Julia Zaks et al. Proc Natl Acad Sci U S A. .

Abstract

Oxygen-evolving photosynthetic organisms possess nonphotochemical quenching (NPQ) pathways that protect against photo-induced damage. The majority of NPQ in plants is regulated on a rapid timescale by changes in the pH of the thylakoid lumen. In order to quantify the rapidly reversible component of NPQ, called qE, we developed a mathematical model of pH-dependent quenching of chlorophyll excitations in Photosystem II. Our expression for qE depends on the protonation of PsbS and the deepoxidation of violaxanthin by violaxanthin deepoxidase. The model is able to simulate the kinetics of qE at low and high light intensities. The simulations suggest that the pH of the lumen, which activates qE, is not itself affected by qE. Our model provides a framework for testing hypothesized qE mechanisms and for assessing the role of qE in improving plant fitness in variable light intensity.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Schematic of components described in the model. For more detailed schematics, see ref. . Nonphotochemical quenching occurs in PSII.
Fig. 2.
Fig. 2.
(A) Schematic of the system that activates and is affected by qE. qE regulates the concentrations of excited chlorophylls in the PSII antenna, which is directly affected by the light intensity. The ability of the photosynthetic electron transfer (the “plant”) to use the energy contained in the excited chlorophylls (“input”, green box) determines the requirement for qE. We consider qE to be the “controller” (orange box) that is triggered by the lumen pH (light blue box). The lumen pH is a component of the pmf driving ATP synthesis. (B) Modeled pathways and rates for quenching of chlorophyll fluorescence (green box) in PSII. Quenching by qE is shown in orange. (C) Components involved in the activation of qE (orange box) are a protonated PsbS protein and a deepoxodized xanthophyll. Both of these components are triggered by the lumen pH (cyan box). The numerical values of key parameters for qE is given in Table S2.
Fig. 3.
Fig. 3.
(A) Pulse amplitude modulation (PAM) traces of wild type and npq4 Arabidopsis thaliana leaves at 1,000 μmol photons/m2/s. (B) NPQ in wild type and mutant, calculated using the formula formula image. (C) Difference in NPQ between wild type and npq4, which is a measure of qE. The black bar at the top of each figure indicates times when the plant is darkened, and the white bar indicates actinic light illumination.
Fig. 4.
Fig. 4.
Measured (squares) and simulated (dashed lines) qE for input light intensities of (A) 100 and (B) 1,000 μmol photons/m2s. The experimental trace in B is the same as in Fig. 3C. Other than light intensity, all parameters for the simulation are the same. qE is taken to be the difference in NPQ between the wild type and npq4 mutant in order to subtract the baseline of slowly reversible NPQ. Both measured and simulated NPQ values are determined from the PAM traces shown in Fig. S1. The black bar at the top indicates times when the plant is darkened, and the white bar indicates actinic light illumination.
Fig. 5.
Fig. 5.
Effect of qE on pH of thylakoid lumen at (A) 100 and (B) 1,000 μmol photons/m2/s. For the values for qE activation given in Table S2, the model predicts that qE has minimal effect on the pH of the lumen, suggesting that qE quenching does not lead to a signification reduction in linear electron flow. This result indicates that qE only quenches excitations that do not contribute to pmf and ATP synthesis, suggesting that qE does not waste useful energy. The black bar at the top indicates times when the plant is darkened, and the white bar indicates actinic light illumination.
Fig. 6.
Fig. 6.
Effect of varying the rate kQ on the lumen pH at 1,000 μmol photons/m2/s. For quenching rates of 3 × 109 and 1 × 1010, corresponding to timescales for quenching of 300 ps and 100 ps, the lumen pH is essentially unaffected by qE (see also Fig. 5B). At faster rates of quenching, the feedback quenching of qE is strong enough that it affects the value of the lumen pH, which is the trigger for qE.
See this image and copyright information in PMC

Comment in

  • Modeling the protection of photosynthesis.
    Harbinson J. Harbinson J. Proc Natl Acad Sci U S A. 2012 Sep 25;109(39):15533-4. doi: 10.1073/pnas.1213195109. Epub 2012 Sep 18. Proc Natl Acad Sci U S A. 2012. PMID: 22991475 Free PMC article. No abstract available.

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References

    1. Melis A. Photosystem-II damage and repair cycle in chloroplasts: What modulates the rate of photodamage in vivo? Trends Plant Sci. 1999;4:130–135. - PubMed
    1. Kulheim C, Agren J, Jansson S. Rapid regulation of light harvesting and plant fitness in the field. Science. 2002;297:91–93. - PubMed
    1. Müller P, Li X-P, Niyogi KK. Non-photochemical quenching. A response to excess light energy. Plant Physiol. 2001;125:1558–1566. - PMC - PubMed
    1. Li X-P, Muller-Moule P, Gilmore AM, Niyogi KK. PsbS-dependent enhancement of feedback de-excitation protects photosystem II from photoinhibition. Proc Natl Acad Sci USA. 2002;99:15222–15227. - PMC - PubMed
    1. de Bianchi S, Ballottari M, DallOsto L, Bassi R. Regulation of plant light harvesting by thermal dissipation of excess energy. Biochem Soc Trans. 2010;38:651–660. - PubMed

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