Photosynthesis Research

, Volume 127, Issue 2, pp 219–235

Energy dissipation pathways in Photosystem 2 of the diatom, Phaeodactylum tricornutum, under high-light conditions

Original Article

DOI: 10.1007/s11120-015-0180-3

Cite this article as:
Kuzminov, F.I. & Gorbunov, M.Y. Photosynth Res (2016) 127: 219. doi:10.1007/s11120-015-0180-3

Abstract

To prevent photooxidative damage under supraoptimal light, photosynthetic organisms evolved mechanisms to thermally dissipate excess absorbed energy, known as non-photochemical quenching (NPQ). Here we quantify NPQ-induced alterations in light-harvesting processes and photochemical reactions in Photosystem 2 (PS2) in the pennate diatom Phaeodactylum tricornutum. Using a combination of picosecond lifetime analysis and variable fluorescence technique, we examined the dynamics of NPQ activation upon transition from dark to high light. Our analysis revealed that NPQ activation starts with a 2–3-fold increase in the rate constant of non-radiative charge recombination in the reaction center (RC); however, this increase is compensated with a proportional increase in the rate constant of back reactions. The resulting alterations in photochemical processes in PS2 RC do not contribute directly to quenching of antenna excitons by the RC, but favor non-radiative dissipation pathways within the RC, reducing the yields of spin conversion of the RC chlorophyll to the triplet state. The NPQ-induced changes in the RC are followed by a gradual ~ 2.5-fold increase in the yields of thermal dissipation in light-harvesting complexes. Our data suggest that thermal dissipation in light-harvesting complexes is the major sink for NPQ; RCs are not directly involved in the NPQ process, but could contribute to photoprotection via reduction in the probability of 3Chl formation.

Keywords

Non-photochemical quenching Diatoms Photosystem 2 Reaction center Light-harvesting complex Photosynthetic energy transfer 

Abbreviations

Pt1

Diatom algae Phaeodactylum tricornutum (CCMP 632)

Pt4

Diatom algae Phaeodactylum tricornutum (UTEX 646)

Dd

Diadinoxanthin

Dt

Diatoxanthin

DTT

Dithiothreitol

FIRe

Fluorescence Induction and Relaxation

PS1 (PS2)

Photosystem 1 (photosystem 2)

RC

Reaction center

FCP

Fucoxanthin chlorophyll a/c-binding Protein

Lhcx

Light-harvesting proteins that belong to LI818/Lhcsr protein family and act as modulators of NPQ (Goss and Lepetit 2015)

XC

Xanthophyll cycle

Fo

Minimum yield of fluorescence at open PS2 RC in the dark-adapted cells

FM

Maximum yield of fluorescence at closed PS2 RC in the dark-adapted cells

FV/FM

Maximum PS2 photochemical efficiency in the dark [=(FM − Fo)/FM]

\( F_{\text{M}}^{\text{NPQ}} \)

Maximum yield of fluorescence at closed PS2 RC in cells after exposure to prolonged illumination

\( F_{\text{M}}^{\text{I}} \)

Maximum yield of fluorescence at closed PS2 RC in photoinhibited cells (e.g., with damaged RCs)

NPQ

Non-photochemical quenching parameter [\( = (F_{M} - F_{\text{M}}^{\text{NPQ}} )/F_{\text{M}}^{\text{NPQ}} \)]

σPS2

Functional absorption cross section of PS2

P680, P

Primary donor of the PS2 RC

I

Intermediate acceptor of PS2 RC (phaeophytin)

RP

Radical pair

3Chl

Triplet chlorophyll

Supplementary material

11120_2015_180_MOESM1_ESM.docx (317 kb)
Supplementary material 1 (DOCX 317 kb)

Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  1. 1.Environmental Biophysics and Molecular Biology Program, Department of Marine and Coastal SciencesRutgers UniversityNew BrunswickUSA
  2. 2.International Laser CenterM.V. Lomonosov Moscow State UniversityMoscowRussia

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