Conformational changes in photosynthetic pigment proteins on thylakoid membranes can lead to fast non-photochemical quenching in cyanobacteria

Zhicong Wang,Jing Dong,Dunhai Li

doi:10.1007/s11427-012-4360-5

Abstract

A high non-photochemical quenching (NPQ) appeared below the phase transition temperature when Microcystis aeruginosa PCC7806 cells were exposed to saturated light for a short time. This suggested that a component of NPQ, independent from state transition or photo-inhibition, had been generated in the PSII complex; this was a fast component responding to high intensity light. Glutaraldehyde (GA), commonly used to stabilize membrane protein conformations, resulted in more energy transfer to PSII reaction centers, affecting the energy absorption and dissipation process rather than the transfer process of phycobilisome (PBS). In comparison experiments with and without GA, the rapid light curves (RLCs) and fluorescence induction dynamics of the fast phase showed that excess excitation energy was dissipated by conformational change in the photosynthetic pigment proteins on the thylakoid membrane (PPPTM). Based on deconvolution of NPQ relaxation kinetics, we concluded that the fast quenching component (NPQf) was closely related to PPPTM conformational change, as it accounted for as much as 39.42% of the total NPQ. We hypothesize therefore, that NPQf induced by PPPTM conformation is an important adaptation mechanism for Microcystis blooms under high-intensity light during summer and autumn.

Highlights

A high non-photochemical quenching (NPQ) appeared below the phase transition temperature when Microcystis aeruginosa PCC7806 cells were exposed to saturated light for a short time
This suggested that a component of NPQ, independent from state transition or photo-inhibition, had been generated in the photosystem II (PSII) complex; this was a fast component responding to high intensity light
When rETRmax was plotted with linear regression versus different temperatures, there were two obvious lines of rETRmax and a flex point appeared at about 18°C (Figure 1A)

Summary

Introduction

A high non-photochemical quenching (NPQ) appeared below the phase transition temperature when Microcystis aeruginosa PCC7806 cells were exposed to saturated light for a short time This suggested that a component of NPQ, independent from state transition or photo-inhibition, had been generated in the PSII complex; this was a fast component responding to high intensity light. NPQ can be deconvoluted into three components based on the different relaxation times in dark periods after exposure to high intensity light [7,8,9] These three components of NPQ were found to be (i) a fast quenching component (NPQf), which refers to the ΔpH-dependent process or high-energy state (qE); (ii) a medium quenching component (NPQm), related to the quenching of state transition process (qT); and (iii), a low quenching component (qI), resulting from photo-inhibition of photosynthesis. Gwizdala et al [24] used an in vitro reconstitution system to show that cyanobacteria thermally dissipated excess absorbed energy through interactions between OCP, fluorescence recovery protein (FRP), and PBS

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Discussion

Conclusion