LHCII Populations in Different Quenching States Are Present in the Thylakoid Membranes in a Ratio that Depends on the Light Conditions

Tian, Lijin; Dinc, Emine; Croce, Roberta

doi:10.1021/acs.jpclett.5b00944

Cited by 40 publications

(46 citation statements)

References 44 publications

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“…5C. These three components are assigned to different LHC populations, where the nature of this heterogeneity has been presented in our previous work (25). Three components are necessary for the fit of the decay kinetics in the Q cells, but they differ in amplitude and lifetime from those of UQ and R. The quenching mainly affects the longest lifetime component, the amplitude of which is reduced by >40% in Q cells compared with UQ cells.…”

Section: Resultsmentioning

confidence: 98%

“…Using a vitamin repressor system, it is possible to completely deplete C. reinhardtii cells of photosystem (PS) I and II core components under normal and high-light conditions (23)(24)(25) (Fig. S1A).…”

Section: Resultsmentioning

confidence: 99%

“…As shown previously, at the beginning of the treatment, the cells contain all the components of the photosynthetic apparatus and grow normally. After vitamin treatment, the photosynthetic apparatus is degraded, starting with the core complexes of PSI and PSII, and after 6 d in normal light and 3 in high light, the thylakoid membrane of these cells contains mainly LHCII (24,25) (Fig. S1B).…”

Section: Resultsmentioning

confidence: 99%

“…The 500-ps component responds to the quenching process as well: the lifetime becomes shorter, from 530 to 390 ps, and the DAS shows less excitation energy transfer character in the Q cells. The DAS with a 3-ns lifetime has positive amplitude with maximum at 710 nm and represents the fluorescence decay of the red-most pigments, most likely associated with the LHCA proteins (25). At 77 K, these red pigments receive most of the energy, acting as energy traps, indicating that they are well connected to the LHCII.…”

Section: Spectra (Das) Are Shown Inmentioning

confidence: 99%

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LHCSR1 induces a fast and reversible pH-dependent fluorescence quenching in LHCII in Chlamydomonas reinhardtii cells

Dinc¹,

Tian²,

Roy³

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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To avoid photodamage, photosynthetic organisms are able to thermally dissipate the energy absorbed in excess in a process known as nonphotochemical quenching (NPQ). Although NPQ has been studied extensively, the major players and the mechanism of quenching remain debated. This is a result of the difficulty in extracting molecular information from in vivo experiments and the absence of a validation system for in vitro experiments. Here, we have created a minimal cell of the green alga Chlamydomonas reinhardtii that is able to undergo NPQ. We show that LHCII, the main light harvesting complex of algae, cannot switch to a quenched conformation in response to pH changes by itself. Instead, a small amount of the protein LHCSR1 (light-harvesting complex stress related 1) is able to induce a large, fast, and reversible pH-dependent quenching in an LHCII-containing membrane. These results strongly suggest that LHCSR1 acts as pH sensor and that it modulates the excited state lifetimes of a large array of LHCII, also explaining the NPQ observed in the LHCSR3-less mutant. The possible quenching mechanisms are discussed.photosynthesis | light-harvesting | nonphotochemical quenching | green algae | thylakoid membranes P hotosynthetic organisms get their energy from light and have developed a series of mechanisms to respond to the changes in light intensity that occur in their natural environment (1, 2). This is particularly important in high-light conditions, as the energy absorbed in excess can induce photodamage, eventually leading to the death of the organism. Photosynthetic organisms are equipped with many pigment-protein complexes, most of which in plants and green algae are members of the light-harvesting complex (Lhc) multigenic family (3). These complexes maximize light absorption in low light, but can easily become overexcited in high light (4), when a large part of the absorbed light cannot be used for charge separation in the reaction centers of the photosystems. Especially when the changes in light intensity are very fast, and thus protein degradation is not an option, photoprotective mechanisms need to be switched on to avoid the formation of singlet oxygen. The most rapid response to high light intensity is the dissipation of a large part of the absorbed energy as heat in a series of processes known as nonphotochemical quenching (NPQ) (1,5,6).The general idea is that the LHCs can switch between a lightharvesting conformation, characterized by a long excited-state lifetime, and a quenched (Q) conformation that shows a shorter lifetime because of the presence of competing de-excitation processes (7). How this switch is induced and the nature of these de-excitation processes is a matter of debate. It is known that NPQ is triggered by low luminal pH, which is a signal for the overexcitation of the membrane; this activates the quenching processes (5, 8), which involves the proteins PsbS (in plants and mosses) (9, 10) and/or lightharvesting complex stress related (LHCSR) (in green algae, mosses, and diatoms) (10-12)....

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Spectra (Das) Are Shown Inmentioning

confidence: 99%

See 2 more Smart Citations

LHCSR1 induces a fast and reversible pH-dependent fluorescence quenching in LHCII in Chlamydomonas reinhardtii cells

Dinc¹,

Tian²,

Roy³

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

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“…However, these preparations represent an over-simplified system in a non-native environment. To overcome these problems, several approaches have been put forward: (i) reducing the number of components involved in NPQ in the thylakoid membrane by using mutants lacking photosystems I and II core complexes or blocking the chloroplast translation that leads to membranes enriched in LHCII (15,16) and (ii) studying isolated LHCII in detergent-free environment using nanodisks (17), styrene maleic acid (18), amphipoles (19), or liposomes (20 -22). These methods have revealed that the lifetime of LHCII in the membrane differs substantially from its lifetime in detergent micelles, suggesting that in the natural environment the antennas assume a different and more quenched conformation.…”

mentioning

confidence: 99%

Light-harvesting Complexes (LHCs) Cluster Spontaneously in Membrane Environment Leading to Shortening of Their Excited State Lifetimes

Natali

Gruber

Dietzel

et al. 2016

Journal of Biological Chemistry

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The light reactions of photosynthesis, which include lightharvesting and charge separation, take place in the amphiphilic environment of the thylakoid membrane. The light-harvesting complex II (LHCII) is the main responsible for light absorption in plants and green algae and is involved in photoprotective mechanisms that regulate the amount of excited states in the membrane. The dual function of LHCII has been extensively studied in detergent micelles, but recent results have indicated that the properties of this complex differ in a lipid environment. In this work we checked these suggestions by studying LHCII in liposomes. By combining bulk and single molecule measurements, we monitored the fluorescence characteristics of liposomes containing single complexes up to densely packed proteoliposomes. We show that the natural lipid environment per se does not alter the properties of LHCII, which for single complexes remain very similar to that in detergent. However, we show that LHCII has the strong tendency to cluster in the membrane and that protein interactions and the extent of crowding modulate the lifetimes of the excited state in the membrane. Finally, the presence of LHCII monomers at low concentrations of complexes per liposome is discussed.Photosynthetic organisms evolved the capacity to harvest the energy of solar radiation and store it into chemical compounds. In vascular plants and green algae, sunlight is absorbed by a series of membrane proteins called light-harvesting complexes (LHC).3 The most abundant of these pigment-protein complexes is LHCII. The LHCs have a dual function; in low light conditions they absorb solar energy and efficiently transfer the excitation energy to the reaction center, and in high light they additionally play a role in photoprotection by dissipating the energy absorbed in excess as heat (1, 2). This last process called non-photochemical quenching (NPQ) leads to a decrease of the excited state lifetime of chlorophyll a (Chl a), limiting the possibility of Chl triplet formation and thus the production of singlet oxygen (3). The fast, on the timescale of seconds, and fully reversible part of NPQ is called qE. This mechanism is triggered by the acidification of the lumenal space of the thylakoids, which activates PsbS (4) and LhcSR (5), the proteins responsible for NPQ in plants and green algae, respectively, and the violaxanthin de-epoxidase, which converts violaxanthin into zeaxanthin (for reviews, see Refs. 6 and 7). Although the precise molecular mechanism of quenching has not been fully elucidated yet, a prominent idea discussed in literature is that NPQ is regulated via conformational changes of LHCII. Those changes could be correlated to, or even caused by, LHCII aggregation (8, 9). It was observed that low pH and zeaxanthin, both occurring in high light, enhance LHCII aggregation (10). Aggregation of LHCII in vitro is accompanied by a decrease of the Chl a fluorescence yield, indicating an increased rate of energy dissipation (9, 11). The generation of new quenching sit...

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Long-term survival of Chlamydomonas reinhardtii during conditional senescence

Damoo

Durnford

2021

Arch Microbiol

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LHCII Populations in Different Quenching States Are Present in the Thylakoid Membranes in a Ratio that Depends on the Light Conditions

Cited by 40 publications

References 44 publications

LHCSR1 induces a fast and reversible pH-dependent fluorescence quenching in LHCII in Chlamydomonas reinhardtii cells

LHCSR1 induces a fast and reversible pH-dependent fluorescence quenching in LHCII in Chlamydomonas reinhardtii cells

Light-harvesting Complexes (LHCs) Cluster Spontaneously in Membrane Environment Leading to Shortening of Their Excited State Lifetimes

Long-term survival of Chlamydomonas reinhardtii during conditional senescence

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