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Updated: Jun 7, 2026
10:20
Evaluation of Photosynthetic Behaviors by Simultaneous Measurements of Leaf Reflectance and Chlorophyll Fluorescence Analyses
Published on: August 9, 2019
Mapping the absorption landscape of far-red Photosystem II
Ho Fong Leong1, Giovanni Consoli1, Geoffry A Davis1,2
1Department of Life Sciences, Imperial College, London, UK.
Nature Communications
|June 5, 2026
Summary
Cyanobacteria use far-red light photoacclimation for survival in low-light conditions. This study reveals unique subunits and chlorophyll arrangements in far-red Photosystem II, explaining their adaptation to dim environments.
Area of Science:
- Photosynthesis research
- Cyanobacterial adaptation
- Structural biology
Background:
- Far-red light photoacclimation allows cyanobacteria to survive in low-light environments.
- Far-red Photosystem II incorporates specialized chlorophylls (chlorophyll f and d) for red-shifted light absorption.
Purpose of the Study:
- To comparatively analyze far-red Photosystem II structures in Chroococcidiopsis thermalis PCC 7203 and Calothrix sp. NIES-3974.
- To elucidate the structural basis for far-red light utilization and survival mechanisms in cyanobacteria.
Main Methods:
- Cryo-electron microscopy for structural determination.
- Sequence comparisons and electrostatic potential analyses for chlorophyll site assignment.
- Comparative phylogenetic, structural, and spectroscopic analyses.
Main Results:
- Identified a far-red exclusive subunit, PsbH2', in C. thermalis, crucial for chlorophyll f binding.
- Assigned specific chlorophyll f binding sites and their wavelengths in both species.
- Found PsbH2' is absent in Calothrix, with fewer chlorophyll f sites.
Conclusions:
- The study provides a framework for modeling energy transfer in far-red Photosystem II.
- Identified conserved features enabling cyanobacterial survival under far-red light.
- Structural and spectroscopic data explain the spectral distinctness of red-shifted chlorophylls.
Related Concept Videos
01:22Photosystem II
The multi-protein complex photosystem II (PS II) harvests photons and transfers their energy through its bound pigments to its reaction center, and ultimately to photosystem I (PSI) through the electron transport chain. The pigments responsible for caputirng the light energy in photosystems include chlorophyll a, chlorophyll b, and carotenoids.
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
01:27Photosystem I
Although structurally similar to photosystem II (PSII), photosystem I (PSI) is has a different electron supplier and electron acceptor.
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
01:32Photosystems
Photosystems are multiprotein complexes that form the functional units of photosynthesis in plants, algae, and cyanobacteria. They are found embedded in the membrane of tiny sac-like structures called thylakoids placed inside the chloroplast.
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
01:29The Photochemical Reaction Center
Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center is a more appropriate term that describes these complexes. The Nobel laureates Robert Emerson and William Arnold provided the first experimental evidence of photochemical reaction centers by demonstrating the participation of nearly 2,500 chlorophyll molecules for the release of just one molecule of oxygen. Despite thousands of photosynthetic...
01:32UV–Vis Spectroscopy of Conjugated Systems
Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent of conjugation in the...
One of the factors influencing λmax is the extent of conjugation in the...
01:15The Antenna Complex
Plants and other photosynthetic organisms comprise pigments capable of absorption of direct sunlight. These pigments are present in the reaction center - the main site of photochemical reactions as well as in the antenna complex. Under average light conditions, the rate at which reaction center pigments absorb light is far below the electron transport chain's capacity. As a result, the reaction center alone cannot provide enough energy to drive photosynthesis. The photosynthetic efficiency can...