scholarly journals The Loroxanthin cycle: A new type of xanthophyll cycle in green algae (Chlorophyta)

2021 ◽  
Author(s):  
Tom E van den Berg ◽  
Roberta Croce
Keyword(s):  
Energy Transfer ◽  
Xanthophyll Cycle ◽  
Excitation Energy Transfer ◽  
Spectroscopic Properties ◽  
High Light ◽  
Low Light ◽  
Time Points ◽  
Long Time ◽  
New Type ◽  
Shade Adaptation

Xanthophyll cycles have proven to be major contributors to photoacclimation for many organisms. This work describes a light-driven xanthophyll cycle operating in the chlorophyte Chlamydomonas reinhardtii and involving the xanthophylls Lutein (L) and Loroxanthin (Lo). Pigments were quantified during a switch from high to low light and at different time points from cells grown in Day/night cycle. Trimeric LHCII was purified from cells acclimated to high or low light and their pigment content and spectroscopic properties were characterized. The Lo/(L+Lo) ratio in the cells varies by a factor of 10 between cells grown in low or high light leading to a change in the Lo/(L+Lo) ratio in trimeric LHCII from 0.5 in low light to 0.07 in high light. Trimeric LhcbMs binding Loroxanthin have 5+/-1% higher excitation energy transfer from carotenoid to Chlorophyll as well as higher thermo- and photostability than trimeric LhcbMs that only bind Lutein. The Loroxanthin cycle operates on long time scales (hours to days) and likely evolved as a shade adaptation. It has many similarities with the Lutein-epoxide - Lutein cycle of plants.

scholarly journals Energy-Saving Research on New Type of LED Sensor Lamp with Low-Light Mode

Electronics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 1649
Author(s):  
Chun-Te Lee ◽  
Ping-Tsan Ho
Keyword(s):  
Energy Saving ◽  
Power Saving ◽  
High Light ◽  
Saving Rate ◽  
Dark Mode ◽  
Low Light ◽  
Light Mode ◽  
New Type ◽  
Women And Children ◽  
Human Eyes

In general, the sensor lamps in the corridors, stairwells, or toilets of buildings will change from completely dark to full brightness when someone passes by. It will make the human eyes feel very uncomfortable, and when the sensor lamp is completely dark, the whole corridor and stairwell will be dark, making women and children feel insecure at night. If the lighting is changed to be sensor-less, there is a serious problem of wasted energy. To solve this dilemma, we developed a new type of “LED sensor lamp with low-light mode” that changes the original “full dark mode” to “low-light mode”. As such, when someone approaches the sensor lamp, their eyes will not be uncomfortable with the momentary illumination. Furthermore, when no one passes by, the sensor lamp will stay in low-light mode, so that people returning home at night no longer have to go through dark corridors, thereby achieving safety, aesthetics, and energy-saving purposes. This new sensor lamp’s power consumption in low-light mode is only 1/10 of the high-light mode, but its brightness can be up to half of the high-light mode, making it very suitable for parking lots, corridors, stairways, or toilets of buildings. It only requires the replacement of the lamp but not the original lamp socket, yet the basic brightness can be maintained. Take the general 15W T8 LED lamp (sensor-less) as an example: if it is replaced by this new type of sensor lamp, and the place where it is installed is rarely passed by people, the power saving rate will be as high as 90%. Assuming that there are 12 passers-by per hour, the saving rate is still 81%.

scholarly journals PsaK2 Subunit in Photosystem I Is Involved in State Transition under High Light Condition in the Cyanobacterium Synechocystis sp. PCC 6803

2005 ◽  
Vol 280 (23) ◽  
pp. 22191-22197 ◽  
Author(s):  
Tamaki Fujimori ◽  
Yukako Hihara ◽  
Kintake Sonoike
Keyword(s):  
Energy Transfer ◽  
Photosystem I ◽  
State Transition ◽  
Light Condition ◽  
High Light ◽  
Photochemical Quenching ◽  
Wild Type ◽  
Low Light ◽  
High Light Condition ◽  
Non Photochemical Quenching

To avoid the photodamage, cyanobacteria regulate the distribution of light energy absorbed by phycobilisome antenna either to photosystem II or to photosystem I (PSI) upon high light acclimation by the process so-called state transition. We found that an alternative PSI subunit, PsaK2 (sll0629 gene product), is involved in this process in the cyanobacterium Synechocystis sp. PCC 6803. An examination of the subunit composition of the purified PSI reaction center complexes revealed that PsaK2 subunit was absent in the PSI complexes under low light condition, but was incorporated into the complexes during acclimation to high light. The growth of the psaK2 mutant on solid medium was inhibited under high light condition. We determined the photosynthetic characteristics of the wild type strain and the two mutants, the psaK1 (ssr0390) mutant and the psaK2 mutant, using pulse amplitude modulation fluorometer. Non-photochemical quenching, which reflects the energy transfer from phycobilisome to PSI in cyanobacteria, was higher in high light grown cells than in low light grown cells, both in the wild type and the psaK1 mutant. However, this change of non-photochemical quenching during acclimation to high light was not observed in the psaK2 mutant. Thus, PsaK2 subunit is involved in the energy transfer from phycobilisome to PSI under high light condition. The role of PsaK2 in state transition under high light condition was also confirmed by chlorophyll fluorescence emission spectra determined at 77 K. The results suggest that PsaK2-dependent state transition is essential for the growth of this cyanobacterium under high light condition.

Effects of lincomycin on PSII efficiency, non-photochemical quenching, D1 protein and xanthophyll cycle during photoinhibition and recovery

2004 ◽  
Vol 31 (8) ◽  
pp. 803 ◽  
Author(s):  
Kristine Mueh Bachmann ◽  
Volker Ebbert ◽  
William W. Adams III ◽  
Amy S. Verhoeven ◽  
Barry A. Logan ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Thermal Energy ◽  
Xanthophyll Cycle ◽  
D1 Protein ◽  
Light Treatment ◽  
High Light ◽  
Low Light ◽  
Psii Efficiency ◽  
High Light Treatment ◽  
Thermal Energy Dissipation

Leaves of Parthenocissus quinquefolia (L.) Planch. (Virginia creeper) were treated with lincomycin (an inhibitor of chloroplast-encoded protein synthesis), subjected to a high-light treatment and allowed to recover in low light. While lincomycin-treated leaves had similar characteristics as controls after a 1 h exposure to high light, total D1 levels in lincomycin-treated leaves were half those in controls at the end of the recovery period. In addition, lincomycin delayed recovery of maximal PSII efficiency of open centers (ratio of variable to maximal chlorophyll fluorescence, F v / F m) and of estimated PSII photochemistry rate upon return to low light subsequent to the high-light treatment. Furthermore, lincomycin treatment slowed the removal of zeaxanthin (Z) and antheraxanthin (A) during recovery in low light, and the level of thermal energy dissipation (non-photochemical fluorescence quenching, NPQ) remained elevated. In lincomycin-treated leaves infiltrated with the uncoupler nigericin immediately after high-light exposure, thermal energy dissipation, sustained with lincomycin alone, declined quickly to control levels. In summary, lincomycin treatment affected not only D1 protein turnover but also xanthophyll-cycle operation and thermal-energy dissipation. The latter effect was apparently a result of the maintenance of a high trans-thylakoid proton gradient. Similar effects were also seen subsequent to short-term exposures to high light in lincomycin-treated Spinacia oleracea L. (spinach) leaves. In contrast, lincomycin treatments under low-light levels did not induce Z formation or NPQ. These results suggest that lincomycin has the potential to lower PSII efficiency (F v / F m) through inhibition of NPQ relaxation and Z + A removal subsequent to high-light exposures.

Evidence of additional excitation energy transfer pathways in the phycobiliprotein antenna system of Acaryochloris marina

2015 ◽  
Vol 14 (2) ◽  
pp. 429-438 ◽  
Author(s):  
A. C. Nganou ◽  
L. David ◽  
N. Adir ◽  
D. Pouhe ◽  
M. J. Deen ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Light Intensity ◽  
Excitation Energy ◽  
Excitation Energy Transfer ◽  
Energy Conversion Efficiency ◽  
Antenna System ◽  
Low Light ◽  
Acaryochloris Marina ◽  
Photosynthetic Microorganisms ◽  
Additional Excitation

To improve the energy conversion efficiency of solar organic cells, the clue may lie in the development of devices inspired by an efficient light harvesting mechanism of some aquatic photosynthetic microorganisms that are adapted to low light intensity.

scholarly journals Light-harvesting mutants show differential gene expression upon shift to high light as a consequence of photosynthetic redox and reactive oxygen species metabolism

2014 ◽  
Vol 369 (1640) ◽  
pp. 20130229 ◽  
Author(s):  
Mikko Tikkanen ◽  
Peter J. Gollan ◽  
Nageswara Rao Mekala ◽  
Janne Isojärvi ◽  
Eva-Mari Aro
Keyword(s):  
Gene Expression ◽  
Reactive Oxygen Species ◽  
Energy Transfer ◽  
Excitation Energy ◽  
Light Harvesting ◽  
Expression Profiles ◽  
Excitation Energy Transfer ◽  
Reactive Oxygen ◽  
High Light ◽  
Oxygen Species

The amount of light energy that is harvested and directed to the photosynthetic machinery is regulated in order to control the production of reactive oxygen species (ROS) in leaf tissues. ROS have important roles as signalling factors that instigate and mediate a range of cellular responses, suggesting that the mechanisms regulating light-harvesting and photosynthetic energy transduction also affect cell signalling. In this study, we exposed wild-type (WT) Arabidopsis and mutants impaired in the regulation of photosynthetic light-harvesting ( stn7 , tap38 and npq4 ) to transient high light (HL) stress in order to study the role of these mechanisms for up- and downregulation of gene expression under HL stress. The mutants, all of which have disturbed regulation of excitation energy transfer and distribution, responded to transient HL treatment with surprising similarity to the WT in terms of general ‘abiotic stress-regulated’ genes associated with hydrogen peroxide and 12-oxo-phytodienoic acid signalling. However, we identified distinct expression profiles in each genotype with respect to induction of singlet oxygen and jasmonic acid-dependent responses. The results of this study suggest that the control of excitation energy transfer interacts with hormonal regulation. Furthermore, the photosynthetic pigment–protein complexes appear to operate as receptors that sense the energetic balance between the photosynthetic light reactions and downstream metabolism.

scholarly journals LHCSR1-dependent fluorescence quenching is mediated by excitation energy transfer from LHCII to photosystem I in Chlamydomonas reinhardtii

2018 ◽  
Vol 115 (14) ◽  
pp. 3722-3727 ◽  
Author(s):  
Kotaro Kosuge ◽  
Ryutaro Tokutsu ◽  
Eunchul Kim ◽  
Seiji Akimoto ◽  
Makio Yokono ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Photosystem Ii ◽  
Fluorescence Quenching ◽  
Excitation Energy ◽  
Chlamydomonas Reinhardtii ◽  
Photosystem I ◽  
Excitation Energy Transfer ◽  
High Light ◽  
Light Harvesting Complexes ◽  
Photosynthetic Organisms

Photosynthetic organisms are frequently exposed to light intensities that surpass the photosynthetic electron transport capacity. Under these conditions, the excess absorbed energy can be transferred from excited chlorophyll in the triplet state (3Chl*) to molecular O2, which leads to the production of harmful reactive oxygen species. To avoid this photooxidative stress, photosynthetic organisms must respond to excess light. In the green alga Chlamydomonas reinhardtii, the fastest response to high light is nonphotochemical quenching, a process that allows safe dissipation of the excess energy as heat. The two proteins, UV-inducible LHCSR1 and blue light-inducible LHCSR3, appear to be responsible for this function. While the LHCSR3 protein has been intensively studied, the role of LHCSR1 has been only partially elucidated. To investigate the molecular functions of LHCSR1 in C. reinhardtii, we performed biochemical and spectroscopic experiments and found that the protein mediates excitation energy transfer from light-harvesting complexes for Photosystem II (LHCII) to Photosystem I (PSI), rather than Photosystem II, at a low pH. This altered excitation transfer allows remarkable fluorescence quenching under high light. Our findings suggest that there is a PSI-dependent photoprotection mechanism that is facilitated by LHCSR1.

scholarly journals Adaptation of Rhodopseudomonas acidophila strain 7050 to growth at different light intensities: what are the benefits to changing the type of LH2?

2018 ◽  
Vol 207 ◽  
pp. 471-489 ◽  
Author(s):  
A. T. Gardiner ◽  
D. M. Niedzwiedzki ◽  
R. J. Cogdell
Keyword(s):  
Energy Transfer ◽  
High Light ◽  
Low Light ◽  
Time Resolved ◽  
Rhodopseudomonas Acidophila ◽  
Light Intensities ◽  
Transfer Properties

Femto-second time resolved absorption has been used to investigate how the energy transfer properties in the membranes of high-light and low-light adapted cells change as the composition of the LH2 complexes varies.

scholarly journals Structure of cyanobacterial phycobilisome core revealed by structural modeling and chemical cross-linking

2021 ◽  
Vol 7 (2) ◽  
pp. eaba5743
Author(s):  
Haijun Liu ◽  
Mengru M. Zhang ◽  
Daniel A. Weisz ◽  
Ming Cheng ◽  
Himadri B. Pakrasi ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excitation Energy Transfer ◽  
Energy Coupling ◽  
Regulatory Elements ◽  
Photochemical Activity ◽  
Structural Basis ◽  
Bottom Surface ◽  
Cross Linking ◽  
Orange Carotenoid Protein ◽  
Chemical Cross Linking

In cyanobacteria and red algae, the structural basis dictating efficient excitation energy transfer from the phycobilisome (PBS) antenna complex to the reaction centers remains unclear. The PBS has several peripheral rods and a central core that binds to the thylakoid membrane, allowing energy coupling with photosystem II (PSII) and PSI. Here, we have combined chemical cross-linking mass spectrometry with homology modeling to propose a tricylindrical cyanobacterial PBS core structure. Our model reveals a side-view crossover configuration of the two basal cylinders, consolidating the essential roles of the anchoring domains composed of the ApcE PB loop and ApcD, which facilitate the energy transfer to PSII and PSI, respectively. The uneven bottom surface of the PBS core contrasts with the flat reducing side of PSII. The extra space between two basal cylinders and PSII provides increased accessibility for regulatory elements, e.g., orange carotenoid protein, which are required for modulating photochemical activity.

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