TY - JOUR
T1 - Changes in aggregation states of light-harvesting complexes as a mechanism for modulating energy transfer in desert crust cyanobacteria
AU - Eyal, Leeat Bar
AU - Choubeh, Reza Ranjbar
AU - Cohen, Eyal
AU - Eisenberg, Ido
AU - Tamburu, Carmen
AU - Dorogi, Márta
AU - Ünnep, Renata
AU - Appavou, Marie Sousai
AU - Nevo, Reinat
AU - Raviv, Uri
AU - Reich, Ziv
AU - Garab, Gyözö
AU - Van Amerongen, Herbert
AU - Paltiel, Yossi
AU - Keren, Nir
N1 - Publisher Copyright:
© 2017, National Academy of Sciences. All rights reserved.
PY - 2017/8/29
Y1 - 2017/8/29
N2 - In this paper we propose an energy dissipation mechanism that is completely reliant on changes in the aggregation state of the phycobilisome light-harvesting antenna components. All photosynthetic organisms regulate the efficiency of excitation energy transfer (EET) to fit light energy supply to biochemical demands. Not many do this to the extent required of desert crust cyanobacteria. Following predawn dew deposition, they harvest light energy with maximum efficiency until desiccating in the early morning hours. In the desiccated state, absorbed energy is completely quenched. Time and spectrally resolved fluorescence emission measurements of the desiccated desert crust Leptolyngbya ohadii strain identified (i) reduced EET between phycobilisome components, (ii) shorter fluorescence lifetimes, and (iii) red shift in the emission spectra, compared with the hydrated state. These changes coincide with a loss of the ordered phycobilisome structure, evident from small-angle neutron and X-ray scattering and cryo-transmission electron microscopy data. Based on these observations we propose a model where in the hydrated state the organized rod structure of the phycobilisome supports directional EET to reaction centers with minimal losses due to thermal dissipation. In the desiccated state this structure is lost, giving way to more random aggregates. The resulting EET path will exhibit increased coupling to the environment and enhanced quenching.
AB - In this paper we propose an energy dissipation mechanism that is completely reliant on changes in the aggregation state of the phycobilisome light-harvesting antenna components. All photosynthetic organisms regulate the efficiency of excitation energy transfer (EET) to fit light energy supply to biochemical demands. Not many do this to the extent required of desert crust cyanobacteria. Following predawn dew deposition, they harvest light energy with maximum efficiency until desiccating in the early morning hours. In the desiccated state, absorbed energy is completely quenched. Time and spectrally resolved fluorescence emission measurements of the desiccated desert crust Leptolyngbya ohadii strain identified (i) reduced EET between phycobilisome components, (ii) shorter fluorescence lifetimes, and (iii) red shift in the emission spectra, compared with the hydrated state. These changes coincide with a loss of the ordered phycobilisome structure, evident from small-angle neutron and X-ray scattering and cryo-transmission electron microscopy data. Based on these observations we propose a model where in the hydrated state the organized rod structure of the phycobilisome supports directional EET to reaction centers with minimal losses due to thermal dissipation. In the desiccated state this structure is lost, giving way to more random aggregates. The resulting EET path will exhibit increased coupling to the environment and enhanced quenching.
KW - Cyanobacteria
KW - Desiccation
KW - Energy dissipation
KW - Photosynthetic efficiency
KW - Phycobilisome
UR - http://www.scopus.com/inward/record.url?scp=85028538488&partnerID=8YFLogxK
U2 - 10.1073/pnas.1708206114
DO - 10.1073/pnas.1708206114
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C2 - 28808031
AN - SCOPUS:85028538488
SN - 0027-8424
VL - 114
SP - 9481
EP - 9486
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 35
ER -