Changes in aggregation states of light-harvesting complexes as a mechanism for modulating energy transfer in desert crust cyanobacteria

Leeat Bar Eyal, R. Ranjbar Choubeh, Eyal Cohen, Ido Eisenberg, Carmen Tamburu, Márta Dorogi, Renata Ünnep, Marie-Sousai Appavou, Reinat Revo, Uri Raviv, Ziv Reich, Gyozo Garab, H. van Amerongen, Yossi Paltiel, Nir Keren*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

12 Citations (Scopus)

Abstract

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.
Original languageEnglish
Pages (from-to)9481-9486
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number35
DOIs
Publication statusPublished - 2017

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  • Cite this

    Bar Eyal, L., Ranjbar Choubeh, R., Cohen, E., Eisenberg, I., Tamburu, C., Dorogi, M., Ünnep, R., Appavou, M-S., Revo, R., Raviv, U., Reich, Z., Garab, G., van Amerongen, H., Paltiel, Y., & Keren, N. (2017). Changes in aggregation states of light-harvesting complexes as a mechanism for modulating energy transfer in desert crust cyanobacteria. Proceedings of the National Academy of Sciences of the United States of America, 114(35), 9481-9486. https://doi.org/10.1073/pnas.1708206114