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

Leeat Bar Eyal, Reza Ranjbar Choubeh, Eyal Cohen, Ido Eisenberg, Carmen Tamburu, Márta Dorogi, Renata Ünnep, Marie Sousai Appavou, Reinat Nevo, Uri Raviv, Ziv Reich, Gyözö Garab, Herbert Van Amerongen, Yossi Paltiel, Nir Keren*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

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 languageAmerican English
Pages (from-to)9481-9486
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number35
DOIs
StatePublished - 29 Aug 2017

Bibliographical note

Publisher Copyright:
© 2017, National Academy of Sciences. All rights reserved.

Keywords

  • Cyanobacteria
  • Desiccation
  • Energy dissipation
  • Photosynthetic efficiency
  • Phycobilisome

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