Journal Article

FZJ-2017-07371

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Changes in aggregation states of light-harvesting complexes as a mechanism for modulating energy transfer in desert crust cyanobacteria

Bar Eyal, L. ; Ranjbar Choubeh, R. ; Cohen, E. ; Eisenberg, I. ; Tamburu, C. ; Dorogi, M. ; Ünnep, R. ; Appavou, M.-S.FZJ* ; Nevo, R. ; Raviv, U. ; Reich, Z. ; Garab, G. ; van Amerongen, H. ; Paltiel, Y. ; Keren, N. (Corresponding author)

2017
National Acad. of Sciences Washington, DC

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Please use a persistent id in citations: doi:10.1073/pnas.1708206114

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.

Keyword(s): Polymers, Soft Nano Particles and Proteins (1st) ; Biology (2nd)

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Contributing Institute(s):

1. JCNS-FRM-II (JCNS (München) ; Jülich Centre for Neutron Science JCNS (München) ; JCNS-FRM-II)
2. Neutronenstreuung (Neutronenstreuung ; JCNS-1)

Research Program(s):

1. 6G15 - FRM II / MLZ (POF3-6G15) (POF3-6G15)
2. 6G4 - Jülich Centre for Neutron Research (JCNS) (POF3-623) (POF3-623)

Experiment(s):

1. KWS-2: Small angle scattering diffractometer (NL3ao)

Appears in the scientific report 2017

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Database coverage:
; BIOSIS Previews ; Current Contents - Agriculture, Biology and Environmental Sciences ; Current Contents - Life Sciences ; Ebsco Academic Search ; IF >= 5 ; JCR ; NCBI Molecular Biology Database ; National-Konsortium ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection ; Zoological Record

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