Journal
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY
Volume 152, Issue -, Pages 301-307Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jphotobiol.2015.07.016
Keywords
PsbS; LHCII aggregation; NPQ; Lincomycin; Arabidopsis
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Funding
- Leverhulme Trust
- UK Biotechnology and Biological Sciences Research Council
- Royal Society
- Biotechnology and Biological Sciences Research Council [BB/L019027/1] Funding Source: researchfish
- BBSRC [BB/L019027/1] Funding Source: UKRI
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Plants with varying levels of PsbS protein were grown on lincomycin. Enhanced levels of non-photochemical fluorescence quenching (NPQ) in over-expressers of the protein have been observed. This was accompanied by increased amplitude of the irreversible NPQ component, qI, previously considered to reflect mainly photoinhibition of PSII reaction centres (RCII). However, since RCIIs were largely absent the observed qI is likely to originate from the LHCII antenna. In chloroplasts of over-expressers of PsbS grown on lincomycin an abnormally large NPQ (similar to 7) was characterised by a 0.34 ns average chlorophyll fluorescence lifetime. Yet the lifetime in the Fm state was similar to that of wild-type plants. 77 K fluorescence emission spectra revealed a specific 700 nm peak typical of LHCII aggregates as well as quenching of the PSI fluorescence at 730 nm. The aggregated state manifested itself as a clear change in the distance between LHCII complexes detected by freeze-fracture electron microscopy. Grana thylakoids in the quenched state revealed 3 times more aggregated LHCII particles compared to the dark-adapted state. Overall, the results directly demonstrate the importance of LHCII aggregation in the NPQ mechanism and show that the PSII supercomplex structure plays no role in formation of the observed quenching. (C) 2015 Elsevier B.V. All rights reserved.
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