Far-red fluorescence: A direct spectroscopic marker for LHCII oligomer formation in non-photochemical quenching

Abstract 

Time-resolved fluorescence on oligomers of the main light-harvesting complex from higher plants indicate that in vitro oligomerization leads to the formation of a weakly coupled inter-trimer chlorophyll–chlorophyll (Chl) exciton state which converts in tens of ps into a state which is spectrally broad and has a strongly far-red enhanced fluorescence spectrum. Both its lifetime and spectrum show striking similarity with a 400ps fluorescence component appearing in intact leaves of Arabidopsis when non-photochemical quenching (NPQ) is induced. The fluorescence components with high far-red/red ratio are thus a characteristic marker for NPQ conditions in vivo. The far-red emitting state is shown to be an emissive Chl–Chl charge transfer state which plays a crucial part in the quenching.

Abbreviations: Chl, chlorophyll, cmc, critical micelle concentration, CT, charge transfer, DAS, decay associated spectra, DM, dodecyl maltoside, LHCI, light-harvesting complex of photosystem I, LHCII, major light-harvesting complex of photosystem II, NPQ, non-photochemical quenching, Nx, neoxanthin, PSI, photosystem I, PSII, photosystem II, SAS, species-associated spectra, Vx, violaxanthin, Zx, zeaxanthin

Keywords: LHCII, Aggregation, Chlorophyll fluorescence, Non-photochemical quenching, Violaxanthin, Zeaxanthin, Arabidopsis mutant