Two mechanisms for dissipation of excess light in monomeric and trimeric light-harvesting complexes

Research output: Contribution to journalArticle


Oxygenic photoautotrophs require mechanisms for rapidly matching the level of chlorophyll excited states from light harvesting with the rate of electron transport from water to carbon dioxide. These photoprotective reactions prevent formation of reactive excited states and photoinhibition. The fastest response to excess illumination is the so-called non-photochemical quenching which, in higher plants, requires the luminal pH sensor PsbS and other yet unidentified components of the photosystem II antenna. Both trimeric light-harvesting complex II (LHCII) and monomeric LHC proteins have been indicated as site(s) of the heat-dissipative reactions. Different mechanisms have been proposed: Energy transfer to a lutein quencher in trimers, formation of a zeaxanthin radical cation in monomers. Here, we report on the construction of a mutant lacking all monomeric LHC proteins but retaining LHCII trimers. Its non-photochemical quenching induction rate was substantially slower with respect to the wild type. A carotenoid radical cation signal was detected in the wild type, although it was lost in the mutant. We conclude that non-photochemical quenching is catalysed by two independent mechanisms, with the fastest activated response catalysed within monomeric LHC proteins depending on both zeaxanthin and lutein and on the formation of a radical cation. Trimeric LHCII was responsible for the slowly activated quenching component whereas inclusion in supercomplexes was not required. This latter activity does not depend on lutein nor on charge transfer events, whereas zeaxanthin was essential.


  • Luca Dall'Osto
  • Stefano Cazzaniga
  • Mauro Bressan
  • David Paleček
  • Karel Židek
  • Krishna K. Niyogi
  • Graham R. Fleming
  • Donatas Zigmantas
  • Roberto Bassi
External organisations
  • University of Verona
  • University of California, Berkeley
  • Lawrence Berkeley National Laboratory
  • CNR Institute for Sustainable Plant Protection (IPSP)
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Biochemistry and Molecular Biology
Original languageEnglish
Article number17033
JournalNature Plants
Publication statusPublished - 2017 Apr 10
Publication categoryResearch