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Circadian rhythms are associated with variation in photosystem II function and photoprotective mechanisms

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  • Yulia Yarkhunova
  • Carmela R. Guadagno
  • Matthew Rubin
  • Seth Jon Davis
  • Brent E. Ewers
  • Cynthia Weinig


Publication details

JournalPlant, Cell and Environment
DateAccepted/In press - 3 Apr 2018
DateE-pub ahead of print - 17 Apr 2018
DatePublished (current) - 1 Nov 2018
Early online date17/04/18
Original languageEnglish


The circadian clock regulates many aspects of leaf gas supply and biochemical
demand for CO2 20 , and is hypothesized to improve plant performance. Yet the extent to which the clock may regulate the efficiency of photosystem II (PSII) and photoprotective mechanisms such as heat dissipation remains largely unexplored. Based on measurements of chlorophyll a fluorescence, we estimated the maximum efficiency of photosystem II in light (Fv'/Fm') and heat dissipation by non-photochemical quenching (NPQ). We further dissected total NPQ into its main components, qE (pH-dependent quenching), qT (state-transition quenching) and qI (quenching related to photoinhibition), in clock mutant genotypes of Arabidopsis thaliana, the cognate wild-type genotypes, and a panel of recombinant inbred lines (RILs) expressing quantitative variation in clock period. Compared to mutants with altered clock function, we observed that wild-type genotypes with clock period lengths of approximately 24 hr had both higher levels of Fv'/Fm ', indicative of improved PSII function, and reduced NPQ, suggestive of lower stress on PSII light harvesting complexes. In the RILs, genetic variances were significant for Fv'/Fm' and all three components of NPQ, with qE explaining the greatest proportion of NPQ. Bivariate tests of association and structural equation models of hierarchical trait relationships showed that quantitative clock variation was empirically associated with Fv'/Fm' and NPQ, with qE mediating the relationship with gas exchange. The results demonstrate significant segregating variation for all photoprotective components, and suggest the adaptive significance of the clock may partly derive from its regulation of the light reactions of photosynthesis and of photoprotective mechanisms. Key words: Arabidopsis thaliana, circadian rhythms, chlorophyll a fluorescence, maximum efficiency of PSII, non-photochemical quenching

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© John Wiley, 2018. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details

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