Functional interaction of the circadian clock and UV RESISTANCE LOCUS 8-controlled UV-B signaling pathways in Arabidopsis thaliana

Balázs Fehér, László Kozma-Bognár, Eva Kevei, Anita Hajdu, Melanie Binkert, Seth Jon Davis, Eberhard Schäfer, Roman Ulm, Ferenc Nagy

Research output: Contribution to journalArticlepeer-review


Circadian clocks regulate many molecular and physiological processes in Arabidopsis (Arabidopsis thaliana), allowing the timing of these processes to occur at the most appropriate time of the day in a 24-h period. The accuracy of timing relies on the synchrony of the clock and the environmental day/night cycle. Visible light is the most potent signal for such synchronization, but light-induced responses are also rhythmically attenuated (gated) by the clock. Here, we report a similar mutual interaction of the circadian clock and non-damaging photomorphogenic UV-B light. We show that low-intensity UV-B radiation acts as entraining signal for the clock. UV RESISTANCE LOCUS 8 (UVR8) and CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) are required, but ELONGATED HYPOCOTYL 5 (HY5) and HY5 HOMOLOG (HYH) are dispensable for this process. UV-B responsiveness of clock gene expression suggests that photomorphogenic UV-B entrains the plant clock through transcriptional activation. We also demonstrate that UV-B induction of gene expression under these conditions is gated by the clock in a HY5/HYH-independent manner. The arrhythmic early flowering 3-4 mutant showed non-gated, high-level gene induction by UV-B, yet displayed no increased tolerance to UV-B stress. Thus, the temporal restriction of UV-B responsiveness by the circadian clock can be considered as saving resources during acclimation without losing fitness.
Original languageEnglish
Pages (from-to)37-48
Number of pages12
JournalThe Plant Journal
Issue number1
Publication statusPublished - 2011


  • circadian clock
  • entrainment
  • ultraviolet-B light
  • gene expression
  • circadian gating
  • UV-B tolerance


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