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

@entity958 @entity29820 @entity72985 @entity47340
Circadian clocks regulate many molecular and physiological processes in @entity958 ( @entity958 ), 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 ( @entity72985 ) and CONSTITUTIVELY PHOTOMORPHOGENIC   1 ( @entity29820 ) are required, but ELONGATED HYPOCOTYL   5 ( @entity47340 ) and @entity47340 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 @entity47340 /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.
