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Abstract:
The rhythmic opening/closing and volatile emissions of flowers are known to attract pollinators
at specific times. That these rhythms are maintained under constant light or dark conditions
suggests a circadian clock involvement. Although a forward and reverse genetic
approach has led to the identification of core circadian clock components in Arabidopsis
thaliana, the involvement of these clock components in floral rhythms has remained untested,
probably because of the weak diurnal rhythms in A. thaliana flowers.
Here, we addressed the role of these core clock components in the flowers of the wild
tobacco Nicotiana attenuata, whose flowers open at night, emit benzyl acetone (BA) scents
and move vertically through a 140° arc.
We first measured N. attenuata floral rhythms under constant light conditions. The results
suggest that the circadian clock controls flower opening, BA emission and pedicel movement,
but not flower closing.
We generated transgenic N. attenuata lines silenced in the homologous genes of Arabidopsis
LATE ELONGATED HYPOCOTYL (LHY) and ZEITLUPE (ZTL), which are known to be core
clock components. Silencing NaLHY and NaZTL strongly altered floral rhythms in different
ways, indicating that conserved clock components in N. attenuata coordinate these floral rhythms.
