Abstract
In Arabidopsis thaliana, PRR5,PRR7 and PRR9 are the components of the central oscillator of circadian clock. prr5/7/9 triple mutants lose the sensitivity of light in hypocotyl elongation (Nakamichi et al., 2005). But their leaves restore sensitivity to light. Under light-dark condition, they show smaller leaf blades and longer petioles, like a shade-avoidance phenotype, than those grown under continuous lighting (Niimura et al., submitted). In addition, shade-avoidance marker genes, AtHB-2 and PIL1 are highly expressed during dark period in the leaves of prr5/7/9, although the expression of the genes in prr5/7/9 are very low as those in WT during light period. These result suggest the existence of the unique mechanism to repress shade avoidance response in leaves, and that it might be related with PRR5,PRR7 and PRR9.
