UNASSIGNED: Optimal timing of flowering in higher plants is crucial for successful reproduction and is coordinated by external and internal factors, including light and the circadian clock. In @entity958 , light-dependent stabilization of the rhythmically expressed CONSTANS (CO) is required for the activation of @entity36422 ( @entity36422 ), resulting in the initiation of flowering. Phytochrome A and cryptochrome photoreceptors stabilize CO in the evening by attenuating the activity of the CONSTITUTIVE PHOTOMORPHOGENIC 1-SUPPRESSOR OF PHYA-105 1 ( @entity29820 - @entity29819 ) ubiquitin ligase complex, which promotes turnover of CO. In contrast, @entity28781 (phyB) facilitates degradation of CO in the morning and delays flowering. Accordingly, flowering is accelerated in phyB mutants. Paradoxically, plants overexpressing phyB also show early flowering, which may arise from an early phase of rhythmic CO expression. Here we demonstrate that overexpression of phyB induces @entity36422 transcription at dusk and in the night without affecting the phase or level of CO transcription. This response depends on the light-activated Pfr form of phyB that inhibits the function of the @entity29820 - @entity29819 complex by direct interactions. Our data suggest that attenuation of @entity29820 activity results in the accumulation of CO protein and subsequent induction of @entity36422 . We show that phosphorylation of Ser-86 inhibits this function of phyB by accelerating dark reversion and thus depletion of Pfr forms in the night. Our results explain the early flowering phenotype of phyB overexpression and reveal additional features of the molecular machinery by which photoreceptors mediate photoperiodism.

High-level expression and phosphorylation of XXXX modulates flowering time in @entity958 .

@entity36422 :: ('842859(Tax:3702)', 'Gene') :: ['FT', 'FLOWERING LOCUS T'] @entity29819 :: ('819242(Tax:3702)', 'Gene') :: ['SPA1'] @entity958 :: ('3702', 'Species') :: ['Arabidopsis'] @entity28781 :: ('816394(Tax:3702)', 'Gene') :: ['phytochrome B'] @entity29820 :: ('817857(Tax:3702)', 'Gene') :: ['COP1']
@entity28781 :: (816394(Tax:3702),Gene) :: ['phytochrome B']
