Antagonistic actions of @entity958 cryptochromes and XXXX in the regulation of floral induction.

@entity958 @entity16607 @entity16606 @entity28781
The @entity958 photoreceptors @entity16606 , @entity16607 and @entity28781 are known to play roles in the regulation of flowering time, for which the molecular mechanisms remain unclear. We have previously hypothesized that @entity28781 mediates a red-light inhibition of floral initiation and @entity16607 mediates a blue-light inhibition of the @entity28781 function. Studies of the @entity16607 / @entity28781 double mutant provide direct evidence in support of this hypothesis. The function of cryptochromes in floral induction was further investigated using the @entity16607 / @entity16606 double mutants. The @entity16607 / @entity16606 double mutants showed delayed flowering in monochromatic blue light, whereas neither monogenic @entity16606 nor @entity16607 mutant exhibited late flowering in blue light. This result suggests that, in addition to the @entity28781 -dependent function, @entity16607 also acts redundantly with @entity16606 to promote floral initiation in a @entity28781 -independent manner. To understand how photoreceptors regulate the transition from vegetative growth to reproductive development, we examined the effect of sequential illumination by blue light and red light on the flowering time of plants. We found that there was a light-quality-sensitive phase of plant development, during which the quality of light exerts a profound influence on flowering time. After this developmental stage, which is between approximately day-1 to day-7 post germination, plants are committed to floral initiation and the quality of light has little effect on the flowering time. Mutations in either the @entity28781 gene or both the @entity16606 and @entity16607 genes resulted in the loss of the light-quality-sensitive phase manifested during floral development. The commitment time of floral transition, defined by a plant's sensitivity to light quality, coincides with the commitment time of inflorescence development revealed previously by a plant's sensitivity to light quantity - the photoperiod. Therefore, the developmental mechanism resulting in the commitment to flowering appears to be the direct target of the antagonistic actions of the photoreceptors.
