REGULATIONS OF FLOWERING TIME BY ARABIDOPSIS PHOTORECEPTORS

The shift in plants from vegetative growth to floral development is re gulated by red-far-red light receptors (phytochromes) and blue-ultravi olet A light receptors (cryptochromes). A mutation in the Arabidopsis thaliana CRY2 gene encoding a blue-light receptor apoprotein (CRY2) is allelic to the late-flowering mutant, fha. Flowering in cry2/fha muta nt plants is only incompletely responsive to photoperiod. Cryptochrome 2 (cry2) is a positive regulator of the flowering-time gene CO, the e xpression of which is regulated by photoperiod. Analysis of flowering in cry2 and phyB mutants in response to different wavelengths of light indicated that flowering is regulated by the antagonistic actions of phyB and cry2.