FLD interacts with CO to affect both flowering time and floral initiation in Arabidopsis thaliana

fld and co, both with significantly delayed flowering, are characterized as late-flowering mutations in Arabidopsis thaliana. Double mutants between f ld-2 and co-3 were generated and the phenotypes characterized. Double mutan ts flower later than both single mutant parents, suggesting that there is a n additive effect. In addition, the formation of flowers in double mutants was altered and showed a novel phenotype. Double mutant flowers contained a much longer stalk (pedicel). Sepals and petals were absent, Several leaf-l ike structures were produced in the position normally occupied by sepals an d the organ numbers were reduced. The carpels were morphologically normal. The stamens produced were usually aborted in the early stage, thus, the flo wers were sterile. The additive phenotype observed in double mutants provid es evidence to support that these two genes, FLD and CO, are not only invol ved in rosette-to-inflorescence transition but also involved in the bower f ormation. This result also indicates that FLD and CO promote the reproducti ve program through two different pathways.