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 fld-2 and co-3 were generated and the phenotypes characterized. Double mutants flower later than both single mutant parents, suggesting that there is an 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-like structures were produced in the position normally occupied by sepals and the organ numbers were reduced. The carpels were morphologically normal. The stamens produced were usually aborted in the early stage, thus, the flowers were sterile. The additive phenotype observed in double mutants provides evidence to support that these two genes, FLD and CO, are not only involved in rosette-to-inflorescence transition but also involved in the flower formation. This result also indicates that FLD and CO promote the reproductive program through two different pathways.