Different roles of flowering time genes in the activation of floral initiation genes in Arabidopsis.

We have analyzed double mutants that combine late-flowering mutations at four flowering-time loci (f E, FPA, F WA, and FT) with mutations at the LEAFY ( L N ) , APETALA7 (AP7), and TERMlNAL FLOWER7 (TFL7) loci involved in the floral initiation process (FLIP). Double mutants between f t -7 or fwa-7 and lfy-6 completely lack flowerlike structures, indicating that both F WA and F T act redundantly with LF Y to control AP7. Moreover, the phenotypes of f t 7 ap7-7 and fwa-7 ap7-7 double mutants are reminiscent of the phenotype of ap7-7 cal-7 double mutants, suggesting that FWA and F T could also be involved in the control of other FLlP genes. Such extreme phenotypes were not observed in double mutants between f v e d or fpa-7 and lfy-6 or ap7-7. Each of these showed a phenotype similar to that of ap7-7 or lfy-6 mutants grown under noninductive photoperiods, suggesting a redundant interaction with FLlP genes. Finally, the phenotype of double mutants combining the late-flowering mutations with tfH-2 were also consistent with the different roles of flowering-time genes.