The early-flowering mutant efs is involved in the autonomous promotion pathway of Arabidopsis thaliana

The transition to flowering is a crucial moment in a plant's life cycle of which the mechanism has only been partly revealed, In a screen for early fl owering, after mutagenesis of the late-flowering fwa mutant of Arabidopsis thaliana, the early flowering in short days (efs) mutant was identified, Un der long-day light conditions, the recessive monogenic efs mutant flowers a t the same time as wild type but, under short-day conditions, the mutant fl owers much earlier. In addition to its early-flowering phenotype, efs has s everal pleiotropic effects such as a reduction in plant size, fertility and apical dominance, Double mutant analysis with several late-flowering mutan ts from the autonomous promotion (fca and fve) and the photoperiod promotio n (co,fwa and gi) pathways of flowering showed that efs reduces the floweri ng time of all these mutants. However, efs is completely epistatic to fca a nd fve but additive to co, fwa and gi, indicating that EFS is an inhibitor of flowering specifically involved in the autonomous promotion pathway. A v ernalisation treatment does not further reduce the flowering time of the ef s mutant, suggesting that vernalisation promotes flowering through EFS, By comparing the length of the juvenile and adult phases of vegetative growth for wild-type, efs and the double mutant plants, it is apparent that efs ma inly reduces the length of the adult phase.