| The transition from vegetative growth to flowering is the major developmental switch in the plant life cycle. The timing of flower intiation is critical for reproductive success. Flowering is regulated by endogenous as well as environmental signals. Molecular genetic studies on Arabidopsis thaliana revealed four major flowering pathways: the photoperiod, the vernalization, the autonomous, and the gibberellin pathways. The acquisition of mutants related to flowering time played an important role in uncovering floral development. In this study, a late-flowering Arabidopsis mutant flx was isolated, genetically analyzed and the FLX locus was initially mapped.Seeds of wild-type Arabidopsis thaliana (Columbia) were mutagenized with EMS, M2 populations were screened by rosette leaf number and flowering time. Fourteen potential late-flowering mutants were selected from M2 seedlings, and one of these M2 mutants maintained late-flowering in their M3 and M4 generations. This flx mutant was backcrossed with the wild-type Columbia erecta background. All F1 plants showed wild-type early-flowering phenotype. In F2 populations, the early-flowering and late-flowering seedlings segregated 216:71 (3:1). The result of genetic analysis suggested that this mutant has a monogenic recessive mutation in a nuclear gene, named as flx (flowering locus x). To map flx locus, homozygous flx plants (Columbia ecotype) were crossed with wild-type plants (Landsberg ecotype). Mapping populations were composed of the late-flowering seedlings in the F2 population. Initial mapping with simple sequence length polymorphism (SSLP) molecular markers from each of the five chromosomes of Arabidopsis indicated that the flx gene was located on chromosome V. Further analysis with additional marker on chromosome V showed that FLX locus is tightly linked to nga225 with a genetic distance of 2.5 cM. The work provided a basis for further cloning flx and uncovering the molecular mechanism of flowering time control in plants.
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