The FLF MADS box gene: A repressor of flowering in Arabidopsis regulated by vernalization and methylation

A MADS box gene, FLF (for FLOWERING LOCUS F), isolated from a late-flowerin g, T-DNA-tagged Arabidopsis mutant, is a semidominant gene encoding a repre ssor of flowering. The FLF gene appears to integrate the vernalization-depe ndent and autonomous flowering pathways because its expression is regulated by genes in both pathways. The level of FLF mRNA is downregulated by verna lization and by a decrease in genomic DNA methylation, which is consistent with our previous suggestion that vernalization acts to induce flowering th rough changes in gene activity that are mediated through a reduction in DNA methylation. The flf-1 mutant requires a greater than normal amount of an exogenous gibberellin (GA,) to decrease flowering time compared with the wi ld type or with vernalization-responsive late-flowering mutants, suggesting that the FLF gene product may block the promotion of flowering by GAs. FLF maps to a region on chromosome 5 near the FLOWERING LOCUS C gene, which is a semidominant repressor of flowering in late-flowering ecotypes of Arabid opsis.