Carrot can be induced to flower without exposure to a low temperature if treated with gibberellin (GA). This suggests that GA is involved in vernalization. However, an early-flowering ecotype, Landsberg erecta (Ler), of Arabidopsis thaliana is hastened to flower by GA application although it does not respond to low temperature. Gibberellin 1-3 (ga1-3) mutant lacking kaurene (GA precursor)-synthesizing enzyme and gibberellin insensitive (gai) mutant lacking sensitivity to GA are induced to flower by exposure to a low temperature. Therefore, GA and low temperature may be independently involved in flowering.

　　The flowering locus C (flc) is a low temperature-insensitive mutant. The expression of FLC gene is suppressed by a low temperature. The early-flowering ecotype Ler of Arabidopsis thaliana, which does not require vernalization for flowering, does not express the FLC gene. The gene expression of FLC in the late-flowering mutant fca-1 is decreased by vernalization, and the expression of the FLC gene is suppressed by the FCA gene. These facts suggest that the FLC gene plays a central role in low temperature requirement. The FLC gene product is a transcription factor with MADS domain.
　　The low temperature-insensitive flc mutant is induced to flower under long-day conditions. Therefore, the FLC is not involved in photoperiodic flowering.

　　The low temperature stimulus is perceived at the seed or seedling stage, and its effect appears later when the plant has matured. This means that the information established at the seed or seedling stage can be held stably for a long period of time even after the cell divisions has been repeated for tens of thousands times. In fact, the FLC gene expression continued to be suppressed in the once-vernalized plants. DNA methylation is involved in such a stable change in the gene activity maintained through repeated cell divisions.
　　Flowering of the low-temperature-sensitive late-flower mutants, fca was promoted if treated with a demethylation reagent, 5-azacytidine. Low-temperature requiring Thlaspi arvense （Brassicaceae）and winter wheat were also induced to flower by 5-azacytidine treatment. Transformation with antisense methyl-transferase gene promoted flowering. These results suggest that the expression of the genes necessary for flowering are suppressed by DNA methylation. The introduction of methyl residue to cytosine in DNA prevents the attachment of transcription factor and therefore suppresses the expression of the genes.
　　In vernalization, low temperature may suppress the activity of DNA methyl transferase and demethylate the flowering-related genes resulting in induction of their expression.