69. The flowering repressor gene that is responsible for the vernalization requirement in Arabidopsis is:
(1) CONSTANS (CO)
(2) FLOWERING LOCUS D (FD)
(3) FLOWERING LOCUS T (FT)
(4) FLOWERING LOCUS C (FLC)

 

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Introduction

FLOWERING LOCUS C (FLC) is a central floral repressor gene in Arabidopsis thaliana that mediates the plant’s vernalization requirement—the necessity of prolonged cold exposure to initiate flowering. As a MADS-box transcription factor, FLC represses key flowering promoting genes, delaying flowering until favorable conditions arise.

Role of FLC in Vernalization and Flowering

• FLC represses genes such as FLOWERING LOCUS T (FT) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) that promote flowering.

• Vernalization promotes flowering by epigenetically silencing FLC after exposure to prolonged cold, removing repression and allowing activation of flowering pathways.

• FLC expression and protein levels correlate with late flowering times in winter-annual Arabidopsis ecotypes; reduced FLC leads to rapid flowering.

Molecular Mechanism and Epigenetic Control

• Prolonged cold leads to stable, mitotically heritable repression of FLC through chromatin remodeling and histone modifications.

• FLC interacts with other flowering genes and integrates environmental signals ensuring flowering only occurs after vernalization.

Contrasting Other Genes Listed

• CONSTANS (CO) activates flowering in response to photoperiod but is not a repressor nor involved in vernalization.

• FLOWERING LOCUS T (FT) is a promoter of flowering and a mobile florigenic signal, downstream of FLC repression.

• FLOWERING LOCUS D (FD) is a transcription factor partnering with FT to trigger flower development, not a vernalization repressor.

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Summary Table: Gene Functions in Arabidopsis Flowering

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Conclusion

FLOWERING LOCUS C (FLC), a MADS-box gene, acts as the major flowering repressor mediating vernalization-dependent flowering in Arabidopsis, making option (4) the correct answer.

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FAQ