Florigen: One Found, More to Follow?

Florigen(s) are molecules that are synthesized in response to appropriate photoperiods and transmitted from leaves to shoot apices to promote floral initiation. It has been recently discovered in Arabidopsis that mRNA of the FT gene acts as a florigen. In Arabidopsis, cryptochromes and phytochromes mediate long-day promotion of CO protein expression, which activates FT mRNA expression in leaves. FT mRNA is transmitted to the shoot apex, where it acts together with FD to activate transcription of floral meristem identity genes, resulting in floral initiation. The discovery of the molecular nature of a florigen was a major scientific breakthrough in 2005. Key words: florigen; photoperiod; flowering; Arabidopsis; light. Yu X, Klejnot J, Lin C (2006). Florigen: One found, more to follow? J Integrat Plant Biol 48(6), 617−621. www.blackwell-synergy.com; www.jipb.net Plants characteristically flower during a particular time of the year, in response to the most predictable seasonal change on earth, photoperiod. Long-day (LD) plants, such as Arabidopsis, garden pea, and wheat, tend to flower from late spring to earl