The true identity of florigen – the molecule(s) that migrates from leaves to
apical meristem to initiate flowering -- was notoriously elusive, having made it almost
the “Bigfoot” of plant biology. There was never a lack of drama in the field of florigen
study, and florigen researchers have once again experienced such a swing in the last
two years. We wrote a Minireview last year in this journal (Yu et al., 2006) to excitedly
salute, among other discoveries, the notion that the FT mRNA might be the molecular
form of a florigen. However, this hypothesis was challenged in a little less than two
years after its initial proposition, and the original paper proposed the FT mRNA
hypothesis was retracted (Huang et al., 2005; Bohlenius et al., 2007). Interestingly
enough, the FT gene previously proposed to encode a florigen was never challenged.
Rather, the FT protein, instead of the FT mRNA, is now believed to migrate from leaves
to the apical meristem to promote floral initiation. In this Update, we will share with our
readers some entertaining stories concerning the recent studies of florigen in five
different plant species. In addition to the literature referenced in this Update, readers
may also refer to our previous Minireview and references therein for additional
background information (Yu et al., 2006).