SUMMARY In many species, FLOWERING LOCUS T ( FT )‐like genes promote the floral transition by integrating environmental signals, in particular photoperiod, and internal cues. Here we show that Brassica napus contains six FT ‐like genes and two pseudogenes belonging to three orthogroups. All B. napus FT ‐like genes induce early flowering when expressed at the shoot apical meristems of Arabidopsis thaliana ft mutants; however, BnaFT.C6 and non‐orthologous FT ‐like genes do not encode fully functional mobile florigens. In the case of BnFT.C6 , the functional change is associated with a T to C amino acid change that is restricted to semi‐winter accessions. Expression of orthologs of FT is photoperiod‐dependent, and two distal enhancers are conserved; however, the homeologs BnaFT.A7 and BnaFT.C6 show rearrangements of DNA motifs binding NF‐Y/CO and NF‐Y transcriptional activator complexes between the promoter and downstream enhancers. Motif rearrangements correlate with differences in tissue‐specific expression. Furthermore, homeologs with rearranged motifs could not be transactivated by B. napus CO in transient assays, although they show LD photoperiod‐dependent expression. We propose that differential diurnal expression of NF‐Y genes contributes to the photoperiod‐dependent regulation of B. napus FT genes.
Wang et al. (Fri,) studied this question.