FT Protein Acts as a Long-Range Signal in Arabidopsis

Abstract

Plants are sessile organisms and must respond to changes in environmental conditions. Flowering time is a key developmental switch that is affected by both day length and temperature. Environmental cues are sensed by the leaves while the responses occur at the apex, requiring long-range communication within the plant. For many years it has been known that leaves exposed to light can trigger the floral transition of a darkened shoot, and grafting experiments demonstrated that the floral stimulus travels long distances. This mobile signal was later termed "florigen," but its nature has been unclear. The gene FLOWERING LOCUS T (FT) is a major output of both the photoperiod and the vernalization pathways controlling the floral transition. FT protein acts at the shoot apex of the plant in concert with a transcription factor, FLOWERING LOCUS D (FD). A fundamental question is how FT transcription in the leaves leads to active FT protein at the apex. We have uncoupled FT protein movement from its biological function to show that FT protein is the mobile signal that travels from the leaves to the apex. To our knowledge, FT is the only known protein that serves as a long-range developmental signal in plants.

Long-distance movement of ArabidopsisFLOWERING LOCUS TRNA participates in systemic floral regulation

“…In addition, the movement of FT protein is sufficient to trigger floral initiation, which suggests that the FT protein is a key part of the florigenic signaling pathway. 9,10,[20][21][22][23] Parallel proteomic analyses showed that FT protein is translocated through phloem sap, which is consistent with the notion that the florigen is transported along the phloem translocation stream. 24 Thus, FT protein is clearly part of the florigen.…”

“…Arabidopsis transformants expressing NLS FT or 3XYFP:NLS in companion cells failed to complement the late flowering of ft mutants, which suggests that the movement of FT RNA is not sufficient to promote flowering. 20,21 However, because the movement of engineered FT RNA was not examined directly, the constructs used to interfere with the movement of FT protein may have affected the movement of FT RNA. In another experiment, the expression of an artificial miRNA against FT RNA in the apex did not affect floral initiation, which suggests that FT RNA in the apex is not necessary for flowering.…”

“…9,23,25 Expression of immobilized FT protein with a nuclear localization signal or three copies of yellow fluorescent protein in companion cells failed to rescue the late flowering of ft mutants, which suggests that the movement of FT RNA is not sufficient to promote flowering. 20,21 In addition, the expression of an artificial microRNA (amiRNA) against the FT RNA in the apex did not affect floral initiation, suggesting that FT RNA in the apex may not be necessary for flowering. 21 On the contrary, use of an RNA mobility assay system based on movement-defective viruses and agroinfiltration revealed that FT RNA moves systemically in Arabidopsis and Nicotiana benthamiana.…”

Mutation inTERMINAL FLOWER1Reverses the Photoperiodic Requirement for Flowering in the Wild StrawberryFragaria vesca

“…In contrast, in the SD plant rice, an FT homolog, Heading date3a, is activated when the CO homolog Heading date1 peaks after dusk in SDs (Hayama et al, 2003). After the activation of FT expression, the FT protein moves through the phloem to the shoot apex (Corbesier et al, 2007;Jaeger and Wigge, 2007;Tamaki et al, 2007), where 14-3-3 proteins bridge its interaction with a bZIP transcription factor, FLOWERING LOCUS D (FD; Taoka et al, 2011). The FT/14-3-3/FD complex, in turn, induces flowering by up-regulating the floral meristem identity genes APETALA1 (AP1) and FRUITFULL (FUL; Abe et al, 2005;Wigge et al, 2005).…”

Effects of Light Quality on Vegetative Growth and Flower Initiation in Phalaenopsis

“…There are some genes involved in flowering and among those genes, FLOWERING LOCUS T (FT) is a fl oral integrator that plays an important role in controlling fl owering time. Most recently, the nature of FT and its ortholog as fl origen, a mobile fl owering signal, has been proposed in tomato, rice, arabidopsis and cucurbits (Lifschitz, et al, 2006;Tamaki et al, 2007;Corbesier et al, 2007;Jaeger and Wigge, 2007;Mathieu et al, 2007;Lin et al, 2007;Notaguchi et al, 2008;Zeevart, 2008). At present, the isolation of FT gene in orchid (Oncidium Gower Ramsey) has been reported.…”