Florigen activation complex forms via multifaceted assembly in Arabidopsis

ABSTRACT: 'Florigen', encoded by FT genes, is synthesized in leaves and transported to the shoot apical meristem (SAM) to induce flower development. At the SAM, 14-3-3 proteins are proposed to act as receptors for FT and to mediate the indirect interaction between FT and the bZIP transcription factor FD to form the 'florigen activation complex' (FAC) that activates transcription of flowering genes. We demonstrate a different mechanism of FAC assembly, diverse functions for the 14-3-3s within the complex and an unexpected spatiotemporal distribution of the FAC. We show that FT is not recruited by 14-3-3 alone, but that it interacts with the DNA−FD−14-3-3 complex through two interfaces, one of which binds DNA via the unstructured C-terminus of FT. Also, we find that interaction of 14-3-3s with the phosphorylated FD C-terminus reduces liquid-phase condensation of the intrinsically disordered FD protein allowing it to bind DNA, and that the 14-3-3s strengthen DNA binding of FD by promoting dimerization, which ultimately results in the recruitment of FT. Unexpectedly, we also discovered that after FT movement to the shoot apex, FT and FD are co-transcribed in young floral primordia forming a boundary with the suppressed bract and allowing formation of the FAC during the first stages of floral development. Our studies propose a new mechanism by which the florigen FT transcriptional complex is formed, and indicate distinct functions for the complex during SAM and floral primordium development.

INSTRUMENT(S):

ORGANISM(S): Arabidopsis Thaliana (mouse-ear Cress)

TISSUE(S): Plant Cell

SUBMITTER: Sara Christina Stolze  

LAB HEAD: Hirofumi Nakagami

PROVIDER: PXD067955 | Pride | 2025-09-02

REPOSITORIES: Pride