Florigen Accelerates Secondary Cell Wall Biogenesis to Harmonize Vascular Maturation with flowering and reproductive phase Development

The protein hormone florigen is a universal systemic inducer of flowering and a generic growth terminator across meristems. To understand the developmental rational for its pleiotropic functions and to uncover the deep cellular systems mobilized by florigen beyond flowering we explored the radial expansion of tomato stems. RNAseq, genetic analysis and histological validations show that endogenous, mobile, or induced florigen accelerate secondary cell wall biogenesis (SCWB), and hence vascular maturation, in coordination with but independently of flowering. Conversely, a systemic FT-like florigen antagonist from Ginkgo biloba, arrests SCWB. Downstream of florigen, RNAseq identified MADS/FUL and MIF genes, that similarly impact SCWB independent from flowering. Florigen we show is remarkably stable and distributed to all organs regardless of pre-existing endogenous levels. By accelerating SCWB, florigen triggers a global redistribution of resources, signals and mechanical loads, thereby harmonizing vascular maturation with the reproductive development it had originally set into motion. Overall design: The florigen hormone, vegetative functions, growth and end cellular targets.