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Abstract

The floral transition is a major developmental change in a plant's life cycle and is triggered by environmental and endogenous cues. Among the potential endogenous cues is sucrose, which could link flowering to the metabolic and energy status of the plant. However, the molecular mechanisms by which sucrose and other internal signals are integrated into the complex network of flowering time egulation are not understood. The level of trehalose 6-phosphate (T6P) is closely linked to the level of sucrose, which supports the hypothesis that T6P acts as a signal of sucrose status. TREHALOSE 6-PHOSPHATE SYNTHASE 1 (TPS1) is expressed in the shoot apical meristem. We found that T6P levels rise in the shoot apex over time, increasing more than two-fold during the floral transition in long day conditions as well as in short days. Plants over-expressing an artificial microRNA against TPS1 flower much later than wild type plants. Further, increased TPS1 expression in the stem cells alone is sufficient to induce precocious flowering, while reducing T6P content by overexpression of TREHALOSE 6-PHOSPHATE PHOSPHATASE (TPP) in the stem cells delays flowering. The miRNA156 and its target genes were recently found to integrate plant age into flowering time regulation. Our data show that sucrose availability, signalled via T6P, modulates the plant's competence to flower, and that the T6P signal is integrated into the miR156 node of the flowering network.