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Abstract

Summary The vegetative phase change marks the beginning of adult phase in the life cycle of plants and is associated with a gradual decline in the microRNA miR156, in response to sucrose status. Trehalose 6-phosphate (T6P) is a sugar molecule with signaling function reporting the current sucrose state. To elucidate the role of T6P signaling in vegetative phase change, molecular, genetic and metabolic analyses were performed using the Arabidopsis thaliana loss-of-function lines in TREHALOSE PHOSPHATE SYNTHASE1 (TPS1), a gene coding for an enzyme that catalyzes the production of T6P. These lines show a significant delay in vegetative phase change, both under short and long days. Induced expression of TPS1 complements this delay in TPS1 knock-out mutant (tps1-2 GVG::TPS1). Further analyses indicate that the T6P pathway promotes vegetative phase transition by suppressing miR156 and thereby modulating the levels of its target transcripts, the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE genes. TPS1 knock-down plants with a delayed vegetative phase change phenotype, accumulate significantly more sucrose than wild-type plants as a result of a feed-back regulation. In summary, we conclude that the T6P pathway forms an integral part of an endogenous mechanism that influences phase transitions dependent on the metabolic state.