Trehalose 6-phosphate activates Target of Rapamycin in plants

Abstract Coordinating carbon availability with growth is a fundamental challenge in plants. Target of Rapamycin (TOR) promotes cell growth and is activated by sugars, but the underlying molecular mechanism has remained elusive. Here, we identify trehalose 6-phosphate (T6P), a sucrose-derived metabolite, as the key signal linking carbon to TOR activity. In Arabidopsis and Brassica napus, T6P stimulates cell growth via TOR and is required for sucrose-induced TOR activation. We show immunoprecipitates using anti-TOR antibodies contain catalytically active TOR in addition to the catalytically active SnRK1 energy sensor kinase. In vitro experiments show that, SnRK1α1, the catalytic subunit of SnRK1 suppresses TOR activity, and T6P reverses this inhibition in a dose-dependent manner, providing biochemical evidence that T6P activates TOR by suppressing SnRK1. This work thus establishes a direct sucrose–T6P–SnRK1–TOR signaling axis that couples carbon availability to plant growth. Competing Interest Statement The authors have declared no competing interest.