The hot issue: TOR signalling network in plants.

The target of rapamycin (TOR) signalling network plays a pivotal role in regulating sugar metabolism and life-span in yeast, plants and mammals, in which TOR functions as a crucial protein. In plants, the TOR complex comprises TOR, RAPTOR (regulatory-associated protein of TOR) and LST8 (lethal with SEC13 protein 8). Factors like light, auxin, glucose, sucrose and amino acid can activate TOR protein as upstream signals to further phosphorylate downstream factors of TOR which promote cell proliferation and growth in plants. In this review, we analyse the TOR signalling network in plants and discuss the relationship between glucose and TOR, as well as the dynamic balance between TOR and sucrose-non-fermenting-related protein kinases (SnRKs). Given that 63 novel TOR-regulated proteins have been identified in previous studies, we also believe there are many unknown functions of TOR that need to be further investigated.