It has recently emerged that many higher plants can synthesize trace amounts of trehalose. In arabidopsis disruption of the first step of trehalose synthesis, catalysed by trehalose-6-phosphate synthase (TPS), has lethal consequences, demonstrating an important physiological role. It is not yet clear what the precise function of trehalose synthesis is, but there is mounting evidence that trehalose-6-phosphate is implicated in the regulation of sugar metabolism. Further work is necessary to confirm this hypothesis and determine the underlying mechanism.