Trehalose: Metabolism and Role in Stress Signaling in Plants

Trehalose is a nonreducing disaccharide composed of two glucose residues bound by an α-α linkage. First reported in 1832 in rye following ergot infection, trehalose has since been detected in a wide range of organisms, including bacteria, fungi, invertebrates, and plants. It has role in plant response to various environmental stresses such as cold and salinity, and in regulation of stomatal conductance and water-use efficiency. Trehalose is a potential signal metabolite in plant interactions with pathogenic or symbiotic microorganisms and herbivorous insects. Recently it has been found that trehalose metabolism is also crucial for normal plant growth and development. In plants, as in other eukaryotes and many prokaryotes, trehalose is synthesized via a phosphorylated intermediate, trehalose 6-phosphate (T6P). In plants, trehalose 6-phosphate (T6P), the intermediate of trehalose biosynthesis, is thought to be a signal of sucrose status and current studies point towards the role of T6P as a regulatory molecule, especially in sugar influx and metabolism. A meta-analysis reveals that the levels of T6P changes are in parallel with sucrose, which is the major product of photosynthesis and the main transport sugar in plants. The intermediate T6P is now confirmed to act as a sensor for available sucrose, hereby directly influencing the type of response to the changing environmental conditions. This is possible because T6P and/or trehalose or their biosynthetic enzymes are part of complex interaction networks with other crucial hormone and sugar-induced signaling pathways, which may function at different developmental stages.