The function of trehalose biosynthesis in plants.

Trehalose (alpha-D-glucopyranosyl-1,1-alpha-D-glucopyranoside) occurs in a large variety of organisms, ranging from bacteria to invertebrate animals, where it serves as an energy source or stress protectant. Until recently, only few plant species, mainly desiccation-tolerant 'resurrection' plants, were considered to synthesise trehalose. Instead of trehalose, most other plants species accumulate sucrose as major transport sugar and during stress. The ability to synthesize sucrose has probably evolved from the cyanobacterial ancestors of plastids and may be linked to photosynthetic function. Although most plant species do not appear to accumulate easily detectable amounts of trehalose, the discovery of genes for trehalose biosynthesis in Arabidopsis and in a range of crop plants suggests that the ability to synthesise trehalose is widely distributed in the plant kingdom. The apparent lack of trehalose accumulation in these plants is probably due to the presence of trehalase activity. After inhibition of trehalase, trehalose synthesis can be detected in Arabidopsis. Since trehalose induces metabolic changes, such as an accumulation of storage carbohydrates, rapid degradation of trehalose may be required to prevent detrimental effects of trehalose on the regulation of plant metabolism. In addition, the precursor of trehalose, trehalose-6-phosphate, is probably involved in the regulation of developmental and metabolic processes in plants.