Trehalose metabolism in sugar sensing and plant development

Trehalose (α-D-glucopyranosyl-[1,1]-α-D-glucopyranoside), a non-reducing disaccharide, is common in lower organisms such as bacteria, fungi and invertebrates. In higher plants, trehalose is generally not accumulated and is even considered to be toxic. Recently, genes for trehalose metabolism have, however, been identified in higher plants and characterized by expression studies and functional complementations of corresponding yeast mutants. Interestingly, data obtained from plants externally supplied with trehalose or from transgenic plants expressing trehalose biosynthesis genes from microorganisms point towards a role of trehalose, or intermediates of its metabolism, in sugar sensing and development. These findings may open up new perspectives for engineering the sugar sensing system in plants. Here, we discuss results concerning trehalose as a regulator of the carbohydrate allocation system of the plant and possible mechanisms by which trehalose might interfere with the sugar sensing mechanisms and other signal transduction pathways.