Sugars are not only the major end-products of photosynthesis , and transported in storage in various plant organs but also perform regulatory functions. Changes in the concentration of sugars in the tissues interact on many metabolic processes : photosynthesis , respiration , protein synthesis , nitrogen economy , inhibiting or adding to their intensity . Changes in the sugar content also affect the expression of a number of genes . The accumulation of sugars in the tissue, usually leads to repression of genes encoding structural proteins and enzymes necessary for the process of photosynthesis , while a shortage of sugars enhances their expression . Genes encoding proteins associated with the enzymatic metabolism of sucrose ( sucrose synthase , invertase ) and enzymes involved in starch synthesis ( ADP- glucose pyrophosphorylase ) are induced by sucrose and glucose. This paper discussed the role of hexokinase and glucose and sucrose transporters in the perception and signal transduction of sugars in the cells of higher plants.