Research areas

Starch is the fundamental form of energy storage in many species of plants and constitutes an essential element in the diet of human beings. It is particularly abundant in organisms such as cereals and tubers and is the fundamental raw material in a large number of industrial processes such as the production of adhesives, paints, biodegradable plastics, biofuels etc.

Starch is a polysaccharide of glucose molecules joined covalently which is stored in the organelle known as a plastid. For over fifty years it has been accepted that ADPglucose pyrophosphorylase is the only enzyme capable of producing the ADPglucose necessary for the biosynthesis of glucose in plants.

Nevertheless our team has demonstrated that a cytosolic enzyme, sucrose synthase, is responsible for the synthesis of the major part of ADPglucose which is accumulated in plant cells. (Baroja-Fernández et al. 2003, Plant Cell Physiol. 44, 500-509; Proc. Natl. Acad. Sci. USA. 101, 13080-13085; Trends Plant Sci. 10, 156-158; Muñoz et al. 2005, Plant Cell Physiol. 46, 1366-1376).

Furthermore we have established for the first time the existence of mechanisms of endocytic uptake of the sucrose necessary for the production of starch.

Currently we are identifying and using molecular tools that enable us to control levels of intermediary molecules in the process of starch biosynthesis. We are also researching the molecular basis of the endocytic uptake of sucrose. With information acquired, plants will be designed with high starch content.

Glycogen metabolism in bacteria

Glycogen is the principal form of energy stored in many species of bacteria. Similarly to starch storage in plants, bacterial glycogen is a homopolysaccharide of glucose molecules. As with plants it has traditionally been accepted that ADPglucose pyrophosphorylase is the only enzyme capable of producing the ADPglucose necessary for the biosynthesis of glycogen.

However, our team has accumulated evidence about the existence of other important sources of ADPglucose.

Furthermore we have discovered the existence of the enzymes involved in the control of intracellular levels of ADPglucose. (Moreno-Bruna et al. 2001, Proc. Natl. Acad. Sci. USA 98, 8128-8132).

We are currently working on the identification of these sources of ADPglucose and on the mechanism of glycogen breakdown. The information acquired from bacteria can be used to obtain varieties of plants that have a high starch content.