The classic model for explaining the biosynthesis of starch in plant leaves has been seriously called in to question. While to date the accepted belief has been that starch biosynthesis is produced solely in the chloroplast, biologist Nora Alonso Casajs' PhD provides evidence to show that the greatest part of the precursor molecule in starch biosynthesis known as ADPG accumulates in the cytosol of the plants. This finding has meant a great advance in the race to obtain vegetables that can produce large quantities of starch, a substance the annual production of which is about a thousand million tonnes and which has become an essential raw material in multiple sectors of modern industry such as biofuels or biodegradable plastics.

The thesis, entitled, Factors involved in the regulation of starch and glycogen production in plants and bacteria was recently defended the Public University of Navarra's Institute of Agrobiotechnology.

Biosynthesis of starch

According to the classical model for explaining the biosynthesis of starch, sucrose and starch are final products of two unidirectional routes that take place in the cytosol and the chloroplast respectively. Moreover, this model takes it that the ADPglucose pyrophosphorylase (AGP) is the only enzyme responsible for the biosynthesis of the starch precursor, ADPglucose (ADPG). Over the last few years there have been numerous indications suggesting the involvement of another enzyme, sucrose syntase (SuSy), in the production of the cytosolic ADPG needed for the synthesis of starch.

To analyse which of the models was the correct one this biologist determined the subcellular location of the ADPG linked to the starch biosynthesis, the tool used being plants that superexpress bacterial ADPG hydrolase, both in the cytosol and in the chloroplast.
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Contact: Garazi Andonegi
garazi@elhuyar.com
+34-94-336-3040
Elhuyar Fundazioa
21-Oct-2005