How does the sugar get into the beet? This question has been investigated by researchers at FAU’s Division of Molecular Plant Physiology in collaboration with colleagues from the universities of Kaiserslautern, Cologne and Würzburg, and the companies Südzucker AG and KWS Saat AG. They have discovered a previously unknown mechanism which could be used to increase the sugar content of sugar beet in the future. The researchers’ findings have recently been published in the journal Nature Plants. (DOI: 10.1038/nplants.2014.1)
Alongside sugarcane, sugar beet – the scientific name of which is Beta vulgaris – is the most important crop that sugar can be extracted from. Its white root can also be used to produce ethanol, a type of biofuel. Sugar beet is therefore a rich source of energy and around one fifth of a high-quality, fresh sugar beet cultivated using conventional methods can consist of sugar. This makes sugar beet an important economic factor for rural areas.
Stimulated by energy from sunlight, sugar beet’s green leaves convert carbon dioxide in the air and water from the soil into sucrose. The plant stores this sugar as an energy reserve in its root. However, until recently, researchers were not able to explain what happens on a molecular level when a sugar beet fills its enormous sugar store. The FAU researchers and their colleagues spent three years investigating this phenomenon. Their work was funded by the Federal Ministry of Education and Research.
Protein controls sugar transport
The researchers discovered a previously unknown protein that transports the sugar to the vacuoles in the sugar beet’s cells. Vacuoles are an important organelle found in all plant cells. In sugar beet’s cells they function as powerful stores which absorb the sugar during the first year of growth. When sugar beet is processed the sugar is released from these cells and then crystallised when the water is made to evaporate. The researchers were able to identify and characterise the molecular structure of the protein that transports the sugar to the stores.
Their goal now is to cultivate sugar beet which produces more of this protein, enabling it to store larger quantities of sugar. ‘This would allow farmers to use agricultural land much more effectively and provide more sugar and raw material for biofuels,’ says FAU biologist Dr. Petra Wirsching.