Genes involved in coffee quality have been identified

To maintain their incomes, growers are increasingly banking on producing quality coffee. However, improving coffee beverage quality means knowing more about the biological processes - flowering, fruit ripening, etc - that determine end product characteristics.

Since 2001, CIRAD and the Agricultural Institute of Paraná in Brazil (IAPAR) have been working on joint research into how coffee beans ripen. They have characterized the key enzymes in the sucrose metabolism during coffee bean development. The researchers involved used molecular biology and biochemistry techniques in their work, supported by the University of Campinas in Brazil (Unicamp).

Their work showed that an enzyme, sucrose synthetase, is responsible for sucrose accumulation in coffee (Coffea arabica) beans. Unlike in other plants, invertases play only a minor role in this metabolism. Sucrose synthetase exists in the form of at least two similar proteins with the same biological function - isoforms -, but which are coded by two different genes: SUS1 and SUS2.

Expression of those genes was analysed within the various tissues of developing coffee beans (pulp, perisperm and endosperm). The results showed that sucrose accumulation in coffee beans, towards the end of ripening and just before picking, is controlled by isoform SUS2. Isoform SUS1, for its part, seems to be involved in sucrose breakdown and thus in energy production. In effect, its expression is systematically detected during the early stages of cell division and expansion in young tissues.

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