13th September 2014

The coffee genome is sequenced

The coffee genome has been published, with more than 25,000 genes identified. This reveals that coffee plants make caffeine using a different set of genes from those found in tea, cacao and other such plants. The new findings could help to improve coffee production in the future.

Researchers have published the genome of Coffea canephora, a plant which accounts for about 30 percent of the world's coffee production. By comparing the sequences and positions of genes in coffee, tea and cacao (chocolate) plants, they have shown how enzymes involved in producing caffeine likely evolved independently in each of these three organisms. In other words, coffee did not inherit caffeine-linked genes from a shared common ancestor – but instead developed the genes on its own.

Compared to several other plant species – including the grape and tomato – coffee has larger families of genes that relate to the production of alkaloid and flavonoid compounds, which contribute to qualities such as aroma and bitterness. Coffee also has an expanded collection of N-methyltransferases, enzymes that are involved in making caffeine.

Upon taking a closer look, the researchers found that coffee's caffeine enzymes are more closely related to other genes within the coffee plant than to caffeine enzymes in tea and chocolate. This provides evidence that caffeine production emerged independently in coffee. If this trait had been inherited from a shared common ancestor, the enzymes would have been more similar between species.

There are several possible reasons why caffeine is so important in nature. The chemical may help to deter pests, as well as nearby competitors by stunting their growth when coffee leaves fall on the soil. It may also facilitate pollination. One recent paper showed that – like humans – certain insects can develop caffeine addiction. Bees visiting caffeine-producing plants often returned to get another taste.

Worldwide, over 2.2 billion cups of coffee are consumed daily. It is the principal agricultural product of many tropical countries. According to estimates by the International Coffee Organisation, more than 8.7 million tons of coffee is produced each year from 110,000 sq km (42,500 sq mi) of land – an area equivalent in size to the U.S. state of Pennsylvania. Annual export revenue is $15.4 billion and the sector employs 26 million people in 52 countries.

Philippe Lashermes, at the French Institute of Research for Development: "Coffee is as important to everyday early risers as it is to the global economy. Accordingly, a genome sequence could be a significant step toward improving coffee."

In addition to new and exotic flavours, these improvements may include better resistance to drought and disease. Leaf rust, for example, is currently affecting about half the plants in Central America, in the worst outbreak since 1976. Scientists could also engineer the plants to grow faster and increase their output of coffee beans. Such genetic enhancements may prove vital in the future – a study in 2012 estimated that climate change alone will lead to the extinction of wild Arabica coffee (Coffea arabica) by the 2080s.

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