Coffee Genome Reveals Secrets of a Good Brew

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At last, the coffee genome has been sequenced, shedding light on genes responsible for the kick, flavor and aroma of the ever-popular beverage.

Not only will it help in breeding good quality naturally decaffeinated or extra strength coffee, but the sequence shows that caffeine molecule evolved separately in coffee, tea and cacao (cocoa), say researchers.

Their study is reported in today's issue of the journal Science.

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What's the hot new food "thing"? Buttered coffee, that's what. Or, that's the idea anyway.

More than 2.25 billion cups of coffee are consumed every day. The plant is grown on more than 11 million hectares, often in developing countries where it is an important cash crop.

"Many people argue it's the most traded commodity after oil," says molecular biologist Professor Robert Henry.

Henry is part of an international team of researchers that used advanced sequencing technology to look at the coffee bean genes that control flavour, aroma and caffeine content.

"We're trying to understand the genetic control of the composition of the bean and then subsequently how that influences the ultimate quality of the coffee," says Henry.

He and colleagues provide a draft genome of the Robusta coffee plant (Coffea canephora), which is a hardy species that provides 30 per cent of the world's coffee.

Robusta is a parent of the genetically more complex premium Arabica coffee (Coffea arabica), that provides most of the rest of the world's coffee.

The researchers found coffee has a high number of genes for N-methyltransferases, which are enzymes involved in caffeine synthesis.

However, the enzymes and biochemical pathway for producing caffeine in coffee are different to those in tea or cacao plants

"The interesting thing is that caffeine synthesis has evolved separately in each of the three plants," says Henry. "It's convergent evolution."

"Clearly caffeine is a particularly well-designed or biologically effective molecule if it has evolved independently at least three times," he adds.

Henry says caffeine is involved in the plant's defenses.

"Its bitterness might serve as a warning against some predators," he says.

The researchers also found genes for disease resistance, and genes for linoleic acid, which play a key role in aroma and flavor of coffee.

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Improving coffee

The genome sequence will provide a tool for rapidly locating new genes for breeding coffee that is more resistant to environmental stresses.

"We'd like to be able to extend the range over which we can grow coffee," says Henry.

For example, Arabica coffee is currently narrowly restricted to growing in certain high altitudes in the tropics. As the climate changes these growing areas could shrink even further and one idea is to breed Arabica coffee that can withstand a broader range of climates.

The findings could also help breed a less acidic Robusta coffee, naturally decaffeinated or extra strength coffee.

"This technology allows us to think about tuning coffee characteristics to a range of different market segments," says Henry, adding that the hunt is on for flavor-enhancing and other genes in wild relatives of coffee across Africa and in Australia.