A large team of scientists led by Dr Philippe Lashermes of the French Institute of Research for Development has generated a high-quality draft genome of Robusta coffee, scientifically known as Coffea canephora (syn. Coffea robusta).
Berries of Coffea canephora. Image credit: © 2010. Jeevan Jose, Kerala, India / CC BY-SA 4.0.
Coffea canephora – a species of flowering plant in the Rubiaceae family – has its origins in central and western sub-Saharan Africa.
Regarded as the lesser of the two main varieties of coffee, Coffea canephora accounts for about 30 percent of the world’s coffee production and is grown mostly for use in instant and blended coffees.
It has a greater crop yield than that of Coffea arabica, and contains more caffeine – 2.7 percent compared to C. arabica‘s 1.5 percent.
In their research, Dr Lashermes and his colleagues generated a draft genome of Coffea canephora and looked at how it is distinct from other plant species.
“By looking at the coffee genome and genes specific to coffee, we were able to draw some conclusions about what makes coffee special,” said Dr Lashermes, who is the senior author of a paper published in the journal Science.
Compared to several other plant species including the grape and tomato, Coffea canephora harbors larger families of genes that relate to the production of alkaloid and flavonoid compounds, which contribute to qualities such as coffee aroma and the bitterness of beans. It also has an expanded collection of N-methyltransferases, enzymes that are involved in making caffeine.
Upon taking a closer look, the team found that Coffea canephora‘s caffeine enzymes are more closely related to other genes within the plant than to caffeine enzymes in tea and chocolate. This finding suggests that caffeine production developed independently in coffee. If this trait had been inherited from a common ancestor, the enzymes would have been more similar between species.
“It turns out that, over evolutionary time, the coffee genome wasn’t triplicated as in its relatives: the tomato and chili pepper. Instead it maintained a structure similar to the grape’s. As such, evolutionary diversification of the coffee genome was likely more driven by duplications in particular gene families as opposed to en masse, when all genes in the genome duplicate,” explained co-author Dr Patrick Wincker of the French National Sequencing Center.
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France Denoeud et al. 2014. The coffee genome provides insight into the convergent evolution of caffeine biosynthesis. Science, vol. 345, no. 6201, pp. 1181-1184; doi: 10.1126/science.1255274
