Espresso, filtered, Turkish-style or otherwise, more than two billion cups of coffee are consumed each day in the world! This makes it one of the main international export goods, and the prime asset of many tropical countries. And yet, the coffee plant genome remained unsequenced. An international consortium coordinated by the IRD, the CEA (IG-Genoscope), CIRAD and the University of Buffalo has just remedied this by publishing the reference sequence of Coffea canephora, better known under the name of robusta.
This species was chosen for its diploid genome (2 x 11 chromosomes), whereas C. arabica, the other cultivated species, is a hybrid tetraploid (4x 11 chromosomes) of robusta and C. eugenioides. Combining several sequencing technologies, the researchers deciphered the 710 million base pairs of its DNA and identified more than 25,000 genes. A comparative analysis revealed that this genome has conserved an organization very close to that of the ancestor of all true dicotyledons1 (or eudicotyledons).
The researchers also found that the coffee plant is distinguished by a relatively high number of genes devoted to defense and secondary metabolism2. Caffeine, in particular, is synthesized by enzymes other than those found in the cocoa and tea plants. This molecule therefore emerged at two different time points (at least), during the evolution of eudicotyledons.
The identification of genes of agronomic interest should help in selecting or creating varieties that are more resistant to environmental stresses and aggressors (insects, fungi, viruses, etc.). The full results are available to the scientific community on a public database developed by the IRD and Cirad3.
1 Flowering plants in which the seedlings have two cotyledons (lobes).
2 Present mainly in plants, secondary metabolites are not involved in nutrition (and therefore not in the development of the organism).
3 See: http://coffee-genome.org/