Coffea humblotiana: A Rare, Naturally Decaffeinated Coffee Species

 

The Humblot coffee tree, native to the Comoros archipelago, produces naturally decaffeinated seeds. To understand the absence of caffeine, the UMR DIADE, Nestlé Research Center in Switzerland, and an international team of botanists, biologists, bioinformaticians, and biochemists sequenced its genome and identified the mechanisms involved.

 

There are over 124 species of coffee trees. Only three are currently cultivated (C. arabica, C. canephora and C. liberica), while more than a dozen wild species previously consumed have been abandoned. Among them, the Humblot coffee tree lacks caffeine.

 

A Missing Gene Changes Everything!

To understand the absence of caffeine in the Humblot coffee tree, an interdisciplinary and international approach was implemented in collaboration with Nestlé Research, bringing together researchers from fundamental and applied research institutes.This collaboration enabled, through high-quality sequencing, the assembly and annotation of the C. humblotiana genome, identifying 32,874 genes. Among them, a family of genes called N-methyltransferases, involved in caffeine biosynthesis, was identified.The products of these genes function to successively transfer methyl groups from xanthosine as a precursor, resulting in caffeine synthesis in four steps.However, in the Humblot coffee tree, the last gene in this pathway, responsible for adding a methyl group to theobromine, has completely disappeared, along with a small portion of the chromosome that carries it! The absence of this gene is sufficient to block caffeine synthesis without causing an accumulation of theobromine, a bitter compound found in cocoa seeds.

 

An Essential Step Towards Naturally Decaffeinated Cultivation

Other wild coffee species, also devoid of caffeine and theobromine, need to be analyzed to compare the molecular mechanisms involved. However, the discovery of this biochemical process in the Humblot coffee tree is already a crucial step: this fundamental knowledge will be utilized to develop naturally decaffeinated coffee.Moreover, these efforts should promote the protection and conservation of wild coffee species, which offer original solutions to challenges such as climate change or disease tolerance.

 

*Publication: Raharimalala, N., Rombauts, S., McCarthy, A. et al. The absence of the caffeine synthase gene is involved in the naturally decaffeinated status of Coffea humblotiana, a wild species from the Comoros archipelago. Sci Rep 11, 8119 (2021). https://doi.org/10.1038/s41598-021-87419-0*

*This article was written as part of the Planet@liment project.*

 

Original publication: Coffea humblotiana: https://www.ird.fr/les-secrets-dun-cafe-sauvage-naturellement-decafeine