Citrus sinensis produces caffeine in its flowersWIKIMEDIA, ELLEN LEVY FINCHPlant species belonging to divergent branches of the evolutionary tree are known to have independently evolved caffeine production. According to scientists at Western Michigan University, caffeine-producing plants have taken a number of different biochemical routes to synthesize the stimulant. Coffee, tea, cocoa, orange, and guaraná plants make caffeine using an array of enzymes and substrates, the researchers reported in PNAS this week (September 20).
“This is a very nice article that illustrates the multiplicity of adaptive pathways utilized in biochemical evolution,” said evolutionary biologist Michael Clegg of the University of California, Irvine, who was not involved in the study.
Caffeine is produced by approximately 30 of the world’s 300,000 or so different species of flowering plants, estimated Todd Barkman of Western Michigan, who led the new study. The divergent nature of these species and of the functions the molecule performs—attracting pollinators, deterring pests, and more—has indicated that caffeine production independently evolved multiple times, Barkman said.
Indeed, studies have shown that coffee (Coffea arabica) and tea (Camellia sinensis) use different enzymes to generate caffeine—xanthine methyltransferases (XMT) and caffeine synthases (CS), respectively. Furthermore, comparisons of the coffee genome (Coffea canephora) to ...
