Convergent evolution of caffeine in plants by co-option of exapted ancestral enzymes

Significance Convergent evolution is responsible for generating similar traits in unrelated organisms, such as wings that allow flight in birds and bats. In plants, one of the most prominent examples of convergence is that of caffeine production, which has independently evolved in numerous species. In this study, we reveal that even though the caffeine molecule is identical in the cacao, citrus, guaraná, coffee, and tea lineages, it is produced by different, previously unknown, biosynthetic pathways. Furthermore, by resurrecting extinct enzymes that ancient plants once possessed, we show that the novel pathways would have evolved rapidly because the ancestral enzymes were co-opted from previous biochemical roles to those of caffeine biosynthesis for which they were already primed.