Silencing nature's narcotics: metabolic engineering of the opium poppy.

The opium poppy, Papaver somniferum L., and its narcotic and analgesic alkaloids, have an ancient history of use (and abuse) by humankind. A recent article by Allen and co-workers describes the metabolic engineering of morphine biosynthesis to block morphine formation and accumulate a potentially valuable pathway intermediate, (S)-reticuline. This work highlights the potential for modifying the production of pharmaceuticals in plants, but also raises questions about the complex regulation of biosynthetic pathways.