COVER: The opium poppy, Papaver somniferum, produces a diverse array of pharmaceutical alkaloids, including the narcotic analgesics morphine and codeine. These alkaloids accumulate in the cytoplasm, or latex, of specialized laticifers that accompany vascular tissues throughout the plant, and the latex has long been considered the site of alkaloid synthesis. On pages 2626–2635, Bird et al. use immunofluorescence labeling to show that three key enzymes involved in the alkaloid biosynthesis are localized to sieve elements proximal to laticifers, whereas their corresponding gene transcripts are found in adjacent companion cells. These results extend the function of sieve elements in this species beyond that of the transport of solutes and other macromolecules to the biosynthesis and accumulation of alkaloids. Remarkably, the overall process from gene expression through product accumulation involves the services of three unusual cell types and predicts the intercellular translocation of biosynthetic enzymes and various alkaloids. The cover image shows a close-up view of carpels and stamens of an opium poppy flower.