Alkaloid Synthetic Pathway Noscapine, a nonaddictive alkaloid found in the opium poppy, can be used as a cough suppressant and a tubulin-binding antitumor agent. Winzer et al. (p. 1704 , published online 31 May; see the Perspective by DellaPenna and O'Connor ) found that a cluster of 10 genes were key to the production of noscapine. Poppies homozygous for this gene cluster produced high levels of noscapine, heterozygous poppies produced low levels of noscapine, and those poppies lacking the gene cluster produced no noscapine. Silencing individual genes in turn and analyzing the accumulation of intermediate metabolites allowed the biosynthetic pathway of noscapine to be elucidated.