Papaver species are known to produce a large variety of benzylisoquinoline alkaloids, with each species exhibiting a specific alkaloid profile, but only a few genes involved in the biosynthesis or regulation of these complex pathways are known so far. Here we used a genomic approach to discover genes responsible for the determination of a specific alkaloid profile. A stem expressed sequence tag database of ~1100 unique genes from Papaver somniferum was created. Gene expression analysis of these sequences in P. bracteatum, P. somniferum and P. somniferum ‘Noscapine’ exhibited 39 cDNAs showing differential expression coincident with morphine accumulation.

Isoquinoline alkaloids are a large class of compounds derived from the amino acid L-tyrosine containing many physiologically active members. Among the isoquinoline alkaloids, morphine is one of the pharmaceutically important members that is still derived from the plant that produces it, the opium poppy Papaver somniferum. P. somniferum produces over 80 alkaloids derived from L-tyrosine. We have isolated cDNAs encoding several enzymes of tetrahydrobenzylisoquinoline-derived alkaloid biosynthesis from this plant. The first enzyme in the biosynthetic pathway for which we have isolated a cDNA is norcoclaurine 6-O-methyltransferase. The next is the cytochrome P-450-dependent monooxygenase (S)-N-methylcoclaurine 3’-hydroxylase. These enzymes are common to the morphine, noscapine and sanguinarine biosynthetic pathways. Specific to the sanguinarine pathway is the berberine bridge enzyme that oxidatively cyclizes the N-methyl moiety of (S)-reticuline to the bridge carbon C-8 of (S)-scoulerine. Finally, specific to morphine biosynthesis are salutaridinol 7-O-acetyltransferase and codeinone reductase the penultimate enzyme of the morphine pathway that reduces codeinone to codeine. Given the number of cDNAs specific to various alkaloid biosynthetic pathways that we now have, attempts at metabolic engineering of P. somniferum can be made. We describe herein details of the isolation and biochemical characterization of a cDNA encoding the P. somniferum O-methyltransferase OMTPS3.

Opium poppy (Papaver somniferum L.) produces a large variety of isoquinoline alkaloids. The aim of this investigation is to understand the regulation of biosynthesis and the ecological function of the alkaloids in the plant. Agrobacterium-mediated transformations of opium poppy were used to introduce the berberine bridge enzyme cDNA bbe 1 in the antisense orientation into seedling explants. After induction of callus on an appropriate medium, embryos were developed via somatic embryogenesis. After the embryos were developed into plantlets with leaves and roots they were transferred to soil. In this way, forty-nine phenotypically normal T0 plants were produced. Forty-six plants produced viable seeds and were used to produce T1 plants. These plants were then analyzed for the presence of the bbe 1 transgene and for the content of alkaloid in latex and root. Selected plants showed a differential alkaloid pattern in latex compared to the wild type. In this paper, the results of a plant with an altered alkaloid profile, heritable at least to the T2 generation, is presented. This represents the first example of metabolic engineering of the alkaloid pathways in opium poppy.