AmABCB1, an alkaloid transporter from seeds of Argemone mexicana L (Papaveraceae).

MAIN CONCLUSION: An ABCB-type transporter for sanguinarine, a benzophenanthridine alkaloid, was isolated from Argemone mexicana seeds. An ABCB-type transporter, AmABCB1, was identified in a transcriptome from unfolding seedlings of A. mexicana by its amino acid sequence identity to previously characterized alkaloid transporters from Coptis japonica and Thalictrum minus. Expression analysis revealed mature seeds as its main location; meanwhile, in vitro assays in yeast cells showed that AmABCB1 had uptake and efflux activities for sanguinarine and berberine, respectively.

Production of prenylated flavonoids in tomato fruits expressing a prenyltransferase gene from Streptomyces coelicolor A3(2).

Flavonoids are natural compounds found in many plants, including the important fruit crop, tomato. Prenylated flavonoids consist of a large group of compounds, which often exhibit antitumour, antibacterial and/or anti-androgen activities. In this study, we engineered the biosynthesis of prenylated flavonoids using a Streptomyces prenyltransferase HypSc (SCO7190) possessing broad-range substrate specificity, in tomato as a host plant. LC/MS/MS analysis demonstrated the generation of 3'-dimethylallyl naringenin in tomato fruits when recombinant HypSc protein was targeted to the plastids, whereas the recombinant protein hardly produced this compound in vitro. This is the first report confirming the accumulation of a prenylated flavonoid using a bacterial prenyltransferase in transgenic plants, and our results suggest that the product specificities of prenyltransferases can be significantly influenced by the host plant.

Accumulation and membrane transport of plant alkaloids.

Among a large number of plant secondary metabolites, alkaloids comprise one of the most important groups due to their strong and divergent biological activities, and some are applied for clinical use. Alkaloids are often highly accumulated in particular organs of medicinal plants, which are called the 'medicinal part', whereas it is known that some alkaloids are translocated from source organs to such sink organs. The movement of biosynthetic intermediates from specific cells to other types of cells in tissue, and further detailed movement within the organelles in a cell is also suggested. However, little is known how alkaloids are transported across membranes and finally accumulated in specific organelles such as vacuole of the sink organ. To increase the productivity of valuable alkaloids in planta, not only biosynthetic genes of alkaloids but also genes involved in their transport will be important. Recently, the involvement of ABC transporters in the translocation of berberine alkaloid from root to rhizome was reported, while H(+) antiporters were also suggested as the responsible transporters for vacuolar accumulation of the alkaloid. In this review, we describe intra-organ, intra-tissue and intra-cellular transport of the alkaloid via membrane transports. Furthermore, we discuss the possibility of increasing alkaloid production in transgenic plants by using alkaloid transporter genes.

A novel Coptis japonica multidrug-resistant protein preferentially expressed in the alkaloid-accumulating rhizome.

A full-length cDNA, Cjmdr1, which belongs to the multidrug-resistant (mdr) gene family, was isolated by nested RT-PCR from alkaloid-producing cultured cells of Coptis japonica. The cDNA is 4192 nucleotides long and has an ORF of 1289 amino acids. Northern analysis of the intact plant showed a clear preference in its expression in the rhizome, where alkaloids are highly accumulated compared to other organs.