Cellular localization of tyrosine decarboxylase expression in transgenic opium poppy and tobacco

Opium poppy, Papaver somniferum, is cultivated for its alkaloid-rich latex. Tyrosine decarboxylase (TyDC) is the first enzyme in poppy alkaloid biosynthesis and is encoded by a small gene family. A 2,060-bp promoter fragment of TyDC5 was translationally fused to the P-glucuronidase (GUS) reporter gene and introduced into poppy and tobacco (Nicotiana tabacum). Transgenic seedlings were stained for GUS activity which localized to the xylem parenchyma in the shoots of poppy and tobacco. Roots of both species had similar expression patterns with staining in the vascular cylinder surrounding the xylem. No staining was observed in poppy laticifers suggesting, that other TyDC genes may be expressed in latex or that alkaloid precursors are supplied to laticifers by adjacent cells.