Maize sucrose synthase-1 promoter directs phloem cell-specific expression of Gus gene in transgenic tobacco plants.

Tobacco plants were transformed by using a chimeric gene construction, in which a corn sucrose synthase-1 gene (Sh) promoter was used to direct expression of the beta-glucuronidase (Gus) reporter gene. Expression of Sh-Gus activity in these plants was found to be cell type specfifc. GUS activity was detected only in the phloem cells but not in any other cell types of vegetative tissues. In addition, Sh-Gus expression was found to be anaerobically inducible in tobacco roots. Sh-Gus was also expressed at high levels in the endosperm tissue of maturing tobacco seeds. We thus demonstrated that the corn Sh promoter can direct cell-type-specific and inducible expression in a heterologous dicotyledonous plant.