It is disclosed that a promoter region that drives expression of a 1450 base TR transcript in octopine-type crown gall tumors can also promote expression of a foreign structural gene in bacteria. Use of this dual-purpose promoter region to drive expression of a single copy of a foreign structural gene in both plants and bacteria is taught. The construction of a selectable marker functional in eukaryotes and prokaryotes is exemplified, as are vectors useful in efforts to transform plants.
