Abstract: Adding at least one gene involved in plant host cell T-DNA integration enhances transformation by Agrobacterium. The histone H2A gene encoded by the Arabidopsis RAT5 gene increases transformation frequencies of plants, most likely by causing overexpression of a product needed for T-DNA integration. Agrobacterium tumefaciens genetically transforms plant cells by transferring a portion of the bacterial Ti-plasmid, designated the T-DNA, to the plant, and integrating the T-DNA into the plant genome. However, not all plants are transformable by Agrobacterium and transformation frequencies may be too low to be useful. Little is known about the T-DNA integration process, and no plant genes involved in integration have been identified prior to the present invention.

Abstract: Chimeric regulatory regions and gene cassettes based upon Agrobacterium tumefaciens opine sythase genes are provided for expressing foreign genes in plants. Various upstream activating sequences from opine synthase genes like the mannopine synthase and the octopine synthase genes are operably linked with promoters (or promoters plus activating sequences), both of which are then operably linked to the foreign gene. These regions and cassettes permit expression levels and patterns that could not be obtained previously.

Abstract: Transcription of the vir genes of the Ti-plasmid in Agrobacterium species, typically induced by phenolic compounds secreted by wounded plant cells, is enhanced when induction is carried out in the presence of effective amounts of an opine from the Octopine Family of Nopaline Family. Production of T-strands in Agrobacterium species can be potentiated by induction preferably in the presence of octopine, nopaline, succinamopine, or leucinopine. Agrobacterium species induced in the presence of an opine compound of the Nopaline or Octopine Family effect highly efficient transformation of even recalcitrant plant species.

Abstract: A promoter region that drives expression of a 1450 base T.sub.R transcript in octopine-type crown gall tumors can also promote expression of a foreign structural gene in bacteria. Use of this dul-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.