The expression of a chimeric soybean beta-tubulin gene in tobacco

A chimeric tubulin gene has been constructed by the fusion of a genomic sequence containing a truncated soybean beta-tubulin gene with 2 kb of upstream DNA to the 3′ untranslated region containing the polyadenylation signal from transcription unit 7 of the octopine Ti plasmid pGV117. The chimeric gene has been incorporated into the Ti plasmid transformation vector pGV3850::pAP2034, along with a selectable marker gene active in plants (the neomycin phosphotransferase II gene, conferring kanamycin resistance). Strains of Agrobacterium tumefaciens haboring the plasmids were used to transform Nicotiana tabacum by the leaf disk method and plants were regenerated from transformed cells. Transgenic plants were self fertilized and the segregation of kanamycin resistance was assayed. DNA and RNA were extracted from transgenic plants, fractionated by agarose gel electrophoresis, blotted to nitrocellulose and hybridized to a probe specific for the chimeric gene to assess its structure and expression in transgenic plants. The chimeric gene was stably integrated into the tobacco genome without rearrangements and it was expressed as a polyadenylated RNA of 1.7 kb in the transformants. Genetic analysis revealed that the kanamycin-resistant phenotype was inherited in a Mendelian fashion over two generations.