Construction of a vector conferring herbicide and pest resistance in tobacco plant

A binary plant expression vector, pCM12_slm, carrying the aroAM 12 mutant gene encoding bacterial 5_enolpyruvylshikimate_3_phosphate synthase (EPSPS) and the Bts1m recombinant gene consisting of 331 N_terminal amino acids of CryIAc and 284 C_terminal amino acids of CryIAb has been constructed. The truncated Bts1 gene was fused with the PR1b signal peptide sequence and expressed in tobacco plants under the control of 2E_CaMV35S promoter and the omega(Ω) translation enhancer sequence from tobacco mosaic virus. The mutant aroAM 12 was fused with the transit sequence of tobacco EPSPS and expressed in tobacco plants under the control of the CaMV35S promoter. Tobacco leaves were transformed with \%Agrobacterium tumefaciens\% LBA4404 harboring the pCM12_slm plasmid, and the transgenic plants were selected directly on medium containing the herbicide. Forty glyphosate resistant plants were regenerated, with a transformation frequency of 27%. Transgenic plants were initially assessed for glyphosate resistance by placing leaf discs on shoot induction media containing the herbicide. Rooted plantlets, propagated from selected transgenic tobacco, were transferred to soil in a greenhouse and tested for glyphosate resistance by spraying them with Roundup at a commercial recommended dose. The glyphosate resistance assay indicated that all the transgenic plants showed highly resistant to the herbicide. The PCR assay showed that the \%aroAM12\% gene was present in all of the 40 T\-0 transfer plants, and \%Bts1m\% genes present in 28 of 40 of the transgenic plants. Southern blot analysis further confirmed that the copy number of the transgenes varied from one to three copies in different transgenic plants. Northern blot and immunodot blot showed that the aroAM 12 and Bts1m genes were expressed at the transcription and translation levels. Transgenic plants containing both the aroA M12 and Bts1m genes were further assessed for insect resistance. Tobacco leaves of T\-0 transgenic plants were infested with tobacco bollworm H. assulta larvae for 6 days. The result(table 1) showed that the survival rate of insect larvae was between 0～10%, and the growth of insect larvae was seriously inhibited, suggesting pCM12_slm as a dual functional vector with potential application in breeding of glyphosate and insect resistance transgenic plants.