Expression of genes in transgenic plants from bicistronic transcriptional units

Bicistronic mRNAs encoding either the potato virus Y (PVY) coat protein or the Bacillus thuringiensis CryIC protein followed by the selectable marker gene neomycin phosphotransferase II (nptII) were introduced by electroporation into tobacco protoplasts. The initiation codon for the nptII gene was located 44 or 39 nucleotides downstream of the termination codon of the PVY coat protein or B. thuringiensis cryIC gene, respectively. Plants selected using paromomycin (50 mu g/ml) were shown to express the PVY coat protein by Western blot analysis or the B. thuringiensis CryIC protein by an insect feeding bioassay. Transgenic plants were shown, by Northern analysis, to produce transcripts of either construct without rearrangement. A significantly reduced level of nptII activity was demonstrated in transgenic seedlings of the T1 and T2 generation either by germination on agar containing 75 mu g/ml kanamycin or by nptII activity assays. These results demonstrate that transgenes of interest can be expressed from a bicistronic transcriptional unit and that plants expressing the transgene can be selected by monitoring for activity of a distal marker gene. (C) 1997 Elsevier Science Ireland Ltd.