EXPRESSION OF GENES IN TRANSGENIC PLANTS FROM BICISTRONIC TRANSCRIPTIONAL UNITS

Bicistronic mRNAs encoding either the potato virus Y (PVY) coat protei n or the Bacillus thuringiensis CryIC protein followed by the selectab le 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 term ination codon of the PVY coat protein or B. thuringiensis cryIC gene, respectively. Plants selected using paromomycin (50 mu g/ml) were show n to express the PVY coat protein by Western blot analysis or the B. t huringiensis CryIC protein by an insect feeding bioassay. Transgenic p lants were shown, by Northern analysis, to produce transcripts of eith er construct without rearrangement. A significantly reduced level of n ptII activity was demonstrated in transgenic seedlings of the T1 and T 2 generation either by germination on agar containing 75 mu g/ml kanam ycin or by nptII activity assays. These results demonstrate that trans genes of interest can be expressed from a bicistronic transcriptional unit and that plants expressing the transgene can be selected by monit oring for activity of a distal marker gene. (C) 1997 Elsevier Science Ireland Ltd.