The effect of presumptive polyadenylation signals on the expression of the CAT gene in transgenic tobacco.

Promoter::gene fusions which differed only in the presumed polyadenylation signals attached to the 3' end of the gene, have been used to examine the effect of these signals on expression of the gene in protoplasts and in transgenic plants. The gene constructs were comprised of the 35S promoter, the chloramphenicol acetyl transferase (CAT) gene and DNA sequences carrying the presumed polyadenylation signals of the nopaline synthase (nos) gene or of transcript 7 (T-7) from the T-DNA ofAgrobacterium. Our results show that levels of gene expression were not significantly affected by the orientation or absence of these sequences. We therefore suggest that the practice of cloning presumptive polyadenylation sequences at the 3' end of a gene for expression in plants may be unnecessary.