Transactivation of a target gene using a suppressor tRNA in transgenic tobacco plants.

The abundance of tRNAs, together with their central role in translation, has generated considerable interest in the use of tRNA genes for biotechnological applications. One such application is the use of suppressor tRNAs to transactive target genes containing premature stop codons. Previous work has shown that such systems can work in transient expression experiments in plant protoplasts; here these experiments are extended to show that suppression of stop codons can occur in whole plants. Transgenic tobacco plants homozygous for a modified tRNA(Leu) gene expressing a strong amber suppressor tRNA, and plants carrying a beta-glucuronidase (gus) gene inactivated by a premature amber stop codon have been obtained. When the two types of plants are crossed, many of the F1 hybrids show significant GUS activity. The GUS activity is dependent on the presence of both the suppressor tRNA gene and the gus gene. Tobacco plants carrying the suppressor tRNA gene are phenotypically normal, fertile and the gene shows normal Menedelian inheritance. The potential applications of such a system are discussed.