TRANSFER RNA-MEDIATED SUPPRESSION OF AMBER STOP CODONS IN TRANSGENIC ARABIDOPSIS-THALIANA

An artificial amber suppressor tRNA(Leu) gene (supL) was physically li nked to a mutated gus reporter gene, p35S-gus(aml), which was inactiva ted by an amber stop codon (amL). Upon introduction into Arabidopsis t haliana, the presence of the supL gene was found to be correlated with cytotoxic effects observed during tissue culture and in mature plants . Those primary transformants that displayed cytotoxic symptoms were s hown by X-Gluc staining to express GUS as a result of amber stop codon suppression in vivo. Phenotypically normal lines were found by RT-PCR to express supL. GUS activity above background level was barely detec table in these plants, indicating a low level expression of supL. Howe ver, the remaining suppressor activity was still sufficient to transac tivate an amber-mutated male sterility gene, pA9-barnase(amL1) when co mbined within the same plant by crossing. The suppressor tRNA(Leu) gen e may thus be used in transgenic plants for gene transactivation.