INDUCING GENE SILENCING USING A CONSTRUCT CAPABLE OF TRANSCRIPTION FROM BOTH DIRECTIONS

A DNA fragment of a Potato leaf roll virus full-length cDNA (part of the virus replicase gene) was amplified by PCR. The resulting fragment was inserted as a sense fragment into a vector flanked by a promoter at both sides. Tobacco and potato plants were transformed with this construct. The resulting transgenic plants were tested for resistance to PLRV. Fifty-nine percent of the transgenic tobacco lines showed lower titer of PLRV. It was also shown that the resistant transgenic tobacco lines express both sense and antisense mRNAs of the transgene. Using graft-inoculation method, no PLRV resistant transgenic potato line was identified. This is the first report of testing a single construct capable of expressing mRNA from both directions. It seems that the simultaneous expression of sense and antisense mRNA followed by hybridization and dsRNA formation have triggered post transcriptional gene silencing in transgenic tobacco lines.