Abstract
Transgenic plants exhibit various levels of expression of the transgene, believed to be due to "positional effects". We hypothesize that long sequences flanking to a transgene stabilize expression of the gene in plants. According to the hypothesis, we introduced the reporter gene GUS between flanking sequences of 32 kb and 41 kb derived from Arabidopsis thaliana in the binary vector Transformation-competent Artificial Chromosome (TAC). Without the long flanking sequences, many transgenic Arabidopsis exhibited gene silencing, that was evident in the presence of small RNA species (20-25 nt) detected by the transgene probe. On the other hand, a few transgenic plants carrying the transgene with the flanking sequences exhibited gene silencing only when multiple insertion of the transgene on a chromosome(s) occurred. These results indicate that the flanking sequences suppress gene silencing of the transgene. The long flanking sequences also facilitated production of transgenic plants carrying only a single transgene.
