TRANSFORMATION OF JAPANESE POTATO CULTIVARS WITH THE BETA-GLUCURONIDASE GENE FUSED WITH THE PROMOTER OF THE PATHOGENESIS-RELATED 1A-PROTEIN GENE OF TOBACCO

A fragment of the pathogenesis-related protein 1a (PR1a) gene of tobacco was introduced into Japanese potato cultivars by Agro-bacterium-mediated gene transfer using the binary vector system. A PR1a promoter beta-glucuronidase (GUS) fusion gene was used to study the expression of the gene after salicylic acid treatment. Transformed shoots were recovered from tuber discs using a kanamycin resistant gene as a selective marker. Transformants were obtained from 11 cultivars including leading Japanese varieties. Southern blot analysis of transformants revealed that a DNA probe for the GUS coding region hybridized with nuclear DNA of transformants and the copy number of introduced gene was different among transformants. The transformants having the GUS reporter gene fused with the PR1a promoter showed high GUS activity after salicylic acid treatment. The level of GUS gene expression was almost as high as in transformed potatoes having the GUS gene fused with the CaMV-35S promoter. Wide variation in the level of gene expression among regenerated transformants was observed. The inducible expression of tobacco PR1a gene in transformed potato cultivars showed that the promoter of the PR1a gene is valuable for potato improvement and is capable of driving the expression of target genes under stress conditions.