Induction of differential flower pigmentation patterns by RNAi using promoters with distinct tissue-specific activity

We attempted to evaluate the effects of promoters on flower color modification by RNA interference (RNAi). An inverted repeat of a tobacco chalcone synthase ( CHS ) fragment was used as a trigger under control of three different promoters and transformed into tobacco plants. The flowers of CaMV35S:CHSir displayed a completely white color, whereas those of Agrobacterium rhizogenes rolC:CHSir kept slight pigmentation. On the other hand, gentian GtCHS:CHSir showed decreased pigmentation in the tip only but not at the base of the petal limbs, which resulted in the appearance of bicolor-like flowers. The observed suppression of flower pigmentation corresponded with tissue-specificity of each promoter activity determined by histochemical GUS assay using transgenic tobacco plants with each promoter–GUS construct. These results demonstrate for the first time that RNAi-mediated silencing can be used to produce novel-colored flowers with high horticultural value.