Flower color modification of gentian plants by RNAi-mediated gene silencing

RNA interference (RNAi) is an efficient and powerful technique for gene silencing compared with antisense and sense suppression. Here we report adaptation of RNAi technology to modify flower colors in gentian, targeted for suppression of three anthocyanin biosynthetic genes; chalcone synthase (CHS), anthocyanidin synthase (ANS) and flavonoid 3',5'-hydroxylase (F3'5'H). The petals of transgenic gentian plants with a suppressed CHS gene exhibited pure white to pale-blue color, while those with a suppressed ANS gene showed only pale-blue. The suppression of the F3'5'H gene decreased delphinidin derivatives and increased cyanidin derivatives, and led to magenta flower colors. Northern blot analyses confirmed that all transgenic gentian plants showing typical phenotypes had strongly suppressed transcriptions of the targeted genes, corresponding with a change in anthocyanin accumulation and composition in their petals. Some rolCpro-CHSir transgenic gentians exhibited bicolor phenotypes with reduced anthocyanin accumulation along the vascular bundles. These data demonstrated that the suppression of anthocyanin biosynthetic genes by RNAi was successfully applied to gentian plants to change flower color, and this could be useful for designing novel flower color and patterns. Transgenic gentian plants produced in this study might be utilized as elite materials in the breeding of gentian plants in the near future.