Virus-induced gene silencing offers a powerful reverse-genetic tool for the study of gene function in plants. We have previously reported ef- fective gene silencing of plant genes using a viral satellite DNA associated with Tomato yellow leaf curl China virus (TYLCCNV). In this study,we further modified the viral satellite DNA-based vector. The modified vector can induce sulfu (Su) gene silencing as effective as the original vector in Nicotiana ben- thamiana plants,but the new system simplifies pro- cedures for construction of vector derivative. Fur- thermore,a fragment of petunia Su or chalcone syn- thase (CHS) endogenous gene was inserted into the modified vector. When petunia plants were agro- inoculated with the modified vector carrying a Su or CHS gene,the Su silenced plants started to appear yellowing in veins of systemically infected upper leaves two weeks after agroinoculation,while the CHS silenced plants started to show flower color change one month after agroinoculation and later single-color flowers became mosaic.
