Silencing the Expression of an Agrobacterium Vitis Oncogene in a Model Plant


The purpose of this study was to demonstrate the feasibility of silencing the expression of an essential oncogene from Agrobacterium vitis. Plants that silence Agrobacterium oncogenes are expected to resist the formation of tumors, and therefore better tolerate crown gall disease. Transgenic Petunia hybrida plants that expressed the coding sequence of the Agrobacterium vitis Tm4 TA-iaaM gene under the control of the cauliflower mosaic virus (CaMV) 35S promoter produced a readily recognizable phenotype that was characteristic of elevated auxin levels. A transgenic line that stably expressed the 35S-iaaM transgene was double-transformed with a DNA construct that contained two convergently repeated copies of a partial iaaM sequence. A subset of the double-transformed plants appeared phenotypically wild-type even though they maintained an apparently intact 35S-iaaM transgene in their genomes. These plants had reduced iaaM RNA levels relative to the progenitor 35S-iaaM line and to those double-tranformants that retained the elevated-auxin-levels phenotype. These data suggest that the down-regulation of the 35S-iaaM transgene was mediated through a gene silencing mechanism.

Document Type




Publication Date


Journal Title

Acta Horticulturae