A virus-induced gene silencing approach for the suppression of nicotine content in Nicotiana benthamiana

Virus vectors have been used to study plant gene function by transiently overexpressing specific gene products, or conversely, silencing specific endogenous gene functions. Previously, we reported the establishment of tobamovirus vectors and its applications. In this study, we observed that tobamovirus vector could drive ectopic expression of green fluorescent protein (GFP) in roots after infecting leaves, indicating successful invasion into underground tissues. Subsequently, we attempted to apply the tobamovirus vector system to suppress the expression of putrescine N-methyltransferase (PMT), which is the first committed key enzyme for the biosynthesis of nicotine and is active in the underground parts of plants. Two or three weeks after inoculation with the vector harboring a partial fragment of PMT cDNA, we observed a reduction in the PMT mRNA level in the root and in the nicotine content of the aerial parts of the plant Nicotina benthamiana. The possibilities and limitations of the virus vector for the analysis of metabolic pathways are discussed.