Ecdysone agonist-inducible expression of a coat protein gene from tobacco mosaic virus confers viral resistance in transgenic Arabidopsis

Constitutive expression of a gene encoding tobacco mosaic virus (TMV) coat protein (CP) in transgenic plants confers resistance to infection by TMV and related tobamoviruses. Here, we examined resistance to TMV by temporal and quantitative control of TMV Cg CP (CgCP) gene expression using a simple, methoxyfenozide-inducible system in Arabidopsis plants. By soil drenching with a commercial ecdysone agonist (Intrepid-2F/methoxyfenozide), most transgenic lines were induced from undetectable levels of gene expression to protein levels from 0.05 to 0.8% (w/w) of CgCP. This corresponds to up to four times the amount of CP produced by the constitutive cauliflower mosaic virus (CaMV) double 35S promoter. CgCP transcripts were induced by 700-fold, without changing the expression patterns of pathogenesis-related (PR) genes. The high level of accumulation of CgCP was sufficient to produce large amounts of virus-like particles that accumulate in large aggregates throughout the cells. In virus challenge assays, treatment with lntrepid-2F prior to TMV infection resulted in high levels of viral resistance, while no treatment or treatment with the inducer following infection did not confer resistance. This report demonstrates chemically controlled disease resistance and confirms the utility of the ecdysone agonist-inducible system under greenhouse conditions.