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RNA Silencing of the Introduced Coat Protein Gene of Turnip mosaic virus Confers Broad-Spectrum Resistance in Transgenic Arabidopsis

First, fourth, and fifth authors: Kanagawa Institute of Agricultural Science, 1617 Kamikisawa, Hiratsuka, Kanagawa 259-1204, Japan; second author: Laboratory of Plant Virology, Faculty of Agriculture, Saga University, Saga 840-8502, Japan; and third author: Laboratory of Breeding, Faculty of Agriculture, Saga University, Saga 840-8502, Japan

The coat protein (CP) gene derived from Turnip mosaic virus (TuMV) isolate JO was introduced into Arabidopsis thaliana and the resulting transgenic progenies were analyzed for resistance to TuMV. Transgenic Arabidopsis plants with no detectable transcripts of the introduced CP gene exhibited complete resistance to TuMV. There was no significant correlation between the resistance and the copy number of the transgene. Instead, small interfering RNAs (siRNAs) were detected in these resistant plants, indicating that the resistance is attributed to RNA silencing. The RNA-mediated resistance was not only inherited over successive generations but also effective against 17 worldwide TuMV isolates with different pathogenicity. Comparative analysis of the CP genes among the 17 TuMV isolates revealed that the 380-nt in the 3′ region is highly conserved, suggesting the importance of the 3′ conserved region for broad-spectrum resistance. These results indicate that introduction of the TuMV-CP gene into the target Brassicaceae plants followed by selecting transformants that show RNA silencing for the transgenes can be an effective and reliable strategy for developing crucifer crops with a broad spectrum of resistance to TuMV.