Characterization of Transgenic SGT1-silenced plants

SGT1 plays an important role in almost all R gene mediated disease resistance pathways and some non-host disease resistance pathways (Jin et al., 2002; Peart et al., 2002). In order to investigate the possible role of SGT1 in non-host resistance of tobacco plants to P. infestans, we generated transgenic SGT1-silenced tobacco plants (Samsun NN) using RNAi. Twelve transgenic lines with less severe SGT1 silencing phenotype were recovered. Six out of twelve transgenic lines showed clear attenuation of N mediated TMV resistance pathway. Our results showed that the SGT1-silenced tobacco plants were resistant to the three strains of P. infestans, which leads to the conclusion that SGT1 is not involved in the non-host resistance to P. infestans in tobacco or the transgenic plants were only partially silenced and the remaining SGT1 mRNA may be sufficient for resistance to P. infestans.