The characterization of NbGSTU4-knockdown Nicotiana benthamiana plants. (a) Western blot analysis of Bamboo mosaic virus (BaMV), Potato virus X (PVX), Cucumber mosaic virus (CMV) and Tobacco mosaic virus (TMV) coat protein in NbGSTU4-knockdown (indicated as K) and control (Luc-knockdown indicated as C) N. benthamiana plants 3 d post inoculation. Total proteins were extracted from inoculated leaf, separated on a 12% SDS-polyacrylamide gel, and probed with anti-coat protein antiserum. rbcL indicates the large subunit of RuBisCo stained with Coomassie Blue as a loading control. (b) A histogram of coat protein accumulation derived from (a). (c) The accumulation levels of different types of GST mRNA indicated in NbGSTU4-knockdown and control (Luc-knockdown) plants were measured by real-time RT-PCR. Control plants, black bars; NbGSTU4 knockdown plant, grey bars. The numbers shown above the statistic bar were the average ± SE of at least three independent experiments. Asterisks indicate statistically significant differences between the indicated group analyzed by Student's t-test (***, P < 0.001).