Figure 4.

Histochemically determined GUS activity resulting from the release of silencing. (A) Twenty-four-day-old transgenic plants (T1) containing vector construct only, 35S-IRMOM or PR1-IRMOM were grown aseptically and treated with 3 p.p.m. BTH (+) or mock treated (−) as described in Methods. Upper: cotyledons; scale bar, 1 mm. Lower: whole plants, scale bar, 1 cm. (B) Forty-nine-day-old primary transformants (T1) for vector construct only, 35S-IRMOM or PR1-IRMOM were grown in soil and induced by spraying with 200 p.p.m. BTH (+). PR1-IRMOM were also mock treated (−). Leaves were stained for GUS activity as described in Methods. Scale bar, 1 cm. Note: mock-treated vector control and 35S-IRMOM plants are not shown, as they were exactly the same as BTH-treated plants.