Fig. 2. RNAi reduces PPO expression in red clover leaves. Leaf extracts of nontransformed control (C) or independently derived silenced (numbered) plants from NEWRC27 and NEWRC30 red clover genotypes were analyzed for extract browning, PPO protein by immunoblotting (5 µg protein per lane) with a PPO antibody, or for PPO activity by a quantitative PPO activity assay. PPO activity is expressed as nkat mg^–1. For NEWRC27–1 and NEWRC30–0 plants transformed with the silencing construct, PPO activity was not detectable (ND) and no browning was seen, even after 24 h.