Fig. 3. Targeting to higher plant plastids by the S/T-rich region in the PCP leader. The luciferase reporter construct lacking the first hydrophobic region (as described in Fig. 2B) was fused with a Solanum chacoense 5'UTR and introduced into a highly regenerable genotype (G4) of S. chacoense. Two independent transformants expressed high levels of luciferase in the chloroplasts (A,B), as shown by immunoelectron microscopy using a commercial anti-luciferase as a primary antibody and a 20 nm gold-conjugated rabbit anti-goat as a secondary antibody. Label is observed over the plastid (P) but not the cell wall (CW), vacuole (V) or nucleus (N). Untransformed plants (C) show only background labeling. (D) Quantification of the label density is shown as number of gold beads per µm² for the two transformed plants above as well as for an untransformed control. Bars, 1 µm.