Immunochemical and immunogold electron microscopic detection of CBP70 in chloroplasts of bundle-sheath cells of green maize leaves. (A, B) Immunochemical localization of CBP70 on cross-sections of the middle part (10 cm from the base) of the third leaf of 20-d-old green maize plants. LR White-embedded leaf sections were used. (A) Sections were incubated with mouse anti-CBP70 mAb of the second group (14A4) or (B) with non-immune serum as a negative control, biotinylated anti-mouse antibodies, and streptavidin-alkaline phosphatase conjugate. (A) CBP70 in chloroplasts of bundle-sheath cells surrounding vascular bundle. Large elongated chloroplasts are positioned in bundle-sheath cells near the cell wall opposite to the vascular bundle. CBP70 is localized within chloroplasts in discrete regions arranged along the longitudinal chloroplast axis (black arrow). Plastids in other cells are not stained. (B) Negative control: CBP70 was not detected. (C) Immunogold electron microscopic detection of CBP70 in chloroplasts of bundle-sheath cells of the third leaf of 20-d-old maize green plant. (C) Ultrathin sections were treated with mouse anti-CBP70 mAbs of the second group (14A4) or (D) with non-immune serum (negative control), biotinylated anti-mouse antibodies, and streptavidin-gold (15 nm). CBP70 is localized in the chloroplast (black arrow); it is absent from starch grains bsc-bundle-sheath cells; chl, chloroplast; N, nucleus; S, starch grain; Vs, vascular bundle. Scale bars are 30 μm (A, B) and 1 μm (C, D).