ADP-glucose pyrophosphorylase is localized to both the cytoplasm and plastids in developing pericarp of tomato fruit

Abstract

The intracellular location of ADP-glucose pyrophosphorylase (AGP) in developing pericarp of tomato (Lycopersicon esculentum Mill) has been investigated by immunolocalization. With the use of a highly specific anti-tomato fruit AGP antibody, the enzyme was localized in cytoplasm as well as plastids at both the light and electron microscope levels. The immunogold particles in plastids were localized in the stroma and at the surface of the starch granule, whereas those in the cytoplasm occurred in cluster-like patterns. Contrary to the fruit, the labeling in tomato leaf cells occurred exclusively in the chloroplasts. These data demonstrate that AGP is localized to both the cytoplasm and plastids in developing pericarp cells of tomato.

Figure 1

Light micrographs showing immunolocalization of AGP in developing pericarp of tomato fruit. A, Carbohydrate-specific staining. Starch grains stained red. B and C, Anti-tomato fruit AGP serum detected a signal (gray dots) in both plastids and cytoplasm (arrows). D, The preimmune control serum detected no signal. S, Starch granule; and V, vacuole. A, ×351; B, ×1560; and C and D, ×1950.

Figure 2

Electron micrographs showing immunolocalization of AGP in developing pericarp of tomato fruit. Anti-tomato fruit AGP serum was used for immunolocalization. A, Immunogold particles reside in both plastids and cytoplasm. B, Immunogold particles reside in the cytoplasm. C, Immunogold particles reside at or near the starch granule boundary. D, Preimmune serum control. P, Plastid; S, starch granule; St, stroma; and Cyt, cytoplasm. A, ×24,180;B, ×31,200;C, ×30,420; and D, ×28,860.

Figure 3

Electron micrographs showing immunolocalization of AGP in tomato leaves. Anti-tomato fruit AGP serum was used for immunolocalization. A, Immunogold particles reside in the stroma of chloroplasts. B, Preimmune serum control. Labels are as in Figure 2. A, ×54,600; B, ×42,900.