Abstract: The experiment conducted with ‘Starkrimson’ apple fruit showed that the degradation activity of sucrose synthase declined gradually with the accumulation of fructose, glucose and sucrose during fruit development.
However, the synthesis activity of sucrose synthase decreased during the early stage of fruit development and then increased significantly during the late development stage. Western blotting assay of sucrose synthase detected the presence of a 90 kD peptide and the intensity of immuno􀀁signal increased with fruit developing. On the other hand,
the results of immunogold electron􀀁microscopy assay showed that sucrose synthase was mainly located in the cytoplasm of apple flesh cell and few immunogold particles were found on cell wall or in vacuole. The results also indicated that the quantity of sucrose synthase increased with fruit development and was consistent with the results of Western blotting. So it is suggested that the degradation and synthesis of sucrose in apple fruit may be modulated by sucrose synthase. Fructose may act as sugar signal and modulate the activity of sucrose synthase.

Key words: Apple fruit, Sucrose synthase, Western blotting, Immunogold subcellular localization