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Polygalacturonase (PG) was studied during ripening and senescence of postharvest tomato fruit at pink stage at low and normal temperature. The results showed that the PG activity increased, then decreased during ripening and senescence of tomato. Low temperature inhibited but ethylene enhanced PG activity. Ethylene also enhanced calmodulin content, which was dependent on Ca 2+concentration in cell. When EGTA(Ca 2+chelator), verapamil(Vp) and LaCl 3(Ca 2+channel blockers), trifluoperazine and chloropromaize (two CaM antagonisms) were used to treat tomato fruit at green mature stage with ethylene, they could reverse ethylene-induced increase in PG activity, but Vp, chloropromaize (CPZ), trifluoperazine (TFP) could not directly influence PG activity, which indirectly indicated that influx of Ca 2+ from the extracellular space including the cell wall via the Ca 2+ channel localized in plasma membrane and CaM were required for ethylene-induced PG activity increase and that ethylene signal transduction may be related to Ca 2+CaM messenger system.
Polygalacturonase (PG) was studied during ripening and senescence of postharvest tomato fruit at pink stage at low and normal temperature. The results showed that the PG activity increased, then decreased during ripening and senescence of tomato. Low temperature inhibited but ethylene enhanced PG activity. When EGTA (Ca 2 + chelator), verapamil (Vp) and LaCl 3 (Ca 2 + channel blockers), trifluoperazine and chloropromaize (two CaM antagonisms) were used to treat tomato fruit at green mature stage with ethylene, they could reverse ethylene-induced increase in PG activity, but Vp, chloropromaize (CPZ), trifluoperazine (TFP) could not directly influence PG activity, which indirectly indicates that influx of Ca 2 + from the extracellular space including the cell wall via the Ca 2+ channel localized in plasma membrane and CaM were required for ethylene-induced PG activity increase and that ethylene si gnal transduction may be related to Ca 2 + CaM messenger system.