The Relation between PG and Ripening of Tomato Fruit

The polygalacturonase activity and some physiological changes of transgenic (withantisense PG gene) and control tomato fruits were systematically compared at green-mature, turning,pink-top, pink and red stages in ripening process. The results showed that PG activity of transgenictomato fruits was lower than that in control fruits in ripening process. The PG activity of transgenicfruits were almost inhibited at red stage. Transgenic fruits are better than control fruits in firmnessand storability. Synthesis and accumulation of lycopene of transgenic fruits are postponed, solublepectin content and electric conductivity were all lower than those in control fruits. Stimuli of exo-ethylene caused sharp increase of PG activity in control fruits, but not in transgenic fruits. Theinterrelation of PG activity with softness, storability and susceptivity to stimulus from exo-ethylenewas discussed. We proposed for the first time, the PG activity sharp increasing in control fruits andalmost inhibiting in transgenic fruits were only at red stage, not at whole ripening stage, and the PGactivity plays an important and direct role in fruit ripening softness.