PG与番茄果实成熟的关系

系统比较了转多聚半乳糖醛酸酶(PG)反义基因和对照番茄果实成熟过程中绿熟、转色、粉顶、粉红、全红5个时期的PG活性和与其相关的生理、生化组分的动态变化.实验表明,转基因果与对照果相比,PG活性始终处于较低水平,PG活性强烈被抑制是在全红期;果实的硬度、贮藏寿命指数都高于对照果;番茄红素合成积累进程被延缓;可溶性果胶含量、电解质外渗百分率均低于对照果.外源乙烯刺激引起对照果PG活性剧增,而转基因果表现钝化.讨论了PG活性与果实成熟、耐贮性及软化的关系,及对外源乙烯刺激的敏感性.首次明确提出PG活性在对照果中极大地表达,在转基因果中强烈被抑制是在全红期,而不是在整个成熟期;PG活性在果实软化中起直接和重要作用;PG活性的高低与番茄红素的合成与积累有关.

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.