Relationship between Glutamate Accumulation and Ethylene Synthesis in Tomato Fruit during Ripening

The effect of ethylene on the accumulation of glutamate in the fruit of normal tomato ('Rutgers' and 'Momotaro')and ripening inhibitor mutant (rin) tomato(Lycopersicon esculentum Mill.) during ripening was investigated.As fruit ripening progresse,glutamate content in the fruit pericarp tissue increased greatly in 'Rutgers' but remained low and constant level in rin tomato.Glutamine and γ-aminobutyric acid contents decreased gradually during ripening in both 'Rutgers'and rin fruit.Relatively high activities of glutamate dehydrogease,glutamate synthase and glutamine synthetase were detected throughout fruit ripening in both varieties,whereas no relationship was observed between glutamate content and the enzyme activieies.Treatment of 'Momotaro'fruit with diazocyclopentadience,an inhibitro of ethylene action,inhibited the increase in ethylene production and glutamate accumlation which are associated with fruit ripening,suggesting that glutamate accumlation may be mediated through ethylene.However,glumamate content in rin fruit treatde with exogenous ethylene remained low and unchanged uitil after four days.The results indicate that accumulation of glutamete in tomato fruit is likely to be related to the ripening process apart from the direct role of ethylene.