SPATIOTEMPORAL RELATIONSHIPS BETWEEN ABSCISIC ACID AND ETHYLENE BIOSYNTHESIS DURING TOMATO FRUIT RIPENING

Fruit ripening is a genetically programmed process that involves complex interactions of hormones. Ethylene is the dominant trigger for ripening in climacteric fruit and its production is tightly regulated by internal signals during fruit ripening. Abscisic acid (ABA) plays a major role in late seed development and fruit ripening. Genetic analyses suggests that ABA and ethylene closely interact and both function in plant growth and development. The objective of this study was to investigate the spatiotemporal relationship between endogenous ABA and ethylene during tomato fruit (Lycopersicon esculentum Mill. cv. Zhongza 101) ripening. Endogenous abscisic acid content, ethylene production, ACC content, activities of ACC oxidase were measured during ripening of tomato fruit. Although the maximum ABA content, ACC content and ethylene climacteric peak occurred at different ripening stages, they all increased in seeds before they increased in pericarp tissues. Maximum ABA and ACC contents preceded ethylene production in both the seeds and pericarp. Changes in the activity of ACC oxidase were coincident with those of ethylene production and ABA content. Exogenous ABA treatment made the internal ABA content increase, both in the pericarp and the seed; while treatment with fluridone, an inhibitor of ABA synthesis, inhibited ethylene production. The results suggest that seeds may impact on the process of postharvest tomato fruit ripening by regulating of endogenous ABA content and ethylene production, and that ABA regulates fruit ripening by triggering ethylene production.