Synergistic effect of abscisic acid and ethylene on color development in tomato (Solarium lycopersicum L.) fruit

In order to investigate the synergistic effect of abscisic acid and ethylene on tomato color development during ripening, mature green tomato fruit were harvested and treated with abscisic acid (ABA), 1-methylcyclopropene (1-MCP), alone or in combination, and dihydroguaiaretic acid (NDGA), and then were stored at 20 degrees C and 90% RH for fourteen days. Endogenous ethylene production, color development and the expression profiles of major related genes in treated fruits were examined. Furthermore, 2000 bp sequences upstream of major related genes were analyzed. Results indicated that ABA significantly up-regulated the expression levels of major genes related to carotenoids and flavonoids biosynthesis (ranging from 2.08 to 35 folds) and initiated the accumulation of carotenoids, phenolics and flavonoids by 2 or 4 days earlier than that in control. However, results demonstrated that the exogenous ABA could not significantly affect tomato color development without ethylene. The outcome of gene promoter analysis revealed that, besides single existence of ABRE or ERE motifs, 10 of 23 genes involved in carotenoids biosynthetic pathway, and 10 of 40 genes involved in flavonoid biosynthesis pathway possess both ABRE and ERE motifs in their 2000 bp upstream sequences, suggesting that ABA and ethylene may affect fruit color development via the collaborative regulation of these genes.