Abstract
We have recently reported that sugar concentration (Brix %) in tomato fruit was enhanced by root-chilling cultivation (Fujimura et al. 2008). In this study, we analyzed the concentration of starch and sugars and the gene expression of the major enzymes for starch and sugar metabolisms during tomato fruit development, to help define the mechanism. Root chilling did not affect the pattern in which starch accumulated in early expansion stage and disappeared before ripening while fructose and glucose increased with the fruit development. Root chilling, however, enhanced the accumulation levels of starch, fructose and glucose. Root chilling also enhanced the expression of genes for starch synthesis (AGPase large subunit and SuSy), but not for starch degradation: The expression of SPS gene was not affected, and that of an apoplastic invertase (LIN5) gene was inhibited, by root chilling. These results suggested that root chilling activated the starch synthesis during expansion stage.
