Involvement of sucrose transporter SUT4 in regulating tomato yield and fruit quality.

Previous studies have demonstrated differential regulations of sucrose transporters (SUTs) on crop yield among species. Meanwhile, information about the possible regulation of SUTs on crop quality is lacking. Here, we investigated the regulation of tomato (Solanum lycopersicum) SlSUT4 on the fruit yield and quality. The results showed that SlSUT4 overexpression increased the fruit yield, while the effect of silencing this gene on the yield was dependent on the cultivation conditions - decreased under non-pruning conditions but did not change under pruning conditions. Alteration of SlSUT4 expression affected the primary metabolite profiles in tomato fruits, and both overexpressing and silencing SlSUT4 promoted the levels of key metabolites in glycolysis and the downstream tricarboxylic acid cycle and malic acid biosynthesis. The total soluble solids content was increased in the SlSUT4-overexpressed plants, but decreased in the SlSUT4-silenced plants. Silencing SlSUT4 decreased the flavonoid level. The concentrations of vitamin C and lycopene were not affected in either transgenic plant. The results suggest that SlSUT4 regulates tomato yield and total soluble solids content in fruits, offering a clue for tomato genetic improvement.