Tonoplast Sugar Transporters Coordinately Regulate Tomato Fruit Development and Quality.

Abstract

Fruit yield and quality are antagonistically regulated traits in tomato. An excessive focus on increasing yield often leads to a decline in quality. How to achieve the delicate balance between high yield and desirable fruit quality is still a big challenge. In this study, we discovered that disrupting the function of tomato tonoplast sugar transporter 3a (TST3a) can significantly enhance both fruit weight and flavor. In tomato, there are three TSTs, namely SlTST1, SlTST3a and SlTST3b, which possess same sugar transport specificity for fructose and glucose and redundantly control cell expansion during fruit development. The different levels of sugar accumulation in the sltst mutants significantly associated with the fruit size and flavor. The reason for the enlarged fruits of sltst3a mutants, which are a consequence of sugar accumulation, is the increased abundance of SlTST1 at the tonoplast and coupled with the highest sugar transport capacity of SlTST1. Further studies established that SlTST3a prevented the localization of SlTST1 to the tonoplast by inhibiting its interaction with VH1-interacting kinase (SlVIK). Mutation of SlTST3a in the cultivated tomatoes can simultaneously enhance tomato fruit size and sugar content. Our findings present potential avenues for simultaneously improving both fruit quality and yield and provide valuable insights into the mechanisms underlying the storage sugar for fruit development.