A Tomato Vacuolar Invertase Inhibitor Mediates Sucrose Metabolism and Influences Fruit Ripening

Fruit ripening is a complex process that involves a series of physiological and biochemical changes that ultimately influence fruit quality traits, such as color and flavor. Sugar metabolism is an important factor in ripening, and there is evidence that it influences various aspects of ripening, although the associated mechanism is not well understood. In this study, we identified and analyzed the expression of 36 genes involved in Suc metabolism in ripening tomato (Solanum lycopersicum) fruit. Chromatin immunoprecipitation and gel mobility shift assays indicated that SlVIF, which encodes a vacuolar invertase inhibitor, and SlVI, encoding a vacuolar invertase, are directly regulated by the global fruit ripening regulator RIPENING INHIBITOR (RIN). Moreover, we showed that SlVIF physically interacts with SlVI to control Suc metabolism. Repression of SlVIF by RNA interference delayed tomato fruit ripening, while overexpression of SlVIF accelerated ripening, with concomitant changes in lycopene production and ethylene biosynthesis. An isobaric tags for relative and absolute quantification-based quantitative proteomic analysis further indicated that the abundance of a set of proteins involved in fruit ripening was altered by suppressing SlVIF expression, including proteins associated with lycopene generation and ethylene synthesis. These findings provide evidence for the role of Suc in promoting fruit ripening and establish that SlVIF contributes to fruit quality and the RIN-mediated ripening regulatory mechanisms, which are of significant agricultural value.