A Review of Soluble Sugar Metabolism in Fruit Development

Abstract

Fruits play a pivotal role in promoting human health, with their natural sweetness being a key factor that influences consumer preferences and shapes vendor pricing strategies. The sweetness of fruit is primarily determined by the composition and concentrations of soluble sugars, exhibiting considerable variation among different fruit species and cultivars due to genotypic differences. In response to the increasing consumer demand for nutritious diets and premium-quality fruits, recent research has progressively shifted its focus toward elucidating the composition and metabolic pathways of sugars in fruit, as well as developing cultivars with enhanced sweetness. However, the specific mechanism of sugar metabolism and the regulatory network of its influencing factors are still not fully understood, which, to some extent, hinders the breeding of high-sweetness fruits and further development in sugar utilization. This review systematically summarizes the dynamic changes in major soluble sugars during fruit development and highlights recent advances in three core pathways: sucrose metabolism, sorbitol metabolism, and hexose metabolism. By integrating transcriptional, post-transcriptional, and post-translational regulation with sugar signaling and environmental responses, a multi-level regulatory model of fruit sugar metabolism is proposed. Furthermore, key unresolved scientific questions and emerging research directions are identified, providing a theoretical basis for molecular breeding and the targeted improvement of sugar-related quality traits in fruits.