Research progress on sucrose accumulation characteristics and their molecular regulatory networks in the fruits of fruit trees

Sucrose is a key determinant of fruit sweetness and flavor quality. However, sucrose accumulation varies greatly among fruit tree species, and the molecular regulatory mechanisms and gene networks underlying this variation have not been systematically analyzed, which limits deeper insights into fruit quality improvement. Here, based on the sucrose accumulation characteristics of mature fruits, we classify major fruit trees into three types: sucrose-accumulating, intermediate-converting, and sucrose-hydrolyzing, and clarify the differences in sucrose metabolism and accumulation among them. We further integrate QTL mapping and multi-omics analyses to systematically catalog sucrose regulatory genes in fruit trees. Focusing on the pathways of synthesis, transport, and storage, we analyze the molecular regulatory network of sucrose accumulation and reveal the underlying molecular mechanisms in different fruit trees. We also clarify the regulatory effects of endogenous hormones and environmental factors on sucrose metabolism. This review aims to advance the theoretical framework of molecular regulation of sugar accumulation in fruit trees and to provide theoretical references and technical support for flavor quality improvement and precision breeding for sugar content in fruit.