Gene expression and soluble sugar accumulation in perennial fruits

Abstract Soluble sugars primarily contribute to fruit flavouring and are crucial for fruit quality. Carbohydrate accumulation in fruits is a multifaceted process that can be influenced by their biosynthesis capacity, sink strength, homeostasis, and vacuolar storage ability. Moreover, total soluble sugar contents in fruits also vary among different varieties/species and environmental conditions. Numerous studies have elucidated the carbohydrate regulatory mechanism in fruits; however, there is a knowledge gap regarding the most important contributor to soluble sugar accumulation in perennial fruits. Here, we briefly discussed the recent advances, including carbohydrate long-distance transportation, metabolism and vacuolar storage, and transcript factors for soluble sugar accumulation in fruits. Most importantly, we elucidated that the sink strength in fruit is the most crucial factor that can trap more soluble sugars by maintaining continuous unloading to fruit by genes of cell wall invertase; moreover, genes of sucrose transporters/pyrophosphatase play key roles in vacuolar storage of soluble sugars in perennial fruits. This review delivers a comprehensive summary of recent findings for soluble sugar regulation and fruit quality improvement, which may facilitate sugar optimisation in fruit crops for enhanced fruit quality.