FabHLH130-FaSPS1/FaINV positively contributes to the sugar accumulation in strawberry fruits

Soluble sugars play a crucial role as a carbon and energy source, with their content and composition governing the flavor profile of fruits. Yet how the contents of glucose, sucrose, and fructose are regulated remains poorly understood. In this study, we identified FabHLH130 as a positive regulator in the sucrose metabolism of ‘Snow Princess’ fruits. We generated FabHLH130 overexpression lines in the octoploid cultivar ‘Benihoppe’. Transcriptome analysis reveals higher expression levels of FaSPS1 and FaINV in the sucrose metabolism pathway related to WT. Moreover, the electrophoretic mobility shift and dual-luciferase assays validated that FabHLH130 directly binds to the promoters of FaSPS1 and FaINV , leading to the positive regulation of their expression and enzyme activity. Compared to the WT, the transgenic lines displayed higher total soluble sugar, glucose, sucrose, and fructose contents. Our findings provide insights into the mechanism by which FabHLH130 is associated with sugar accumulation in strawberry fruits and provide a theoretical foundation for understanding soluble sugar metabolism in plants.