摘要Sugars are involved in plant growth, fruit quality, and signaling perception. Therefore, understanding the mechanisms involved in soluble sugar accumulation is essential to understand fruit development. Here, we report that MdPFPβ, a pyrophosphate-dependent phosphofructokinase gene, regulates soluble sugar accumulation by enhancing the pho-tosynthetic performance and sugar-metabolizing enzyme activities in apple (Malus domestica Borkh.). Biochemical analysis revealed that a basic helix-loop-helix (bHLH) transcription factor, MdbHLH3, binds to the MdPFPβ promoter and ac-tivates its expression, thus promoting soluble sugar accumulation in apple fruit. In addition, MdPFPβ overexpression in tomato influenced photosynthesis and carbon metabolism in the plant. Furthermore, we determined that MdbHLH3 increases photo-synthetic rates and soluble sugar accumulation in apple by activating MdPFPβ expression. Our results thus shed light on the mechanism of soluble sugar accumulation in apple leaves and fruit: MdbHLH3 regulates soluble sugar accumulation by activating MdPFPβ gene expression and coordinating carbo-hydrate allocation.