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Figure 1.  Glucose signaling stabilizes MdbHLH3 by promoting the phosphorylation of MdbHLH3 by MdHXK1 and inhibiting MdPUB29 ubiquitination of MdbHLH3. This process can enhance the transcriptional activation of MdbHLH3 on ethylene synthesis-related genes, such as MdACO1, to regulate fruit ripening and enhance the transcriptional activation of MdbHLH3 on MdcyMDH to regulate fruit acidity through the TCA cycle. Additionally, the interaction between MdbHLH3 and MdMYB1 could enhance the transcriptional activation of MdVHA-B1 and MdVHA-B2 by MdMYB1, which affects the expression of acid transporters Ma1 and MdtDT to regulate fruit acidity. MdMYB1 can also affect fruit color through the transcriptional regulation of genes related to anthocyanin synthesis.