MYB transcription factor MdMYB44 positively regulates fruit crispness by directly activating the expression of pectin methylesterase MdMPE3 in apple

Crispness, a key attribute of fruit texture quality, is a critical determinant of apple commercial value. Pectin, a major component of the cell wall, plays a vital role in maintaining cell structure, turgor pressure, and mechanical support, with pectin methylesterase (PMEs, EC 3.1.1.11) mediating pectin modification during cell wall remodeling. In this study, we identified two genes, MdMYB44 and MdMPE3 (pectin methylesterase 3), that regulate apple fruit crispness. Through Y1H, EMSA, ChIP-qPCR, and transient expression assays, we demonstrated that the MYB transcription factor MdMYB44 directly enhances the expression of MdMPE3 by binding to its promoter. These results indicate that MdMYB44 acts as a positive regulator of fruit crispness by activating MdMPE3 transcription. Our findings provide new insights into the molecular mechanisms by which MYB transcription factors and pectin methylesterase influence apple fruit texture, enriching our understanding of the regulation of fruit crispness.