Violet LED light-activated MdHY5 positively regulates phenolic accumulation to inhibit fresh-cut apple fruit browning

Fresh-cut fruit browning severely affects the appearance of fruit. Light treatment can effectively inhibit fresh-cut apple fruit browning, but the regulatory mechanism remains unknown. Here, we discovered that violet LED (Light-Emitting-Diode) light treatment significantly reduced fresh-cut apple fruit browning. Metabolomic analysis revealed that violet LED light treatment enhanced the phenolic accumulation of fresh-cut apple fruit. Transcriptomic analysis showed that the expression of phenolic degradation genes ( ) and ( ) was reduced, and the expression of phenolic synthesis gene ( ) was activated by violet LED light treatment. Moreover, two ( and ) transcription factors involved in light signaling were identified. The expression of and was activated by violet LED light treatment. Violet LED light treatment no longer inhibited fresh-cut apple fruit browning in MdHY5- or MdHYH- silenced fruit. Further experiments revealed that MdHY5 and MdHYH suppressed and expression and promoted expression by binding to their promoters. In addition, MdHY5 and MdHYH bound to each other's promoters and enhanced their expression. Overall, our findings revealed that violet LED light-activated and formed a positive transcriptional loop to regulate the transcription of , , and , which in turn inhibited the degradation of phenolics and promoted the synthesis of phenolics, thus inhibiting fresh-cut apple fruit browning. These results provide a theoretical basis for improving the appearance and quality of fresh-cut apple fruit.