Melatonin suppresses ethylene biosynthesis by inhibiting transcription factor MdREM10 during apple fruit ripening.

Ethylene, a plant hormone, is essential for apple () ripening. The precise molecular mechanism by which melatonin (MT) influences ethylene biosynthesis during apple fruit ripening remains unclear. This study found that exogenous MT treatment inhibited ethylene production and postponed apple fruit ripening. The endogenous MT content of apple fruits exhibited an inverse correlation with ethylene production during fruit ripening, suggesting that MT functions as a ripening suppressor in apple fruits. MT treatment suppressed the expression of key ethylene biosynthesis genes, and , during apple fruit ripening. MT treatment decreased the expression levels of transcription factors and . MdREM10 binds to the promoter, enhancing its expression and subsequently promoting transcription. Furthermore, MdREM10 directly bound to the promoter, promoting its transcription. MdZF32 directly bound to the promoter, inducing its expression. The findings suggested that MT suppresses ethylene biosynthesis and fruit ripening by inhibiting MdREM10, which indirectly promotes transcription via upregulation, and transcription via upregulation.