Ethylene is recognized as the central hormonal driver of ripening in climacteric fruits, triggering changes in color, texture, aroma, and metabolism. Apples are especially sensitive to ethylene accumulation during storage, which accelerates softening and shortens shelf life. While melatonin is known to regulate plant growth, stress response, and senescence, its precise role in controlling ethylene production during fruit ripening has not been clearly defined. Understanding how melatonin interacts with ethylene-related transcriptional networks is essential for developing sustainable strategies to maintain fruit quality, reduce postharvest losses, and improve storage outcomes. However, the molecular mechanisms linking melatonin to ethylene biosynthesis have remained unresolved, requiring deeper investigation.
A research team from Shenyang Agricultural University and partner institutions has uncovered how melatonin delays apple ripening, according to findings published (DOI: 10.1093/hr/uhaf020) on May 1, 2025, in Horticulture Research. The study shows that melatonin suppresses ethylene biosynthesis by inhibiting the transcription factor MdREM10, which would otherwise activate MdERF3 and MdZF32. These transcription factors stimulate MdACS1 and MdACO1, the core genes responsible for producing ethylene. By downregulating MdREM10, melatonin disrupts this transcriptional cascade and slows the ripening process.
The researchers first observed that melatonin levels decrease while ethylene levels increase during natural apple ripening, suggesting opposing regulatory roles. Exogenous melatonin treatment significantly reduced ethylene production and delayed visible ripening. Transcriptomic analyses identified MdREM10, a B3-domain transcription factor, as strongly suppressed in melatonin-treated apples.
Functional assays confirmed MdREM10 as a positive regulator of ethylene biosynthesis. Overexpressing MdREM10 in apple fruit accelerated ripening and increased ethylene output, and melatonin could no longer effectively suppress this response. Further investigation revealed a two-branch regulatory cascade:
• MdREM10 binds directly to the MdERF3 promoter, activating MdERF3, which in turn promotes transcription of MdACS1.
• MdREM10 also binds to and activates MdZF32, which enhances MdACO1 transcription.
Together, MdACS1 and MdACO1 catalyze the key steps of ethylene biosynthesis. Melatonin delays ripening by reducing MdREM10 transcription, thereby decreasing activation of both downstream pathways. This reveals that melatonin regulates ripening primarily at the transcriptional control level, rather than through direct inhibition of enzymatic ethylene synthesis.
“Our findings identify MdREM10 as the key molecular hub linking melatonin signaling to ethylene biosynthesis,” the research team stated. “By uncovering how melatonin acts upstream to regulate transcription factors that govern hormone production, we provide a mechanistic explanation for melatonin's ability to delay ripening. This discovery not only advances fundamental understanding of fruit physiology but also highlights new opportunities to control postharvest quality through natural regulatory pathways.”
This work provides a scientific foundation for using melatonin as a safe and natural treatment to extend the shelf life of apples during storage and transport. Because melatonin is non-toxic and widely conserved across plant species, it may serve as a practical postharvest intervention to reduce food waste. Furthermore, MdREM10, MdERF3, and MdZF32 represent promising gene targets for breeding apple cultivars with slower ripening rates and improved storability. The regulatory architecture described here may also be conserved in other climacteric fruits, indicating broader applications for horticultural production and supply chain stability.
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References
DOI
10.1093/hr/uhaf020
Original Source URL
https://doi.org/10.1093/hr/uhaf020
Funding information
This study received funding from the National Key Research and Development Program of China (2022YFD2100105).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.