Grafting is essential for improving crop resilience, disease resistance, and stress tolerance, particularly in horticultural crops such as melon. However, successful grafting depends on efficient healing at the graft junction, where scion and rootstock tissues must adhere and re-establish vascular connections. This process is influenced by environmental factors, including light conditions, yet the underlying molecular mechanisms remain poorly understood. Previous studies have identified enzymes involved in cell wall remodeling as key players in graft union formation, but how their activity is regulated by light signals has been unclear. Based on these challenges, it is necessary to conduct in-depth research into how light-regulated genetic pathways control graft union healing.
Researchers from Shenyang Agricultural University and collaborating institutions report that red light dramatically enhances graft union healing in melon seedlings by activating a specific transcriptional regulatory module. Published (DOI: 10.1093/hr/uhaf251) online in Horticulture Research in 2025, the study demonstrates that red light stimulates a light-responsive transcription factor, which in turn activates downstream genes responsible for tissue adhesion and vascular reconnection. Through genetic, molecular, and histological analyses, the researchers show how controlled light exposure can translate into faster and more reliable graft healing.
The study identifies a clear molecular pathway linking red light perception to graft union healing. At the center of this process is a light-responsive transcription factor that becomes strongly induced under red light conditions. Once activated, this factor binds directly to the promoters of two WRKY transcription factors, increasing their expression during the early stages of graft healing. These WRKY proteins then form a functional complex and directly activate a gene encoding a β-1,4-glucanase enzyme, which plays a crucial role in loosening cell walls and promoting cell-to-cell adhesion at the graft interface.
Experimental evidence showed that plants exposed to red light exhibited earlier callus formation, faster degradation of the isolation layer, and more rapid vascular reconnection between scion and rootstock. When any component of this pathway was genetically silenced, graft healing was significantly delayed, confirming the functional importance of the entire regulatory module. Conversely, overexpression of the downstream enzyme led to stronger physical adhesion and earlier xylem connectivity. Together, these results demonstrate that red light does not merely influence graft healing indirectly, but actively rewires transcriptional networks that control tissue regeneration.
“Our findings reveal a direct molecular link between light signaling and graft union healing,” said the study’s senior author. “By identifying how red light activates a specific transcriptional cascade, we now understand why light quality has such a strong impact on graft success. This work moves beyond descriptive observations and provides a mechanistic framework that explains how environmental signals can precisely regulate tissue regeneration in plants.”
The discovery has immediate practical implications for horticulture and seedling production. By optimizing red light exposure during the critical post-grafting period, growers could significantly improve graft survival rates and reduce production losses. The identified genetic pathway also offers molecular targets for breeding or biotechnological approaches aimed at enhancing graft compatibility. More broadly, the study highlights how controlled environmental cues, such as light quality, can be strategically used to guide plant regeneration processes. This insight may extend beyond melon to other grafted crops, opening new avenues for improving efficiency and sustainability in modern agriculture.
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References
DOI
10.1093/hr/uhaf251
Original Source URL
https://doi.org/10.1093/hr/uhaf251
Funding information
This work was supported by the National Natural Science Foundation of China (32272696) and the Department of Science & Technology of Liaoning province (2023JH1/10200010).
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.