Alfalfa is a globally important forage crop valued for feed quality and biomass, yet its performance often declines under suboptimal growing conditions. Selenium has attracted attention because, at appropriate doses, it can improve plant growth and photosynthesis, while also helping produce selenium-enriched forage for animal nutrition. At the same time, chlorophyll biosynthesis is central to photosynthetic efficiency and crop productivity. Earlier studies in alfalfa focused mainly on transcriptional regulation, environmental cues, and hormone signaling, leaving post-transcriptional control poorly understood. Based on these challenges, deeper research was needed into how selenium regulates chlorophyll biosynthesis through miRNA-mediated molecular networks in alfalfa.
On November 13, 2025, researchers from Zhengzhou University and Qinghai Normal University reported (DOI: 10.1093/hr/uhaf305) in Horticulture Research that selenium promotes chlorophyll biosynthesis in alfalfa through a newly defined MsmiR171–MsSCL6–MsPOR regulatory pathway. Their study explains how selenium-induced molecular signaling translates into greener leaves, stronger photosynthesis, and improved quality-related traits, offering a mechanistic bridge between micronutrient treatment and forage improvement.
The team began by identifying MsmiR171 as a selenium-responsive miRNA and predicting MsSCL6 as its target. Using GUS staining and dual-luciferase assays, they confirmed that MsmiR171 negatively regulates MsSCL6. They then tested function through overexpression and silencing experiments. Plants overexpressing MsmiR171 developed darker leaves and showed higher chlorophyll, soluble protein, soluble sugar, and starch contents, while plants with suppressed MsmiR171 became chlorotic and lost chlorophyll-related advantages. Photosynthetic indicators, including net photosynthetic rate and stomatal conductance, followed the same trend.
The opposite pattern appeared when MsSCL6 was manipulated. Overexpression of MsSCL6 caused yellowing leaves, reduced chlorophyll accumulation, and weaker photosynthetic performance, whereas silencing MsSCL6 improved these traits. Selenium treatment generally deepened leaf color and partly rescued the negative phenotypes, showing that selenium acts upstream in this pathway. Mechanistically, the researchers found that MsSCL6 directly binds the promoter of MsPOR and represses its transcription. Because MsPOR encodes a key enzyme in chlorophyll biosynthesis, this finding placed it at the functional endpoint of the selenium-responsive cascade. Together, the data reveal a clear model: selenium raises MsmiR171, MsmiR171 suppresses MsSCL6, and reduced MsSCL6 releases MsPOR to drive chlorophyll accumulation.
The study suggests that selenium does not simply “green” alfalfa through a broad physiological effect. Instead, it works through a precise genetic circuit that links a micronutrient signal to chlorophyll production. By uncovering the MsmiR171–MsSCL6–MsPOR module, the researchers provide one of the clearest explanations so far of how selenium enhances photosynthesis at the post-transcriptional level in alfalfa. This gives the field a more targeted framework for improving both plant performance and forage nutritional value.
The findings have clear value for forage breeding and selenium biofortification. A better understanding of this pathway could help breeders design alfalfa varieties with stronger chlorophyll synthesis, better photosynthetic efficiency, and improved biomass accumulation. It also supports efforts to produce selenium-enriched forage, which may benefit livestock nutrition in regions affected by selenium deficiency. Beyond alfalfa, the work highlights how miRNA-centered regulatory modules can convert trace-element signals into agronomically useful traits. That makes this study not only a story about greener leaves, but also about smarter strategies for building high-quality forage crops.
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References
DOI
10.1093/hr/uhaf305
Original Source URL
https://doi.org/10.1093/hr/uhaf305
Funding information
This work was supported by the National Natural Science Foundation of China (grant no. 51508518) and the Special Fund for Agro-scientific Research in the Public Interest (grant no. 201503134).
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.