Tea plants' secret to nitrogen efficiency uncovered through leaf assay
image: A proposed model for transport and remobilization of nitrate and chlorate in tea plant.
Credit: Horticulture Research
Efficient nitrogen use is vital for sustainable tea cultivation and quality improvement. This study developed a rapid method to evaluate nitrate use efficiency (NiUE) in tea plants through leaf chlorate sensitivity and identified key genes regulating nitrate uptake and metabolism. By comparing two contrasting cultivars—Zhenong 117 and Tieguanyin—the researchers found that the chlorate-sensitive Zhenong 117 exhibited superior nitrate transport and assimilation. Transcriptome analysis revealed enhanced expression of CsNRT2.4, CsNPF6.1, CsNPF4.6, CsNPF1.10, and CsNPF1.11 in high-efficiency genotypes. These findings provide a new molecular framework for nitrate utilization and offer potential marker genes to improve nitrogen efficiency in tea breeding.
Nitrogen fertilizers are heavily used in tea plantations to boost amino acid accumulation and enhance tea quality, often at the cost of soil and water health. However, excessive nitrogen application causes nitrate leaching and greenhouse gas emissions, threatening environmental sustainability. Traditional methods to evaluate nitrate utilization efficiency are time-consuming and environmentally sensitive, limiting their use in large-scale breeding programs. Moreover, the molecular coordination of nitrate transport and reduction in woody crops like tea remains poorly understood. Due to these challenges, it is necessary to explore rapid and precise strategies for characterizing nitrate use efficiency (NiUE) and identifying key regulatory genes in tea plants.
Researchers from the Tea Research Institute of the Chinese Academy of Agricultural Sciences have developed a novel leaf chlorate sensitivity assay to rapidly assess NiUE in tea plants. The study (DOI: 10.1093/hr/uhae354), published on April 1, 2025, in Horticulture Research, reveals how contrasting genotypes of Camellia sinensis respond to nitrate and chlorate treatments. By integrating physiological measurements with transcriptomic analysis, the team uncovered critical nitrate transporter and reductase genes that govern efficient nitrogen uptake and allocation, paving the way for greener and more productive tea cultivation.
Ten tea cultivars with distinct leaf colors and growth habits were screened using potassium nitrate (KNO₃) and potassium chlorate (KClO₃) treatments. The sensitive cultivar Zhenong 117 showed rapid decreases in SPAD and Fv/Fm values—indicators of chlorophyll content and photosystem II efficiency—while Tieguanyin displayed stable responses. Isotopic tracing confirmed that Zhenong 117 transported more ¹⁵N-labeled nitrate to new shoots, reflecting higher nitrate uptake and mobilization capacity.
Transcriptome sequencing revealed significant activation of genes involved in nitrate transport, reduction, and assimilation in Zhenong 117. Notably, CsNRT2.4 and CsNPF6.1 mediated xylem loading, while CsNPF4.6, CsNPF1.10, and CsNPF1.11 redistributed nitrate to growing tissues. Furthermore, the nitrate reductase CsNR and nitrite reductase CsFd-NiR were highly upregulated, enhancing conversion to amino acids. Coexpression network analysis identified SBP and bHLH transcription factors as potential regulators initiating nitrate signal transduction. The study proposes a molecular model in which nitrate activates hormonal pathways that drive transporter gene expression, thus improving nitrogen assimilation efficiency in high-performing cultivars.
“Our findings show that chlorate sensitivity can serve as a quick and noninvasive indicator of nitrate efficiency in woody plants,” said Prof. Lizhi Long, corresponding author of the study. “By identifying marker genes such as CsNRT2.4 and CsNPF6.1, we can guide molecular breeding toward tea varieties that use nitrogen more effectively. This not only improves yield and leaf quality but also reduces fertilizer dependence, aligning with the global goals of sustainable agriculture and environmental protection.”
The chlorate-based screening strategy offers a rapid, scalable, and environmentally friendly method for evaluating NiUE in perennial crops. Its integration with molecular markers can accelerate breeding for nitrogen-efficient tea varieties, reducing excessive fertilizer use and mitigating nitrogen runoff. Beyond tea, this approach may be adapted to other woody crops to identify nitrate-efficient genotypes. Future studies will validate these candidate genes under field conditions and further elucidate the regulatory network of nitrate signaling, ultimately supporting eco-friendly production systems and sustainable agricultural practices worldwide.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhae354
Funding information
This research was financially supported by the National Key Research and Development Project (grant no. 2021YFD1601100), Agricultural Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences (CAAS-ASTIP-TRICAAS), Earmarked Fund for China Agriculture Research System (grant no. CARS 19), and Department of Agriculture and Rural affairs in Zhejiang province (2023SNJF037).
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.