Characterization of nitrate use efficiency in tea plant (Camellia sinensis) based on leaf chlorate sensitivity

Abstract

Nitrate (NO₃⁻), a key form of inorganic nitrogen (N) in soils, is typically lost in tea gardens through leaching. However, NO₃⁻ utilization efficiency (NiUE) and its characteristic mechanism in tea plants remain unclear. This study screened contrastive genotypes of NiUE using leaf chlorate sensitivity and explored the potential genes that regulate this process. Fresh branches of 10 cultivars were hydroponically cultivated and subjected to potassium nitrate (KNO₃) and potassium chlorate (KClO₃) treatments, with the former as the control group. The sensitive cultivar, Zhenong 117 (ZN117), showed a decrease in SPAD and F_v/F_m values following KClO₃ treatment, while the tolerant cultivar, Teiguanyin (TGY), exhibited minimal significant changes. After 5 days of cultivation, the ¹⁵N concentration and proportion in new shoots of ZN117 were significantly higher than those in TGY. Transcriptome analysis revealed that the expression of genes responsible for NO₃⁻ transport, including the nitrate transporters NRT2.4, NPF4.6, NPF6.1, NPF1.10, and NPF1.11, significantly increased in ZN117 after NO₃⁻ supply. Genes involved in NO₃⁻ reduction, chlorophyll synthesis, and photosynthesis were progressively induced. Coexpression network analysis indicated that the squamosa promoter-binding protein activated the onset of NO₃⁻ signaling, while basic helix-loop-helix transcripts were triggered to higher levels during NO₃⁻ supply. This study proposes a rapid characterization method of NiUE in woody plants and a speculative molecular regulatory mechanism for the NO₃⁻ transfer and remobilization of tea plants. A set of specific genes involved in NO₃⁻ transport, reduction, and mobilization were identified and proposed as marker genes for NiUE in tea plants.

Acknowledgements

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). We thank Ms. Haitao Li and Ms. Li Fang for experimental assistance.

Author contributions

J.R. and L.L. conceived and designed research; W.Z. and X.D. carried out the experiments; K.N. and L.M. participated in the experiment and managed experimental field; W.Z. interpreted the research results and drafted the manuscript; L.L. supervised the experiment; L.L. and J.R. guided data analysis and revised the manuscript. All authors have read and agreed to the published version of the manuscript.

Data availability

RNA-Sequencing data in this study can be found at Sequence Read Archive of NCBI (https://www.ncbi.nlm.nih.gov/sra), the accession number SRA: PRJNA1066199.

Conflict of interest

The authors declare that they have no conflict of interest.

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