缺硝态氮胁迫茶树根尖转录组及调控网络解析

Transcriptome Analysis and Regulatory Network Elucidation of Tea Plants (Camellia sinensis L.) Root Tips Under Nitrate Deficiency Stress

摘要

硝酸盐(NO₃^-)是茶树生长发育的主要氮源之一，其供应变化直接影响氮代谢稳态及品质形成。为解析茶树响应 NO₃^-缺乏的分子机制，本研究以“龙井 43”为材料，设置 0~12h 时间梯度处理，结合生理指标测定、转录组测序与 qPCR 验证，系统解析其时间动态响应机制。结果显示，茶树在短时 NO₃^-缺乏胁迫下，叶片 Fv/Fm 值与游离氨基酸含量显著下降，根系 NO₃^-与 NH₄⁺含量同步减少，表明其光合能力与氮素代谢受限。转录组分析进一步筛选到 2407 个差异表达基因(differentially expressed genes, DEGs)，GO 和 KEGG 富集分析显示其主要富集于碳水化合物代谢、胁迫响应、苯丙烷与黄酮合成、植物激素及 MAPK 等信号通路。CsNiR 和 CsNPF5.7 硝酸还原与转运相关基因持续下调，暗示初级氮同化通路受阻；而 CsGDH2.1 和 CsAS 表达显著上调，提示茶树可能通过优化碳氮代谢与信号调控以实现快速适应。本研究揭示了茶树在 NO₃^-缺乏胁迫下的分子调控模式，为茶树氮高效利用机制解析与功能基因挖掘提供理论基础。

Abstract

Nitrate(NO₃^-)is one of the major nitrogen sources for tea plant growth and development, and fluctuations in its supply directly affect nitrogen metabolic homeostasis and tea quality formation. To elucidate the molecular mechanisms underlying the response of tea plants to NO₃^-deficiency, the cultivar “Longjing 43”was subjected to a time course treatment(0-12h). Physiological measurements were integrated with transcriptome sequencing and qPCR validation to characterize the dynamic responses to NO₃^-deprivation. The results showed that short term NO₃^-deficiency significantly reduced leaf Fv/Fm and free amino acid contents, accompanied by simultaneous decreases in root NO₃^-and NH₄⁺contents, indicating inhibition of photosynthetic performance and nitrogen metabolism. A total of 2,407 differentially expressed genes(DEGs)were identified. GO and KEGG enrichment analyses revealed that these DEGs were mainly involved in carbohydrate metabolism, stress responses, phenylpropanoid and flavonoid biosynthesis, plant hormone and MAPK related signaling pathways. The nitrate reduction and transport related genes CsNiR and CsNPF5.7 were consistently downregulated, suggesting suppression of primary nitrogen assimilation, whereas CsGDH2.1 and CsAS were significantly upregulated, indicating that tea plants may enhance their tolerance to nitrogen deficiency through coordinated regulation of carbon-nitrogen metabolism and stress related signaling. This study reveals the molecular regulatory patterns of tea plants under NO₃^-deficiency and provides a theoretical basis for elucidating nitrogen use efficiency mechanisms and identifying candidate functional genes in tea plants.

关键词

茶树 / 硝态氮胁迫 / 差异表达基因 / 转录组分析 / 游离氨基酸 / 氮代谢

Key words

Camellia sinensis / nitrate deficiency / differentially expressed genes(DEGs) / RNA-Seq / free amino acid / nitrogen metabolism

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基金资助

国家自然科学基金项目(32202536)

浙江农林大学科研发展基金项目(2024FR012)