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<p>Amid growing labor shortages, mechanized harvesting is an inevitable trend replacing labor-intensive manual tea plucking. Internode length is a key genetic trait determining the suitability of tea plants for mechanical harvesting, yet its underlying regulatory mechanisms remain unclear. To elucidate this, we performed an integrated analysis of phytohormone metabolomes and transcriptomes in stem nodes of tea plant cultivars with contrasting internode lengths. We observed that long-internode cultivars exhibited lower levels of growth-promoting hormones, including cytokinins, gibberellins, and brassinosteroids. Transcriptome analysis identified 5162 differentially expressed genes, primarily enriched in secondary metabolite biosynthesis, hormone signal transduction, and zeatin biosynthesis pathways. Mechanistically, long-internode cultivars appear to employ a coordinated network that may promote elongation: auxin signaling shows transcriptomic signatures consistent with enhancement; bioactive gibberellins (e.g., GA₃) show reduced levels while their metabolic precursors and catabolites (GA₅₃, GA₁₉, GA₃₄) accumulate; Compared to the short-internode cultivar, long-internode cultivars exhibited lower steady-state levels of bioactive cytokinins, suggesting a pattern of reduced cytokinin storage under the sampled conditions. Additionally, brassinosteroid synthesis appears constrained while its perception-related genes are upregulated. Furthermore, although abscisic acid levels did not increase, genes governing its metabolism and perception were pre-emptively upregulated. This suggests a unique mechanism that may enable the coexistence of low hormone levels, high elongation capacity, and a preparatory stress-responsive state. Conversely, short-internode cultivars showed expression patterns consistent with restriced elongation, including reduced auxin signaling and metabolism while maintaining robust cytokinin homeostasis. This study provides a comprehensive metabolomic and transcriptomic analysis of tea plant stem nodes, offering correlative insights and candidate molecular targets for further investigation in breeding elite cultivars optimized for mechanical harvesting.</p>

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Comprehensive Analysis of Phytohormone Contents and Transcriptome Reveals the Mechanism Underlying Internode Elongation in New Shoot of Tea Plants

  • 期刊论文

  • 发表日期：

    2026年6月30日

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  • Xiaoman Li,
  • Jinping Zhu,
  • Hanjia Li,
  • Lu Wang,
  • Jianyan Huang,
  • Xinyuan Hao,
  • Xinchao Wang,
  • Jianming Zeng

摘要

Amid growing labor shortages, mechanized harvesting is an inevitable trend replacing labor-intensive manual tea plucking. Internode length is a key genetic trait determining the suitability of tea plants for mechanical harvesting, yet its underlying regulatory mechanisms remain unclear. To elucidate this, we performed an integrated analysis of phytohormone metabolomes and transcriptomes in stem nodes of tea plant cultivars with contrasting internode lengths. We observed that long-internode cultivars exhibited lower levels of growth-promoting hormones, including cytokinins, gibberellins, and brassinosteroids. Transcriptome analysis identified 5162 differentially expressed genes, primarily enriched in secondary metabolite biosynthesis, hormone signal transduction, and zeatin biosynthesis pathways. Mechanistically, long-internode cultivars appear to employ a coordinated network that may promote elongation: auxin signaling shows transcriptomic signatures consistent with enhancement; bioactive gibberellins (e.g., GA₃) show reduced levels while their metabolic precursors and catabolites (GA₅₃, GA₁₉, GA₃₄) accumulate; Compared to the short-internode cultivar, long-internode cultivars exhibited lower steady-state levels of bioactive cytokinins, suggesting a pattern of reduced cytokinin storage under the sampled conditions. Additionally, brassinosteroid synthesis appears constrained while its perception-related genes are upregulated. Furthermore, although abscisic acid levels did not increase, genes governing its metabolism and perception were pre-emptively upregulated. This suggests a unique mechanism that may enable the coexistence of low hormone levels, high elongation capacity, and a preparatory stress-responsive state. Conversely, short-internode cultivars showed expression patterns consistent with restriced elongation, including reduced auxin signaling and metabolism while maintaining robust cytokinin homeostasis. This study provides a comprehensive metabolomic and transcriptomic analysis of tea plant stem nodes, offering correlative insights and candidate molecular targets for further investigation in breeding elite cultivars optimized for mechanical harvesting.