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Brassinosteroid signaling regulates floral transition defects in Camellia sinensis 'Ziyang 1' via CsBZR2-mediated suppression of CsFLC

Yingao Zhang1*, Huike Li1*, Siqing Wan1, Yongheng Zhang2, Dan Chen1, He Zhang1, Yezi Xiao1, Lu Liu1, Pengjie Wang1#, Youben Yu1#

1 College of Horticulture, Northwest A&F University, Yangling 712100, China

2 Key Laboratory of Biology, Genetics and Breeding of Special Economic Animals and Plants, Ministry of Agriculture andRural Affairs, National Center for Tea Plant Improvement, Tea Research Institute, Chinese Academy of Agricultural Sciences,9th South of Meiling Road, Hangzhou 310008, China

 Highlights 

1. The non-flowering tea mutant ZY1H provides a unique germplasm to explore floral induction mechanisms.

2. CsBZR2-mediated repression of CsFLC and altered brassinosteroid signaling are implicated in disrupting floral transition in ZY1H.

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摘要  

茶树(Camellia sinensis)是重要的叶用经济作物,但其开花过程会消耗大量养分,显著降低茶叶产量与品质。因此,解析茶树成花转变的分子机制,对茶树品种改良和茶园管理优化具有重要意义。本研究以自然突变体‘紫阳1号’(ZY1H,连续多年不开花)及其自然群体‘紫阳群体种’(ZYQT,正常开花)为研究对象,探讨 ZY1H 不开花表型的分子机制。表型观察发现,ZY1H 节间缩短、营养生长持续且未形成花分生组织。染色体分析表明,ZY1H 染色体数目正常(2n=30),排除了三倍体不育的可能性。转录组分析揭示,ZY1H 存在营养生长向生殖生长转变的缺陷,具体表现为 SPL 基因表达不足,且抑花 AP2-like 基因持续高表达;同时,开花抑制因子 SVP 的高表达与开花整合因子 FT 的低表达,进一步破坏了开花信号的整合过程。值得注意的是,ZY1H 中油菜素内酯(BR)含量及其下游调控因子CsBZR2的表达水平均显著升高。功能验证结果表明,CsBZR2可直接结合CsFLC启动子并抑制其表达,从而影响成花进程。本研究表明,ZY1H 的成花缺陷可能由BR 信号通路的异常激活及过度营养生长共同驱动,为深入理解茶树开花调控的分子机制提供了新的见解,并为茶树品种改良提供了理论参考。



Abstract  

The tea plant (Camellia sinensis) is an economically important leaf crop in which the flowering process consumes substantial nutrients, thereby negatively impacting tea yield and quality. Therefore, deciphering the molecular basis of floral transition is essential for enhancing tea cultivars and optimizing plantation management. The natural mutant ‘Ziyang 1’ (ZY1H, which had not flowered for years) and its wild-type cultivar ‘Ziyang’ (ZYQT, normal flowering) were used to study the molecular mechanisms underlying the non-flowering phenotype in ZY1H. Phenotypically, ZY1H exhibited shortened internodes, prolonged vegetative growth, and failure to develop floral meristems. Chromosomal analysis confirmed that ZY1H maintains a normal diploid chromosome number (2n=30), excluding triploidy as a cause of its sterility. Transcriptome analysis revealed defective vegetative-to-reproductive transition in ZY1H, manifesting as insufficient expression of SPL genes and sustained high expression of flower-inhibiting AP2-like genes. Additionally, elevated expression of the flowering repressor SVP and reduced expression of the flowering integrator FT further disrupted the integration of floral induction signals. Notably, brassinosteroid (BR) levels and CsBZR2 expression were elevated in ZY1H. Functional assays showed that CsBZR2 directly interacts with the CsFLC promoter and suppresses its expression, thereby blocking the flowering process. These findings suggest that the floral transition defect in ZY1H is driven by dysregulated BR signaling and excessive vegetative growth, to provide novel insights into the molecular mechanisms of flowering regulation in tea plants and valuable theoretical support for cultivar improvement.

Keywords:  tea plant       floral induction       CsBZR2       flowering       CsFLC  
Online: 31 December 2025  
Fund: 

This study was supported by the National Key Research and Development Program (Grant No. 2022YFD1602003), the China Agriculture Research System of the Ministry of Finance and Ministry of Agriculture and Rural Affairs (Grant No. CARS-19), and the University Extension Project of Xixiang Tea Experimental Demonstration Station (Grant No. XTG2023-04).

About author:  #Correspondence Youben Yu, E-mail: yyben@163.com; Pengjie Wang, E-mail: wpjtea@163.com *These authors contributed equally to this study.

Cite this article: 

Yingao Zhang, Huike Li, Siqing Wan, Yongheng Zhang, Dan Chen, He Zhang, Yezi Xiao, Lu Liu, Pengjie Wang, Youben Yu. 2025. Brassinosteroid signaling regulates floral transition defects in Camellia sinensis 'Ziyang 1' via CsBZR2-mediated suppression of CsFLC. Journal of Integrative Agriculture, Doi:10.1016/j.jia.2025.12.073

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