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Journal of Integrative Agriculture  2025, Vol. 24 Issue (6): 2217-2228    DOI: 10.1016/j.jia.2024.12.032
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Transcriptome-based analysis of lignin accumulation in the regulation of fruit stone development and endocarp hardening in Chinese jujube

Xinyi Mao1*, Xuan Zhao1, 2*, Zhi Luo1*, Ao He1*, Meng Yang1, Mengjun Liu1, 2, Jin Zhao3#, Ping Liu1, 2#

1 College of Horticulture, Hebei Agricultural University, Baoding 071001, China

2 Research Center of Chinese Jujube, Hebei Agricultural University, Baoding 071001, China

3 College of Life Science, Hebei Agricultural University, Baoding 071000, China

 Highlights 
RNA-Seq analysis of three jujube cultivars across key endocarp developmental stages revealed dynamic gene expression networks critical for regulating stone formation in Chinese jujube.
Lignin accumulation in the endocarp, regulated by ZjF6H1-3, ZjPOD genes, and bHLH transcription factors, is pivotal for stone formation in jujube.
This study offers novel molecular insights and a framework for breeding stoneless jujube cultivars through targeted manipulation of lignin-related genes and transcriptional networks.
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摘要  

核果进化出一种极其坚硬的木质外壳,称为果核,用以保护种子。如今,无核栽培品种的市场价值急剧上升,这就提出了培育无核果实的需求。因此,迫切需要了解果核的内在机理。我们利用中国枣的一个有核栽培品种有核和两个无核栽培品种无核大果无核,对枣果核发育机理进行了全面研究。通过解剖分析和木质素染色检测发现,有核栽培品种有核的内果皮木质素积累量远高于其他两个无核栽培品种。木质素积累可能是形成果核的关键原因。通过分析转录组数据并识别其中的差异表达基因(DEGs),发现有核无核丰以及有核大果无核之间有49个重叠的DEGs。其中,参与木质素合成的ZjF6H1-3ZjPOD被鉴定出来。在野生酸枣幼苗上过表达和沉默ZjF6H1-3ZjPOD进一步验证了它们在木质素合成中的作用。此外,在这49个重叠的DEGs中还包括两个bHLH转录因子,并且在ZjF6H1-3ZjPOD的启动子中发现了bHLH转录因子基序,这表明bHLH转录因子也参与了木质素的合成。



Abstract  

Stone fruits, also known as drupes, have evolved an extremely hard wood-like shell called a stone to protect the seeds.  Recently, the market value of stoneless cultivars has risen dramatically, which highlights the need to cultivate stoneless fruit.  Therefore, determining the underlying mechanism of fruit stone development is urgently needed.  By employing the stone-containing jujube cultivar ‘Youhe’ and two stoneless Chinese jujube cultivars, ‘Wuhefeng’ and ‘Daguowuhe’, we comprehensively studied the mechanism of fruit stone development in jujube.  Anatomical analysis and lignin staining revealed that the stone cultivar ‘Youhe’ jujube exhibited much greater lignin accumulation in the endocarp than the two stoneless cultivars.  Lignin accumulation may be the key factor in fruit stone formation.  By analyzing the transcriptome data and identifying differentially expressed genes (DEGs), 49 overlapping DEGs were identified in the comparisons of ‘Youhe’ jujube vs. ‘Wuhefeng’ jujube and ‘Youhe’ jujube vs. ‘Daguowuhe’ jujube.  ZjF6H1-3 and ZjPOD, which are involved in lignin synthesis, were identified among these DEGs.  The overexpression and silencing of ZjF6H1-3 and ZjPOD in wild jujube seedlings further confirmed their roles in lignin synthesis.  In addition, two bHLH transcription factors were included in the 49 overlapping DEGs, and bHLH transcription factor binding motifs were found in the promoters of ZjF6H1-3 and ZjPOD, indicating that bHLH transcription factors are also involved in lignin synthesis and stone formation in Chinese jujube.  This study provides new insights into the molecular networks underlying fruit stone formation and can serve as an important reference for the molecular design and breeding of stoneless fruit cultivars of jujube and fruit trees.

Keywords:  Chinese jujube       fruit stone        lignin        endocarp        phenylpropanoid pathway        transcriptome analysis  
Received: 03 February 2024   Online: 30 December 2024   Accepted: 28 November 2024
Fund: 

This research was supported by the Central Fund for Promoting Innovative Technology Development, China (236Z6801G), the Hebei Provincial Modern Seed Industry Technology Innovation Team - Dried Fruits, China (21326304D), and the Construction of Innovative Teams for the Modern Agricultural Industry System in Hebei Province, China (HBCT2023120210, HBCT2024190203).

About author:  #Correspondence Jin Zhao, E-mail: zhaojinbd@126.com; Ping Liu, E-mail: yylp@hebau.edu.cn *These authors contributed equally to this study.

Cite this article: 

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