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Journal of Integrative Agriculture
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AcMYB12 and AcMYB29 promote onion (Allium cepa L.) flavonols biosynthesis through transcriptional regulation

Qingwei Jia1, 2, Shuting Gai1, 2, Yiren Wang1, 2, Zhihui Zhang1, 2, Xiong Wu3, Wenhui Wu1, 2, Yumeng Pang1, 2, Xiaonan Zhang1, 2, Lei Qin1, 2#, Yong Wang1, 2#

1 College of Horticulture and Landscape Architecture, Northeast Agricultural University, Harbin 150030, China

2 Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Northeast Region), Ministry of Agriculture and Rural Affairs, Northeast Agricultural University, Harbin 150030, China

3 Henan Kanglong Hi-tech Seed Co., Ltd., Jiyuan 459000, China

 Highlights 

1. AcMYB12 and AcMYB29 are both functionally redundant and different in regulating flavonol biosynthesis.

2. The binding activity of AcMYB12 and AcMYB29 with cis-elements lead to difference in their regulatory functions.

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摘要  

黄酮醇具有很高的药用价值,不但在植物抗逆性具有重要作用而且也是洋葱营养价值的关键组成部分,尤其是在可食用部分。虽然黄酮醇的生物合成途径已经得到了很好的研究,但在洋葱中的调控作用尚不完全清楚。本研究通过分析“SA1”不同发育阶段的转录组学和代谢组学数据,筛选到了黄酮醇生物合成和调控基因。其中,鉴定了两个R2R3-MYB转录因子AcMYB12AcMYB29洋葱黄酮醇生物合成的正调控因子。转录激活实验表明,它们都能激活黄酮醇生物合成途径基因AcCHSAcF3’HAcFLS的转录,而酵母单杂交实验证实它们直接结合这些基因的启动子。过表达洋葱愈伤组织和拟南芥中黄酮醇途径基因的表达量和黄酮醇含量显著高于对照,进一步证实AcMYB29AcMYB12在黄酮醇调控中的作用。瞬时沉默试验显示两者之间存在部分功能冗余。有趣的是,他们的调节能力也存在显著差异。AcMYB12主要调控黄酮醇积累,而AcMYB29主要调控槲皮素的合成。进一步研究了它们之间的差异调控的分子机制,结果表明,这些差异可能是由于黄酮醇生物合成途径基因启动子中顺式元件的多样性以及转录因子和顺式元件之间结合活性的差异。



Abstract  

Flavonols have high medical value and are crucial for plant stress resistance. They are also key components of the nutritional value in onions, particularly in the edible parts. Although the flavonol biosynthetic pathway is well studied, its regulation in onions is not fully understood. This study screened flavonol biosynthesis and regulatory genes by analyzing transcriptome and metabolomics data from different developmental stages of “SA1.” Two R2R3-MYB transcription factors, AcMYB12 and AcMYB29, were identified as positive regulators of onion flavonol biosynthesis. Transcriptional activation assays showed that both could activate AcCHS, AcF3’H, and AcFLS. Yeast one-hybrid assays confirmed they directly bind to the promoters of these genes. Flavonol pathway genes expression and flavonol content in overexpressed onion callus and Arabidopsis were significantly higher than in controls, supporting the role of AcMYB29 and AcMYB12 in flavonol regulation. Instantaneous silencing tests revealed partial functional redundancy between the two. Interestingly, There were also significant differences in their ability to regulate. AcMYB12 mainly regulates flavonol accumulation, whereas AcMYB29 focuses on quercetin. We further investigated the molecular mechanisms of differential regulation, likely due to variations in cis-elements in flavonol pathway gene promoters and differences in binding activity between transcription factors and cis-elements.

Keywords:  onion       flavonols       quercetin       R2R3-MYB       cis-element  
Online: 24 June 2025  
Fund: 

This work was supported by Key R & D Projects in Heilongjiang Province [GA21B012]; Collaborative Innovation Achievement Project of Heilongjiang Province University [LJGXCG2022-040].

About author:  Qingwei Jia, E-mail: 465872232@qq.com; #Correspondence Lei Qin, Tel: +86-451-55191261, E-mail: qinlei@neau.edu.cn; Yong Wang, Tel: +86-451-55190243, E-mail: yongwang@neau.edu.cn

Cite this article: 

Qingwei Jia, Shuting Gai, Yiren Wang, Zhihui Zhang, Xiong Wu, Wenhui Wu, Yumeng Pang, Xiaonan Zhang, Lei Qin, Yong Wang. 2025. AcMYB12 and AcMYB29 promote onion (Allium cepa L.) flavonols biosynthesis through transcriptional regulation. Journal of Integrative Agriculture, Doi:10.1016/j.jia.2025.06.023

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