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Article|04 Aug 2022|OPEN
The high-quality genome of pummelo provides insights into the tissue-specific regulation of citric acid and anthocyanin during domestication
Zhihao Lu1 , Yue Huang1 , Sangyin Mao1 , Fangfang Wu2 , Yong Liu3 , Xiangqing Mao4 , Prakash Babu Adhikari1 , Yuantao Xu1 , Lun Wang1 , Hao Zuo1 , Muhammad Junaid Rao1,5 , Qiang Xu,1 ,
1Key Laboratory of Horticultural Plant Biology (Ministry of Education), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, Hubei 430070, China
2Science and Technology Innovation Research Center of Majia Pummelo, Guangfeng, Shangrao, Jiangxi 334000, China
3College of Agronomy, Jiangxi Agricultural University, Nanchang, Jiangxi 330045, China
4Service Center for Agriculture and Rural Area, Guangfeng, Shangrao, Jiangxi 334000, China
5State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Agriculture, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
*Corresponding author. E-mail: xuqiang@mail.hzau.edu.cn

Horticulture Research 9,
Article number: uhac175 (2022)
doi: https://doi.org/10.1093/hr/uhac175
Views: 95

Received: 28 Apr 2022
Accepted: 27 Jul 2022
Published online: 04 Aug 2022

Abstract

Citric acid and anthocyanin contents were co-selected during Citrus domestication. Pummelo is a founding species in the Citrus genus, but the domestication of pummelo has not been well studied. Here, we compared the citric acid and anthocyanin contents of a low citric acid pummelo (Citrus maxima LCA) and its high citric acid variety (HCA) from the same cultivation area in China. Our study revealed that, unlike the LCA type, the HCA variety accumulated anthocyanin in the pericarp early in fruit development. To investigate the genetic basis of acid and anthocyanin enrichment in HCA pulp and pericarp, respectively, we generated a chromosome-scale HCA genome using long-read sequence reads and Hi-C sequencing data. Transcriptome analysis and transient overexpression assays showed that the accumulation of citric acid and anthocyanin was associated with high expression of CgANTHOCYANIN1 (CgAN1), and two different MYBs transcription factors (CgPH4 and CgRuby1), respectively. Moreover, the CgAN1 promoter was more methylated in the LCA pulp than in the HCA pulp. Treatment with a DNA methylation inhibitor, 5-azacytidine, alleviated the CgAN1 promoter hypermethylation in the LCA pulp, leading to increased CgAN1 expression and citric acid content. This study provides a new high-quality pummelo genome and insight into the molecular mechanism behind the change in tissue-specific citric acid and anthocyanin accumulation during pummelo domestication and provides a conceptual basis for precise genetic manipulation in fruit flavor breeding.