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Article|22 Apr 2022|OPEN
Comparative methylomics and chromatin accessibility analysis in Osmanthus fragrans uncovers regulation of genic transcription and mechanisms of key floral scent production
Yuanji Han1 , , Miaomiao Lu1 , Shumin Yue1 , Ke Li1 , Meifang Dong1 , Luxian Liu1 , Hongyun Wang1 and Fude Shang,1,2 ,
1State Key Laboratory of Crop Stress Adaptation and Improvement, Laboratory of Plant Germplasm and Genetic Engineering, School of Life Sciences, Henan University, Kaifeng, Henan 475004, China
2Henan Engineering Research Center for Osmanthus Germplasm Innovation and Resource Utilization, Henan Agricultural University, Zhengzhou, Henan 450002, China
*Corresponding author. E-mail: wolianghan@163.com,fudeshang@henu.edu.cn

Horticulture Research 9,
Article number: uhac096 (2022)
doi: https://doi.org/10.1093/hr/uhac096
Views: 168

Received: 10 Dec 2021
Accepted: 07 Apr 2022
Published online: 22 Apr 2022

Abstract

Linalool and ionone are two important aromatic components in sweet osmanthus petals, and the regulatory mechanisms that produce these two components remain unclear. In this study, we employed whole-genome methylation sequencing and ATAC-seq technology to analyze the genomic DNA methylation status and chromatin accessibility of the sweet osmanthus cultivars ‘Zaohuang’ and ‘Chenghong Dangui’. Results showed that the promoter region of TPS2, a key gene in the linalool synthesis pathway, was less methylated in ‘Chenghong Dangui’ than in ‘Zaohuang’. The chromatin was more accessible in ‘Chenghong Dangui’ than in ‘Zaohuang’, which resulted in a much stronger expression of this gene in ‘Chenghong Dangui’ than in ‘Zaohuang’. This eventually led to a high quantity of linalool and its oxides in the petals of ‘Chenghong Dangui’, but there were lower levels present in the petals of ‘Zaohuang’. These results suggest that DNA methylation and chromatin accessibility play major roles in linalool synthesis in sweet osmanthus. The methylation level of the promoter region of CCD4, a key gene for ionone synthesis, was higher in ‘Zaohuang’ than in ‘Chenghong Dangui’. The chromatin accessibility was lower in ‘Zaohuang’ than in ‘Chenghong Dangui’, although the expression of this gene was significantly higher in ‘Zaohuang’ than in ‘Chenghong Dangui’. ChIP-seq analysis and a series of experiments showed that the differential expression of CCD4 and CCD1 in the two cultivars may predominantly be the result of regulation by ERF2 and other transcription factors. However, a 183-bp deletion involving the CCD4 promoter region in ‘Chenghong Dangui’ may be the main reason for the low expression of this gene in its petals. This study provides an important theoretical basis for improving selective breeding of key floral fragrance components in sweet osmanthus.