Promoter and coding sequence diversity of CsCCD1 may contribute to the differential accumulation of floral β-ionone in fresh tea leaves
Jingming Wang, Mingyue Zhao, Ting Gao, Yingying Feng, Feiquan Wang, Yuting Pan, Jieyang Jin, Tingting Jing, Mengqian Lu, Mengting Zhang, Danyang Guo, Xiaochun Wan, Wilfried Schwab, Chuankui Song
Abstract
The carotenoid-derived volatile β-ionone makes an important contribution to tea fragrance. Here, we qualitatively and quantitatively analysed 15 carotenoids in tea leaves of 13 cultivars by UHPLC-APCI-MS/MS. The 13 cultivars were divided into two groups by PCA (Principal Component Analysis) clustering analysis of their carotenoid content, and OPLS-DA (Orthogonal projections to latent structures) indicated that the levels of β-carotene (VIP = 2.89) and lutein (VIP = 2.30) were responsible for much of the variation between the two groups. Interestingly, the β-carotene to β-ionone conversion rates in Group 1 were higher than in Group 2, while the β-carotene content was significantly lower in Group 1 than in Group 2. The β-ionone content was significantly higher in Group 1. Pearson Correlation Coefficient calculation between the transcription level of candidate genes (CsCCD1 and CsCCD4) and the accumulation of β-ionone indicated that CsCCD1 may involve in the formation of β-ionone in 13 cultivars. Prokaryotic expression and in vitro enzyme activity assays showed that ‘Chuanhuang 1’ had an amino acid mutation in carotenoid cleavage dioxygenases 1 (CsCCD1) compared with ‘Shuchazao’, resulting in a significantly higher β-ionone content in ‘Chuanhuang 1’. Sequence analysis showed that ‘Chuanhuang 1’ and ‘Huangdan’ had different CsCCD1 promoter sequences, leading to significantly higher CsCCD1 expression and β-ionone accumulation in ‘Chuanhuang 1’. These results indicated that the promoter and coding sequence diversity of CsCCD1 might contribute to the differential accumulation of β-ionone in different tea cultivars.