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Article|18 Jan 2022|OPEN
Illustration of the variation in the content of flavanone rutinosides in various citrus germplasms from genetic and enzymatic perspectives
Wenyun Li1,2 ,† , Gu Li1 ,† , Ziyu Yuan1 , Mingyue Li1 , Xiuxin Deng1 , Meilian Tan3 , Yuhua Ma2 and Jiajing Chen1 , , Juan Xu,1 ,
1Key Laboratory of Horticultural Plant Biology (Ministry of Education), College of Horticulture and Forestry, Huazhong Agricultural University, No.1 Shizishan Street, Hongshan District, Wuhan 430070, China
2Guizhou Fruit Institute, Guizhou Academy of Agricultural Sciences, No.1 Jinnong Road, Huaxi District, Guiyang 550006, China
3The Oil Crops Research Institute of the Chinese Academy of Agricultural Sciences, No.2 Xudong Second Road, Wuchang District, Wuhan 430062, China
*Corresponding author. E-mail: jiajingchen@webmail.hzau.edu.cn,xujuan@mail.hzau.edu.cn
Both authors contributed equally to the study.

Horticulture Research 9,
Article number: uhab017 (2022)
doi: https://doi.org/10.1093/hr/uhab017
Views: 20

Received: 11 Mar 2021
Revised: 16 Jul 2021
Accepted: 30 Aug 2021
Published online: 18 Jan 2022

Abstract

In citrus, 1,6-rhamnosytransferase (1,6RhaT) and 1,2-rhamnosytransferase (1,2RhaT) catalyze flavanone-7-O-glucosides to form nonbitter flavanone rutinosides (FRs) and bitter flavanone neohesperidosides (FNs), respectively. As revealed in this study of fruit peels from 36 citrus accessions, FRs varied from undetectable levels in pummelo and kumquat to being the dominant flavonoids in sweet orange and loose-skin mandarins. Furthermore, a previously annotated full-length 1,6RhaT-like gene was identified as another 1,6RhaT-encoding gene by in vitro experiments. In total, 28 alleles of full-length 1,6RhaTs were isolated and classified into A, B and C types with only type A alleles encoding a functional protein. Coincidently, only the accessions that contained FRs harbored type A alleles, as was further verified in two F1 hybrid populations. Moreover, the inferior substrate conversion efficiency of 1,6RhaTs in comparison with that of 1,2RhaT in vitro might partly explain the lower proportions of FRs to total flavanone disaccharides in citrus hybrids harboring both functional rhamnosyltransferases. Our findings provide a better understanding of FR content variations among citrus and are meaningful for a mechanistic illustration of citrus flavonoid metabolism and fruit quality improvement practices.