Dataset Information

Expression and functional analysis of the nobiletin biosynthesis-related gene CitOMT in citrus fruit.

ABSTRACT: Nobiletin, a polymethoxy flavone (PMF), is specific to citrus and has been reported to exhibit important health-supporting properties. Nobiletin has six methoxy groups at the 3',4',5,6,7,8-positions, which are catalyzed by O-methyltransferases (OMTs). To date, researches on OMTs in citrus fruit are still limited. In the present study, a novel OMT gene (CitOMT) was isolated from two citrus varieties Satsuma mandarin (Citrus unshiu Marc.) and Ponkan mandarin (Citrus reticulata Blanco), and its function was characterized in vitro. The results showed that the expression of CitOMT in the flavedo of Ponkan mandarin was much higher than that of Satsuma mandarin during maturation, which was consistent with the higher accumulation of nobiletin in Ponkan mandarin. In addition, functional analysis showed that the recombinant protein of CitOMT had methylation activity to transfer a methyl group to 3'-hydroxy group of flavones in vitro. Because methylation at the 3'-position of flavones is vital for the nobiletin biosynthesis, CitOMT may be a key gene responsible for nobiletin biosynthesis in citrus fruit. The results presented in this study will provide new strategies to enhance nobiletin accumulation and improve the nutritional qualities of citrus fruit.

SUBMITTER: Seoka M

PROVIDER: S-EPMC7498457 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Expression and functional analysis of the nobiletin biosynthesis-related gene CitOMT in citrus fruit.

Seoka Mao M Ma Gang G Zhang Lancui L Yahata Masaki M Yamawaki Kazuki K Kan Toshiyuki T Kato Masaya M

Scientific reports 20200917 1

Nobiletin, a polymethoxy flavone (PMF), is specific to citrus and has been reported to exhibit important health-supporting properties. Nobiletin has six methoxy groups at the 3',4',5,6,7,8-positions, which are catalyzed by O-methyltransferases (OMTs). To date, researches on OMTs in citrus fruit are still limited. In the present study, a novel OMT gene (CitOMT) was isolated from two citrus varieties Satsuma mandarin (Citrus unshiu Marc.) and Ponkan mandarin (Citrus reticulata Blanco), and its fun ...[more]

PMID: 32943728

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Project description:BackgroundXanthophylls are oxygenated carotenoids and fulfill critical roles in plant growth and development. In plants, two different types of carotene hydroxylases, non-heme di-iron and heme-containing cytochrome P450, were reported to be involved in the biosynthesis of xanthophyll. Citrus fruits accumulate a high amount of xanthophylls, especially β,β-xanthophylls. To date, however, the roles of carotene hydroxylases in regulating xanthophyll content and composition have not been elucidated.ResultsIn the present study, the roles of four carotene hydroxylase genes (CitHYb, CitCYP97A, CitCYP97B, and CitCYP97C) in the biosynthesis of xanthophyll in citrus fruits were investigated. Phylogenetic analysis showed that the four citrus carotene hydroxylases presented in four distinct clusters which have been identified in higher plants. CitHYb was a non-heme di-iron carotene hydroxylase, while CitCYP97A, CitCYP97B, and CitCYP97C were heme-containing cytochrome P450-type carotene hydroxylases. Gene expression results showed that the expression of CitHYb increased in the flavedo and juice sacs during the ripening process, which was well consistent with the accumulation of β,β-xanthophyll in citrus fruits. The expression of CitCYP97A and CitCYP97C increased with a peak in November, which might lead to an increase of lutein in the juice sacs during the ripening process. The expression level of CitCYP97B was much lower than that of CitHYb, CitCYP97A, and CitCYP97C in the juice sacs during the ripening process. Functional analysis showed that the CitHYb was able to catalyze the hydroxylation of the β-rings of β-carotene and α-carotene in Escherichia coli BL21 (DE3) cells. Meanwhile, when CitHYb was co-expressed with CitCYP97C, α-carotene was hydroxylated on the β-ring and ε-ring sequentially to produce lutein.ConclusionsCitHYb was a key gene for β,β-xanthophyll biosynthesis in citrus fruits. CitCYP97C functioned as an ε-ring hydroxylase to produce lutein using zeinoxanthin as a substrate. The results will contribute to elucidating xanthophyll biosynthesis in citrus fruits, and provide new strategies to improve the nutritional and commercial qualities of citrus fruits.

Dataset Information

Expression and functional analysis of the nobiletin biosynthesis-related gene CitOMT in citrus fruit.

Publications

Expression and functional analysis of the nobiletin biosynthesis-related gene CitOMT in citrus fruit.

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