Abstract
In this study, the pathway of β-citraurin biosynthesis, carotenoid contents and the expression of genes related to carotenoid metabolism were investigated in two varieties of Satsuma mandarin (Citrus unshiu), Yamashitabeni-wase, which accumulates β-citraurin predominantly, and Miyagawa-wase, which does not accumulate β-citraurin. The results suggested that CitCCD4 (for Carotenoid Cleavage Dioxygenase4) was a key gene contributing to the biosynthesis of β-citraurin. In the flavedo of Yamashitabeni-wase, the expression of CitCCD4 increased rapidly from September, which was consistent with the accumulation of β-citraurin. In the flavedo of Miyagawa-wase, the expression of CitCCD4 remained at an extremely low level during the ripening process, which was consistent with the absence of β-citraurin. Functional analysis showed that the CitCCD4 enzyme exhibited substrate specificity. It cleaved β-cryptoxanthin and zeaxanthin at the 7,8 or 7',8' position. But other carotenoids tested in this study (lycopene, α-carotene, β-carotene, all-trans-violaxanthin, and 9-cis-violaxanthin) were not cleaved by the CitCCD4 enzyme. The cleavage of β-cryptoxanthin and zeaxanthin by CitCCD4 led to the formation of β-citraurin. Additionally, with ethylene and red light-emitting diode light treatments, the gene expression of CitCCD4 was up-regulated in the flavedo of Yamashitabeni-wase. These increases in the expression of CitCCD4 were consistent with the accumulation of β-citraurin in the two treatments. These results might provide new strategies to improve the carotenoid contents and compositions of citrus fruits.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Carotenoids / metabolism*
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Chromatography, High Pressure Liquid
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Citrus / drug effects
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Citrus / enzymology*
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Citrus / genetics
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Citrus / radiation effects
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Cryptoxanthins
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DNA, Complementary / genetics
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DNA, Complementary / isolation & purification
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Dioxygenases / metabolism*
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Ethylenes / pharmacology
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Gene Expression Regulation, Plant / drug effects
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Gene Expression Regulation, Plant / radiation effects
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Genes, Plant / genetics
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Green Fluorescent Proteins / metabolism
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Light
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Metabolic Networks and Pathways / drug effects
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Metabolic Networks and Pathways / genetics
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Metabolic Networks and Pathways / radiation effects
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Molecular Sequence Data
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Nicotiana / drug effects
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Nicotiana / genetics
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Nicotiana / metabolism
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Nicotiana / radiation effects
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Plant Leaves / drug effects
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Plant Leaves / metabolism
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Plant Leaves / radiation effects
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Plants, Genetically Modified
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Recombinant Fusion Proteins / metabolism
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Subcellular Fractions / drug effects
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Subcellular Fractions / metabolism
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Subcellular Fractions / radiation effects
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Xanthophylls / chemistry
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Xanthophylls / metabolism*
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Zeaxanthins
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beta Carotene / analogs & derivatives*
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beta Carotene / chemistry
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beta Carotene / isolation & purification
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beta Carotene / metabolism
Substances
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Cryptoxanthins
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DNA, Complementary
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Ethylenes
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Recombinant Fusion Proteins
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Xanthophylls
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Zeaxanthins
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citraurin
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beta Carotene
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Green Fluorescent Proteins
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Carotenoids
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ethylene
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Dioxygenases
Associated data
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GENBANK/AB114648
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GENBANK/AB114649
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GENBANK/AB114650
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GENBANK/AB114651
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GENBANK/AB114653
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GENBANK/AB114654
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GENBANK/AB114655
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GENBANK/AB219164
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GENBANK/AB219169
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GENBANK/AB219174
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GENBANK/AB781688
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GENBANK/AB781691