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Characterization of a caffeoyl-CoA O-methyltransferase-like enzyme involved in biosynthesis of polymethoxylated flavones in Citrus reticulata

Polymethoxylated flavones (PMFs), which accumulate exclusively in fruit peel of citrus, play important physiological and pharmacological roles but the genetic basis for the methylation of flavonoids has not been fully elucidated in citrus. Here we characterize a caffeoyl-CoA O-methyltransferase-like...

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Autores principales: Liu, Xiaojuan, Zhao, Chenning, Gong, Qin, Wang, Yue, Cao, Jinping, Li, Xian, Grierson, Donald, Sun, Chongde
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7475179/
https://www.ncbi.nlm.nih.gov/pubmed/32182355
http://dx.doi.org/10.1093/jxb/eraa083
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author Liu, Xiaojuan
Zhao, Chenning
Gong, Qin
Wang, Yue
Cao, Jinping
Li, Xian
Grierson, Donald
Sun, Chongde
author_facet Liu, Xiaojuan
Zhao, Chenning
Gong, Qin
Wang, Yue
Cao, Jinping
Li, Xian
Grierson, Donald
Sun, Chongde
author_sort Liu, Xiaojuan
collection PubMed
description Polymethoxylated flavones (PMFs), which accumulate exclusively in fruit peel of citrus, play important physiological and pharmacological roles but the genetic basis for the methylation of flavonoids has not been fully elucidated in citrus. Here we characterize a caffeoyl-CoA O-methyltransferase-like enzyme, designated CrOMT1. The expression pattern of CrOMT1 was highly correlated with the concentration of the three major PMFs in two different citrus fruit tissues during fruit maturation. Exposure of fruit to UV-B radiation sharply increased the level of CrOMT1 transcripts and also led to the accumulation of three PMFs. The potential role of CrOMT1 was studied by testing the catalytic activity of recombinant CrOMT1 with numerous possible substrates in vitro. The enzyme could most efficiently methylate flavones with neighboring hydroxy moieties, with high catalytic efficiencies found with 6-OH- and 8-OH-containing compounds, preferences that correspond precisely with the essential methylation sites involved in the synthesis of the three naturally occurring PMFs in Citrus reticulata. This indicates that CrOMT1 is capable of in vitro methylation reactions required to synthesize PMFs in vivo. Furthermore, transient overexpression of CrOMT1 increased levels of the three major PMFs in fruit, indicating that CrOMT1 is likely to play an essential role in the biosynthesis of PMFs in citrus.
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spelling pubmed-74751792020-09-10 Characterization of a caffeoyl-CoA O-methyltransferase-like enzyme involved in biosynthesis of polymethoxylated flavones in Citrus reticulata Liu, Xiaojuan Zhao, Chenning Gong, Qin Wang, Yue Cao, Jinping Li, Xian Grierson, Donald Sun, Chongde J Exp Bot Research Papers Polymethoxylated flavones (PMFs), which accumulate exclusively in fruit peel of citrus, play important physiological and pharmacological roles but the genetic basis for the methylation of flavonoids has not been fully elucidated in citrus. Here we characterize a caffeoyl-CoA O-methyltransferase-like enzyme, designated CrOMT1. The expression pattern of CrOMT1 was highly correlated with the concentration of the three major PMFs in two different citrus fruit tissues during fruit maturation. Exposure of fruit to UV-B radiation sharply increased the level of CrOMT1 transcripts and also led to the accumulation of three PMFs. The potential role of CrOMT1 was studied by testing the catalytic activity of recombinant CrOMT1 with numerous possible substrates in vitro. The enzyme could most efficiently methylate flavones with neighboring hydroxy moieties, with high catalytic efficiencies found with 6-OH- and 8-OH-containing compounds, preferences that correspond precisely with the essential methylation sites involved in the synthesis of the three naturally occurring PMFs in Citrus reticulata. This indicates that CrOMT1 is capable of in vitro methylation reactions required to synthesize PMFs in vivo. Furthermore, transient overexpression of CrOMT1 increased levels of the three major PMFs in fruit, indicating that CrOMT1 is likely to play an essential role in the biosynthesis of PMFs in citrus. Oxford University Press 2020-05-30 2020-03-17 /pmc/articles/PMC7475179/ /pubmed/32182355 http://dx.doi.org/10.1093/jxb/eraa083 Text en © The Author(s) 2020. Published by Oxford University Press on behalf of the Society for Experimental Biology. http://creativecommons.org/licenses/by/4.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Papers
Liu, Xiaojuan
Zhao, Chenning
Gong, Qin
Wang, Yue
Cao, Jinping
Li, Xian
Grierson, Donald
Sun, Chongde
Characterization of a caffeoyl-CoA O-methyltransferase-like enzyme involved in biosynthesis of polymethoxylated flavones in Citrus reticulata
title Characterization of a caffeoyl-CoA O-methyltransferase-like enzyme involved in biosynthesis of polymethoxylated flavones in Citrus reticulata
title_full Characterization of a caffeoyl-CoA O-methyltransferase-like enzyme involved in biosynthesis of polymethoxylated flavones in Citrus reticulata
title_fullStr Characterization of a caffeoyl-CoA O-methyltransferase-like enzyme involved in biosynthesis of polymethoxylated flavones in Citrus reticulata
title_full_unstemmed Characterization of a caffeoyl-CoA O-methyltransferase-like enzyme involved in biosynthesis of polymethoxylated flavones in Citrus reticulata
title_short Characterization of a caffeoyl-CoA O-methyltransferase-like enzyme involved in biosynthesis of polymethoxylated flavones in Citrus reticulata
title_sort characterization of a caffeoyl-coa o-methyltransferase-like enzyme involved in biosynthesis of polymethoxylated flavones in citrus reticulata
topic Research Papers
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7475179/
https://www.ncbi.nlm.nih.gov/pubmed/32182355
http://dx.doi.org/10.1093/jxb/eraa083
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