Document Detail

A novel red clover hydroxycinnamoyl transferase has enzymatic activities consistent with a role in phaselic acid biosynthesis.
MedLine Citation:
PMID:  19525325     Owner:  NLM     Status:  MEDLINE    
Red clover (Trifolium pratense) leaves accumulate several mumol g(-1) fresh weight of phaselic acid [2-O-(caffeoyl)-l-malate]. Postharvest oxidation of such o-diphenols to o-quinones by endogenous polyphenol oxidases prevents breakdown of forage protein during storage. Forage crops like alfalfa (Medicago sativa) lack both polyphenol oxidase and o-diphenols, and breakdown of their protein upon harvest and storage results in economic losses and release of excess nitrogen into the environment. Understanding how red clover synthesizes o-diphenols such as phaselic acid will help in the development of forage crops utilizing this natural system of protein protection. A possible pathway for phaselic acid biosynthesis predicts a hydroxycinnamoyl transferase (HCT) capable of forming caffeoyl and/or p-coumaroyl esters with malate. Genes encoding two distinct HCTs were identified in red clover. HCT1 shares more than 75% amino acid identity with a number of well-characterized shikimate O-HCTs implicated in monolignol biosynthesis. HCT2 shares only 34% amino acid sequence identity with HCT1 and has limited sequence identity to any previously identified HCT. Expression analyses indicate that HCT1 mRNA accumulates to 4-fold higher levels in stems than in leaves, whereas HCT2 mRNA accumulates to 10-fold higher levels in leaves than in stems. Activity assays of HCT1 and HCT2 proteins expressed in Escherichia coli indicate that HCT1 transfers caffeoyl or p-coumaroyl moieties from a coenzyme A-thiolester to shikimate but not malate, whereas HCT2 transfers caffeoyl or p-coumaroyl moieties from a coenzyme A-thiolester to malate but not shikimate. Together, these results indicate that HCT1 is involved in monolignol biosynthesis and HCT2 is a novel transferase likely involved in phaselic acid biosynthesis.
Michaell Sullivan
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2009-06-12
Journal Detail:
Title:  Plant physiology     Volume:  150     ISSN:  0032-0889     ISO Abbreviation:  Plant Physiol.     Publication Date:  2009 Aug 
Date Detail:
Created Date:  2009-08-06     Completed Date:  2009-09-24     Revised Date:  2013-06-02    
Medline Journal Info:
Nlm Unique ID:  0401224     Medline TA:  Plant Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1866-79     Citation Subset:  IM    
Dairy Forage Research Center, Agricultural Research Service, United States Department of Agriculture, Madison, Wisconsin 53706, USA.
Data Bank Information
Bank Name/Acc. No.:
GENBANK/EU861218;  EU861219;  FJ151489
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MeSH Terms
Acyltransferases / chemistry,  genetics,  metabolism*
Amino Acid Sequence
Caffeic Acids / chemistry,  metabolism*
Chromatography, High Pressure Liquid
Cloning, Molecular
Escherichia coli / metabolism
Gene Expression Profiling
Gene Expression Regulation, Plant
Genes, Plant
Hydrogen-Ion Concentration
Malates / chemistry,  metabolism*
Metabolic Networks and Pathways
Molecular Sequence Data
Organ Specificity
Shikimic Acid / metabolism
Trifolium / enzymology*,  genetics
Reg. No./Substance:
0/Caffeic Acids; 0/Malates; 0/phaselic acid; 138-59-0/Shikimic Acid; EC 2.3.-/Acyltransferases

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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