Cinnamate metabolism in ripening fruit. Characterization of a UDP-glucose:cinnamate glucosyltransferase from strawberry.
Strawberry (Fragaria x ananassa) fruit accumulate (hydroxy)cinnamoyl glucose (Glc) esters, which may serve as the biogenetic precursors of diverse secondary metabolites, such as the flavor constituents methyl cinnamate and ethyl cinnamate. Here, we report on the isolation of a cDNA encoding a UDP-Glc:cinnamate glucosyltransferase (Fragaria x ananassa glucosyltransferase 2 [FaGT2]) from ripe strawberry cv Elsanta that catalyzes the formation of 1-O-acyl-Glc esters of cinnamic acid, benzoic acid, and their derivatives in vitro. Quantitative real-time PCR analysis indicated that FaGT2 transcripts accumulate to high levels during strawberry fruit ripening and to lower levels in flowers. The levels in fruits positively correlated with the in planta concentration of cinnamoyl, p-coumaroyl, and caffeoyl Glc. In the leaf, high amounts of Glc esters were detected, but FaGT2 mRNA was not observed. The expression of FaGT2 is negatively regulated by auxin, induced by oxidative stress, and by hydroxycinnamic acids. Although FaGT2 glucosylates a number of aromatic acids in vitro, quantitative analysis in transgenic lines containing an antisense construct of FaGT2 under the control of the constitutive 35S cauliflower mosaic virus promoter demonstrated that the enzyme is only involved in the formation of cinnamoyl Glc and p-coumaroyl Glc during ripening.
Lunkenbein
Stefan
S
Biomolecular Food Technology, Technical University Munich, Freising, Germany.
Bellido
Mariluz
M
Aharoni
Asaph
A
Salentijn
Elma M J
EM
Kaldenhoff
Ralf
R
Coiner
Heather A
HA
Muñoz-Blanco
Juan
J
Schwab
Wilfried
W
D000595:Amino Acid Sequence; D002934:Cinnamates / Q000737:chemistry / Q000378:metabolism*; D018076:DNA, Complementary / Q000302:isolation & purification; D004952:Esters / Q000737:chemistry / Q000378:metabolism; D031985:Fragaria / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D005638:Fruit / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D007210:Indoleacetic Acids / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D014532:Uridine Diphosphate Glucose / Q000378:metabolism
D002934:Cinnamates; D018076:DNA, Complementary; D004952:Esters; D007210:Indoleacetic Acids; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D005964:Glucosyltransferases; D014532:Uridine Diphosphate Glucose