Cloning and characterization of a glucosyltransferase from Crocus sativus stigmas involved in flavonoid glucosylation.
BACKGROUND
Flavonol glucosides constitute the second group of secondary metabolites that accumulate in Crocus sativus stigmas. To date there are no reports of functionally characterized flavonoid glucosyltransferases in C. sativus, despite the importance of these compounds as antioxidant agents. Moreover, their bitter taste makes them excellent candidates for consideration as potential organoleptic agents of saffron spice, the dry stigmas of C. sativus.


RESULTS
Using degenerate primers designed to match the plant secondary product glucosyltransferase (PSPG) box we cloned a full length cDNA encoding CsGT45 from C. sativus stigmas. This protein showed homology with flavonoid glucosyltransferases. In vitro reactions showed that CsGT45 catalyses the transfer of glucose from UDP_glucose to kaempferol and quercetin. Kaempferol is the unique flavonol present in C. sativus stigmas and the levels of its glucosides changed during stigma development, and these changes, are correlated with the expression levels of CsGT45 during these developmental stages.


CONCLUSIONS
Findings presented here suggest that CsGT45 is an active enzyme that plays a role in the formation of flavonoid glucosides in C. sativus.
Moraga
Angela Rubio
AR
Departamento de Ciencia y Tecnología Agroforestal y Genética, ETSIA, Universidad de Castilla-La Mancha, Campus Universitario s/n, Albacete, 02071, Spain. angela.rubio@uclm.es
Mozos
Almudena Trapero
AT
Ahrazem
Oussama
O
Gómez-Gómez
Lourdes
L
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D027622:Crocus / Q000201:enzymology / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D005419:Flavonoids / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D013379:Substrate Specificity
D018076:DNA, Complementary; D018744:DNA, Plant; D005419:Flavonoids; D010940:Plant Proteins; D005964:Glucosyltransferases
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