title: Genetic mapping and characterization of the globe artichoke (+)-germacrene A synthase gene, encoding the first dedicated enzyme for biosynthesis of the bitter sesquiterpene lactone cynaropicrin.
abstract: Globe artichoke (Cynara cardunculus var. scolymus L., Asteraceae) is a perennial crop traditionally consumed as a vegetable in the Mediterranean countries and rich in nutraceutically and pharmaceutically active compounds, including phenolic and terpenoid compounds. Its bitter taste is caused by its high content of sesquiterpene lactones (STLs), such as cynaropicrin. The biosynthetic pathway responsible for STL biosynthesis in globe artichoke is unknown, but likely proceeds through germacrene A, as has been shown for other Asteraceae species. Here, we investigated the accumulation of cynaropicrin in different tissues of globe artichoke, and compared it to accumulation of phenolic compounds. Cynaropicrin concentration was highest in old leaves. A putative germacrene A synthase (GAS) gene was identified in a set of ~19,000 globe artichoke unigenes. When heterologously expressed in Escherichia coli, the putative globe artichoke GAS converted farnesyl diphosphate (FPP) into (+)-germacrene A. Among various tissues assayed, the level of globe artichoke GAS expression was highest in mature (six week old) leaves. A sequence polymorphism within a mapping population parent allowed the corresponding GAS gene to be positioned on a genetic map. This study reports the isolation, expression and mapping of a key gene involved in STL biosynthesis in C. cardunculus. This is a good basis for further investigation of this pathway.
authors.affiliation: DIVAPRA, Plant Genetics and Breeding, University of Torino, via L. da Vinci 44, 10095 Grugliasco (TO), Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Menin
authors.forename: Cinzia
authors.initials: C
authors.lastname: Comino
authors.forename: Ezio
authors.initials: E
authors.lastname: Portis
authors.forename: Andrea
authors.initials: A
authors.lastname: Moglia
authors.forename: Katarina
authors.initials: K
authors.lastname: Cankar
authors.forename: Harro J
authors.initials: HJ
authors.lastname: Bouwmeester
authors.forename: Sergio
authors.initials: S
authors.lastname: Lanteri
authors.forename: Jules
authors.initials: J
authors.lastname: Beekwilder
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics* / Q000378:metabolism; D053898:Biosynthetic Pathways / Q000235:genetics*; D002853:Chromatography, Liquid; D002874:Chromosome Mapping; D031943:Cynara scolymus / Q000201:enzymology* / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D004926:Escherichia coli / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics*; D008040:Genetic Linkage; D007783:Lactones / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000235:genetics; D010636:Phenols / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D012717:Sesquiterpenes / Q000737:chemistry / Q000378:metabolism*; D013649:Taste / Q000235:genetics
chemical_list: D018076:DNA, Complementary; D007783:Lactones; D010636:Phenols; D010940:Plant Proteins; D012717:Sesquiterpenes; D019883:Alkyl and Aryl Transferases; C075687:cynaropicrin