title: Biosynthesis of the leucine derived α-, β- and γ-hydroxynitrile glucosides in barley (Hordeum vulgare L.).
abstract: Barley (Hordeum vulgare L.) produces five leucine-derived hydroxynitrile glucosides (HNGs), of which only epiheterodendrin is a cyanogenic glucoside. The four non-cyanogenic HNGs are the β-HNG epidermin and the γ-HNGs osmaronin, dihydroosmaronin and sutherlandin. By analyzing 247 spring barley lines including landraces and old and modern cultivars, we demonstrated that the HNG level varies notably between lines whereas the overall ratio between the compounds is constant. Based on sequence similarity to the sorghum (Sorghum bicolor) genes involved in dhurrin biosynthesis, we identified a gene cluster on barley chromosome 1 putatively harboring genes that encode enzymes in HNG biosynthesis. Candidate genes were functionally characterized by transient expression in Nicotiana benthamiana. Five multifunctional P450s, including two CYP79 family enzymes and three CYP71 family enzymes, and a single UDP-glucosyltransferase were found to catalyze the reactions required for biosynthesis of all five barley HNGs. Two of the CYP71 enzymes needed to be co-expressed for the last hydroxylation step in sutherlandin synthesis to proceed. This observation, together with the constant ratio between the different HNGs, suggested that HNG synthesis in barley is organized within a single multi-enzyme complex.
authors.affiliation: Department of Plant and Environmental Sciences, Plant Biochemistry Laboratory, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Copenhagen, Denmark.|VILLUM Research Center for Plant Plasticity, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Eva
authors.initials: E
authors.lastname: Knoch
authors.affiliation: Department of Plant and Environmental Sciences, Plant Biochemistry Laboratory, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Copenhagen, Denmark.|VILLUM Research Center for Plant Plasticity, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Mohammed Saddik
authors.initials: MS
authors.lastname: Motawie
authors.affiliation: Department of Plant and Environmental Sciences, Plant Biochemistry Laboratory, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Copenhagen, Denmark.|VILLUM Research Center for Plant Plasticity, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Carl Erik
authors.initials: CE
authors.lastname: Olsen
authors.affiliation: Department of Plant and Environmental Sciences, Plant Biochemistry Laboratory, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Copenhagen, Denmark.|VILLUM Research Center for Plant Plasticity, University of Copenhagen, Copenhagen, Denmark.|Carlsberg Laboratory, Gamle Carlsberg Vej 10, Copenhagen V, 1799, Denmark.
authors.forename: Birger Lindberg
authors.initials: BL
authors.lastname: Møller
authors.affiliation: Department of Plant and Environmental Sciences, Plant Biochemistry Laboratory, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Copenhagen, Denmark.|VILLUM Research Center for Plant Plasticity, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Michael Foged
authors.initials: MF
authors.lastname: Lyngkjaer
mesh_terms: D005960:Glucosides / Q000096:biosynthesis* / Q000737:chemistry*; D001467:Hordeum / Q000235:genetics / Q000378:metabolism*; D007930:Leucine / Q000737:chemistry* / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D005960:Glucosides; D010940:Plant Proteins; D007930:Leucine
keywords: CYP71C113; CYP71L1; CYP79A12; CYP79A8; Hordeum vulgare; UGT85F22; hydroxynitrile glucoside content; hydroxynitrile glucoside ratios; multifunctional P450s; oxime toxicity