title: Investigation of the potential for triterpene synthesis in rice through genome mining and metabolic engineering.
abstract: The first committed step in sterol biosynthesis in plants involves the cyclization of 2,3-oxidosqualene by the oxidosqualene cyclase (OSC) enzyme cycloartenol synthase. 2,3-Oxidosqualene is also a precursor for triterpene synthesis. Antimicrobial triterpenes are common in dicots, but seldom found in monocots, with the notable exception of oat. Here, through genome mining and metabolic engineering, we investigate the potential for triterpene synthesis in rice. The first two steps in the oat triterpene pathway are catalysed by a divergent OSC (AsbAS1) and a cytochrome P450 (CYP51). The genes for these enzymes form part of a metabolic gene cluster. To investigate the origins of triterpene synthesis in monocots, we analysed systematically the OSC and CYP51 gene families in rice. We also engineered rice for elevated triterpene content. We discovered a total of 12 OSC and 12 CYP51 genes in rice and uncovered key events in the evolution of triterpene synthesis. We further showed that the expression of AsbAS1 in rice leads to the accumulation of the simple triterpene, β-amyrin. These findings provide new insights into the evolution of triterpene synthesis in monocots and open up opportunities for metabolic engineering for disease resistance in rice and other cereals.
authors.affiliation: Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.|Plant Pathology and Genetic Engineering Laboratory, Faculty of Agriculture, Tsushiama-naka 1-1-1, Okayama University, Okayama 700-8530, Japan.
authors.forename: Yoshi-Shige
authors.initials: YS
authors.lastname: Inagaki
authors.affiliation: Department of Computational and Systems Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Graham
authors.initials: G
authors.lastname: Etherington
authors.affiliation: Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Katrin
authors.initials: K
authors.lastname: Geisler
authors.affiliation: Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Ben
authors.initials: B
authors.lastname: Field
authors.affiliation: Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Melissa
authors.initials: M
authors.lastname: Dokarry
authors.affiliation: Plant Pathology and Genetic Engineering Laboratory, Faculty of Agriculture, Tsushiama-naka 1-1-1, Okayama University, Okayama 700-8530, Japan.
authors.forename: Kousuke
authors.initials: K
authors.lastname: Ikeda
authors.affiliation: Plant Pathology and Genetic Engineering Laboratory, Faculty of Agriculture, Tsushiama-naka 1-1-1, Okayama University, Okayama 700-8530, Japan.
authors.forename: Yukako
authors.initials: Y
authors.lastname: Mutsukado
authors.affiliation: Department of Computational and Systems Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Jo
authors.initials: J
authors.lastname: Dicks
authors.affiliation: Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Anne
authors.initials: A
authors.lastname: Osbourn
mesh_terms: D000595:Amino Acid Sequence; D005075:Biological Evolution; D018745:Genome, Plant / Q000235:genetics; D019751:Intramolecular Transferases / Q000235:genetics / Q000378:metabolism; D058977:Molecular Sequence Annotation; D005810:Multigene Family; D009828:Oleanolic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D006109:Poaceae / Q000235:genetics; D016415:Sequence Alignment; D013185:Squalene / Q000031:analogs & derivatives* / Q000378:metabolism; D058886:Sterol 14-Demethylase / Q000235:genetics / Q000378:metabolism; D014315:Triterpenes / Q000378:metabolism*
chemical_list: C002821:2,3-oxidosqualene; D010940:Plant Proteins; D014315:Triterpenes; D009828:Oleanolic Acid; D013185:Squalene; D058886:Sterol 14-Demethylase; D019751:Intramolecular Transferases; C039924:2,3-oxidosqualene-beta-amyrin-cyclase; C021924:lanosterol synthase; C036380:beta-amyrin