title: Divergent evolution of oxidosqualene cyclases in plants.
abstract: Triterpenes are one of the largest classes of plant metabolites and have important functions. A diverse array of triterpenoid skeletons are synthesized via the isoprenoid pathway by enzymatic cyclization of 2,3-oxidosqualene. The genomes of the lower plants Chlamydomonas reinhardtii and moss (Physcomitrella patens) contain just one oxidosqualene cyclase (OSC) gene (for sterol biosynthesis), whereas the genomes of higher plants contain nine to 16 OSC genes. Here we carry out functional analysis of rice OSCs and rigorous phylogenetic analysis of 96 OSCs from higher plants, including Arabidopsis thaliana, Oryza sativa, Sorghum bicolor and Brachypodium distachyon. The functional analysis identified an amino acid sequence for isoarborinol synthase (OsIAS) (encoded by Os11g35710/OsOSC11) in rice. Our phylogenetic analysis suggests that expansion of OSC members in higher plants has occurred mainly through tandem duplication followed by positive selection and diversifying evolution, and consolidated the previous suggestion that dicot triterpene synthases have been derived from an ancestral lanosterol synthase instead of directly from their cycloartenol synthases. The phylogenetic trees are consistent with the reaction mechanisms of the protosteryl and dammarenyl cations which parent a wide variety of triterpene skeletal types, allowing us to predict the functions of the uncharacterized OSCs.
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Fragrant Hill, Beijing 100093, China.
authors.forename: Zheyong
authors.initials: Z
authors.lastname: Xue
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Fragrant Hill, Beijing 100093, China.
authors.forename: Lixin
authors.initials: L
authors.lastname: Duan
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Fragrant Hill, Beijing 100093, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Fragrant Hill, Beijing 100093, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Fragrant Hill, Beijing 100093, China.
authors.forename: Song
authors.initials: S
authors.lastname: Ge
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: Paul
authors.initials: P
authors.lastname: ÓMáille
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
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Fragrant Hill, Beijing 100093, China.
authors.forename: Xiaoquan
authors.initials: X
authors.lastname: Qi
mesh_terms: D017360:Arabidopsis / Q000201:enzymology; D058431:Brachypodium / Q000201:enzymology; D003500:Cyclization; D019143:Evolution, Molecular; D020440:Gene Duplication; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D019751:Intramolecular Transferases / Q000235:genetics* / Q000378:metabolism*; D005810:Multigene Family; D012275:Oryza / Q000201:enzymology / Q000235:genetics; D010802:Phylogeny; D045868:Sorghum / Q000201:enzymology; D013185:Squalene / Q000031:analogs & derivatives / Q000378:metabolism; D014315:Triterpenes / Q000737:chemistry / Q000378:metabolism
chemical_list: C002821:2,3-oxidosqualene; D014315:Triterpenes; C028769:3-hydroxydiploptene; D013185:Squalene; D019751:Intramolecular Transferases; C559557:parkeol synthase, Oryza sativa; C021924:lanosterol synthase