title: Molecular evolution of fern squalene cyclases.
abstract: Triterpenes, a diverse group of natural products comprising six isoprene units, are distributed across various organisms from bacteria to higher plants. Ferns are sporophytes that produce triterpenes and are lower on the evolutionary scale than higher plants. Among ferns that produce triterpenes analogous to bacterial hopanoids, Polypodiodes niponica produces migrated dammaranes and oleananes, which are also widely found in higher plants. Because the study of terpene-producing ferns could help us to understand the molecular basis of triterpene biosynthesis, cDNA cloning of squalene cyclases (SCs) from P. niponica was carried out. Two SCs (PNT and PNG) were obtained. The heterologously expressed PNT produces tirucalla-7,21-diene (67% major), and PNG produces germanicene (69%). Phylogenetic analysis revealed that PNT and PNG, which produce higher-plant-type migrated dammaranes and oleananes, are closely related to bacterial-type SCs. Furthermore, analysis of the minor products indicated that fern SCs gained the ability to directly form dammarenyl cations, which are key intermediates in oleanane formation during molecular evolution.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Shinozaki
authors.forename: Masaaki
authors.initials: M
authors.lastname: Shibuya
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Takahata
authors.forename: Kazuo
authors.initials: K
authors.lastname: Masuda
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Ebizuka
mesh_terms: D019143:Evolution, Molecular; D029624:Ferns / Q000737:chemistry / Q000201:enzymology*; D008190:Lyases / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009828:Oleanolic Acid / Q000031:analogs & derivatives / Q000096:biosynthesis; D010802:Phylogeny; D014315:Triterpenes / Q000737:chemistry / Q000378:metabolism
chemical_list: D014315:Triterpenes; C514393:tirucallane; D009828:Oleanolic Acid; D008190:Lyases; C022651:squalene cyclase; C036380:beta-amyrin