title: Characterization of CYP71Z18 indicates a role in maize zealexin biosynthesis.
abstract: Maize (Zea mays) produces zealexins as phytoalexins, with the inducible production of these antibiotics providing biochemical protection against fungal infection. However, the biosynthesis of these sesquiterpenoids has remained unclear. In particular, it is unclear how the olefinic precursor, (S)-β-macrocarpene produced by the characterized maize sesquiterpene synthases TPS6/11, is further elaborated to form the bioactive zealexins. The first step is likely to be conversion of carbon-15 (C15) from a methyl group to a carboxylic acid by a cytochrome P450 mono-oxygenase (CYP). In this study, CYP71Z18, whose transcription is strongly induced by fungal infection, was found to catalyze oxidation of C15 in (S)-β-macrocarpene, forming zealexin A1. The inducible transcription of CYP71Z18 matches that observed for TPS6/11 and the accumulation of zealexins, which is consistent with a role for CYP71Z18 in sesquiterpenoid phytoalexin production. This completes identification of zealexin A1 biosynthesis, and represents the initial CYP identified for the production of maize terpenoid phytoalexins.
authors.affiliation: College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China. Electronic address: hongjiemao1@163.com.
authors.forename: Hongjie
authors.initials: H
authors.lastname: Mao
authors.affiliation: College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China. Electronic address: jiangliu@sicau.edu.cn.
authors.forename: Jiang
authors.initials: J
authors.lastname: Liu
authors.affiliation: College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China. Electronic address: rfchang@sina.com.
authors.forename: Fei
authors.initials: F
authors.lastname: Ren
authors.affiliation: Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA. Electronic address: rjpeters@iastate.edu.
authors.forename: Reuben J
authors.initials: RJ
authors.lastname: Peters
authors.affiliation: College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China; Institute of Ecological Agriculture, Sichuan Agricultural University, Chengdu 611130, China. Electronic address: qwang@sicau.edu.cn.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Wang
mesh_terms: D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism / Q000502:physiology*; D015394:Molecular Structure; D012717:Sesquiterpenes / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D013729:Terpenes / Q000378:metabolism; D003313:Zea mays / Q000737:chemistry / Q000502:physiology*; D000094162:Phytoalexins
chemical_list: D012717:Sesquiterpenes; D013729:Terpenes; C531190:beta-macrocarpene; D003577:Cytochrome P-450 Enzyme System; D000094162:Phytoalexins
keywords: Biosynthesis; Maize; P450; Phytoalexin; Poaceae; Terpenoid; Zea mays; Zealexin