title: Diterpene phytoalexins are biosynthesized in and exuded from the roots of rice seedlings.
abstract: Rice (Oryza sativa L.) produces a variety of diterpene phytoalexins, such as momilactones, phytocassanes, and oryzalexins. Momilactone B was previously identified as an allelopathic substance exuded from the roots of rice. We identified in this present study momilactone A and phytocassanes A-E in extracts of, and exudates from, the roots of rice seedlings. The concentration of each compound was of the same order of magnitude as that of momilactone B. Expression analyses of the diterpene cyclase genes responsible for the biosynthesis of momilactones and phytocassanes suggest that these phytoalexins found in roots are primarily biosynthesized in those roots. None of phytocassanes B-E exhibited allelopathic activity against dicot seedling growth, whereas momilactone A showed much weaker allelopathic activity than momilactone B. The exudation of diterpene phytoalexins from the roots might be part of a system for defense against root-infecting pathogens.
authors.affiliation: Department of Bioresource Engineering, Yamagata University, Tsuruoka, Yamagata 997-8555, Japan. toyomasu@tds1.tr.yamagata-u.ac.jp
authors.forename: Tomonobu
authors.initials: T
authors.lastname: Toyomasu
authors.forename: Takuma
authors.initials: T
authors.lastname: Kagahara
authors.forename: Kazunori
authors.initials: K
authors.lastname: Okada
authors.forename: Jinichiro
authors.initials: J
authors.lastname: Koga
authors.forename: Morifumi
authors.initials: M
authors.lastname: Hasegawa
authors.forename: Wataru
authors.initials: W
authors.lastname: Mitsuhashi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sassa
authors.forename: Hisakazu
authors.initials: H
authors.lastname: Yamane
mesh_terms: D001483:Base Sequence; D001681:Biological Assay; D002851:Chromatography, High Pressure Liquid; D017931:DNA Primers; D004224:Diterpenes / Q000378:metabolism*; D012275:Oryza / Q000201:enzymology / Q000378:metabolism*; D018517:Plant Roots / Q000201:enzymology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012717:Sesquiterpenes; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D013729:Terpenes / Q000378:metabolism*; D000094162:Phytoalexins
chemical_list: D017931:DNA Primers; D004224:Diterpenes; D012717:Sesquiterpenes; D013729:Terpenes; D000094162:Phytoalexins