title: Formation and exudation of non-volatile products of the arabidiol triterpenoid degradation pathway in Arabidopsis roots.
abstract: Triterpenoids produced by plants play important roles in the protection against biotic stress. Roots of Arabidopsis thaliana produce different triterpenoids, which include the tricyclic triterpene diol, arabidiol. In a degradation reaction induced by infection with the oomycete pathogen, Pythium irregulare, arabidiol is cleaved to the 11-carbon volatile homoterpene, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), and the 19-carbon ketone, apo-arabidiol. The arabidiol pathway and its volatile breakdown product DMNT have been implicated in the defense against P. irregulare infection. Here we show that the non-volatile breakdown product apo-arabidiol is further converted to the acetylated derivative α-14-acetyl-apo-arabidiol via a presumed epimerization and subsequent acetylation reaction. α-14-acetyl-apo-arabidiol and the detected intermediates in the derivatization pathway are partially exuded from the root indicating possible defensive activities of these molecules in the rhizosphere. The conversion steps of apo-arabidiol vary among different Arabidopsis accessions and are present in only rudimentary form in the close relative Arabidopsis lyrata, which supports an intra- and inter-specific modularity in triterpenoid metabolism.
authors.affiliation: a Department of Biological Sciences , Virginia Tech , Blacksburg , VA , USA.
authors.forename: Reza
authors.initials: R
authors.lastname: Sohrabi
authors.affiliation: b Division of Medicinal Chemistry and Pharmacognosy, Ohio State University , Columbus , OH , USA.
authors.forename: Tehane
authors.initials: T
authors.lastname: Ali
authors.affiliation: b Division of Medicinal Chemistry and Pharmacognosy, Ohio State University , Columbus , OH , USA.
authors.forename: Liva
authors.initials: L
authors.lastname: Harinantenaina Rakotondraibe
authors.affiliation: a Department of Biological Sciences , Virginia Tech , Blacksburg , VA , USA.
authors.forename: Dorothea
authors.initials: D
authors.lastname: Tholl
mesh_terms: D000475:Alkenes / Q000378:metabolism; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018517:Plant Roots / Q000378:metabolism*; D014315:Triterpenes / Q000378:metabolism*; D055549:Volatile Organic Compounds / Q000378:metabolism; D013729:Terpenes
chemical_list: D000475:Alkenes; D029681:Arabidopsis Proteins; D014315:Triterpenes; D055549:Volatile Organic Compounds; C411254:4,8-dimethyl-1,3,7-nonatriene; D013729:Terpenes; C521218:arabidiol
keywords: Accession variation; Arabidopsis; defense; homoterpene; root; triterpene; volatile