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.

SUBMITTER: Sohrabi R 

PROVIDER: S-EPMC5289522 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature