title: Studies on the biosynthesis and metabolism of the phytoalexin lubimin and related compounds in Datura stramonium L.
abstract: Arachidonic acid, cellulase, CuSO4, a sonicate of Phytophthora infestans mycelium and a spore suspension of Penicillium chrysogenum all elicited the formation of the sesquiterpenoid phytoalexins lubimin, 3-hydroxylubimin and rishitin in fruit cavities of Datura stramonium. 3-Hydroxylubimin was the predominant phytoalexin formed after treatment of the fruits with arachidonic acid, cellulase and the P. infestans preparation. Copper sulphate was a potent elicitor of lubimin but not 3-hydroxylubimin. The fungus P. chrysogenum metabolized lubimin and 3-hydroxylubimin to 15-dihydrolubimin and 3-hydroxy-15-dihydrolubimin respectively, both in fruit cavities inoculated with spores of this fungus and in pure culture. The 15-dihydrolubimin formed in the fruits by the fungus was further metabolized (by the fruits) to both isolubimin and 3-hydroxy-15-dihydrolubimin. The precursor-product relationships between all of the subject compounds was investigated by feeding experiments with (3)H-labelled compounds. 2-Dehydro-[15-(3)H1]lubimin was rapidly and efficiently incorporated into lubimin and may be the direct precursor of lubimin in planta. 3-Hydroxy[2-(3)H1]lubimin was incorporated into the nor-eudesmane rishitin but 10-epi-3-hydroxy[2-(3)H1]lubimin was not. An updated scheme for the biosynthesis and metabolism of lubimin and related compounds in infected tissues of solanaceous plants is presented.
authors.affiliation: Department of Applied Biology, School of Life Sciences, University of Hull, HU6 7RX, Hull, UK.
authors.forename: I M
authors.initials: IM
authors.lastname: Whitehead
authors.forename: A L
authors.initials: AL
authors.lastname: Atkinson
authors.forename: D R
authors.initials: DR
authors.lastname: Threlfall