Metabolic responses of Thellungiella halophila/salsuginea to biotic and abiotic stresses: metabolite profiles and quantitative analyses.

The metabolite profiles of the model crucifer Thellungiella salsuginea (salt cress) ecotype Shandong subjected to various biotic and abiotic stresses were analyzed using HPLC-DAD-ESI-MS. Two different cruciferous microbial pathogens, Albugo candida, a biotrophic oomycete, and Leptosphaeria maculans, a necrotrophic fungus, elicited formation of the phytoalexins wasalexins A and B without causing visual damage on inoculated leaves. Analyses of non-polar and polar metabolites led to elucidation of the chemical structures of five metabolites: 4'-O-(E)-sinapoyl-7-methoxyisovitexin-2''-O-beta-D-glucopyranoside, 4'-O-(E)-sinapoylisovitexin-2''-O-beta-D-glucopyranoside, 4-O-beta-D-glucopyranosyl-7-hydroxymatairesinol, 5'-O-beta-D-glucopyranosyldihydroneoascorbigen and 3-O-beta-D-glucopyranosylthiane. 3-O-beta-D-glucopyranosylthiane, an unique metabolite for which we suggest the name glucosalsuginin, is proposed to derive from the glucosinolate glucoberteroin. In addition, the identification of a broad range of polar metabolites identical to those of other crucifers was carried out. Quantification of several metabolites over a period of eight days showed that concentrations of the polar phytoanticipin 4-methoxyglucobrassicin increased substantially in leaves irradiated with UV light (lambda(max) 254 nm) relative to control leaves, but not in leaves subjected to other stresses.