In this manuscript, a fast and accurate identification and quantitation by mass spectrometry of indolic glucosinolates and camalexin involved in defense in
Arabidopsis thaliana are described. Two elicitation systems, inoculation with
Botrytis cinerea and treatment with AgNO
3, were used in Col-0 wild-type and mutant genotypes impaired in the biosynthesis of the selected metabolites. Identification of analytes was carried out by nontargeted LC/ESI-QTOF-MS profiling. Confirmation of indolic glucosinolates and camalexin was achieved by their absence in the
cyp79B2/B3 and
pad3 mutants as well as their respective fragmentation upon collision-induced dissociation. Camalexin accumulation was induced only after AgNO
3 treatment, whereas all indolic glucosinolates were constitutively present. Inoculation with
Botrytis did not influence camalexin concentration but caused most aliphatic and indolic glucosinolates contents to decrease. Only the
pen 3.1 mutant showed increased indolic glucosinolate levels after
Botrytis or AgNO
3 treatments. In addition, profiles of secondary metabolite in nontreated Col-0 and mutant plants were analyzed by means of partial least squares coupled to discriminant analysis (PLS-DA), and differences in the basal levels of indolic glucosinolates and tryptophan between
cyp79B2/B3 plants and the rest of genotypes, including Col-0, were found. This probably has to be taken into consideration when comparing stress responses of Col-0 and
cyp79B2/B3. The use of mutants carrying alterations in biosynthetic pathways is proposed as a useful strategy to identify secondary metabolites.
Keywords:
metabolomics; LC/ESI-QTOF-MS; abiotic stress; biotic stress; secondary metabolism; phytoalexins