The plant kingdom has been estimated to synthesize hundreds of thousands of bioactive secondary metabolites, yet the genes and pathways responsible for biosynthesis of most metabolites remain unclear. Secretary glandular trichomes (SGTs) are plant epidermal cells that function as prolific chemical factories that synthesize a diverse collection of specialized metabolites. Among these are structurally diverse non-volatile acylsugars that exhibit insecticidal properties. Some relatives of wild tomato accumulate large numbers of isomeric acylsugars that differ in acylchain lengths, branching points, and positions of substitution. The discovery of the genes responsible for specialized metabolite biosynthesis can open doors to metabolic engineering for their controlled production in plants and other species. However, central to the gene discovery process is the development of rapid and sensitive analytical strategies to identify and profile these specialized metabolites.Numerous novel acylsugars have been profiled in 80 different accessions of the wild tomato relative Solanum habrochaites, but details regarding structure are limited. Perhaps most challenging is the similar MS/MS product ion spectra generated for acylsugar isomers in both positive and negative ion modes. To overcome these barriers, a combination of tools including ultra high performance LC-TOF MS with multiplexed collision induced dissociation (CID) and LC-MS/MS were employed using multiple collision energies to uncover differences in functional group elimination thresholds. Further structure support was derived from chemical hydrolysis, 1D and 2D NMR spectra. The CID spectra provided evidence for substitution positions, and facilitate discrimination of isomeric specialized metabolites.

Profiling secondary metabolome isomeric diversity of glandular trichomes of tomato and its wild relatives using liquid chromatography/mass spectrometry

243rd National Meeting (2012)

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