Profiling, isolation and structure elucidation of specialized acylsucrose metabolites accumulating in trichomes of Petunia species
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Acylsugar specialized metabolites function as defenses against insect herbivores, and are the most abundant specialized metabolites produced in Solanaceous trichomes. Metabolite profiling provides the foundation for determining the genetic basis of specialized metabolism and its evolution.
To profile and identify acylsugar specialized metabolites in three Petunia species: P. axillaris, P. integrifolia and P. exserta.
Metabolites were profiled using ultra-high performance liquid chromatography/time-of-flight mass spectrometry (UHPLC/TOF MS). Metabolites were purified using solid phase extraction and HPLC, and structures were established using NMR spectroscopy.
Twenty-eight distinct acylsucrose formulas, representing a sampling of more than 100 different detected chemical forms, were purified from three Petunia species and structures have been proposed based on one- and two-dimensional NMR data. 15 of the 28 purified acylsugars were sucrose pentaesters that possess a malonyl group on the fructose ring. These malonate esters can be readily distinguished from other acylsugars based on distinct masses of pseudomolecular ions and fragment ions generated using multiplexed collision-induced dissociation. Chemical diversity of acylsugars was observed between Petunia species, particularly with respect to the lengths of acyl chains and specific acylation positions.
These findings suggest substrate selectivity of various acyltransferases in Petunia species.
KeywordsNuclear magnetic resonance (NMR) spectroscopy Petunia axillaris Petunia integrifolia Petunia exserta Specialized metabolite profiling Ultra-high performance liquid chromatography/time-of-flight mass spectrometry (UHPLC/TOF MS)
We thank members of the Solanum Trichome project team, notably Drs. Banibrata Ghosh, Swathi Nadakuduti, Zhenzhen Wang, Tony Schilmiller, Jing Ning, and Robert Last for helpful discussion and contributions to this effort. We thank the Michigan State University Mass Spectrometry and Metabolomics Core staff and Dr. Daniel Holmes of the MSU Max T. Rogers NMR Facility.
Research in the Barry and Jones laboratories is funded by National Science Foundation grants IOS-1025636 and IOS-1546617 (R. L. Last, PI). A.D.J. and C.S.B. acknowledge support from the USDA National Institute of Food and Agriculture, Hatch projects MICL02143 and MICL02265. M. E. was supported by the Plant Genomics at Michigan State University Summer Research Experiences for Undergraduates Program (NSF grant DBI-1358474, C. S. Barry, PI).
Compliance with ethical standards
Conflict of interest
Each author declares no conflict of interest with regard to the research presented in this article.
This article does not contain any studies with human participants or with animals performed by any of the authors.
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