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Plant J. 2016 Dec;88(5):775-793. doi: 10.1111/tpj.13295. Epub 2016 Sep 27.

Integrating metabolomics and transcriptomics data to discover a biocatalyst that can generate the amine precursors for alkamide biosynthesis.

Author information

1
The Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, USA.
2
Center for Metabolic Biology, Iowa State University, Ames, IA, USA.
3
Engineering Research Center for Biorenewable Chemicals, Iowa State University, Ames, IA, USA.
4
Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, 402 N. Blackford Street, Indianapolis, IN, USA.
5
W.M. Keck Metabolomics Research Laboratory, Iowa State University, Ames, IA, USA.
6
Department of Genetics, Development & Cell Biology-LAS, Iowa State University, Ames, IA, USA.
7
Department of Plant Biology, Michigan State University, East Lansing, MI, 48824, USA.

Abstract

The Echinacea genus is exemplary of over 30 plant families that produce a set of bioactive amides, called alkamides. The Echinacea alkamides may be assembled from two distinct moieties, a branched-chain amine that is acylated with a novel polyunsaturated fatty acid. In this study we identified the potential enzymological source of the amine moiety as a pyridoxal phosphate-dependent decarboxylating enzyme that uses branched-chain amino acids as substrate. This identification was based on a correlative analysis of the transcriptomes and metabolomes of 36 different E. purpurea tissues and organs, which expressed distinct alkamide profiles. Although no correlation was found between the accumulation patterns of the alkamides and their putative metabolic precursors (i.e., fatty acids and branched-chain amino acids), isotope labeling analyses supported the transformation of valine and isoleucine to isobutylamine and 2-methylbutylamine as reactions of alkamide biosynthesis. Sequence homology identified the pyridoxal phosphate-dependent decarboxylase-like proteins in the translated proteome of E. purpurea. These sequences were prioritized for direct characterization by correlating their transcript levels with alkamide accumulation patterns in different organs and tissues, and this multi-pronged approach led to the identification and characterization of a branched-chain amino acid decarboxylase, which would appear to be responsible for generating the amine moieties of naturally occurring alkamides.

KEYWORDS:

Echinacea purpurea ; alkamides; amines; fatty acids; metabolomics; specialized metabolism; transcriptomics

PMID:
27497272
PMCID:
PMC5195896
DOI:
10.1111/tpj.13295
[Indexed for MEDLINE]
Free PMC Article

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