Abstract
While the structures of plant primary metabolic pathways are generally well defined and highly conserved across species, those defining specialized metabolism are less well characterized and more highly variable across species. In this study, we investigated polyphenolic metabolism in the lycopersicum complex by characterizing the underlying biosynthetic and decorative reactions that constitute the metabolic network of polyphenols across eight different species of tomato. For this purpose, GC–MS- and LC–MS-based metabolomics of different tissues of Solanum lycopersicum and wild tomato species were carried out, in concert with the evaluation of cross-hybridized microarray data for MapMan-based transcriptomic analysis, and publicly available RNA-sequencing data for annotation of biosynthetic genes. The combined data were used to compile species-specific metabolic networks of polyphenolic metabolism, allowing the establishment of an entire pan-species biosynthetic framework as well as annotation of the functions of decoration enzymes involved in the formation of metabolic diversity of the flavonoid pathway. The combined results are discussed in the context of the current understanding of tomato flavonol biosynthesis as well as a global view of metabolic shifts during fruit ripening. Our results provide an example as to how large-scale biology approaches can be used for the definition and refinement of large specialized metabolism pathways.
Highlights
IntroductionGiven that the nutritional and calorific value of crops are, by and large, determined by their chemical composition, identifying the genetic bases that control the accumulation of metabolites is of fundamental importance for attempts at crop improvement
As a first step toward understanding the entire framework of tomato polyphenolic metabolism, we surveyed tomato polyphenols characterized by nuclear magnetic resonance studies or confirmed by co-elution with standard compounds in liquid chromatography–mass spectrometry (LC–MS) (Figure 1A)
Tomato species represent an excellent system for unraveling the diversity in this pathway, considering that the tomato clade includes a set of species with a wealth of genomic and metabolomic resources available, which diverged recently but show considerable diversity at the morphological and physiological levels (Peralta et al, 2008)
Summary
Given that the nutritional and calorific value of crops are, by and large, determined by their chemical composition, identifying the genetic bases that control the accumulation of metabolites is of fundamental importance for attempts at crop improvement. For this reason, many studies have been carried out utilizing natural variation to study both metabolite accumulation and metabolic regulation (Kliebenstein, 2009; Sulpice et al, 2010; Chan et al, 2011; Wen et al, 2014; Ishihara et al, 2016; Tohge et al, 2016; Perez de Souza et al, 2019)
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