Postdoctoral Research Associate Michigan State University
Plant specialized metabolites are used by humans as medicines, food additives and natural insecticides. Solanaceae family plants synthesize herbivory defensive acylated sugars in the tip cells of glandular trichomes. Acylsugars show striking structural variety within Solanaceae family. One example is that – while acylsucroses are found in many species across the family – acylglucoses were detected in the phylogenetically distinct new world tomato Solanum pennellii and old world black nightshade Solanum nigrum. We describe use of NMR spectroscopy, RNA-seq, and in vitro pathway reconstruction to characterize a S. nigrum acylglucose biosynthetic pathway. The pathway includes a trichome-expressed invertase (acylsucrose fructofuranosidase or ASFF) and two acyltransferases. Thus, the pathway is superficially similar to our recently published work demonstrating evolution of S. pennellii acylglucose biosynthesis, where SpASFF1 enzyme converts triacylsucrose to triacylglucose. However, our results reveal that the S. nigrum pathway evolved independently, with recruitment of a neofunctionalized SnASFF from a distinct lineage of the invertase gene phylogeny. This work highlights how the repeated emergence of novel enzymes from primary metabolism shaped diversification of specialized metabolites in plants. The newly discovered pathway and its unconventional players strengthen our toolset to engineer plants with metabolic novelties, and aid in our aim to establish a systematic approach to decipher phenotypical advantages of different types of acylsugars.
Coauthors: Thilani Anthony – Michigan State University;Rachel Arking – Michigan State University;Elizabeth Christensen – Michigan State University;Robert Last – Michigan State University