Metabolic fingerprinting and biosynthesis of sesquiterpene lactones in Smallanthus sonchifolius and Espeletia (Asteraceae): a metabolomic and transcriptomic approach

Abstract

Smallanthus sonchifolius ("yacón") along with the genus Espeletia (Asteraceae, Millerieae) constitute closely related plant groups native to the South American Andes. These species display not only a remarkable genetic similarity, but also a uniform secondary metabolite chemistry, producing the same structural subtype of sesquiterpene lactones (STLs). This class of secondary metabolites possesses a broad range of biological activities and recent data suggest they are biosynthesized due to the adaptive advantages these compounds provide to the producing plants mainly as protective molecules. However, in spite of the potential adaptive roles STLs played in yacon and probably in members from the related genus Espeletia, their biosynthetic origin in recently diversified plant groups remain unexplored. Moreover, the lack of a comprehensive phytochemical characterization of S. sonchifolius across its ontogeny deserves further attention to understand the accumulation and possible adaptive roles of secondary metabolites in this species and others from the same tribe (Millerieae). Therefore, the aim of this research project is to study the metabolic fingerprint and biosynthesis of STLs across the ontogeny of S. sonchifolius and evaluate whether the ability to produce STLs is conserved in Espeletia, or if it is only restricted to a few species. Individuals will be harvested in different developmental stages and the LC-MS-based metabolome and expression of STL biosynthesis related genes will be assessed. Multivariate statistical analyses will be used to find putative changes in the metabolome of S. sonchifolius according to its ontogeny as well as to correlate metabolic data with gene expression studies in an integrated approach involving metabolomic and transcriptomic information. Sequencing of STLs genes in S. sonchifolius and Espeletia will allow finding regions of local similarity with sequences from different species of Asteraceae and phylogenetic reconstructions will employed to explore relationships among Asteraceae species based on genes from the secondary metabolism. (AU)