Plants adapt to their environments by diversifying their phenotypes in various ways. This diversification is intimately linked and reflected in plants’ fascinating capacity to evolve novel specialized metabolites. It is now clearly recognized that all modern flowering plant genomes derive from processes set in motion by a history of repeated and episodic auto- or allopolyploidy events and that these polyploidy events act as important drivers of phenotypic innovations. However, the contribution of polyploidy events to the diversification of plant specialized metabolism defenses against insects has only rarely been examined. My group investigates specialized metabolism in the genus Nicotiana for which half of the species are allopolyploids of different ages. Using a multidisciplinary approach combining transcriptomics, metabolomics and chemical ecology methods, we are currently dissecting biochemical pathways leading to “transgressive” defense-related metabolic characters for two well-mapped allopolyploidy cases corresponding to sections Polydiclae and Repandae within the Nicotiana genus.
Species from the section Repandae derive from a single ancient allopolyploidy event, for which N. sylvestris and N. obtusifolia are the closest paternal and maternal genomes, respectively. We discovered that Repandae species are unique among all Nicotiana species with respect to their capacity to synthesize long chain fatty acid-based N-acyl-nornicotine compounds (NANNs) in
their trichomes where they act as superior toxins against insects. During this seminar, I will present results of our recent investigations on the biochemistry, molecular evolution as well as on the defensive mode of action of NANNs. Critical to this research has also been the development of novel computational approaches applied to mass spectrometry metabolomics profiles. During this seminar, I will therefore present a novel “BLAST-like” pipeline (R package MetCirc) through which metabolite trees can be constructed. The use of this bioinformatics method to mine intra- and inter-specific metabolic variations will be exemplified.