Molecular regulation and ecological consequences of chemodiversity in Solanum dulcamara

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Solanum dulcamara plants produce a large variety of steroidal glycoalkaloids (SGAs), which may provide resistance to herbivores and pathogens. In the first phase, we focused on two leaf SGA chemotypes: plants with SGAs that are unsaturated at the C5,6 bond (U) and those producing also saturated (S) SGAs. Our aim was to identify additional levels of chemodiversity in these SGA chemotypes as well as to study the ecological consequences. Using LC-qTOF-MS analysis, we found that root metabolic profiles of U and S chemotypes are more similar than those of their leaves. Primary and adventitious roots contain different subsets of SGAs, and, like flowers, also produce oxygenated glycosteroids. Using synthetic steroidal compounds, we are now testing how these small structural differences affect herbivores in bioassays. A common garden experiment was designed with P1, P5 and P7. Manipulating U and S chemotype frequencies revealed that both individual chemotype and plot chemodiversity affected fruit and seed production. These data will be shared with P9 for modelling evolutionary trajectories. Together with P8 we assembled and annotated the genome of one S chemotype. Combined with herbivore and jasmonate induction experiments, we identified genes involved in the regulation, biosynthesis and transport of SGAs as well as terpene synthases. In a second phase, we aim to understand how root chemodiversity influences belowground interactions and how intra-individual chemodiversity is molecularly regulated. We will expand our comparative analyses of leaf, root and flower metabolite profiles by adding field-collected individuals from P3. Using the R-package developed by P10, we will analyse whether roots overall have lower levels of intraspecific chemodiversity than leaves or flowers as in P1, P3 and P5. We propose to synthesise the knowledge gained in a conceptual paper with the other projects in the Research Unit to explore the fundamental question of “how to define an individual chemotype?”. Using a sub-set representing contrasting root metabolite profiles, we will test how root chemodiversity impacts interactions with root herbivores, nematodes and beneficial microbes (with P7). In addition, we will assess how these different belowground interactions will impact leaf metabolite profiles and aboveground herbivores. The plant and herbivore performance data will be shared with P9 for modelling. Finally, with P8 we will use the genomic data generated in the first phase to analyse the molecular regulation of intra-individual variation in SGAs and terpenoids among organs within a plant. We will participate in the COR chemodiversity-plasticity experiment by providing elemental (C, N, P) analyses.