Impulse Lecture How specialized metabolites mediate interactions between plants and other organisms

Small molecular weight organic compounds are common across the galaxy and transcend all known biological interactions. Plants, in particular, have evolved a remarkable capacity to produce diverse sets of so-called specialized metabolites from a few simple, inorganic precursors. Already in 1977, Rhoades argued that plant specialized metabolites are likely multifunctional, i.e. that they serve multiple purposes. Multifunctionality may render the production of specialized metabolites more cost effective and may explain their abundance and tight spatiotemporal control in plants. Work over the last decades confirms that specialized metabolites often have a broad range of functions, from growth and development to defense [1]. However, our understanding of how this multifunctionality affects the interactions between plants and other organisms, including herbivores and their natural enemies is limited. In my presentation, I will explore the importance of multifunctional plant metabolites for plant-environment interactions by discussing our work on benzoxazinoids, the most abundant specialized metabolites in grasses such as wheat and maize. We find that benzoxazinoids act as direct defenses, within-plant defense signaling molecules, microbiome modulators and siderophores. At the same time, the western corn rootworm, a specialist maize pest and important agricultural pest, exploits benzoxazinoids as foraging cues, protective agents and micronutrient providers. Thus, the multifunctionality of plant specialized metabolites is mirrored in the adaptations of a specialist herbivore, resulting in a tightly interlocked metabolism. These findings have implications for our understanding of the ecology and evolution of plant specialized metabolites, and for their use in agriculture and medicine.