Diverse Allyl-Glucosinolate catabolites independently influence root growth and development

Plants utilize specialized chemicals to defend against biotic attackers. The generation of these defense chemicals is hypothesized to be costly for the plant and their production might limit growth or fitness. Hence, the plant must calibrate and fine-tune its defense metabolism to optimize the cost-to-benefit ratio for any given environment.

Glucosinolates (GSLs) are sulfur-containing defense metabolites, produced in the Cruciferae family, including the model plant Arabidopsis thaliana. Previous work suggested that specific GSLs may function as signals to provide direct feedback regulation within the plant to calibrate defense and growth. This includes one of the most widespread GSL, Allyl-GSL that has been linked to resistance to numerous pests. Allyl-GSL treatment leads to alterations in plant biomass and endogenous metabolite content.

We found that Allyl-GSL magnifies auxin signaling and responses. This auxin interaction is likely caused not by the Allyl-GSL but instead by three separate catabolic products coming from Allyl-GSL. Excitingly, each compound has a unique regulatory effect on plant development. These unique regulatory effects are reflected by different effects on the auxin signaling cascade or the progression of the cell cycle. The generation of these different catabolic products is mediated by specific enzymes that are controlled in response to diverse environmental stimuli. We propose that this allows the plant to sense the specific processes that are influencing defense metabolism. Thus allowing a specific response that is optimal to any given environment. These findings provide a better understanding of how plants integrate between growth and defense under changing biotic environments.