Metabolomic analysis reveals reliance on secondary plant metabolites to facilitate carnivory in the Cape sundew, Drosera capensis

Abstract Background and aims Secondary metabolites are integral to multiple key plant processes: growth regulation, pollinator attraction, interactions with conspecifics, competitors and symbionts, yet their role in plant adaptation remains an underexplored area of research. Carnivorous plants use secondary metabolites to acquire nutrients from prey, but the extent of the role of secondary metabolites in plant carnivory is not known. We aimed to determine the extent of the role of secondary metabolites in facilitating carnivory of the Cape sundew, Drosera capensis.
Methods We conducted metabolomic analysis of 72 plants in a time-series experiment before and after simulated prey capture. We used UHPLC-MS/MS and retention time index to identify compounds in the leaf trap tissue which changed up to 72 hrs following simulated prey capture. We identified associated metabolic pathways, and cross-compared these compounds to metabolites previously known to be involved in carnivorous plants across taxa.
Key results For the first time in a carnivorous plant, we have profiled the whole-leaf metabolome response to prey capture. Reliance on secondary plant metabolites was higher than previously thought–2383 out of 3257 compounds in fed leaves had statistically significant concentration changes in comparison to unfed controls. Of these, ~34 compounds are also associated with carnivory in other species; 11 are unique to Nepenthales. At least 20 compounds had 10-fold changes in concentration, 12 of which had 30-fold changes and are typically associated with defence or attraction in non-carnivorous plants.
Conclusions Secondary plant metabolites are utilised in plant carnivory to an extent greater than previously thought–we found a whole metabolome response to prey capture. Plant carnivory, at the metabolic level, likely evolved from at least two distinct functions–attraction and defence. Findings of this study support the hypothesis that secondary metabolites play an important role in plant diversification and adaptation to new environments.