Predator-induced plastic changes in metabolomic profiles
The mechanisms underlying the widespread trait responses to predation
risk are still poorly understood (Mitchell et al. 2017). Our
results clearly showed predation risk changed the metabolome of the preyD. magna . One key finding was that the amino
acid
metabolism (i.e.
valine,
leucine and isoleucine biosynthesis, and metabolism of
beta-alanine,
arginine and proline, tryptophan and phenylalanine) was strongly
affected across subpopulations under predation risk. The pronounced
changes in amino acid metabolism indicates D. magna deals with
predation risk by altering protein utilization. This complements a
proteomic study showing that exposure to predator kairomones enhanced
the biosynthetic activity of proteins in D.
magna , particularly
glyceraldehyde-3-phosphate dehydrogenase (GAPDH) that is necessary for
biosynthesis of amino acids (Otte et al. 2014). Related to this,
exposure to fish kairomones has been shown to upregulate genes involved
in protein folding in D. magna (Schwarzenberger et al.2009). In addition, the predator-induced change in amino acid metabolism
may partly reflect changes in stress protein levels as documented for
the study species (Pauwels et al. 2005). Besides playing a
central role in the metabolic turnover of proteins, amino acids are also
used extensively in energy metabolism (Viant et al. 2003). The
proteomic study indeed showed evidence for enhanced energy demand ofD. magna when under predation risk (Otte et al. 2014).