3.5 | Metabolomic comparison of fenced and unfencedR. multiflora plants
We conducted untargeted metabolomics analysis on all R.
multiflora samples and identified 1,350 metabolite features. Even
though the samples tend to separate from each other on the PCA plot
based on treatment (fence vs no fence), the PCA did not group the
samples into distinct clusters (Figure 6A ). To inspect the
treatment-based differences in the metabolite profile of the plants, we
conducted PLS-DA (Figure 6B ) and identified the top 15 features
that varied significantly across the treatments (Figure 6C ). We
followed this analysis with HCA to obtain a filtered set of 25
metabolites that consistently and significantly varied between the fence
and no fence samples. The heatmap generated from the HCA analysis
indicates that the top 25 metabolites clearly differentiate the fence
and no fence samples (Figure 6D ). The GSEA tool in
Metaboanalyst was used to identify some putative metabolic pathways that
the metabolomic features are associated with, including the pentose
phosphate pathway (P = 0.04) and carbon fixation in photosynthetic
organisms (P = 0.04) (Appendix Table 5 ); though carbon
fixation is not directly related with plant defense, the pentose
phosphate pathway is implicated with stress responses in plants .