3.4 | Metabolomic comparison of fenced and unfencedL. benzoin plants
We identified 1,225 metabolite features in all L. benzoin samples
by conducting untargeted metabolomics analysis. PCA did not indicate
clear treatment- or species-based subgrouping of the samples
(Figure 5A ). Hence, we followed a supervised approach (PLS-DA
and HCA) to probe for metabolites that varied among the samples based on
treatment (fence vs no fence) (Figure 5B , D ).
Both methods (PLS-DA and HCA) identified similar significant metabolite
features with similar patterns of accumulation between the fenced and
unfenced plots (Figure 5C, D ).
We used the metabolite features that we identified to obtain putative
prediction of the chemical identities of the 1,225 metabolite features
and the metabolic pathways that they are assigned to using the GSEA
functional analysis tool. Our analysis identified glyoxylate and
dicarboxylate metabolism (P = 0.01) and pentose phosphate pathway (P =
0.02) as significantly overrepresented pathways (Appendix Table
4 ). The glyoxylate and dicarboxylate pathway is not involved in plant
defense directly; however, the possible role of the pentose phosphate
pathway in pathogen defense has been shown in Arabidopsis
thaliana . .