Arabidopsides as Signatory Biomarkers of the Arabidopsis thaliana Response to Lipopolysaccharides—Metabolomics Insights

The in vivo production of specialized metabolites in response to external stimuli can be genus- and species-specific and involves the activation of linked metabolic pathways. In Arabidopsis thaliana, oxidized galactolipids containing oxo-phytodienoic acid (OPDA), known as Arabidopsides, are functionally linked to multiple plant stress events. It has been proposed that Arabidopsides may fulfill the function of storage metabolites of the esterified OPDA moieties to enable early induction and sustained activation of defense-related pathways linked to jasmonic acid (JA). Differential profiles or signatures of the accumulated Arabidopsides result from early utilization or further conjugation and interconversion reactions. Arabidopsides were previously annotated as discriminant metabolites in untargeted metabolomics datasets of extracts of A. thaliana leaves infiltrated with lipopolysaccharide (LPS) chemotypes from two pathogens, as well as a non-pathogen. This elicitation response suggests a functional relationship between LPS as a ‘non-self’ defense-triggering stimulus and the synthesis and accumulation of the annotated Arabidopsides. A defense response or priming effect via OPDA release and subsequent JA actions would be particularly advantageous, as it would equip susceptible plants with a more responsive and effective defensive metabolome through metabolic reprogramming. Arabidopsides may thus be regarded as signature metabolites in underscoring the dynamic and condition-dependent nature of microbe-mediated metabolic reprogramming that involves perception of bacterial LPSs from potential pathogens or beneficial rhizobacteria.