Arachidonic acid (AA) is an oomycete-derived MAMP capable of eliciting robust defense responses and inducing resistance in plants. Similarly, extract (ANE) from the brown seaweed Ascophylum nodosum, a plant biostimulant that contains AA, can also prime plants for defense against pathogen challenge. A previous parallel study comparing the transcriptomes of AA and ANE root-treated tomato demonstrated significant overlap in transcriptional profiles, a shared induced resistance phenotype, and changes in accumulation of various defense-related phytohormones. In this work, untargeted metabolomic analysis via liquid chromatography-mass spectrometry was conducted to investigate the local and systemic metabolome-wide remodeling events elicited by AA- and ANE-root treatment in tomato. Our study demonstrated AA and ANE’s capacity to locally and systemically alter the metabolome of tomato with enrichment of chemical classes and accumulation of metabolites associated with defense-related secondary metabolism. AA and ANE root-treated plants showed enrichment of fatty acyl-glycosides and strong modulation of hydroxycinnamic acids and derivatives. Identification of specific metabolites whose accumulation was affected by AA and ANE treatment revealed shared metabolic changes related to ligno-suberin biosynthesis and the synthesis of phenolic compounds. This study highlights the extensive local and systemic metabolic changes in tomato induced by treatment with a fatty acid MAMP and a seaweed-derived plant biostimulant with implications for induced resistance and crop improvement.

Arachidonic acid (AA) is an oomycete derived MAMP capable of eliciting robust defense responses and inducing resistance in plants. Similarly, extract from the brown seaweed Ascophylum nodosum, a plant biostimulant that contains AA, can also prime plants for defense against pathogen challenge. A previous parallel study comparing the transcriptomes of AA and ANE root-treated tomato demonstrated significant overlap in transcriptional profiles, a shared induced resistance phenotype, and changes in accumulation of various defense-related phytohormones. In this work, untargeted metabolomic analysis via LCMS was conducted to investigate the local and systemic metabolome-wide remodeling events elicited by AA- and ANE-root treatment in tomato. Our study demonstrated AA and ANE's capacity to locally and systemically alter the metabolome of tomato with enrichment of chemical classes and accumulation of metabolites associated with defense-related secondary metabolism. AA and ANE root-treated plants showed enrichment of fatty acyl-glycosides and strong modulation of hydroxycinnamic acids and derivatives. Identification of specific metabolites whose accumulation was affected by AA and ANE treatment revealed shared metabolic changes related to ligno-suberin biosynthesis and the synthesis of phenolic compounds. However, AA- and ANE-induced metabolomes are distinct, and do not share the extensive overlap in their induced transcriptomes that we observed in a previous study. This study highlights the extensive local and systemic metabolic changes in tomato induced by treatment with a fatty acid MAMP and a seaweed-derived plant biostimulant with implications for induced resistance and crop improvement.