UC Davis

Arachidonic acid (AA) is an oomycete-derived microbe-associated molecular pattern (MAMP) capable of eliciting robust defense responses and inducing resistance in plants. Similarly, Ascophylum nodosum extract (ANE) from the brown seaweed A. nodosum, a plant biostimulant that contains AA, can also prime plants for defense against pathogen challenges. A previous parallel study comparing the transcriptomes of AA- and ANE-root-treated tomatoes demonstrated significant overlap in transcriptional profiles, a shared induced resistance phenotype, and changes in the 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 tomatoes. Our study demonstrated AA and ANEs capacity to locally and systemically alter the metabolome of tomatoes 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 tomatoes induced by treatment with a fatty acid MAMP and a seaweed-derived plant biostimulant with implications for induced resistance and crop improvement.