An untargeted global metabolomic analysis reveals the biochemical changes underlying basal resistance and priming in Solanum lycopersicum, and identifies 1-methyltryptophan as a metabolite involved in plant responses to Botrytis cinerea and Pseudomonas syringae

Abstract

n this study, we have used untargeted global metabolomic analysis to determine and compare the chemi-cal nature of the metabolites altered during the infection of tomato plants (cv. Ailsa Craig) with Botry-tis cinerea (Bot)orPseudomonas syringae pv. tomato DC3000 (Pst), pathogens that have different invasionmechanisms and lifestyles. We also obtained the metabolome of tomato plants primed using the naturalresistance inducer hexanoic acid and then infected with these pathogens. By contrasting the metabolomicprofiles of infected, primed, and primed + infected plants, we determined not only the processes or compo-nents related directly to plant defense responses, but also inferred the metabolic mechanisms by whichpathogen resistance is primed. The data show that basal resistance and hexanoic acid-induced resistance toBot and Pst are associated with a marked metabolic reprogramming. This includes significant changes inamino acids, sugars and free fatty acids, and in primary and secondary metabolism. Comparison of themetabolic profiles of the infections indicated clear differences, reflecting the fact that the plant’s chemicalresponses are highly adapted to specific attackers. The data also indicate involvement of signaling mole-cules, including pipecolic and azelaic acids, in response to Pst and, interestingly, to Bot. The compound 1-methyltryptophan was shown to be associated with the tomato–Pst and tomato–Bot interactions as well aswith hexanoic acid-induced resistance. Root application of this Trp-derived metabolite also demonstratedits ability to protect tomato plants against both pathogens.