The ectomycorrhizal fungus Tricholoma matsutake biosynthesizes benzoic acid and benzaldehyde independently

Abstract Metabolism of benzoic acids and benzaldehydes are crucial to produce hormones, defense compounds and attractants for pollinators in plants. Tricholoma matsutake contains benzoic acid and benzaldehyde, but their roles have not been fully studied. First we conducted tracer experiments to gain insight into benzoic acid and benzaldehyde biosynthesis in T. matsutake . 13 C and 2 H were incorporated into benzoic acid from uniformly 13 C- and 2 H- labelled l -phenylalanine and ( E )-cinnamate 1 d after supplementation of the precursors without any substitution of 13 C and 2 H. In contrast, no 13 C and 2 H were incorporated into benzaldehyde from these precursors 10 d after the supplementation. The results indicate that T. matsutake has a metabolic pathway to biosynthesize benzoic acid from l -phenylalanine and ( E )-cinnamate in which benzaldehyde is not a metabolic intermediate. However, 30 d after the supplementation of 13 C- and 2 H- labelled l -phenylalanine, 13 C and 2 H were incorporated into all the carbon and hydrogen atoms of benzaldehyde. In addition, 2 H was not incorporated into benzaldehyde from exogenously supplemented 2 H-labelled benzoic acid. This result indicates that T. matsutake has a metabolic pathway to biosynthesize benzaldehyde from l -phenylalanine in which benzoic acid is not an intermediate. Taken together, our results strongly suggest that T. matsutake biosynthesizes benzoic acid and benzaldehyde in separate pathways.