Transcription and synthesis of phenols in the phenylpropanoid synthesis pathway.
The KEGG pathway analysis of DMs in EICL vs. EFCL revealed that ”phenylpropanoid biosynthesis” and ”tyrosine metabolism” were significantly enriched. Most phenylpropanoids took L-phenylalanine and L-tyrosine as raw materials and synthesized corresponding metabolites through deamination, hydroxylation, and coupling reactions. Thus, we constructed the transcription and synthesis roadmap of phenols in the phenylpropanoid synthetic pathway.
In the L-phenylalanine metabolic pathway, endophytes had no significant effect on the contents of L-phenylalanine, cinnamic acid, and 2-hydroxy-cinnamate in the phenolic synthesis pathway of L-phenylalanine, regardless of whether the pathogen was inoculated (Fig. 5). After pathogen inoculation, endophytes significantly inhibitedPAL and C4H expression (Fig. 5). In the L-tyrosine metabolic pathway, endophytes promoted the accumulation of ferulic acid, p-coumaroylagmatine, feruloylputrescine, and sinapic acid before pathogen inoculation (Table 1; Fig. 5). After pathogen inoculation, the endophyte significantly induced the PTAL expression, and the contents of p-coumaroylagmatine and feruloylputrescine were higher in EI than that in EF. These results suggest that endophytes may promote phenols synthesis through the L-tyrosine metabolism pathway.