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.