Activation of phenylpropanoid pathway by L-phenylalanine promotes suberin polyphenolic and lignin deposition in wounded potato tubers.

Wound healing is essential for maintaining postharvest quality in potato tubers, and phenylpropanoid metabolism plays an important role in forming protective aromatic barriers at wound sites. This study investigated whether exogenous L-phenylalanine (L-Phe) could enhance wound responses associated with phenylpropanoids in wounded potato tubers. Treatment with 0.05 mmol L-1 L-Phe increased the activity of phenylpropanoid-related enzymes, including phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), 4-coumarate: CoA ligase (4CL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD). This was associated with higher accumulation of selected phenylpropanoid-related acids, soluble monolignols, total phenolics, and lignin-associated aromatic wall material at wounds. Microscopy further showed enhanced deposition of suberin polyphenolic (SPP) material and expansion of the wound-associated lignified zone in L-Phe-treated tubers. These structural and biochemical responses were accompanied by reduced weight loss and a modest reduction in disease severity during healing. Collectively, these results suggest that exogenous L-Phe enhances phenylpropanoid-associated aromatic wound-barrier development in potato tubers.