Role of phenylpropanoid pathway regulation in wound healing of potato tubers (P-26)

Mechanical wounding of potato tubers is a major contributor to postharvest losses as it causes desiccation, skin aberration, and increases susceptibility to pathogens during storage. Accelerating wound-healing (WH) of tubers at postharvest storage is important to mitigate wounding associated economic losses. Formation of suberin polyphenolics (SPP) at open cut surfaces of tuber tissues is the first and immediate response of potato tuber to wounding. Phenylpropanoid pathway plays a direct role in the biosynthesis of SPP and regulates the signification of tissues, both are critical steps in tuber WH. Though the overall role of phenylpropanoid pathway in tuber WH is well known, further research is needed at molecular level for developing tuber WH strategies through modulation of this critical pathway. In this research, seed tubers of cvs. Atlantic, Dakota Russet, Russet Burbank, and Shepody were used, and tuber discs (3 mm width and 11 mm diameter) were extracted from laterally excised tissue cylinder following an established mechanical wounding model. Tuber discs were then treated with (i) 2-(N-morpholino)ethanesulfonic acid (MES) buffer (control), (ii) 50 µM and (iii) 100 µM Piperonylic acid (a known inhibitor of the phenylpropanoid pathway), and (iii) an elicitor treatment (1:1 volume combination of chitosan oligosaccharide 0.125 g L⁻¹ and cranberry pomace residue 0.125 g L⁻¹), which has shown acceleration of tuber WH in previous research. Following treatments, discs were incubated at 20°C and 90% relative humidity for nine days and tuber tissues were collected at 0, 1-, 3-, 6-, and 9-days post-wounding for microscopic, biochemical, and transcriptomic analyses. Lower SPP score along with reduced content of phenylpropanoid metabolites (phenolics and flavonoids), and reduction in phenylalanine ammonia lyase activity were observed with Piperonylic acid (100 µM) treatment, while elicitor treatment enhanced SPP formation and resulted in higher phenylpropanoid metabolites in tuber tissues contributing to rapid WH of potato tubers.