Exogenous Glutathione enhances tolerance of the potato ( Solanum tuberosum L.) to cadmium stress by regulating the biosynthesis of phenylpropanoid and the signal transduction of plant hormones

Background Cadmium (Cd) pollution has brought harm to the growth and development of potato. Glutathione (GSH) is an important antioxidant that may play an active role in the response of a potato to Cd stress. However, how GSH influences the effect of Cd on potatoes is unknown. In this study, we investigated the effects of exogenous GSH on the phenylpropanoid biosynthesis pathway and plant hormone signal transduction pathway in potatoes under Cd stress to explore new ideas for how potatoes respond to Cd stress. We cultured 21-day-old 'Atlantic’ plantlets in Murashige and Skoog (MS) medium supplemented with 500 μmol/L CdCl 2 or 500 μmol/L CdCl 2 + 400 μmol/L GSH. We then investigated the activities of key enzymes in the phenylpropanoid biosynthesis pathway, hormone levels, and the expression levels of related genes at different time points. Results Analysis showed that 96 h of treatment with glutathione led to an increase in the expression levels of genes encoding phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD); an increase in the enzymic activities of PAL, CAD and POD; and an increase in the content of lignin. The content of lignin was positively correlated with the expression levels of several genes (PAL: PG0031457, CAD: PG0005359, POD: PG0011640 and PG0015106). In addition, the levels of Salicylic acid (SA) and Jasmonic acid (JA) increased significantly, the expression levels of the genes encoding transcription factor TGA (PG2023696), pathogenesis-related protein 1 (PR1) (PG0005111), and the transcription inhibitor Aux/IAA (PG0006093) all increased while the expression levels of jasmonate ZIM domain-containing protein (JAZ) (PG0004367), auxin influx carrier (AUX) (PG0006550) and auxin response factor (ARF) (PG0005794) all decreased. We also observed a reduction in the content of IAA. Conclusion Exogenous GSH improved the tolerance of potato, Atlantic cv. to Cd stress by regulating the phenylpropanoid biosynthesis pathway and the plant hormone signal transduction pathway. Graphical Abstract