Iron toxicity-induced regulation of key secondary metabolic processes associated with the quality and resistance of Panax ginseng and Panax quinquefolius

Panax ginseng and Panax quinquefolius can survive for long periods of time in iron toxicity-stressed environments, which cause rusty roots and reduced productivity. To reveal the proteomic changes in these two Panax species in response to iron toxicity stress, plants of these two species were divided into a control group and an iron toxicity-stress group. An isobaric tags for relative and absolute quantitation (iTRAQ) proteomics approach was used to explore the changes in protein accumulation and the potential mechanisms underlying the response to iron toxicity stress in the two Panax species. Proteomic analyses revealed approximately 725 differentially expressed proteins (DEPs) in the iron toxicity-stress and control groups, including 233 and 492 proteins whose expression was upregulated and downregulated, respectively. The expression of DEPs related to photosynthesis was significantly downregulated, and DEPs whose expression was significantly upregulated were associated with redox reactions. Many upregulated DEPs were also involved in pathways such as those involving phenylpropanoid, flavonoid, isoflavone and ginsenoside synthesis. The abundance of some ginsenoside monomers (Rg1 and Rb3) also significantly increased in P. ginseng and P. quinquefolius. Moreover, P. quinquefolius contained 455 DEPs whose expression was higher than that in P. ginseng, including many proteins related to the regulation of ion homeostasis, indicating that P. quinquefolius is more resistant to iron toxicity stress than P. ginseng is.