Methyl jasmonate improves selenium tolerance via regulating ROS signalling, hormonal crosstalk and phenylpropanoid pathway in Plantago ovata.

Selenium (Se) toxicity is an emerging contaminant of global concern. It is known to cause oxidative stress, affecting plant growth and yield. Plantago ovata, a major cash crop known for its medicinal properties, is often cultivated in Se-contaminated soil. Thus, the aim of this study was to evaluate the use of methyl jasmonate (MeJA) seed priming technique to mitigate Se-induced phytotoxicity. The results demonstrated that Se stress inhibited P. ovata growth, biomass and lowered chlorophyll content in a dose-dependent manner. Treatment with 1 μM MeJA enhanced the antioxidant defence system via ROS signalling and upregulated key enzymes of phenylpropanoid pathway, PAL (1.9 times) and CHI (5.4 times) in comparison to control. Caffeic acid, Vanillic acid, Chlorogenic acid, Coumaric acid and Luteoloside were the most abundant polyphenols. Enzymatic antioxidants involved in ROS scavenging, such as CAT (up to 1.3 times) and GPOX (up to 1.4 times) were raised, while SOD (by 0.6 times) was reduced. There was an upregulation of growth-inducible hormones, IAA (up to 2.1 fold) and GA (up to 1.5 fold) whereas, the stress-responsive hormones ABA (by 0.6 fold) and SA (by 0.5 fold) were downregulated. The alleviation of Se toxicity was also evident from the decrease in HO and MDA contents under MeJA treatment. These findings suggest that MeJA can effectively improve Se tolerance and nutraceutical value in P. ovata by modulating the phytohormone regulatory network, redox homeostasis and elicits accumulation of polyphenols. Therefore, MeJA seed priming could be an efficient way to enhance stress resilience and sustainable crop production.