Antioxidant and metabolic responses of Linum album cell culture to polyethylene glycol-induced drought stress

Owing to drought stress disruptions, the physiological and biochemical homeostasis required for the plants’ growth and productivity is severely compromised. Here, we studied the adaptive mechanisms of Linum album cells exposed to drought stress. Thus, changes in the redox state, primary metabolites, and secondary metabolites were considered responding to various concentrations of polyethylene glycol (PEG) (0, 2.5, 5, 7.5, and 10%). Our observations revealed that treatment with PEG could lower fresh weight and water contents while increasing dry weight, pointing to the osmotic adjustment under water-deficit condition. The elevated levels of hydrogen peroxide and malondialdehyde which occur at 7.5% and 10% PEG can be due to the oxidative stress and membrane peroxidation. Meanwhile, antioxidant enzymes activities superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase significantly enhanced, suggesting their role in mitigating oxidative damage. The increase in nitric oxide level at 5% PEG proposes its concentration-dependent regulatory role in L. album drought adaptation. PEG treatment also reprogrammed the primary metabolites profile through a dose-dependent alteration in the content of soluble free sugars and amino acids. Furthermore, enhanced phenylalanine ammonia-lyase activity was accompanied by a considerable accumulation of phenolic acids (salicylic, cinnamic, gallic, coumaric, ferulic, and caffeic acids), flavonoids (vitexin, catechin, rutin, resveratrol, daidzein, apigenin, and naringenin), and lignans (podophyllotoxin and 6-Methoxy podophyllotoxin) occurred. Overall, these findings suggest that antioxidant enzymes activation together with metabolic flux toward phenolics and osmoprotectants accumulation contribute to L. album resilience under drought stress.