Chitosan-induced phenolics production is mediated by nitrogenous regulatory molecules: NO and PAs in Linum album hairy roots

Due to medicinal value, phenolics are of great interest. Many investigations have already been conducted on Linum album Kotschy ex Boiss to increase these valuable compounds especially lignans. In the present work, the hairy roots of the L. album were treated with 200 mg L −1 chitosan for 12, 24, 48, and 72 h and the lignan contents were determined by high performance liquid chromatography (HPLC). To understand the governing upstream routes, the contents of hydrogen peroxide (H 2 O 2 ), nitric oxide (NO), salicylic acid (SA), the activity of antioxidant enzymes, the amino acids, polyamines, and phenylpropanoids were determined by HPLC and spectroscopy techniques. The levels of regulatory molecules (H 2 O 2 , NO, and SA) enhanced at first hours of treatment and the antioxidant enzymatic activities increased in correlation with them. This observation might be attributed to adjustment of the oxidative status and direction of the elicited cells toward specific defensive responses. The content of amino acids, polyamines, and phenylpropanoids underwent a time-dependent reprogramming. The amino acid metabolism shifted toward the elevated levels of glutamate, aspartate, arginine, methionine, phenylalanine, and tyrosine after 24 h as well as correlated with the modulation of polyamines and phenylpropanoids. After 72 h, there was a channeling of the cell metabolism towards the accumulation of secondary metabolites, mainly podophyllotoxin, 6-methoxy podophyllotoxin, catechin, and vitexin. These results propose the complex relationship between the regulatory molecules and the profile of nitrogenous compounds enhanced the phenolics accumulation. Key Message Chitosan treatment of Linum album hairy roots activates signaling network accompanied by modulation of nitrogenous compounds and alteration of defensive pathways towards production of phenylpropanoids.