756 ISSN 1021-4437, Russian Journal of Plant Physiology, 2019, Vol. 66, No. 5, pp. 756–762. © Pleiades Publishing, Ltd., 2019. Effects of Nanoparticles on Activity of Lignan Biosynthesis Enzymes in Cell Suspension Culture of Linum usitatissimum L. F. Karimzadeh a, *, R. Haddad a , Gh. Garoosi a , and R. Khademian b a Department of Biotechnology, Faculty of Agriculture and Natural Resources, Imam Khomeini International University, Qazvin, Iran b Department of Genetic and Plant Breeding, Faculty of Agriculture and Natural Resources, Imam Khomeini International University, Qazvin, Iran *e-mail: karimzadeh.2011@yahoo.com Received May 27, 2018; revised January 22, 2019; accepted January 24, 2019 Abstract—Flax (Linum usitatissimum L.), as an important commercial crops, is a rich source of fatty acids, protein, dietary fiber and lignans. Flax plant has an effective anticancer activity due to lignan contents. Nanoparticles have recently been used as efficient non-biologic elicitors to improve the biosynthesis of sec- ondary metabolites. In this study, the effects of different concentration of ZnO (0, 30, 60, and 120 mg/L) and TiO 2 (0, 50, 100, and 150 mg/L) nanoparticles at different time (0, 24, 48, and 72 h) were investigated on enzyme activities and production of secondary metabolites in cell suspension cultures of flax. The results indicated that the highest activity of phenylalanine ammonia lyase (PAL) was observed in 30 mg/L nano- ZnO treatment at 48 h, whereas the effect of nano-TiO 2 on PAL enzyme activity was not statistically signifi- cant. According to the results, the highest activity of CAD (cinnamyl alcohol dehydrogenase) was observed in 60 mg/L concentration of nano-ZnO at different intervals. The use of 150 mg/L nano-TiO 2 led to increased activity of CAD. The maximum content of total phenol was detected at 150 mg/L nano-TiO 2 . Dif- ferent concentrations of nano-TiO 2 , caused to an increase in total lignan at all intervals. The highest amount of total phenol and lignans was observed in 30 and 60 mg/L ZnO. In the present study, we were observed dif- ferent effects of nanoparticle on enzymes activity and secondary metabolite production in cell suspension cultures of flax plant, depending on concentration and type of nanoparticles. Keywords: Linum usitatissimum, enzyme activity, nano-elicitors, plant cell culture, lignan biosynthesis, ZnO nanoparticles, TiO 2 nanoparticles DOI: 10.1134/S1021443719050078 INTRODUCTION Linum usitatissimum (flax) is one of the most ancient crops, which is cultivated for fiber as well as functional food due to its potential health benefits and medicinal purposes. Flax is mostly used in traditional medicine; it is utilized for the management of diarrhea and gastrointestinal infections. Flax contains many biologically active compounds and elements such as omega-3 fatty acids, tocopherol, phenylpropanoids, cyclic peptides, alkaloids, mucilage, and also is the richest source of plant lignans. The major lignan in flax is secoisolariciresinol diglucoside (SDG) that has numerous health benefits, especially anti-oxidant and cancer prevention properties. SDG is used to treat atherosclerosis, cardiovascular, diabetic, hemopoi- etic, and liver necrosis [1]. Secondary metabolites are organic compounds produced by bacteria, fungi, or plants, which are not essential for their growth, development and reproduc- tion. Plant secondary metabolites are basically involved in the defense mechanism and play import- ant roles in signaling processes under biotic and abi- otic environmental stress. Many secondary metabo- lites have pharmacological and therapeutic activities such as phenolics, alkaloids, terpenes, flavonoids, anthocyanins. Phenylpropanoids are a large group of secondary metabolites in plants, including flavonoids, and coumarins, and lignans [2]. They are present in structural compounds (lignin), pigments (anthocya- nins) and also play an important role in plant resis- tance to pathogens and environmental stresses [3]. Monolignols, as one of the phenylpropanoids group, are present in lignans and lignin. Phenylalanine ammonia lyase (PAL) enzyme is the first enzyme in monolignols biosynthesis pathway as leads to conver- sion of L-phenylalanine to trans-cinnamic acid. Trans-cinnamic acid is then converted to canideryl aldehyde during several successive reactions. Finally, monolignols are formed through cinnamyl alcohol Abbreviations: CAD—cinnamyl alcohol dehydrogenase; SCV— settled cell volume; SDG—secoisolariciresinol diglucoside. RESEARCH PAPERS