Cell and Tissue Journal

Abstract Aim: The stinging nettle (Urtica dioica L.) is a very important medicinal plant that is used in the treatment of many diseases. Considering the important medicinal properties (flavonoid compounds and antioxidant enzymes) of nettle and the numerous advantages of using elicitors in plant tissue culture to enhance the production of medicinal compounds, this study investigated the effect of different concentrations of the chitosan elicitor on the production of some secondary metabolites and antioxidant enzyme activities in callus suspension culture of nettle.
Material and methods: Nettle seeds were cultured in 1/2MS medium after surface sterilization (with 1% sodium hypochlorite and 70% ethanol). leaf explants were isolated from sterile seedling (at the four-leaf stage). The explants were cultured in MS hormone-containing medium (NAA and BA 2.5 and 1 mg L^-1, respectively) and maintained under light conditions of 16 : 8 (light : darkness) hours  at 25 °C. After several stages of subculturing, uniform callus was produced. Eight days after transfer of calli to MS liquid culture medium, calli were treated with chitosan elicitor at concentrations of 0, 50, and 100 mg L^-1. Calli were sampled at 24, 48, and 120 hours after treatment. Finally, the production of secondary metabolites (quercetin, kaempferol, and rutin) was determined using HPLC and the standard line equation. Also, the activities of antioxidant enzymes (phenylalanine ammonia-lyase, polyphenol oxidase, and peroxidase) and the total content of phenol, flavonoid and protein were measured and analyzed by spectrophotometry method. The experiment was conducted in completely randomized design with three replications and was analyzed as a split-time statistical design.
Results: According to the results of the analysis of variance, the effect of chitosan elicitor concentration, sampling time after elicitor application and the interaction effect of elicitor concentration and sampling time on all measured parameters except for the total flavonoid content (the effect of elicitor concentration was not significant) were significant. The highest phenylalanine ammonia-lyase and polyphenol oxidase enzyme activities were at sampling times of 120 and 24 hours after elicitor application at 100 mg L^-1 chitosan concentration, respectively. The peroxidase enzyme activity at the sampling time of 120 hours and a concentration of 50 mg L^-1 of chitosan was 2.57 times that of the control sample. The total protein content decreased at concentrations of 50 and 100 mg L^-1 chitosan compared with the control. The highest amount of quercetin production was in the treatment of 100 mg L^-1 chitosan and sampling time of 48 hours after elicitor application, which increased 25 times compared with the control. Kaempferol and rutin had the highest production at sampling times of 48 and 24 hours and a concentration of 50 mg L^-1, respectively, which increased by 72.6 and 51.2 percent compared with the control.
Conclusion: Chitosan elicitor is known as a biotic elicitor with a positive effect on medicinal and antioxidant properties in various plants. In this study, chitosan elicitor increased the production of quercetin, kaempferol, and rutin metabolites as well as the activity of antioxidant enzymes in nettle callus culture. So, chitosan elicitor can be introduced as an enhancer of medicinal properties of nettle plant under in vitro culture conditions. Obviously, for the commercial production of medicinal compounds, the conditions for large-scale callus production in bioreactors must be optimized.

Abstract Aim: Hairy roots induced by inoculation with Agrobacterium rhizogenes are suitable for the production and accumulation of plant secondary metabolites. Genetically modified hairy roots produce valuable secondary metabolites to a greater amount and with more genetic stability than cell suspension cultures and normal roots. Catharanthus roseus is one of the most important medicinal plants that produces valuable secondary metabolites such as indole alkaloids. The purpose of this research was to investigate the effect of factors influencing the induction of hairy roots and to investigate the amount of production of secondary metabolites (vindoline and catharanthine) in the hairy roots produced by inoculation of C. roseus plant with A. rhizogenes.
Material and Methods: In order to produce sterile C. roseus seedlings and to prepare explants, seeds cultured on MS culture medium. The effect of the type of culture medium (MS, 1/2 MS and B5), the type of explant (leaf and stem), the type of bacterial strain (A4, 1132 and 2656) and the type of plant genotype (white and red) on the amount of hairy root induction in a completely randomized design was investigated. Extraction of samples was done using methanol solvent, then the amount of indole alkaloids was calculated using HPLC method and standard curve. The nature of transgenic hairy roots was confirmed after DNA extraction from different samples using PCR method with specific primers (rolB and virD).
Results: According to the results, the most efficient strain in transferring T-DNA to the explants and the appearance of hairy roots was related to A4 strain (53.8%). 1/2 MS culture medium with 77.69% of root induction was the best medium combination for the appearance of hairy roots. Also, white genotype (62% rooting) and leaf explant (77% rooting) were identified as the best genotype and explant for the production of hairy roots. After the specific amplification of the rolB gene and the lack of amplification of the virD gene in the PCR reaction in the samples, the molecular confirmation of the transgenic nature of the hairy root clones was done. Based on the results of HPLC experiment, the average amount of vindoline and catharanthine in hairy roots (0.24 and 0.615 mg/g dry weight) is higher than aerial parts (0.106 and 0.488 mg/g dry weight) and normal root (0.021 and 0.013 mg/g dry weight). The amount of these alkaloids in the aerial parts was higher than in the normal roots of the plant.
Conclusion: The production of hairy roots in response to the inoculation of plant explants with A. rhizogenes is influenced by various factors such as the type of explant, the genotype of the plant, the strain of bacteria and the composition of culture medium. These factors must be optimized to establish effective hairy root cultur in a plant. It seems that with the introduction of rol genes from bacteria to the plant genome (hairy root) and as a result of the change in the amount of endogenous hormone production and the response of the plant cell to the entry of bacterial genes, the amount and profile of the production of the secondary metabolites of the plant will change. As a result, by selecting clones with increased production of medicinally important alkaloids and optimizing the conditions of large scale production of secondary metabolites in bioreactors, we can move towards the commercial production of these compounds through cell and plant tissue culture.