Chemical Elicitors-Induced Variation in Cellular Biomass, Biosynthesis of Secondary Cell Products, and Antioxidant System in Callus Cultures of Fagonia indica.

Fagonia indica is a rich source of pharmacologically active compounds. The variation in the metabolites of interest is one of the major issues in wild plants due to different environmental factors. The addition of chemical elicitors is one of the effective strategies to trigger the biosynthetic pathways for the release of a higher quantity of bioactive compounds. Therefore, this study was designed to investigate the effects of chemical elicitors, aluminum chloride (AlCl3) and cadmium chloride (CdCl2), on the biosynthesis of secondary metabolites, biomass, and the antioxidant system in callus cultures of F. indica. Among various treatments applied, AlCl3 (0.1 mM concentration) improved the highest in biomass accumulation (fresh weight (FW): 404.72 g/L) as compared to the control (FW: 269.85 g/L). The exposure of cultures to AlCl3 (0.01 mM) enhanced the accumulation of secondary metabolites, and the total phenolic contents (TPCs: 7.74 mg/g DW) and total flavonoid contents (TFCs: 1.07 mg/g DW) were higher than those of cultures exposed to CdCl2 (0.01 mM) with content levels (TPC: 5.60 and TFC: 0.97 mg/g) as compared to the control (TPC: 4.16 and TFC: 0.42 mg/g DW). Likewise, AlCl3 and CdCl2 also promoted the free radical scavenging activity (FRSA; 89.4% and 90%, respectively) at a concentration of 0.01 mM, as compared to the control (65.48%). For instance, the quantification of metabolites via high-performance liquid chromatography (HPLC) revealed an optimum production of myricetin (1.20 mg/g), apigenin (0.83 mg/g), isorhamnetin (0.70 mg/g), and kaempferol (0.64 mg/g). Cultures grown in the presence of AlCl3 triggered higher quantities of secondary metabolites than those grown in the presence of CdCl2 (0.79, 0.74, 0.57, and 0.67 mg/g). Moreover, AlCl3 at 0.1 mM enhanced the biosynthesis of superoxide dismutase (SOD: 0.08 nM/min/mg-FW) and peroxidase enzymes (POD: 2.37 nM/min/mg-FW), while CdCl2 resulted in an SOD activity up to 0.06 nM/min/mg-FW and POD: 2.72 nM/min/mg-FW. From these results, it is clear that AlCl3 is a better elicitor in terms of a higher and uniform productivity of biomass, secondary cell products, and antioxidant enzymes compared to CdCl2 and the control. It is possible to scale the current strategy to a bioreactor for a higher productivity of metabolites of interest for various pharmaceutical industries.

Lead (Pb) bioaccumulation and antioxidative responses in Tetraena qataranse.

Lead (Pb) is the second most toxic metal on Earth and is toxic to humans and other living things. In plants, Pb commonly inhibits growth when it is at a concentration in the soil of 30 mg/kg or more but several Pb tolerant plants have been reported. However, few studies have focused on plant response to Pb exposure, particularly at concentrations higher than 30 mg/kg. The assessment and evaluation of metal dose-dependent plant responses will assist in future phytoremediation studies. Therefore, this work documents the Pb concentration-dependent antioxidative response in Tetraena qataranse. Young seedlings were irrigated with 0, 25, 50, and 100 mg/L Pb every 48 h for seven weeks under greenhouse conditions. A phytotoxicity test showed that at the lowest treatment concentration, Pb stimulates growth. However, at 100 mg/L (1600 mg/kg Pb in the growth medium at harvest), the metal disrupted healthy growth in T. qataranse, particularly root development. Metal accumulation in the root was higher (up to 2784 mg/kg) than that of the shoot (1141.6 mg/kg). Activity assays of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and glutathione reductase (GR) showed a progressive increase in enzymatic activities due to Pb treatment. Together, the results of this study suggest that T. qataranse is a Pb hyperaccumulator. Increased antioxidant enzyme activity was essential to maintaining cellular homeostasis and assisted in the arid plant's tolerance to Pb stress.

Differential Effects of Thidiazuron on Production of Anticancer Phenolic Compounds in Callus Cultures of Fagonia indica.

Fagonia indica, a very important anticancer plant, has been less explored for its in vitro potential. This is the first report on thidiazuron (TDZ)-mediated callogenesis and elicitation of commercially important phenolic compounds. Among the five different plant growth regulators tested, TDZ induced comparatively higher fresh biomass, 51.0 g/100 mL and 40.50 g/100 mL for stem and leaf explants, respectively, after 6 weeks of culture time. Maximum total phenolic content (202.8 µg gallic acid equivalent [GAE]/mL for stem-derived callus and 161.3 µg GAE/mL for leaf-derived callus) and total flavonoid content (191.03 µg quercetin equivalent [QE]/mL for stem-derived callus and 164.83 µg QE/mL for leaf-derived callus) were observed in the optimized callus cultures. The high-performance liquid chromatography (HPLC) data indicated higher amounts of commercially important anticancer secondary metabolites such as gallic acid (125.10 ± 5.01 µg/mL), myricetin (32.5 ± 2.05 µg/mL), caffeic acid (12.5 ± 0.52 µg/mL), catechin (9.4 ± 1.2 µg/mL), and apigenin (3.8 ± 0.45 µg/mL). Owing to the greater phenolic content, a better 2-2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity (69.45 % for stem explant and 63.68 % for leaf explant) was observed in optimized calluses. The unusually higher biomass and the enhanced amount of phenolic compounds as a result of lower amounts of TDZ highlight the importance of this multipotent hormone as elicitor in callus cultures of F. indica.

ROS generation and proline metabolism in calli of halophyte Nitraria tangutorum Bobr. to sodium nitroprusside treatment.

Nitric oxide (NO) is a stress factor or a signal molecule involved in various plant physiological and developmental processes. In the present study, the generation of reactive oxygen species and the metabolism of proline due to different sodium nitroprusside (SNP, an NO donor) concentrations were investigated in callus from halophyte Nitraria tangutorum Bobr. Treatment with SNP led to significant increases of hydrogen peroxide (H2O2) content and cell viability but notable reductions in hydrogen radical level and lipid peroxidation degree, and superoxide onion (O2 (-)) content also enhanced in 100 µM SNP-treated calli. Using a chemical inhibitor for plasma membrane (PM) NADPH oxidase diphenylene iodonium (DPI), we found low O2 (-) generation in untreated and 25 µM SNP-treated calli, whereas in those treated with 100 µM SNP O2 (-) level exhibited a very little alteration, comparable to the absence of DPI. These suggest a high activity of PM NADPH oxidase in untreated calli. H2O2 scavenging enzymes (catalase, peroxidase [POD] and ascorbate peroxidase) and H2O2 forming enzymes (superoxide dismutase [SOD], cell wall-POD and diamine oxidase [DAO]) stimulated significantly in calli treated with different SNP concentrations while glutathione reductase activity decreased. In addition, a reduction in proline content was observed in SNP-treated calli. Moreover, different SNP concentrations stimulated proline dehydrogenase (PDH) and ornithine δ-aminotransferase but inhibited r-glutamyl kinase (GK). In conclusion, our results suggest that the increasing H2O2 generation was associated with the stimulation of SOD, cell wall-POD and DAO, and that the reduction of proline content might be the consequence of increased PDH activity and decreased GK activity in N. tangutorum Bobr. calli under SNP treatment.