Ehab M. R. Metwali

Impact of application of zinc oxide nanoparticles on callus induction, plant regeneration, element content and antioxidant enzyme activity in tomato (Solanum lycopersicum Mill.) under salt stress

The properties of nanomaterials and their potential applications have been given considerable attention by researchers in various fields, especially agricultural biotechnology. However, not much has been done to evaluate the role or effect of zinc oxide nanoparticles (ZnO-NPs) in regulating physiological and biochemical processes in response to salt-induced stress. For this purpose, some callus growth traits, plant regeneration rate, mineral element (sodium, potassium, phosphorous and nitrogen) contents and changes in the activity of superoxide dismutase (SOD) and glutathione peroxidase (GPX) in tissues of five tomato cultivars were investigated in a callus culture exposed to elevated concentrations of salt (3.0 and 6.0 g L -1 NaCl), and in the presence of zinc oxide nanoparticles (15 and 30 mg L -1 ). The relative callus growth rate was inhibited by 3.0 g L -1 NaCl; this was increased dramatically at 6.0 g L -1 . Increasing exposure to NaCl was associated with a significantly higher sodium content and SOD and GPX activities. Zinc oxide nanoparticles mitigated the effects of NaCl, and in this application of lower concentrations (15 mg L -1 ) was more effective than a higher concentration (30 mg L -1 ). This finding indicates that zinc oxide nanoparticles should be investigated further as a potential anti-stress agent in crop production. Different tomato cultivars showed different degrees of tolerance to salinity in the presence of ZnO-NPs. The cultivars Edkawy, followed by Sandpoint, were less affected by salt stress than the cultivar Anna Aasa. DOI: 10.2298/ABS151105017A Key words : Nano biotechnology, in vitro culture, protein, salinity, superoxide dismutase, glutathione peroxidase Received: November 5, 2015; Revised: February 11, 2016; Accepted: February 12, 2016; Published online: March 21, 2016 How to cite this article: Alharby HF, Metwali EMR, Fuller MP, Aldhebiani AY. Impact of application of zinc oxide nanoparticles on callus induction, plant regeneration, element content and antioxidant enzyme activity in tomato (Solanum lycopersicum Mill.) under salt stress. Arch Biol Sci. 2016;68(4):723-35.

The alteration of mRNA expression of SOD and GPX genes, and proteins in tomato (Lycopersicon esculentum Mill) under stress of NaCl and/or ZnO nanoparticles.

Five cultivars of tomato having different levels of salt stress tolerance were exposed to different treatments of NaCl (0, 3 and 6 g L−1) and ZnO-NPs (0, 15 and 30 mg L−1). Treatments with NaCl at both 3 and 6 g L−1 suppressed the mRNA levels of superoxide dismutase (SOD) and glutathione peroxidase (GPX) genes in all cultivars while plants treated with ZnO-NPs in the presence of NaCl, showed increments in the mRNA expression levels. This indicated that ZnO-NPs had a positive response on plant metabolism under salt stress. Superior expression levels of mRNA were observed in the salt tolerant cultivars, Sandpoint and Edkawy while the lowest level was detected in the salt sensitive cultivar, Anna Aasa. SDS–PAGE showed clear differences in patterns of protein expression among the cultivars. A negative protein marker for salt sensitivity and ZnO-NPs was detected in cv. Anna Aasa at a molecular weight of 19.162 kDa, while the tolerant cultivar Edkawy had two positive markers at molecular weights of 74.991 and 79.735 kDa.

Improving the Salinity Tolerance in Potato (Solanum tuberosum) by Exogenous Application of Silicon Dioxide Nanoparticles

Salinity is one of the major abiotic stresses affecting potato growth and productivity in semi-arid and growing zones. An increase in salt tolerance by selecting superior potato cultivars using new biotechnology approaches and application of nanomaterial could improve the productivity and profitability of potato. In this study, two cultivars of potato were exposed to different treatments of NaCl at 50 and 100 mM and SiO2-NPs at 50 and 100 mg L -1 under in vitro and greenhouse conditions. After 35 and 90 days of treatment, different growth parameters, protein analysis and antioxidant enzyme activities were examined. Addition of NaCl to the medium induced a significant decrease in most growth traits in comparison to control and SiO2-NPs treatments with higher NaCl concentration (100 mM) having a more adverse effect on growth. Inclusion of different concentrations of SiO2-NPs to the medium reduced the deleterious effect of salinity, which was more pronounced at 50 mg L -1 SiO2-NPs than at 100 mg L -1 . A protein band was observed (22.39 kDa) which can be considered as positive marker for salt stress in cv. Sante and a novel band (70.412 kDa) corresponded to damaging mechanisms as a result of toxic effects in cv. Proventa. Cultivar Proventa was less affected by salt stress than cv. Sante. In conclusion application of SiO2-NPs at 50 mg L -1 is the optimum dose to enhance and help improving in vitro plant growth and mitigating the negative effects of salinity in potato.

Effectiveness of tissue culture media components on the growth and development of cauliflower (Brassica oleracea var. Botrytis) seedling explants in vitro

A key factor in the application of in vitro techniques to cauliflower improvement is the development of efficient protocols for regeneration of plants from tissue for use in breeding programs for the selection of the desirable genotypes under biotic and abiotic stress. Experiments were conducted to study the effect of different media components (agar or agar + sucrose or agar + Murashige and Skoog (MS) salts or agar + sucrose + MS) on callus induction and regeneration from five explants types (cotyledon, hypocotyls, shoot apex, primary root and root tip) and also the effects of auxin and cytokinin were carried out using one F 1 hybrid cauliflower cv. Medallion. The results show that cotyledons, mid roots and root apices grown on agar + MS + sugar were the most developed compared with explants on the other media. This medium was the most productive in terms of lateral root number and root length. The presence of 2,4-dichlorophenoxyacetic acid increased callus production compared to 6-benzylamino purine. Within the selected explants, a significant difference was indicated between different explants under different treatments. Liquid culture was more successful at producing viable plantlets than solid culture. Key words: Cauliflower, explants, in vitro , growth regulator, growth characters, solid and liquid culture.

Producing Transgenic Thompson Seedless Grape (Vitis vinifera) Plants using Agrobacterium tumefaciens

Under osmotic stress plant avoid it by different modification in their metabolisms such as increasing the synthesis of mRNA of delta 1-pyrroline-5-carboxylate synthase (P5CS), where P5CS is a target gene for increasing proline production and expect to improve the resistance to abiotic stress. To test this hypothesis, grape (Vitis vinifera L.) cv. Thompson Seedless was conducted to develop a protocol for high frequency regeneration and Agrobacterium mediated P5CS gene transfer. Callus induction was achieved by culture leaf explants on Nitsch and Nitsch (NN) basal medium including 2.0 mg L-1 2,4-di-chloro-phenoxy-acetic-acid + 0.5 mg L-1 Thiadiazuron solidified with 2.5 g L-1 phytagel. While for in vitro proliferation of plant, the calli were cultured on NN medium supplemented with 3.0 mg L-1 Zeatin riboside + 0.5 mg L-1 Thiadiazuron. Agrobacterium-mediated transformation using the strain LB4404 harbouring the binary vector pBI121 with the P5CS gene under CaMV 35S promoter and the bar gene as a plant selectable marker was used for transforming grape explants. A P5CS specific band (2100 bp) was amplified from DNA extracted only from the transgenic grape plants and 24% for P5CS gene was positive for the bar gene. Over expression of the abiotic stress P5CS gene was enhanced synthesis of proline to over 6 times higher in transgenic plants compared to controls. The successful transformation of genetically diverse grape cv. Thompson Seedless indicated that the transformation system may have general application to an even wider range of grapes cultivars