: Nanotechnology is one of the most important modern sciences that has integrated all sectors of science. Nanotechnology has been applied in the agricultural sector in the last ten years in pursuit of increasing agricultural production and ensuring food security. Plant biotechnology is an essential science that is concerned with plant production. The use of nanotechnology in plant biotechnology under controlled conditions has facilitated the understanding of important internal mechanisms of the plant biological system. The application of nanoparticles (NPs) in plant biotechnology has demonstrated an interesting impact on in vitro plant growth and development. This includes the positive effect of the NPs on micropropagation, callus induction, somatic embryogenesis, cell suspension culture, and plant disinfection. In addition, other biotechnology processes, including the genetic transformation of plants, plant conservation, and secondary metabolite production have improved by the use of NPs. Furthermore, nanotechnology is used to improve plant tolerance to different stress conditions that limit plant production. In this review article, we attempt to consolidate the achievements of nanotechnology and plant biotechnology and discuss advances in the applications of nanotechnology in plant biotechnology. It has been concluded that more research is needed to understand the mechanism of nanoparticle delivery and translocation in plants in order to avoid any future hazardous effects of nanomaterials. This will be key to the achievement of magnificent progress in plant nanobiotechnology.

Commiphora gileadensis L. is an important endangered medicinal plant that belongs to the family Burseraceae. In this study, C. gileadensis callus culture was established successfully using mature leaves as explants cultured on Murashige and Skoog (MS) media supplemented with 24.50 μM of indole butyric acid (IBA) and 2.22 μM 6-Benzylaminopurine (BAP) (callus induction media). The obtained callus was maintained on MS medium supplemented with 16.11 μM naphthalene acetic acid (NAA) in combination with 6.66 μM BAP, which resulted in a substantial increase in callus fresh and dry weights. The cell suspension culture was established successfully using liquid callus induction media supplemented with 3.0 mg·L⁻¹ proline. Thereafter, the chemical constituents of different C. gileadensis methanolic extracts (callus, cell suspension, leaves, and seeds) were profiled, and their cytotoxic and antimicrobial properties were investigated. The LC-MS GNPS analyses were applied for chemical profiling of the methanolic plant extracts, and several natural products were identified, including flavonols, flavanones, and flavonoids glycosides, with two unusual families that included puromycin, 10-hydroxycamptothecin, and justicidin B. The methanolic extracts have shown selective antimicrobial and cytotoxic properties against different microbes and cancer cell lines. For instance, leaf extract showed the highest zone of inhibition for Staphylococcus aureus, while cell suspension culture was effective against Staphylococcus epidermidis and Staphylococcus aureus. All extracts showed selective activity against A549 cell lines for the cytotoxicity assay, while the leaf extract had a broad cytotoxic effect against all tested cell lines. This study revealed that C. gileadensis callus and cell suspension cultures can be employed to increase the in vitro formation of biologically active compounds that may have cytotoxicity and antibacterial action against different cancer cell lines and bacterial species. Further studies are required to isolate and identify such constituents that corroborate the observed activities.

Quinoa (Chenopodium quinoa) is of great economic importance and constitutes one of the model plants for salinity and drought tolerance in the Mediterranean climate. This study aimed to study the physiological responses of Q6 (a quinoa line developed by International Center for Bio-saline Agriculture (ICBA) in cooperation with the National Center for Agricultural Research (NARC), Jordan) grown under in vitro salt-stressing conditions (MS Media plus either 0, 25, 50, 75, 100, 150, or 200 mM of NaCl) and to determine the highest salt level that Q6 plantlets can tolerate. After this, different levels of chemically synthesized silver nanoparticles (Ag NPs) (25, 50, and 75 mg/L) were added to the growth MS media to examine if they can boost the mitigation powers of Q6 plantlets against the highest salt level that the Q6 plantlets could tolerate. Data showed that all tested growth parameters were negatively affected by adding NaCl to the media at all levels. Shoot length, proliferation, and fresh and dry weights declined to reach minimum values at 200 mM NaCl when compared to the other NaCl levels. Similarly, chlorophyll, protein, and ion content were negatively affected when exposed to NaCl at all levels, while proline increased significantly with increasing NaCl in the growth media. The addition of Ag NPs resulted in improving the mitigation powers of Q6 plantlets, especially when 75 mg/L Ag NPs were added, as this resulted in a significant improvement in microshoot growth under 200 mM NaCl when compared to the control. Adding 75 mg/L of Ag NPs to 200 mM NaCl improved shoot growth (3.56 cm) when compared to (1.04 cm) obtained plantlets that were grown in 200 mM NaCl alone. Further, other growth parameters were almost doubled by adding 75 mg/L of Ag NPs to 200 mM NaCl when compared to 200 mM NaCl alone. Additionally, adding Ag NPs (especially at the 75 mg/L level) to the media improved total chlorophyll, protein, and ion content while also reducing proline when compared to the control, which indicated an improvement in microshoot tolerance to salt-stressing conditions. These results indicate that adding specific concentrations of Ag NPs improves the growth performance and stress tolerance of Q6 grown under salt-stressing conditions.

In vitro preservation of transgenic tomato lines overexpressing the stress-responsive transcription factor SlAREB1 was studied by using slow growth and cryopreservation techniques. Slow growth preservation was performed by using different concentrations of sucrose (0, 100, 200, 300 mm) and abscisic acid (0, 4, 8, 12 μm) in Murashige and Skoog (MS) media, while cryopreservation was conducted by using encapsulation dehydration, V-cryoplates and seeds. Significant differences were observed between tested lines grown on MS media supplemented with 200 mm sucrose where transgenic lines overexpressing SlAREB1 showed improved growth when compared with negative control. The addition of abscisic acid (ABA) to the preservation media affected negatively transgenic lines growth and development when compared with ABA-free media. In encapsulation dehydration, non-cryopreserved transgenic lines overexpressing SlAREB1 pretreated in 0.8 M sucrose for 1 day and subjected to different dehydration periods showed significantly higher survival percentages when compared with negative control. For V-cryoplates technique, cryopreserved transgenic lines overexpressing SlAREB1 treated in 0.3 M sucrose for 3 days with or without cold acclimatization showed significantly higher survival percentages when compared with the negative control. Seed cryopreservation was performed successfully with a clear reduction in germination percentage in transgenic lines overexpressing high levels of SlAREB1. In conclusion, transgenic tomato lines overexpressing SlAREB1 were found to improve tolerance against different abiotic stresses associated with different in vitro preservation protocols.