An ultrastructural study of the interaction of liposomes with plant protoplasts

Nanotechnology Strategies for Plant Genetic Engineering

Plant genetic engineering is essential for improving crop yield, quality, and resistance to abiotic/biotic stresses for sustainable agriculture. Agrobacterium-, biolistic bombardment-, electroporation-, and poly(ethylene glycol) (PEG)-mediated genetic-transformation systems are extensively used in plant genetic engineering. However, these systems have limitations, including species dependency, destruction of plant tissues, low transformation efficiency, and high cost. Recently, nanotechnology-based gene-delivery methods have been developed for plant genetic transformation. This nanostrategy shows excellent transformation efficiency, good biocompatibility, adequate protection of exogenous nucleic acids, and the potential for plant regeneration. However, the nanomaterial-mediated gene-delivery system in plants is still in its infancy, and there are many challenges for its broad applications. Herein, the conventional genetic transformation techniques used in plants are briefly discussed. After that, the progress in the development of nanomaterial-based gene-delivery systems is considered. CRISPR-Cas-mediated genome editing and its combined applications with plant nanotechnology are also discussed. The conceptual innovations, methods, and practical applications of nanomaterial-mediated genetic transformation summarized herein will be beneficial for promoting plant genetic engineering in modern agriculture.

Omics and Edible Vaccines

Molecular farming provides an unprecedented approach for the production of metabolites or proteins of medicinal value from plants used previously only in agricultural setting. These plants act as protein factories that can synthesize a variety of proteins free from pathogens such as plasma proteins, growth factors, and vaccines. This method provides a novel, tempting, inexpensive, easy, and safe alternative to other techniques of protein or antigen production. With the advent of transgenic plants, it is possible to produce unlimited amounts of subunit vaccines (for oral use/edible and of parenteral use), protein used for pharmaceutical/medicinal purpose, recombinant proteins, antibodies, and industrial enzymes. Plants have numerous advantages over the production systems on account of scalability, safety, and are economic; for example, less cost of production is involved for Hepatitis B nucleocapsid antigen using transgenic tobacco. Biopharming or molecular farming provides an important resource for cheaper drug production used in the treatment of cancer, heart diseases, and infectious diseases. The pharmaceutical products are manufactured by genetically engineered plants that are extracted and purified, also known as pharmaceuticals produced by plants. Edible vaccines are cheaper in cost, easy to administer mostly by oral route, fail-safe, and are acceptable by society especially in developing countries. These vaccines are targeted to provide systemic as well as mucosal types of immunity. It has been predicted that in future children may get their immunization by munching on foods instead of getting enduring shots. The production of edible vaccines consists of the process of introducing the selected genes of desired quality into plant to induce these altered or transgenic plants to produce the encoded proteins in a natural way. These vaccines provide safer alternatives and help in reduction of cost of production and shipping and also decrease the potential hazards associated with conventional vaccines. However, becoming a reality and readily availability of edible vaccine is challenged by many problems of technical, regulatory, and nonscientific issues, which should be ruled out and rectified. This chapter provides insight into the current scenario and future applications of this new preventive modality.

The relevance of gene transfer to the safety of food and feed derived from genetically modified (GM) plants

In 2000, the thematic network ENTRANSFOOD was launched to assess four different topics that are all related to the testing or assessment of food containing or produced from genetically modified organisms (GMOs). Each of the topics was linked to a European Commission (EC)-funded large shared cost action (see http://www.entransfood.com). Since the exchange of genetic information through horizontal (lateral) gene transfer (HGT) might play a more important role, in quantity and quality, than hitherto imagined, a working group dealing with HGT in the context of food and feed safety was established. This working group was linked to the GMOBILITY project (GMOBILITY, 2003) and the results of the deliberations are laid down in this review paper. HGT is reviewed in relation to the potential risks of consuming food or feed derived from transgenic crops. First, the mechanisms for obtaining transgenic crops are described. Next, HGT mechanisms and its possible evolutionary role are described. The use of marker genes is presented in detail as a special case for genes that may pose a risk. Furthermore, the exposure to GMOs and in particular to genetically modified (GM) deoxyribonucleic acid (DNA) is discussed as part of the total risk assessment. The review finishes off with a number of conclusions related to GM food and feed safety. The aim of this paper is to provide a comprehensive overview to assist risk assessors as well as regulators and the general public in understanding the safety issues related to these mechanisms.

Enhancement of adenovirus-mediated gene transfer into dermal fibroblasts in vitro and in vivo by polyethylene glycol 6000

Gene therapy directed to the skin requires efficient transfer of the desired gene into cutaneous cells. In this study, we examined several chemical substances present in various ointments by enhancement of virus infectivity. The recombinant adenovirus vector, AxCALacZ, was used to infect dermal fibroblasts with some chemicals both in vitro and in vivo, and the expression of the LacZ gene was determined by X-Gal reaction. As the result, it was shown that PEG 6000 had the highest ability to enhance the exogenous gene expression in cultured fibroblasts with little toxicity. In vivo, it was also demonstrated that fibroblasts in mouse skin were efficiently gene transfer by adenovirus vector and 20% PEG 6000-treatment. These results suggest that this chemical treatment appears to be a simple, safe, convenient, and effective method for facilitating virus-mediated gene therapy in the skin.

Preservation of ultrastructure in phosphatidylcholine vesicles by tannic acid and OsO4

To improve preservation and visualization of membrane structure in artificial phosphatidylcholine vesicles (PC liposomes), the following three fixation formulas including tannic acid (TA) and osmium (OsO4) steps were tested: (1) TA-OsO4, (2) OsO4-TA, and (3) OsO4-TA-OsO4. The TA-OsO4 method, known to stabilize PC against conventional dehydration, was inadequate for characterizing liposome structure because it induced a serious artifact that the liposomes were aggregated and fused. On the other hand, the OsO4-TA method did not cause the artifact but only a dull EM image was obtained for the membrane structure. The best results with egg PC liposomes have been obtained by the OsO4-TA-OsO4 method which gives improved preservation and enhanced contrast of membrane structure.

Endocytosis of cationized ferritin by coated vesicles of soybean protoplasts

Soybean (Glycine max (L.) Merr.) protoplasts have been surface-labelled with cationized ferritin, and the fate of the label has been followed ultrastructurally. Endocytosis of the label occurs via the coated-membrane system. The pathway followed by the label, once it has been taken into the interior of the protoplast, appears to be similar to that found during receptor-mediated endocytosis in animal cells. Cationized ferritin is first seen in coated vesicles but rapidly appears in smooth vesicles. Labelled, partially coated vesicles are occasionally observed, indicating that the smooth vesicles may have arisen by the uncoating of coated vesicles. Structures which eventually become labelled with cationized ferritin include multivesicular bodies, dictyosomes, large smooth vesicles, and a system of partially coated reticula.

An efficient method for introducing defined lipids into the plasma membrane of mammalian cells

An efficient method has been devised to introduce lipid molecules into the plasma membrane of mammalian cells. This method has been applied to fuse lipid vesicles with the apical plasma membrane of Madin-Darby canine kidney cells. The cells were infected with fowl plague or influenza N virus. 4 h after infection, the hemagglutinin (HA) spike glycoprotein of the virus was present in the apical plasma membrane of the cells. Lipid vesicles containing egg phosphatidylcholine, cholesterol, and an HA receptor (ganglioside) were then bound to the cells at 0 degrees C. More than 85% of the vesicles were released by external neuraminidase at 0 degrees C or by simply warming the cells to 37 degrees C for 10 s, probably because of the action of the viral neuraminidase at the cell surface. However, when the cells were warmed to 37 degrees C in a pH 5.3 medium for 30 s, 50% of the bound vesicles could no longer be released by external neuraminidase. This only occurred when the HA protein had been cleaved into its HA1 and HA2 subunits. When we used influenza N virus, whose HA is not cleaved in Madin-Darby canine kidney cells, cleavage with external trypsin was required. The fact that the HA protein has fusogenic properties at low pH only in its cleaved form suggests that fusion of the vesicles with the plasma membrane had taken place. Further confirmation for fusion was obtained using an assay based on the decrease of energy transfer between two fluorescent phospholipids in a vesicle upon fusion of the vesicle with the plasma membrane (Struck, D. K., D. Hoekstra, and R. E. Pagano. 1981. Biochemistry, 20:4093-4099).