Molecular Biotechnology: Principles and Applications - Glick B., Pasternak J. 2002

Molecular Biotechnology of Microbial Systems
Plant Genetic Engineering: Methodology
Physical Methods of Gene Transfer into Plant Cells

A. tumefaciens-mediated Gene transfer systems are highly effective only for certain plant species. In particular, monocots, including major cereal crops (rice, wheat, and maize), are virtually untransformable by A. tumefaciens. Nevertheless, by modifying protocols and carefully controlling conditions, researchers have successfully transformed maize and rice using A. tumefaciens carrying Ti-plasmid-derived vectors. For example, immature maize embryos were immersed for a few minutes in an A. tumefaciens Cell suspension and then incubated for several days in the absence of selective pressure. Thereafter, the embryos were transferred to an antibiotic-containing medium that allowed only transformed plant Cells to grow. These cells were kept in the dark for several weeks, after which the mass of transformed plant cells was transferred to another nutrient medium and incubated in the light to regenerate a whole transgenic plant. Table 17.1 lists several Methods for transforming monocotyledonous plants. Some of these methods require Cell wall removal to yield protoplasts. The latter are maintained in culture as independently growing cells or in a special nutrient medium where they regenerate cell walls; a whole plant can then be regenerated from these cells. In addition, transformation methods have been developed that allow the Introduction of a cloned gene into a small number of cells within a plant tissue from which a whole plant can be regenerated, bypassing The Need for protoplast regeneration. Currently, the preferred methods for delivering DNA into plant cells are either Ti-plasmid-based vectors or Microparticle Bombardment (Table 17.1). More than 50 different plant species have been genetically transformed using these approaches (Table 17.2).

Class="center">Table 17.1. Methods for introducing DNA into plant cells

Table 17.2. Genetically transformed plants