August 2, 2021

Indirect method of DNA delivery in GM crops

GM crops were introduced in the U.S. in the mid-1990s. The term genetically modified (GM), as it is commonly used, refers to the transfer of genes between organisms using a series of laboratory techniques for cloning genes, splicing DNA segments together, and inserting genes into cells.

The method of transformation to generate genetically modified can be divided into two major categories: indirect and direct DNA delivery.

*Indirect method: the new DNA is introduced into the plant cell via bacteria, usually Agrobacterium tumefaciens or less commonly Agrobacterium rhizogenes.
*Direct method: In this transformation methods, the new DNA is introduced without an intermediate host and the most commonly used direct transformation method is biolistic transformation.

Genetic engineering and tissue culture are necessary to create a transgenic plant; genetic engineering to introduce the transgene (gene from another species) into the plant cell and tissue culture to regenerate the transformed cell into a whole plant.

Bacteria have in general two different types of DNA: chromosomal DNA and plasmid DNA. Chromosomal DNA is a very long molecule arranged in a chromosome, like in cells with nucleus (eukaryotes) and plasmid DNA is a small and circular DNA molecule. Plasmids are very useful for genetic engineering.

Agrobacterium tumefaciens is a soil-borne bacterium that, in nature, is capable of inserting a defined fragment of its DNA into the genome of dicotyledonous plants. The bacterium has the ability to introduce new genetic material into the plant cell. The genetic material that is introduced is called T DNA (transferred DNA) which is located on a Ti plasmid. A Ti plasmid is a circular piece of DNA.

Agrobacterium tumefaciens is a bacterium naturally able to transfer a part of its plasmid DNA into the cells of wounded plants. This extraordinary property –the ability to transfer DNA from one kingdom (bacteria) to another one (vegetal)– is unique and molecular biologists have used it to transfer selected genes into plant cells.

The natural ability to alter the plant’s genetic makeup was the foundation of plant transformation using Agrobacterium.

Some potential applications of GM crop technology are:
•Nutritional enhancement: Higher vitamin content; more healthful fatty acid profiles
•Stress tolerance: Tolerance to high and low temperatures, salinity, and drought;
•Disease resistance
Indirect method of DNA delivery in GM crops

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