introducing gene into the plant cell methods

to genetically modify a plant, thousands of DNA comprising an individual gtene are transferred into an individual plant cells where the new gene becomes a permanent part of the cells genome. this process is known as "transgenic"

THE DIAGRAM

This gene transfer technique involves using a "gene gun" to shoot DNA through plant cell walls and membranes to the cell nucleus, where the DNA can combine with the plant's own genome. In this technique, the DNA is made to adhere to microscopic gold or tungsten pellets, like minuscule shotgun pellets, and is then propelled by a blast of pressurized helium. the target cells are arrayed in the line of fire allowing pellets to enter the cells. the pellet cells will enter the cell but do not exit in an appropriate condition, causing injury but not killing the cell. what happens after the pellets enter the cells is still unknown , but it was assumed that the DNA is no longer stuck on the pellet and the foreign DNA is inserted into the cell DNA, through some sort of natural genetic repair mechanismthis is the simplest method of introducing foreign DNA into cells, known as 'shotgun method' and is used in cereals like wheat, rice, maize and species unsuitable for naturally occuring engineer, agrobacterium.

agrobacterium: a naturally occurring genetic engineering agent

The most widely used biological method for transferring genes into plants uses on a trait of a naturally occurring soil bacterium, Agrobacterium tumefaciens, which causes crown gall disease. This bacterium, in the course of its natural interaction with plants, has the ability to infect a plant cell and transfer a portion of its DNA into a plant's genome. This leads to an abnormal growth on the plant called a gall. Scientists take advantage of this natural transfer mechanism by first removing the disease-causing genes and then inserting a new beneficial gene into A. tumefaciens. The bacteria then transfer the new gene into the plant.

Advantages
Depending on which genes are transferred, agricultural biotechnology can protect crops from disease, increase their yield, improve their nutritional content, or reduce pesticide use. In 2000, more than half of American soybeans and cotton and one-fourth of American corn crops were genetically modified by modern biotechnology techniques. Genetically modified foods may also help people in developing countries. One in five people in the developing world do not have access to enough food to meet their basic nutritional needs. By enhancing the nutritional value of foods, biotechnology can help improve the quality of basic diets.

how to select the right cells

When using these methods, new genes are successfully introduced into only a small percentage of the cells, so scientists must be able to "pick out" or "select" the transformed cells before proceeding. This is often done by concurrently introducing an additional gene into the cell that will make it resistant to an antibiotic. A cell that survives antibiotic treatment will most likely have received the gene of interest as well; that cell is subsequently used to propagate the new plant. There is a concern that the gene giving antibiotic resistance could naturally be transferred to bacteria once the transgenic plant is in the wild, making bacteria resistant to antibiotics that are used to fight human infection. Scientists are currently devising ways to select for transformed cells that will alleviate this issue.

It was also discovered that plant cells could be "electroporated" or mixed with a gene and "shocked" with a pulse of electricity, causing holes to form in the cell through which the DNA could flow. The cell is subsequently able to repair the holes and the gene becomes a part of the plant genome.

Traits Being Introduced Into Plants
Changes made to plants through the use of biotech- nology can be categorized into the three broad areas of input, output, and value-added traits. Examples of each are described below.

Input traits
An "input" trait helps producers by lowering the cost of production, improving crop yields, and reducing the level of chemicals required for the control of insects, diseases, and weeds.

Input traits that are commercially available or being tested in plants:

Resistance to destruction by insects Tolerance to broad-spectrum herbicides Resistance to diseases caused by viruses, bacteria, fungi, and worms Protection from environmental stresses such as heat, cold, drought, and high salt concentration

Output Traits
An "output" trait helps consumers by enhancing the quality of the food and fiber products they use.

Output traits that consumers may one day be able to take advantage of:

Nutritionally enhanced foods that contain more starch or protein, more vitamins, more anti-oxidants (to reduce the risk of certain cancers), and fewer trans-fatty acids (to lower the risk of heart disease) Foods with improved taste, increased shelf-life, and better ripening characteristics Trees that make it possible to produce paper with less environmental damage Nicotine-free tobacco Ornamental flowers with new colors, fragrances, and increased longevity

"Value-added" traits

Genes are being placed into plants that completely change the way they are used. Plants may be used as "manufacturing facilities" to inexpensively produce large quantities of materials including: Therapeutic proteins for disease treatment and vaccination Textile fibers Biodegradable plastics Oils for use in paints, detergents, and lubricants Plants are being produced with entirely new functions that enable them to do things such as: Detect and/or dispose of environmental contaminants like mercury, lead, and petroleum products

Canola Plants made Resistant to High Concentrations of Salt Through Biotechnology

Canola plants grown in the presence of a high concentration of salt. Non-genetically modified canola (non-GM) or canola genetically modified to have high, medium, or low tolerance to salt.

Plants with "input traits" that are commercially available include:

Roundup Ready® soybean, canola, and corn: resistant to treatment with Roundup herbicide that may result in more effective weed control with less tillage, and/or decreased use of other, more harmful herbicides YieldGard® corn and Bollgard® cotton: express an insecticidal protein that is not toxic to animals or humans which protects the plant from damage caused by the European corn borer, tobacco budworm, and bollworm Destiny III® and Liberator III® squash: resistant to some viruses that destroy squash

Plants may become available with "output traits" including:

High laurate canola and high oleic soybean having altered oil content to be used primarily in industrial oils and fluids rather than food High-starch potatoes that take up less oil when frying Longer shelf-life bananas, peppers, pineapples, strawberries, and tomatoes Soybeans with higher levels of isoflavones; compounds that may be beneficial in reducing some cancers and heart disease Plants that produce vaccines and pharmaceuticals for treatment of human diseases Corn with improved digestibility and more nutrients providing livestock with better feed

Source:

1 mainly about input and output traits

http://www.ext.vt.edu/pubs/biotech/443-002/443-002.html

2 mainly decribing the techniques

http://www.bookrags.com/Transgenic_plants ]

3 decribe the 2 mthods of inserting gene

book name:

Alan McHughen. (2000) a consumer's guide to GM food from green genes to red herrings. publisher: Oxford university press(NY)