Highlights Green Biotechnology II
1. Plants are important "engines" for making biotechnology products. This is for a couple of reasons. First, plants can extract energy from sunlight. Second, many plants naturally produce useful products.
2. Plants can be manipulated much more easily in culture than animals can. For example, plant cells can be propagated almost indefinitely. Animal cells, by contrast will die after a fixed number of cell divisions (by cellular suicide = apoptosis) unless they are either cancer cells or stem cells. Stem cells are hard to isolate and propagate.
3. Plant tissue can be grown independently of the plant that produces it. Thus plant cells are readily grown as masses and these masses are readily grown in bioreactors.
4. Many plants, as noted above, naturally produce useful products. Examples include willow bark (aspirin-like material) and foxglove - heart medicine (digoxigenin/dititoxin).
5. Putting genes into plants is not easy. For dicotyledonous plants like trees, a bacterium called Agrobacterium tumefaciens is very useful. Normally, it infects plants at a wound site and injects a plasmid called the Ti plasmid (actually a region of the plasmid called T-DNA) into the plant cell. This DNA gets taken up by the plant's chromosome. In the normal infectious scheme, the T-DNA contains genes that make the plant make products that the bacterium can feed on. This results in a tumor in the plant.
6. Biotechnologists have altered the T-DNA to remove the tumor causing genes and instead replace them with genes of interest, such as disease resistance, color, etc.
7. Monocots can acquire DNA by a technique called shotgun. In this technique, recombinant DNA is literally exploded into cells.
8. A bacterial gene that is commonly used to protect plants from insects is called Bt. Bt is produced by a bacterium called Bacillus thuringensis and it is deadly to insects that eat it. Bt is used as a natural insecticide and can be readily purchased over the counter. It is not harmful to people, but may harm helpful insects.
9. Recombinant plants have also been made that make the Bt protein themselves, thus removing the need to spray the protein.
10. Transformation of genes into plants has created novel organisms. Examples include Christmas trees that express the enzyme luciferase. When sprayed with luciferin, the luciferase breaks it down, producing light.
11. A more practical use of gene technology was that used to create golden rice. In this technology, the genes for making Vitamin A were introduced into rice, which gives the rice its color. Vitamin A is lacking in normal rice, so golden rice is helpful in providing this necessary vitamin to poor people who would otherwise go blind.