|MadSci Network: Genetics|
The ability to transfer genes from one species to another is a very common practice in molecular biology labs. What you are refering to is a gene called "luciferase" which is a protein that causes chemiluminescence (glowing) when a certain substrate is added. This is a naturally-occurring protein found in fireflies. There are several types of genes that scientists utilize as reporter genes. When we try to put DNA from one type of organism or source into another organism, we need to know not only that it got into the target cell's DNA, but also that it's being activated. The use of a simple gene that can report to us the presence of the transferred DNA by flourescence or some color change is very helpful. To make a plant glow in the dark is interesting and fun to see, but is not the ultimate purpose of the experimentor. Let's look at a possible research scenario. Perhaps the researcher wanted to see if human antibodies could be produced in plants for medical purposes. DNA containing genes for a specific antibody and the luciferase reporter are transferred to the plant cells by use of some kind of vector, i.e. some kind of transport or shuttle to deliver the desired DNA to the target. Viruses can be used as vectors, and also in the case of plants, a bacterium called Agrobacterium tumefaciens. This bacteria is able to transfer some of its genetic material into plant cells so that the plant will make some of the things it needs to survive, and also causes what is known as crown gall. Scientists can trick the bacterium into delivering the genes that they are interested in to the plant. It is relatively easy to replace the normal bacterial gene that is delivered with a gene we want to study by use of recombinant DNA techniques. So now we have a strain of Agrobacterium that carries our gene of interest, and we inoculate a plant with that bacterium. It delivers the luciferase and antibody genes to the plant nucleus where hopefully the plant is able to start producing protein from both of these new genes. How do we tell if we are successful? Well, we could just break open the cells and go through lots of long purification processes and tests to detect functional antibody made by the plants. But it is a lot easier to see if the DNA is even there by checking for luminescence conferred by the luciferase gene. IF the plant glows when we add a certain chemical to the plant, then the DNA we wanted to put in is there, and since luciferase is being made then most likely the plant is making antibodies as well. We can test all the plants that glow for antibodies and disregard the ones that don't glow. The luciferase gene reported to us that the DNA is there. If you want to have plants with almost every cell containing these genes, you transfer them to plant cells at a very early stage of development so when cells divide, the daughter cells have all the same genetic material as the parent cell. Then you can have adult plants that may be able to pass these foreign genes on to their offspring as well. Now, as to whether you can buy Agrobacterium tumefaciens, I don't know why one person would want to. Also, I am not sure, but I don't think you can buy Agrobacterium with desired genes. The genes of interest are contained on small circular pieces of DNA called plasmids, which are kind of like cassette tapes that you can put into bacteria. There are all kinds of plasmids, and each lab using this technology genetically manipulates their own and puts them into the bacteria. You can certainly find these bacteria naturally in trees that have crown gall, those big tumorous- looking knots in the trunks or branches. But unless you have a research lab with lots of equipment, biological and chemical supplies to work with the bacteria,and perform recombinant DNA technology on them, you might as well just leave it in the tree.
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