The glowing tobacco plant contains the gene for luciferase from fireflies, which allows the plant to glow. Created at UCSD in 1986, the overall purpose was to determine the usefulness of using the gene for luciferase as a reporter for expression of other genes.
Luciferase is an enzyme which catalyzes the reaction of luciferin to light through a two step process. The reaction requires ATP and oxygen and is the same reaction used by fireflies to produce light. Though it's use as an analysis tool was just being developed when the glowing tobacco plant was first created, luciferase has been used in many systems as a reporter for gene expression. By incorporating the gene for luciferase next to the gene of interest, the luciferase protein will be translated along with the gene of interest. The advantage to using luciferase as opposed to a flourescent protein is that once luciferin is added to the system, light is emitted without the need for excitation at another wavelength (1 ).
To incorporate the luciferase gene into the tobacco plant, a construct was made which contained a CaMV 35S promoter and the luciferase gene just downstream of the promoter. The CaMV 35S promoter comes from the cauliflower mosaic virus and when transferred into plant cells, has a high activity and confers the expression of genes under control of the promoter (2 ). This construct of promoter and luciferase gene was incorporated into a plasmid and introduced to tobacco plants using the bacterial vector Agrobacterium tumefaciens. Once the plant cells were transfected, they were grown into full tobacco plants. When fed water with luciferin, the plants emitted light throughout the entire organism, but with higher emission in the roots and stem (3 ).
Purpose and ApplicationsEdit
As previously mentioned, the purpose of this experiment was to determine the usefulness of using luciferase as a reporter for gene expression. When researchers initially determined that luciferase was encoded by a single gene, the idea to use the protein as a marker for gene expression was quickly pursued. Since it can generate light with no external input of light, luciferase is an excellent enzyme for quickly observing where and when genes are expressed. The only substrates required are luciferin (which is added once detection is desired), ATP (found in all cells), and oxygen (which is ubquitous in ambient air), making the system easy to use (1 , 3 , 4 ).