The molecular isolation of transposable elements now permits the cloning of genes in
which the element resides. The major advantage of this system is that genes whose function is not
known can be cloned. The first step in this procedure is to identify a plant stock that is mutant
for a specific trait because a transposable element has been inserted into and inactivated the gene.
Next, a genomic library (often in bacteriophage lambda) of the plant stock is created. This
library is then screened with a clone for the transposable element. Any clone that is selected
from the screening will contain the element. In the clone, sequences for the mutated gene will lie
adjacent to the element. A sublcone containing sequences from the gene is then developed from the
non-transposable element DNA of the original clone. This clone is then used to screen a genomic
library containing DNA from a normal plant. In this manner, any clone that is selected should
contain a full, normal copy of the gene.
Because this system is so powerful, scientist have begun introducing elements from corn
and Antirrhinum into other species using transformation techniques. It has been demonstrated
that these elements can be induced to move from one location to another in the new species. If
this movement is coupled with the appearance of mutant phenotype, then the gene responsible for
the phenotype can cloned in that particular species. These techniques have now allowed the use
of transposon tagging in plant species in which active transposable elements have not been
If following link is to a lab dedicated to transposon tagging of genes.
The Fedoroff Transposon Tagging Laboratory
Copyright © 1998. Phillip McClean