McClintock and the Ac/Ds Transposable Elements of Corn

Cloning Maize Ac and Ds Elements

Molecular Features of the Maize Ac/Ds System

Transposon Tagging

Cloning the Cf-9 Gene of Tomato by Transposon Tagging

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Transposon Tagging

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 identified.

If following link is to a lab dedicated to transposon tagging of genes.

The Fedoroff Transposon Tagging Laboratory

Copyright © 1998. Phillip McClean