Gene tagging by endogenous transposons

Abstract

Gene tagging by transposons (transposon tagging) is one of the most useful methods to identify and isolate specific genetic loci of an organism. It was first applied in Drosophila [ 1 ] and then in several plant species, until recently most often and successfully in maize and Antirrhinum (for an overview of attempts in these plant species see [4, 12]). However, there should be many other good candidates for this approach as listed in [8]. The advantage of transposon mediated cloning over most other gene isolation methods is that, except for a mutant phenotype, no other information on the gene product or its function is required. The two major keys to the method of transposon tagging are:

• 1 that integration of a transposon (mobile DNA element) into a genetic locus often leads to a loss of its function whereas excision from that locus may result in partial or full restoration for its original tasks. (In a minority of the cases the tagged gene becomes ectopically expressed, transposon excision also leading to restoration of its original boundaries of function).

• 2 that excision and integration of a transposon result in a change in the physical size of the donor site as well as that of the new insertion site. As a consequence, the results of transposition become detectable as Restriction Fragment Length Polymorphisms (RFLPs) when the transposon is used as a molecular probe (Fig. 1).