ABSTRACT
The introduction of transposons into heterologous hosts by transformation and creation of transgenic transposon lines offers a myriad of novel applications. Endogenous transposons in maize and snapdragon are used for transposon tagging and isolation of genes which display a mutant phenotype. Transposon engineering and introduction into heterologous hosts augments transposon tagging by incorporating technologies developed in transgenic plant research. The use of selectable and screenable marker genes, promoter fusions, in vitro mutagenesis and PCR-based analysis/cloning are some of the developments associated with the successful use of heterologous transposons. Two maize transposon systems, Ac-Ds and En-I (Spin) have been widely used in heterologous plants, their behaviour studied, modified for improvement wherever required and employed to isolate and characterize a number of genes in Arabidopsis, petunia, tomato, tobacco and flax. The introduction of foreign transposon DNA of defined sequence, as the mutagen, expedites mutant analysis. The local transposition behaviour of maize transposons has been exploited for the development of efficient tagging strategies, involving transposon mapping in the plant genome and use of linked transposons for the targeted tagging of specific genes of interest. Most gene inac-tivations do not display a mutant phenotype, due to redundancy or other reasons. Therefore, to ascribe functions to a larger proportion of genes, transposons have been constructed and used for the entrapment of genes and regulatory sequences in the genome. The future promising uses of heterologous transposons include site-specific chromosome engineering and target-selected gene inactivation.
