Transposons as tools for functional genomics

Transposons have been used extensively for insertional mutagenesis in several plant species. These include species where highly active endogenous systems are available such as maize and Antirrhinum majus, as well as species where heterologous transposons have been introduced through transformation, such as Arabidopsis thaliana and tomato. Much of the past use of transposons has been in traditional ‘forward genetics’ approaches, to isolate and molecularly characterize genes identified by mutant phenotypes. With the rapid progress in the genome projects of different plants, large-scale transposon mutagenesis has become an important component of functional genomics, permitting assignment of functions to sequenced genes through reverse genetics. Different strategies can be pursued, depending upon the properties of the transposon such as the mechanism and control of transposition, and those of the host plant such as transformation efficiency. The successful use of these strategies in A. thaliana has made it possible to develop databases for reverse genetics, where screening for the knockout of a gene of interest can be performed by computer searches. The extension of these technologies to other plants, particularly agronomically important crops such as rice, is now feasible.