Identification of transposon-tagged genes by the random sequencing of Mutator-tagged DNA fragments from Zea mays

We have used a universal adaptor amplification procedure to isolate random Mutator-tagged fragments from Mutator-active maize plants. Direct sequence characterization of 761 Mutator-tagged fragments indicated that a significa nt number were homologous to sequences within the public databases. The abi lity of Mutator-tagged fragments to detect homology was not related to the length of the sequence within the range 100-400 bp. However, fragments abov e this size did show an increased chance of detecting homology to either ex pressed sequence tags or genes. Characterization of the insertion sites of the Mutator elements suggested that while it does target transcribed region s, Mutator does not appear to have any site preference within the transcrip tion unit. Hybridization of previously unidentified Mutator-tagged fragment s to arrayed cDNA libraries confirmed that many of these also showed homolo gy to transcribed regions of the genome. Examination of back-crossed progen y confirmed that all the insertions examined were germinal; however, in all but one case, selfing five individual Mutator-tagged lines failed to revea l an obvious phenotype. This study suggests that the random sequencing of M utator-tagged fragments is capable of producing both a significant number o f interesting transposon tagged genes and mutant plant lines, all of which could be extremely valuable in future gene discovery and functional genomic s programmes.