Tourist: a large family of small inverted repeat elements frequently associated with maize genes.

The wx-B2 mutation results from a 128-bp transposable element-like insertion in exon 11 of the maize Waxy gene. Surprisingly, 11 maize genes and one barley gene in the GenBank and EMBL data bases were found to contain similar elements in flanking or intron sequences. Members of this previously undescribed family of elements, designated Tourist, are short (133 bp on average), have conserved terminal inverted repeats, are flanked by a 3-bp direct repeat, and display target site specificity. Based on estimates of repetitiveness of three Tourist elements in maize genomic DNA, the copy number of the Tourist element family may exceed that of all previously reported eukaryotic inverted repeat elements. Taken together, our data suggest that Tourist may be the maize equivalent of the human Alu family of elements with respect to copy number, genomic dispersion, and the high frequency of association with genes.