Insertional tagging of regulatory sequences in tritordeum; a hexaploid cereal species

As an approach to isolate novel cereal promoters, promoterless uidA constructs and particle bombardment were used to transform tritordeum. Five of eight transgenic lines containing uidA sequences showed evidence of promoter tagging. Expression of uidA was detected in four lines as: constitutive expression, expression in short cells of the epidermis of the spikelets, expression in pollen grains and in cells of the epidermis of the spikelet, and expression in anther primordia and pollen grains. In the fifth line, the uidA was shown by RT-PCR to be transcribed, but no GUS activity was detected. The different patterns of uidA expression indicate that different regulatory sequences were tagged in each of these lines. Analysis of the progeny resulting from self-fertilisation of the primary tagged plants, indicate that the transgenes integrated at one or two loci and the patterns of expression were stably inherited. To our knowledge, this is the first report of promoter tagging in cereals by direct gene transfer.