HORMONAL AND ENVIRONMENTAL-REGULATION OF A PLANT PDR5-LIKE ABC TRANSPORTER

The PDR5 gene from yeast encodes an ABC (ATP-binding cassette) transpo rter involved in the ATP-dependent efflux of a variety of structurally unrelated cytotoxic compounds. We report here on the cDNA cloning and characterization of a PDR5 homolog (TUR2) from a higher eukaryote, th e aquatic plant Spirodela polyrrhiza. We show that TUR2 transcripts ac cumulate throughout the plant following treatment with the steroid-lik e hormone, abscisic acid, and that this induction can be repressed by the adenine-derived hormone, kinetin. Furthermore, TUR2 gene expressio n is induced by environmental stress treatments such as low temperatur e and high salt. These data indicate that PDR5 homologs are present in plants, that they may function during stress conditions in an analogo us fashion to that described in yeast, and that the expression of such ABC transporters is subject to a complex hormonal and environmental r egulation.