No abstract

The PDR5 gene from yeast encodes an ABC (ATPbinding cassette) transporter 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, the aquatic plant Spirodela polyrrhiza. We show that TUR2 transcripts accumulate throughout the plant following treatment with the steroid-like hormone, abscisic acid, and that this induction can be repressed by the adenine-derived hormone, kinetin. Furthermore, TUR2 gene expression is induced by environmental stress treatments such as low temperature and high salt. These data indicate that PDR5 homologs are present in plants, that they may function during stress conditions in an analogous fashion to that described in yeast, and that the expression of such ABC transporters is subject to a complex hormonal and environmental regulation.

SummaryPDR5-like proteins represent one group of the ABC superfamily of transporters. Members of this group are present in plants and, due to the function of PDR5-related proteins in fungi in the excretion of xenobiotics (including antifungal agents), it has been proposed that they might play a similar role in plants in the response to and detoxi®cation of herbicides and fungicides. However, until now no functional data has been presented showing an altered plant response to any herbicide or fungicide as a result of manipulating the expression of a PDR5-like gene in plants. In this paper, we show that the plant SpTUR2 PDR5-like ABC transporter is localised to the plasma membrane and that expression of this protein in Arabidopsis leads to the acquisition of resistance to the diterpenoid antifungal agent sclareol. These data both de®ne a possible endogenous substrate for this transporter and highlight the potential of manipulating plant chemical resistance via modulating the expression of speci®c PDR5-like transporters.