CsPDR8 and CsPDR12, two of the 16 pleiotropic drug resistance genes in cucumber, are transcriptionally regulated by phytohormones and auxin herbicide in roots

Abstract

There are 15 and 23 members of the pleiotropic drug resistance (PDR) proteins, a subfamily of ATP-binding cassette (ABC) transporters, in Arabidopsis thaliana and Oryza sativa, respectively. Until recently, only a few members of Arabidopsis thaliana PDRs (AtPDRs) had been characterized in detail but growing reports indicate that proteins of this family may participate in growth regulator-mediated signaling and phytohormone transport. The profile of Oryza sativa PDRs (OsPDRs) expression in response to different stimuli also suggests that some rice PDRs are associated with a phytohormone-mediated response to environmental changes. Due to the lack of full genome resources, only individual members of PDRs in other plants (Nicotiana, Oryza, Glycine or Spirodela) have been studied. We have previously cloned two full cDNA sequences encoding for cucumber homologs of Arabidopsis PDR8 and PDR12. Here, we present the genomic organization of 16 cucumber PDRs and the phylogeny of the predicted Cucumis sativus PDR (CsPDR) proteins. Further analysis of CsPDR8 and CsPDR12 reveal that these cucumber genes are constitutively expressed mainly in roots of young seedlings and flowering plants (CsPDR8 and CsPDR12), and in flowers (CsPDR12). In roots, the transcript of CsPDR8 decreased in response to ABA and markedly raised in the presence of ACC, salicylic acid or jasmonic acid. In comparison, the expression of CsPDR12 was not affected by ACC and significantly increased upon the addition of jasmonic acid, salicylic acid, 2,4-D, kinetin or ABA to the growth media. These data suggest that CsPDR8 and CsPDR12 may be involved in a phytohormone-mediated response of plants to different stimuli by sharing different signaling pathways.