Molecular cloning and expression analysis of PDR1-like gene in ginseng subjected to salt and cold stresses or hormonal treatment

The plant pleiotropic drug resistance (PDR) family of ATP-binding cassette (ABC) transporters is potentially involved in diverse biological processes. Currently, little is known about their actual physiological functions. A Panax ginseng PDR transporter gene (PgPDR1) was cloned and the cDNA has an open reading frame of 4344 bp. The deduced amino acid sequence contained the characteristic domains of PDR transporters: Walker A, Walker B, and ABC signature. Genomic DNA hybridization analysis indicated that one copy of PgPDR1 gene was present in P. ginseng. Subcellular localization showed that PgPDR1-GFP fusion protein was specifically localized in the cell membrane. Promoter region analysis revealed the presence of cis-acting elements, some of which are putatively involved in response to hormone, light and stress. To understand the functional roles of PgPDR1, we investigated the expression patterns of PgPDR1 in different tissues and under various conditions. Quantitative real-time PCR (qRT-PCR) and Western blotting analysis showed that PgPDR1 was expressed at a high level in the roots and leaves compared to seeds and stems. The expression of PgPDR1 was up-regulated by salicylic acid (SA) or chilling, down-regulated by ABA, and regulated differently at transcript and protein levels by MeJA. These results suggest that PgPDR1 might be involved in responding to environmental stresses and hormones.