Molecular cloning, characterization and promoter analysis of a novel MDR-type ABC transporter gene (GbMDR1) from Ginkgo biloba

A novel MDR-type ABC transporter cDNA (designated as Gbmdr1) was cloned and characterized for the first time from the gymnosperm plant species, Ginkgo biloba, using RACE technique. The full-length cDNA of Gbmdr1 was 4275 bp, and it contained a 3840 bp open reading frame (ORF) encoding a polypeptide of 1279 amino acid with a predicted isoelectric point of 8.22 and molecular mass of 139.6 kDa. The deduced GbMDR1 protein consisted of four domains including two TMDs (74-351, 716-993) and two NBDs (428-607, 1067-1251). The promoter of the Gbmdr1 was also cloned by the Genome Walking method. Sequence analysis demonstrated that there were many regulatory elements in the Gbmdr1 promoter and the TATA box was located at -52~-56 bp upstream of the transcriptional start site. Sequence alignment and molecular evolution analysis revealed that GbMDR1 was a plant MDR-like ABC transporter protein, and that it has a further relationship with most other MDRs of plant species. Southern blot analysis indicated that Gbmdr1 belonged to a small multi-gene family. Tissue expression analysis indicated that Gbmdr1 expression was high in stems and leaves but low in roots. These results show that GbMDR1 is a MDR-like ABC transporter protein that may be involved in the transport and accumulation of secondary metabolites.