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

Abstract

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 in- cluding 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 Gb- mdr1 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.