Isolation and characterization of an auxin-binding protein gene from radish, and its expression in insect cells

Auxin-binding protein (ABP1) is a putative receptor for auxin in the plasma membrane. We isolated a full-length cDNA encoding ABP1 from radish by screening a cDNA library with its partial cDNA fragment generated by the reverse transcriptase-polymerase chain reaction (RT-PCR) method. Radish abp1 mRNA was highly expressed in cotyledons, hooks and hypocotyls, and less so in roots of radish seedlings. The deduced amino acid sequence of radish abp1 consisted of conserved auxin-binding motifs, a signal peptide and ER-retention signal, and contained two potentially N-linked glycosylation signals. To analyze the biochemical properties of the radish abp1 product, this cDNA was expressed in insect cells by the baculovirus vector system. The result of tunicamycin-treatment showed that the signal peptide was cleaved and that the radish abp1 product was glycosylated at both target sites in insect cells.