Cloning and characterization of a novel sulfate transporter gene from radish (Raphanus sativus L.)

A putative sulfate transporter gene, RSultr3.2A, was identified from radish (Raphanus sativus L.). The RSultr3.2A gene encodes a polypeptide of 651 amino acids with a calculated molecular mass of 71701 Da. The deduced amino acid sequence preserves the common motifs of the sulfate transporters and exhibits a high degree of homology to other plant sulfate transporters. RSultr3.2A was not induced by sulfur starvation and was expressed in roots, stems, leaves, flowers and young pods, suggesting a possible need for the nonregulated and constitutive sulfate transport system of the plant. The RSultr3.2A is a single copy gene in the radish genome. A genomic sequence information corresponding to RSultr3.2A cDNA was found by PCR and sequencing. Comparison of cDNA and genomic sequences revealed that the coding sequence of RSultr3.2A consisted of 12 exons. In addition, another cDNA (RSultr3.2B) from radish young pods was found. As compared with RSultr3.2A, RSultr3.2B encodes a 499 amino acid protein with modifications in the carboxy-terminus. Sequence analysis suggested an occasional donor splicing site mutation (GT to TT) in the RSultr3.2A gene from radish young pods leading to the truncated cDNA RSultr3.2B.