The copy number and position of the insertion of the AphVIII marker gene in the SO₄  ²⁻ transporter mutants. A, Diagram showing the site of AphVIII insertion in the SLT1, SLT2, and SULTR2 genes. Black bars, gray bars, and white bars represent exons, introns, and untranslated regions, respectively. B, DNA gel-blot analysis of wild-type, slt1, slt2, and sultr2 strains. Genomic DNA was digested with PstI, separated by agarose gel electrophoresis, transferred to a nitrocellulose membrane, and hybridized with the 1.7-kb PSAD::AphVIII PCR fragment. Asterisks designate the newly introduced PSAD::AphVIII gene sequences. Size standards (in kb) are shown to the left.