NodD repression correlates with NodD binding. (A) β-Galactosidase activities for the nodD promoter. In each pair of columns, the left column represents β-galactosidase activity in the absence of the nodD gene (assayed in R.leguminosarum 8401), whereas the right stands for β-galactosidase activity in the presence of the nodD gene [assayed in R.leguminosarum 8401 (pIJ1518)]. (B) NodD binding to wild-type and mutant nodD promoters. Lanes 1, 3 and 5, migration of labeled wild-type and two mutant DNA fragments in the absence of NodD protein; lanes 2, 4 and 6, as lanes 1, 3 and 5 but in the presence of 0.3 µg Form II NodD protein and 100 ng ctDNA. The intensities of free and shifted DNA bands were scanned on a Shimadzu CS-930 TLC scanner and were analyzed for the percent of shifted DNA against total free DNA. Wild-type, 40%; m1, 6%; m2, 65%.