Analysis of the T4SS locus in Xcc 8004. (a) The mutagenesis strategy used in the deletion of T4SS (virB/D4 locus). The red and blue rectangles indicate the T4SS left and right border sequences, respectively, which were cloned and used as the target sequences in homologous recombination. The yellow rectangle indicates the deleted region of the virB/D4 locus. The larger hollow arrows indicate the CDSs and the smaller solid arrows indicate the primers used. (b) The plant assay results of the wild-type strain 8004 and the mutant 8004ΔT4 on the host plant radish (R. sativus var. radicula) cv. Manshenhong. The photographs were taken ten days after inoculation. The average lesion lengths caused by the 8004ΔT4 mutant were not significantly different from those caused by the wild type. Values are the mean ± standard deviation from 3 repeats, each with 50 leaves.