Fig. 3.
Effects of mutations in the WxxxE and ERMRS motifs of WtsE on the virulence of Pnss. A, the whorls of sweet corn seedlings were inoculated and rated as described in Materials and Methods. Disease severity ratings, scoring for lesion formation, were taken daily and the area under the disease progress curve (AUDPC) was calculated for days 1 to 6 after inoculation. Disease severity ratings are shown for day 5 after inoculation. Mean ratings ± SD were calculated from 24-31 plants per strain and are representative of three trials. B, growth of wild-type Pnss and wtsE derivatives in sweet corn seedlings. Whorls were inoculated with 5 × 106 CFU/plant. At daily intervals, viable cell counts were done for each of four plants per strain. The experiment was done twice and bacterial populations ± SD are the combined means from both experiments. The following Pnss strains were tested; DC283 (wild-type), AA005 wtsE∷aphT, JH037 wtsE-wxe1, JH030 wtsE-wxe2, JH039 wtsE-wxe12, JH033 wtsE-ΔFEMK, and JH042 wtsE-wxe12/ΔFEMK.