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. 2006 Oct;18(10):2836–2853. doi: 10.1105/tpc.106.045633

Figure 9.

Figure 9.

Application of Iron or Siderophores Restores the Virulence of the A. brassicicola Δnps6 Strain to the Host.

(A) and (B) Exogenous application of ferric citrate or DFO enhances the virulence of Δnps6 strains of A. brassicicola to Arabidopsis.

(A) Second and third true leaves, in pairs, of Arabidopsis ecotype Di-G drop-inoculated with the wild-type strain and Δnps6 strain Abnps6-9 of A. brassicicola, 4 d after inoculation. Pairs of mock-inoculated control leaves are shown at right in each row. Plants were pretreated with 0.5 mM ferric citrate, 0.25 mM DFO, or 0.25 mM iron-saturated DFO. Iron and DFO were dissolved in 1 g/L Glucopon 215 CS UP solution, and control plants (top row) were pretreated with Glucopon 215 CS UP solution alone.

(B) Average vertical lengths of lesions formed by wild-type and Δnps6 strains of A. brassicicola are shown for each treatment. A statistically significant enhancement in virulence of the A. brassicicola Δnps6 strain was observed when iron, DFO, or iron-saturated DFO (right) was applied (P < 0.01). Error bars indicate 95% confidence intervals (lesion size [mm]: Δnps6 = 1.90 ± 0.41; wild type = 4.05 ± 0.37; Δnps6 with iron = 3.90 ± 0.62; Δnps6 with DFO = 4.1 ± 0.46; Δnps6 with iron-saturated DFO = 4.5 ± 0.37).

(C) and (D) Application of Nα-dimethylcoprogen, the extracellular siderophore produced by A. brassicicola, restores wild-type virulence to Arabidopsis to the Δnps6 strain.

(C) Second and third true leaves, in pairs, of Arabidopsis ecotype Di-G infected by the wild-type strain and Δnps6 strain Abnps6-9 of A. brassicicola, 4 d after inoculation. Mock-inoculated controls are shown at right in all rows. Plants were pretreated with crude extracts prepared from cultures of wild-type and Δnps6 strains grown under iron-depleted conditions or 0.2 mM Nα-dimethylcoprogen purified from the crude extract of the wild-type culture. Control plants were pretreated with 1 g/L Glucopon 215 CS UP solution.

(D) Average vertical lengths of lesions formed by wild-type and A. brassicicola Δnps6 strains are shown for each treatment. Application of crude extract from wild-type culture or Nα-dimethylcoprogen led to a statistically significant enhancement in virulence of the A. brassicicola Δnps6 strain (P < 0.01). Error bars indicate 95% confidence intervals (lesion size [mm]: Δnps6 with wild-type crude extract = 4.00 ± 0.65; Δnps6 with Δnps6 crude extract = 1.60 ± 0.43; Δnps6 = 1.50 ± 0.33; wild type = 4.50 ± 0.44; Δnps6 with siderophore = 4.3 ± 0.59).