Host DNA damage by <i>Pseudomonas syringae</i> pv. <i>tomato</i> (<i>Pst</i>).

<p>(A–B) Accumulation of γ-H2AX during infection. Wild-type Arabidopsis Col-0 plants were vacuum-inoculated with (left to right) 10 mM MgCl₂, <i>Pst</i> DC3000, <i>Pst</i> DC3000(<i>avrRpt2</i>) or <i>Pst</i> DC3000(Δ<i>hrcC</i>) at 1×10⁷ cfu/ml. The level of γ-H2AX was monitored at (A) 2, 4, 8 h, or (B) 12, 24, 48 h after inoculation, by immunoblot using anti-γ-H2AX antibody. Controls for equivalent loading included a non-specific band detected by the antibody (control) or Ponceau S staining of the same blot. Similar results were obtained in at least three separate experiments. (C) Representative <i>Pst</i>-induced DNA damage detected by comet assay. Wild-type Col-0 plants were inoculated with 10 mM MgCl₂, or with <i>Pst</i> DC3000 or <i>Pst</i> DC3000(<i>avrRpt2</i>) at 1×10⁷ cfu/ml. Tissues were collected 8 or 16 h after inoculation and nuclei were subjected to comet assays. (D) Comet assay data presented as mean ± SE from at least 200 randomly selected nuclei for each treatment; data for 8 and 16 h are from separate experiments. **: significantly different from MgCl₂-treated control (ANOVA <i>P</i><0.01).