Figure 2.

Induction of PR-1 gene expression Plants of the indicated genotype were inoculated with 1 × 10⁶ bacteria mL^-1 DC3000 carrying the specified avirulence gene or the empty vector or a 10 mM MgCl₂ blank. At the indicated time points, leaf samples were taken for total RNA preparation. Probes derived from the PR-1 cDNA were used for Northern blots. Quantitation was with a phosphorimager. All blots were stripped and probed again with a radiolabeled probe made from the ROC1 cDNA as a control for RNA loading. These values were used for data normalization. Each bar represents a mean of data from 3 separate experiments. Differences between means were assessed for statistical significance using Student's t tests. Lowercase letters indicate statistically significant differences between means (P < 0.05 or in many cases greater significance). Comparisons of means were made separately for the two time points.