Figure 4.

RNA blot analysis of the expression of the SAR and ISR regulatory gene Npr1 in Arabidopsis Col-0 plants expressing ISR, SAR, or both types of induced resistance. ISR was induced by growing the plants in soil containing WCS417r (417r). SAR was induced 3 days before harvest by preinfecting three leaves per plant with Pst(avrRpt2) (avrPst). Of the Pst(avrRpt2)-induced plants, the systemic, noninoculated tissue was collected. A Npr1 gene-specific probe was used to detect Npr1 transcripts. To check for equal loading, the blots were stripped and hybridized with a gene-specific probe for β-tubulin (Tub).