Figure 3.

Summary of evidence that AvrB elicits an Rpg1-dependent HR whether delivered by P. syringae pv glycinea, P. fluorescens (pHIR11), or biolistic transformation. Top indicates the responses of soybean cultivars Acme and Harosoy to P. syringae pv glycinea and P. fluorescens (pHIR11) strains with or without avrB (33, 86). “P” indicates pathogenicity (bacterial blight symptoms); “HR” indicates rapid confluent collapse with an inoculum level of 5 × 10⁷ cells/ml and no disease development at any inoculum level; “Null” indicates no visible response. Bottom shows the effects on β-glucuronidase (GUS) activity of transient coexpression of avrB in leaf cells of Acme and Harosoy. The leaves were biolistically cobombarded with tungsten particles coated with the indicated plasmids, incubated for 24 h, and then histochemically stained for GUS activity (23), which is an indicator of the viability of the transformed cells (87). Note that the histochemically stained spots are much smaller in the Acme leaves expressing avrB and completely absent in Harosoy leaves expressing avrB.