Figure 6.

RHC with enclosed rhizobia is absent in the ern1-1 ern2-1 double mutant. Wild-type A17 and ern1-1 ern2-1 RHs were imaged after inoculation with S. meliloti (visualized in green). At 2 dpi, RHs are usually deformed in both A17 (A and B) and ern1-1 ern2-1 (D and E) lines. At this stage, RHCs are frequent in A17 (arrow in B) while in the double mutant most RHs display RH tip swelling (arrows in E). This RH swelling becomes more pronounced over time as illustrated at 4 dpi (arrows in G) and is not observed in noninoculated conditions (H). In some rare cases, loose curls can be observed in ern1-1 ern2-1 roots (F). But in this case, curling is not complete and although numerous rhizobia are associated with these RHs, they are not entrapped within the curl, in contrast to the wild-type situation shown in C. Bars = 200 μm (A and D); 40 μm (B, E, G, and H); 10 μm (C and F).