Fig. 1.

dnf4 is unable to develop functional nodules. (A) Plants were inoculated with S. medicae ABS7 and grew for 4 wk. Yellow leaves are the sign of nitrogen deficiency. (Scale bar: 10 mm.) (B) dnf4 nodules remain small and white, whereas the wild type nodules elongate and show pink color. (Scale bar: 1 mm.) (C) Toluidine blue staining of 10-dpi nodules inoculated with ABS7. (Scale bar: 100 μm.) (D) Magnification of boxed areas in C. Elongated bacteroids stain dark blue. dnf4 nodules show degradation of symbiosomes and host cells at the nitrogen fixation zone proximal to the root. (Scale bar: 20 μm.)