FIG 1.

The ΔssuD mutant strain of USDA110 shows ineffective symbiotic nitrogen fixation with soybean. (A) Soybean plants inoculated with the ΔssuD mutant formed fewer nodules than the WT strain. (B) The nodules of the ΔssuD mutant were much smaller than those formed by the WT. Bar, 1 mm. (C) Cross section of the nodules showing decreased leghemoglobin (red) in nodules of the ΔssuD mutant compared to that in the WT. Bar, 100 μm. (D). Soybean plants inoculated with the ΔssuD mutant show stunted growth and symptoms of nitrogen deficiency (yellow leaves), compared to full growth and green leaves in the WT-inoculated plants. Bar, 1.5 cm. *, P < 0.01 versus the WT.