Fig 4.

Suppressor alleles of divL and cckA improve the symbiotic outcome of ∆cbrA. M. sativa plants were inoculated with S. meliloti and at 28 days post-inoculation plant height, and the percentage of phenotypically wild-type pink nodules was quantified (N = 10 plants per strain). (A and C) While the average height of plants inoculated with wild type is approximately 29 mm, the average height of plants inoculated with ΔcbrA is not significantly different from uninoculated (buffer control) plants (P = 0.9749) at approximately 10 mm. In contrast, the plant height of those inoculated with either a ΔcbrA divL or ΔcbrA cckA double mutant is significantly different from uninoculated (buffer control) plants (P < 0.0001) and more closely resembles those inoculated with wild type. (B and D) Regarding nodule development, plants inoculated with either a ΔcbrA divL or ΔcbrA cckA double mutant have a significantly increased percentage of at least 50% pink nodules in contrast to the ΔcbrA mutant rate of between 5%–10% (P < 0.0001). There is no significant difference in either (A and C) plant height or (B and D) pink nodule development in the divL and cckA single mutants when compared to the wild type. Statistical significance and P values for all comparisons were determined using a two-way ANOVA and Tukey Kramer test.