FIG 2 .

Contributions of the reb operon to R-body formation in stem nodules. S. rostrata plants were inoculated with the WT or ΔpraR, ΔAZC_3781-7, or ΔpraR ΔAZC_3781-7 mutant strains and grown at 30°C. Stem nodules were analyzed at 14 days postinoculation (dpi). (A) Hand-cut images (upper) and acetylene reduction activities (ARAs) reflecting nitrogen-fixing activities (lower) of stem nodules. Values are presented as means ± standard deviations from five separate plants. Different letters indicate significant differences (P < 0.05, Tukey-Kramer). (B) Quantitative reverse transcription-PCR (RT-PCR) analyses of the reb operon in stem nodules. Expression levels of the reb operon were normalized to 16S rRNA levels, expressed relative to corresponding data from the WT strain, and are presented as means ± standard deviations from three separate plants. Different letters indicate significant differences (P < 0.05, Tukey-Kramer). (C) Optical microscopic (OM) observations of infected host cells in stem nodules and transmission electron microscopic (TEM) observations of bacterial cells in host cells. Arrowheads indicate R bodies.