Symbiotic phenotype of M. truncatula wild type (WT), nramp1-1, and nramp1-1 transformed with MtNramp1 regulated under its endogenous promoter (NR1p). A, Growth of representative plants. Bar = 1 cm. B, Close view of representative nodules of each M. truncatula line. Bar = 1 mm. C, Fresh weight of shoots and roots. Data are the mean ± se (n = 6–8 plants). D, Nodule number per plant; 100% = 5.67 nodules/plant. Data are the average ± se (n = 7 plants). E, Nitrogenase activity in 28-dpi nodules. Acetylene reduction was measured in duplicate from two sets of five pooled plants. Data are the mean ± se; 100% = 42.83 nmol ethylene h–1 g–1. F, Iron content (μg g−1) in 28-dpi plants. Bars indicate the average ± se of two sets of five transformed plants. Asterisk indicates significant differences (P ≤ 0.05).