Western blot analysis of OsBOR1 protein in response to different B concentrations in rice roots. A and B, Western blot analysis of OsBOR1 (A) and H⁺-ATPase (B) in response to different B concentrations. Red arrow shows the size of OsBOR1. C and D, Signal intensity of OsBOR1 (C) and H⁺-ATPase (D). Seedlings (21-d-old) were exposed to 0, 0.3, 3, 30 µM B for 7 d. Roots were harvested for western blot analysis with three biological replicates. The microsome fraction was analyzed by SDS–PAGE and visualized by western blot with antibodies against OsBOR1 and H⁺-ATPase (as an internal standard). Signal intensity of target band was quantified by Image Lab Software (Bio-Rad, Hercules, CA, USA) and the intensity relative to −B is shown. Data are means ± sd (n = 3). Left lane shows molecular weight markers. Different lowercase letters indicate the significant difference at P < 0.01 by Tukey–Kramer’s test.