Histochemical localization of the expression of ERF12 in M. truncatula roots and nodules. A to H, M. truncatula roots transformed using ProERF12:GUS constructs and stained using X-Gluc. A and B, Uninoculated roots. C and D, Roots at 2 dpi. E to H, Nodules at different stages of development. I, Longitudinal 100-µm section of nodules at 2 to 3 weeks post inoculation. In H, S. medicae expressing a lacZ construct during early stages is stained in magenta. Bars = 100 µm (A–D and H) and 500 µm (E–G and I).