Fig. 1.

Phenotype of nup133 mutants and genetic complementation. (A) Wild-type root nodules. (B) Ineffective nodule on nup133-1 inoculated with the M. loti TONO strain. (C) Root hair curling on a wild-type seedling inoculated with M. loti. (D) Root hair swelling on nup133-1 inoculated with M. loti. (E) Nodules on transgenic root showing complementation of nup133-2. (F) Section of mature wild-type root nodule. (G) Section of nup133-2 nodule. (H–J) Electron micrographs of an ineffective nodule showing infection threads (arrow) and M. loti bacteria within enlarged infection droplet structures (arrow). (K and L) Electron micrographs of a wild-type nodule showing a branched infection thread releasing an M. loti containing infection droplet (white arrow) and bacteroids (black arrow) surrounded by peribacteroid membrane (arrowhead). The symbiosome consists of bacteroids enclosed within a peribacteroid membrane. (Scale bars: 1 mm in A, B, and G and 50 μm in C–F and H.)