Phylogenetic tree of NRAMP3 homologues in Populus and Salix species. Arabidopsis thaliana NRAMP2 (AT1G47240.1), NRAMP3 (AT2G23150.1), NRAMP4 (AT5G67330.1), and NRAMP5 (AT4G18790 .1) as well as P. trichocarpa NRAMP2 (Potri002G121000.1) and S. purpurea NRAMP2 (Sapur.002G098200.1) are shown as an outgroup. The other protein sequences used for this tree are listed in supplementary data S3, Supplementary Material online. “$” indicates incomplete protein sequences. Phylogenetic analyses were conducted as described in Materials and methods.