Phylogenetic relationships within cation transporter families of Arabidopsis

Uptake and translocation of cationic nutrients play essential roles in phys iological processes including plant growth, nutrition, signal transduction, and development. Approximately 5% of the Arabidopsis genome appears to enc ode membrane transport proteins. These proteins are classified in 46 unique families containing approximately 880 members. In addition, several hundre d putative transporters have not yet been assigned to families. In this pap er, we have analyzed the phylogenetic relationships of over 150 cation tran sport proteins. This analysis has focused on cation transporter gene famili es for which initial characterizations have been achieved for individual me mbers, including potassium transporters and channels, sodium transporters, calcium antiporters, cyclic nucleotide-gated channels, cation diffusion fac ilitator proteins, natural resistance-associated macrophage proteins (NRAMP ), and Zn-regulated transporter Fe-regulated transporter-like proteins. Phy logenetic trees of each family define the evolutionary relationships of the members to each other. These families contain numerous members, indicating diverse functions in vivo. Closely related isoforms and separate subfamili es exist within many of these gene families, indicating possible redundanci es arid specialized functions. To facilitate their further study, the Plant sT database (http://plantst.sdsc.edu) has been created that includes alignm ents of the analyzed cation transporters and their chromosomal locations.