Abstract
The cation/proton antiporter superfamily is associated with the transport of monovalent cations across membranes.
This superfamily was annotated in the Arabidopsis genome and some members were functionally characterized.
In the present study, a systematic analysis of the cation/proton antiporter genes in diverse plant
specieswas reported.We identified 240 cation/proton antiporters in alga, moss, and angiosperm. A phylogenetic
tree was constructed showing these 240members are separated into three families, i.e., Na+/H+ exchangers, K+
efflux antiporters, and cation/H+ exchangers. Our analysis revealed that tandem and/or segmental duplications
contribute to the expansion of cation/H+ exchangers in the examined angiospermspecies. Sliding windowanalysis
of the nonsynonymous/synonymous substitution ratios showed some differences in the evolutionary fate of
cation/proton antiporter paralogs. Furthermore, we identified over-represented motifs among these 240 proteins
and foundmostmotifs are family specific, demonstrating diverse evolution of the cation/proton antiporters
among three families. In addition, we investigated the co-expressed genes of the cation/proton antiporters in
Arabidopsis thaliana. The results showed some biological processes are enriched in the co-expressed genes,
suggesting the cation/proton antiporters may be involved in these biological processes. Taken together, this
study furthers our knowledge on cation/proton antiporters in plants.
