Distinct patterns of natural selection in Na+/H+ antiporter genes in Populus euphratica and Populus pruinosa.

Yuxia Wu,Xiaohui Liang,Kuibin Meng

doi:10.1002/ece3.2639

Abstract

Salt tolerance genes constitute an important class of loci in plant genomes. Little is known about the extent to which natural selection in saline environments has acted upon these loci, and what types of nucleotide diversity such selection has given rise to. Here, we surveyed genetic diversity in three types of Na+/H+ antiporter gene (SOS, NhaD, and NHX, belonging to the cation/proton antiporter 1 family), which have well‐characterized essential roles in plant salt tolerance. Ten Na+/H+ antiporter genes and 16 neutral loci randomly selected as controls were sequenced from 17 accessions of two closely related members of the genus Populus, Populus euphratica and Populus pruinosa, section Turanga, which are native to northwest China. The results show that salt tolerance genes are common targets of natural selection in P. euphratica and P. pruinosa. Moreover, the patterns of nucleotide variation across the three types of Na+/H+ antiporter gene are distinctly different in these two closely related Populus species, and gene flow from P. pruinosa to P. euphratica is highly restricted. Our results suggest that natural selection played an important role in shaping the current distinct patterns of Na+/H+ antiporter genes, resulting in adaptive evolution in P. euphratica and P. pruinosa.

Highlights

The ability of an organism to undergo biological adaptation to the environment is a product of long-term evolution (Darwin, 1859)
We selected three types of Na+/H+ antiporter gene which were identified in previous studies as being affected by salt stress in P. euphratica (Hu & Wu, 2014; Ottow et al, 2005; Wu et al, 2007; Ye et al, 2009), and sequenced almost the complete gene coding regions for ten Na+/H+ antiporter genes in these three classes, and 16 neutral loci randomly selected as controls, in order to analyze nucleotide diversity in these two Populus species
Our results showed that salt tolerance genes have undergone greater divergence between the two species than the 16 reference loci, indicating that adaptive evolution of these genes has taken place in both P. euphratica and P. pruinosa

Summary

| INTRODUCTION

The ability of an organism to undergo biological adaptation to the environment is a product of long-term evolution (Darwin, 1859). Genes related to salt adaptation constitute an important group of loci It is still largely unknown whether differences in mutation rates across the genome, consistent with natural selection in response to environmental stresses, can account for the evolution of salt tolerance-related genes in plants. We selected three types of Na+/H+ antiporter gene which were identified in previous studies as being affected by salt stress in P. euphratica (Hu & Wu, 2014; Ottow et al, 2005; Wu et al, 2007; Ye et al, 2009), and sequenced almost the complete gene coding regions for ten Na+/H+ antiporter genes in these three classes, and 16 neutral loci randomly selected as controls, in order to analyze nucleotide diversity in these two Populus species

| MATERIALS AND METHODS

Findings

| DISCUSSION