Background: Gene duplication events have been proposed to be involved in the adaptation of plants to stress conditions; precisely how is unclear. To address this question, we studied the evolution of two families of antiporters. Cation/proton exchangers are important for normal cell function and in plants, Na+,K+/H+ antiporters have also been implicated in salt tolerance. Two well-known plant cation/proton antiporters are NHX1 and SOS1, which perform Na+ and K+ compartmentalization into the vacuole and Na+ efflux from the cell, respectively. However, our knowledge about the evolution of NHX and SOS1 stress responsive gene families is still limited.Results: In this study we performed a comprehensive molecular evolutionary analysis of the NHX and SOS1 families. Using available sequences from a total of 33 plant species, we estimated gene family phylogenies and gene duplication histories, as well as examined heterogeneous selection pressure on amino acid sites. Our results show that, while the NHX family expanded and specialized, the SOS1 family remained a low copy gene family that appears to have undergone neofunctionalization during its evolutionary history. Additionally, we found that both families are under purifying selection although SOS1 is less constrained.Conclusions: We propose that the different evolution histories are related with the proteins' function and localization, and that the NHX and SOS1 families are examples of two different evolutionary paths through which duplication events may result in adaptive evolution of stress tolerance.
Bibliographical noteFunding Information:
We are grateful to Ulises Rosas (Purugganan Lab, NYU) for critical reading of the manuscript. We also thank funding by Fundação para a Ciência e a Tecnologia (FCT) – Portugal through National Funds (# PEst-OE/EQB/LA0004/ 2011), and in part by a grant from the NSF Plant Genome Research Program to MDP. ISP has a PhD fellowship grant (SFRH/BD/68835/2010) from FCT – Portugal. SN and IAA have postdoctoral fellowship grants (SFRH/BPD/34593/ 2007 and SFRH/BPD/78314/2011, respectively) also from FCT – Portugal.
ASJC Scopus subject areas
- Plant Science