Molecular Evolution Of Na~+/H~+ Antiporter Gene Family In Genus Populus

Populus species are identified as a deciduous tree with important economic and ecological value distributing in the Northern Hemisphere. The sequence determination of whole genome of various Populus species has laid a foundation for studying the mechanism of different Populus species adapting to different environmental conditions by comparing the variation of the key allelic.In this study, 64 pairs of specific primers were designed according to the sequence of Populus trichocarpa genome reference and were used to amplify Populus Na~+/H~+ antiporter gene family. The sequencing data was artificially aligned using CodonCode Aligner software. We carried out calculation though PAML software to check purpose gene structure variation and the adaptive evolution between different populous species. The DNA polymorphism were analyzed and the genetic diversity of each haplotype was calculated by DnaSP, MEGA and ARLEQUIN software, and through the software of HKA and MKPRF, the data were calculated and the neutral test was carried out to reveal the molecular evolution mechanism of Na~+/H~+ gene family. The results showed that: positive selection was detected in the calculations of NHX5 gene in Sect. Populus and NHX6、SOS1 in Sect. Turanga Bge; the Na~+/H~+ antiporter gene family in both P. euphratica and P. pruinosa generally experienced adaptive evolution. Meanwhile, the research found that SOS1 gene possessed a gene duplication phenomenon in P. euphratica(Sect. Turanga Bge). And the duplicate genes were named PeSOS1 b, which could markedly recover the sensitivity of the deficient E.coli EP432 without EcNhaA and EcNhaB genes to the high salt environment through functional complementation experiments indicating that PeSOS1 b gene still had the function of anti-salt the existence of salt PeSOS1 b gene function, yet carried out pseudogenization.The Na~+/H~+ antiporter gene family existed different patterns of molecular evolutionary among different Populus species, which could play an important role on studying the evolutionary styles of genes and revealing natural selection mechanism of related functional gene.