Phylogenetic Analysis of NHX1 Gene in Different Species of Plants Based on Coding Sequences

The world population is anticipated to be about six billion by the end of the year 2050 which is very alarming (Najafi et al. 2019). On the other hand, food productivity is reducing due to various abiotic stresses; therefore, minimizing this situation is a major concern for all nations to cope with the increasing food requirements. Soil salinity is a serious environmental stress limiting plant productivity (Shrivastava et al. 2015). Sodium ions (Na+) abundant in saline soil, are cytotoxic in plants when they accumulate to high concentrations (Hasegawa et al. 2013). Over accumulation of Na+ in the cytosol causes protein synthesis inhibition, many enzymatic reactions, and photosynthetic processes (Yamaguchi et al. 2013). Therefore, it is crucial to exclude Na+ from photosynthetic organs for adequate metabolism and efficient carbon fixation. Until now, several classes of Na+ transporters have shown to play significant roles in Na+ homeostasis during salinity stress (Uozumi et al. 2010). The NHX transporter has drawn particular attention because of its capability to transport Na+ across cellular membranes. To date, most of NHX proteins studied facilitate electroneutral Na+/H+ and K+/H+ antiport through the membrane by using the H+ gradient as a driving force (Uozumi et al. 2010). These were observed to be responsible for Na+ reclusion into intracellular compartments under salinity stress. Overexpression of vacuolar NHX gene has conferred salt tolerance to a range of plant species such as wheat, rice, and tomato with a concomitant increase in tissue Na+ (Sahoo et al. 2016, Zhang et al. 2017). Moreover, the role of vacuolar NHXs in Na+ compartmentation under salinity stress is strongly supported by the findings of the Arabidopsis AtNHX1 mutant exhibited Na+ sensitivity and significantly less vacuolar Na+/H+ antiport activity (Apse et al. 2003). Besides an essential role in salt tolerance, pH regulation and organ developments have been demonstrated for vacuolar NHXs (Yamaguchi et al. 2001). Under normal conditions, the