NHX-Type Na+/H+ Antiporter Gene Expression Under Different Salt Levels and Allelic Diversity of HvNHX in Wild and Cultivated Barleys.

Zahra Jabeen,Guoping Zhang,Faiza Irshad,Yong Han,Nazim Hussain

doi:10.3389/fgene.2021.809988

Zahra Jabeen, Guoping Zhang + Show 3 more

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https://doi.org/10.3389/fgene.2021.809988

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Abstract

Salinity tolerance is a multifaceted trait attributed to various mechanisms. Wild barley is highly specialized to grow under severe environmental conditions of Tibet and is well-known for its diverse germplasm with high tolerance to abiotic stresses. The present study focused on determining the profile of the expression of isoforms of the HvNHX gene in 36 wild and two cultivated barley under salt stress. Our findings revealed that in leaves and roots, expression of HvNHX1 and HvNHX3 in XZ16 and CM72 was upregulated at all times as compared with sensitive ones. The HvNHX2 and HvNHX4 isoforms were also induced by salt stress, although not to the same extent as HvNHX1 and HvNHX3. Gene expression analysis revealed that HvNHX1 and HvNHX3 are the candidate genes that could have the function of regulators of ions by sequestration of Na+ in the vacuole. HvNHX1 and HvNHX3 showed a wide range of sequence variations in an amplicon, identified via single-nucleotide polymorphisms (SNPs). Evaluation of the sequencing data of 38 barley genotypes, including Tibetan wild and cultivated varieties, showed polymorphisms, including SNPs, and small insertion and deletion (INDEL) sites in the targeted genes HvNHX1 and HvNHX3. Comprehensive analysis of the results revealed that Tibetan wild barley has distinctive alleles of HvNHX1 and HvNHX3 which confer tolerance to salinity. Furthermore, less sodium accumulation was observed in the root of XZ16 than the other genotypes as visualized by CoroNa-Green, a sodium-specific fluorophore. XZ16 is the tolerant genotype, showing least reduction of root and leaf dry weight under moderate (150 mM) and severe (300 mM) NaCl stress. Evaluation of genetic variation and identification of salt tolerance mechanism in wild barley could be promoting approaches to unravel the novel alleles involved in salinity tolerance.

Highlights

Na+/H+, counter-transporters (NHXs) serve as essential membrane transporters and help catalyze the neutral exchange of K+ or Na+ for H+ and have been found to play a significant role in pH and ion homeostasis, cell expansion, and salt tolerance
We studied the influence of salt stress on HvNHX1, HvNHX2, HvNHX3, and HvNHX4 gene expression in roots and leaves of four barley genotypes after 0, 6, 12, and 24 h of exposure to moderate and severe salt stress
Na+ first enters the cytosol of a plant and disturbs important physiological, biochemical, and molecular processes; it restricts plant growth, disruption of ion homeostasis (Mane et al, 2010; Basu et al, 2020), and development, posing a serious threat to crop production (Zhu, 2007)

Summary

Introduction

Na+/H+, counter-transporters (NHXs) serve as essential membrane transporters and help catalyze the neutral exchange of K+ or Na+ for H+ and have been found to play a significant role in pH and ion homeostasis, cell expansion, and salt tolerance. To develop crops with enhanced tolerance to abiotic stresses, the establishment of a better understanding of the underlying mechanisms is essential. Soil salinization causes severe reduction in barley production all around the world (Rengasamy et al, 2003; Mishra and Tanna 2017). In such a scenario, to go for soil amendments is near to impossible. Understanding salt-tolerant mechanisms is essential for the genetic improvement of crops. Having unique features among cereal crops, barley is widely used in physiological and genetic studies to unravel the mechanisms of salt tolerance (Munns and Mark, 2008). Tibetan wild barley (H. spontaneum L.), which habited the Qinghai–Tibet Plateau of China years ago, is one of the ancestors of cultivated barley (Dai et al, 2012)

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