Abstract
Sodium (Na+) accumulation in the cytosol will result in ion homeostasis imbalance and toxicity of transpiring leaves. Studies of salinity tolerance in the diploid wheat ancestor Triticum monococcum showed that HKT1;5-like gene was a major gene in the QTL for salt tolerance, named Nax2. In the present study, we were interested in investigating the molecular mechanisms underpinning the role of the HKT1;5 gene in salt tolerance in barley (Hordeum vulgare). A USDA mini-core collection of 2,671 barley lines, part of a field trial was screened for salinity tolerance, and a Genome Wide Association Study (GWAS) was performed. Our results showed important SNPs that are correlated with salt tolerance that mapped to a region where HKT1;5 ion transporter located on chromosome four. Furthermore, sodium (Na+) and potassium (K+) content analysis revealed that tolerant lines accumulate more sodium in roots and leaf sheaths, than in the sensitive ones. In contrast, sodium concentration was reduced in leaf blades of the tolerant lines under salt stress. In the absence of NaCl, the concentration of Na+ and K+ were the same in the roots, leaf sheaths and leaf blades between the tolerant and the sensitive lines. In order to study the molecular mechanism behind that, alleles of the HKT1;5 gene from five tolerant and five sensitive barley lines were cloned and sequenced. Sequence analysis did not show the presence of any polymorphism that distinguishes between the tolerant and sensitive alleles. Our real-time RT-PCR experiments, showed that the expression of HKT1;5 gene in roots of the tolerant line was significantly induced after challenging the plants with salt stress. In contrast, in leaf sheaths the expression was decreased after salt treatment. In sensitive lines, there was no difference in the expression of HKT1;5 gene in leaf sheath under control and saline conditions, while a slight increase in the expression was observed in roots after salt treatment. These results provide stronger evidence that HKT1;5 gene in barley play a key role in withdrawing Na+ from the xylem and therefore reducing its transport to leaves. Given all that, these data support the hypothesis that HKT1;5 gene is responsible for Na+ unloading to the xylem and controlling its distribution in the shoots, which provide new insight into the understanding of this QTL for salinity tolerance in barley.
Highlights
The world’s land area affected by salinized soil and water is approximately 7%, and according to the FAO Land and Plant Nutrition Management service, most of the world’s land is not cultivated, but a significant proportion of irrigated land is saltaffected
Based on the field trial screening of the USDA barley core collection for salinity tolerance and ICP for the estimation of sodium and potassium content in the flag leaf, our results showed that the maintenance of K+ with exclusion of Na+ from the flag leaf was highly correlated with salt tolerance
The barley core collection tested in the field exhibited significant difference in salinity tolerance
Summary
The world’s land area affected by salinized soil and water is approximately 7%, and according to the FAO Land and Plant Nutrition Management service, most of the world’s land is not cultivated, but a significant proportion of irrigated land is saltaffected. There are two major mechanisms of salinity stress at the whole plant level that are advanced so far: a rapid and early osmotic stress which reduces shoot growth, and a slower accumulating ionic stress which accelerates senescence of older leaves (Sahi et al, 2006; Munns and Tester, 2008). Osmotic stress affects the plant’s water relations due to reduced availability of water from the soil solution (Munns, 2005), which in turn disturbs the growth of the plant by reducing cell expansion and elongation rates. This mechanism will lead to smaller and thicker leaves, reducing photosynthesis by stomatal closure, and limiting water uptake (Fricke et al, 2004). Adaptation to salinity stress is a quantitative character, which is controlled by different genetic pathways, where multiple genes are implicated in salinity tolerance (DeRose-Wilson and Gaut, 2011)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
