Comparative proteomic analysis of salt response proteins in seedling roots of two wheat varieties
Graphical abstract
Highlights
► One highly salt tolerant wheat cultivar and one salt sensitive wheat line were studied. ► Their seedling roots were used for a comparative proteome analysis for salt response. ► 114 DEPs were identified which fall into 4 functional categories.
Introduction
Soil salinity is a prevalent abiotic stress, which seriously impairs crop production on at least 20% of irrigated land worldwide [1]. Salinity stress leads to slow growth, wilting or even death of plants, especially in high salt concentrations. Ion toxicity, nutrient constraints, hyperosmotic stress and oxidative stress caused by salt stress may be the primary causes of severely disrupted protein synthesis and act by interfering with normal enzyme activity [2], [3]. Under salt stress, plants accumulate ion and reactive oxygen species (ROS) that are harmful to plant cells, especially under high salt concentrations [4]. These toxic by-products can decrease enzyme activity or even degrade some proteins. Due to genotypic difference and environmental conditions, plants have adaptive mechanisms to minimize salt injury, and different plants have developed different abilities to survive salt stress. In barley, S-adenosylmethionine (SAM) synthase and peroxidase involved in the detoxification of reactive oxygen species (ROS) were more abundant in salt-tolerant cultivar (cv) Steptoe than in salt-sensitive cv Morex, while proteins involved in iron uptake were expressed at a higher level in the sensitive cv Morex [5]. Salt-tolerant barley cultivars may have greater ability to sequester Na+ into sub-cellular compartments and/or maintain K+ homeostasis during salt stress [6]. Higher levels of vacuolar H+-ATPase might play a pivotal role in salinity tolerance of plant roots.
To date, a number of salt-responsive genes involved in membrane transport, signal transduction, redox reaction and other processes have been identified. Many stress-related genes such as AtNHX1, AVP1, AtSOS1 and AtSOS2 are required for Na+ sequestration and extrusion to maintain intracellular Na+/K+ homeostasis [7], [8], [9]. Such genes also include AgNHX1 and SKC1 in rice [10], and GhNHX1 in tobacco [11]. Some small molecular compatible solutes were synthesized by a series of genes closely related to abiotic stress responses. For example, the BADH gene in Suaeda liaotungensis kitag, which encodes betaine aldehyde dehydrogenase, the key enzyme of glycinebetaine synthesis, was introduced into maize to improve salt tolerance [12], [13], [14]. Sorbitol dehydrogenase encoded by the PmSDH1 gene over-accumulates mannitol to regulate salt stress in transgenic Plantago major plants [7]. Similarly, some transcriptional factors, such as OsNAC5 and JERF3 in rice and TaSTRG in wheat, can regulate stress responses and transgenic plants had improved tolerance to abiotic stresses such as salt, drought and cold [15], [16]. Despite these examples, salinity response remains a very complicated quantitative trait, causing many proteins to undergo removal of signal peptides, RNA splicing and post-translational modifications (PTMs) such as phosphorylation and glycosylation. This leads to poor correlations between transcriptomes and proteomes in different wheat cultivars under abiotic stresses [17], [18].
Recently, proteomic analysis has become one of the best strategies to reveal the dynamics of expression under salt stress. Comparative analysis of root proteomes between two durum wheat varieties with different tolerance levels to NaCl showed that the net synthesis of a 26 kDa polypeptide was significantly changed, being more evident in the more tolerant variety under 200 mM salt stress [19]. Wang et al. [20] identified 49 salt-responsive DEPs between seedling-roots of wheat cultivars Shanrong No. 3 and Jinan 177 under 200 mM salt treatments for 24 h. A wheat V-H+-ATPase E subunit protein was enhanced by salt stress, evidently more so in a wheat salt tolerant cultivar, under 137 mM salt stress [21]. However, proteomic studies on wheat roots at different levels of salt stress are rather limited; the few reports in this area were all focused on a very narrow range of salt concentrations [19], [20], [21]. Thus, comparisons of proteomic dynamics between salt-tolerant and salt-sensitive wheat varieties are yet to be studied, especially under a range of salt concentrations.
Wheat, the second major crop in the world, is a salt-sensitive glycophyte significantly affected by soil salinity. Since the root plays important roles in plant positioning, water absorption, and mineral uptake, it is also considered to be the primary site of salinity perception and the main organ responsible for tolerance to salt stress [2]. A comprehensive survey of the root proteome in response to salinity stress will help in understanding salt tolerance in wheat. Common wheat cv Chinese Spring (CS), which is widely used in experimental studies is sensitive to salt [22] and other stresses such as heat [23]. Chinese cv Jing-411, widely cultivated in the Beijing area in the 1990s, has characteristics of high yield, lodging resistance and abiotic stress tolerance. However, the protein dynamics of salt tolerance have not been investigated. In the present work, we undertook a comparative proteomic analysis of roots of wheat cv Jing-411 and Chinese Spring after exposure to a gradient of salinity conditions.
Section snippets
Plant materials and salt treatment
The experiments were carried out on common wheat varieties (Triticum aestivum L., 2n = 6x = 42, AABBDD), Jing-411 and Chinese Spring. Seeds were germinated on wet filter paper in the dark at room temperature. Uniformly pregerminated seeds were grown in 16 h light and 8 h dark at 23 °C–25 °C. Two-leaf seedlings were transferred to Hoagland's solution containing 5 mM KNO3, 2 mM MgSO4, 1 mM KH2PO4, 5 mM Ca(NO3)2, 50 μM FeNa2(EDTA)2, 50 μM H3BO3, 10 μM MnC12, 0.8 μM ZnSO4, 0.4 μM CuSO4, and 0.02 μM (NH4)6MoO24. The
Morphological and physiological changes under salt stress
In order to study short-term responses to salt stress, three-week-old wheat seedlings of the two wheat cultivars were treated for 2 days under a gradient of salt concentrations. CS wilted more than Jing-411 and exhibited obvious chlorosis, especially at the highest salt concentration. After salt treatment, the relative water content (RWC) and chlorophyll content in leaves were decreased more in CS than in Jing-411 (Fig. 1). The sodium contents in the roots differed significantly between CS and
Discussion
Our results demonstrated that, after treatment for 2 days under a gradient of salt concentrations, CS wilted more to a greater extent than Jing-411 and exhibited obvious chlorosis. Salt stress inhibits plant growth for two main reasons; it reduces the ability of the plant to take up water (osmotic stress) and it accumulates to excessive levels in the tissues resulting in cellular injury (ionic stress) [25], [26]. Under high salt concentrations, the regulatory functions of the plant appear to be
Summary
Salt tolerance is a complex phenomenon in most plant species, and involves numerous mechanisms, at the cellular, tissue, organ, and whole plant levels [62]. In the current study, a significant number of salt tolerance-related proteins were identified with various functions, including signal transduction related proteins, carbon, amino acid and nitrogen metabolism proteins, and detoxification and defense-associated proteins. These proteins should be useful in revealing insights into salt
Acknowledgments
We are grateful to Professor Robert McIntosh from University of Sydney for constructive suggestions in reviewing the manuscript. This research was financially supported by grants from the National Natural Science Foundation of China (30830072), the Chinese Ministry of Science and Technology (2009CB118300) and Key Project of National Plant Transgenic Genes of China (2008ZX08002-004, 2009ZX08002-017B).
References (62)
- et al.
Overexpression of TaSTRG gene improves salt and drought tolerance in rice
J Plant Physiol
(2009) - et al.
A proteomic study of the response to salinity and drought stress in an introgression strain of bread wheat
Mol Cell Proteomics
(2009) - et al.
Proteome analysis of wheat leaf under salt stress by two-dimensional difference gel electrophoresis (2D-DIGE). Proteomics Special Issues
Phytochemistry
(2011) - et al.
Cloning and characterization of a cDNA encoding 14-3-3 protein with leaf and stem-specific expression from wheat
DNA Seq
(2008) - et al.
Structural-functional state of thylakoid membranes of wheat genotypes under water stress
Biochim Biophys Acta
(2007) - et al.
Proteomic analysis of small heat shock protein isoforms in barley shoots
Phytochem
(2004) - et al.
Proteomics reveals elevated levels of PR10 proteins in saline-tolerant peanut (Arachis hypogaea) calli
Plant Physiol Biochem
(2006) - et al.
Translationally controlled tumor protein is a novel heat shock protein with chaperone-like activity
Biochem Biophys Res Commun
(2009) - et al.
Functional cloning of genes that suppress oxidative stress-induced cell death: TCTP prevents hydrogen peroxide-induced cell death
FEBS Lett
(2009) - et al.
Breeding for salinity resistance in crop plants: where next?
Aust J Plant Physiol
(1995)
Contractile roots are the most sensitive organ in Crocus sativus to salt stress
Biol Plant
Salt and drought stress signal transduction in plants
Ann Rev Plant Biol
Proteomic analysis of reactive oxygen species (ROS)-related proteins in rice roots
Plant Cell Rep
Salt stress-induced alterations in the root proteome of barley genotypes with contrasting response towards salinity
J Exp Bot
Insights into the salt tolerance mechanism in barley (Hordeum vulgare) from comparisons of cultivars that differ in salt sensitivity
J Plant Res
Salt tolerance conferred by overexpression of a vacuolar Na+/H+ antiport in Arabidopsis
Science
The Arabidopsis thaliana SOS2 gene encodes a protein kinase that is required for salt tolerance
Proc Natl Acad Sci USA
The Arabidopsis thaliana salt tolerance gene SOS1 encodes a putative Na+/H+ antiporter
Proc Natl Acad Sci USA
A rice quantitative trait locus for salt tolerance encodes a sodium transporter
Nat Genet
The cotton GhNHX1 gene encoding a novel putative tonoplast Na(+)/H(+) antiporter plays an important role in salt stress
Plant Cell Physiol
Improved tolerance to salinity and low temperature in transgenic tobacco producing glycine betaine
J Exp Bot
The Suaeda liaotungensis kitag betaine aldehyde dehydrogenase gene improves salt tolerance of transgenic maize mediated with minimum linear length of DNA fragment
Euphytica
Differential regulation of sorbitol and sucrose loading into the phloem of Plantago major in response to salt stress
Plant Physiol
The abiotic stress-responsive NAC-type transcription factor OsNAC5 regulates stress-inducible genes and stress tolerance in rice
Mol Genet Genomics
Modification-specific proteomics: characterization of post-translational modifications by mass spectrometry
Curr Opin Chem Biol
Analysis by two-dimensional electrophoresis of the effect of salt stress on the polypeptide patterns in roots of a salt-tolerant and a salt-sensitive cultivar of wheat
Electrophoresis
Proteomic analysis on a high salt tolerance introgression strain of Triticum aestivum/Thinopyrum ponticum
Proteomics
Cloning and functional analysis of wheat V-H+-ATPase subunit genes
Plant Mol Biol
Gene induction and repression by salt treatment in roots of the salinity-sensitive Chinese Spring wheat and the salinity-tolerant Chinese Spring x Elytrigia elongata amphiploid
Proc Natl Acad Sci USA
Heat stress-responsive transcriptome analysis in heat susceptible and tolerant wheat (Triticum aestivum L.) by using Wheat Genome Array
BMC Genomics
Rapid estimates of relative water content
Plant Physiol
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These authors contributed equally to this work.