Salt stress reveals differential physiological, biochemical and molecular responses in T. monococcum and T. durum wheat genotypes

Abstract

Salt stress responses implicate a complex mechanism and differ from plant species to another. In this study, we analyzed the physiological, biochemical and molecular responses to salt stress of the diploid wheat (T. monococcum) and compared to the tetraploid wheat (T. durum). Our results showed that the diploid wheat cultivar (cv. Turkey) is relatively tolerant to different salt stress conditions than the tetraploid wheat cultivar (cv. Om Rabia3). This tolerance was manifested by significant germination, plant growth and uptake of water generating cell turgor and development. Moreover, total chlorophyll content was higher in the diploid wheat than that in the tetraploid wheat. The Na⁺ content in leaf blade of the cv. Om Rabia3 was significantly higher than that of the cv. Turkey, suggesting that the diploid cultivar accumulates less toxic sodium in the photosynthetic tissues. This mechanism could be explained by the recirculation of the toxic ions Na⁺ into the xylem sap by SOS1 protein, which coordinates with HKT-like proteins to reduce the accumulation of Na⁺ ions in leaf blade. Interestingly, the expression of the three genes SOS1, HKT and NHX was enhanced under salinity especially in leaf blade of the cv. Turkey. Moreover, this wheat cultivar induced the antioxidative enzymes CAT and SOD activity more efficiently than the other cultivar.

Keywords: Antioxidant enzyme; Diploid wheat; Salt stress; Sodium transport; Tetraploid wheat.

Fig. 1

Seeds germination percentage of the diploid wheat T. monococcum (cv. Turkey) and the tetraploid wheat T. durum (cv. Om Rabia3) under different salt concentrations (0, 50, 100 and 200 mM NaCl). Values represent mean ± SE of four replicates. Asterisks indicate a statistically significant difference (P < 0.05)

Fig. 2

a Effect of salt stress treatment on plant growth of two different wheat genotypes, the cv. Turkey and the cv. Om Rabia3. Determination of the dry weight (DW) of the different organ of these two wheat cultivars, b total leaf area (TLA), c and root length, d under low (50 mM), medium (100 mM) and high (200 mM) salt stress treatment during 3 days. Values represent mean ± SE of six replicates. Asterisks indicate a statistically significant difference (P < 0.05)

Fig. 3

a Relative water content (RWC) of leaf blade of the two wheat cultivars (cv. Turkey and the cv. Om Rabia3) under different salt concentrations (0, 50, 100 and 200 mM NaCl) during 3 days, and under exposition with 100 mM NaCl during 2, 4 and 8 days, b determination of the water content of the different organ of these wheat cultivars under salt stress treatment, c and under exposition to medium salt stress (100 mM) during 2, 4 and 8 days, d values represent mean ± SE of four replicates. Asterisks indicate a statistically significant difference (P < 0.05)

Fig. 4

Determination of the total chlorophyll content of the two wheat cultivars (cv. Turkey and the cv. Om Rabia3) under different salt concentrations (0, 50, 100 and 200 mM NaCl) and during 3 days. Values represent mean ± SE of three replicates. Asterisks indicate a statistically significant difference (P < 0.05)

Fig. 5

Na⁺ and K⁺ content of the different organs of two wheat cultivars treated with different salt concentration (0, 50, 100 and 200 mM NaCl) during 3 days, and exposed to medium salt stress (100 mM) during 2, 4 and 8 days. Na⁺ (a, b) and K⁺ (c, d) contents calculated as mg of ions per g of dry weight (DW) of the tissue. Sodium and potassium contents were determined in the roots, the leaf sheath and the leaf blade. Values represent mean ± SE of three replicates. Asterisks indicate a statistically significant difference (P < 0.05)

Fig. 6

Real-time RT-PCR analysis of SOS, a NHX, b and HKT1;4, C expression in different tissues (roots, leaf sheath and leaf blade) of the two wheat cultivars (cv. Turkey and the cv. Om Rabia3). Relative expression level was measured under normal condition or under 50 mM NaCl treatment for 4 and 48 h. Data in (a–c) are mean ± SE of three biological replicates. Asterisks indicate a statistically significant difference (P < 0.05)

Fig. 7

Effect of salt stress treatment (50 mM NaCl) on H₂O₂ content in roots, leaf sheath and leaf blade of the two wheat cultivars (cv. Turkey and cv. Om Rabia3) during 4 and 48 h. Values represent mean ± SE of four replicates. Asterisks indicate a statistically significant difference (P < 0.05)

Fig. 8

CAT and SOD activities, a and quantitative expression, b analysis in leaf blade of the two different wheat genotypes (cv. Turkey and the cv. Om Rabia3) exposed or low salt stress treatment (50 mM NaCl) and control during 4 and 48 h. Values represent mean ± SE of three replicates. Asterisks indicate a statistically significant difference (P < 0.05)