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Effect of aspartic acid on physiological characteristics and gene expression of salt exclusion in Tartary buckwheat under salt stress

  • Jia-Song Zhang
  • Ya-Qi Wang
  • Jin-Nan Song
  • Jin-Peng Xu
  • Hong-Bing YangEmail author
Original Article
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Abstract

Salt-tolerant variety Chuanqiao No. 1 and salt-sensitive variety Chuanqiao No. 2 of Tartary buckwheat were used as experimental materials. The effect of aspartic acid on seed germination, physiological characteristics of seedlings and gene expression of salt exclusion in Tartary buckwheat were studied under NaCl stress of 150 mM. The results showed that the aspartic acid treatment could restore the seed germination rate and root vigor of seedlings to the control with non-damage level in salt-tolerant Tartary buckwheat variety under salt stress, and the salt-sensitive variety was increased greatly. Spraying aspartic acid had some protective effects on cell membrane of leaves in Tartary buckwheat under salt stress, and the protective effects were more obviously on salt-sensitive variety, and that could restore the activity of SOD and CAT of leaves to the control level in salt-tolerant Tartary buckwheat variety under salt stress, and the activity of antioxidant enzymes in salt-sensitive variety was increased significantly. The relative expression of FtNHX1 and FtSOS1 genes was increased significantly under salt stress, and that of FtNHX1 gene in salt-tolerant and salt-sensitive varieties was reached the maximum expression level at 12 h and 24 h respectively, while that of FtSOS1 gene in salt-tolerant and salt-sensitive varieties was reached the maximum expression level at 12 h, and the salt-tolerant variety was increased greatly. After spraying aspartic acid, the relative expression of FtNHX1 and FtSOS1 genes was increased more obviously. The relative expression of FtNHX1 gene in salt-tolerant and salt-sensitive varieties was reached the maximum expression level at 12 h, while that of FtSOS1 gene was reached the maximum expression level at 12 h and 24 h respectively, and that in salt-tolerant variety was increased especially more, indicating that spraying aspartic acid on gene expression of salt exclusion in salt-tolerant variety of Tartary buckwheat has a better effect under salt stress.

Keywords

Tartary buckwheat Salt stress Aspartic acid Physiological characteristics Gene expression of salt exclusion 

Abbreviations

CAT

Catalase

MDA

Malondialdehyde

POD

Peroxidase

SOD

Superoxide dismutase

TTC

Triphenyltetrazolium chloride

Introduction

In recent years, crop growth and yield have been greatly affected by the increasing area of salinization and secondary salinization in China (Chen et al. 2007), and salinization has become one of the main factors affecting the sustainable development of agriculture and ecological environment. Buckwheat has a long history of food use in China, which was introduced into Japan from the Tang Dynasty. Buckwheat is an excellent health care saint in Japan, it has great market value and prospect (Hu et al. 2008). Therefore, it is of great value and economic significance to study the salt tolerance of buckwheat, which can expand the planting area and increase the yield of buckwheat.

Studies showed that salt stress affected seed germination, seedling root vigor, plasmalemma permeability of leaves and other physiological characteristics (Han et al. 2014). The Na+ was uptaken from the roots and reached the shoot with transpiration and accumulated in the leaves, which resulted in leaf necrosis and affected photosynthesis, thereby reducing crop yield (Cai et al. 2015). The salt tolerance of crops was the worst at the stage of seed germination and seedlings, followed by the stage of reproductive growth, while the sensitivity to salt stress was relatively low at the other developmental stages of crops (Gong et al. 1994). The Na+/H+ antiporter (SOS1 or NHX1) plays an important role in maintaining a suitable concentration of Na+ in the cytoplasm and reducing Na+ toxicity. The NHX1 is located in vacuolar membrane, which can compartmentalize excessive Na+ in cytoplasm and accumulate in the vacuole, and the SOS1 is located in plasmalemma, which can extrude excessive Na+ from the cytoplasm (Blumwald et al. 2000; Shi et al. 2002).

The amino acids are important components of cell proteins in plants, and also important osmotic regulators in cytoplasm, which can enhance the water retention capacity of cells (Yang 2014a). Recent studies have shown that amino acids, as biological stimulants, can also improve physiological characteristics, significantly improve salt tolerance, and alleviate the inhibition of salt stress on growth and development in plants (Xu et al. 2018). Under high temperature stress, proper concentration of glutamic acid and aspartic acid had important protective effect on structure and function of plasmalemma in buckwheat leaves, and the effect of aspartic acid was better than that of glutamic acid (Liu and Yang 2015). At present, there are few studies on improvement of crop physiological characteristics by aspartic acid under salt stress. In this study, the seed germination rate, root vigor of seedlings, plasmalemma permeability, MDA content, activity of antioxidant enzyme and gene expression of FtNHX1 and FtSOS1 were measured to study the effect of aspartic acid on physiological characteristics and gene expression of salt exclusion in Tartary buckwheat under salt stress, which would provide a theoretical basis for the study on mechanism of exogenous substances improving the salt tolerance in crops and the effective utilization of salinized soil resources.

Materials and methods

Salt-tolerant variety Chuanqiao No. 1 and salt-sensitive variety Chuanqiao No. 2 of Tartary buckwheat were used as experimental materials (Liu et al. 2015). Based the effect of salt stress on seed germination and seedling growth of Tartary buckwheat (Yang and Yang 2014), we chose 150 mM as the concentration of NaCl for treatment. The physiological characteristics of buckwheat seedlings under high temperature stress were significantly improved by aspartic acid treatment of 20 µM (Yang 2014b; Liu and Yang 2015), while aspartic acid treatment of 40 µM could significantly promote the growth of buckwheat seedlings under salt stress and improve the salt tolerance of buckwheat (Ji et al. 2014; Yang 2014a), so we chose 40 µM as the concentration of aspartic acid for treatment under salt stress.

Determination of seed germination rate

The same size and full grain seeds of Tartary buckwheat were selected, soaked in 1 g/L KMnO4 for 10 min, washed in proper amount of aseptic water for 5 min, imbibed in distilled water for 5 h. The seeds were evenly placed in a dish with filter paper, cultured in incubator at 26 °C. The control (CK) group was treated with clean water, and the salt stress (NaCl) group was treated with NaCl of 150 mM, and that in salt stress + aspartic acid (NaCl + Asp) group was that containing 40 µM aspartic acid in NaCl solution. 121 Tartary buckwheat seeds in each group were counted at the same time every day, and continuously counted for 5 days to calculate the germination rate.

Germination rate (Gr) = n/N × 100% (n: germination number; N: total number of seeds). Setting 3 replicates each treatment.

Cultivation and treatment of seedling materials

The seedlings of Tartary buckwheat were cultivated with Hoagland nutrient solution, natural light and conventional management. Buckwheat seedlings were treated with NaCl of 150 mM in roots at the stage of 2 leaves and 1 center leaf, and NaCl + Asp group was sprayed with aspartic acid of 40 µM on the basis of salt stress in roots, and the physiological indexes were determined after 2 days later. 5 buckwheat seedlings in each group were treated with 3 replicates per treatment.

Determination of root vigor of seedlings

Using TTC method (Liu and Liu 2010) to determine the root vigor of seedlings.

Determination of plasmalemma permeability and MDA content of leaves

The plasmalemma permeability and MDA content of leaves were determined by the method of Li et al. (1983).

Determination of antioxidant enzyme activity of leaves

The SOD activity of leaves was determined by the method of Zou (2000), and the POD and CAT activity of leaves was determined by the method of He et al. (1997).

Determination of gene expression

Plant RNA extraction kit of Takara was used to add liquid nitrogen to grind the sample. During the extraction process, the extract was placed in ice to reduce the temperature to prevent RNA degradation. The RNA concentration was determined by spectrophotometry, and the cDNA was obtained by RT-PCR using Prime ScriptTM RT reagent Kit with gDNA ERASER reverse transcription kit (Takara). The primers used in this experiment are FtNHX1-F, FtNHX1-R, FtSOS1-F and FtSOS1-R. Primer sequences are shown in Table S1.

Reverse transcription was carried out in two steps: first, a 10 µL reaction system was constructed (Table S2). The PCR procedure: 42 °C, 3 min; 4 °C, ∞.

The 20 µL reaction system was constructed by 10 µL system of step 1 (Table S3). The PCR procedure: 42 °C, 15 min; 85 °C, 1 min; 4 °C, ∞.

The cDNA obtained by reverse transcription should be quickly inserted on ice to prevent degradation. Adding 40 µL RNase-free H2O to make the system up to 60 µL for the analysis of fluorescence quantitative PCR. Real-time fluorescence quantitative PCR primers of Actin-F and Actin-R were used to perform real-time fluorescence quantitative PCR on Agilent Technologies Strata gene MX3000P with the reference of SYBR Premix EX Taq II kit (Vazyme). Setting 3 replicates each treatment.

Results

Effect of aspartic acid on seed germination rate in Tartary buckwheat under salt stress

Salt tolerance of seeds is the early stage for salt tolerance identification in plants and important basis for early selection of salt-tolerant varieties (Li et al. 2005). Table 1 showed that the seed germination rate of Chuanqiao Nos. 1 and 2 was decreased significantly under salt stress, which was decreased by 15.01% and 45.23% respectively compared with the control, and that of Chuanqiao No. 2 was decreased by a large extent. After the treatment with exogenous aspartic acid, the seed germination rate of Chuanqiao Nos. 1 and 2 was increased significantly, which was increased by 11.12% and 24.92% respectively compared with the salt stress, and that of Chuanqiao No. 2 was increased by a large extent, and that of Chuanqiao No. 1 was restored to the control level.
Table 1

Effects of aspartic acid on seed germination rate (%) in Tartary buckwheat under salt stress

Varieties

CK (control)

NaCl (150 mM)

NaCl + Asp (40 µM)

Chuanqiao No. l

93.27 ± 6.18a

78.26 ± 4.83b

89.38 ± 5.51a

Chuanqiao No. 2

92.65 ± 5.79a

47.42 ± 3.65c

72.34 ± 4.76b

Values followed by different letters are significantly different at the 0.05 probability level. The same as below

Effect of aspartic acid on root vigor of seedlings in Tartary buckwheat under salt stress

Root system is an important interface between plant and environment, it will produce corresponding physiological response after receiving stress signal, which will affect the growth and development of shoot (Wan and Song 1995). The root vigor can reflect the stress resistance of the species to a certain extent (Gao et al. 2010). Table 2 showed that the root vigor of seedlings in Chuanqiao Nos. 1 and 2 was decreased significantly under salt stress, which was decreased by 32.79% and 59.95% respectively compared with the control, and that in Chuanqiao No. 2 was decreased by a large extent. After the treatment with exogenous aspartic acid, the root vigor of seedlings in Chuanqiao Nos. 1 and 2 was increased significantly, which was increased by 39.56% and 90.83% respectively compared with the salt stress, and that in Chuanqiao No. 2 was increased greatly, and that in Chuanqiao No. 1 was restored to the control level.
Table 2

Effects of aspartic acid on root vigor (U/g) of seedlings in Tartary buckwheat under salt stress

Varieties

CK (control)

NaCl (150 mM)

NaCl + Asp (40 µM)

Chuanqiao No. l

112.35 ± 7.06a

75.51 ± 4.87b

105.38 ± 6.46a

Chuanqiao No. 2

106.47 ± 6.49a

42.64 ± 3.23c

81.37 ± 5.31b

Effect of aspartic acid on plasmalemma permeability of leaves in Tartary buckwheat under salt stress

Under normal growth conditions, the plasmalemma permeability of plants was lower, while that was increased under stress environment (Li et al. 2009). Xiao et al. (2000) showed that the plasmalemma permeability could reflect the integrity of membrane system and the degree of damage, and the greater the plasmalemma permeability under salt stress, the greater degree of damage in plants. Table 3 showed that the plasmalemma permeability of leaves in Chuanqiao Nos. 1 and 2 was increased significantly under salt stress, which was increased by 97.56% and 223.90% respectively compared with the control, and that in Chuanqiao No. 2 was increased by a large margin. After the treatment with exogenous aspartic acid, the plasmalemma permeability of leaves in Chuanqiao Nos. 1 and 2 was decreased significantly, which was decreased by 27.17% and 34.53% respectively compared with the salt stress, and that in Chuanqiao No. 2 was decreased greatly.
Table 3

Effects of aspartic acid on plasmalemma permeability (%) of leaves in Tartary buckwheat under salt stress

Varieties

CK (control)

NaCl (150 mM)

NaCl + Asp (40 µM)

Chuanqiao No. l

22.15 ± 1.86d

43.76 ± 2.65b

31.87 ± 2.08c

Chuanqiao No. 2

19.83 ± 1.74d

64.23 ± 3.97a

42.05 ± 2.81b

Effect of aspartic acid on MDA content of leaves in Tartary buckwheat under salt stress

MDA is the product of membrane lipid peroxidation (Tian et al. 2009); the content of MDA can reflect the degree of membrane lipid peroxidation and the stress response to some extent in plants (Cao et al. 2005). Table 4 showed that the MDA content of leaves in Chuanqiao Nos. 1 and 2 was increased significantly under salt stress, which was increased by 158.97% and 299.08% respectively, and that in Chuanqiao No. 2 was increased by a large margin. After the treatment with exogenous aspartic acid, the MDA content of leaves in Chuanqiao Nos. 1 and 2 was decreased significantly, which was decreased by 32.67% and 39.93% respectively compared with the salt stress, and that in Chuanqiao No. 2 was decreased greatly.
Table 4

Effects of aspartic acid on MDA content (µmol/g) of leaves in Tartary buckwheat under salt stress

Varieties

CK (control)

NaCl (150 mM)

NaCl + Asp (40 µM)

Chuanqiao No. l

26.03 ± 2.02e

67.41 ± 4.20b

45.39 ± 2.73d

Chuanqiao No. 2

23.87 ± 1.89e

95.26 ± 5.81a

57.22 ± 3.86c

Effect of aspartic acid on SOD activity of leaves in Tartary buckwheat under salt stress

SOD is an important antioxidant enzyme in organisms, and it is involved in almost all the physiological processes of stress resistance in organisms (Dou et al. 2000). Table 5 showed that the SOD activity of leaves in Chuanqiao Nos. 1 and 2 was decreased significantly under salt stress, which was decreased by 30.58% and 55.05% respectively compared with the control, and that in Chuanqiao No. 2 was decreased by a large extent. After the treatment with exogenous aspartic acid, the SOD activity of leaves in Chuanqiao Nos. 1 and 2 was increased significantly, which was increased by 42.80% and 69.59% respectively compared with the salt stress, and that in Chuanqiao No. 2 was increased greatly, and that in Chuanqiao No. 1 was restored to the control level.
Table 5

Effects of aspartic acid on SOD activity (U/g) of leaves in Tartary buckwheat under salt stress

Varieties

CK (control)

NaCl (150 mM)

NaCl + Asp (40 µM)

Chuanqiao No. l

147.52 ± 8.29a

102.41 ± 6.63b

146.24 ± 8.45a

Chuanqiao No. 2

151.36 ± 8.87a

68.03 ± 4.72c

115.37 ± 7.08b

Effect of aspartic acid on POD activity of leaves in Tartary buckwheat under salt stress

POD consumes H2O2 by catalyzing H2O2 to react with other substrates, so as to reduce the damage of H2O2 in plants (Liu and Jia 2009). Table 6 showed that the POD activity of leaves in Chuanqiao Nos. 1 and 2 was decreased significantly under salt stress, which was decreased by 40.33% and 51.58% respectively compared with the control, and that in Chuanqiao No. 2 was decreased by a large extent. After the treatment with exogenous aspartic acid, the POD activity of leaves in Chuanqiao No. 1 and Chuanqiao No. 2 was increased significantly, which was increased by 40.22% and 54.77% respectively compared with the salt stress, and that in Chuanqiao No. 2 was increased greatly.
Table 6

Effects of aspartic acid on POD activity (U g−1 min−1) of leaves in Tartary buckwheat under salt stress

Varieties

CK (control)

NaCl (150 mM)

NaCl + Asp (40 µM)

Chuanqiao No. l

97.64 ± 7.26a

58.26 ± 4.15d

81.69 ± 5.27b

Chuanqiao No. 2

93.82 ± 5.43a

45.43 ± 3.62e

70.31 ± 4.96c

Effect of aspartic acid on CAT activity of leaves in Tartary buckwheat under salt stress

CAT can quench H2O2 and decompose H2O2 into H2O and O2 directly, and the changes of CAT activity play an important role in the balance of oxidation and antioxidation in plants (Li and Du 2001; Wei et al. 2006). Table 7 showed that the CAT activity of leaves in Chuanqiao Nos. 1 and 2 was decreased significantly under salt stress, which was decreased by 23.82% and 52.63% respectively compared with the control, and that in Chuanqiao No. 2 was decreased by a large extent. After the treatment with exogenous aspartic acid, the CAT activity of leaves in Chuanqiao No. 1 and Chuanqiao No. 2 was increased significantly, which was increased by 32.37% and 56.48% respectively compared with the salt stress, and that in Chuanqiao No. 2 was increased greatly, and that in Chuanqiao No. 1 was restored to the control level.
Table 7

Effects of aspartic acid on CAT activity (U g−1 min−1) of leaves in Tartary buckwheat under salt stress

Varieties

CK (control)

NaCl (150 mM)

NaCl + Asp (40 µM)

Chuanqiao No. l

23.97 ± 2.02a

18.26 ± 1.65b

24.17 ± 1.98a

Chuanqiao No. 2

26.05 ± 2.21a

12.34 ± 1.03c

19.31 ± 1.76b

Effect of aspartic acid on relative expression of FtNHX1 gene of leaves in Tartary buckwheat under salt stress

Much Na+ in cytoplasm can be transported to vacuole for compartmentalization by Na+/H+ antiport in vacuolar membrane to reduce Na+ toxicity (Reguera et al. 2014). Figure 1 showed that the relative expression of FtNHX1 gene of leaves in Chuanqiao Nos. 1 and 2 was increased significantly under salt stress, and that in Chuanqiao No. 1 was increased by 152.81%, 472.67%, 286.18% and 57.41% respectively at 6, 12, 24 and 48 h compared with the control, and that was reached the maximum level at 12 h, and that in Chuanqiao No. 2 was increased by 64.16%, 123.77%, 211.45% and 47.65% respectively compared with the control, and that was reached the maximum level at 24 h, and that in Chuanqiao No. 1 was increased more than that in Chuanqiao No. 2. After the treatment with exogenous aspartic acid, the relative expression of FtNHX1 gene of leaves in Chuanqiao Nos. 1 and 2 was increased more obviously, and that in Chuanqiao No. 1 was increased by 621.35%, 886.41%, 708.16% and 532.37% respectively compared with the salt stress, while that in Chuanqiao No. 2 was increased by 412.74%, 724.58%, 512.49% and 310.57% respectively compared with the salt stress. Both Chuanqiao Nos. 1 and 2 were reached the maximum level at 12 h, and that in Chuanqiao No. 1 was increased greatly, suggesting that the Na+ compartmentalization capacity of vacuole in Chuanqiao No. 1 is obviously higher than that in Chuanqiao No. 2.
Fig. 1

Effects of aspartic acid on relative expression of FtNHX1 gene of leaves in Tartary buckwheat under salt stress

Effect of aspartic acid on relative expression of FtSOS1 gene of leaves in Tartary buckwheat under salt stress

Na+/H+ antiport in plasmalemma could pump Na+ outside the cell to improve the salt tolerance in plants (Apse and Blumwald 2007). Figure 2 showed that the relative expression of FtSOS1 gene of leaves in Chuanqiao Nos. 1 and 2 was increased significantly under salt stress, and that in Chuanqiao No. 1 was increased by 315.63%, 763.51%, 538.42% and 423.15% respectively at 6, 12, 24 and 48 h compared with the control, and that in Chuanqiao No. 2 was increased by 181.48%, 349.06%, 246.17% and 156.77% respectively compared with the control, and both were reached the maximum level at 12 h, and that in Chuanqiao No. 1 was increased more than that in Chuanqiao No. 2. After the treatment with exogenous aspartic acid, the relative expression of FtSOS1 gene of leaves in Chuanqiao Nos. 1 and 2 was increased more obviously, and that in Chuanqiao No. 1 was increased by 831.32%, 1461.38%, 1202.17% and 1026.52% respectively compared with the salt stress, and that was reached the maximum level at 12 h, while that in Chuanqiao No. 2 was increased by 348.49%, 624.87%, 899.85% and 571.76% respectively compared with the salt stress, and that was reached the maximum level at 24 h. Compared with Chuanqiao No. 2, the relative expression of FtSOS1 gene in Chuanqiao No. 1 was increased particularly, suggesting that the Na+ extrusion capacity of plasmalemma in Chuanqiao No. 1 is obviously higher than that in Chuanqiao No. 2.
Fig. 2

Effects of aspartic acid on relative expression of FtSOS1 gene of leaves in Tartary buckwheat under salt stress

Discussion

Germination rate and root vigor were important indexes for identification of salt tolerance in wheat varieties (Meng et al. 2015). Liu et al. (2015) found that the seed germination rate and root vigor of seedlings in Tartary buckwheat were reduced under NaCl stress of 100 mM. The changes of seed germination rate and root vigor of seedlings in Chuanqiao Nos. 1 and 2 under NaCl stress of 150 mM were studied in this paper, and found that the seed germination rate and root vigor of seedlings in two kinds of Tartary buckwheat varieties were decreased significantly, while that in salt-sensitive variety were decreased greatly. After the treatment with exogenous aspartic acid, the seed germination rate and root vigor of seedlings in two kinds of Tartary buckwheat varieties were increased significantly, while that in salt-sensitive variety were increased greatly, and that in salt-tolerant variety were restored to the control with non-damage level.

Cell membrane is an interface between cell and environment, and also the primary and main site of damage in plants under stress. Maintaining the stability of cell membrane is an important salt-tolerant mechanism in crops. Stress could destroy the integrity of membrane and leak soluble substances (Hou et al. 2012), under normal conditions, the plasmalemma permeability of leaf cells is very small, while under stress environment, that increased obviously (Cao et al. 2005). In this paper, under salt stress, the plasmalemma permeability of leaves in two kinds of Tartary buckwheat varieties increased significantly, while that in salt-sensitive variety increased significantly. After the treatment with exogenous aspartic acid, that in salt-sensitive variety decreased more, indicating that the aspartic acid had a better effect on protecting the integrity of plasma membrane in salt-sensitive one.

Malondialdehyde (MDA) is the end product of membrane lipid peroxidation. When MDA binds to protein, cross-linking occurs between protein molecules. Especially, the cross-linking polymerization of structural protein and enzyme protein are more harmful to plasma membrane. Therefore, the MDA content could reflect the damage degree of cell membrane in tissue (Liu et al. 2009). In this paper, MDA content of leaves in salt-sensitive variety was increased more than that in salt-tolerant one, indicating that the degree of membrane lipid peroxidation of leaves in salt-sensitive variety was higher. After the treatment with exogenous aspartic acid, that in two kinds of Tartary buckwheat varieties was decreased significantly, and that in salt-sensitive variety was decreased more, indicating that spraying aspartic acid had some protective effects on cell membrane of leaves in Tartary buckwheat under salt stress, and especially obvious on salt-sensitive variety.

Improving the activity of antioxidant enzymes and accumulating osmotic regulators are two important mechanisms for plant survival under stress environment. The reactive oxygen radicals produced by plants under stress environment have strong oxidative capacity, which can destroy the structure and function of many functional molecules in cells. Therefore, the scavenging of reactive oxygen species is very important for keeping the cell membrane in good condition (Tian et al. 2005). Studies have shown that SOD, POD and CAT are important protective enzymes for ROS scavenging and play an important role in preventing membrane lipid peroxidation, delaying senescence and maintaining normal growth and development in plants. Under moderate stress-induced conditions, the activity of SOD, POD and CAT will increase to improve the stress resistance in plants (Wang et al. 2011). In this paper, the activity of SOD, POD and CAT of leaves in two kinds of Tartary buckwheat varieties was decreased significantly under salt stress, and that in salt-sensitive variety was decreased more obviously. After treated with exogenous aspartic acid, that in two kinds of Tartary buckwheat varieties was increased significantly, and the activity of SOD and CAT of leaves in salt-tolerant variety was restored to the control level.

Most dicotyledons adapt to salinity in three ways, including Na+ excretion of plasmalemma, Na+ compartmentalization of vacuole and Na+ uptake rejection. The first two ways are accomplished by Na+/H+ antiport in plasmalemma and vacuolar respectively (Peng and Wang 2005). Meng (2010) found that MzNHX1 is a Na+/H+ antiport gene in vacuolar membrane, which is related to salt tolerance in Malus zumi, while SOS1 is a Na+/H+ antiport gene in plasma membrane, which can transport Na+ out of cells and is the first barrier to salt exclusion in plants (Yang et al. 2016). In this paper, the relative expression of FtNHX1 and FtSOS1 genes in two kinds of Tartary buckwheat varieties was increased significantly under salt stress, indicating that the expression of FtNHX1 and FtSOS1 genes was positively regulated by salt, and that in salt-tolerant variety was increased more than that in salt-sensitive one, indicating that the expression of FtNHX1 and FtSOS1 genes was positively correlated with the salt tolerance of Tartary buckwheat. After the treatment with exogenous aspartic acid, the relative expression of FtNHX1 and FtSOS1 genes was increased significantly, especially in salt-tolerant variety, indicating that the effect of spraying aspartic acid on gene expression of salt exclusion in salt-tolerant variety of Tartary buckwheat was better than that in salt-sensitive one under salt stress.

Conclusion

  1. (1)

    Aspartic acid treatment could restore the seed germination rate and root vigor of seedlings to the control with non-damage level in salt-tolerant variety under salt stress.

     
  2. (2)

    The protective effect of spraying aspartic acid on cell membrane of leaves in salt-sensitive variety was more obviously than that in salt-tolerant one.

     
  3. (3)

    Spraying aspartic acid could restore the activity of SOD and CAT of leaves to the control level in salt-tolerant variety under salt stress.

     
  4. (4)

    The effect of spraying aspartic acid on gene expression of salt exclusion in salt-tolerant variety was better than that in salt-sensitive one under salt stress.

     

Notes

Acknowledgements

We would like to acknowledge the financial supports from the National Natural Science Foundation of China (31371552), and the research materials Chuanqiao Nos. 1 and 2 were furnished by Research Station of Alpine Crop, Department of Agriculture and Science in Liangshan State, Sichuan Province, China.

Authors’ contribution

J-SZ analyzed the physiological characteristics of Tartary buckwheat and wrote the manuscript. Y-QW analyzed the gene express of FtNHX1 by doing real-time PCR. J-NS analyzed the gene express of FeSOS1 by doing real-time PCR. J-PX cultivated the plant and treated. The corresponding author H-BY designed the experiment and revised the manuscript.

Compliance with ethical standards

Conflict of interest

There is no conflict exists among all the authors, and the contribution of the authors is clear and unquestionable. All of them declare that they have no conflict of interest. Therefore, all authors are allowed to publish the article.

Supplementary material

13562_2019_518_MOESM1_ESM.docx (34 kb)
Supplementary material 1 (DOCX 33 kb)
13562_2019_518_MOESM2_ESM.docx (34 kb)
Supplementary material 2 (DOCX 34 kb)
13562_2019_518_MOESM3_ESM.docx (34 kb)
Supplementary material 3 (DOCX 34 kb)

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Copyright information

© Society for Plant Biochemistry and Biotechnology 2019

Authors and Affiliations

  1. 1.Key Lab of Plant Biotechnology in Universities of Shandong Province, College of Life SciencesQingdao Agricultural UniversityQingdaoChina

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