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Overexpression of Cucumber Phospholipase D alpha Gene ( CsPLD α ) in Tobacco Enhanced Salinity Stress Tolerance by Regulating Na + – K + Balance and Lipid Peroxidation

View Article: PubMed Central - PubMed

ABSTRACT

Plant phospholipase D (PLD), which can hydrolyze membrane phospholipids to produce phosphatidic acid (PA), a secondary signaling molecule, has been proposed to function in diverse plant stress responses. In this research, we characterized the roles of the cucumber phospholipase D alpha gene (PLDα, GenBank accession number EF363796) in growth and tolerance to short- and long-term salt stress in transgenic tobacco (Nicotiana tabacum). Fresh and dry weights of roots, PLD activity and content, mitogen activated protein kinase (MAPK) gene expression, Na+–K+ homeostasis, expression of genes encoding ion exchange, reactive oxygen species (ROS) metabolism and osmotic adjustment substances were investigated in wild type (WT) and CsPLDα-overexpression tobacco lines grown under short- and long-term high salt (250 mM) stress. Under short-term stress (5 h), in both overexpression lines, the PA content, and the expression levels of MAPK and several genes related to ion exchange (NtNHX1, NtNKT1, NtHAK1, NtNHA1, NtVAG1), were promoted by high PLD activity. Meanwhile, the Na+/K+ ratio decreased. Under long-term stress (16 days), ROS scavenging systems (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase activities) in leaves of transgenic lines were more active than those in WT plants. Meanwhile, the contents of proline, soluble sugar, and soluble protein significantly increased. In contrast, the contents of O2•− and H2O2, the electrolytic leakage and the accumulation of malondialdehyde in leaves significantly decreased. The root fresh and dry weights of the overexpression lines increased significantly. Na+–K+ homeostasis had the same trend as under the short-term treatment. These findings suggested that CsPLDα-produced PA can activate the downstream signals’ adaptive response to alleviate the damage of salt stress, and the main strategies for adaptation to salt stress are the accumulation of osmoprotective compounds, maintaining Na+–K+ homeostasis and the scavenging of ROS, which function in the osmotic balancing and structural stabilization of membranes.

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Related in: MedlinePlus

Effects of long-term NaCl stress on the activities of SOD(A), POD (B), CAT (C), and APX (D) in both WT and transgenic tobacco leaves. Values are means ± SD (n = 3). Different capital letters indicate significant difference (P < 0.01), and different small letters indicate significant difference (P < 0.05).
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Figure 10: Effects of long-term NaCl stress on the activities of SOD(A), POD (B), CAT (C), and APX (D) in both WT and transgenic tobacco leaves. Values are means ± SD (n = 3). Different capital letters indicate significant difference (P < 0.01), and different small letters indicate significant difference (P < 0.05).

Mentions: To evaluate the antioxidant defense system in plants exposed to salt stress, the activities of four well-recognized kinds of antioxidant enzymes, SOD, CAT, POD and APX, were measured in leaves of both WT and transgenic plants. There were opposing trends for H2O2 and O2•−. As shown in Figures 10A–D, antioxidant enzyme activities between WT and transgenic plants without a salt treatment showed no significant differences. Nevertheless, a NaCl treatment increased the enzyme activities in all of the plants, with the enzyme activities being higher in ‘T1-71’ and ‘T1-68’ than in WT plants. During the experimental period, SOD, POD, CAT, and APX activities peaked at 8 days, were maintained at high levels, and finally decreased at day 16, but their levels remained high compared with the CK. When compared with WT plants after 8 days of treatment, the SOD activities in leaves of ‘T1-68’ and ‘T1-71’ plants increased by 7.1 and 12.3%, respectively (P < 0.01; Figure 10A), and the POD activities increased by 41.9 and 45.9%, respectively (P < 0.05; Figure 10B). The CAT activities increased by 26.2 and 27.1%, respectively (P < 0.05; Figure 10C), and the APX activities increased by 32.7 and 40.0% (P < 0.01; Figure 10D), respectively. Thus, CsPLDα-overexpression in tobacco plants facilitated the growth and salt-stress tolerance of plants.


Overexpression of Cucumber Phospholipase D alpha Gene ( CsPLD α ) in Tobacco Enhanced Salinity Stress Tolerance by Regulating Na + – K + Balance and Lipid Peroxidation
Effects of long-term NaCl stress on the activities of SOD(A), POD (B), CAT (C), and APX (D) in both WT and transgenic tobacco leaves. Values are means ± SD (n = 3). Different capital letters indicate significant difference (P < 0.01), and different small letters indicate significant difference (P < 0.05).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5383712&req=5

Figure 10: Effects of long-term NaCl stress on the activities of SOD(A), POD (B), CAT (C), and APX (D) in both WT and transgenic tobacco leaves. Values are means ± SD (n = 3). Different capital letters indicate significant difference (P < 0.01), and different small letters indicate significant difference (P < 0.05).
Mentions: To evaluate the antioxidant defense system in plants exposed to salt stress, the activities of four well-recognized kinds of antioxidant enzymes, SOD, CAT, POD and APX, were measured in leaves of both WT and transgenic plants. There were opposing trends for H2O2 and O2•−. As shown in Figures 10A–D, antioxidant enzyme activities between WT and transgenic plants without a salt treatment showed no significant differences. Nevertheless, a NaCl treatment increased the enzyme activities in all of the plants, with the enzyme activities being higher in ‘T1-71’ and ‘T1-68’ than in WT plants. During the experimental period, SOD, POD, CAT, and APX activities peaked at 8 days, were maintained at high levels, and finally decreased at day 16, but their levels remained high compared with the CK. When compared with WT plants after 8 days of treatment, the SOD activities in leaves of ‘T1-68’ and ‘T1-71’ plants increased by 7.1 and 12.3%, respectively (P < 0.01; Figure 10A), and the POD activities increased by 41.9 and 45.9%, respectively (P < 0.05; Figure 10B). The CAT activities increased by 26.2 and 27.1%, respectively (P < 0.05; Figure 10C), and the APX activities increased by 32.7 and 40.0% (P < 0.01; Figure 10D), respectively. Thus, CsPLDα-overexpression in tobacco plants facilitated the growth and salt-stress tolerance of plants.

View Article: PubMed Central - PubMed

ABSTRACT

Plant phospholipase D (PLD), which can hydrolyze membrane phospholipids to produce phosphatidic acid (PA), a secondary signaling molecule, has been proposed to function in diverse plant stress responses. In this research, we characterized the roles of the cucumber phospholipase D alpha gene (PLD&alpha;, GenBank accession number EF363796) in growth and tolerance to short- and long-term salt stress in transgenic tobacco (Nicotiana tabacum). Fresh and dry weights of roots, PLD activity and content, mitogen activated protein kinase (MAPK) gene expression, Na+&ndash;K+ homeostasis, expression of genes encoding ion exchange, reactive oxygen species (ROS) metabolism and osmotic adjustment substances were investigated in wild type (WT) and CsPLD&alpha;-overexpression tobacco lines grown under short- and long-term high salt (250 mM) stress. Under short-term stress (5 h), in both overexpression lines, the PA content, and the expression levels of MAPK and several genes related to ion exchange (NtNHX1, NtNKT1, NtHAK1, NtNHA1, NtVAG1), were promoted by high PLD activity. Meanwhile, the Na+/K+ ratio decreased. Under long-term stress (16 days), ROS scavenging systems (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase activities) in leaves of transgenic lines were more active than those in WT plants. Meanwhile, the contents of proline, soluble sugar, and soluble protein significantly increased. In contrast, the contents of O2&bull;&minus; and H2O2, the electrolytic leakage and the accumulation of malondialdehyde in leaves significantly decreased. The root fresh and dry weights of the overexpression lines increased significantly. Na+&ndash;K+ homeostasis had the same trend as under the short-term treatment. These findings suggested that CsPLD&alpha;-produced PA can activate the downstream signals&rsquo; adaptive response to alleviate the damage of salt stress, and the main strategies for adaptation to salt stress are the accumulation of osmoprotective compounds, maintaining Na+&ndash;K+ homeostasis and the scavenging of ROS, which function in the osmotic balancing and structural stabilization of membranes.

No MeSH data available.


Related in: MedlinePlus