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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

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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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Effects of long-term NaCl stress on phospholipase D activity in both WT and transgenic tobacco leaves. Values are means ± SD (n = 3). Mean values followed by different capital letters (A–C) and small letters (a–c) are significantly different (P < 0.01) and (P < 0.05), respectively.
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Figure 6: Effects of long-term NaCl stress on phospholipase D activity in both WT and transgenic tobacco leaves. Values are means ± SD (n = 3). Mean values followed by different capital letters (A–C) and small letters (a–c) are significantly different (P < 0.01) and (P < 0.05), respectively.

Mentions: Figure 6 shows that the PLD activity levels were not significantly different between WT and transgenic plants before treatment (CK). However, the PLD activities in transgenic plants were induced to a greater degree than that in the WT under high NaCl conditions. The PLD activities in leaves of ‘T1-68’ and ‘T1-71’ transgenic plants were significantly higher by 15.3 and 29.3%, respectively, than that in WT after 8 days of the 250 mM NaCl treatment. In addition, the high salt treatment slightly enhanced the PLD activities in WT and transgenic plants as the treatment time increased. Thus, PLD may be positively induced by salt stress and CsPLDα-overexpression may have sensitized plant responses to the long-term salt stress.


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 phospholipase D activity in both WT and transgenic tobacco leaves. Values are means ± SD (n = 3). Mean values followed by different capital letters (A–C) and small letters (a–c) are significantly different (P < 0.01) and (P < 0.05), respectively.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 6: Effects of long-term NaCl stress on phospholipase D activity in both WT and transgenic tobacco leaves. Values are means ± SD (n = 3). Mean values followed by different capital letters (A–C) and small letters (a–c) are significantly different (P < 0.01) and (P < 0.05), respectively.
Mentions: Figure 6 shows that the PLD activity levels were not significantly different between WT and transgenic plants before treatment (CK). However, the PLD activities in transgenic plants were induced to a greater degree than that in the WT under high NaCl conditions. The PLD activities in leaves of ‘T1-68’ and ‘T1-71’ transgenic plants were significantly higher by 15.3 and 29.3%, respectively, than that in WT after 8 days of the 250 mM NaCl treatment. In addition, the high salt treatment slightly enhanced the PLD activities in WT and transgenic plants as the treatment time increased. Thus, PLD may be positively induced by salt stress and CsPLDα-overexpression may have sensitized plant responses to the long-term salt stress.

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