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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 K content(A,B), Na content (C,D) and Na/K ratio (E,F) in both WT and transgenic tobacco leaves (A,C,E) and roots (B,D,F). 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 7: Effects of long-term NaCl stress on K content(A,B), Na content (C,D) and Na/K ratio (E,F) in both WT and transgenic tobacco leaves (A,C,E) and roots (B,D,F). 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: Under a long-time exposure to salts, Na+ concentrations in both the leaves and roots of WT and transgenic plants increased significantly (Figures 7C,D), while the K+ content decreased as shown in Figures 7A,B. Compared with WT plants, Na+ content after the 16-days treatment increased by more than 29.3% in leaves, but only 17.8% in roots, of ‘T1-71’ transgenic plants. Meanwhile, the K+ content increased by 57.7% in leaves and 40.6% in roots. Consequently, the Na+/K+ ratio increased in both the leaves and roots after 16 days of salt stress (Figures 7E,F). Unlike WT plants, both transgenic plants still maintained the highest levels of Na+ or K+ in their organisms, but the lowest Na+/K+ ratio after the 16-days salt stress, and the difference was more distinct in the ‘T1-71’ plants. Thus, the patterns of ion influx and efflux in all of the tobacco lines were consistent when the responses to salt stress. However, the overexpression of CsPLDα could protect against stress-induced changes in ion concentrations to maintain Na+–K+ homeostasis during a long-term treatment.


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 K content(A,B), Na content (C,D) and Na/K ratio (E,F) in both WT and transgenic tobacco leaves (A,C,E) and roots (B,D,F). 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

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

Figure 7: Effects of long-term NaCl stress on K content(A,B), Na content (C,D) and Na/K ratio (E,F) in both WT and transgenic tobacco leaves (A,C,E) and roots (B,D,F). 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: Under a long-time exposure to salts, Na+ concentrations in both the leaves and roots of WT and transgenic plants increased significantly (Figures 7C,D), while the K+ content decreased as shown in Figures 7A,B. Compared with WT plants, Na+ content after the 16-days treatment increased by more than 29.3% in leaves, but only 17.8% in roots, of ‘T1-71’ transgenic plants. Meanwhile, the K+ content increased by 57.7% in leaves and 40.6% in roots. Consequently, the Na+/K+ ratio increased in both the leaves and roots after 16 days of salt stress (Figures 7E,F). Unlike WT plants, both transgenic plants still maintained the highest levels of Na+ or K+ in their organisms, but the lowest Na+/K+ ratio after the 16-days salt stress, and the difference was more distinct in the ‘T1-71’ plants. Thus, the patterns of ion influx and efflux in all of the tobacco lines were consistent when the responses to salt stress. However, the overexpression of CsPLDα could protect against stress-induced changes in ion concentrations to maintain Na+–K+ homeostasis during a long-term treatment.

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