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Phospholipid signaling responses in salt-stressed rice leaves.

Darwish E, Testerink C, Khalil M, El-Shihy O, Munnik T - Plant Cell Physiol. (2009)

Bottom Line: Only very small amounts of PIP2 were found.Comparison of the 32P-lipid responses in salt-tolerant and salt-sensitive cultivars revealed no significant differences.Together these results show that salt stress rapidly activates several lipid responses in rice leaves but that these responses do not explain the difference in salt tolerance between sensitive and tolerant cultivars.

View Article: PubMed Central - PubMed

Affiliation: Section of Plant Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.

ABSTRACT
Salinity is one of the major environmental factors limiting growth and productivity of rice plants. In this study, the effect of salt stress on phospholipid signaling responses in rice leaves was investigated. Leaf cuts were radiolabeled with 32P-orthophosphate and the lipids extracted and analyzed by thin-layer chromatography, autoradiography and phosphoimaging. Phospholipids were identified by co-migration of known standards. Results showed that 32P(i) was rapidly incorporated into the minor lipids, phosphatidylinositol bisphosphate (PIP2) and phosphatidic acid (PA) and, interestingly, also into the structural lipids phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), which normally label relatively slowly, like phosphatidylcholine (PC) and phosphatidylinositol (PI). Only very small amounts of PIP2 were found. However, in response to salt stress (NaCl), PIP2 levels rapidly (<30 min) increased up to 4-fold, in a time- and dose-dependent manner. PA and its phosphorylated product, diacylglycerolpyrophosphate (DGPP), also increased upon NaCl stress, while cardiolipin (CL) levels decreased. All other phospholipid levels remained unchanged. PA signaling can be generated via the combined action of phospholipase C (PLC) and diacylglycerol kinase (DGK) or directly via phospholipase D (PLD). The latter can be measured in vivo, using a transphosphatidylation assay. Interestingly, these measurements revealed that salt stress inhibited PLD activity, indicating that the salt stress-induced PA response was not due to PLD activity. Comparison of the 32P-lipid responses in salt-tolerant and salt-sensitive cultivars revealed no significant differences. Together these results show that salt stress rapidly activates several lipid responses in rice leaves but that these responses do not explain the difference in salt tolerance between sensitive and tolerant cultivars.

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Related in: MedlinePlus

Salt stress activates PLD activity after prolonged incubation. Leaf cuts of rice were pre-labeled O/N with 32Pi and then subjected to 500 mM NaCl for 0, 4, 8 or 24 h. In this case, 0.5% (v/v) n-butanol was added 30 min prior to the end of the treatment. Lipids were then extracted, separated by ethyl acetate TLC and quantified by phosphoimaging. Radioactivity levels of PBut (A) and PA (B) are shown. Control (open bars); NaCl (filled bars).
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Figure 5: Salt stress activates PLD activity after prolonged incubation. Leaf cuts of rice were pre-labeled O/N with 32Pi and then subjected to 500 mM NaCl for 0, 4, 8 or 24 h. In this case, 0.5% (v/v) n-butanol was added 30 min prior to the end of the treatment. Lipids were then extracted, separated by ethyl acetate TLC and quantified by phosphoimaging. Radioactivity levels of PBut (A) and PA (B) are shown. Control (open bars); NaCl (filled bars).

Mentions: To study the activity of PLD under longer salt stress conditions, pre-labeled leaf cuts were incubated with 500 mM NaCl for 4, 8 or 24 h. n-Butanol [0.5% (v/v)] was only added for the last 30 min of the incubation. As shown in Fig. 5, increased PBut levels were found after 8 h (1.8-fold increase), and, after 24 h, PLD activity was still 1.3-fold higher than in the control situation without salt. These results indicate that the fast increase of PA within the first half hour is not a consequence of PLD activation, but that PLD is activated at later time points (hours vs. minutes). In tobacco pollen tubes, PLD was also found to be inhibited by salt stress in the minute range (Zonia and Munnik 2004).Fig. 5


Phospholipid signaling responses in salt-stressed rice leaves.

Darwish E, Testerink C, Khalil M, El-Shihy O, Munnik T - Plant Cell Physiol. (2009)

Salt stress activates PLD activity after prolonged incubation. Leaf cuts of rice were pre-labeled O/N with 32Pi and then subjected to 500 mM NaCl for 0, 4, 8 or 24 h. In this case, 0.5% (v/v) n-butanol was added 30 min prior to the end of the treatment. Lipids were then extracted, separated by ethyl acetate TLC and quantified by phosphoimaging. Radioactivity levels of PBut (A) and PA (B) are shown. Control (open bars); NaCl (filled bars).
© Copyright Policy - openaccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2682722&req=5

Figure 5: Salt stress activates PLD activity after prolonged incubation. Leaf cuts of rice were pre-labeled O/N with 32Pi and then subjected to 500 mM NaCl for 0, 4, 8 or 24 h. In this case, 0.5% (v/v) n-butanol was added 30 min prior to the end of the treatment. Lipids were then extracted, separated by ethyl acetate TLC and quantified by phosphoimaging. Radioactivity levels of PBut (A) and PA (B) are shown. Control (open bars); NaCl (filled bars).
Mentions: To study the activity of PLD under longer salt stress conditions, pre-labeled leaf cuts were incubated with 500 mM NaCl for 4, 8 or 24 h. n-Butanol [0.5% (v/v)] was only added for the last 30 min of the incubation. As shown in Fig. 5, increased PBut levels were found after 8 h (1.8-fold increase), and, after 24 h, PLD activity was still 1.3-fold higher than in the control situation without salt. These results indicate that the fast increase of PA within the first half hour is not a consequence of PLD activation, but that PLD is activated at later time points (hours vs. minutes). In tobacco pollen tubes, PLD was also found to be inhibited by salt stress in the minute range (Zonia and Munnik 2004).Fig. 5

Bottom Line: Only very small amounts of PIP2 were found.Comparison of the 32P-lipid responses in salt-tolerant and salt-sensitive cultivars revealed no significant differences.Together these results show that salt stress rapidly activates several lipid responses in rice leaves but that these responses do not explain the difference in salt tolerance between sensitive and tolerant cultivars.

View Article: PubMed Central - PubMed

Affiliation: Section of Plant Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.

ABSTRACT
Salinity is one of the major environmental factors limiting growth and productivity of rice plants. In this study, the effect of salt stress on phospholipid signaling responses in rice leaves was investigated. Leaf cuts were radiolabeled with 32P-orthophosphate and the lipids extracted and analyzed by thin-layer chromatography, autoradiography and phosphoimaging. Phospholipids were identified by co-migration of known standards. Results showed that 32P(i) was rapidly incorporated into the minor lipids, phosphatidylinositol bisphosphate (PIP2) and phosphatidic acid (PA) and, interestingly, also into the structural lipids phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), which normally label relatively slowly, like phosphatidylcholine (PC) and phosphatidylinositol (PI). Only very small amounts of PIP2 were found. However, in response to salt stress (NaCl), PIP2 levels rapidly (<30 min) increased up to 4-fold, in a time- and dose-dependent manner. PA and its phosphorylated product, diacylglycerolpyrophosphate (DGPP), also increased upon NaCl stress, while cardiolipin (CL) levels decreased. All other phospholipid levels remained unchanged. PA signaling can be generated via the combined action of phospholipase C (PLC) and diacylglycerol kinase (DGK) or directly via phospholipase D (PLD). The latter can be measured in vivo, using a transphosphatidylation assay. Interestingly, these measurements revealed that salt stress inhibited PLD activity, indicating that the salt stress-induced PA response was not due to PLD activity. Comparison of the 32P-lipid responses in salt-tolerant and salt-sensitive cultivars revealed no significant differences. Together these results show that salt stress rapidly activates several lipid responses in rice leaves but that these responses do not explain the difference in salt tolerance between sensitive and tolerant cultivars.

Show MeSH
Related in: MedlinePlus