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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 stimulates PA and PIP2 formation in a time- and dose-dependent manner. Rice leaf cuts were labeled O/N with 32Pi and then subjected to different concentrations of NaCl (0, 250, 500 and 1,000 mM) for different time periods (0, 15, 30, 45 and 60 min). The 60 min control sample was incubated for 60 min in buffer without salt. Lipids were extracted and subjected to alkaline TLC to separate the different phospholipid species. Radioactivity was visualized by autoradiography and quantified by phosphoimaging. (A) Autoradiograph of alkaline TLC showing lipids from leaf cuts of rice plants treated with 1 M NaCl for the times indicated. (B, C) Radioactivity levels of PA (B) and PIP2 (C) after NaCl treatment at the concentrations and for the times indicated.
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Figure 2: Salt stress stimulates PA and PIP2 formation in a time- and dose-dependent manner. Rice leaf cuts were labeled O/N with 32Pi and then subjected to different concentrations of NaCl (0, 250, 500 and 1,000 mM) for different time periods (0, 15, 30, 45 and 60 min). The 60 min control sample was incubated for 60 min in buffer without salt. Lipids were extracted and subjected to alkaline TLC to separate the different phospholipid species. Radioactivity was visualized by autoradiography and quantified by phosphoimaging. (A) Autoradiograph of alkaline TLC showing lipids from leaf cuts of rice plants treated with 1 M NaCl for the times indicated. (B, C) Radioactivity levels of PA (B) and PIP2 (C) after NaCl treatment at the concentrations and for the times indicated.

Mentions: The results of a typical experiment are presented in Fig. 2. Two main responses were observed: an increase in PA and PIP2. Responses were time-and dose dependent, with PA increases of up to 3.4-fold (Fig. 2B) and PIP2 increases of up to 4-fold (Fig. 2C), depending on the time and dose. In addition, two minor responses were picked up. DGPP levels increased whereas cardiolipin (CL), a minor structural phospholipid which is predominantly present in mitochondria, was found to decrease in response to salt stress (Fig. 2A).Fig. 2


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 stimulates PA and PIP2 formation in a time- and dose-dependent manner. Rice leaf cuts were labeled O/N with 32Pi and then subjected to different concentrations of NaCl (0, 250, 500 and 1,000 mM) for different time periods (0, 15, 30, 45 and 60 min). The 60 min control sample was incubated for 60 min in buffer without salt. Lipids were extracted and subjected to alkaline TLC to separate the different phospholipid species. Radioactivity was visualized by autoradiography and quantified by phosphoimaging. (A) Autoradiograph of alkaline TLC showing lipids from leaf cuts of rice plants treated with 1 M NaCl for the times indicated. (B, C) Radioactivity levels of PA (B) and PIP2 (C) after NaCl treatment at the concentrations and for the times indicated.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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

Figure 2: Salt stress stimulates PA and PIP2 formation in a time- and dose-dependent manner. Rice leaf cuts were labeled O/N with 32Pi and then subjected to different concentrations of NaCl (0, 250, 500 and 1,000 mM) for different time periods (0, 15, 30, 45 and 60 min). The 60 min control sample was incubated for 60 min in buffer without salt. Lipids were extracted and subjected to alkaline TLC to separate the different phospholipid species. Radioactivity was visualized by autoradiography and quantified by phosphoimaging. (A) Autoradiograph of alkaline TLC showing lipids from leaf cuts of rice plants treated with 1 M NaCl for the times indicated. (B, C) Radioactivity levels of PA (B) and PIP2 (C) after NaCl treatment at the concentrations and for the times indicated.
Mentions: The results of a typical experiment are presented in Fig. 2. Two main responses were observed: an increase in PA and PIP2. Responses were time-and dose dependent, with PA increases of up to 3.4-fold (Fig. 2B) and PIP2 increases of up to 4-fold (Fig. 2C), depending on the time and dose. In addition, two minor responses were picked up. DGPP levels increased whereas cardiolipin (CL), a minor structural phospholipid which is predominantly present in mitochondria, was found to decrease in response to salt stress (Fig. 2A).Fig. 2

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