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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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Salinity stress inhibits PLD activity in rice leaves. Rice leaf cuts were pre-labeled O/N with 32Pi and then subjected to different concentration of NaCl (i.e. 0, 250, 500 and 1,000 mM) for 30 min, in the presence 0.5% (v/v) n-butanol as transphosphatidylation substrate for PLD (see Materials and Methods). Lipids were extracted and separated by ethyl acetate TLC. Radioactivity was quantified by phosphoimaging. Radioactivity levels of PBut (A) and PA (B) are shown.
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Figure 4: Salinity stress inhibits PLD activity in rice leaves. Rice leaf cuts were pre-labeled O/N with 32Pi and then subjected to different concentration of NaCl (i.e. 0, 250, 500 and 1,000 mM) for 30 min, in the presence 0.5% (v/v) n-butanol as transphosphatidylation substrate for PLD (see Materials and Methods). Lipids were extracted and separated by ethyl acetate TLC. Radioactivity was quantified by phosphoimaging. Radioactivity levels of PBut (A) and PA (B) are shown.

Mentions: Interestingly, and in contrast to what had been found before in Chlamydomonas (Munnik et al. 2000), Arabidopsis seedlings (Katagiri et al. 2001), tomato cell suspension cultures (Munnik et al. 2000) and Arabidopsis leaf discs (Bargmann et al. 2009b), salt did not activate PLD in rice leaves (Fig. 4). In contrast, salt was even found to inhibit PLD activity, as seen by the dose-dependent decrease in PBut formation (Fig. 4A) while PA levels clearly increased (Fig. 4 B).Fig. 4


Phospholipid signaling responses in salt-stressed rice leaves.

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

Salinity stress inhibits PLD activity in rice leaves. Rice leaf cuts were pre-labeled O/N with 32Pi and then subjected to different concentration of NaCl (i.e. 0, 250, 500 and 1,000 mM) for 30 min, in the presence 0.5% (v/v) n-butanol as transphosphatidylation substrate for PLD (see Materials and Methods). Lipids were extracted and separated by ethyl acetate TLC. Radioactivity was quantified by phosphoimaging. Radioactivity levels of PBut (A) and PA (B) are shown.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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

Figure 4: Salinity stress inhibits PLD activity in rice leaves. Rice leaf cuts were pre-labeled O/N with 32Pi and then subjected to different concentration of NaCl (i.e. 0, 250, 500 and 1,000 mM) for 30 min, in the presence 0.5% (v/v) n-butanol as transphosphatidylation substrate for PLD (see Materials and Methods). Lipids were extracted and separated by ethyl acetate TLC. Radioactivity was quantified by phosphoimaging. Radioactivity levels of PBut (A) and PA (B) are shown.
Mentions: Interestingly, and in contrast to what had been found before in Chlamydomonas (Munnik et al. 2000), Arabidopsis seedlings (Katagiri et al. 2001), tomato cell suspension cultures (Munnik et al. 2000) and Arabidopsis leaf discs (Bargmann et al. 2009b), salt did not activate PLD in rice leaves (Fig. 4). In contrast, salt was even found to inhibit PLD activity, as seen by the dose-dependent decrease in PBut formation (Fig. 4A) while PA levels clearly increased (Fig. 4 B).Fig. 4

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